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Maciej W. Rozycki 3e29f34a4e MIPS: Keep the ISA bit in compressed code addresses 
1. Background information

The MIPS architecture, as originally designed and implemented in
mid-1980s has a uniform instruction word size that is 4 bytes, naturally
aligned.  As such all MIPS instructions are located at addresses that
have their bits #1 and #0 set to zeroes, and any attempt to execute an
instruction from an address that has any of the two bits set to one
causes an address error exception.  This may for example happen when a
jump-register instruction is executed whose register value used as the
jump target has any of these bits set.

Then in mid 1990s LSI sought a way to improve code density for their
TinyRISC family of MIPS cores and invented an alternatively encoded
instruction set in a joint effort with MIPS Technologies (then a
subsidiary of SGI).  The new instruction set has been named the MIPS16
ASE (Application-Specific Extension) and uses a variable instruction
word size, which is 2 bytes (as the name of the ASE suggests) for most,
but there are a couple of exceptions that take 4 bytes, and then most of
the 2-byte instructions can be treated with a 2-byte extension prefix to
expand the range of the immediate operands used.

As a result instructions are no longer 4-byte aligned, instead they are
aligned to a multiple of 2.  That left the bit #0 still unused for code
references, be it for the standard MIPS (i.e. as originally invented) or
for the MIPS16 instruction set, and based on that observation a clever
trick was invented that on one hand allowed the processor to be
seamlessly switched between the two instruction sets at any time at the
run time while on the other avoided the introduction of any special
control register to do that.

So it is the bit #0 of the instruction address that was chosen as the
selector and named the ISA bit.  Any instruction executed at an even
address is interpreted as a standard MIPS instruction (the address still
has to have its bit #1 clear), any instruction executed at an odd
address is interpreted as a MIPS16 instruction.

To switch between modes ordinary jump instructions are used, such as
used for function calls and returns, specifically the bit #0 of the
source register used in jump-register instructions selects the execution
(ISA) mode for the following piece of code to be interpreted in.
Additionally new jump-immediate instructions were added that flipped the
ISA bit to select the opposite mode upon execution.  They were
considered necessary to avoid the need to make register jumps in all
cases as the original jump-immediate instructions provided no way to
change the bit #0 at all.

This was all important for cases where standard MIPS and MIPS16 code had
to be mixed, either for compatibility with the existing binary code base
or to access resources not reachable from MIPS16 code (the MIPS16
instruction set only provides access to general-purpose registers, and
not for example floating-point unit registers or privileged coprocessor
0 registers) -- pieces of code in the opposite mode can be executed as
ordinary subroutine calls.

A similar approach has been more recently adopted for the MIPS16
replacement instruction set defined as the so called microMIPS ASE.
This is another instruction set encoding introduced to the MIPS
architecture.  Just like the MIPS16 ASE, the microMIPS instruction set
uses a variable-length encoding, where each instruction takes a multiple
of 2 bytes.  The ISA bit has been reused and for microMIPS-capable
processors selects between the standard MIPS and the microMIPS mode
instead.

2. Statement of the problem

To put it shortly, MIPS16 and microMIPS code pointers used by GDB are
different to these observed at the run time.  This results in the same
expressions being evaluated producing different results in GDB and in
the program being debugged.  Obviously it's the results obtained at the
run time that are correct (they define how the program behaves) and
therefore by definition the results obtained in GDB are incorrect.

A bit longer description will record that obviously at the run time the
ISA bit has to be set correctly (refer to background information above
if unsure why so) or the program will not run as expected.  This is
recorded in all the executable file structures used at the run time: the
dynamic symbol table (but not always the static one!), the GOT, and
obviously in all the addresses embedded in code or data of the program
itself, calculated by applying the appropriate relocations at the static
link time.

While a program is being processed by GDB, the ISA bit is stripped off
from any code addresses, presumably to make them the same as the
respective raw memory byte address used by the processor to access the
instruction in the instruction fetch access cycle.  This stripping is
actually performed outside GDB proper, in BFD, specifically
_bfd_mips_elf_symbol_processing (elfxx-mips.c, see the piece of code at
the very bottom of that function, starting with an: "If this is an
odd-valued function symbol, assume it's a MIPS16 or microMIPS one."
comment).

This function is also responsible for symbol table dumps made by
`objdump' too, so you'll never see the ISA bit reported there by that
tool, you need to use `readelf'.

This is however unlike what is ever done at the run time, the ISA bit
once present is never stripped off, for example a cast like this:

(short *) main

will not strip the ISA bit off and if the resulting pointer is intended
to be used to access instructions as data, for example for software
instruction decoding (like for fault recovery or emulation in a signal
handler) or for self-modifying code then the bit still has to be
stripped off by an explicit AND operation.

This is probably best illustrated with a simple real program example.
Let's consider the following simple program:

$ cat foobar.c
int __attribute__ ((mips16)) foo (void)
{
  return 1;
}

int __attribute__ ((mips16)) bar (void)
{
  return 2;
}

int __attribute__ ((nomips16)) foo32 (void)
{
  return 3;
}

int (*foo32p) (void) = foo32;
int (*foop) (void) = foo;
int fooi = (int) foo;

int
main (void)
{
  return foop ();
}
$

This is plain C with no odd tricks, except from the instruction mode
attributes.  They are not necessary to trigger this problem, I just put
them here so that the program can be contained in a single source file
and to make it obvious which function is MIPS16 code and which is not.

Let's try it with Linux, so that everyone can repeat this experiment:

$ mips-linux-gnu-gcc -mips16 -g -O2 -o foobar foobar.c
$

Let's have a look at some interesting symbols:

$ mips-linux-gnu-readelf -s foobar | egrep 'table|foo|bar'
Symbol table '.dynsym' contains 7 entries:
Symbol table '.symtab' contains 95 entries:
    55: 00000000     0 FILE    LOCAL  DEFAULT  ABS foobar.c
    66: 0040068c     4 FUNC    GLOBAL DEFAULT [MIPS16]    12 bar
    68: 00410848     4 OBJECT  GLOBAL DEFAULT   21 foo32p
    70: 00410844     4 OBJECT  GLOBAL DEFAULT   21 foop
    78: 00400684     8 FUNC    GLOBAL DEFAULT   12 foo32
    80: 00400680     4 FUNC    GLOBAL DEFAULT [MIPS16]    12 foo
    88: 00410840     4 OBJECT  GLOBAL DEFAULT   21 fooi
$

Hmm, no sight of the ISA bit, but notice how foo and bar (but not
foo32!) have been marked as MIPS16 functions (ELF symbol structure's
`st_other' field is used for that).

So let's try to run and poke at this program with GDB.  I'll be using a
native system for simplicity (I'll be using ellipses here and there to
remove unrelated clutter):

$ ./foobar
$ echo $?
1
$

So far, so good.

$ gdb ./foobar
[...]
(gdb) break main
Breakpoint 1 at 0x400490: file foobar.c, line 23.
(gdb) run
Starting program: .../foobar

Breakpoint 1, main () at foobar.c:23
23        return foop ();
(gdb)

Yay, it worked!  OK, so let's poke at it:

(gdb) print main
$1 = {int (void)} 0x400490 <main>
(gdb) print foo32
$2 = {int (void)} 0x400684 <foo32>
(gdb) print foo32p
$3 = (int (*)(void)) 0x400684 <foo32>
(gdb) print bar
$4 = {int (void)} 0x40068c <bar>
(gdb) print foo
$5 = {int (void)} 0x400680 <foo>
(gdb) print foop
$6 = (int (*)(void)) 0x400681 <foo>
(gdb)

A-ha!  Here's the difference and finally the ISA bit!

(gdb) print /x fooi
$7 = 0x400681
(gdb) p/x $pc
p/x $pc
$8 = 0x400491
(gdb)

And here as well...

(gdb) advance foo
foo () at foobar.c:4
4       }
(gdb) disassemble
Dump of assembler code for function foo:
   0x00400680 <+0>:     jr      ra
   0x00400682 <+2>:     li      v0,1
End of assembler dump.
(gdb) finish
Run till exit from #0  foo () at foobar.c:4
main () at foobar.c:24
24      }
Value returned is $9 = 1
(gdb) continue
Continuing.
[Inferior 1 (process 14103) exited with code 01]
(gdb)

So let's be a bit inquisitive...

(gdb) run
Starting program: .../foobar

Breakpoint 1, main () at foobar.c:23
23        return foop ();
(gdb)

Actually we do not like to run foo here at all.  Let's run bar instead!

(gdb) set foop = bar
(gdb) print foop
$10 = (int (*)(void)) 0x40068c <bar>
(gdb)

Hmm, no ISA bit.  Is it going to work?

(gdb) advance bar
bar () at foobar.c:9
9       }
(gdb) p/x $pc
$11 = 0x40068c
(gdb) disassemble
Dump of assembler code for function bar:
=> 0x0040068c <+0>:     jr      ra
   0x0040068e <+2>:     li      v0,2
End of assembler dump.
(gdb) finish
Run till exit from #0  bar () at foobar.c:9

Program received signal SIGILL, Illegal instruction.
bar () at foobar.c:9
9       }
(gdb)

Oops!

(gdb) p/x $pc
$12 = 0x40068c
(gdb)

We're still there!

(gdb) continue
Continuing.

Program terminated with signal SIGILL, Illegal instruction.
The program no longer exists.
(gdb)

So let's try something else:

(gdb) run
Starting program: .../foobar

Breakpoint 1, main () at foobar.c:23
23        return foop ();
(gdb) set foop = foo
(gdb) advance foo
foo () at foobar.c:4
4       }
(gdb) disassemble
Dump of assembler code for function foo:
=> 0x00400680 <+0>:     jr      ra
   0x00400682 <+2>:     li      v0,1
End of assembler dump.
(gdb) finish
Run till exit from #0  foo () at foobar.c:4

Program received signal SIGILL, Illegal instruction.
foo () at foobar.c:4
4       }
(gdb) continue
Continuing.

Program terminated with signal SIGILL, Illegal instruction.
The program no longer exists.
(gdb)

The same problem!

(gdb) run
Starting program:
/net/build2-lucid-cs/scratch/macro/mips-linux-fsf-gcc/isa-bit/foobar

Breakpoint 1, main () at foobar.c:23
23        return foop ();
(gdb) set foop = foo32
(gdb) advance foo32
foo32 () at foobar.c:14
14      }
(gdb) disassemble
Dump of assembler code for function foo32:
=> 0x00400684 <+0>:     jr      ra
   0x00400688 <+4>:     li      v0,3
End of assembler dump.
(gdb) finish
Run till exit from #0  foo32 () at foobar.c:14
main () at foobar.c:24
24      }
Value returned is $14 = 3
(gdb) continue
Continuing.
[Inferior 1 (process 14113) exited with code 03]
(gdb)

That did work though, so it's the ISA bit only!

(gdb) quit

Enough!

That's the tip of the iceberg only though.  So let's rebuild the
executable with some dynamic symbols:

$ mips-linux-gnu-gcc -mips16 -Wl,--export-dynamic -g -O2 -o foobar-dyn foobar.c
$ mips-linux-gnu-readelf -s foobar-dyn | egrep 'table|foo|bar'
Symbol table '.dynsym' contains 32 entries:
     6: 004009cd     4 FUNC    GLOBAL DEFAULT   12 bar
     8: 00410b88     4 OBJECT  GLOBAL DEFAULT   21 foo32p
     9: 00410b84     4 OBJECT  GLOBAL DEFAULT   21 foop
    15: 004009c4     8 FUNC    GLOBAL DEFAULT   12 foo32
    17: 004009c1     4 FUNC    GLOBAL DEFAULT   12 foo
    25: 00410b80     4 OBJECT  GLOBAL DEFAULT   21 fooi
Symbol table '.symtab' contains 95 entries:
    55: 00000000     0 FILE    LOCAL  DEFAULT  ABS foobar.c
    69: 004009cd     4 FUNC    GLOBAL DEFAULT   12 bar
    71: 00410b88     4 OBJECT  GLOBAL DEFAULT   21 foo32p
    72: 00410b84     4 OBJECT  GLOBAL DEFAULT   21 foop
    79: 004009c4     8 FUNC    GLOBAL DEFAULT   12 foo32
    81: 004009c1     4 FUNC    GLOBAL DEFAULT   12 foo
    89: 00410b80     4 OBJECT  GLOBAL DEFAULT   21 fooi
$

OK, now the ISA bit is there for a change, but the MIPS16 `st_other'
attribute gone, hmm...  What does `objdump' do then:

$ mips-linux-gnu-objdump -Tt foobar-dyn | egrep 'SYMBOL|foo|bar'
foobar-dyn:     file format elf32-tradbigmips
SYMBOL TABLE:
00000000 l    df *ABS*  00000000              foobar.c
004009cc g     F .text  00000004              0xf0 bar
00410b88 g     O .data  00000004              foo32p
00410b84 g     O .data  00000004              foop
004009c4 g     F .text  00000008              foo32
004009c0 g     F .text  00000004              0xf0 foo
00410b80 g     O .data  00000004              fooi
DYNAMIC SYMBOL TABLE:
004009cc g    DF .text  00000004  Base        0xf0 bar
00410b88 g    DO .data  00000004  Base        foo32p
00410b84 g    DO .data  00000004  Base        foop
004009c4 g    DF .text  00000008  Base        foo32
004009c0 g    DF .text  00000004  Base        0xf0 foo
00410b80 g    DO .data  00000004  Base        fooi
$

Hmm, the attribute (0xf0, printed raw) is back, and the ISA bit gone
again.

Let's have a look at some DWARF-2 records GDB uses (I'll be stripping
off a lot here for brevity) -- debug info:

$ mips-linux-gnu-readelf -wi foobar
Contents of the .debug_info section:
[...]
  Compilation Unit @ offset 0x88:
   Length:        0xbb (32-bit)
   Version:       4
   Abbrev Offset: 62
   Pointer Size:  4
 <0><93>: Abbrev Number: 1 (DW_TAG_compile_unit)
    <94>   DW_AT_producer    : (indirect string, offset: 0x19e): GNU C 4.8.0 20120513 (experimental) -meb -mips16 -march=mips32r2 -mhard-float -mllsc -mplt -mno-synci -mno-shared -mabi=32 -g -O2
    <98>   DW_AT_language    : 1        (ANSI C)
    <99>   DW_AT_name        : (indirect string, offset: 0x190): foobar.c
    <9d>   DW_AT_comp_dir    : (indirect string, offset: 0x225): [...]
    <a1>   DW_AT_ranges      : 0x0
    <a5>   DW_AT_low_pc      : 0x0
    <a9>   DW_AT_stmt_list   : 0x27
 <1><ad>: Abbrev Number: 2 (DW_TAG_subprogram)
    <ae>   DW_AT_external    : 1
    <ae>   DW_AT_name        : foo
    <b2>   DW_AT_decl_file   : 1
    <b3>   DW_AT_decl_line   : 1
    <b4>   DW_AT_prototyped  : 1
    <b4>   DW_AT_type        : <0xc2>
    <b8>   DW_AT_low_pc      : 0x400680
    <bc>   DW_AT_high_pc     : 0x400684
    <c0>   DW_AT_frame_base  : 1 byte block: 9c         (DW_OP_call_frame_cfa)
    <c2>   DW_AT_GNU_all_call_sites: 1
 <1><c2>: Abbrev Number: 3 (DW_TAG_base_type)
    <c3>   DW_AT_byte_size   : 4
    <c4>   DW_AT_encoding    : 5        (signed)
    <c5>   DW_AT_name        : int
 <1><c9>: Abbrev Number: 4 (DW_TAG_subprogram)
    <ca>   DW_AT_external    : 1
    <ca>   DW_AT_name        : (indirect string, offset: 0x18a): foo32
    <ce>   DW_AT_decl_file   : 1
    <cf>   DW_AT_decl_line   : 11
    <d0>   DW_AT_prototyped  : 1
    <d0>   DW_AT_type        : <0xc2>
    <d4>   DW_AT_low_pc      : 0x400684
    <d8>   DW_AT_high_pc     : 0x40068c
    <dc>   DW_AT_frame_base  : 1 byte block: 9c         (DW_OP_call_frame_cfa)
    <de>   DW_AT_GNU_all_call_sites: 1
 <1><de>: Abbrev Number: 2 (DW_TAG_subprogram)
    <df>   DW_AT_external    : 1
    <df>   DW_AT_name        : bar
    <e3>   DW_AT_decl_file   : 1
    <e4>   DW_AT_decl_line   : 6
    <e5>   DW_AT_prototyped  : 1
    <e5>   DW_AT_type        : <0xc2>
    <e9>   DW_AT_low_pc      : 0x40068c
    <ed>   DW_AT_high_pc     : 0x400690
    <f1>   DW_AT_frame_base  : 1 byte block: 9c         (DW_OP_call_frame_cfa)
    <f3>   DW_AT_GNU_all_call_sites: 1
 <1><f3>: Abbrev Number: 5 (DW_TAG_subprogram)
    <f4>   DW_AT_external    : 1
    <f4>   DW_AT_name        : (indirect string, offset: 0x199): main
    <f8>   DW_AT_decl_file   : 1
    <f9>   DW_AT_decl_line   : 21
    <fa>   DW_AT_prototyped  : 1
    <fa>   DW_AT_type        : <0xc2>
    <fe>   DW_AT_low_pc      : 0x400490
    <102>   DW_AT_high_pc     : 0x4004a4
    <106>   DW_AT_frame_base  : 1 byte block: 9c        (DW_OP_call_frame_cfa)
    <108>   DW_AT_GNU_all_tail_call_sites: 1
[...]
$

-- no sign of the ISA bit anywhere -- frame info:

$ mips-linux-gnu-readelf -wf foobar
[...]
Contents of the .debug_frame section:

00000000 0000000c ffffffff CIE
  Version:               1
  Augmentation:          ""
  Code alignment factor: 1
  Data alignment factor: -4
  Return address column: 31

  DW_CFA_def_cfa_register: r29
  DW_CFA_nop

00000010 0000000c 00000000 FDE cie=00000000 pc=00400680..00400684

00000020 0000000c 00000000 FDE cie=00000000 pc=00400684..0040068c

00000030 0000000c 00000000 FDE cie=00000000 pc=0040068c..00400690

00000040 00000018 00000000 FDE cie=00000000 pc=00400490..004004a4
  DW_CFA_advance_loc: 6 to 00400496
  DW_CFA_def_cfa_offset: 32
  DW_CFA_offset: r31 at cfa-4
  DW_CFA_advance_loc: 6 to 0040049c
  DW_CFA_restore: r31
  DW_CFA_def_cfa_offset: 0
  DW_CFA_nop
  DW_CFA_nop
  DW_CFA_nop
[...]
$

-- no sign of the ISA bit anywhere -- range info (GDB doesn't use arange):

$ mips-linux-gnu-readelf -wR foobar
Contents of the .debug_ranges section:

    Offset   Begin    End
    00000000 00400680 00400690
    00000000 00400490 004004a4
    00000000 <End of list>

$

-- no sign of the ISA bit anywhere -- line info:

$ mips-linux-gnu-readelf -wl foobar
Raw dump of debug contents of section .debug_line:
[...]
  Offset:                      0x27
  Length:                      78
  DWARF Version:               2
  Prologue Length:             31
  Minimum Instruction Length:  1
  Initial value of 'is_stmt':  1
  Line Base:                   -5
  Line Range:                  14
  Opcode Base:                 13

 Opcodes:
  Opcode 1 has 0 args
  Opcode 2 has 1 args
  Opcode 3 has 1 args
  Opcode 4 has 1 args
  Opcode 5 has 1 args
  Opcode 6 has 0 args
  Opcode 7 has 0 args
  Opcode 8 has 0 args
  Opcode 9 has 1 args
  Opcode 10 has 0 args
  Opcode 11 has 0 args
  Opcode 12 has 1 args

 The Directory Table is empty.

 The File Name Table:
  Entry Dir     Time    Size    Name
  1     0       0       0       foobar.c

 Line Number Statements:
  Extended opcode 2: set Address to 0x400681
  Special opcode 6: advance Address by 0 to 0x400681 and Line by 1 to 2
  Special opcode 7: advance Address by 0 to 0x400681 and Line by 2 to 4
  Special opcode 55: advance Address by 3 to 0x400684 and Line by 8 to 12
  Special opcode 7: advance Address by 0 to 0x400684 and Line by 2 to 14
  Advance Line by -7 to 7
  Special opcode 131: advance Address by 9 to 0x40068d and Line by 0 to 7
  Special opcode 7: advance Address by 0 to 0x40068d and Line by 2 to 9
  Advance PC by 3 to 0x400690
  Extended opcode 1: End of Sequence

  Extended opcode 2: set Address to 0x400491
  Advance Line by 21 to 22
  Copy
  Special opcode 6: advance Address by 0 to 0x400491 and Line by 1 to 23
  Special opcode 60: advance Address by 4 to 0x400495 and Line by -1 to 22
  Special opcode 34: advance Address by 2 to 0x400497 and Line by 1 to 23
  Special opcode 62: advance Address by 4 to 0x40049b and Line by 1 to 24
  Special opcode 32: advance Address by 2 to 0x40049d and Line by -1 to 23
  Special opcode 6: advance Address by 0 to 0x40049d and Line by 1 to 24
  Advance PC by 7 to 0x4004a4
  Extended opcode 1: End of Sequence
[...]

-- a-ha, the ISA bit is there!  However it's not always right for some
reason, I don't have a small test case to show it, but here's an excerpt
from MIPS16 libc, a prologue of a function:

00019630 <__libc_init_first>:
   19630:       e8a0            jrc     ra
   19632:       6500            nop

00019634 <_init>:
   19634:       f000 6a11       li      v0,17
   19638:       f7d8 0b08       la      v1,15e00 <_DYNAMIC+0x15c54>
   1963c:       f400 3240       sll     v0,16
   19640:       e269            addu    v0,v1
   19642:       659a            move    gp,v0
   19644:       64f6            save    48,ra,s0-s1
   19646:       671c            move    s0,gp
   19648:       d204            sw      v0,16(sp)
   1964a:       f352 984c       lw      v0,-27828(s0)
   1964e:       6724            move    s1,a0

and the corresponding DWARF-2 line info:

 Line Number Statements:
  Extended opcode 2: set Address to 0x19631
  Advance Line by 44 to 45
  Copy
  Special opcode 8: advance Address by 0 to 0x19631 and Line by 3 to 48
  Special opcode 66: advance Address by 4 to 0x19635 and Line by 5 to 53
  Advance PC by constant 17 to 0x19646
  Special opcode 25: advance Address by 1 to 0x19647 and Line by 6 to 59
  Advance Line by -6 to 53
  Special opcode 33: advance Address by 2 to 0x19649 and Line by 0 to 53
  Special opcode 39: advance Address by 2 to 0x1964b and Line by 6 to 59
  Advance Line by -6 to 53
  Special opcode 61: advance Address by 4 to 0x1964f and Line by 0 to 53

-- see that "Advance PC by constant 17" there?  It clears the ISA bit,
however code at 0x19646 is not standard MIPS code at all.  For some
reason the constant is always 17, I've never seen DW_LNS_const_add_pc
used with any other value -- is that a binutils bug or what?

3. Solution:

I think we should retain the value of the ISA bit in code references,
that is effectively treat them as cookies as they indeed are (although
trivially calculated) rather than raw memory byte addresses.

In a perfect world both the static symbol table and the respective
DWARF-2 records should be fixed to include the ISA bit in all the cases.
I think however that this is infeasible.

All the uses of `_bfd_mips_elf_symbol_processing' can not necessarily be
tracked down.  This function is used by `elf_slurp_symbol_table' that in
turn is used by `bfd_canonicalize_symtab' and
`bfd_canonicalize_dynamic_symtab', which are public interfaces.

Similarly DWARF-2 records are used outside GDB, one notable if a bit
questionable is the exception unwinder (libgcc/unwind-dw2.c) -- I have
identified at least bits in `execute_cfa_program' and
`uw_frame_state_for', both around the calls to `_Unwind_IsSignalFrame',
that would need an update as they effectively flip the ISA bit freely;
see also the comment about MASK_RETURN_ADDR in gcc/config/mips/mips.h.
But there may be more places.  Any change in how DWARF-2 records are
produced would require an update there and would cause compatibility
problems with libgcc.a binaries already distributed; given that this is
a static library a complex change involving function renames would
likely be required.

I propose therefore to accept the existing inconsistencies and deal with
them entirely within GDB.  I have figured out that the ISA bit lost in
various places can still be recovered as long as we have symbol
information -- that'll have the `st_other' attribute correctly set to
one of standard MIPS/MIPS16/microMIPS encoding.

Here's the resulting change.  It adds a couple of new `gdbarch' hooks,
one to update symbol information with the ISA bit lost in
`_bfd_mips_elf_symbol_processing', and two other ones to adjust DWARF-2
records as they're processed.  The ISA bit is set in each address
handled according to information retrieved from the symbol table for the
symbol spanning the address if any; limits are adjusted based on the
address they point to related to the respective base address.
Additionally minimal symbol information has to be adjusted accordingly
in its gdbarch hook.

With these changes in place some complications with ISA bit juggling in
the PC that never fully worked can be removed from the MIPS backend.
Conversely, the generic dynamic linker event special breakpoint symbol
handler has to be updated to call the minimal symbol gdbarch hook to
record that the symbol is a MIPS16 or microMIPS address if applicable or
the breakpoint will be set at the wrong address and either fail to work
or cause SIGTRAPs (this is because the symbol is handled early on and
bypasses regular symbol processing).

4. Results obtained

The change fixes the example above -- to repeat only the crucial steps:

(gdb) break main
Breakpoint 1 at 0x400491: file foobar.c, line 23.
(gdb) run
Starting program: .../foobar

Breakpoint 1, main () at foobar.c:23
23        return foop ();
(gdb) print foo
$1 = {int (void)} 0x400681 <foo>
(gdb) set foop = bar
(gdb) advance bar
bar () at foobar.c:9
9       }
(gdb) disassemble
Dump of assembler code for function bar:
=> 0x0040068d <+0>:     jr      ra
   0x0040068f <+2>:     li      v0,2
End of assembler dump.
(gdb) finish
Run till exit from #0  bar () at foobar.c:9
main () at foobar.c:24
24      }
Value returned is $2 = 2
(gdb) continue
Continuing.
[Inferior 1 (process 14128) exited with code 02]
(gdb)

-- excellent!

The change removes about 90 failures per MIPS16 multilib in mips-sde-elf
testing too, results for MIPS16 are now similar to that for standard
MIPS; microMIPS results are a bit worse because of host-I/O problems in
QEMU used instead of MIPSsim for microMIPS testing only:

                === gdb Summary ===

# of expected passes            14299
# of unexpected failures        187
# of expected failures          56
# of known failures             58
# of unresolved testcases       11
# of untested testcases         52
# of unsupported tests          174

MIPS16:

                === gdb Summary ===

# of expected passes            14298
# of unexpected failures        187
# of unexpected successes       2
# of expected failures          54
# of known failures             58
# of unresolved testcases       12
# of untested testcases         52
# of unsupported tests          174

microMIPS:

                === gdb Summary ===

# of expected passes            14149
# of unexpected failures        201
# of unexpected successes       2
# of expected failures          54
# of known failures             58
# of unresolved testcases       7
# of untested testcases         53
# of unsupported tests          175

2014-12-12  Maciej W. Rozycki  <macro@codesourcery.com>
            Maciej W. Rozycki  <macro@mips.com>
            Pedro Alves  <pedro@codesourcery.com>

	gdb/
	* gdbarch.sh (elf_make_msymbol_special): Change type to `F',
	remove `predefault' and `invalid_p' initializers.
	(make_symbol_special): New architecture method.
	(adjust_dwarf2_addr, adjust_dwarf2_line): Likewise.
	(objfile, symbol): New declarations.
	* arch-utils.h (default_elf_make_msymbol_special): Remove
	prototype.
	(default_make_symbol_special): New prototype.
	(default_adjust_dwarf2_addr): Likewise.
	(default_adjust_dwarf2_line): Likewise.
	* mips-tdep.h (mips_unmake_compact_addr): New prototype.
	* arch-utils.c (default_elf_make_msymbol_special): Remove
	function.
	(default_make_symbol_special): New function.
	(default_adjust_dwarf2_addr): Likewise.
	(default_adjust_dwarf2_line): Likewise.
	* dwarf2-frame.c (decode_frame_entry_1): Call
	`gdbarch_adjust_dwarf2_addr'.
	* dwarf2loc.c (dwarf2_find_location_expression): Likewise.
	* dwarf2read.c (create_addrmap_from_index): Likewise.
	(process_psymtab_comp_unit_reader): Likewise.
	(add_partial_symbol): Likewise.
	(add_partial_subprogram): Likewise.
	(process_full_comp_unit): Likewise.
	(read_file_scope): Likewise.
	(read_func_scope): Likewise.  Call `gdbarch_make_symbol_special'.
	(read_lexical_block_scope): Call `gdbarch_adjust_dwarf2_addr'.
	(read_call_site_scope): Likewise.
	(dwarf2_ranges_read): Likewise.
	(dwarf2_record_block_ranges): Likewise.
	(read_attribute_value): Likewise.
	(dwarf_decode_lines_1): Call `gdbarch_adjust_dwarf2_line'.
	(new_symbol_full): Call `gdbarch_adjust_dwarf2_addr'.
	* elfread.c (elf_symtab_read): Don't call
	`gdbarch_elf_make_msymbol_special' if unset.
	* mips-linux-tdep.c (micromips_linux_sigframe_validate): Strip
	the ISA bit from the PC.
	* mips-tdep.c (mips_unmake_compact_addr): New function.
	(mips_elf_make_msymbol_special): Set the ISA bit in the symbol's
	address appropriately.
	(mips_make_symbol_special): New function.
	(mips_pc_is_mips): Set the ISA bit before symbol lookup.
	(mips_pc_is_mips16): Likewise.
	(mips_pc_is_micromips): Likewise.
	(mips_pc_isa): Likewise.
	(mips_adjust_dwarf2_addr): New function.
	(mips_adjust_dwarf2_line): Likewise.
	(mips_read_pc, mips_unwind_pc): Keep the ISA bit.
	(mips_addr_bits_remove): Likewise.
	(mips_skip_trampoline_code): Likewise.
	(mips_write_pc): Don't set the ISA bit.
	(mips_eabi_push_dummy_call): Likewise.
	(mips_o64_push_dummy_call): Likewise.
	(mips_gdbarch_init): Install `mips_make_symbol_special',
	`mips_adjust_dwarf2_addr' and `mips_adjust_dwarf2_line' gdbarch
	handlers.
	* solib.c (gdb_bfd_lookup_symbol_from_symtab): Get
	target-specific symbol address adjustments.
	* gdbarch.h: Regenerate.
	* gdbarch.c: Regenerate.

2014-12-12  Maciej W. Rozycki  <macro@codesourcery.com>

	gdb/testsuite/
	* gdb.base/func-ptrs.c: New file.
	* gdb.base/func-ptrs.exp: New file.
2014-12-12 13:49:06 +00:00

2475 lines
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/* Frame unwinder for frames with DWARF Call Frame Information.
Copyright (C) 2003-2014 Free Software Foundation, Inc.
Contributed by Mark Kettenis.
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#include "defs.h"
#include "dwarf2expr.h"
#include "dwarf2.h"
#include "frame.h"
#include "frame-base.h"
#include "frame-unwind.h"
#include "gdbcore.h"
#include "gdbtypes.h"
#include "symtab.h"
#include "objfiles.h"
#include "regcache.h"
#include "value.h"
#include "record.h"
#include "complaints.h"
#include "dwarf2-frame.h"
#include "ax.h"
#include "dwarf2loc.h"
#include "dwarf2-frame-tailcall.h"
struct comp_unit;
/* Call Frame Information (CFI). */
/* Common Information Entry (CIE). */
struct dwarf2_cie
{
/* Computation Unit for this CIE. */
struct comp_unit *unit;
/* Offset into the .debug_frame section where this CIE was found.
Used to identify this CIE. */
ULONGEST cie_pointer;
/* Constant that is factored out of all advance location
instructions. */
ULONGEST code_alignment_factor;
/* Constants that is factored out of all offset instructions. */
LONGEST data_alignment_factor;
/* Return address column. */
ULONGEST return_address_register;
/* Instruction sequence to initialize a register set. */
const gdb_byte *initial_instructions;
const gdb_byte *end;
/* Saved augmentation, in case it's needed later. */
char *augmentation;
/* Encoding of addresses. */
gdb_byte encoding;
/* Target address size in bytes. */
int addr_size;
/* Target pointer size in bytes. */
int ptr_size;
/* True if a 'z' augmentation existed. */
unsigned char saw_z_augmentation;
/* True if an 'S' augmentation existed. */
unsigned char signal_frame;
/* The version recorded in the CIE. */
unsigned char version;
/* The segment size. */
unsigned char segment_size;
};
struct dwarf2_cie_table
{
int num_entries;
struct dwarf2_cie **entries;
};
/* Frame Description Entry (FDE). */
struct dwarf2_fde
{
/* CIE for this FDE. */
struct dwarf2_cie *cie;
/* First location associated with this FDE. */
CORE_ADDR initial_location;
/* Number of bytes of program instructions described by this FDE. */
CORE_ADDR address_range;
/* Instruction sequence. */
const gdb_byte *instructions;
const gdb_byte *end;
/* True if this FDE is read from a .eh_frame instead of a .debug_frame
section. */
unsigned char eh_frame_p;
};
struct dwarf2_fde_table
{
int num_entries;
struct dwarf2_fde **entries;
};
/* A minimal decoding of DWARF2 compilation units. We only decode
what's needed to get to the call frame information. */
struct comp_unit
{
/* Keep the bfd convenient. */
bfd *abfd;
struct objfile *objfile;
/* Pointer to the .debug_frame section loaded into memory. */
const gdb_byte *dwarf_frame_buffer;
/* Length of the loaded .debug_frame section. */
bfd_size_type dwarf_frame_size;
/* Pointer to the .debug_frame section. */
asection *dwarf_frame_section;
/* Base for DW_EH_PE_datarel encodings. */
bfd_vma dbase;
/* Base for DW_EH_PE_textrel encodings. */
bfd_vma tbase;
};
static struct dwarf2_fde *dwarf2_frame_find_fde (CORE_ADDR *pc,
CORE_ADDR *out_offset);
static int dwarf2_frame_adjust_regnum (struct gdbarch *gdbarch, int regnum,
int eh_frame_p);
static CORE_ADDR read_encoded_value (struct comp_unit *unit, gdb_byte encoding,
int ptr_len, const gdb_byte *buf,
unsigned int *bytes_read_ptr,
CORE_ADDR func_base);
/* Structure describing a frame state. */
struct dwarf2_frame_state
{
/* Each register save state can be described in terms of a CFA slot,
another register, or a location expression. */
struct dwarf2_frame_state_reg_info
{
struct dwarf2_frame_state_reg *reg;
int num_regs;
LONGEST cfa_offset;
ULONGEST cfa_reg;
enum {
CFA_UNSET,
CFA_REG_OFFSET,
CFA_EXP
} cfa_how;
const gdb_byte *cfa_exp;
/* Used to implement DW_CFA_remember_state. */
struct dwarf2_frame_state_reg_info *prev;
} regs;
/* The PC described by the current frame state. */
CORE_ADDR pc;
/* Initial register set from the CIE.
Used to implement DW_CFA_restore. */
struct dwarf2_frame_state_reg_info initial;
/* The information we care about from the CIE. */
LONGEST data_align;
ULONGEST code_align;
ULONGEST retaddr_column;
/* Flags for known producer quirks. */
/* The ARM compilers, in DWARF2 mode, assume that DW_CFA_def_cfa
and DW_CFA_def_cfa_offset takes a factored offset. */
int armcc_cfa_offsets_sf;
/* The ARM compilers, in DWARF2 or DWARF3 mode, may assume that
the CFA is defined as REG - OFFSET rather than REG + OFFSET. */
int armcc_cfa_offsets_reversed;
};
/* Store the length the expression for the CFA in the `cfa_reg' field,
which is unused in that case. */
#define cfa_exp_len cfa_reg
/* Assert that the register set RS is large enough to store gdbarch_num_regs
columns. If necessary, enlarge the register set. */
static void
dwarf2_frame_state_alloc_regs (struct dwarf2_frame_state_reg_info *rs,
int num_regs)
{
size_t size = sizeof (struct dwarf2_frame_state_reg);
if (num_regs <= rs->num_regs)
return;
rs->reg = (struct dwarf2_frame_state_reg *)
xrealloc (rs->reg, num_regs * size);
/* Initialize newly allocated registers. */
memset (rs->reg + rs->num_regs, 0, (num_regs - rs->num_regs) * size);
rs->num_regs = num_regs;
}
/* Copy the register columns in register set RS into newly allocated
memory and return a pointer to this newly created copy. */
static struct dwarf2_frame_state_reg *
dwarf2_frame_state_copy_regs (struct dwarf2_frame_state_reg_info *rs)
{
size_t size = rs->num_regs * sizeof (struct dwarf2_frame_state_reg);
struct dwarf2_frame_state_reg *reg;
reg = (struct dwarf2_frame_state_reg *) xmalloc (size);
memcpy (reg, rs->reg, size);
return reg;
}
/* Release the memory allocated to register set RS. */
static void
dwarf2_frame_state_free_regs (struct dwarf2_frame_state_reg_info *rs)
{
if (rs)
{
dwarf2_frame_state_free_regs (rs->prev);
xfree (rs->reg);
xfree (rs);
}
}
/* Release the memory allocated to the frame state FS. */
static void
dwarf2_frame_state_free (void *p)
{
struct dwarf2_frame_state *fs = p;
dwarf2_frame_state_free_regs (fs->initial.prev);
dwarf2_frame_state_free_regs (fs->regs.prev);
xfree (fs->initial.reg);
xfree (fs->regs.reg);
xfree (fs);
}
/* Helper functions for execute_stack_op. */
static CORE_ADDR
read_addr_from_reg (void *baton, int reg)
{
struct frame_info *this_frame = (struct frame_info *) baton;
struct gdbarch *gdbarch = get_frame_arch (this_frame);
int regnum = gdbarch_dwarf2_reg_to_regnum (gdbarch, reg);
return address_from_register (regnum, this_frame);
}
/* Implement struct dwarf_expr_context_funcs' "get_reg_value" callback. */
static struct value *
get_reg_value (void *baton, struct type *type, int reg)
{
struct frame_info *this_frame = (struct frame_info *) baton;
struct gdbarch *gdbarch = get_frame_arch (this_frame);
int regnum = gdbarch_dwarf2_reg_to_regnum (gdbarch, reg);
return value_from_register (type, regnum, this_frame);
}
static void
read_mem (void *baton, gdb_byte *buf, CORE_ADDR addr, size_t len)
{
read_memory (addr, buf, len);
}
/* Execute the required actions for both the DW_CFA_restore and
DW_CFA_restore_extended instructions. */
static void
dwarf2_restore_rule (struct gdbarch *gdbarch, ULONGEST reg_num,
struct dwarf2_frame_state *fs, int eh_frame_p)
{
ULONGEST reg;
gdb_assert (fs->initial.reg);
reg = dwarf2_frame_adjust_regnum (gdbarch, reg_num, eh_frame_p);
dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
/* Check if this register was explicitly initialized in the
CIE initial instructions. If not, default the rule to
UNSPECIFIED. */
if (reg < fs->initial.num_regs)
fs->regs.reg[reg] = fs->initial.reg[reg];
else
fs->regs.reg[reg].how = DWARF2_FRAME_REG_UNSPECIFIED;
if (fs->regs.reg[reg].how == DWARF2_FRAME_REG_UNSPECIFIED)
complaint (&symfile_complaints, _("\
incomplete CFI data; DW_CFA_restore unspecified\n\
register %s (#%d) at %s"),
gdbarch_register_name
(gdbarch, gdbarch_dwarf2_reg_to_regnum (gdbarch, reg)),
gdbarch_dwarf2_reg_to_regnum (gdbarch, reg),
paddress (gdbarch, fs->pc));
}
/* Virtual method table for execute_stack_op below. */
static const struct dwarf_expr_context_funcs dwarf2_frame_ctx_funcs =
{
read_addr_from_reg,
get_reg_value,
read_mem,
ctx_no_get_frame_base,
ctx_no_get_frame_cfa,
ctx_no_get_frame_pc,
ctx_no_get_tls_address,
ctx_no_dwarf_call,
ctx_no_get_base_type,
ctx_no_push_dwarf_reg_entry_value,
ctx_no_get_addr_index
};
static CORE_ADDR
execute_stack_op (const gdb_byte *exp, ULONGEST len, int addr_size,
CORE_ADDR offset, struct frame_info *this_frame,
CORE_ADDR initial, int initial_in_stack_memory)
{
struct dwarf_expr_context *ctx;
CORE_ADDR result;
struct cleanup *old_chain;
ctx = new_dwarf_expr_context ();
old_chain = make_cleanup_free_dwarf_expr_context (ctx);
make_cleanup_value_free_to_mark (value_mark ());
ctx->gdbarch = get_frame_arch (this_frame);
ctx->addr_size = addr_size;
ctx->ref_addr_size = -1;
ctx->offset = offset;
ctx->baton = this_frame;
ctx->funcs = &dwarf2_frame_ctx_funcs;
dwarf_expr_push_address (ctx, initial, initial_in_stack_memory);
dwarf_expr_eval (ctx, exp, len);
if (ctx->location == DWARF_VALUE_MEMORY)
result = dwarf_expr_fetch_address (ctx, 0);
else if (ctx->location == DWARF_VALUE_REGISTER)
result = read_addr_from_reg (this_frame,
value_as_long (dwarf_expr_fetch (ctx, 0)));
else
{
/* This is actually invalid DWARF, but if we ever do run across
it somehow, we might as well support it. So, instead, report
it as unimplemented. */
error (_("\
Not implemented: computing unwound register using explicit value operator"));
}
do_cleanups (old_chain);
return result;
}
/* Execute FDE program from INSN_PTR possibly up to INSN_END or up to inferior
PC. Modify FS state accordingly. Return current INSN_PTR where the
execution has stopped, one can resume it on the next call. */
static const gdb_byte *
execute_cfa_program (struct dwarf2_fde *fde, const gdb_byte *insn_ptr,
const gdb_byte *insn_end, struct gdbarch *gdbarch,
CORE_ADDR pc, struct dwarf2_frame_state *fs)
{
int eh_frame_p = fde->eh_frame_p;
unsigned int bytes_read;
enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
while (insn_ptr < insn_end && fs->pc <= pc)
{
gdb_byte insn = *insn_ptr++;
uint64_t utmp, reg;
int64_t offset;
if ((insn & 0xc0) == DW_CFA_advance_loc)
fs->pc += (insn & 0x3f) * fs->code_align;
else if ((insn & 0xc0) == DW_CFA_offset)
{
reg = insn & 0x3f;
reg = dwarf2_frame_adjust_regnum (gdbarch, reg, eh_frame_p);
insn_ptr = safe_read_uleb128 (insn_ptr, insn_end, &utmp);
offset = utmp * fs->data_align;
dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
fs->regs.reg[reg].how = DWARF2_FRAME_REG_SAVED_OFFSET;
fs->regs.reg[reg].loc.offset = offset;
}
else if ((insn & 0xc0) == DW_CFA_restore)
{
reg = insn & 0x3f;
dwarf2_restore_rule (gdbarch, reg, fs, eh_frame_p);
}
else
{
switch (insn)
{
case DW_CFA_set_loc:
fs->pc = read_encoded_value (fde->cie->unit, fde->cie->encoding,
fde->cie->ptr_size, insn_ptr,
&bytes_read, fde->initial_location);
/* Apply the objfile offset for relocatable objects. */
fs->pc += ANOFFSET (fde->cie->unit->objfile->section_offsets,
SECT_OFF_TEXT (fde->cie->unit->objfile));
insn_ptr += bytes_read;
break;
case DW_CFA_advance_loc1:
utmp = extract_unsigned_integer (insn_ptr, 1, byte_order);
fs->pc += utmp * fs->code_align;
insn_ptr++;
break;
case DW_CFA_advance_loc2:
utmp = extract_unsigned_integer (insn_ptr, 2, byte_order);
fs->pc += utmp * fs->code_align;
insn_ptr += 2;
break;
case DW_CFA_advance_loc4:
utmp = extract_unsigned_integer (insn_ptr, 4, byte_order);
fs->pc += utmp * fs->code_align;
insn_ptr += 4;
break;
case DW_CFA_offset_extended:
insn_ptr = safe_read_uleb128 (insn_ptr, insn_end, &reg);
reg = dwarf2_frame_adjust_regnum (gdbarch, reg, eh_frame_p);
insn_ptr = safe_read_uleb128 (insn_ptr, insn_end, &utmp);
offset = utmp * fs->data_align;
dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
fs->regs.reg[reg].how = DWARF2_FRAME_REG_SAVED_OFFSET;
fs->regs.reg[reg].loc.offset = offset;
break;
case DW_CFA_restore_extended:
insn_ptr = safe_read_uleb128 (insn_ptr, insn_end, &reg);
dwarf2_restore_rule (gdbarch, reg, fs, eh_frame_p);
break;
case DW_CFA_undefined:
insn_ptr = safe_read_uleb128 (insn_ptr, insn_end, &reg);
reg = dwarf2_frame_adjust_regnum (gdbarch, reg, eh_frame_p);
dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
fs->regs.reg[reg].how = DWARF2_FRAME_REG_UNDEFINED;
break;
case DW_CFA_same_value:
insn_ptr = safe_read_uleb128 (insn_ptr, insn_end, &reg);
reg = dwarf2_frame_adjust_regnum (gdbarch, reg, eh_frame_p);
dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
fs->regs.reg[reg].how = DWARF2_FRAME_REG_SAME_VALUE;
break;
case DW_CFA_register:
insn_ptr = safe_read_uleb128 (insn_ptr, insn_end, &reg);
reg = dwarf2_frame_adjust_regnum (gdbarch, reg, eh_frame_p);
insn_ptr = safe_read_uleb128 (insn_ptr, insn_end, &utmp);
utmp = dwarf2_frame_adjust_regnum (gdbarch, utmp, eh_frame_p);
dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
fs->regs.reg[reg].how = DWARF2_FRAME_REG_SAVED_REG;
fs->regs.reg[reg].loc.reg = utmp;
break;
case DW_CFA_remember_state:
{
struct dwarf2_frame_state_reg_info *new_rs;
new_rs = XNEW (struct dwarf2_frame_state_reg_info);
*new_rs = fs->regs;
fs->regs.reg = dwarf2_frame_state_copy_regs (&fs->regs);
fs->regs.prev = new_rs;
}
break;
case DW_CFA_restore_state:
{
struct dwarf2_frame_state_reg_info *old_rs = fs->regs.prev;
if (old_rs == NULL)
{
complaint (&symfile_complaints, _("\
bad CFI data; mismatched DW_CFA_restore_state at %s"),
paddress (gdbarch, fs->pc));
}
else
{
xfree (fs->regs.reg);
fs->regs = *old_rs;
xfree (old_rs);
}
}
break;
case DW_CFA_def_cfa:
insn_ptr = safe_read_uleb128 (insn_ptr, insn_end, &reg);
fs->regs.cfa_reg = reg;
insn_ptr = safe_read_uleb128 (insn_ptr, insn_end, &utmp);
if (fs->armcc_cfa_offsets_sf)
utmp *= fs->data_align;
fs->regs.cfa_offset = utmp;
fs->regs.cfa_how = CFA_REG_OFFSET;
break;
case DW_CFA_def_cfa_register:
insn_ptr = safe_read_uleb128 (insn_ptr, insn_end, &reg);
fs->regs.cfa_reg = dwarf2_frame_adjust_regnum (gdbarch, reg,
eh_frame_p);
fs->regs.cfa_how = CFA_REG_OFFSET;
break;
case DW_CFA_def_cfa_offset:
insn_ptr = safe_read_uleb128 (insn_ptr, insn_end, &utmp);
if (fs->armcc_cfa_offsets_sf)
utmp *= fs->data_align;
fs->regs.cfa_offset = utmp;
/* cfa_how deliberately not set. */
break;
case DW_CFA_nop:
break;
case DW_CFA_def_cfa_expression:
insn_ptr = safe_read_uleb128 (insn_ptr, insn_end, &utmp);
fs->regs.cfa_exp_len = utmp;
fs->regs.cfa_exp = insn_ptr;
fs->regs.cfa_how = CFA_EXP;
insn_ptr += fs->regs.cfa_exp_len;
break;
case DW_CFA_expression:
insn_ptr = safe_read_uleb128 (insn_ptr, insn_end, &reg);
reg = dwarf2_frame_adjust_regnum (gdbarch, reg, eh_frame_p);
dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
insn_ptr = safe_read_uleb128 (insn_ptr, insn_end, &utmp);
fs->regs.reg[reg].loc.exp = insn_ptr;
fs->regs.reg[reg].exp_len = utmp;
fs->regs.reg[reg].how = DWARF2_FRAME_REG_SAVED_EXP;
insn_ptr += utmp;
break;
case DW_CFA_offset_extended_sf:
insn_ptr = safe_read_uleb128 (insn_ptr, insn_end, &reg);
reg = dwarf2_frame_adjust_regnum (gdbarch, reg, eh_frame_p);
insn_ptr = safe_read_sleb128 (insn_ptr, insn_end, &offset);
offset *= fs->data_align;
dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
fs->regs.reg[reg].how = DWARF2_FRAME_REG_SAVED_OFFSET;
fs->regs.reg[reg].loc.offset = offset;
break;
case DW_CFA_val_offset:
insn_ptr = safe_read_uleb128 (insn_ptr, insn_end, &reg);
dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
insn_ptr = safe_read_uleb128 (insn_ptr, insn_end, &utmp);
offset = utmp * fs->data_align;
fs->regs.reg[reg].how = DWARF2_FRAME_REG_SAVED_VAL_OFFSET;
fs->regs.reg[reg].loc.offset = offset;
break;
case DW_CFA_val_offset_sf:
insn_ptr = safe_read_uleb128 (insn_ptr, insn_end, &reg);
dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
insn_ptr = safe_read_sleb128 (insn_ptr, insn_end, &offset);
offset *= fs->data_align;
fs->regs.reg[reg].how = DWARF2_FRAME_REG_SAVED_VAL_OFFSET;
fs->regs.reg[reg].loc.offset = offset;
break;
case DW_CFA_val_expression:
insn_ptr = safe_read_uleb128 (insn_ptr, insn_end, &reg);
dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
insn_ptr = safe_read_uleb128 (insn_ptr, insn_end, &utmp);
fs->regs.reg[reg].loc.exp = insn_ptr;
fs->regs.reg[reg].exp_len = utmp;
fs->regs.reg[reg].how = DWARF2_FRAME_REG_SAVED_VAL_EXP;
insn_ptr += utmp;
break;
case DW_CFA_def_cfa_sf:
insn_ptr = safe_read_uleb128 (insn_ptr, insn_end, &reg);
fs->regs.cfa_reg = dwarf2_frame_adjust_regnum (gdbarch, reg,
eh_frame_p);
insn_ptr = safe_read_sleb128 (insn_ptr, insn_end, &offset);
fs->regs.cfa_offset = offset * fs->data_align;
fs->regs.cfa_how = CFA_REG_OFFSET;
break;
case DW_CFA_def_cfa_offset_sf:
insn_ptr = safe_read_sleb128 (insn_ptr, insn_end, &offset);
fs->regs.cfa_offset = offset * fs->data_align;
/* cfa_how deliberately not set. */
break;
case DW_CFA_GNU_window_save:
/* This is SPARC-specific code, and contains hard-coded
constants for the register numbering scheme used by
GCC. Rather than having a architecture-specific
operation that's only ever used by a single
architecture, we provide the implementation here.
Incidentally that's what GCC does too in its
unwinder. */
{
int size = register_size (gdbarch, 0);
dwarf2_frame_state_alloc_regs (&fs->regs, 32);
for (reg = 8; reg < 16; reg++)
{
fs->regs.reg[reg].how = DWARF2_FRAME_REG_SAVED_REG;
fs->regs.reg[reg].loc.reg = reg + 16;
}
for (reg = 16; reg < 32; reg++)
{
fs->regs.reg[reg].how = DWARF2_FRAME_REG_SAVED_OFFSET;
fs->regs.reg[reg].loc.offset = (reg - 16) * size;
}
}
break;
case DW_CFA_GNU_args_size:
/* Ignored. */
insn_ptr = safe_read_uleb128 (insn_ptr, insn_end, &utmp);
break;
case DW_CFA_GNU_negative_offset_extended:
insn_ptr = safe_read_uleb128 (insn_ptr, insn_end, &reg);
reg = dwarf2_frame_adjust_regnum (gdbarch, reg, eh_frame_p);
insn_ptr = safe_read_uleb128 (insn_ptr, insn_end, &utmp);
offset = utmp * fs->data_align;
dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
fs->regs.reg[reg].how = DWARF2_FRAME_REG_SAVED_OFFSET;
fs->regs.reg[reg].loc.offset = -offset;
break;
default:
internal_error (__FILE__, __LINE__,
_("Unknown CFI encountered."));
}
}
}
if (fs->initial.reg == NULL)
{
/* Don't allow remember/restore between CIE and FDE programs. */
dwarf2_frame_state_free_regs (fs->regs.prev);
fs->regs.prev = NULL;
}
return insn_ptr;
}
/* Architecture-specific operations. */
/* Per-architecture data key. */
static struct gdbarch_data *dwarf2_frame_data;
struct dwarf2_frame_ops
{
/* Pre-initialize the register state REG for register REGNUM. */
void (*init_reg) (struct gdbarch *, int, struct dwarf2_frame_state_reg *,
struct frame_info *);
/* Check whether the THIS_FRAME is a signal trampoline. */
int (*signal_frame_p) (struct gdbarch *, struct frame_info *);
/* Convert .eh_frame register number to DWARF register number, or
adjust .debug_frame register number. */
int (*adjust_regnum) (struct gdbarch *, int, int);
};
/* Default architecture-specific register state initialization
function. */
static void
dwarf2_frame_default_init_reg (struct gdbarch *gdbarch, int regnum,
struct dwarf2_frame_state_reg *reg,
struct frame_info *this_frame)
{
/* If we have a register that acts as a program counter, mark it as
a destination for the return address. If we have a register that
serves as the stack pointer, arrange for it to be filled with the
call frame address (CFA). The other registers are marked as
unspecified.
We copy the return address to the program counter, since many
parts in GDB assume that it is possible to get the return address
by unwinding the program counter register. However, on ISA's
with a dedicated return address register, the CFI usually only
contains information to unwind that return address register.
The reason we're treating the stack pointer special here is
because in many cases GCC doesn't emit CFI for the stack pointer
and implicitly assumes that it is equal to the CFA. This makes
some sense since the DWARF specification (version 3, draft 8,
p. 102) says that:
"Typically, the CFA is defined to be the value of the stack
pointer at the call site in the previous frame (which may be
different from its value on entry to the current frame)."
However, this isn't true for all platforms supported by GCC
(e.g. IBM S/390 and zSeries). Those architectures should provide
their own architecture-specific initialization function. */
if (regnum == gdbarch_pc_regnum (gdbarch))
reg->how = DWARF2_FRAME_REG_RA;
else if (regnum == gdbarch_sp_regnum (gdbarch))
reg->how = DWARF2_FRAME_REG_CFA;
}
/* Return a default for the architecture-specific operations. */
static void *
dwarf2_frame_init (struct obstack *obstack)
{
struct dwarf2_frame_ops *ops;
ops = OBSTACK_ZALLOC (obstack, struct dwarf2_frame_ops);
ops->init_reg = dwarf2_frame_default_init_reg;
return ops;
}
/* Set the architecture-specific register state initialization
function for GDBARCH to INIT_REG. */
void
dwarf2_frame_set_init_reg (struct gdbarch *gdbarch,
void (*init_reg) (struct gdbarch *, int,
struct dwarf2_frame_state_reg *,
struct frame_info *))
{
struct dwarf2_frame_ops *ops = gdbarch_data (gdbarch, dwarf2_frame_data);
ops->init_reg = init_reg;
}
/* Pre-initialize the register state REG for register REGNUM. */
static void
dwarf2_frame_init_reg (struct gdbarch *gdbarch, int regnum,
struct dwarf2_frame_state_reg *reg,
struct frame_info *this_frame)
{
struct dwarf2_frame_ops *ops = gdbarch_data (gdbarch, dwarf2_frame_data);
ops->init_reg (gdbarch, regnum, reg, this_frame);
}
/* Set the architecture-specific signal trampoline recognition
function for GDBARCH to SIGNAL_FRAME_P. */
void
dwarf2_frame_set_signal_frame_p (struct gdbarch *gdbarch,
int (*signal_frame_p) (struct gdbarch *,
struct frame_info *))
{
struct dwarf2_frame_ops *ops = gdbarch_data (gdbarch, dwarf2_frame_data);
ops->signal_frame_p = signal_frame_p;
}
/* Query the architecture-specific signal frame recognizer for
THIS_FRAME. */
static int
dwarf2_frame_signal_frame_p (struct gdbarch *gdbarch,
struct frame_info *this_frame)
{
struct dwarf2_frame_ops *ops = gdbarch_data (gdbarch, dwarf2_frame_data);
if (ops->signal_frame_p == NULL)
return 0;
return ops->signal_frame_p (gdbarch, this_frame);
}
/* Set the architecture-specific adjustment of .eh_frame and .debug_frame
register numbers. */
void
dwarf2_frame_set_adjust_regnum (struct gdbarch *gdbarch,
int (*adjust_regnum) (struct gdbarch *,
int, int))
{
struct dwarf2_frame_ops *ops = gdbarch_data (gdbarch, dwarf2_frame_data);
ops->adjust_regnum = adjust_regnum;
}
/* Translate a .eh_frame register to DWARF register, or adjust a .debug_frame
register. */
static int
dwarf2_frame_adjust_regnum (struct gdbarch *gdbarch,
int regnum, int eh_frame_p)
{
struct dwarf2_frame_ops *ops = gdbarch_data (gdbarch, dwarf2_frame_data);
if (ops->adjust_regnum == NULL)
return regnum;
return ops->adjust_regnum (gdbarch, regnum, eh_frame_p);
}
static void
dwarf2_frame_find_quirks (struct dwarf2_frame_state *fs,
struct dwarf2_fde *fde)
{
struct compunit_symtab *cust;
cust = find_pc_compunit_symtab (fs->pc);
if (cust == NULL)
return;
if (producer_is_realview (COMPUNIT_PRODUCER (cust)))
{
if (fde->cie->version == 1)
fs->armcc_cfa_offsets_sf = 1;
if (fde->cie->version == 1)
fs->armcc_cfa_offsets_reversed = 1;
/* The reversed offset problem is present in some compilers
using DWARF3, but it was eventually fixed. Check the ARM
defined augmentations, which are in the format "armcc" followed
by a list of one-character options. The "+" option means
this problem is fixed (no quirk needed). If the armcc
augmentation is missing, the quirk is needed. */
if (fde->cie->version == 3
&& (strncmp (fde->cie->augmentation, "armcc", 5) != 0
|| strchr (fde->cie->augmentation + 5, '+') == NULL))
fs->armcc_cfa_offsets_reversed = 1;
return;
}
}
void
dwarf2_compile_cfa_to_ax (struct agent_expr *expr, struct axs_value *loc,
struct gdbarch *gdbarch,
CORE_ADDR pc,
struct dwarf2_per_cu_data *data)
{
struct dwarf2_fde *fde;
CORE_ADDR text_offset;
struct dwarf2_frame_state fs;
int addr_size;
memset (&fs, 0, sizeof (struct dwarf2_frame_state));
fs.pc = pc;
/* Find the correct FDE. */
fde = dwarf2_frame_find_fde (&fs.pc, &text_offset);
if (fde == NULL)
error (_("Could not compute CFA; needed to translate this expression"));
/* Extract any interesting information from the CIE. */
fs.data_align = fde->cie->data_alignment_factor;
fs.code_align = fde->cie->code_alignment_factor;
fs.retaddr_column = fde->cie->return_address_register;
addr_size = fde->cie->addr_size;
/* Check for "quirks" - known bugs in producers. */
dwarf2_frame_find_quirks (&fs, fde);
/* First decode all the insns in the CIE. */
execute_cfa_program (fde, fde->cie->initial_instructions,
fde->cie->end, gdbarch, pc, &fs);
/* Save the initialized register set. */
fs.initial = fs.regs;
fs.initial.reg = dwarf2_frame_state_copy_regs (&fs.regs);
/* Then decode the insns in the FDE up to our target PC. */
execute_cfa_program (fde, fde->instructions, fde->end, gdbarch, pc, &fs);
/* Calculate the CFA. */
switch (fs.regs.cfa_how)
{
case CFA_REG_OFFSET:
{
int regnum = gdbarch_dwarf2_reg_to_regnum (gdbarch, fs.regs.cfa_reg);
if (regnum == -1)
error (_("Unable to access DWARF register number %d"),
(int) fs.regs.cfa_reg); /* FIXME */
ax_reg (expr, regnum);
if (fs.regs.cfa_offset != 0)
{
if (fs.armcc_cfa_offsets_reversed)
ax_const_l (expr, -fs.regs.cfa_offset);
else
ax_const_l (expr, fs.regs.cfa_offset);
ax_simple (expr, aop_add);
}
}
break;
case CFA_EXP:
ax_const_l (expr, text_offset);
dwarf2_compile_expr_to_ax (expr, loc, gdbarch, addr_size,
fs.regs.cfa_exp,
fs.regs.cfa_exp + fs.regs.cfa_exp_len,
data);
break;
default:
internal_error (__FILE__, __LINE__, _("Unknown CFA rule."));
}
}
struct dwarf2_frame_cache
{
/* DWARF Call Frame Address. */
CORE_ADDR cfa;
/* Set if the return address column was marked as unavailable
(required non-collected memory or registers to compute). */
int unavailable_retaddr;
/* Set if the return address column was marked as undefined. */
int undefined_retaddr;
/* Saved registers, indexed by GDB register number, not by DWARF
register number. */
struct dwarf2_frame_state_reg *reg;
/* Return address register. */
struct dwarf2_frame_state_reg retaddr_reg;
/* Target address size in bytes. */
int addr_size;
/* The .text offset. */
CORE_ADDR text_offset;
/* True if we already checked whether this frame is the bottom frame
of a virtual tail call frame chain. */
int checked_tailcall_bottom;
/* If not NULL then this frame is the bottom frame of a TAILCALL_FRAME
sequence. If NULL then it is a normal case with no TAILCALL_FRAME
involved. Non-bottom frames of a virtual tail call frames chain use
dwarf2_tailcall_frame_unwind unwinder so this field does not apply for
them. */
void *tailcall_cache;
/* The number of bytes to subtract from TAILCALL_FRAME frames frame
base to get the SP, to simulate the return address pushed on the
stack. */
LONGEST entry_cfa_sp_offset;
int entry_cfa_sp_offset_p;
};
/* A cleanup that sets a pointer to NULL. */
static void
clear_pointer_cleanup (void *arg)
{
void **ptr = arg;
*ptr = NULL;
}
static struct dwarf2_frame_cache *
dwarf2_frame_cache (struct frame_info *this_frame, void **this_cache)
{
struct cleanup *reset_cache_cleanup, *old_chain;
struct gdbarch *gdbarch = get_frame_arch (this_frame);
const int num_regs = gdbarch_num_regs (gdbarch)
+ gdbarch_num_pseudo_regs (gdbarch);
struct dwarf2_frame_cache *cache;
struct dwarf2_frame_state *fs;
struct dwarf2_fde *fde;
volatile struct gdb_exception ex;
CORE_ADDR entry_pc;
const gdb_byte *instr;
if (*this_cache)
return *this_cache;
/* Allocate a new cache. */
cache = FRAME_OBSTACK_ZALLOC (struct dwarf2_frame_cache);
cache->reg = FRAME_OBSTACK_CALLOC (num_regs, struct dwarf2_frame_state_reg);
*this_cache = cache;
reset_cache_cleanup = make_cleanup (clear_pointer_cleanup, this_cache);
/* Allocate and initialize the frame state. */
fs = XCNEW (struct dwarf2_frame_state);
old_chain = make_cleanup (dwarf2_frame_state_free, fs);
/* Unwind the PC.
Note that if the next frame is never supposed to return (i.e. a call
to abort), the compiler might optimize away the instruction at
its return address. As a result the return address will
point at some random instruction, and the CFI for that
instruction is probably worthless to us. GCC's unwinder solves
this problem by substracting 1 from the return address to get an
address in the middle of a presumed call instruction (or the
instruction in the associated delay slot). This should only be
done for "normal" frames and not for resume-type frames (signal
handlers, sentinel frames, dummy frames). The function
get_frame_address_in_block does just this. It's not clear how
reliable the method is though; there is the potential for the
register state pre-call being different to that on return. */
fs->pc = get_frame_address_in_block (this_frame);
/* Find the correct FDE. */
fde = dwarf2_frame_find_fde (&fs->pc, &cache->text_offset);
gdb_assert (fde != NULL);
/* Extract any interesting information from the CIE. */
fs->data_align = fde->cie->data_alignment_factor;
fs->code_align = fde->cie->code_alignment_factor;
fs->retaddr_column = fde->cie->return_address_register;
cache->addr_size = fde->cie->addr_size;
/* Check for "quirks" - known bugs in producers. */
dwarf2_frame_find_quirks (fs, fde);
/* First decode all the insns in the CIE. */
execute_cfa_program (fde, fde->cie->initial_instructions,
fde->cie->end, gdbarch,
get_frame_address_in_block (this_frame), fs);
/* Save the initialized register set. */
fs->initial = fs->regs;
fs->initial.reg = dwarf2_frame_state_copy_regs (&fs->regs);
if (get_frame_func_if_available (this_frame, &entry_pc))
{
/* Decode the insns in the FDE up to the entry PC. */
instr = execute_cfa_program (fde, fde->instructions, fde->end, gdbarch,
entry_pc, fs);
if (fs->regs.cfa_how == CFA_REG_OFFSET
&& (gdbarch_dwarf2_reg_to_regnum (gdbarch, fs->regs.cfa_reg)
== gdbarch_sp_regnum (gdbarch)))
{
cache->entry_cfa_sp_offset = fs->regs.cfa_offset;
cache->entry_cfa_sp_offset_p = 1;
}
}
else
instr = fde->instructions;
/* Then decode the insns in the FDE up to our target PC. */
execute_cfa_program (fde, instr, fde->end, gdbarch,
get_frame_address_in_block (this_frame), fs);
TRY_CATCH (ex, RETURN_MASK_ERROR)
{
/* Calculate the CFA. */
switch (fs->regs.cfa_how)
{
case CFA_REG_OFFSET:
cache->cfa = read_addr_from_reg (this_frame, fs->regs.cfa_reg);
if (fs->armcc_cfa_offsets_reversed)
cache->cfa -= fs->regs.cfa_offset;
else
cache->cfa += fs->regs.cfa_offset;
break;
case CFA_EXP:
cache->cfa =
execute_stack_op (fs->regs.cfa_exp, fs->regs.cfa_exp_len,
cache->addr_size, cache->text_offset,
this_frame, 0, 0);
break;
default:
internal_error (__FILE__, __LINE__, _("Unknown CFA rule."));
}
}
if (ex.reason < 0)
{
if (ex.error == NOT_AVAILABLE_ERROR)
{
cache->unavailable_retaddr = 1;
do_cleanups (old_chain);
discard_cleanups (reset_cache_cleanup);
return cache;
}
throw_exception (ex);
}
/* Initialize the register state. */
{
int regnum;
for (regnum = 0; regnum < num_regs; regnum++)
dwarf2_frame_init_reg (gdbarch, regnum, &cache->reg[regnum], this_frame);
}
/* Go through the DWARF2 CFI generated table and save its register
location information in the cache. Note that we don't skip the
return address column; it's perfectly all right for it to
correspond to a real register. If it doesn't correspond to a
real register, or if we shouldn't treat it as such,
gdbarch_dwarf2_reg_to_regnum should be defined to return a number outside
the range [0, gdbarch_num_regs). */
{
int column; /* CFI speak for "register number". */
for (column = 0; column < fs->regs.num_regs; column++)
{
/* Use the GDB register number as the destination index. */
int regnum = gdbarch_dwarf2_reg_to_regnum (gdbarch, column);
/* If there's no corresponding GDB register, ignore it. */
if (regnum < 0 || regnum >= num_regs)
continue;
/* NOTE: cagney/2003-09-05: CFI should specify the disposition
of all debug info registers. If it doesn't, complain (but
not too loudly). It turns out that GCC assumes that an
unspecified register implies "same value" when CFI (draft
7) specifies nothing at all. Such a register could equally
be interpreted as "undefined". Also note that this check
isn't sufficient; it only checks that all registers in the
range [0 .. max column] are specified, and won't detect
problems when a debug info register falls outside of the
table. We need a way of iterating through all the valid
DWARF2 register numbers. */
if (fs->regs.reg[column].how == DWARF2_FRAME_REG_UNSPECIFIED)
{
if (cache->reg[regnum].how == DWARF2_FRAME_REG_UNSPECIFIED)
complaint (&symfile_complaints, _("\
incomplete CFI data; unspecified registers (e.g., %s) at %s"),
gdbarch_register_name (gdbarch, regnum),
paddress (gdbarch, fs->pc));
}
else
cache->reg[regnum] = fs->regs.reg[column];
}
}
/* Eliminate any DWARF2_FRAME_REG_RA rules, and save the information
we need for evaluating DWARF2_FRAME_REG_RA_OFFSET rules. */
{
int regnum;
for (regnum = 0; regnum < num_regs; regnum++)
{
if (cache->reg[regnum].how == DWARF2_FRAME_REG_RA
|| cache->reg[regnum].how == DWARF2_FRAME_REG_RA_OFFSET)
{
struct dwarf2_frame_state_reg *retaddr_reg =
&fs->regs.reg[fs->retaddr_column];
/* It seems rather bizarre to specify an "empty" column as
the return adress column. However, this is exactly
what GCC does on some targets. It turns out that GCC
assumes that the return address can be found in the
register corresponding to the return address column.
Incidentally, that's how we should treat a return
address column specifying "same value" too. */
if (fs->retaddr_column < fs->regs.num_regs
&& retaddr_reg->how != DWARF2_FRAME_REG_UNSPECIFIED
&& retaddr_reg->how != DWARF2_FRAME_REG_SAME_VALUE)
{
if (cache->reg[regnum].how == DWARF2_FRAME_REG_RA)
cache->reg[regnum] = *retaddr_reg;
else
cache->retaddr_reg = *retaddr_reg;
}
else
{
if (cache->reg[regnum].how == DWARF2_FRAME_REG_RA)
{
cache->reg[regnum].loc.reg = fs->retaddr_column;
cache->reg[regnum].how = DWARF2_FRAME_REG_SAVED_REG;
}
else
{
cache->retaddr_reg.loc.reg = fs->retaddr_column;
cache->retaddr_reg.how = DWARF2_FRAME_REG_SAVED_REG;
}
}
}
}
}
if (fs->retaddr_column < fs->regs.num_regs
&& fs->regs.reg[fs->retaddr_column].how == DWARF2_FRAME_REG_UNDEFINED)
cache->undefined_retaddr = 1;
do_cleanups (old_chain);
discard_cleanups (reset_cache_cleanup);
return cache;
}
static enum unwind_stop_reason
dwarf2_frame_unwind_stop_reason (struct frame_info *this_frame,
void **this_cache)
{
struct dwarf2_frame_cache *cache
= dwarf2_frame_cache (this_frame, this_cache);
if (cache->unavailable_retaddr)
return UNWIND_UNAVAILABLE;
if (cache->undefined_retaddr)
return UNWIND_OUTERMOST;
return UNWIND_NO_REASON;
}
static void
dwarf2_frame_this_id (struct frame_info *this_frame, void **this_cache,
struct frame_id *this_id)
{
struct dwarf2_frame_cache *cache =
dwarf2_frame_cache (this_frame, this_cache);
if (cache->unavailable_retaddr)
(*this_id) = frame_id_build_unavailable_stack (get_frame_func (this_frame));
else if (cache->undefined_retaddr)
return;
else
(*this_id) = frame_id_build (cache->cfa, get_frame_func (this_frame));
}
static struct value *
dwarf2_frame_prev_register (struct frame_info *this_frame, void **this_cache,
int regnum)
{
struct gdbarch *gdbarch = get_frame_arch (this_frame);
struct dwarf2_frame_cache *cache =
dwarf2_frame_cache (this_frame, this_cache);
CORE_ADDR addr;
int realnum;
/* Check whether THIS_FRAME is the bottom frame of a virtual tail
call frame chain. */
if (!cache->checked_tailcall_bottom)
{
cache->checked_tailcall_bottom = 1;
dwarf2_tailcall_sniffer_first (this_frame, &cache->tailcall_cache,
(cache->entry_cfa_sp_offset_p
? &cache->entry_cfa_sp_offset : NULL));
}
/* Non-bottom frames of a virtual tail call frames chain use
dwarf2_tailcall_frame_unwind unwinder so this code does not apply for
them. If dwarf2_tailcall_prev_register_first does not have specific value
unwind the register, tail call frames are assumed to have the register set
of the top caller. */
if (cache->tailcall_cache)
{
struct value *val;
val = dwarf2_tailcall_prev_register_first (this_frame,
&cache->tailcall_cache,
regnum);
if (val)
return val;
}
switch (cache->reg[regnum].how)
{
case DWARF2_FRAME_REG_UNDEFINED:
/* If CFI explicitly specified that the value isn't defined,
mark it as optimized away; the value isn't available. */
return frame_unwind_got_optimized (this_frame, regnum);
case DWARF2_FRAME_REG_SAVED_OFFSET:
addr = cache->cfa + cache->reg[regnum].loc.offset;
return frame_unwind_got_memory (this_frame, regnum, addr);
case DWARF2_FRAME_REG_SAVED_REG:
realnum
= gdbarch_dwarf2_reg_to_regnum (gdbarch, cache->reg[regnum].loc.reg);
return frame_unwind_got_register (this_frame, regnum, realnum);
case DWARF2_FRAME_REG_SAVED_EXP:
addr = execute_stack_op (cache->reg[regnum].loc.exp,
cache->reg[regnum].exp_len,
cache->addr_size, cache->text_offset,
this_frame, cache->cfa, 1);
return frame_unwind_got_memory (this_frame, regnum, addr);
case DWARF2_FRAME_REG_SAVED_VAL_OFFSET:
addr = cache->cfa + cache->reg[regnum].loc.offset;
return frame_unwind_got_constant (this_frame, regnum, addr);
case DWARF2_FRAME_REG_SAVED_VAL_EXP:
addr = execute_stack_op (cache->reg[regnum].loc.exp,
cache->reg[regnum].exp_len,
cache->addr_size, cache->text_offset,
this_frame, cache->cfa, 1);
return frame_unwind_got_constant (this_frame, regnum, addr);
case DWARF2_FRAME_REG_UNSPECIFIED:
/* GCC, in its infinite wisdom decided to not provide unwind
information for registers that are "same value". Since
DWARF2 (3 draft 7) doesn't define such behavior, said
registers are actually undefined (which is different to CFI
"undefined"). Code above issues a complaint about this.
Here just fudge the books, assume GCC, and that the value is
more inner on the stack. */
return frame_unwind_got_register (this_frame, regnum, regnum);
case DWARF2_FRAME_REG_SAME_VALUE:
return frame_unwind_got_register (this_frame, regnum, regnum);
case DWARF2_FRAME_REG_CFA:
return frame_unwind_got_address (this_frame, regnum, cache->cfa);
case DWARF2_FRAME_REG_CFA_OFFSET:
addr = cache->cfa + cache->reg[regnum].loc.offset;
return frame_unwind_got_address (this_frame, regnum, addr);
case DWARF2_FRAME_REG_RA_OFFSET:
addr = cache->reg[regnum].loc.offset;
regnum = gdbarch_dwarf2_reg_to_regnum
(gdbarch, cache->retaddr_reg.loc.reg);
addr += get_frame_register_unsigned (this_frame, regnum);
return frame_unwind_got_address (this_frame, regnum, addr);
case DWARF2_FRAME_REG_FN:
return cache->reg[regnum].loc.fn (this_frame, this_cache, regnum);
default:
internal_error (__FILE__, __LINE__, _("Unknown register rule."));
}
}
/* Proxy for tailcall_frame_dealloc_cache for bottom frame of a virtual tail
call frames chain. */
static void
dwarf2_frame_dealloc_cache (struct frame_info *self, void *this_cache)
{
struct dwarf2_frame_cache *cache = dwarf2_frame_cache (self, &this_cache);
if (cache->tailcall_cache)
dwarf2_tailcall_frame_unwind.dealloc_cache (self, cache->tailcall_cache);
}
static int
dwarf2_frame_sniffer (const struct frame_unwind *self,
struct frame_info *this_frame, void **this_cache)
{
/* Grab an address that is guarenteed to reside somewhere within the
function. get_frame_pc(), with a no-return next function, can
end up returning something past the end of this function's body.
If the frame we're sniffing for is a signal frame whose start
address is placed on the stack by the OS, its FDE must
extend one byte before its start address or we could potentially
select the FDE of the previous function. */
CORE_ADDR block_addr = get_frame_address_in_block (this_frame);
struct dwarf2_fde *fde = dwarf2_frame_find_fde (&block_addr, NULL);
if (!fde)
return 0;
/* On some targets, signal trampolines may have unwind information.
We need to recognize them so that we set the frame type
correctly. */
if (fde->cie->signal_frame
|| dwarf2_frame_signal_frame_p (get_frame_arch (this_frame),
this_frame))
return self->type == SIGTRAMP_FRAME;
if (self->type != NORMAL_FRAME)
return 0;
return 1;
}
static const struct frame_unwind dwarf2_frame_unwind =
{
NORMAL_FRAME,
dwarf2_frame_unwind_stop_reason,
dwarf2_frame_this_id,
dwarf2_frame_prev_register,
NULL,
dwarf2_frame_sniffer,
dwarf2_frame_dealloc_cache
};
static const struct frame_unwind dwarf2_signal_frame_unwind =
{
SIGTRAMP_FRAME,
dwarf2_frame_unwind_stop_reason,
dwarf2_frame_this_id,
dwarf2_frame_prev_register,
NULL,
dwarf2_frame_sniffer,
/* TAILCALL_CACHE can never be in such frame to need dealloc_cache. */
NULL
};
/* Append the DWARF-2 frame unwinders to GDBARCH's list. */
void
dwarf2_append_unwinders (struct gdbarch *gdbarch)
{
/* TAILCALL_FRAME must be first to find the record by
dwarf2_tailcall_sniffer_first. */
frame_unwind_append_unwinder (gdbarch, &dwarf2_tailcall_frame_unwind);
frame_unwind_append_unwinder (gdbarch, &dwarf2_frame_unwind);
frame_unwind_append_unwinder (gdbarch, &dwarf2_signal_frame_unwind);
}
/* There is no explicitly defined relationship between the CFA and the
location of frame's local variables and arguments/parameters.
Therefore, frame base methods on this page should probably only be
used as a last resort, just to avoid printing total garbage as a
response to the "info frame" command. */
static CORE_ADDR
dwarf2_frame_base_address (struct frame_info *this_frame, void **this_cache)
{
struct dwarf2_frame_cache *cache =
dwarf2_frame_cache (this_frame, this_cache);
return cache->cfa;
}
static const struct frame_base dwarf2_frame_base =
{
&dwarf2_frame_unwind,
dwarf2_frame_base_address,
dwarf2_frame_base_address,
dwarf2_frame_base_address
};
const struct frame_base *
dwarf2_frame_base_sniffer (struct frame_info *this_frame)
{
CORE_ADDR block_addr = get_frame_address_in_block (this_frame);
if (dwarf2_frame_find_fde (&block_addr, NULL))
return &dwarf2_frame_base;
return NULL;
}
/* Compute the CFA for THIS_FRAME, but only if THIS_FRAME came from
the DWARF unwinder. This is used to implement
DW_OP_call_frame_cfa. */
CORE_ADDR
dwarf2_frame_cfa (struct frame_info *this_frame)
{
if (frame_unwinder_is (this_frame, &record_btrace_tailcall_frame_unwind)
|| frame_unwinder_is (this_frame, &record_btrace_frame_unwind))
throw_error (NOT_AVAILABLE_ERROR,
_("cfa not available for record btrace target"));
while (get_frame_type (this_frame) == INLINE_FRAME)
this_frame = get_prev_frame (this_frame);
if (get_frame_unwind_stop_reason (this_frame) == UNWIND_UNAVAILABLE)
throw_error (NOT_AVAILABLE_ERROR,
_("can't compute CFA for this frame: "
"required registers or memory are unavailable"));
/* This restriction could be lifted if other unwinders are known to
compute the frame base in a way compatible with the DWARF
unwinder. */
if (!frame_unwinder_is (this_frame, &dwarf2_frame_unwind)
&& !frame_unwinder_is (this_frame, &dwarf2_tailcall_frame_unwind))
error (_("can't compute CFA for this frame"));
return get_frame_base (this_frame);
}
const struct objfile_data *dwarf2_frame_objfile_data;
static unsigned int
read_1_byte (bfd *abfd, const gdb_byte *buf)
{
return bfd_get_8 (abfd, buf);
}
static unsigned int
read_4_bytes (bfd *abfd, const gdb_byte *buf)
{
return bfd_get_32 (abfd, buf);
}
static ULONGEST
read_8_bytes (bfd *abfd, const gdb_byte *buf)
{
return bfd_get_64 (abfd, buf);
}
static ULONGEST
read_initial_length (bfd *abfd, const gdb_byte *buf,
unsigned int *bytes_read_ptr)
{
LONGEST result;
result = bfd_get_32 (abfd, buf);
if (result == 0xffffffff)
{
result = bfd_get_64 (abfd, buf + 4);
*bytes_read_ptr = 12;
}
else
*bytes_read_ptr = 4;
return result;
}
/* Pointer encoding helper functions. */
/* GCC supports exception handling based on DWARF2 CFI. However, for
technical reasons, it encodes addresses in its FDE's in a different
way. Several "pointer encodings" are supported. The encoding
that's used for a particular FDE is determined by the 'R'
augmentation in the associated CIE. The argument of this
augmentation is a single byte.
The address can be encoded as 2 bytes, 4 bytes, 8 bytes, or as a
LEB128. This is encoded in bits 0, 1 and 2. Bit 3 encodes whether
the address is signed or unsigned. Bits 4, 5 and 6 encode how the
address should be interpreted (absolute, relative to the current
position in the FDE, ...). Bit 7, indicates that the address
should be dereferenced. */
static gdb_byte
encoding_for_size (unsigned int size)
{
switch (size)
{
case 2:
return DW_EH_PE_udata2;
case 4:
return DW_EH_PE_udata4;
case 8:
return DW_EH_PE_udata8;
default:
internal_error (__FILE__, __LINE__, _("Unsupported address size"));
}
}
static CORE_ADDR
read_encoded_value (struct comp_unit *unit, gdb_byte encoding,
int ptr_len, const gdb_byte *buf,
unsigned int *bytes_read_ptr,
CORE_ADDR func_base)
{
ptrdiff_t offset;
CORE_ADDR base;
/* GCC currently doesn't generate DW_EH_PE_indirect encodings for
FDE's. */
if (encoding & DW_EH_PE_indirect)
internal_error (__FILE__, __LINE__,
_("Unsupported encoding: DW_EH_PE_indirect"));
*bytes_read_ptr = 0;
switch (encoding & 0x70)
{
case DW_EH_PE_absptr:
base = 0;
break;
case DW_EH_PE_pcrel:
base = bfd_get_section_vma (unit->abfd, unit->dwarf_frame_section);
base += (buf - unit->dwarf_frame_buffer);
break;
case DW_EH_PE_datarel:
base = unit->dbase;
break;
case DW_EH_PE_textrel:
base = unit->tbase;
break;
case DW_EH_PE_funcrel:
base = func_base;
break;
case DW_EH_PE_aligned:
base = 0;
offset = buf - unit->dwarf_frame_buffer;
if ((offset % ptr_len) != 0)
{
*bytes_read_ptr = ptr_len - (offset % ptr_len);
buf += *bytes_read_ptr;
}
break;
default:
internal_error (__FILE__, __LINE__,
_("Invalid or unsupported encoding"));
}
if ((encoding & 0x07) == 0x00)
{
encoding |= encoding_for_size (ptr_len);
if (bfd_get_sign_extend_vma (unit->abfd))
encoding |= DW_EH_PE_signed;
}
switch (encoding & 0x0f)
{
case DW_EH_PE_uleb128:
{
uint64_t value;
const gdb_byte *end_buf = buf + (sizeof (value) + 1) * 8 / 7;
*bytes_read_ptr += safe_read_uleb128 (buf, end_buf, &value) - buf;
return base + value;
}
case DW_EH_PE_udata2:
*bytes_read_ptr += 2;
return (base + bfd_get_16 (unit->abfd, (bfd_byte *) buf));
case DW_EH_PE_udata4:
*bytes_read_ptr += 4;
return (base + bfd_get_32 (unit->abfd, (bfd_byte *) buf));
case DW_EH_PE_udata8:
*bytes_read_ptr += 8;
return (base + bfd_get_64 (unit->abfd, (bfd_byte *) buf));
case DW_EH_PE_sleb128:
{
int64_t value;
const gdb_byte *end_buf = buf + (sizeof (value) + 1) * 8 / 7;
*bytes_read_ptr += safe_read_sleb128 (buf, end_buf, &value) - buf;
return base + value;
}
case DW_EH_PE_sdata2:
*bytes_read_ptr += 2;
return (base + bfd_get_signed_16 (unit->abfd, (bfd_byte *) buf));
case DW_EH_PE_sdata4:
*bytes_read_ptr += 4;
return (base + bfd_get_signed_32 (unit->abfd, (bfd_byte *) buf));
case DW_EH_PE_sdata8:
*bytes_read_ptr += 8;
return (base + bfd_get_signed_64 (unit->abfd, (bfd_byte *) buf));
default:
internal_error (__FILE__, __LINE__,
_("Invalid or unsupported encoding"));
}
}
static int
bsearch_cie_cmp (const void *key, const void *element)
{
ULONGEST cie_pointer = *(ULONGEST *) key;
struct dwarf2_cie *cie = *(struct dwarf2_cie **) element;
if (cie_pointer == cie->cie_pointer)
return 0;
return (cie_pointer < cie->cie_pointer) ? -1 : 1;
}
/* Find CIE with the given CIE_POINTER in CIE_TABLE. */
static struct dwarf2_cie *
find_cie (struct dwarf2_cie_table *cie_table, ULONGEST cie_pointer)
{
struct dwarf2_cie **p_cie;
/* The C standard (ISO/IEC 9899:TC2) requires the BASE argument to
bsearch be non-NULL. */
if (cie_table->entries == NULL)
{
gdb_assert (cie_table->num_entries == 0);
return NULL;
}
p_cie = bsearch (&cie_pointer, cie_table->entries, cie_table->num_entries,
sizeof (cie_table->entries[0]), bsearch_cie_cmp);
if (p_cie != NULL)
return *p_cie;
return NULL;
}
/* Add a pointer to new CIE to the CIE_TABLE, allocating space for it. */
static void
add_cie (struct dwarf2_cie_table *cie_table, struct dwarf2_cie *cie)
{
const int n = cie_table->num_entries;
gdb_assert (n < 1
|| cie_table->entries[n - 1]->cie_pointer < cie->cie_pointer);
cie_table->entries =
xrealloc (cie_table->entries, (n + 1) * sizeof (cie_table->entries[0]));
cie_table->entries[n] = cie;
cie_table->num_entries = n + 1;
}
static int
bsearch_fde_cmp (const void *key, const void *element)
{
CORE_ADDR seek_pc = *(CORE_ADDR *) key;
struct dwarf2_fde *fde = *(struct dwarf2_fde **) element;
if (seek_pc < fde->initial_location)
return -1;
if (seek_pc < fde->initial_location + fde->address_range)
return 0;
return 1;
}
/* Find the FDE for *PC. Return a pointer to the FDE, and store the
inital location associated with it into *PC. */
static struct dwarf2_fde *
dwarf2_frame_find_fde (CORE_ADDR *pc, CORE_ADDR *out_offset)
{
struct objfile *objfile;
ALL_OBJFILES (objfile)
{
struct dwarf2_fde_table *fde_table;
struct dwarf2_fde **p_fde;
CORE_ADDR offset;
CORE_ADDR seek_pc;
fde_table = objfile_data (objfile, dwarf2_frame_objfile_data);
if (fde_table == NULL)
{
dwarf2_build_frame_info (objfile);
fde_table = objfile_data (objfile, dwarf2_frame_objfile_data);
}
gdb_assert (fde_table != NULL);
if (fde_table->num_entries == 0)
continue;
gdb_assert (objfile->section_offsets);
offset = ANOFFSET (objfile->section_offsets, SECT_OFF_TEXT (objfile));
gdb_assert (fde_table->num_entries > 0);
if (*pc < offset + fde_table->entries[0]->initial_location)
continue;
seek_pc = *pc - offset;
p_fde = bsearch (&seek_pc, fde_table->entries, fde_table->num_entries,
sizeof (fde_table->entries[0]), bsearch_fde_cmp);
if (p_fde != NULL)
{
*pc = (*p_fde)->initial_location + offset;
if (out_offset)
*out_offset = offset;
return *p_fde;
}
}
return NULL;
}
/* Add a pointer to new FDE to the FDE_TABLE, allocating space for it. */
static void
add_fde (struct dwarf2_fde_table *fde_table, struct dwarf2_fde *fde)
{
if (fde->address_range == 0)
/* Discard useless FDEs. */
return;
fde_table->num_entries += 1;
fde_table->entries =
xrealloc (fde_table->entries,
fde_table->num_entries * sizeof (fde_table->entries[0]));
fde_table->entries[fde_table->num_entries - 1] = fde;
}
#define DW64_CIE_ID 0xffffffffffffffffULL
/* Defines the type of eh_frames that are expected to be decoded: CIE, FDE
or any of them. */
enum eh_frame_type
{
EH_CIE_TYPE_ID = 1 << 0,
EH_FDE_TYPE_ID = 1 << 1,
EH_CIE_OR_FDE_TYPE_ID = EH_CIE_TYPE_ID | EH_FDE_TYPE_ID
};
static const gdb_byte *decode_frame_entry (struct comp_unit *unit,
const gdb_byte *start,
int eh_frame_p,
struct dwarf2_cie_table *cie_table,
struct dwarf2_fde_table *fde_table,
enum eh_frame_type entry_type);
/* Decode the next CIE or FDE, entry_type specifies the expected type.
Return NULL if invalid input, otherwise the next byte to be processed. */
static const gdb_byte *
decode_frame_entry_1 (struct comp_unit *unit, const gdb_byte *start,
int eh_frame_p,
struct dwarf2_cie_table *cie_table,
struct dwarf2_fde_table *fde_table,
enum eh_frame_type entry_type)
{
struct gdbarch *gdbarch = get_objfile_arch (unit->objfile);
const gdb_byte *buf, *end;
LONGEST length;
unsigned int bytes_read;
int dwarf64_p;
ULONGEST cie_id;
ULONGEST cie_pointer;
int64_t sleb128;
uint64_t uleb128;
buf = start;
length = read_initial_length (unit->abfd, buf, &bytes_read);
buf += bytes_read;
end = buf + length;
/* Are we still within the section? */
if (end > unit->dwarf_frame_buffer + unit->dwarf_frame_size)
return NULL;
if (length == 0)
return end;
/* Distinguish between 32 and 64-bit encoded frame info. */
dwarf64_p = (bytes_read == 12);
/* In a .eh_frame section, zero is used to distinguish CIEs from FDEs. */
if (eh_frame_p)
cie_id = 0;
else if (dwarf64_p)
cie_id = DW64_CIE_ID;
else
cie_id = DW_CIE_ID;
if (dwarf64_p)
{
cie_pointer = read_8_bytes (unit->abfd, buf);
buf += 8;
}
else
{
cie_pointer = read_4_bytes (unit->abfd, buf);
buf += 4;
}
if (cie_pointer == cie_id)
{
/* This is a CIE. */
struct dwarf2_cie *cie;
char *augmentation;
unsigned int cie_version;
/* Check that a CIE was expected. */
if ((entry_type & EH_CIE_TYPE_ID) == 0)
error (_("Found a CIE when not expecting it."));
/* Record the offset into the .debug_frame section of this CIE. */
cie_pointer = start - unit->dwarf_frame_buffer;
/* Check whether we've already read it. */
if (find_cie (cie_table, cie_pointer))
return end;
cie = (struct dwarf2_cie *)
obstack_alloc (&unit->objfile->objfile_obstack,
sizeof (struct dwarf2_cie));
cie->initial_instructions = NULL;
cie->cie_pointer = cie_pointer;
/* The encoding for FDE's in a normal .debug_frame section
depends on the target address size. */
cie->encoding = DW_EH_PE_absptr;
/* We'll determine the final value later, but we need to
initialize it conservatively. */
cie->signal_frame = 0;
/* Check version number. */
cie_version = read_1_byte (unit->abfd, buf);
if (cie_version != 1 && cie_version != 3 && cie_version != 4)
return NULL;
cie->version = cie_version;
buf += 1;
/* Interpret the interesting bits of the augmentation. */
cie->augmentation = augmentation = (char *) buf;
buf += (strlen (augmentation) + 1);
/* Ignore armcc augmentations. We only use them for quirks,
and that doesn't happen until later. */
if (strncmp (augmentation, "armcc", 5) == 0)
augmentation += strlen (augmentation);
/* The GCC 2.x "eh" augmentation has a pointer immediately
following the augmentation string, so it must be handled
first. */
if (augmentation[0] == 'e' && augmentation[1] == 'h')
{
/* Skip. */
buf += gdbarch_ptr_bit (gdbarch) / TARGET_CHAR_BIT;
augmentation += 2;
}
if (cie->version >= 4)
{
/* FIXME: check that this is the same as from the CU header. */
cie->addr_size = read_1_byte (unit->abfd, buf);
++buf;
cie->segment_size = read_1_byte (unit->abfd, buf);
++buf;
}
else
{
cie->addr_size = gdbarch_dwarf2_addr_size (gdbarch);
cie->segment_size = 0;
}
/* Address values in .eh_frame sections are defined to have the
target's pointer size. Watchout: This breaks frame info for
targets with pointer size < address size, unless a .debug_frame
section exists as well. */
if (eh_frame_p)
cie->ptr_size = gdbarch_ptr_bit (gdbarch) / TARGET_CHAR_BIT;
else
cie->ptr_size = cie->addr_size;
buf = gdb_read_uleb128 (buf, end, &uleb128);
if (buf == NULL)
return NULL;
cie->code_alignment_factor = uleb128;
buf = gdb_read_sleb128 (buf, end, &sleb128);
if (buf == NULL)
return NULL;
cie->data_alignment_factor = sleb128;
if (cie_version == 1)
{
cie->return_address_register = read_1_byte (unit->abfd, buf);
++buf;
}
else
{
buf = gdb_read_uleb128 (buf, end, &uleb128);
if (buf == NULL)
return NULL;
cie->return_address_register = uleb128;
}
cie->return_address_register
= dwarf2_frame_adjust_regnum (gdbarch,
cie->return_address_register,
eh_frame_p);
cie->saw_z_augmentation = (*augmentation == 'z');
if (cie->saw_z_augmentation)
{
uint64_t length;
buf = gdb_read_uleb128 (buf, end, &length);
if (buf == NULL)
return NULL;
cie->initial_instructions = buf + length;
augmentation++;
}
while (*augmentation)
{
/* "L" indicates a byte showing how the LSDA pointer is encoded. */
if (*augmentation == 'L')
{
/* Skip. */
buf++;
augmentation++;
}
/* "R" indicates a byte indicating how FDE addresses are encoded. */
else if (*augmentation == 'R')
{
cie->encoding = *buf++;
augmentation++;
}
/* "P" indicates a personality routine in the CIE augmentation. */
else if (*augmentation == 'P')
{
/* Skip. Avoid indirection since we throw away the result. */
gdb_byte encoding = (*buf++) & ~DW_EH_PE_indirect;
read_encoded_value (unit, encoding, cie->ptr_size,
buf, &bytes_read, 0);
buf += bytes_read;
augmentation++;
}
/* "S" indicates a signal frame, such that the return
address must not be decremented to locate the call frame
info for the previous frame; it might even be the first
instruction of a function, so decrementing it would take
us to a different function. */
else if (*augmentation == 'S')
{
cie->signal_frame = 1;
augmentation++;
}
/* Otherwise we have an unknown augmentation. Assume that either
there is no augmentation data, or we saw a 'z' prefix. */
else
{
if (cie->initial_instructions)
buf = cie->initial_instructions;
break;
}
}
cie->initial_instructions = buf;
cie->end = end;
cie->unit = unit;
add_cie (cie_table, cie);
}
else
{
/* This is a FDE. */
struct dwarf2_fde *fde;
CORE_ADDR addr;
/* Check that an FDE was expected. */
if ((entry_type & EH_FDE_TYPE_ID) == 0)
error (_("Found an FDE when not expecting it."));
/* In an .eh_frame section, the CIE pointer is the delta between the
address within the FDE where the CIE pointer is stored and the
address of the CIE. Convert it to an offset into the .eh_frame
section. */
if (eh_frame_p)
{
cie_pointer = buf - unit->dwarf_frame_buffer - cie_pointer;
cie_pointer -= (dwarf64_p ? 8 : 4);
}
/* In either case, validate the result is still within the section. */
if (cie_pointer >= unit->dwarf_frame_size)
return NULL;
fde = (struct dwarf2_fde *)
obstack_alloc (&unit->objfile->objfile_obstack,
sizeof (struct dwarf2_fde));
fde->cie = find_cie (cie_table, cie_pointer);
if (fde->cie == NULL)
{
decode_frame_entry (unit, unit->dwarf_frame_buffer + cie_pointer,
eh_frame_p, cie_table, fde_table,
EH_CIE_TYPE_ID);
fde->cie = find_cie (cie_table, cie_pointer);
}
gdb_assert (fde->cie != NULL);
addr = read_encoded_value (unit, fde->cie->encoding, fde->cie->ptr_size,
buf, &bytes_read, 0);
fde->initial_location = gdbarch_adjust_dwarf2_addr (gdbarch, addr);
buf += bytes_read;
fde->address_range =
read_encoded_value (unit, fde->cie->encoding & 0x0f,
fde->cie->ptr_size, buf, &bytes_read, 0);
addr = gdbarch_adjust_dwarf2_addr (gdbarch, addr + fde->address_range);
fde->address_range = addr - fde->initial_location;
buf += bytes_read;
/* A 'z' augmentation in the CIE implies the presence of an
augmentation field in the FDE as well. The only thing known
to be in here at present is the LSDA entry for EH. So we
can skip the whole thing. */
if (fde->cie->saw_z_augmentation)
{
uint64_t length;
buf = gdb_read_uleb128 (buf, end, &length);
if (buf == NULL)
return NULL;
buf += length;
if (buf > end)
return NULL;
}
fde->instructions = buf;
fde->end = end;
fde->eh_frame_p = eh_frame_p;
add_fde (fde_table, fde);
}
return end;
}
/* Read a CIE or FDE in BUF and decode it. Entry_type specifies whether we
expect an FDE or a CIE. */
static const gdb_byte *
decode_frame_entry (struct comp_unit *unit, const gdb_byte *start,
int eh_frame_p,
struct dwarf2_cie_table *cie_table,
struct dwarf2_fde_table *fde_table,
enum eh_frame_type entry_type)
{
enum { NONE, ALIGN4, ALIGN8, FAIL } workaround = NONE;
const gdb_byte *ret;
ptrdiff_t start_offset;
while (1)
{
ret = decode_frame_entry_1 (unit, start, eh_frame_p,
cie_table, fde_table, entry_type);
if (ret != NULL)
break;
/* We have corrupt input data of some form. */
/* ??? Try, weakly, to work around compiler/assembler/linker bugs
and mismatches wrt padding and alignment of debug sections. */
/* Note that there is no requirement in the standard for any
alignment at all in the frame unwind sections. Testing for
alignment before trying to interpret data would be incorrect.
However, GCC traditionally arranged for frame sections to be
sized such that the FDE length and CIE fields happen to be
aligned (in theory, for performance). This, unfortunately,
was done with .align directives, which had the side effect of
forcing the section to be aligned by the linker.
This becomes a problem when you have some other producer that
creates frame sections that are not as strictly aligned. That
produces a hole in the frame info that gets filled by the
linker with zeros.
The GCC behaviour is arguably a bug, but it's effectively now
part of the ABI, so we're now stuck with it, at least at the
object file level. A smart linker may decide, in the process
of compressing duplicate CIE information, that it can rewrite
the entire output section without this extra padding. */
start_offset = start - unit->dwarf_frame_buffer;
if (workaround < ALIGN4 && (start_offset & 3) != 0)
{
start += 4 - (start_offset & 3);
workaround = ALIGN4;
continue;
}
if (workaround < ALIGN8 && (start_offset & 7) != 0)
{
start += 8 - (start_offset & 7);
workaround = ALIGN8;
continue;
}
/* Nothing left to try. Arrange to return as if we've consumed
the entire input section. Hopefully we'll get valid info from
the other of .debug_frame/.eh_frame. */
workaround = FAIL;
ret = unit->dwarf_frame_buffer + unit->dwarf_frame_size;
break;
}
switch (workaround)
{
case NONE:
break;
case ALIGN4:
complaint (&symfile_complaints, _("\
Corrupt data in %s:%s; align 4 workaround apparently succeeded"),
unit->dwarf_frame_section->owner->filename,
unit->dwarf_frame_section->name);
break;
case ALIGN8:
complaint (&symfile_complaints, _("\
Corrupt data in %s:%s; align 8 workaround apparently succeeded"),
unit->dwarf_frame_section->owner->filename,
unit->dwarf_frame_section->name);
break;
default:
complaint (&symfile_complaints,
_("Corrupt data in %s:%s"),
unit->dwarf_frame_section->owner->filename,
unit->dwarf_frame_section->name);
break;
}
return ret;
}
static int
qsort_fde_cmp (const void *a, const void *b)
{
struct dwarf2_fde *aa = *(struct dwarf2_fde **)a;
struct dwarf2_fde *bb = *(struct dwarf2_fde **)b;
if (aa->initial_location == bb->initial_location)
{
if (aa->address_range != bb->address_range
&& aa->eh_frame_p == 0 && bb->eh_frame_p == 0)
/* Linker bug, e.g. gold/10400.
Work around it by keeping stable sort order. */
return (a < b) ? -1 : 1;
else
/* Put eh_frame entries after debug_frame ones. */
return aa->eh_frame_p - bb->eh_frame_p;
}
return (aa->initial_location < bb->initial_location) ? -1 : 1;
}
void
dwarf2_build_frame_info (struct objfile *objfile)
{
struct comp_unit *unit;
const gdb_byte *frame_ptr;
struct dwarf2_cie_table cie_table;
struct dwarf2_fde_table fde_table;
struct dwarf2_fde_table *fde_table2;
volatile struct gdb_exception e;
cie_table.num_entries = 0;
cie_table.entries = NULL;
fde_table.num_entries = 0;
fde_table.entries = NULL;
/* Build a minimal decoding of the DWARF2 compilation unit. */
unit = (struct comp_unit *) obstack_alloc (&objfile->objfile_obstack,
sizeof (struct comp_unit));
unit->abfd = objfile->obfd;
unit->objfile = objfile;
unit->dbase = 0;
unit->tbase = 0;
if (objfile->separate_debug_objfile_backlink == NULL)
{
/* Do not read .eh_frame from separate file as they must be also
present in the main file. */
dwarf2_get_section_info (objfile, DWARF2_EH_FRAME,
&unit->dwarf_frame_section,
&unit->dwarf_frame_buffer,
&unit->dwarf_frame_size);
if (unit->dwarf_frame_size)
{
asection *got, *txt;
/* FIXME: kettenis/20030602: This is the DW_EH_PE_datarel base
that is used for the i386/amd64 target, which currently is
the only target in GCC that supports/uses the
DW_EH_PE_datarel encoding. */
got = bfd_get_section_by_name (unit->abfd, ".got");
if (got)
unit->dbase = got->vma;
/* GCC emits the DW_EH_PE_textrel encoding type on sh and ia64
so far. */
txt = bfd_get_section_by_name (unit->abfd, ".text");
if (txt)
unit->tbase = txt->vma;
TRY_CATCH (e, RETURN_MASK_ERROR)
{
frame_ptr = unit->dwarf_frame_buffer;
while (frame_ptr < unit->dwarf_frame_buffer + unit->dwarf_frame_size)
frame_ptr = decode_frame_entry (unit, frame_ptr, 1,
&cie_table, &fde_table,
EH_CIE_OR_FDE_TYPE_ID);
}
if (e.reason < 0)
{
warning (_("skipping .eh_frame info of %s: %s"),
objfile_name (objfile), e.message);
if (fde_table.num_entries != 0)
{
xfree (fde_table.entries);
fde_table.entries = NULL;
fde_table.num_entries = 0;
}
/* The cie_table is discarded by the next if. */
}
if (cie_table.num_entries != 0)
{
/* Reinit cie_table: debug_frame has different CIEs. */
xfree (cie_table.entries);
cie_table.num_entries = 0;
cie_table.entries = NULL;
}
}
}
dwarf2_get_section_info (objfile, DWARF2_DEBUG_FRAME,
&unit->dwarf_frame_section,
&unit->dwarf_frame_buffer,
&unit->dwarf_frame_size);
if (unit->dwarf_frame_size)
{
int num_old_fde_entries = fde_table.num_entries;
TRY_CATCH (e, RETURN_MASK_ERROR)
{
frame_ptr = unit->dwarf_frame_buffer;
while (frame_ptr < unit->dwarf_frame_buffer + unit->dwarf_frame_size)
frame_ptr = decode_frame_entry (unit, frame_ptr, 0,
&cie_table, &fde_table,
EH_CIE_OR_FDE_TYPE_ID);
}
if (e.reason < 0)
{
warning (_("skipping .debug_frame info of %s: %s"),
objfile_name (objfile), e.message);
if (fde_table.num_entries != 0)
{
fde_table.num_entries = num_old_fde_entries;
if (num_old_fde_entries == 0)
{
xfree (fde_table.entries);
fde_table.entries = NULL;
}
else
{
fde_table.entries = xrealloc (fde_table.entries,
fde_table.num_entries *
sizeof (fde_table.entries[0]));
}
}
fde_table.num_entries = num_old_fde_entries;
/* The cie_table is discarded by the next if. */
}
}
/* Discard the cie_table, it is no longer needed. */
if (cie_table.num_entries != 0)
{
xfree (cie_table.entries);
cie_table.entries = NULL; /* Paranoia. */
cie_table.num_entries = 0; /* Paranoia. */
}
/* Copy fde_table to obstack: it is needed at runtime. */
fde_table2 = (struct dwarf2_fde_table *)
obstack_alloc (&objfile->objfile_obstack, sizeof (*fde_table2));
if (fde_table.num_entries == 0)
{
fde_table2->entries = NULL;
fde_table2->num_entries = 0;
}
else
{
struct dwarf2_fde *fde_prev = NULL;
struct dwarf2_fde *first_non_zero_fde = NULL;
int i;
/* Prepare FDE table for lookups. */
qsort (fde_table.entries, fde_table.num_entries,
sizeof (fde_table.entries[0]), qsort_fde_cmp);
/* Check for leftovers from --gc-sections. The GNU linker sets
the relevant symbols to zero, but doesn't zero the FDE *end*
ranges because there's no relocation there. It's (offset,
length), not (start, end). On targets where address zero is
just another valid address this can be a problem, since the
FDEs appear to be non-empty in the output --- we could pick
out the wrong FDE. To work around this, when overlaps are
detected, we prefer FDEs that do not start at zero.
Start by finding the first FDE with non-zero start. Below
we'll discard all FDEs that start at zero and overlap this
one. */
for (i = 0; i < fde_table.num_entries; i++)
{
struct dwarf2_fde *fde = fde_table.entries[i];
if (fde->initial_location != 0)
{
first_non_zero_fde = fde;
break;
}
}
/* Since we'll be doing bsearch, squeeze out identical (except
for eh_frame_p) fde entries so bsearch result is predictable.
Also discard leftovers from --gc-sections. */
fde_table2->num_entries = 0;
for (i = 0; i < fde_table.num_entries; i++)
{
struct dwarf2_fde *fde = fde_table.entries[i];
if (fde->initial_location == 0
&& first_non_zero_fde != NULL
&& (first_non_zero_fde->initial_location
< fde->initial_location + fde->address_range))
continue;
if (fde_prev != NULL
&& fde_prev->initial_location == fde->initial_location)
continue;
obstack_grow (&objfile->objfile_obstack, &fde_table.entries[i],
sizeof (fde_table.entries[0]));
++fde_table2->num_entries;
fde_prev = fde;
}
fde_table2->entries = obstack_finish (&objfile->objfile_obstack);
/* Discard the original fde_table. */
xfree (fde_table.entries);
}
set_objfile_data (objfile, dwarf2_frame_objfile_data, fde_table2);
}
/* Provide a prototype to silence -Wmissing-prototypes. */
void _initialize_dwarf2_frame (void);
void
_initialize_dwarf2_frame (void)
{
dwarf2_frame_data = gdbarch_data_register_pre_init (dwarf2_frame_init);
dwarf2_frame_objfile_data = register_objfile_data ();
}
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