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Fix setting-breakpoints regression on PPC64 (function descriptors)

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The recent-ish commit e5f25bc5d6 ('Fix "list ambiguous_variable"')
caused a serious regression on PPC64.  See
<https://sourceware.org/ml/gdb-patches/2017-11/msg00666.html>.

Basically, after that patch, GDB sets breakpoints in function
descriptors instead of where the descriptors point to, which is
incorrect.

The problem is that GDB now only runs a minsym's address through
gdbarch_convert_from_func_ptr_addr if msymbol_is_text returns true.
However, if the symbol points to a function descriptor,
msymbol_is_text is false since function descriptors are in fact
outside the text section.

The fix is to also run a non-text address through
gdbarch_convert_from_func_ptr_addr, and if that detects that it was
indeed a function descriptor, treat the resulting address as a
function.

While implementing that directly in linespec.c:minsym_found (where the
bad msymbol_is_text check is) fixes the issue, I noticed that
linespec.c:add_minsym has some code that also basically needs to do
the same checks, however it's implemented differently.  Also,
add_minsym is calling find_pc_sect_line on non-function symbols, which
also doesn't look right.

So I introduced msymbol_is_function, so that we have a simple place to
consider minsyms and function descriptors.

And then, the only other use of msymbol_is_text is in
find_function_alias_target, which turns out to also be incorrect.
Changing that one to use msymbol_is_function, i.e., to consider
function descriptors too fixes (on PPC64):

  -FAIL: gdb.base/symbol-alias.exp: p func_alias
  -FAIL: gdb.base/symbol-alias.exp: p *func_alias()
  +PASS: gdb.base/symbol-alias.exp: p func_alias
  +PASS: gdb.base/symbol-alias.exp: p *func_alias()

And then after that, msymbol_is_text is no longer used anywhere, so it
can be removed.

Tested on x86_64 GNU/Linux, no regressions.  Tested on PPC64 GNU/Linux
and results compared to a testrun of e5f25bc5d6^ (before the
offending commit), also no regressions.  (there's a couple new FAILs
and some new symbol name matching unit tests are crashing, but that
looks unrelated).

gdb/ChangeLog:
2017-11-29  Pedro Alves  <palves@redhat.com>

	* linespec.c (minsym_found, add_minsym): Use msymbol_is_function.
	* minsyms.c (msymbol_is_text): Delete.
	(msymbol_is_function): New function.
	* minsyms.h (msymbol_is_text): Delete.
	(msymbol_is_function): New declaration.
	* symtab.c (find_function_alias_target): Use msymbol_is_function.
This commit is contained in:
Pedro Alves 2017-11-29 19:25:58 +00:00
parent 5dcf52c19f
commit 4024cf2b8d
5 changed files with 65 additions and 74 deletions
Download patch file Download diff file Expand all files Collapse all files

9
gdb/ChangeLog
View file

@ -1,3 +1,12 @@
2017-11-29 Pedro Alves <palves@redhat.com>
* linespec.c (minsym_found, add_minsym): Use msymbol_is_function.
* minsyms.c (msymbol_is_text): Delete.
(msymbol_is_function): New function.
* minsyms.h (msymbol_is_text): Delete.
(msymbol_is_function): New declaration.
* symtab.c (find_function_alias_target): Use msymbol_is_function.
2017-11-29 Tom Tromey <tom@tromey.com>
* Makefile.in (distclean): Handle the case where rmdir fails.

79
gdb/linespec.c
View file

@ -4309,22 +4309,12 @@ minsym_found (struct linespec_state *self, struct objfile *objfile,
struct minimal_symbol *msymbol,
std::vector<symtab_and_line> *result)
{
struct gdbarch *gdbarch = get_objfile_arch (objfile);
CORE_ADDR pc;
struct symtab_and_line sal;
if (msymbol_is_text (msymbol))
CORE_ADDR func_addr;
if (msymbol_is_function (objfile, msymbol, &func_addr))
{
sal = find_pc_sect_line (MSYMBOL_VALUE_ADDRESS (objfile, msymbol),
(struct obj_section *) 0, 0);
sal.section = MSYMBOL_OBJ_SECTION (objfile, msymbol);
/* The minimal symbol might point to a function descriptor;
resolve it to the actual code address instead. */
pc = gdbarch_convert_from_func_ptr_addr (gdbarch, sal.pc,
&current_target);
if (pc != sal.pc)
sal = find_pc_sect_line (pc, NULL, 0);
sal = find_pc_sect_line (func_addr, NULL, 0);
if (self->funfirstline)
{
@ -4332,14 +4322,9 @@ minsym_found (struct linespec_state *self, struct objfile *objfile,
&& (COMPUNIT_LOCATIONS_VALID (SYMTAB_COMPUNIT (sal.symtab))
|| SYMTAB_LANGUAGE (sal.symtab) == language_asm))
{
/* If gdbarch_convert_from_func_ptr_addr does not apply then
sal.SECTION, sal.LINE&co. will stay correct from above.
If gdbarch_convert_from_func_ptr_addr applies then
sal.SECTION is cleared from above and sal.LINE&co. will
stay correct from the last find_pc_sect_line above. */
sal.pc = MSYMBOL_VALUE_ADDRESS (objfile, msymbol);
sal.pc = gdbarch_convert_from_func_ptr_addr (gdbarch, sal.pc,
&current_target);
struct gdbarch *gdbarch = get_objfile_arch (objfile);
sal.pc = func_addr;
if (gdbarch_skip_entrypoint_p (gdbarch))
sal.pc = gdbarch_skip_entrypoint (gdbarch, sal.pc);
}
@ -4424,52 +4409,26 @@ static void
add_minsym (struct minimal_symbol *minsym, void *d)
{
struct collect_minsyms *info = (struct collect_minsyms *) d;
bound_minimal_symbol_d mo;
mo.minsym = minsym;
mo.objfile = info->objfile;
if (info->symtab != NULL)
{
CORE_ADDR pc;
struct symtab_and_line sal;
struct gdbarch *gdbarch = get_objfile_arch (info->objfile);
/* We're looking for a label for which we don't have debug
info. */
CORE_ADDR func_addr;
if (msymbol_is_function (info->objfile, minsym, &func_addr))
{
symtab_and_line sal = find_pc_sect_line (func_addr, NULL, 0);
sal = find_pc_sect_line (MSYMBOL_VALUE_ADDRESS (info->objfile, minsym),
NULL, 0);
sal.section = MSYMBOL_OBJ_SECTION (info->objfile, minsym);
pc
= gdbarch_convert_from_func_ptr_addr (gdbarch, sal.pc, &current_target);
if (pc != sal.pc)
sal = find_pc_sect_line (pc, NULL, 0);
if (info->symtab != sal.symtab)
return;
if (info->symtab != sal.symtab)
return;
}
}
/* Exclude data symbols when looking for breakpoint locations. */
if (!info->list_mode)
switch (minsym->type)
{
case mst_slot_got_plt:
case mst_data:
case mst_bss:
case mst_abs:
case mst_file_data:
case mst_file_bss:
{
/* Make sure this minsym is not a function descriptor
before we decide to discard it. */
struct gdbarch *gdbarch = get_objfile_arch (info->objfile);
CORE_ADDR addr = gdbarch_convert_from_func_ptr_addr
(gdbarch, BMSYMBOL_VALUE_ADDRESS (mo),
&current_target);
if (addr == BMSYMBOL_VALUE_ADDRESS (mo))
return;
}
}
/* Exclude data symbols when looking for breakpoint locations. */
if (!info->list_mode && !msymbol_is_function (info->objfile, minsym))
return;
bound_minimal_symbol_d mo = {minsym, info->objfile};
VEC_safe_push (bound_minimal_symbol_d, info->msyms, &mo);
}

34
gdb/minsyms.c
View file

@ -57,17 +57,35 @@
/* See minsyms.h. */
bool
msymbol_is_text (minimal_symbol *msymbol)
msymbol_is_function (struct objfile *objfile, minimal_symbol *minsym,
CORE_ADDR *func_address_p)
{
switch (MSYMBOL_TYPE (msymbol))
CORE_ADDR msym_addr = MSYMBOL_VALUE_ADDRESS (objfile, minsym);
switch (minsym->type)
{
case mst_text:
case mst_text_gnu_ifunc:
case mst_solib_trampoline:
case mst_file_text:
return true;
case mst_slot_got_plt:
case mst_data:
case mst_bss:
case mst_abs:
case mst_file_data:
case mst_file_bss:
{
struct gdbarch *gdbarch = get_objfile_arch (objfile);
CORE_ADDR pc = gdbarch_convert_from_func_ptr_addr (gdbarch, msym_addr,
&current_target);
if (pc != msym_addr)
{
if (func_address_p != NULL)
*func_address_p = pc;
return true;
}
return false;
}
default:
return false;
if (func_address_p != NULL)
*func_address_p = msym_addr;
return true;
}
}

9
gdb/minsyms.h
View file

@ -159,9 +159,14 @@ void terminate_minimal_symbol_table (struct objfile *objfile);
/* Return whether MSYMBOL is a function/method. */
/* Return whether MSYMBOL is a function/method. If FUNC_ADDRESS_P is
non-NULL, and the MSYMBOL is a function, then *FUNC_ADDRESS_P is
set to the function's address, already resolved if MINSYM points to
a function descriptor. */
bool msymbol_is_text (minimal_symbol *msymbol);
bool msymbol_is_function (struct objfile *objfile,
minimal_symbol *minsym,
CORE_ADDR *func_address_p = NULL);
/* Compute a hash code for the string argument. */

8
gdb/symtab.c
View file

@ -3927,14 +3927,14 @@ skip_prologue_using_sal (struct gdbarch *gdbarch, CORE_ADDR func_addr)
symbol *
find_function_alias_target (bound_minimal_symbol msymbol)
{
if (!msymbol_is_text (msymbol.minsym))
CORE_ADDR func_addr;
if (!msymbol_is_function (msymbol.objfile, msymbol.minsym, &func_addr))
return NULL;
CORE_ADDR addr = BMSYMBOL_VALUE_ADDRESS (msymbol);
symbol *sym = find_pc_function (addr);
symbol *sym = find_pc_function (func_addr);
if (sym != NULL
&& SYMBOL_CLASS (sym) == LOC_BLOCK
&& BLOCK_START (SYMBOL_BLOCK_VALUE (sym)) == addr)
&& BLOCK_START (SYMBOL_BLOCK_VALUE (sym)) == func_addr)
return sym;
return NULL;