FreeChainXenon/binutils-gdb
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

[gdb/symtab] Fix zero address complaint for shlib

Browse source 
In PR28004 the following warning / Internal error is reported:
...
$ gdb -q -batch \
    -iex "set sysroot $(pwd -P)/repro" \
    ./repro/gdb \
    ./repro/core \
    -ex bt
  ...
 Program terminated with signal SIGABRT, Aborted.
 #0  0x00007ff8fe8e5d22 in raise () from repro/usr/lib/libc.so.6
 [Current thread is 1 (LWP 1762498)]
 #1  0x00007ff8fe8cf862 in abort () from repro/usr/lib/libc.so.6
 warning: (Internal error: pc 0x7ff8feb2c21d in read in psymtab, \
           but not in symtab.)
 warning: (Internal error: pc 0x7ff8feb2c218 in read in psymtab, \
           but not in symtab.)
  ...
 #2  0x00007ff8feb2c21e in __gnu_debug::_Error_formatter::_M_error() const \
   [clone .cold] (warning: (Internal error: pc 0x7ff8feb2c21d in read in \
   psymtab, but not in symtab.)

) from repro/usr/lib/libstdc++.so.6
...

The warning is about the following:
- in find_pc_sect_compunit_symtab we try to find the address
  (0x7ff8feb2c218 / 0x7ff8feb2c21d) in the symtabs.
- that fails, so we try again in the partial symtabs.
- we find a matching partial symtab
- however, the partial symtab has a full symtab, so
  we should have found a matching symtab in the first step.

The addresses are:
...
(gdb) info sym 0x7ff8feb2c218
__gnu_debug::_Error_formatter::_M_error() const [clone .cold] in \
  section .text of repro/usr/lib/libstdc++.so.6
(gdb) info sym 0x7ff8feb2c21d
__gnu_debug::_Error_formatter::_M_error() const [clone .cold] + 5 in \
  section .text of repro/usr/lib/libstdc++.so.6
...
which correspond to unrelocated addresses 0x9c218 and 0x9c21d:
...
$ nm -C  repro/usr/lib/libstdc++.so.6.0.29 | grep 000000000009c218
000000000009c218 t __gnu_debug::_Error_formatter::_M_error() const \
  [clone .cold]
...
which belong to function __gnu_debug::_Error_formatter::_M_error() in
/build/gcc/src/gcc/libstdc++-v3/src/c++11/debug.cc.

The partial symtab that is found for the addresses is instead the one for
/build/gcc/src/gcc/libstdc++-v3/src/c++98/bitmap_allocator.cc, which is
incorrect.

This happens as follows.

The bitmap_allocator.cc CU has DW_AT_ranges at .debug_rnglist offset 0x4b50:
...
    00004b50 0000000000000000 0000000000000056
    00004b5a 00000000000a4790 00000000000a479c
    00004b64 00000000000a47a0 00000000000a47ac
...

When reading the first range 0x0..0x56, it doesn't trigger the "start address
of zero" complaint here:
...
      /* A not-uncommon case of bad debug info.
         Don't pollute the addrmap with bad data.  */
      if (range_beginning + baseaddr == 0
          && !per_objfile->per_bfd->has_section_at_zero)
        {
          complaint (_(".debug_rnglists entry has start address of zero"
                       " [in module %s]"), objfile_name (objfile));
          continue;
        }
...
because baseaddr != 0, which seems incorrect given that when loading the
shared library individually in gdb (and consequently baseaddr == 0), we do see
the complaint.

Consequently, we run into this case in dwarf2_get_pc_bounds:
...
  if (low == 0 && !per_objfile->per_bfd->has_section_at_zero)
    return PC_BOUNDS_INVALID;
...
which then results in this code in process_psymtab_comp_unit_reader being
called with cu_bounds_kind == PC_BOUNDS_INVALID, which sets the set_addrmap
argument to 1:
...
      scan_partial_symbols (first_die, &lowpc, &highpc,
                            cu_bounds_kind <= PC_BOUNDS_INVALID, cu);
...
and consequently, the CU addrmap gets build using address info from the
functions.

During that process, addrmap_set_empty is called with a range that includes
0x9c218 and 0x9c21d:
...
(gdb) p /x start
$7 = 0x9989c
(gdb) p /x end_inclusive
$8 = 0xb200d
...
but it's called for a function at DIE 0x54153 with DW_AT_ranges at 0x40ae:
...
    000040ae 00000000000b1ee0 00000000000b200e
    000040b9 000000000009989c 00000000000998c4
    000040c3 <End of list>
...
and neither range includes 0x9c218 and 0x9c21d.

This is caused by this code in partial_die_info::read:
...
            if (dwarf2_ranges_read (ranges_offset, &lowpc, &highpc, cu,
                                    nullptr, tag))
             has_pc_info = 1;
...
which pretends that the function is located at addresses 0x9989c..0xb200d,
which is indeed not the case.

This patch fixes the first problem encountered: fix the "start address of
zero" complaint warning by removing the baseaddr part from the condition.
Same for dwarf2_ranges_process.

The effect is that:
- the complaint is triggered, and
- the warning / Internal error is no longer triggered.

This does not fix the observed problem in partial_die_info::read, which is
filed as PR28200.

Tested on x86_64-linux.

Co-Authored-By: Simon Marchi <simon.marchi@polymtl.ca>

gdb/ChangeLog:

2021-07-29  Simon Marchi  <simon.marchi@polymtl.ca>
	    Tom de Vries  <tdevries@suse.de>

	PR symtab/28004
	* gdb/dwarf2/read.c (dwarf2_rnglists_process, dwarf2_ranges_process):
	Fix zero address complaint.
	* gdb/testsuite/gdb.dwarf2/dw2-zero-range-shlib.c: New test.
	* gdb/testsuite/gdb.dwarf2/dw2-zero-range.c: New test.
	* gdb/testsuite/gdb.dwarf2/dw2-zero-range.exp: New file.
This commit is contained in:
Tom de Vries 2021-08-06 16:44:17 +02:00
parent 7fc8d4f48b
commit b9f3fbc9f3
4 changed files with 232 additions and 8 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

10
gdb/dwarf2/read.c
View file

@ -13631,7 +13631,6 @@ dwarf2_rnglists_process (unsigned offset, struct dwarf2_cu *cu,
/* Base address selection entry. */
gdb::optional<CORE_ADDR> base;
const gdb_byte *buffer;
CORE_ADDR baseaddr;
bool overflow = false;
ULONGEST addr_index;
struct dwarf2_section_info *rnglists_section;
@ -13648,8 +13647,6 @@ dwarf2_rnglists_process (unsigned offset, struct dwarf2_cu *cu,
}
buffer = rnglists_section->buffer + offset;
baseaddr = objfile->text_section_offset ();
while (1)
{
/* Initialize it due to a false compiler warning. */
@ -13791,7 +13788,7 @@ dwarf2_rnglists_process (unsigned offset, struct dwarf2_cu *cu,
/* A not-uncommon case of bad debug info.
Don't pollute the addrmap with bad data. */
if (range_beginning + baseaddr == 0
if (range_beginning == 0
&& !per_objfile->per_bfd->has_section_at_zero)
{
complaint (_(".debug_rnglists entry has start address of zero"
@ -13833,7 +13830,6 @@ dwarf2_ranges_process (unsigned offset, struct dwarf2_cu *cu, dwarf_tag tag,
gdb::optional<CORE_ADDR> base;
unsigned int dummy;
const gdb_byte *buffer;
CORE_ADDR baseaddr;
if (cu_header->version >= 5)
return dwarf2_rnglists_process (offset, cu, tag, callback);
@ -13849,8 +13845,6 @@ dwarf2_ranges_process (unsigned offset, struct dwarf2_cu *cu, dwarf_tag tag,
}
buffer = per_objfile->per_bfd->ranges.buffer + offset;
baseaddr = objfile->text_section_offset ();
while (1)
{
CORE_ADDR range_beginning, range_end;
@ -13901,7 +13895,7 @@ dwarf2_ranges_process (unsigned offset, struct dwarf2_cu *cu, dwarf_tag tag,
/* A not-uncommon case of bad debug info.
Don't pollute the addrmap with bad data. */
if (range_beginning + baseaddr == 0
if (range_beginning == 0
&& !per_objfile->per_bfd->has_section_at_zero)
{
complaint (_(".debug_ranges entry has start address of zero"

21
gdb/testsuite/gdb.dwarf2/dw2-zero-range-shlib.c Normal file
View file

@ -0,0 +1,21 @@
/*
Copyright 2021 Free Software Foundation, Inc.
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/>. */
void
foo (void)
{
asm ("foo_label: .globl foo_label");
}

24
gdb/testsuite/gdb.dwarf2/dw2-zero-range.c Normal file
View file

@ -0,0 +1,24 @@
/*
Copyright 2021 Free Software Foundation, Inc.
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/>. */
extern void foo (void);
int
main (void)
{
asm ("main_label: .globl main_label");
foo ();
}

185
gdb/testsuite/gdb.dwarf2/dw2-zero-range.exp Normal file
View file

@ -0,0 +1,185 @@
# Copyright 2021 Free Software Foundation, Inc.
# 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/>.
# Check that the ".debug_ranges entry has start address of zero" complaint
# is triggered for a loaded shared lib.
load_lib dwarf.exp
# This test can only be run on targets which support DWARF-2 and use gas.
if {![dwarf2_support]} {
verbose "Skipping $gdb_test_file_name."
return 0
}
if {[skip_shlib_tests]} {
return 0
}
standard_testfile .c -shlib.c -dw.S
# Test with both a .debug_ranges section (DWARF 4) and a .debug_rnglists
# section (DWARF 5).
foreach_with_prefix ranges_sect {ranges rnglists} {
set asm_file [standard_output_file ${ranges_sect}-$srcfile3]
if { $ranges_sect == "ranges" } {
Dwarf::assemble $asm_file {
global srcdir subdir srcfile2
declare_labels ranges_label
cu {} {
compile_unit {
{language @DW_LANG_C}
{name $srcfile2}
{ranges ${ranges_label} DW_FORM_sec_offset}
} {
subprogram {
{external 1 flag}
{name foo}
}
}
}
ranges {is_64 [is_64_target]} {
ranges_label: sequence {
base 0
range 0 1
}
}
}
} elseif { $ranges_sect == "rnglists" } {
Dwarf::assemble $asm_file {
global srcdir subdir srcfile2
declare_labels rnglists_label
cu {
version 5
} {
compile_unit {
{language @DW_LANG_C}
{name $srcfile2}
{ranges ${rnglists_label} DW_FORM_sec_offset}
} {
subprogram {
{external 1 flag}
{name foo}
}
}
}
rnglists {
table {
rnglists_label: list_ {
start_end 0 1
}
}
}
}
} else {
error "invalid ranges section kind"
}
set lib1 [standard_output_file shr1.sl]
set lib_opts "nodebug"
set sources [list ${srcdir}/${subdir}/$srcfile2 $asm_file]
if { [gdb_compile_shlib $sources ${lib1} $lib_opts] != "" } {
untested "failed to compile"
return -1
}
set exec_opts [list debug shlib=${lib1}]
set sources ${srcdir}/${subdir}/${srcfile}
if { [gdb_compile $sources ${binfile} executable \
$exec_opts] != ""} {
untested "failed to compile"
return -1
}
clean_restart $binfile
set readnow_p [readnow]
# Don't load the symbols for $lib1 during runto_main.
# Instead, we do this afterwards using "sharedlibrary $lib1".
gdb_test_no_output "set auto-solib-add off"
if { ![runto_main] } {
fail "cannot run to main."
return -1
}
set complaint_re ".debug_${ranges_sect} entry has start address of zero"
set re \
"During symbol reading: $complaint_re \\\[in module \[^\r\n\]*\\\]"
# Test for presence of complaint, with lib1 relocated.
with_complaints 1 {
set test "Zero address complaint - relocated - psymtab"
set have_complaint 0
gdb_test_multiple "sharedlibrary $lib1" $test {
-re -wrap $re {
set have_complaint 1
}
-re -wrap "" {
}
}
if { $have_complaint } {
pass $test
} else {
set index [have_index $lib1]
if { $index == "gdb_index" } {
kfail symtab/28159 $test
} else {
fail $test
}
}
}
if { ! $readnow_p } {
with_complaints 1 {
gdb_test "maint expand-symtabs $srcfile2" $re \
"Zero address complaint - relocated - symtab"
}
}
clean_restart
# Test for presence of complaint, with lib1 unrelocated.
with_complaints 1 {
gdb_load $lib1
set test "Zero address complaint - unrelocated - psymtab"
set have_complaint [regexp $re.* $gdb_file_cmd_msg]
if { $have_complaint } {
pass $test
} else {
set index [have_index $lib1]
if { $index == "gdb_index" } {
kfail symtab/28159 $test
} else {
fail $test
}
}
}
if { ! $readnow_p } {
with_complaints 1 {
gdb_test "maint expand-symtabs $srcfile2" $re \
"Zero address complaint - unrelocated - symtab"
}
}
}