[Bug other/82857] libbacktrace: please support binaries stripped with dwz -m (following the .gnu_debugaltlink)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82857 --- Comment #5 from Tom de Vries --- Created attachment 44962 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=44962=edit WIP patch, handles DW_FORM_GNU_strp_alt With this patch, the test-case from comment 1 passes: ... Non-stripped 1 Stripped 0 Stripped with debuglink 1 Stripped with debuglink to compressed with objcopy 1 Stripped with debuglink to compressed with dwz 1 Stripped with debuglink to compressed with dwz -m 1 ... In more detail, we get the backtrace with function name 'main', and the full path for bt.c: ... 0x400eff main /data/gcc_versions/devel/bt.c:20 0x7fe303fcaf49 __libc_start_main ../csu/libc-start.c:308 0x400da9 ??? ../sysdeps/x86_64/start.S:120 0x ??? ???:0 ...
[Bug other/82857] libbacktrace: please support binaries stripped with dwz -m (following the .gnu_debugaltlink)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82857 --- Comment #4 from Tom de Vries --- Created attachment 44957 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=44957=edit WIP patch, follows .gnu_debugaltlink
[Bug other/82857] libbacktrace: please support binaries stripped with dwz -m (following the .gnu_debugaltlink)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82857
--- Comment #3 from Tom de Vries ---
The dwz man shows:
...
-M NAME --multifile-name NAME
Specify the name of the common file that should be put into the
.gnu_debugaltlink section alongside
with its build ID. By default dwz puts there the argument of the
-m option.
...
The debugaltlink looks like:
...
$ objdump -s a.out.debug
Contents of section .gnu_debugaltlink:
636f6d6d 6f6e2e64 65627567 00583730 common.debug.X70
0010 8a56187b b2abdbbd 93929f3f f623059e .V.{...?.#..
0020 2f /
...
and given that this is the buildid of common.debug:
...
$ file common.debug
common.debug: ELF 64-bit LSB relocatable, x86-64, version 1 (SYSV),
BuildID[sha1]=5837308a56187bb2abdbbd93929f3ff623059e2f, with debug_info, not
stripped
...
indeed .gnu_debugaltlink looks like the zero-terminated "common.debug" string
followed by the buildid.
[Bug other/82857] libbacktrace: please support binaries stripped with dwz -m (following the .gnu_debugaltlink)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82857 Ian Lance Taylor changed: What|Removed |Added CC||ian at airs dot com --- Comment #2 from Ian Lance Taylor --- Are there any docs for the dwz -m format or for .gnu.debugaltlink?
[Bug other/82857] libbacktrace: please support binaries stripped with dwz -m (following the .gnu_debugaltlink)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82857
Tom de Vries changed:
What|Removed |Added
Status|UNCONFIRMED |NEW
Last reconfirmed||2018-11-01
CC||vries at gcc dot gnu.org
Ever confirmed|0 |1
--- Comment #1 from Tom de Vries ---
Test-case:
...
$ cat bt.c
#include "backtrace.h"
int
main (void)
{
struct backtrace_state *state = backtrace_create_state ("./a.out", 0, NULL,
NULL);
backtrace_print (state, 0, stderr);
return 0;
}
...
Test script:
...
$ cat test.sh
#!/bin/sh
###
rm -Rf a.out ./a.out.debug
###
src=bt.c
pwd=$(pwd -P)
gcc_src=$pwd/src
gcc_build=$pwd/build
CFLAGS="-I $gcc_src/libbacktrace"
LDFLAGS="-lbacktrace -L $gcc_build/libbacktrace/.libs/"
gcc $src -O0 -g $CFLAGS $LDFLAGS
###
echo "Non-stripped"
./a.out 2>&1 | grep -c /bt.c
###
cp a.out a.out.debug
strip --only-keep-debug a.out.debug
cp a.out.debug a.out.debug.saved
###
objcopy --strip-debug ./a.out
#strip a.out
echo "Stripped"
./a.out 2>&1 | grep -c /bt.c
###
objcopy --add-gnu-debuglink=a.out.debug ./a.out
echo "Stripped with debuglink"
./a.out 2>&1 | grep -c /bt.c
###
objcopy a.out.debug --compress-debug-sections=zlib
# We need to reset the debuglink, because the checksum has changed
objcopy -R .gnu_debuglink ./a.out
objcopy --add-gnu-debuglink=a.out.debug ./a.out
echo "Stripped with debuglink to compressed with objcopy"
./a.out 2>&1 | grep -c /bt.c
###
cp a.out.debug.saved a.out.debug
dwz a.out.debug
# We need to reset the debuglink, because the checksum has changed
objcopy -R .gnu_debuglink ./a.out
objcopy --add-gnu-debuglink=a.out.debug ./a.out
echo "Stripped with debuglink to compressed with dwz"
./a.out 2>&1 | grep -c /bt.c
###
cp a.out.debug.saved a.out.debug
cp a.out.debug.saved a.out.2.debug
dwz -m common.debug a.out.debug a.out.2.debug
# We need to reset the debuglink, because the checksum has changed
objcopy -R .gnu_debuglink ./a.out
objcopy --add-gnu-debuglink=a.out.debug ./a.out
echo "Stripped with debuglink to compressed with dwz -m"
./a.out 2>&1 | grep -c /bt.c
...
Test output:
...
$ ./test.sh
Non-stripped
1
Stripped
0
Stripped with debuglink
1
Stripped with debuglink to compressed with objcopy
1
Stripped with debuglink to compressed with dwz
1
Stripped with debuglink to compressed with dwz -m
0
...
Confirmed on master.
