When strcmp-avx2.S is used as the default, elf/tst-valgrind-smoke fails
with
==1272761== Conditional jump or move depends on uninitialised value(s)
==1272761== at 0x4022C98: strcmp (strcmp-avx2.S:462)
==1272761== by 0x400B05B: _dl_name_match_p (dl-misc.c:75)
==1272761== by 0x40085F3: _dl_map_object (dl-load.c:1966)
==1272761== by 0x401AEA4: map_doit (rtld.c:644)
==1272761== by 0x4001488: _dl_catch_exception (dl-catch.c:237)
==1272761== by 0x40015AE: _dl_catch_error (dl-catch.c:256)
==1272761== by 0x401B38F: do_preload (rtld.c:816)
==1272761== by 0x401C116: handle_preload_list (rtld.c:892)
==1272761== by 0x401EDF5: dl_main (rtld.c:1842)
==1272761== by 0x401A79E: _dl_sysdep_start (dl-sysdep.c:140)
==1272761== by 0x401BEEE: _dl_start_final (rtld.c:494)
==1272761== by 0x401BEEE: _dl_start (rtld.c:581)
==1272761== by 0x401AD87: ??? (in */elf/ld.so)
The assembly codes are:
0x0000000004022c80 <+144>: vmovdqu 0x20(%rdi),%ymm0
0x0000000004022c85 <+149>: vpcmpeqb 0x20(%rsi),%ymm0,%ymm1
0x0000000004022c8a <+154>: vpcmpeqb %ymm0,%ymm15,%ymm2
0x0000000004022c8e <+158>: vpandn %ymm1,%ymm2,%ymm1
0x0000000004022c92 <+162>: vpmovmskb %ymm1,%ecx
0x0000000004022c96 <+166>: inc %ecx
=> 0x0000000004022c98 <+168>: jne 0x4022c32 <strcmp+66>
strcmp-avx2.S has 32-byte vector loads of strings which are shorter than
32 bytes:
(gdb) p (char *) ($rdi + 0x20)
$6 = 0x1ffeffea20 "memcheck-amd64-linux.so"
(gdb) p (char *) ($rsi + 0x20)
$7 = 0x4832640 "core-amd64-linux.so"
(gdb) call (int) strlen ((char *) ($rsi + 0x20))
$8 = 19
(gdb) call (int) strlen ((char *) ($rdi + 0x20))
$9 = 23
(gdb)
It triggers the valgrind error. The above code is safe since the loads
don't cross the page boundary. Update tst-valgrind-smoke.sh to accept
an optional suppression file and pass a suppression file to valgrind when
strcmp-avx2.S is the default implementation of strcmp.
Reviewed-by: Sunil K Pandey <skpgkp2@gmail.com>
Check if whether valgrind is available in the test environment.
If not, skip the test. Run smoke tests with valgrind to verify dynamic loader.
First, check if algrind works with the system ld.so in the test
environment. Then run the actual test inside the test environment,
using the just build ld.so and new libraries.
Co-authored-by: Mark Wielaard <mark@klomp.org>
