commit c954eb72b3 upstream.
The decoder reports the current instruction if it was decoded. In some
cases the current instruction is not decoded, in which case the instruction
bytes length must be set to zero. Ensure that is always done.
Note perf script can anyway get the instruction bytes for any samples where
they are not present.
Also note, that there is a redundant "ptq->insn_len = 0" statement which is
not removed until a subsequent patch in order to make this patch apply
cleanly to stable branches.
Example:
A machne that supports TSX is required. It will have flag "rtm". Kernel
parameter tsx=on may be required.
# for w in `cat /proc/cpuinfo | grep -m1 flags `;do echo $w | grep rtm ; done
rtm
Test program:
#include <stdio.h>
#include <immintrin.h>
int main()
{
int x = 0;
if (_xbegin() == _XBEGIN_STARTED) {
x = 1;
_xabort(1);
} else {
printf("x = %d\n", x);
}
return 0;
}
Compile with -mrtm i.e.
gcc -Wall -Wextra -mrtm xabort.c -o xabort
Record:
perf record -e intel_pt/cyc/u --filter 'filter main @ ./xabort' ./xabort
Before:
# perf script --itrace=xe -F+flags,+insn,-period --xed --ns
xabort 1478 [007] 92161.431348581: transactions: x 400b81 main+0x14 (/root/xabort) mov $0xffffffff, %eax
xabort 1478 [007] 92161.431348624: transactions: tx abrt 400b93 main+0x26 (/root/xabort) mov $0xffffffff, %eax
After:
# perf script --itrace=xe -F+flags,+insn,-period --xed --ns
xabort 1478 [007] 92161.431348581: transactions: x 400b81 main+0x14 (/root/xabort) xbegin 0x6
xabort 1478 [007] 92161.431348624: transactions: tx abrt 400b93 main+0x26 (/root/xabort) xabort $0x1
Fixes: faaa87680b ("perf intel-pt/bts: Report instruction bytes and length in sample")
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: stable@vger.kernel.org
Link: http://lore.kernel.org/lkml/20210519074515.9262-3-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
bc586be0ef