From: Adrian Hunter adrian.hunter@intel.com
commit c954eb72b31a9dc56c99b450253ec5b121add320 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: faaa87680b25d ("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 --- tools/perf/util/intel-pt.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
--- a/tools/perf/util/intel-pt.c +++ b/tools/perf/util/intel-pt.c @@ -707,8 +707,10 @@ static int intel_pt_walk_next_insn(struc
*ip += intel_pt_insn->length;
- if (to_ip && *ip == to_ip) + if (to_ip && *ip == to_ip) { + intel_pt_insn->length = 0; goto out_no_cache; + }
if (*ip >= al.map->end) break; @@ -1198,6 +1200,7 @@ static void intel_pt_set_pid_tid_cpu(str
static void intel_pt_sample_flags(struct intel_pt_queue *ptq) { + ptq->insn_len = 0; if (ptq->state->flags & INTEL_PT_ABORT_TX) { ptq->flags = PERF_IP_FLAG_BRANCH | PERF_IP_FLAG_TX_ABORT; } else if (ptq->state->flags & INTEL_PT_ASYNC) {