From: Andi Kleen ak@linux.intel.com
[ Upstream commit e98df280bc2a499fd41d7f9e2d6733884de69902 ]
When the LBR data and the instructions in a binary do not match the loop printing instructions could get confused and print a long stream of bogus <bad> instructions.
The problem was that if the instruction decoder cannot decode an instruction it ilen wasn't initialized, so the loop going through the basic block would continue with the previous value.
Harden the code to avoid such problems:
- Make sure ilen is always freshly initialized and is 0 for bad instructions.
- Do not overrun the code buffer while printing instructions
- Print a warning message if the final jump is not on an instruction boundary.
Signed-off-by: Andi Kleen ak@linux.intel.com Cc: Jiri Olsa jolsa@kernel.org Link: http://lore.kernel.org/lkml/20190927233546.11533-1-andi@firstfloor.org Signed-off-by: Arnaldo Carvalho de Melo acme@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- tools/perf/builtin-script.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c index 53c11fc0855ee..d20f851796c52 100644 --- a/tools/perf/builtin-script.c +++ b/tools/perf/builtin-script.c @@ -1021,7 +1021,7 @@ static int perf_sample__fprintf_brstackinsn(struct perf_sample *sample, continue;
insn = 0; - for (off = 0;; off += ilen) { + for (off = 0; off < (unsigned)len; off += ilen) { uint64_t ip = start + off;
printed += ip__fprintf_sym(ip, thread, x.cpumode, x.cpu, &lastsym, attr, fp); @@ -1029,6 +1029,7 @@ static int perf_sample__fprintf_brstackinsn(struct perf_sample *sample, printed += ip__fprintf_jump(ip, &br->entries[i], &x, buffer + off, len - off, insn, fp); break; } else { + ilen = 0; printed += fprintf(fp, "\t%016" PRIx64 "\t%s\n", ip, dump_insn(&x, ip, buffer + off, len - off, &ilen)); if (ilen == 0) @@ -1036,6 +1037,8 @@ static int perf_sample__fprintf_brstackinsn(struct perf_sample *sample, insn++; } } + if (off != (unsigned)len) + printed += fprintf(fp, "\tmismatch of LBR data and executable\n"); }
/* @@ -1066,6 +1069,7 @@ static int perf_sample__fprintf_brstackinsn(struct perf_sample *sample, goto out; } for (off = 0; off <= end - start; off += ilen) { + ilen = 0; printed += fprintf(fp, "\t%016" PRIx64 "\t%s\n", start + off, dump_insn(&x, start + off, buffer + off, len - off, &ilen)); if (ilen == 0)