From 2613f53750f32755d95c58fdd109830f8d8f6353 Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Thu, 7 Nov 2019 17:33:18 +0800 Subject: [PATCH] perf script brstackinsn: Fix recovery from LBR/binary mismatch [ 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 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 Cc: Jiri Olsa Link: http://lore.kernel.org/lkml/20190927233546.11533-1-andi@firstfloor.org Signed-off-by: Arnaldo Carvalho de Melo Signed-off-by: Sasha Levin Signed-off-by: Yang Yingliang --- 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 c770d226e504..e3e41d309c89 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) -- GitLab