[PATCH] perf report: Fix invalid memory accessing

[Wang Nan <wangnan0@huawei.com>]

Commit e1e499aba570a2ea84d29822b7ea637ac41d9a51 (perf tools: Add
processor socket info to hist_entry and addr_location) reads env->cpu
array for each sample using index al.cpu. However, al.cpu can be -1 if
sample doesn't select PERF_SAMPLE_CPU. Also, env->cpu can be invalid if
feature CPU_TOPOLOGY not selected. We should validate env->cpu and al.cpu
before setting al.socket.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
---

Although theoretically CPU_TOPOLOGY feature should always be selected by
'perf record', I did generate a perf.data without that feature. It has
header like this:

 # perf report -i ./bad.perf.data  --header-only          
 # ========
 # captured on: Thu Jan  8 09:30:15 2009
 # hostname : localhost
 # os release : 3.10.49-gd672fc4
 # perf version : 4.2.gc9df
 # arch : aarch64
 # nrcpus online : 8
 # nrcpus avail : 8
 # total memory : 1850768 kB
 # cmdline : /system/bin/perf record -e sync:sync_timeline -e kgsl:kgsl_register_event -g -a sleep 5 
 # event : name = sync:sync_timeline, , id = { 1107, 1108, 1109, 1110, 1111, 1112 }, type = 2, size = 112, config = 0x3e7, { sample_period, sample_freq } = 1, sample_type = IP|TID|TIME|CALLCHAIN|ID|CPU|PERIOD|RAW, read_format = ID, disabled = 1, inherit = 1, mmap = 1, comm = 1, task = 1, sample_id_all = 1, exclude_guest = 1, mmap2 = 1, comm_exec = 1
 # event : name = kgsl:kgsl_register_event, , id = { 1113, 1114, 1115, 1116, 1117, 1118 }, type = 2, size = 112, config = 0x350, { sample_period, sample_freq } = 1, sample_type = IP|TID|TIME|CALLCHAIN|ID|CPU|PERIOD|RAW, read_format = ID, disabled = 1, inherit = 1, sample_id_all = 1, exclude_guest = 1
 # pmu mappings: cpu = 4, software = 1, tracepoint = 2
 # ========
 #

It should be:

 # ========
 # captured on: Thu Jan  8 11:26:41 2009
 ...
 # HEADER_CPU_TOPOLOGY info available, use -I to display
 # pmu mappings: cpu = 4, software = 1, tracepoint = 2
 # ========

However, bad perf.data appears randomly. I can't stably reproduce it, so I
guess there might have another invalid memory accessing.

---
 tools/perf/builtin-report.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
index 4b43245..16d097d 100644
--- a/tools/perf/builtin-report.c
+++ b/tools/perf/builtin-report.c
@@ -158,8 +158,16 @@ static int process_sample_event(struct perf_tool *tool,
 		return -1;
 	}
 
-	/* read socket id from perf.data for perf report */
-	al.socket = env->cpu[al.cpu].socket_id;
+	/*
+	 * read socket id from perf.data for perf report
+	 * al.cpu is invalid if PERF_SAMPLE_CPU is not selected by this
+	 * sample.
+	 * env->cpu is invalid if CPU_TOPOLOGY feature is not set in
+	 * header.
+	 */
+	al.socket = -1;
+	if (env->cpu && al.cpu >= 0)
+		al.socket = env->cpu[al.cpu].socket_id;
 
 	if (rep->hide_unresolved && al.sym == NULL)
 		goto out_put;
-- 
1.8.3.4