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authorTom Zanussi <tom.zanussi@linux.intel.com>2019-02-04 15:07:24 -0600
committerSteven Rostedt (VMware) <rostedt@goodmis.org>2019-03-05 08:47:46 -0500
commit9f0bbf3115ca9f91f43b7c74e9ac7d79f47fc6c2 (patch)
treebc91b05a3507119c615c73a47b7bcbaedb4b39a0 /kernel/trace
parented581aaf99be10883c8364df16bd80a7b8f72efc (diff)
downloadlinux-9f0bbf3115ca9f91f43b7c74e9ac7d79f47fc6c2.tar.bz2
tracing: Use strncpy instead of memcpy for string keys in hist triggers
Because there may be random garbage beyond a string's null terminator, it's not correct to copy the the complete character array for use as a hist trigger key. This results in multiple histogram entries for the 'same' string key. So, in the case of a string key, use strncpy instead of memcpy to avoid copying in the extra bytes. Before, using the gdbus entries in the following hist trigger as an example: # echo 'hist:key=comm' > /sys/kernel/debug/tracing/events/sched/sched_waking/trigger # cat /sys/kernel/debug/tracing/events/sched/sched_waking/hist ... { comm: ImgDecoder #4 } hitcount: 203 { comm: gmain } hitcount: 213 { comm: gmain } hitcount: 216 { comm: StreamTrans #73 } hitcount: 221 { comm: mozStorage #3 } hitcount: 230 { comm: gdbus } hitcount: 233 { comm: StyleThread#5 } hitcount: 253 { comm: gdbus } hitcount: 256 { comm: gdbus } hitcount: 260 { comm: StyleThread#4 } hitcount: 271 ... # cat /sys/kernel/debug/tracing/events/sched/sched_waking/hist | egrep gdbus | wc -l 51 After: # cat /sys/kernel/debug/tracing/events/sched/sched_waking/hist | egrep gdbus | wc -l 1 Link: http://lkml.kernel.org/r/50c35ae1267d64eee975b8125e151e600071d4dc.1549309756.git.tom.zanussi@linux.intel.com Cc: Namhyung Kim <namhyung@kernel.org> Cc: stable@vger.kernel.org Fixes: 79e577cbce4c4 ("tracing: Support string type key properly") Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace')
-rw-r--r--kernel/trace/trace_events_hist.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 5b03b9a869bb..c7774fa119a7 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -5157,9 +5157,10 @@ static inline void add_to_key(char *compound_key, void *key,
/* ensure NULL-termination */
if (size > key_field->size - 1)
size = key_field->size - 1;
- }
- memcpy(compound_key + key_field->offset, key, size);
+ strncpy(compound_key + key_field->offset, (char *)key, size);
+ } else
+ memcpy(compound_key + key_field->offset, key, size);
}
static void