From 4dc411ddbdcf28b88530da3a4377b85e22201dab Mon Sep 17 00:00:00 2001 From: Keno Fischer Date: Sun, 3 Jul 2016 19:08:33 -0400 Subject: [PATCH] perf_event_open.2: Add a note that dyn_size is omitted if size == 0 The perf_output_sample_ustack in kernel/events/core.c only writes a single 64 bit word if it can't dump the user registers. From the current version of the man page, I would have expected two 64 bit words (one for size, one for dyn_size). Change the man page to make this behavior explicit. Reviewed-by: Vince Weaver --- man2/perf_event_open.2 | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2 index 0e42c5007..67881546e 100644 --- a/man2/perf_event_open.2 +++ b/man2/perf_event_open.2 @@ -1994,7 +1994,7 @@ struct { /* if PERF_SAMPLE_REGS_USER */ u64 size; /* if PERF_SAMPLE_STACK_USER */ char data[size]; /* if PERF_SAMPLE_STACK_USER */ - u64 dyn_size; /* if PERF_SAMPLE_STACK_USER */ + u64 dyn_size; /* if PERF_SAMPLE_STACK_USER && size != 0 */ u64 weight; /* if PERF_SAMPLE_WEIGHT */ u64 data_src; /* if PERF_SAMPLE_DATA_SRC */ u64 transaction;/* if PERF_SAMPLE_TRANSACTION */ @@ -2185,6 +2185,11 @@ stack pointer at the time of sampling). .I dyn_size is the amount of data actually dumped (can be less than .IR size ). +Note that +.I dyn_size +is omitted if +.I size +is 0. .TP .I weight If