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| author | Marco Elver <elver@google.com> | 2022-01-31 13:34:07 +0300 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2022-02-02 15:11:40 +0300 |
| commit | ddecd22878601a606d160680fa85802b75d92eb6 (patch) | |
| tree | e3e3e3e0d39ced09c898006b35437ad933c52fe8 /include | |
| parent | 95d29fa104523b1756323f7003294b1711c27808 (diff) | |
| download | linux-ddecd22878601a606d160680fa85802b75d92eb6.tar.xz | |
perf: uapi: Document perf_event_attr::sig_data truncation on 32 bit architectures
Due to the alignment requirements of siginfo_t, as described in
3ddb3fd8cdb0 ("signal, perf: Fix siginfo_t by avoiding u64 on 32-bit
architectures"), siginfo_t::si_perf_data is limited to an unsigned long.
However, perf_event_attr::sig_data is an u64, to avoid having to deal
with compat conversions. Due to being an u64, it may not immediately be
clear to users that sig_data is truncated on 32 bit architectures.
Add a comment to explicitly point this out, and hopefully help some
users save time by not having to deduce themselves what's happening.
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Link: https://lore.kernel.org/r/20220131103407.1971678-3-elver@google.com
Diffstat (limited to 'include')
| -rw-r--r-- | include/uapi/linux/perf_event.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h index 1b65042ab1db..82858b697c05 100644 --- a/include/uapi/linux/perf_event.h +++ b/include/uapi/linux/perf_event.h @@ -465,6 +465,8 @@ struct perf_event_attr { /* * User provided data if sigtrap=1, passed back to user via * siginfo_t::si_perf_data, e.g. to permit user to identify the event. + * Note, siginfo_t::si_perf_data is long-sized, and sig_data will be + * truncated accordingly on 32 bit architectures. */ __u64 sig_data; }; |