On 22/04/2021 07:44, Marco Elver wrote:

On some architectures, like Arm, the alignment of a structure is that of
its largest member.

This means that there is no portable way to add 64-bit integers to
siginfo_t on 32-bit architectures, because siginfo_t does not contain
any 64-bit integers on 32-bit architectures.

In the case of the si_perf field, word size is sufficient since there is
no exact requirement on size, given the data it contains is user-defined
via perf_event_attr::sig_data. On 32-bit architectures, any excess bits
of perf_event_attr::sig_data will therefore be truncated when copying
into si_perf.

Since this field is intended to disambiguate events (e.g. encoding
relevant information if there are more events of the same type), 32 bits
should provide enough entropy to do so on 32-bit architectures.

For 64-bit architectures, no change is intended.

Fixes: fb6cc127e0b6 ("signal: Introduce TRAP_PERF si_code and si_perf to siginfo")
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reported-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Marco Elver <elver@google.com>

Thanks for fixing!

Tested-by: Jon Hunter <jonathanh@nvidia.com>

Cheers
Jon

-- 
nvpublic

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