Re: [PATCH v2 1/2] perf record: Add 8-byte aligned event type PERF_RECORD_COMPRESSED2

Arnaldo Carvalho de Melo
2025-03-17T15:52:09Z

On Fri, Mar 14, 2025 at 06:27:05PM -0700, Namhyung Kim wrote:
> Hello,
>
> On Mon, Mar 03, 2025 at 10:32:40AM -0800, Chun-Tse Shao wrote:
> > The original PERF_RECORD_COMPRESS is not 8-byte aligned, which can cause
> > asan runtime error:
> >
> > # Build with asan
> > $ make -C tools/perf O=/tmp/perf DEBUG=1 EXTRA_CFLAGS="-O0 -g -fno-omit-frame-pointer -fsanitize=undefined"
> > # Test success with many asan runtime errors:
> > $ /tmp/perf/perf test "Zstd perf.data compression/decompression" -vv
> > 83: Zstd perf.data compression/decompression:
> > ...
> > util/session.c:1959:13: runtime error: member access within misaligned address 0x7f69e3f99653 for type 'union perf_event', which requires 13 byte alignment
> > 0x7f69e3f99653: note: pointer points here
> > d0 3a 50 69 44 00 00 00 00 00 08 00 bb 07 00 00 00 00 00 00 44 00 00 00 00 00 00 00 ff 07 00 00
> > ^
> > util/session.c:2163:22: runtime error: member access within misaligned address 0x7f69e3f99653 for type 'union perf_event', which requires 8 byte alignment
> > 0x7f69e3f99653: note: pointer points here
> > d0 3a 50 69 44 00 00 00 00 00 08 00 bb 07 00 00 00 00 00 00 44 00 00 00 00 00 00 00 ff 07 00 00
> > ^
> > ...
> >
> > Since there is no way to align compressed data in zstd compression, this
> > patch add a new event type `PERF_RECORD_COMPRESSED2`, which adds a field
> > `data_size` to specify the actual compressed data size. The
> > `header.size` contains the total record size, including the padding at
> > the end to make it 8-byte aligned.
> >
> > Tested with `Zstd perf.data compression/decompression`
>
> Looks good to me.
>
> Arnaldo, are you ok with adding a new record type for this?

Checking the discussion and the patch.

- ARnaldo