Re: [PATCH v2 0/2] perf symbols: skip livepatch symbols

[Petr Mladek <pmladek@suse.com>]

On Wed 2026-07-01 16:54:02, Namhyung Kim wrote:
> Hello,
> 
> On Fri, Jun 26, 2026 at 05:21:38PM -0400, Joe Lawrence wrote:
> > This patchset fixes two minor perf bugs when livepatches containing
> > special so-called livepatch symbols are loaded.  In both cases, perf
> > should ignore these symbols as they resolve as relocations to kernel
> > addresses and not module space.
> > 
> > - Patch 1 fixes `perf test 1`
> > - Patch 2 fixes `perf record --kcore` bloat
> > 
> > 
> > Testing notes
> > =============
> > 
> > ("perf symbols: skip livepatch symbols when loading kallsyms"):
> > 
> >   Without patch:
> >   ./tools/perf/perf test 1
> >     1: vmlinux symtab matches kallsyms                     : FAILED!
> > 
> >   With patch:
> >   ./tools/perf/perf test 1
> >     1: vmlinux symtab matches kallsyms                     : Ok
> > 
> > ("perf symbols: skip livepatch symbols in kcore_copy")
> > 
> >   1. Baseline = pre-patch perf, no livepatch
> >   ------------------------------------------
> >   
> >   $ ./tools/perf/perf record --kcore -a -o /tmp/baseline.data -- sleep 1
> >   [ perf record: Woken up 1 times to write data ]
> >   [ perf record: Captured and wrote 0.221 MB /tmp/baseline.data (1717 samples) ]
> >   
> >   $ tree --noreport -h /tmp/baseline.data
> >   /tmp/baseline.data
> >   |-- [ 235K]  data
> >   `-- [   50]  kcore_dir
> >       |-- [  11M]  kallsyms
> >       |-- [  25M]  kcore
> >       `-- [ 1.7K]  modules
> >   
> >   
> >   2. Bloated kcore = pre-patch perf, with livepatch
> >   -------------------------------------------------
> >   
> >   $ insmod kpatch-5_14_0-570_94_1-1-3.ko
> >   $ ./tools/perf/perf record --kcore -a -o /tmp/klp-bloated.data -- sleep 1
> >   [ perf record: Woken up 1 times to write data ]
> >   [ perf record: Captured and wrote 0.274 MB /tmp/klp-bloated.data (2757 samples) ]
> >   
> >   $ tree --noreport  -h /tmp/klp-bloated.data
> >   /tmp/klp-bloated.data
> >   |-- [ 288K]  data
> >   `-- [   50]  kcore_dir
> >       |-- [  11M]  kallsyms
> >       |-- [  68M]  kcore
> >       `-- [ 1.8K]  modules
> >   
> >   
> >   3. Post-fix = patched perf, with livepatch
> >   ------------------------------------------
> >   
> >   [ kpatch-5_14_0-570_94_1-1-3.ko still loaded from test (2) ]
> >   
> >   $ ./tools/perf/perf record --kcore -a -o /tmp/postfix.data -- sleep 1
> >   [ perf record: Woken up 1 times to write data ]
> >   [ perf record: Captured and wrote 0.274 MB /tmp/postfix.data (2763 samples) ]
> >   
> >   $ tree --noreport -h /tmp/postfix.data
> >   /tmp/postfix.data
> >   |-- [ 289K]  data
> >   `-- [   50]  kcore_dir
> >       |-- [  11M]  kallsyms
> >       |-- [  25M]  kcore
> >       `-- [ 1.8K]  modules
> > 
> > Changes
> > =======
> > 
> > v2:
> > - Move klp symbol check into tools/perf/util/symbol.h alongside similar
> >   is_ignored_kernel_symbol() check [Petr]
> > - Use KLP_SYM_PREFIX instead of inlining it [Petr]
> > - Add similar check to kcore_copy__process_kallsyms() [Sashiko]
> > 
> > - Note: Sashiko flagged a pre-existing off-by-one in kallsyms__parse()
> >   where the symbol-name loop could write past symbol_name[] on overlong
> >   entries. That issue is unrelated to livepatch symbols and was already
> >   fixed by Rui Qi's 68018df3f55e ("perf: Fix off-by-one stack buffer
> >   overflow in kallsyms__parse()").
> 
> Petr, are you ok with this change?

Yup, both changes look good to me. Feel free to use:

Acked-by: Petr Mladek <pmladek@suse.com>

Best Regards,
Petr