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 <[email protected]>
Best Regards,
Petr
