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()").
v1:
https://lore.kernel.org/linux-perf-users/[email protected]/T/#t
Joe Lawrence (2):
perf symbols: skip livepatch symbols when loading kallsyms
perf symbols: skip livepatch symbols in kcore_copy kallsyms processing
tools/perf/util/symbol-elf.c | 4 ++++
tools/perf/util/symbol.c | 4 ++--
tools/perf/util/symbol.h | 12 ++++++++++++
3 files changed, 18 insertions(+), 2 deletions(-)
--
2.54.0
