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perf symbols: skip livepatch symbols in kcore_copy kallsyms processing

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Livepatch symbols (.klp.sym.*) carry a [module] tag but resolve to core
kernel text addresses.  When kcore_copy__process_kallsyms() encounters
these symbols, they are treated as module symbols, pulling the
first_module_symbol down to a kernel text address.

This corrupts the module memory range used to build the kcore PT_LOAD
segments.  For example, with a kpatch module containing a
".klp.sym.vmlinux.arch_release_task_struct,0" livepatch symbol loaded:

  kernel symbols
    ...
    ffffffffb4a41120  arch_release_task_struct
    ...                 ^
    ...                 | aliased by .klp.sym
    ...                 | drags first_module_symbol here
                        |
    (43M gap)           | bloated kcore segment
                        |
  module symbols        |
    ffffffffc047b000  <-- correct first_module_symbol
    ...
    ...

This causes the module PT_LOAD segment to start at the .klp.sym address
and not the real first module address, bloating the kcore copy:

  Baseline (no livepatch):   VirtAddr ffffffffc047b000, 8.5M
  Bloated  (with livepatch): VirtAddr ffffffffb4a41000, 54M
  Post-fix (with livepatch): VirtAddr ffffffffc047b000, 8.9M

Filter livepatch symbols early in kcore_copy__process_kallsyms() before
they can affect module boundary tracking.

Reported-by: Sashiko <sashiko-bot@kernel.org>
Link: https://sashiko.dev/#/patchset/20260624201254.472576-1-joe.lawrence@redhat.com?part=1
Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
Acked-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
This commit is contained in:
Joe Lawrence 2026-06-26 17:21:40 -04:00 committed by Namhyung Kim
parent 5a9dd83589
commit 55caa65301
1 changed files with 4 additions and 0 deletions
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4
tools/perf/util/symbol-elf.c
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@ -2216,6 +2216,10 @@ static int kcore_copy__process_kallsyms(void *arg, const char *name, char type,
if (!kallsyms__is_function(type))
return 0;
/* Ignore livepatch symbols */
if (is_livepatch_symbol(name))
return 0;
if (strchr(name, '[')) {
if (!kci->first_module_symbol || start < kci->first_module_symbol)
kci->first_module_symbol = start;