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perf symbols: skip livepatch symbols when loading kallsyms

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Livepatch modules contain special symbols (prefixed by ".klp.sym.") that
act as relocation placeholders.  Once resolved, they point to the same
addresses as the original kernel symbols they reference. [1]

These special symbols confuse the 'vmlinux symtab matches kallsyms' perf
test as kallsyms may report multiple symbols sharing a single kernel
address.  For example:

  kallsyms (without livepatch)
  ----------------------------
  ffffffff81a41110 T __pfx_arch_release_task_struct
> ffffffff81a41120 T arch_release_task_struct
  ffffffff81a41140 T __pfx_exit_thread
  ffffffff81a41150 T exit_thread

  kallsyms (with livepatch loaded)
  ---------------------------------
  ffffffff81a41110 T __pfx_arch_release_task_struct
> ffffffff81a41120 T arch_release_task_struct
  ffffffff81a41140 T __pfx_exit_thread
  ffffffff81a41150 T exit_thread
> ffffffff81a41120 w .klp.sym.vmlinux.arch_release_task_struct,0  [kpatch_5_14_0_570_94_1_1_3]

When perf loads kallsyms, both symbols are inserted into the symbol
table at the same address, corrupting symbol end-address calculations
and causing test failures.

Filter out symbols prefixed with ".klp.sym." when loading kallsyms, as
they alias existing kernel symbols.

Link: https://docs.kernel.org/livepatch/module-elf-format.html#livepatch-symbols [1]
Reported-and-tested-by:
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 17:21:39 -04:00
committed by Namhyung Kim
parent e1065ed188
commit 5a9dd83589
2 changed files with 14 additions and 2 deletions
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4
tools/perf/util/symbol.c
View File

@@ -880,8 +880,8 @@ static int map__process_kallsym_symbol(void *arg, const char *name,
if (!symbol_type__filter(type))
return 0;
/* Ignore mapping symbols in kallsyms */
if (is_ignored_kernel_symbol(name))
/* Ignore mapping and livepatch symbols in kallsyms */
if (is_ignored_kernel_symbol(name) || is_livepatch_symbol(name))
return 0;
/*

12
tools/perf/util/symbol.h
View File

@@ -8,7 +8,9 @@
#include <stdint.h>
#include <stdatomic.h>
#include <linux/list.h>
#include <linux/livepatch_external.h>
#include <linux/rbtree.h>
#include <linux/string.h>
#include <stdio.h>
#include <errno.h>
#include "addr_location.h"
@@ -45,6 +47,16 @@ static inline bool is_ignored_kernel_symbol(const char *str)
return str[0] == '$';
}
/*
* Livepatch symbols (.klp.sym.*) are relocation placeholders whose resolved
* addresses alias existing kernel symbols. They carry a [module] tag which
* confuses module boundary tracking and symbol table lookups.
*/
static inline bool is_livepatch_symbol(const char *str)
{
return strstarts(str, KLP_SYM_PREFIX);
}
/*
* libelf 0.8.x and earlier do not support ELF_C_READ_MMAP;
* for newer versions we can use mmap to reduce memory usage: