perf symbols: skip livepatch symbols when loading kallsyms

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>

2 files changed, 14 insertions, 2 deletions

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index cd379ced19e5..a562702b4841 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -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;
 
 	/*
diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
index a71525335703..d0bac824c79c 100644
--- a/tools/perf/util/symbol.h
+++ b/tools/perf/util/symbol.h
@@ -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"
@@ -46,6 +48,16 @@ static inline bool is_ignored_kernel_symbol(const char *str)
 }
 
 /*
+ * 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:
  */