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perf symbols: Handle 'u' and 'l' symbols in /proc/kallsyms

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I started seeing this in recent Fedora 42 kernels:

  # uname -a
  Linux number 6.14.3-300.fc42.x86_64 #1 SMP PREEMPT_DYNAMIC Sun Apr 20 16:08:39 UTC 2025 x86_64 GNU/Linux
  #

  # perf test vmlinux
    1: vmlinux symtab matches kallsyms                                 : FAILED!
  #

Where we have Rust enabled:

  # grep CONFIG_RUST /boot/config-6.14.3-300.fc42.x86_64
  CONFIG_RUSTC_VERSION=108600
  CONFIG_RUST_IS_AVAILABLE=y
  CONFIG_RUSTC_LLVM_VERSION=200101
  CONFIG_RUSTC_HAS_COERCE_POINTEE=y
  CONFIG_RUST=y
  CONFIG_RUSTC_VERSION_TEXT="rustc 1.86.0 (05f9846f8 2025-03-31) (Fedora 1.86.0-1.fc42)"
  CONFIG_RUST_FW_LOADER_ABSTRACTIONS=y
  CONFIG_RUST_PHYLIB_ABSTRACTIONS=y
  # CONFIG_RUST_DEBUG_ASSERTIONS is not set
  CONFIG_RUST_OVERFLOW_CHECKS=y
  # CONFIG_RUST_BUILD_ASSERT_ALLOW is not set
  #

Looking at the reason for the failure:

  # perf test -v vmlinux |& grep ^ERR
  ERR : 0xffffffff99efc7d0: __pfx__RNCINvNtNtNtCsf5tcb0XGUW4_4core4iter8adapters3map12map_try_foldjNtCsagR6JbSOIa9_12drm_panic_qr7VersionuINtNtNtBa_3ops12control_flow11ControlFlowB10_ENcB10_0NCINvNvNtNtNtB8_6traits8iterator8Iterator4find5checkB10_NCNvMB12_B10_13from_segments0E0E0B12_ not on kallsyms
  ERR : 0xffffffff99efc7e0: _RNCINvNtNtNtCsf5tcb0XGUW4_4core4iter8adapters3map12map_try_foldjNtCsagR6JbSOIa9_12drm_panic_qr7VersionuINtNtNtBa_3ops12control_flow11ControlFlowB10_ENcB10_0NCINvNvNtNtNtB8_6traits8iterator8Iterator4find5checkB10_NCNvMB12_B10_13from_segments0E0E0B12_ not on kallsyms
  #

But:

  # grep -w u /proc/kallsyms
  ffffffff99efc7d0 u __pfx__RNCINvNtNtNtCsf5tcb0XGUW4_4core4iter8adapters3map12map_try_foldjNtCsagR6JbSOIa9_12drm_panic_qr7VersionuINtNtNtBa_3ops12control_flow11ControlFlowB10_ENcB10_0NCINvNvNtNtNtB8_6traits8iterator8Iterator4find5checkB10_NCNvMB12_B10_13from_segments0E0E0B12_
  ffffffff99efc7e0 u _RNCINvNtNtNtCsf5tcb0XGUW4_4core4iter8adapters3map12map_try_foldjNtCsagR6JbSOIa9_12drm_panic_qr7VersionuINtNtNtBa_3ops12control_flow11ControlFlowB10_ENcB10_0NCINvNvNtNtNtB8_6traits8iterator8Iterator4find5checkB10_NCNvMB12_B10_13from_segments0E0E0B12_
  #

The test checks that "vmlinux symtab matches kallsyms", so it finds those two
symbols in vmlinux:

  # pahole --running_kernel_vmlinux
  /usr/lib/debug/lib/modules/6.14.3-300.fc42.x86_64/vmlinux
  #

  # readelf -sW /usr/lib/debug/lib/modules/6.14.3-300.fc42.x86_64/vmlinux | grep -Ew '(__pfx__RNCINvNtNtNtCsf5tcb0XGUW4_4core4iter8adapters3map12map_try_foldjNtCsagR6JbSOIa9_12drm_panic_qr7VersionuINtNtNtBa_3ops12control_flow11ControlFlowB10_ENcB10_0NCINvNvNtNtNtB8_6traits8iterator8Iterator4find5checkB10_NCNvMB12_B10_13from_segments0E0E0B12_|_RNCINvNtNtNtCsf5tcb0XGUW4_4core4iter8adapters3map12map_try_foldjNtCsagR6JbSOIa9_12drm_panic_qr7VersionuINtNtNtBa_3ops12control_flow11ControlFlowB10_ENcB10_0NCINvNvNtNtNtB8_6traits8iterator8Iterator4find5checkB10_NCNvMB12_B10_13from_segments0E0E0B12_)'
 81844: ffffffff81efc7e0   524 FUNC    LOCAL  DEFAULT    1 _RNCINvNtNtNtCsf5tcb0XGUW4_4core4iter8adapters3map12map_try_foldjNtCsagR6JbSOIa9_12drm_panic_qr7VersionuINtNtNtBa_3ops12control_flow11ControlFlowB10_ENcB10_0NCINvNvNtNtNtB8_6traits8iterator8Iterator4find5checkB10_NCNvMB12_B10_13from_segments0E0E0B12_
144259: ffffffff81efc7d0    16 FUNC    LOCAL  DEFAULT    1 __pfx__RNCINvNtNtNtCsf5tcb0XGUW4_4core4iter8adapters3map12map_try_foldjNtCsagR6JbSOIa9_12drm_panic_qr7VersionuINtNtNtBa_3ops12control_flow11ControlFlowB10_ENcB10_0NCINvNvNtNtNtB8_6traits8iterator8Iterator4find5checkB10_NCNvMB12_B10_13from_segments0E0E0B12_
  #

It is there.

From the nm documentation we can see that:

           "U" The symbol is undefined.

           "u" The symbol is a unique global symbol.  This is a GNU extension to the
	       standard set of ELF symbol bindings.  For such a symbol the dynamic
	       linker will make sure that in the entire process there is just one
	       symbol with this name and type in use.

So lets consider 'u' symbols in /proc/kallsyms when loading it to cover this case.

Fedora:40 shows this as a 'l' symbol, so consider that as well.

With this patch 'perf test 1' is happy again:

  # perf test vmlinux
    1: vmlinux symtab matches kallsyms                                 : Ok
  #

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: James Clark <james.clark@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/aBE_n0PGl3g6h-cS@x1
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Arnaldo Carvalho de Melo
2025-04-29 12:38:26 -03:00
parent 92b664dcef
commit 4d728bb93b
1 changed files with 5 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
tools/perf/util/symbol.c
View File

@@ -98,10 +98,12 @@ static enum dso_binary_type binary_type_symtab[] = {
#define DSO_BINARY_TYPE__SYMTAB_CNT ARRAY_SIZE(binary_type_symtab)
static bool symbol_type__filter(char symbol_type)
static bool symbol_type__filter(char __symbol_type)
{
symbol_type = toupper(symbol_type);
return symbol_type == 'T' || symbol_type == 'W' || symbol_type == 'D' || symbol_type == 'B';
// Since 'U' == undefined and 'u' == unique global symbol, we can't use toupper there
char symbol_type = toupper(__symbol_type);
return symbol_type == 'T' || symbol_type == 'W' || symbol_type == 'D' || symbol_type == 'B' ||
__symbol_type == 'u' || __symbol_type == 'l';
}
static int prefix_underscores_count(const char *str)