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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>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.