From 5febf432df1cfa5b25d99b54c32103fafbdd0eb9 Mon Sep 17 00:00:00 2001 From: Miguel Ojeda Date: Sun, 16 Aug 2026 15:32:33 +0200 Subject: kbuild: rust: keep Rust objects out of Clang LTO with inline helpers Under `CONFIG_LTO_CLANG` + `CONFIG_RUST_INLINE_HELPERS`, one may hit `objtool` errors such as: vmlinux.o: error: objtool: _R..._3Gsp4boot+0xd6a: can't find jump dest instruction at .text._R..._3Gsp4boot+0x1dfd The reason is that in such builds, the Clang invocation that compiles the combined Rust plus helpers bitcode emits LLVM bitcode (again) -- the final code generation happens in the linker's LTO step, which the `-mllvm` trap options passed to Clang do not reach. This, in turn, means that unreachable traps are missing, and the impossible paths do not merely fallthrough to the next symbol, but past the end of their own section, since LTO builds place each function in its own section. Thus filter `CC_FLAGS_LTO` out of the Clang invocation, so that it always emits machine code directly, with the traps in place. Assisted-by: LLM Cc: Gary Guo Cc: Boqun Feng Cc: Alice Ryhl Cc: Matthew Maurer Cc: Josh Poimboeuf Cc: Peter Zijlstra Cc: stable@vger.kernel.org Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust") Acked-by: Gary Guo Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org Signed-off-by: Miguel Ojeda --- drivers/gpu/drm/Kconfig.debug | 115 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 115 insertions(+) create mode 100644 drivers/gpu/drm/Kconfig.debug (limited to 'drivers/gpu/drm/Kconfig.debug') diff --git a/drivers/gpu/drm/Kconfig.debug b/drivers/gpu/drm/Kconfig.debug new file mode 100644 index 000000000..1f4c98cbf --- /dev/null +++ b/drivers/gpu/drm/Kconfig.debug @@ -0,0 +1,115 @@ +config DRM_USE_DYNAMIC_DEBUG + bool "use dynamic debug to implement drm.debug" + default n + depends on BROKEN + depends on DRM + depends on DYNAMIC_DEBUG || DYNAMIC_DEBUG_CORE + depends on JUMP_LABEL + help + Use dynamic-debug to avoid drm_debug_enabled() runtime overheads. + Due to callsite counts in DRM drivers (~4k in amdgpu) and 56 + bytes per callsite, the .data costs can be substantial, and + are therefore configurable. + +config DRM_WERROR + bool "Compile the drm subsystem with warnings as errors" + depends on DRM && EXPERT + depends on !WERROR + default n + help + A kernel build should not cause any compiler warnings, and this + enables the '-Werror' flag to enforce that rule in the drm subsystem. + + The drm subsystem enables more warnings than the kernel default, so + this config option is disabled by default. + + If in doubt, say N. + +config DRM_HEADER_TEST + bool "Ensure DRM headers are self-contained and pass kernel-doc" + depends on DRM && EXPERT && BROKEN + default n + help + Ensure the DRM subsystem headers both under drivers/gpu/drm and + include/drm compile, are self-contained, have header guards, and have + no kernel-doc warnings. + + If in doubt, say N. + +config DRM_DEBUG_MM + bool "Insert extra checks and debug info into the DRM range managers" + default n + depends on DRM + depends on STACKTRACE_SUPPORT + select STACKDEPOT + help + Enable allocation tracking of memory manager and leak detection on + shutdown. + + Recommended for driver developers only. + + If in doubt, say "N". + +config DRM_KUNIT_TEST_HELPERS + tristate + depends on DRM && KUNIT + select DRM_KMS_HELPER + help + KUnit Helpers for KMS drivers. + +config DRM_KUNIT_TEST + tristate "KUnit tests for DRM" if !KUNIT_ALL_TESTS + depends on DRM && KUNIT && MMU + select DRM_BRIDGE_CONNECTOR + select DRM_BUDDY + select DRM_DISPLAY_DP_HELPER + select DRM_DISPLAY_HDMI_STATE_HELPER + select DRM_DISPLAY_HELPER + select DRM_EXEC + select DRM_EXPORT_FOR_TESTS if m + select DRM_GEM_SHMEM_HELPER + select DRM_KUNIT_TEST_HELPERS + select DRM_SYSFB_HELPER + select PRIME_NUMBERS + default KUNIT_ALL_TESTS + help + This builds unit tests for DRM. This option is not useful for + distributions or general kernels, but only for kernel + developers working on DRM and associated drivers. + + For more information on KUnit and unit tests in general, + please refer to the KUnit documentation in + Documentation/dev-tools/kunit/. + + If in doubt, say "N". + +config DRM_TTM_KUNIT_TEST + tristate "KUnit tests for TTM" if !KUNIT_ALL_TESTS + depends on DRM && KUNIT && MMU && (UML || COMPILE_TEST) + select DRM_TTM + select DRM_BUDDY + select DRM_EXPORT_FOR_TESTS if m + select DRM_KUNIT_TEST_HELPERS + default KUNIT_ALL_TESTS + help + Enables unit tests for TTM, a GPU memory manager subsystem used + to manage memory buffers. This option is mostly useful for kernel + developers. It depends on (UML || COMPILE_TEST) since no other driver + which uses TTM can be loaded while running the tests. + + If in doubt, say "N". + +config DRM_SCHED_KUNIT_TEST + tristate "KUnit tests for the DRM scheduler" if !KUNIT_ALL_TESTS + select DRM_SCHED + depends on DRM && KUNIT + default KUNIT_ALL_TESTS + help + Choose this option to build unit tests for the DRM scheduler. + + Recommended for driver developers only. + + If in doubt, say "N". + +config DRM_EXPORT_FOR_TESTS + bool -- cgit v1.3.1