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Message-Id: <20250315-kbuild-prefix-map-v2-1-00e1983b2a23@weissschuh.net> Date: Sat, 15 Mar 2025 14:20:14 +0100 From: Thomas Weißschuh <linux@...ssschuh.net> To: Masahiro Yamada <masahiroy@...nel.org>, Nathan Chancellor <nathan@...nel.org>, Nicolas Schier <nicolas@...sle.eu>, Jonathan Corbet <corbet@....net>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>, Ben Hutchings <ben@...adent.org.uk> Cc: linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org, Thomas Weißschuh <linux@...ssschuh.net> Subject: [PATCH v2] kbuild: make all file references relative to source root -fmacro-prefix-map only affects __FILE__ and __BASE_FILE__. Other references, for example in debug information, are not affected. This makes handling of file references in the compiler outputs harder to use and creates problems for reproducible builds. Switch to -ffile-prefix map which affects all references. Also drop the documentation section advising manual specification of -fdebug-prefix-map for reproducible builds, as it is not necessary anymore. Suggested-by: Ben Hutchings <ben@...adent.org.uk> Link: https://lore.kernel.org/lkml/c49cc967294f9a3a4a34f69b6a8727a6d3959ed8.camel@decadent.org.uk/ Acked-by: Borislav Petkov (AMD) <bp@...en8.de> # arch/x86/ Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net> --- Changes in v2: - Pick up Ack from Borislav - Merge all changes into single patch - Also drop link to KCFLAGS from docs - Link to v1: https://lore.kernel.org/r/20250313-kbuild-prefix-map-v1-0-38cea8448c5f@weissschuh.net --- Documentation/kbuild/reproducible-builds.rst | 17 ----------------- Makefile | 2 +- arch/x86/boot/Makefile | 2 +- arch/x86/boot/compressed/Makefile | 2 +- 4 files changed, 3 insertions(+), 20 deletions(-) diff --git a/Documentation/kbuild/reproducible-builds.rst b/Documentation/kbuild/reproducible-builds.rst index f2dcc39044e66ddd165646e0b51ccb0209aca7dd..a7762486c93fcd3eba08b836bed622a41e829e41 100644 --- a/Documentation/kbuild/reproducible-builds.rst +++ b/Documentation/kbuild/reproducible-builds.rst @@ -46,21 +46,6 @@ The kernel embeds the building user and host names in `KBUILD_BUILD_USER and KBUILD_BUILD_HOST`_ variables. If you are building from a git commit, you could use its committer address. -Absolute filenames ------------------- - -When the kernel is built out-of-tree, debug information may include -absolute filenames for the source files. This must be overridden by -including the ``-fdebug-prefix-map`` option in the `KCFLAGS`_ variable. - -Depending on the compiler used, the ``__FILE__`` macro may also expand -to an absolute filename in an out-of-tree build. Kbuild automatically -uses the ``-fmacro-prefix-map`` option to prevent this, if it is -supported. - -The Reproducible Builds web site has more information about these -`prefix-map options`_. - Generated files in source packages ---------------------------------- @@ -131,7 +116,5 @@ See ``scripts/setlocalversion`` for details. .. _KBUILD_BUILD_TIMESTAMP: kbuild.html#kbuild-build-timestamp .. _KBUILD_BUILD_USER and KBUILD_BUILD_HOST: kbuild.html#kbuild-build-user-kbuild-build-host -.. _KCFLAGS: kbuild.html#kcflags -.. _prefix-map options: https://reproducible-builds.org/docs/build-path/ .. _Reproducible Builds project: https://reproducible-builds.org/ .. _SOURCE_DATE_EPOCH: https://reproducible-builds.org/docs/source-date-epoch/ diff --git a/Makefile b/Makefile index 5c333682dc9142b1aacfe454a5c77f5923554b7d..4f920187cee658ae4d1b807fca365f6994274828 100644 --- a/Makefile +++ b/Makefile @@ -1067,7 +1067,7 @@ endif # change __FILE__ to the relative path to the source directory ifdef building_out_of_srctree -KBUILD_CPPFLAGS += $(call cc-option,-fmacro-prefix-map=$(srcroot)/=) +KBUILD_CPPFLAGS += $(call cc-option,-ffile-prefix-map=$(srcroot)/=) KBUILD_RUSTFLAGS += --remap-path-prefix=$(srcroot)/= endif diff --git a/arch/x86/boot/Makefile b/arch/x86/boot/Makefile index 9cc0ff6e9067d574488a35573eff4d0f8449e398..f500f82864aae80deb74faa3df9a8b6333d6c4ca 100644 --- a/arch/x86/boot/Makefile +++ b/arch/x86/boot/Makefile @@ -54,7 +54,7 @@ targets += cpustr.h KBUILD_CFLAGS := $(REALMODE_CFLAGS) -D_SETUP KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__ -KBUILD_CFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=) +KBUILD_CFLAGS += $(call cc-option,-ffile-prefix-map=$(srctree)/=) KBUILD_CFLAGS += -fno-asynchronous-unwind-tables KBUILD_CFLAGS += $(CONFIG_CC_IMPLICIT_FALLTHROUGH) diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile index 5edee7a9786c67e13c295473751b82387bcbd67e..ad324978b2e5b1b6f8be82647769c99db8257ac7 100644 --- a/arch/x86/boot/compressed/Makefile +++ b/arch/x86/boot/compressed/Makefile @@ -38,7 +38,7 @@ KBUILD_CFLAGS += -fno-stack-protector KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member) KBUILD_CFLAGS += $(call cc-disable-warning, gnu) KBUILD_CFLAGS += -Wno-pointer-sign -KBUILD_CFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=) +KBUILD_CFLAGS += $(call cc-option,-ffile-prefix-map=$(srctree)/=) KBUILD_CFLAGS += -fno-asynchronous-unwind-tables KBUILD_CFLAGS += -D__DISABLE_EXPORTS # Disable relocation relaxation in case the link is not PIE. --- base-commit: a57512d6cd88eba04cdc1fb83832c00d248bd0d1 change-id: 20250312-kbuild-prefix-map-5ae76c209e7a Best regards, -- Thomas Weißschuh <linux@...ssschuh.net>
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