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Message-ID: <aBEttQH4kimHFScx@intel.com> Date: Tue, 29 Apr 2025 22:51:17 +0300 From: Ville Syrjälä <ville.syrjala@...ux.intel.com> To: Thomas Weißschuh <linux@...ssschuh.net> Cc: 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>, linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org Subject: Re: [PATCH v2] kbuild: make all file references relative to source root On Sat, Mar 15, 2025 at 02:20:14PM +0100, Thomas Weißschuh wrote: > -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. Hi, This broke 'objdump -S' completely for me. I see the following difference in the debug info: - <12> DW_AT_name : (indirect line string, offset: 0): drivers/gpu/drm/i915/i915_config.c - <16> DW_AT_comp_dir : (indirect line string, offset: 0x23): /home/.../src/linux-2.6/build + <12> DW_AT_name : (indirect line string, offset: 0): ../drivers/gpu/drm/i915/i915_config.c + <16> DW_AT_comp_dir : (indirect line string, offset: 0x26): /home/.../src/linux-2.6/build Looks like I can work around it with some combination of --prefix and --prefix-strip, but that seems far too tedious to have to do every time I need to decode an oops. > > 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> > -- Ville Syrjälä Intel
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