[PATCH 0/4] kbuild: make all file references relative to source root

[PATCH 0/4] kbuild: make all file references relative to source root

[Thomas Weißschuh]

-fmacro-prefix-map only affects __FILE__ and __BASE_FILE__.
Other references, for example in debug information, is not affected.
This makes handling of file references in the compiler output harder to
use and creates problems for reproducible builds.

Switch to -ffile-prefix map which affects all references.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
Thomas Weißschuh (4):
      kbuild: make all file references relative to source root
      kbuild: doc: reproducible-builds: drop section "Absolute filenames"
      x86/boot: Switch to -ffile-prefix-map
      x86/boot/compressed: Switch to -ffile-prefix-map

 Documentation/kbuild/reproducible-builds.rst | 16 ----------------
 Makefile                                     |  2 +-
 arch/x86/boot/Makefile                       |  2 +-
 arch/x86/boot/compressed/Makefile            |  2 +-
 4 files changed, 3 insertions(+), 19 deletions(-)
---
base-commit: bc5431693696b3f928b0b7acf8d7a120127db7a4
change-id: 20250312-kbuild-prefix-map-5ae76c209e7a

Best regards,
-- 
Thomas Weißschuh <linux@weissschuh.net>

[PATCH 1/4] kbuild: make all file references relative to source root

[Thomas Weißschuh]

-fmacro-prefix-map only affects __FILE__ and __BASE_FILE__.
Other references, for example in debug information, is not affected.
This makes handling of file references in the compiler output harder to
use and creates problems for reproducible builds.

Switch to -ffile-prefix map which affects all references.

Suggested-by: Ben Hutchings <ben@decadent.org.uk>
Link: https://lore.kernel.org/lkml/c49cc967294f9a3a4a34f69b6a8727a6d3959ed8.camel@decadent.org.uk/
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
 Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index 30242e731a0d19faa0ffbeada8313e77c4105b41..7b1683bb60e2f473b255fb8a0bde97b15d19ddb6 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
 

-- 
2.48.1

[PATCH 2/4] kbuild: doc: reproducible-builds: drop section "Absolute filenames"

[Thomas Weißschuh]

The top-level Makefile now uses the generic -ffile-prefix-map which also
affects debug information, making the manual override superfluous.

Drop the now unnecessary section.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
 Documentation/kbuild/reproducible-builds.rst | 16 ----------------
 1 file changed, 16 deletions(-)

diff --git a/Documentation/kbuild/reproducible-builds.rst b/Documentation/kbuild/reproducible-builds.rst
index f2dcc39044e66ddd165646e0b51ccb0209aca7dd..c815f486926253ffe5daa5e9a9ab3dbcb142c6fc 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
 ----------------------------------
 
@@ -132,6 +117,5 @@ 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/

-- 
2.48.1

[PATCH 3/4] x86/boot: Switch to -ffile-prefix-map

[Thomas Weißschuh]

-ffile-prefix-map is a more general variant of the currently used
-fmacro-prefix-map. It is also what the top-level Makefile is using now.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
 arch/x86/boot/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

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)
 

-- 
2.48.1

Re: [PATCH 3/4] x86/boot: Switch to -ffile-prefix-map

[Masahiro Yamada]

Hi X86 maintainers,

Is it OK to pick up this to kbuild tree?
Ack is appreciated.



On Fri, Mar 14, 2025 at 12:59 AM Thomas Weißschuh <linux@weissschuh.net> wrote:
>
> -ffile-prefix-map is a more general variant of the currently used
> -fmacro-prefix-map. It is also what the top-level Makefile is using now.
>
> Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
> ---
>  arch/x86/boot/Makefile | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> 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)
>
>
> --
> 2.48.1
>


--
Best Regards
Masahiro Yamada

Re: [PATCH 3/4] x86/boot: Switch to -ffile-prefix-map

[Borislav Petkov]

On Sat, Mar 15, 2025 at 05:15:33PM +0900, Masahiro Yamada wrote:
> Hi X86 maintainers,
> 
> Is it OK to pick up this to kbuild tree?
> Ack is appreciated.

For both:

Acked-by: Borislav Petkov (AMD) <bp@alien8.de>

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

[PATCH 4/4] x86/boot/compressed: Switch to -ffile-prefix-map

[Thomas Weißschuh]

-ffile-prefix-map is a more general variant of the currently used
-fmacro-prefix-map. It is also what the top-level Makefile is using now.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
 arch/x86/boot/compressed/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 606c74f274593ebaf6200b7d307a453e2c6e872e..73a67366cb706658f9680cd50864a68546d3dc98 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.

-- 
2.48.1

Re: [PATCH 4/4] x86/boot/compressed: Switch to -ffile-prefix-map

[Masahiro Yamada]

Hi X86 maintainers,

Is it OK to pick up this to kbuild tree?
Ack is appreciated.


On Fri, Mar 14, 2025 at 12:59 AM Thomas Weißschuh <linux@weissschuh.net> wrote:
>
> -ffile-prefix-map is a more general variant of the currently used
> -fmacro-prefix-map. It is also what the top-level Makefile is using now.
>
> Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
> ---
>  arch/x86/boot/compressed/Makefile | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
> index 606c74f274593ebaf6200b7d307a453e2c6e872e..73a67366cb706658f9680cd50864a68546d3dc98 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.
>
> --
> 2.48.1
>


-- 
Best Regards
Masahiro Yamada

Re: [PATCH 4/4] x86/boot/compressed: Switch to -ffile-prefix-map

[Ingo Molnar]

* Masahiro Yamada <masahiroy@kernel.org> wrote:

> Hi X86 maintainers,
> 
> Is it OK to pick up this to kbuild tree?
> Ack is appreciated.

Acked-by: Ingo Molnar <mingo@kernel.org>

Thank you for picking up these!

	Ingo

Re: [PATCH 4/4] x86/boot/compressed: Switch to -ffile-prefix-map

[Masahiro Yamada]

On Sun, Mar 16, 2025 at 6:25 AM Ingo Molnar <mingo@kernel.org> wrote:
>
>
> * Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> > Hi X86 maintainers,
> >
> > Is it OK to pick up this to kbuild tree?
> > Ack is appreciated.
>
> Acked-by: Ingo Molnar <mingo@kernel.org>
>
> Thank you for picking up these!
>
>         Ingo

Thanks, I will add your Ack to v2 and apply it.

-- 
Best Regards
Masahiro Yamada

Re: [PATCH 0/4] kbuild: make all file references relative to source root

[Borislav Petkov]

On Thu, Mar 13, 2025 at 04:59:08PM +0100, Thomas Weißschuh wrote:
> -fmacro-prefix-map only affects __FILE__ and __BASE_FILE__.
> Other references, for example in debug information, is not affected.
> This makes handling of file references in the compiler output harder to
> use and creates problems for reproducible builds.
> 
> Switch to -ffile-prefix map which affects all references.
> 
> Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
> ---
> Thomas Weißschuh (4):
>       kbuild: make all file references relative to source root
>       kbuild: doc: reproducible-builds: drop section "Absolute filenames"
>       x86/boot: Switch to -ffile-prefix-map
>       x86/boot/compressed: Switch to -ffile-prefix-map

Btw, I don't see why those are 4 patches - it is a single logical change that
converts to this new compiler switch.

So why are they 4?

Masahiro, might as well merge them into one...

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

Re: [PATCH 0/4] kbuild: make all file references relative to source root

[Masahiro Yamada]

On Sat, Mar 15, 2025 at 8:34 PM Borislav Petkov <bp@alien8.de> wrote:
>
> On Thu, Mar 13, 2025 at 04:59:08PM +0100, Thomas Weißschuh wrote:
> > -fmacro-prefix-map only affects __FILE__ and __BASE_FILE__.
> > Other references, for example in debug information, is not affected.
> > This makes handling of file references in the compiler output harder to
> > use and creates problems for reproducible builds.
> >
> > Switch to -ffile-prefix map which affects all references.
> >
> > Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
> > ---
> > Thomas Weißschuh (4):
> >       kbuild: make all file references relative to source root
> >       kbuild: doc: reproducible-builds: drop section "Absolute filenames"
> >       x86/boot: Switch to -ffile-prefix-map
> >       x86/boot/compressed: Switch to -ffile-prefix-map
>
> Btw, I don't see why those are 4 patches - it is a single logical change that
> converts to this new compiler switch.
>
> So why are they 4?

Good point.

>
> Masahiro, might as well merge them into one...

I'd like Thomas to submit a single patch.




--
Best Regards
Masahiro Yamada