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[PATCH v3 1/7] x86/boot/startup: Disable objtool validation for library code

Ard Biesheuvel posted 7 patches 8 months, 2 weeks ago
There is a newer version of this series
[PATCH v3 1/7] x86/boot/startup: Disable objtool validation for library code
Posted by Ard Biesheuvel 8 months, 2 weeks ago 
From: Ard Biesheuvel <ardb@kernel.org>

The library code built under arch/x86/boot/startup is not intended to be
linked into vmlinux but only into the decompressor and/or the EFI stub.

This means objtool validation is not needed here, and may result in
false positive errors for things like missing retpolines.

So disable it for all objects added to lib-y

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/x86/boot/startup/Makefile | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/x86/boot/startup/Makefile b/arch/x86/boot/startup/Makefile
index 73946a3f6b3b..8919a1cbcb5a 100644
--- a/arch/x86/boot/startup/Makefile
+++ b/arch/x86/boot/startup/Makefile
@@ -4,3 +4,9 @@ KBUILD_AFLAGS		+= -D__DISABLE_EXPORTS
 
 lib-$(CONFIG_X86_64)		+= la57toggle.o
 lib-$(CONFIG_EFI_MIXED)		+= efi-mixed.o
+
+#
+# Disable objtool validation for all library code, which is intended
+# to be linked into the decompressor or the EFI stub but not vmlinux
+#
+$(patsubst %.o,$(obj)/%.o,$(lib-y)): OBJECT_FILES_NON_STANDARD := y
-- 
2.49.0.504.g3bcea36a83-goog
Re: [PATCH v3 1/7] x86/boot/startup: Disable objtool validation for library code
Posted by Borah, Chaitanya Kumar 8 months, 1 week ago 
On 4/8/2025 2:22 PM, Ard Biesheuvel wrote:
> From: Ard Biesheuvel <ardb@kernel.org>
>
> The library code built under arch/x86/boot/startup is not intended to be
> linked into vmlinux but only into the decompressor and/or the EFI stub.
>
> This means objtool validation is not needed here, and may result in
> false positive errors for things like missing retpolines.
>
> So disable it for all objects added to lib-y
>
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Solves 
https://lore.kernel.org/intel-gfx/CAMj1kXEfBMczOmA2+dMMubuD-qE59GTAiV2E_9m8KNG4-rgP6Q@mail.gmail.com/T/#mbf2913e778475b70617390d4a5d0244295b9cb8c

Tested-by: Chaitanya Kumar Borah <chaitanya.kumar.borah@intel.com>

> ---
>   arch/x86/boot/startup/Makefile | 6 ++++++
>   1 file changed, 6 insertions(+)
>
> diff --git a/arch/x86/boot/startup/Makefile b/arch/x86/boot/startup/Makefile
> index 73946a3f6b3b..8919a1cbcb5a 100644
> --- a/arch/x86/boot/startup/Makefile
> +++ b/arch/x86/boot/startup/Makefile
> @@ -4,3 +4,9 @@ KBUILD_AFLAGS		+= -D__DISABLE_EXPORTS
>   
>   lib-$(CONFIG_X86_64)		+= la57toggle.o
>   lib-$(CONFIG_EFI_MIXED)		+= efi-mixed.o
> +
> +#
> +# Disable objtool validation for all library code, which is intended
> +# to be linked into the decompressor or the EFI stub but not vmlinux
> +#
> +$(patsubst %.o,$(obj)/%.o,$(lib-y)): OBJECT_FILES_NON_STANDARD := y
Re: [PATCH v3 1/7] x86/boot/startup: Disable objtool validation for library code
Posted by Ingo Molnar 8 months, 1 week ago 
* Borah, Chaitanya Kumar <chaitanya.kumar.borah@intel.com> wrote:

> 
> On 4/8/2025 2:22 PM, Ard Biesheuvel wrote:
> > From: Ard Biesheuvel <ardb@kernel.org>
> > 
> > The library code built under arch/x86/boot/startup is not intended to be
> > linked into vmlinux but only into the decompressor and/or the EFI stub.
> > 
> > This means objtool validation is not needed here, and may result in
> > false positive errors for things like missing retpolines.
> > 
> > So disable it for all objects added to lib-y
> > 
> > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> 
> Solves https://lore.kernel.org/intel-gfx/CAMj1kXEfBMczOmA2+dMMubuD-qE59GTAiV2E_9m8KNG4-rgP6Q@mail.gmail.com/T/#mbf2913e778475b70617390d4a5d0244295b9cb8c
> 
> Tested-by: Chaitanya Kumar Borah <chaitanya.kumar.borah@intel.com>

Thank you for the testing!

	Ingo
[tip: x86/boot] x86/boot/startup: Disable objtool validation for library code
Posted by tip-bot2 for Ard Biesheuvel 8 months, 1 week ago 
The following commit has been merged into the x86/boot branch of tip:

Commit-ID:     d9fa398fe82728ee703ad2bd9cf5247df9626470
Gitweb:        https://git.kernel.org/tip/d9fa398fe82728ee703ad2bd9cf5247df9626470
Author:        Ard Biesheuvel <ardb@kernel.org>
AuthorDate:    Tue, 08 Apr 2025 10:52:56 +02:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Wed, 09 Apr 2025 11:59:03 +02:00

x86/boot/startup: Disable objtool validation for library code

The library code built under arch/x86/boot/startup is not intended to be
linked into vmlinux but only into the decompressor and/or the EFI stub.

This means objtool validation is not needed here, and may result in
false positive errors for things like missing retpolines.

So disable it for all objects added to lib-y

Tested-by: Chaitanya Kumar Borah <chaitanya.kumar.borah@intel.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Len Brown <len.brown@intel.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20250408085254.836788-10-ardb+git@google.com
---
 arch/x86/boot/startup/Makefile | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/x86/boot/startup/Makefile b/arch/x86/boot/startup/Makefile
index 73946a3..8919a1c 100644
--- a/arch/x86/boot/startup/Makefile
+++ b/arch/x86/boot/startup/Makefile
@@ -4,3 +4,9 @@ KBUILD_AFLAGS		+= -D__DISABLE_EXPORTS
 
 lib-$(CONFIG_X86_64)		+= la57toggle.o
 lib-$(CONFIG_EFI_MIXED)		+= efi-mixed.o
+
+#
+# Disable objtool validation for all library code, which is intended
+# to be linked into the decompressor or the EFI stub but not vmlinux
+#
+$(patsubst %.o,$(obj)/%.o,$(lib-y)): OBJECT_FILES_NON_STANDARD := y

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