linux-kernel - Re: [tip: x86/bugs] x86/retpoline: Ensure default return thunk isn't used at runtime

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Message-ID: <20240216212745.GAZc_TURO0t35GjTQM@fat_crate.local>
Date: Fri, 16 Feb 2024 22:27:45 +0100
From: Borislav Petkov <bp@...en8.de>
To: Josh Poimboeuf <jpoimboe@...nel.org>
Cc: Nathan Chancellor <nathan@...nel.org>, linux-kernel@...r.kernel.org,
	linux-tip-commits@...r.kernel.org, x86@...nel.org
Subject: Re: [tip: x86/bugs] x86/retpoline: Ensure default return thunk isn't
 used at runtime

On Thu, Feb 15, 2024 at 09:42:35PM -0800, Josh Poimboeuf wrote:
> Right, the good news is this isn't a regression and the warning is
> working as designed.
> 
> This should tell the build to invoke objtool on that file:
> 
> diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
> index b1b8dd1608f7..92d67379f570 100644
> --- a/arch/x86/entry/vdso/Makefile
> +++ b/arch/x86/entry/vdso/Makefile
> @@ -36,6 +36,7 @@ UBSAN_SANITIZE_vma.o			:= y
>  KCSAN_SANITIZE_vma.o			:= y
>  OBJECT_FILES_NON_STANDARD_vma.o		:= n
>  OBJECT_FILES_NON_STANDARD_extable.o	:= n
> +OBJECT_FILES_NON_STANDARD_vdso-image-64.o := n

Right, this should be:

diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
index c4df99aa1615..4a514cafd73e 100644
--- a/arch/x86/entry/vdso/Makefile
+++ b/arch/x86/entry/vdso/Makefile
@@ -36,6 +36,8 @@ UBSAN_SANITIZE_vma.o			:= y
 KCSAN_SANITIZE_vma.o			:= y
 OBJECT_FILES_NON_STANDARD_vma.o		:= n
 OBJECT_FILES_NON_STANDARD_extable.o	:= n
+OBJECT_FILES_NON_STANDARD_vdso-image-32.o := n
+OBJECT_FILES_NON_STANDARD_vdso-image-64.o := n
 
 # vDSO images to build
 vdso_img-$(VDSO64-y)		+= 64

for completeness.

Lemme know if you want to write a formal patch or I should.

If you do, please make sure to include the exact way to reproduce
because we might need it in the future.

Thx.

-- 
Regards/Gruss,
    Boris.

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