| Message ID | 20220309191633.2307110-1-nathan@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: Do not include __READ_ONCE() block in assembly files | expand |
On Wed, Mar 9, 2022 at 11:19 AM Nathan Chancellor <nathan@kernel.org> wrote: > > When building arm64 defconfig + CONFIG_LTO_CLANG_{FULL,THIN}=y after > commit 558c303c9734 ("arm64: Mitigate spectre style branch history side > channels"), the following error occurs: > > <instantiation>:4:2: error: invalid fixup for movz/movk instruction > mov w0, #ARM_SMCCC_ARCH_WORKAROUND_3 > ^ > > Marc figured out that moving "#include <linux/init.h>" in > include/linux/arm-smccc.h into a !__ASSEMBLY__ block resolves it. The > full include chain with CONFIG_LTO=y from include/linux/arm-smccc.h: > > include/linux/init.h > include/linux/compiler.h > arch/arm64/include/asm/rwonce.h > arch/arm64/include/asm/alternative-macros.h > arch/arm64/include/asm/assembler.h > > The asm/alternative-macros.h include in asm/rwonce.h only happens when > CONFIG_LTO is set, which ultimately casues asm/assembler.h to be > included before the definition of ARM_SMCCC_ARCH_WORKAROUND_3. As a > result, the preprocessor does not expand ARM_SMCCC_ARCH_WORKAROUND_3 in > __mitigate_spectre_bhb_fw, which results in the error above. > > Avoid this problem by just avoiding the CONFIG_LTO=y __READ_ONCE() block > in asm/rwonce.h with assembly files, as nothing in that block is useful > to assembly files, which allows ARM_SMCCC_ARCH_WORKAROUND_3 to be > properly expanded with CONFIG_LTO=y builds. > > Cc: stable@vger.kernel.org > Fixes: e35123d83ee3 ("arm64: lto: Strengthen READ_ONCE() to acquire when CONFIG_LTO=y") > Link: https://lore.kernel.org/r/20220309155716.3988480-1-maz@kernel.org/ > Reported-by: Marc Zyngier <maz@kernel.org> > Acked-by: James Morse <james.morse@arm.com> > Signed-off-by: Nathan Chancellor <nathan@kernel.org> Thanks for taking point on all of the BHB fallout. Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Tested-by: Nick Desaulniers <ndesaulniers@google.com> > --- > > This is based on current mainline; if it should be based on a specific > arm64 branch, please let me know. > > As 558c303c9734 is going to stable, I marked this for stable as well to > avoid breaking Android. I used e35123d83ee3 for the fixes tag to make it > clear to the stable team this should only go where that commit is > present. If a different fixes tag should be used, please feel free to > substitute. > > arch/arm64/include/asm/rwonce.h | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/include/asm/rwonce.h b/arch/arm64/include/asm/rwonce.h > index 1bce62fa908a..56f7b1d4d54b 100644 > --- a/arch/arm64/include/asm/rwonce.h > +++ b/arch/arm64/include/asm/rwonce.h > @@ -5,7 +5,7 @@ > #ifndef __ASM_RWONCE_H > #define __ASM_RWONCE_H > > -#ifdef CONFIG_LTO > +#if defined(CONFIG_LTO) && !defined(__ASSEMBLY__) > > #include <linux/compiler_types.h> > #include <asm/alternative-macros.h> > @@ -66,7 +66,7 @@ > }) > > #endif /* !BUILD_VDSO */ > -#endif /* CONFIG_LTO */ > +#endif /* CONFIG_LTO && !__ASSEMBLY__ */ > > #include <asm-generic/rwonce.h> > > > base-commit: 330f4c53d3c2d8b11d86ec03a964b86dc81452f5 > -- > 2.35.1 >
On Wed, Mar 09, 2022 at 01:53:50PM -0800, Nick Desaulniers wrote: > On Wed, Mar 9, 2022 at 11:19 AM Nathan Chancellor <nathan@kernel.org> wrote: > > Avoid this problem by just avoiding the CONFIG_LTO=y __READ_ONCE() block > > in asm/rwonce.h with assembly files, as nothing in that block is useful > > to assembly files, which allows ARM_SMCCC_ARCH_WORKAROUND_3 to be > > properly expanded with CONFIG_LTO=y builds. > > > > Cc: stable@vger.kernel.org > > Fixes: e35123d83ee3 ("arm64: lto: Strengthen READ_ONCE() to acquire when CONFIG_LTO=y") > > Link: https://lore.kernel.org/r/20220309155716.3988480-1-maz@kernel.org/ > > Reported-by: Marc Zyngier <maz@kernel.org> > > Acked-by: James Morse <james.morse@arm.com> > > Signed-off-by: Nathan Chancellor <nathan@kernel.org> > > Thanks for taking point on all of the BHB fallout. > > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> > Tested-by: Nick Desaulniers <ndesaulniers@google.com> Thanks for the review and testing. Unfortunately I've just sent the pull request to Linus, so didn't include your tags.
On Wed, 9 Mar 2022 12:16:34 -0700, Nathan Chancellor wrote: > When building arm64 defconfig + CONFIG_LTO_CLANG_{FULL,THIN}=y after > commit 558c303c9734 ("arm64: Mitigate spectre style branch history side > channels"), the following error occurs: > > <instantiation>:4:2: error: invalid fixup for movz/movk instruction > mov w0, #ARM_SMCCC_ARCH_WORKAROUND_3 > ^ > > [...] Applied to arm64 (for-next/spectre-bhb), thanks! [1/1] arm64: Do not include __READ_ONCE() block in assembly files https://git.kernel.org/arm64/c/52c9f93a9c48
diff --git a/arch/arm64/include/asm/rwonce.h b/arch/arm64/include/asm/rwonce.h index 1bce62fa908a..56f7b1d4d54b 100644 --- a/arch/arm64/include/asm/rwonce.h +++ b/arch/arm64/include/asm/rwonce.h @@ -5,7 +5,7 @@ #ifndef __ASM_RWONCE_H #define __ASM_RWONCE_H -#ifdef CONFIG_LTO +#if defined(CONFIG_LTO) && !defined(__ASSEMBLY__) #include <linux/compiler_types.h> #include <asm/alternative-macros.h> @@ -66,7 +66,7 @@ }) #endif /* !BUILD_VDSO */ -#endif /* CONFIG_LTO */ +#endif /* CONFIG_LTO && !__ASSEMBLY__ */ #include <asm-generic/rwonce.h>
When building arm64 defconfig + CONFIG_LTO_CLANG_{FULL,THIN}=y after commit 558c303c9734 ("arm64: Mitigate spectre style branch history side channels"), the following error occurs: <instantiation>:4:2: error: invalid fixup for movz/movk instruction mov w0, #ARM_SMCCC_ARCH_WORKAROUND_3 ^ Marc figured out that moving "#include <linux/init.h>" in include/linux/arm-smccc.h into a !__ASSEMBLY__ block resolves it. The full include chain with CONFIG_LTO=y from include/linux/arm-smccc.h: include/linux/init.h include/linux/compiler.h arch/arm64/include/asm/rwonce.h arch/arm64/include/asm/alternative-macros.h arch/arm64/include/asm/assembler.h The asm/alternative-macros.h include in asm/rwonce.h only happens when CONFIG_LTO is set, which ultimately casues asm/assembler.h to be included before the definition of ARM_SMCCC_ARCH_WORKAROUND_3. As a result, the preprocessor does not expand ARM_SMCCC_ARCH_WORKAROUND_3 in __mitigate_spectre_bhb_fw, which results in the error above. Avoid this problem by just avoiding the CONFIG_LTO=y __READ_ONCE() block in asm/rwonce.h with assembly files, as nothing in that block is useful to assembly files, which allows ARM_SMCCC_ARCH_WORKAROUND_3 to be properly expanded with CONFIG_LTO=y builds. Cc: stable@vger.kernel.org Fixes: e35123d83ee3 ("arm64: lto: Strengthen READ_ONCE() to acquire when CONFIG_LTO=y") Link: https://lore.kernel.org/r/20220309155716.3988480-1-maz@kernel.org/ Reported-by: Marc Zyngier <maz@kernel.org> Acked-by: James Morse <james.morse@arm.com> Signed-off-by: Nathan Chancellor <nathan@kernel.org> --- This is based on current mainline; if it should be based on a specific arm64 branch, please let me know. As 558c303c9734 is going to stable, I marked this for stable as well to avoid breaking Android. I used e35123d83ee3 for the fixes tag to make it clear to the stable team this should only go where that commit is present. If a different fixes tag should be used, please feel free to substitute. arch/arm64/include/asm/rwonce.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) base-commit: 330f4c53d3c2d8b11d86ec03a964b86dc81452f5