* [PATCH AUTOSEL 6.6 5/6] ARM: 9434/1: cfi: Fix compilation corner case
[not found] <20241120140647.1768984-1-sashal@kernel.org>
@ 2024-11-20 14:06 ` Sasha Levin
2024-11-20 15:13 ` Nathan Chancellor
0 siblings, 1 reply; 3+ messages in thread
From: Sasha Levin @ 2024-11-20 14:06 UTC (permalink / raw)
To: linux-kernel, stable
Cc: Linus Walleij, kernel test robot, Nathan Chancellor, Russell King,
Sasha Levin, linux, arnd, samitolvanen, linux-arm-kernel, llvm
From: Linus Walleij <linus.walleij@linaro.org>
[ Upstream commit 4aea16b7cfb76bd3361858ceee6893ef5c9b5570 ]
When enabling expert mode CONFIG_EXPERT and using that power
user mode to disable the branch prediction hardening
!CONFIG_HARDEN_BRANCH_PREDICTOR, the assembly linker
in CLANG notices that some assembly in proc-v7.S does
not have corresponding C call sites, i.e. the prototypes
in proc-v7-bugs.c are enclosed in ifdef
CONFIG_HARDEN_BRANCH_PREDICTOR so this assembly:
SYM_TYPED_FUNC_START(cpu_v7_smc_switch_mm)
SYM_TYPED_FUNC_START(cpu_v7_hvc_switch_mm)
Results in:
ld.lld: error: undefined symbol: __kcfi_typeid_cpu_v7_smc_switch_mm
>>> referenced by proc-v7.S:94 (.../arch/arm/mm/proc-v7.S:94)
>>> arch/arm/mm/proc-v7.o:(.text+0x108) in archive vmlinux.a
ld.lld: error: undefined symbol: __kcfi_typeid_cpu_v7_hvc_switch_mm
>>> referenced by proc-v7.S:105 (.../arch/arm/mm/proc-v7.S:105)
>>> arch/arm/mm/proc-v7.o:(.text+0x124) in archive vmlinux.a
Fix this by adding an additional requirement that
CONFIG_HARDEN_BRANCH_PREDICTOR has to be enabled to compile
these assembly calls.
Closes: https://lore.kernel.org/oe-kbuild-all/202411041456.ZsoEiD7T-lkp@intel.com/
Reported-by: kernel test robot <lkp@intel.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/arm/mm/proc-v7.S | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index 193c7aeb67039..bea11f9bfe856 100644
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -93,7 +93,7 @@ ENTRY(cpu_v7_dcache_clean_area)
ret lr
ENDPROC(cpu_v7_dcache_clean_area)
-#ifdef CONFIG_ARM_PSCI
+#if defined(CONFIG_ARM_PSCI) && defined(CONFIG_HARDEN_BRANCH_PREDICTOR)
.arch_extension sec
ENTRY(cpu_v7_smc_switch_mm)
stmfd sp!, {r0 - r3}
--
2.43.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH AUTOSEL 6.6 5/6] ARM: 9434/1: cfi: Fix compilation corner case
2024-11-20 14:06 ` [PATCH AUTOSEL 6.6 5/6] ARM: 9434/1: cfi: Fix compilation corner case Sasha Levin
@ 2024-11-20 15:13 ` Nathan Chancellor
2024-11-22 15:21 ` Sasha Levin
0 siblings, 1 reply; 3+ messages in thread
From: Nathan Chancellor @ 2024-11-20 15:13 UTC (permalink / raw)
To: Sasha Levin
Cc: linux-kernel, stable, Linus Walleij, kernel test robot,
Russell King, linux, arnd, samitolvanen, linux-arm-kernel, llvm
Hi Sasha,
On Wed, Nov 20, 2024 at 09:06:35AM -0500, Sasha Levin wrote:
> From: Linus Walleij <linus.walleij@linaro.org>
>
> [ Upstream commit 4aea16b7cfb76bd3361858ceee6893ef5c9b5570 ]
>
> When enabling expert mode CONFIG_EXPERT and using that power
> user mode to disable the branch prediction hardening
> !CONFIG_HARDEN_BRANCH_PREDICTOR, the assembly linker
> in CLANG notices that some assembly in proc-v7.S does
> not have corresponding C call sites, i.e. the prototypes
> in proc-v7-bugs.c are enclosed in ifdef
> CONFIG_HARDEN_BRANCH_PREDICTOR so this assembly:
>
> SYM_TYPED_FUNC_START(cpu_v7_smc_switch_mm)
> SYM_TYPED_FUNC_START(cpu_v7_hvc_switch_mm)
>
> Results in:
>
> ld.lld: error: undefined symbol: __kcfi_typeid_cpu_v7_smc_switch_mm
> >>> referenced by proc-v7.S:94 (.../arch/arm/mm/proc-v7.S:94)
> >>> arch/arm/mm/proc-v7.o:(.text+0x108) in archive vmlinux.a
>
> ld.lld: error: undefined symbol: __kcfi_typeid_cpu_v7_hvc_switch_mm
> >>> referenced by proc-v7.S:105 (.../arch/arm/mm/proc-v7.S:105)
> >>> arch/arm/mm/proc-v7.o:(.text+0x124) in archive vmlinux.a
>
> Fix this by adding an additional requirement that
> CONFIG_HARDEN_BRANCH_PREDICTOR has to be enabled to compile
> these assembly calls.
>
> Closes: https://lore.kernel.org/oe-kbuild-all/202411041456.ZsoEiD7T-lkp@intel.com/
>
> Reported-by: kernel test robot <lkp@intel.com>
> Reviewed-by: Nathan Chancellor <nathan@kernel.org>
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
> Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
> arch/arm/mm/proc-v7.S | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
> index 193c7aeb67039..bea11f9bfe856 100644
> --- a/arch/arm/mm/proc-v7.S
> +++ b/arch/arm/mm/proc-v7.S
> @@ -93,7 +93,7 @@ ENTRY(cpu_v7_dcache_clean_area)
> ret lr
> ENDPROC(cpu_v7_dcache_clean_area)
>
> -#ifdef CONFIG_ARM_PSCI
> +#if defined(CONFIG_ARM_PSCI) && defined(CONFIG_HARDEN_BRANCH_PREDICTOR)
> .arch_extension sec
> ENTRY(cpu_v7_smc_switch_mm)
This patch is unnecessary in branches prior to 6.10 (when ARM started
supporting kCFI) because SYM_TYPED_FUNC_START() is not used here. I
would just drop it for 6.6 and earlier.
> stmfd sp!, {r0 - r3}
> --
> 2.43.0
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH AUTOSEL 6.6 5/6] ARM: 9434/1: cfi: Fix compilation corner case
2024-11-20 15:13 ` Nathan Chancellor
@ 2024-11-22 15:21 ` Sasha Levin
0 siblings, 0 replies; 3+ messages in thread
From: Sasha Levin @ 2024-11-22 15:21 UTC (permalink / raw)
To: Nathan Chancellor
Cc: linux-kernel, stable, Linus Walleij, kernel test robot,
Russell King, linux, arnd, samitolvanen, linux-arm-kernel, llvm
On Wed, Nov 20, 2024 at 08:13:38AM -0700, Nathan Chancellor wrote:
>Hi Sasha,
>
>On Wed, Nov 20, 2024 at 09:06:35AM -0500, Sasha Levin wrote:
>> From: Linus Walleij <linus.walleij@linaro.org>
>>
>> [ Upstream commit 4aea16b7cfb76bd3361858ceee6893ef5c9b5570 ]
>>
>> When enabling expert mode CONFIG_EXPERT and using that power
>> user mode to disable the branch prediction hardening
>> !CONFIG_HARDEN_BRANCH_PREDICTOR, the assembly linker
>> in CLANG notices that some assembly in proc-v7.S does
>> not have corresponding C call sites, i.e. the prototypes
>> in proc-v7-bugs.c are enclosed in ifdef
>> CONFIG_HARDEN_BRANCH_PREDICTOR so this assembly:
>>
>> SYM_TYPED_FUNC_START(cpu_v7_smc_switch_mm)
>> SYM_TYPED_FUNC_START(cpu_v7_hvc_switch_mm)
>>
>> Results in:
>>
>> ld.lld: error: undefined symbol: __kcfi_typeid_cpu_v7_smc_switch_mm
>> >>> referenced by proc-v7.S:94 (.../arch/arm/mm/proc-v7.S:94)
>> >>> arch/arm/mm/proc-v7.o:(.text+0x108) in archive vmlinux.a
>>
>> ld.lld: error: undefined symbol: __kcfi_typeid_cpu_v7_hvc_switch_mm
>> >>> referenced by proc-v7.S:105 (.../arch/arm/mm/proc-v7.S:105)
>> >>> arch/arm/mm/proc-v7.o:(.text+0x124) in archive vmlinux.a
>>
>> Fix this by adding an additional requirement that
>> CONFIG_HARDEN_BRANCH_PREDICTOR has to be enabled to compile
>> these assembly calls.
>>
>> Closes: https://lore.kernel.org/oe-kbuild-all/202411041456.ZsoEiD7T-lkp@intel.com/
>>
>> Reported-by: kernel test robot <lkp@intel.com>
>> Reviewed-by: Nathan Chancellor <nathan@kernel.org>
>> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
>> Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
>> Signed-off-by: Sasha Levin <sashal@kernel.org>
>> ---
>> arch/arm/mm/proc-v7.S | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
>> index 193c7aeb67039..bea11f9bfe856 100644
>> --- a/arch/arm/mm/proc-v7.S
>> +++ b/arch/arm/mm/proc-v7.S
>> @@ -93,7 +93,7 @@ ENTRY(cpu_v7_dcache_clean_area)
>> ret lr
>> ENDPROC(cpu_v7_dcache_clean_area)
>>
>> -#ifdef CONFIG_ARM_PSCI
>> +#if defined(CONFIG_ARM_PSCI) && defined(CONFIG_HARDEN_BRANCH_PREDICTOR)
>> .arch_extension sec
>> ENTRY(cpu_v7_smc_switch_mm)
>
>This patch is unnecessary in branches prior to 6.10 (when ARM started
>supporting kCFI) because SYM_TYPED_FUNC_START() is not used here. I
>would just drop it for 6.6 and earlier.
Ack, will do.
--
Thanks,
Sasha
^ permalink raw reply [flat|nested] 3+ messages in thread
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2024-11-20 14:06 ` [PATCH AUTOSEL 6.6 5/6] ARM: 9434/1: cfi: Fix compilation corner case Sasha Levin
2024-11-20 15:13 ` Nathan Chancellor
2024-11-22 15:21 ` Sasha Levin
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