* [PATCH] ARM: drop Thumb-2 workaround for ancient binutils
@ 2020-05-07 9:33 Ard Biesheuvel
2020-05-13 16:15 ` Dave Martin
2020-05-14 14:13 ` Linus Walleij
0 siblings, 2 replies; 3+ messages in thread
From: Ard Biesheuvel @ 2020-05-07 9:33 UTC (permalink / raw)
To: linux-arm-kernel; +Cc: Dave Martin, linus.walleij, linux, arnd, Ard Biesheuvel
The CONFIG_THUMB2_AVOID_R_ARM_THM_JUMP11 workaround addresses an issue
which was fixed before the oldest supported binutils (2.23 at this time)
were released. So we can remove it now.
Cc: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
arch/arm/Kconfig | 31 -------------------------------
arch/arm/Makefile | 4 ----
2 files changed, 35 deletions(-)
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 165987aa5bcd..9a4d4c14fbde 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1425,37 +1425,6 @@ config THUMB2_KERNEL
If unsure, say N.
-config THUMB2_AVOID_R_ARM_THM_JUMP11
- bool "Work around buggy Thumb-2 short branch relocations in gas"
- depends on THUMB2_KERNEL && MODULES
- default y
- help
- Various binutils versions can resolve Thumb-2 branches to
- locally-defined, preemptible global symbols as short-range "b.n"
- branch instructions.
-
- This is a problem, because there's no guarantee the final
- destination of the symbol, or any candidate locations for a
- trampoline, are within range of the branch. For this reason, the
- kernel does not support fixing up the R_ARM_THM_JUMP11 (102)
- relocation in modules at all, and it makes little sense to add
- support.
-
- The symptom is that the kernel fails with an "unsupported
- relocation" error when loading some modules.
-
- Until fixed tools are available, passing
- -fno-optimize-sibling-calls to gcc should prevent gcc generating
- code which hits this problem, at the cost of a bit of extra runtime
- stack usage in some cases.
-
- The problem is described in more detail at:
- https://bugs.launchpad.net/binutils-linaro/+bug/725126
-
- Only Thumb-2 kernels are affected.
-
- Unless you are sure your tools don't have this problem, say Y.
-
config ARM_PATCH_IDIV
bool "Runtime patch udiv/sdiv instructions into __aeabi_{u}idiv()"
depends on CPU_32v7 && !XIP_KERNEL
diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index 7d5cd0f85461..ba65205ab609 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -125,10 +125,6 @@ AFLAGS_NOWARN :=$(call as-option,-Wa$(comma)-mno-warn-deprecated,-Wa$(comma)-W)
ifeq ($(CONFIG_THUMB2_KERNEL),y)
CFLAGS_ISA :=-mthumb -Wa,-mimplicit-it=always $(AFLAGS_NOWARN)
AFLAGS_ISA :=$(CFLAGS_ISA) -Wa$(comma)-mthumb
-# Work around buggy relocation from gas if requested:
-ifeq ($(CONFIG_THUMB2_AVOID_R_ARM_THM_JUMP11),y)
-KBUILD_CFLAGS_MODULE +=-fno-optimize-sibling-calls
-endif
else
CFLAGS_ISA :=$(call cc-option,-marm,) $(AFLAGS_NOWARN)
AFLAGS_ISA :=$(CFLAGS_ISA)
--
2.17.1
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linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] ARM: drop Thumb-2 workaround for ancient binutils
2020-05-07 9:33 [PATCH] ARM: drop Thumb-2 workaround for ancient binutils Ard Biesheuvel
@ 2020-05-13 16:15 ` Dave Martin
2020-05-14 14:13 ` Linus Walleij
1 sibling, 0 replies; 3+ messages in thread
From: Dave Martin @ 2020-05-13 16:15 UTC (permalink / raw)
To: Ard Biesheuvel; +Cc: linus.walleij, arnd, linux, linux-arm-kernel
On Thu, May 07, 2020 at 11:33:49AM +0200, Ard Biesheuvel wrote:
> The CONFIG_THUMB2_AVOID_R_ARM_THM_JUMP11 workaround addresses an issue
> which was fixed before the oldest supported binutils (2.23 at this time)
> were released. So we can remove it now.
Acked-by: Dave Martin <Dave.Martin@arm.com>
If we don't need this nasty fix any more, that's good for me. I wonder
if anyone still builds Thumb-2 kernels for real? Maybe uclinux needs
it?
(I'll trust you on the version number)
Cheers
---Dave
> Cc: Dave Martin <Dave.Martin@arm.com>
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> ---
> arch/arm/Kconfig | 31 -------------------------------
> arch/arm/Makefile | 4 ----
> 2 files changed, 35 deletions(-)
>
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 165987aa5bcd..9a4d4c14fbde 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -1425,37 +1425,6 @@ config THUMB2_KERNEL
>
> If unsure, say N.
>
> -config THUMB2_AVOID_R_ARM_THM_JUMP11
> - bool "Work around buggy Thumb-2 short branch relocations in gas"
> - depends on THUMB2_KERNEL && MODULES
> - default y
> - help
> - Various binutils versions can resolve Thumb-2 branches to
> - locally-defined, preemptible global symbols as short-range "b.n"
> - branch instructions.
> -
> - This is a problem, because there's no guarantee the final
> - destination of the symbol, or any candidate locations for a
> - trampoline, are within range of the branch. For this reason, the
> - kernel does not support fixing up the R_ARM_THM_JUMP11 (102)
> - relocation in modules at all, and it makes little sense to add
> - support.
> -
> - The symptom is that the kernel fails with an "unsupported
> - relocation" error when loading some modules.
> -
> - Until fixed tools are available, passing
> - -fno-optimize-sibling-calls to gcc should prevent gcc generating
> - code which hits this problem, at the cost of a bit of extra runtime
> - stack usage in some cases.
> -
> - The problem is described in more detail at:
> - https://bugs.launchpad.net/binutils-linaro/+bug/725126
> -
> - Only Thumb-2 kernels are affected.
> -
> - Unless you are sure your tools don't have this problem, say Y.
> -
> config ARM_PATCH_IDIV
> bool "Runtime patch udiv/sdiv instructions into __aeabi_{u}idiv()"
> depends on CPU_32v7 && !XIP_KERNEL
> diff --git a/arch/arm/Makefile b/arch/arm/Makefile
> index 7d5cd0f85461..ba65205ab609 100644
> --- a/arch/arm/Makefile
> +++ b/arch/arm/Makefile
> @@ -125,10 +125,6 @@ AFLAGS_NOWARN :=$(call as-option,-Wa$(comma)-mno-warn-deprecated,-Wa$(comma)-W)
> ifeq ($(CONFIG_THUMB2_KERNEL),y)
> CFLAGS_ISA :=-mthumb -Wa,-mimplicit-it=always $(AFLAGS_NOWARN)
> AFLAGS_ISA :=$(CFLAGS_ISA) -Wa$(comma)-mthumb
> -# Work around buggy relocation from gas if requested:
> -ifeq ($(CONFIG_THUMB2_AVOID_R_ARM_THM_JUMP11),y)
> -KBUILD_CFLAGS_MODULE +=-fno-optimize-sibling-calls
> -endif
> else
> CFLAGS_ISA :=$(call cc-option,-marm,) $(AFLAGS_NOWARN)
> AFLAGS_ISA :=$(CFLAGS_ISA)
> --
> 2.17.1
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] ARM: drop Thumb-2 workaround for ancient binutils
2020-05-07 9:33 [PATCH] ARM: drop Thumb-2 workaround for ancient binutils Ard Biesheuvel
2020-05-13 16:15 ` Dave Martin
@ 2020-05-14 14:13 ` Linus Walleij
1 sibling, 0 replies; 3+ messages in thread
From: Linus Walleij @ 2020-05-14 14:13 UTC (permalink / raw)
To: Ard Biesheuvel; +Cc: Arnd Bergmann, Russell King, Linux ARM, Dave Martin
On Thu, May 7, 2020 at 11:33 AM Ard Biesheuvel <ardb@kernel.org> wrote:
> The CONFIG_THUMB2_AVOID_R_ARM_THM_JUMP11 workaround addresses an issue
> which was fixed before the oldest supported binutils (2.23 at this time)
> were released. So we can remove it now.
>
> Cc: Dave Martin <Dave.Martin@arm.com>
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Makes sense.
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Yours,
Linus Walleij
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 3+ messages in thread
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2020-05-07 9:33 [PATCH] ARM: drop Thumb-2 workaround for ancient binutils Ard Biesheuvel
2020-05-13 16:15 ` Dave Martin
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