| Message ID | 20200507093349.25313-1-ardb@kernel.org (mailing list archive) |
|---|---|
| State | Mainlined |
| Commit | 67b0141bd12d3a609d47ebbb53a4df67e3fdf4c4 |
| Headers | show |
| Series | ARM: drop Thumb-2 workaround for ancient binutils | expand |
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
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
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)
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(-)