Patchwork [U-Boot,v3,2/9] arm: work around assembler bug

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Submitter Allen Martin
Date Aug. 15, 2012, 9:38 p.m.
Message ID <1345066741-19613-3-git-send-email-amartin@nvidia.com>
Download mbox | patch
Permalink /patch/177858/
State Changes Requested
Delegated to: Tom Warren
Headers show

Comments

Allen Martin - Aug. 15, 2012, 9:38 p.m.
Disable sibling call optimization based on binutils version.  This is
to work around a bug in the assember in binutils versions < 2.22.
Branches to weak symbols can be incorrectly optimized in thumb mode to
a short branch (b.n instruction) that won't reach when the symbol gets
preempted.

http://sourceware.org/bugzilla/show_bug.cgi?id=12532

Signed-off-by: Allen Martin <amartin@nvidia.com>
---
 arch/arm/config.mk |   18 ++++++++++++++++++
 1 file changed, 18 insertions(+)
Marek Vasut - Sept. 6, 2012, 3:03 a.m.
Dear Allen Martin,

> Disable sibling call optimization based on binutils version.  This is
> to work around a bug in the assember in binutils versions < 2.22.
> Branches to weak symbols can be incorrectly optimized in thumb mode to
> a short branch (b.n instruction) that won't reach when the symbol gets
> preempted.

CC Albert ... Albert, let's pull this in as a part of this series.

I'm fine with it.

> http://sourceware.org/bugzilla/show_bug.cgi?id=12532
> 
> Signed-off-by: Allen Martin <amartin@nvidia.com>
> ---
>  arch/arm/config.mk |   18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/arch/arm/config.mk b/arch/arm/config.mk
> index 3f4453a..24b9d7c 100644
> --- a/arch/arm/config.mk
> +++ b/arch/arm/config.mk
> @@ -87,3 +87,21 @@ endif
>  ifndef CONFIG_NAND_SPL
>  LDFLAGS_u-boot += -pie
>  endif
> +
> +#
> +# FIXME: binutils versions < 2.22 have a bug in the assembler where
> +# branches to weak symbols can be incorrectly optimized in thumb mode
> +# to a short branch (b.n instruction) that won't reach when the symbol
> +# gets preempted
> +#
> +# http://sourceware.org/bugzilla/show_bug.cgi?id=12532
> +#
> +ifeq ($(CONFIG_SYS_THUMB_BUILD),y)
> +ifeq ($(GAS_BUG_12532),)
> +export GAS_BUG_12532:=$(shell if [ $(call binutils-version) -lt 0222 ] ; \
> +	then echo y; else echo n; fi)
> +endif
> +ifeq ($(GAS_BUG_12532),y)
> +PLATFORM_RELFLAGS += -fno-optimize-sibling-calls
> +endif
> +endif

Best regards,
Marek Vasut

Patch

diff --git a/arch/arm/config.mk b/arch/arm/config.mk
index 3f4453a..24b9d7c 100644
--- a/arch/arm/config.mk
+++ b/arch/arm/config.mk
@@ -87,3 +87,21 @@  endif
 ifndef CONFIG_NAND_SPL
 LDFLAGS_u-boot += -pie
 endif
+
+#
+# FIXME: binutils versions < 2.22 have a bug in the assembler where
+# branches to weak symbols can be incorrectly optimized in thumb mode
+# to a short branch (b.n instruction) that won't reach when the symbol
+# gets preempted
+#
+# http://sourceware.org/bugzilla/show_bug.cgi?id=12532
+#
+ifeq ($(CONFIG_SYS_THUMB_BUILD),y)
+ifeq ($(GAS_BUG_12532),)
+export GAS_BUG_12532:=$(shell if [ $(call binutils-version) -lt 0222 ] ; \
+	then echo y; else echo n; fi)
+endif
+ifeq ($(GAS_BUG_12532),y)
+PLATFORM_RELFLAGS += -fno-optimize-sibling-calls
+endif
+endif