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authorDave Martin <dave.martin@linaro.org>2011-03-03 05:41:12 -0500
committerRussell King <rmk+kernel@arm.linux.org.uk>2011-03-10 11:49:06 -0500
commit6f685c5cdd29649cf8cc8f57c72791159f936e07 (patch)
tree892575c8f378609771752e12e88d4f2699084c70 /arch/arm/Makefile
parent23bfdacf4eb525ff3404161429cedaa281c23e47 (diff)
ARM: 6781/1: Thumb-2: Work around buggy Thumb-2 short branch relocations in gas
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. This patch adds a new CONFIG_THUMB2_AVOID_R_ARM_THM_JUMP11 config option which adds -fno-optimize-sibling-calls to CFLAGS_MODULE when building a Thumb-2 kernel. Signed-off-by: Dave Martin <dave.martin@linaro.org> Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm/Makefile')
-rw-r--r--arch/arm/Makefile4
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index da525bc96145..6d611f407ce6 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -105,6 +105,10 @@ AFLAGS_AUTOIT :=$(call as-option,-Wa$(comma)-mimplicit-it=always,-Wa$(comma)-mau
105AFLAGS_NOWARN :=$(call as-option,-Wa$(comma)-mno-warn-deprecated,-Wa$(comma)-W) 105AFLAGS_NOWARN :=$(call as-option,-Wa$(comma)-mno-warn-deprecated,-Wa$(comma)-W)
106CFLAGS_THUMB2 :=-mthumb $(AFLAGS_AUTOIT) $(AFLAGS_NOWARN) 106CFLAGS_THUMB2 :=-mthumb $(AFLAGS_AUTOIT) $(AFLAGS_NOWARN)
107AFLAGS_THUMB2 :=$(CFLAGS_THUMB2) -Wa$(comma)-mthumb 107AFLAGS_THUMB2 :=$(CFLAGS_THUMB2) -Wa$(comma)-mthumb
108# Work around buggy relocation from gas if requested:
109ifeq ($(CONFIG_THUMB2_AVOID_R_ARM_THM_JUMP11),y)
110CFLAGS_MODULE +=-fno-optimize-sibling-calls
111endif
108endif 112endif
109 113
110# Need -Uarm for gcc < 3.x 114# Need -Uarm for gcc < 3.x