Hi Albert,
On Tuesday 07 February 2012 02:36 AM, Albert ARIBAUD wrote:
Le 06/02/2012 12:37, Aneesh V a écrit :
When U-Boot/SPL is built using the Thumb instruction set the
toolchain has a potential issue with weakly linked symbols.
If a function has a weakly linked default implementation in C
and a real implementation in assembly GCC is confused about the
instruction set of the assembly implementation. As a result
the assembly function that is built in ARM is executed as
if it is Thumb. This results in a crash.
We need to investigate further to see if this is a toolchain
issue or an issue with our usage of it. In the meanwhile, we
can workaround the issue by having both the weakly linked alias
and the real implementation in C.
I would tend to NAK a patch submission where an issue is known and
investigation is considered but is actually bypassed by a workaround.
These tend to turn from 'temporary fix' to 'old crust' with time,
because there is no incentive for a better solution when the quick fix
"works, after all".
I have a solution to this problem now. The following change solves it.
diff --git a/arch/arm/cpu/armv7/omap-common/lowlevel_init.S
b/arch/arm/cpu/armv7/omap-common/lowlevel_init.S
index 35f38ac..177af7a 100644
--- a/arch/arm/cpu/armv7/omap-common/lowlevel_init.S
+++ b/arch/arm/cpu/armv7/omap-common/lowlevel_init.S
@@ -28,6 +28,7 @@
#include <asm/arch/omap.h>
+.type save_boot_params, %function
.global save_boot_params
save_boot_params:
/*
Apparently having the symbol marked as %function type in the symbol
table helps ld. However, not having the %function tag doesn't prevent
ld from linking correctly to this function. It affects only ARM/Thumb
resolution. Strange!
I came to this solution from the test-code provided by Ulrich Weigand
in reply to my queries in Linaro ML [1]. I couldn't reproduce the
problem with his code, but eventually could break it when I removed
the %function.
I will continue this discussion there and to understand whether this is
a limitation with GCC.
However, hope you are fine with the above solution. I shall fix up all
assembly functions in arm.
[1] http://article.gmane.org/gmane.linux.linaro.devel/3073
br,
Aneesh
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