Hi Ulrich,
On Tuesday 15 March 2011 09:00 PM, Ulrich Weigand wrote:
Aneesh V<ane...@ti.com> wrote:
I was trying to build u-boot in Thumb2 for OMAP4. Everything was fine
until I added some patches recently. One of these patches introduced an
API (let's say foo()) that has a weakly linked alias(let's say
__foo()) and a strongly linked implementation(the real foo()) in an
assembly file.
Although I give -mthumb and -mthumb-interwork for all the files,
apparently GCC generates ARM code for assembly files. In the final
image foobar() calls foo() using a BL. Since foobar() is in Thumb and
foo() in ARM, it ends up crashing. Looks like foobar() assumed foo()
to be Thumb because __foo() is Thumb.
I'm unable to reproduce this. Do you have a complete test case?
Thank you for looking into this problem.
I've tried with the following small example:
foo1.c:
extern void foo (void) __attribute__ ((weak, alias ("__foo")));
void __foo (void)
{
}
int main (void)
{
foo ();
}
foo2.S:
.text
.align 2
.global foo
.type foo, %function
foo:
push {r7}
add r7, sp, #0
mov sp, r7
pop {r7}
bx lr
.size foo, .-foo
Can you try this sequence:
arm-linux-gnueabi-gcc -march=armv7-a -mthumb -mthumb-interwork -o foo1.o
foo1.c -c
arm-linux-gnueabi-gcc -march=armv7-a -mthumb -mthumb-interwork -o foo2.o
foo2.S -c
arm-linux-gnueabi-ld -r foo1.o foo2.o
arm-linux-gnueabi-objdump -S a.out
With this sequence I get the following output:
00000000 <__foo>:
0: b480 push {r7}
2: af00 add r7, sp, #0
4: 46bd mov sp, r7
6: bc80 pop {r7}
8: 4770 bx lr
a: bf00 nop
0000000c <main>:
c: b580 push {r7, lr}
e: af00 add r7, sp, #0
10: f7ff fffe bl 18 <foo>
14: 4618 mov r0, r3
16: bd80 pop {r7, pc}
00000018 <foo>:
18: e92d0080 push {r7}
1c: e28d7000 add r7, sp, #0
20: e1a0d007 mov sp, r7
24: e8bd0080 pop {r7}
28: e12fff1e bx lr
When building just "gcc foo1.c", I get:
0000835c<__foo>:
835c: b480 push {r7}
835e: af00 add r7, sp, #0
8360: 46bd mov sp, r7
8362: bc80 pop {r7}
8364: 4770 bx lr
8366: bf00 nop
00008368<main>:
8368: b580 push {r7, lr}
836a: af00 add r7, sp, #0
836c: f7ff fff6 bl 835c<__foo>
8370: 4618 mov r0, r3
8372: bd80 pop {r7, pc}
When building both files "gcc foo1.c foo2.S", I get instead:
00008368<main>:
8368: b580 push {r7, lr}
836a: af00 add r7, sp, #0
836c: f000 e802 blx 8374<foo>
8370: 4618 mov r0, r3
8372: bd80 pop {r7, pc}
00008374<foo>:
8374: e92d0080 push {r7}
8378: e28d7000 add r7, sp, #0
837c: e1a0d007 mov sp, r7
8380: e8bd0080 pop {r7}
8384: e12fff1e bx lr
So it seems to me the linker is handling this correctly ...
(This is on Ubuntu Natty using system gcc and binutils.)
Mit freundlichen Gruessen / Best Regards
Ulrich Weigand
--
Dr. Ulrich Weigand | Phone: +49-7031/16-3727
STSM, GNU compiler and toolchain for Linux on System z and Cell/B.E.
IBM Deutschland Research& Development GmbH
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