SVC32 and SP

Carlo Caione carlo.caione at
Mon May 21 15:31:51 EDT 2012

On Fri, May 18, 2012 at 11:41 AM, Sascha Hauer <s.hauer at> wrote:
> On Fri, May 18, 2012 at 12:06:00AM +0200, Carlo Caione wrote:
>> Hi,
>> I was debugging the problem with barebox and qemu-linaro as I
>> described in a previous post.
>> This is what I have discovered.
>> The problem is in the strlen function that seems to get corrupted
>> runtime during barebox initialization. The problem seems related to
>> the switch to SVC32 mode together with the __mmu_cache_flush
>> implementation.
>> Before setting the cpu to SVC32 mode, the Stack Pointer is correctly
>> set to 0x4020fcb0, but, immediately after the writing in the cpsr
>> register (__asm__ __volatile__("msr cpsr, %0" : : "r"(r));) the Stack
>> Pointer (now R13_SVC) is in 0x40205cb0 that is in the middle of the
>> .text section (and precisely in the middle of the strlen routine).
>> The problem is that in the __mmu_cache_flush disassembly I have a huge
>> push {r0, r1, r2, r3, r4, r5, r6, r7, r9, r10, r11} that overwrites
>> the strlen function and corrupts the code.
> Can you try and remove the call to __mmu_cache_flush in start.c?

Everything is fine if I comment out __mmu_cache_flush()

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