SVC32 and SP

[Sascha Hauer]

On Mon, May 21, 2012 at 09:31:51PM +0200, Carlo Caione wrote:
> On Fri, May 18, 2012 at 11:41 AM, Sascha Hauer <s.hauer at pengutronix.de> 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()

Ok, thanks for testing. I'll prepare a patch for this

Sascha


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