Le 30/11/2010 09:35, Andreas Bießmann a écrit :
Dear Albert ARIBAUD,
Am 30.11.2010 09:22, schrieb Albert ARIBAUD:
Le 30/11/2010 08:06, Andreas Bießmann a écrit :
r8 is used for gd and should therefore be left alone
I'm surprised that this did not break things so far... Whatever value r8 ended with was used as the address of GD.
Well r8 is set in arch/arm/include/asm/global_data.h
---8<--- #define DECLARE_GLOBAL_DATA_PTR register volatile gd_t *gd asm ("r8") --->8---
The GD is then later on allocated in board_init_f
---8<--- /* Pointer is writable since we allocated a register for it */ gd = (gd_t *) (CONFIG_SYS_INIT_SP_ADDR); /* compiler optimization barrier needed for GCC>= 3.4 */ __asm__ __volatile__("": : :"memory");
memset ((void*)gd, 0, sizeof (gd_t)); --->8---
... which is why I could not find "r8" allocation :) ... Thanks. So yes, we need to keep r8, and yes, we were lucky that the start.S code did run at all with a corrupted r8 -- fixing that may remove some weird behaviors we could see,
Can you do a pass on other ARM archs which must be fixed too?
I'd like to see a less ambiguous comment here, but I'm not sure what's best. Any suggestions?
Not currently, this was just slipped in by fast preperation of that patch.
fixnext:
- str r1, [r0]
- str r1, [r0] /* store back content of r1 */
Nak. This comment paraphrases the instruction.
dito
I'd rather have no comment than a paraphrase of the code, but I'd rather have an imperfect yet at least partly helpful comment than no comment at all for assembly language code.
regards
Andreas Bießmann
Amicalement,