While the above may work, why you don't just follow the procedure call standard instead? Place the value in r0 instead of r10, and you'll have it as the first argument to the function.
there is a reason why I use r10 (and why somebody used r8, I suppose) - I search some address during start.S, and want to stock it in the place that will not be corrupted during continuation of the code in start.S. As you can see, start.S will heavily use r0, r1, probably other low-numbered regs.
Yes, I can put r10 to r0 just before the call of the function (and change signature of start(void) to start(int my_var), is that rght?) but what would this change. If the thisngs work with r10, even better...
And one thing I also noted that is strange a variable of "register volatile". I played around with arm gcc compiler - does this volatile stuff really have some effect? Compiler seems to produce asm code like it is not volatile (optimize by deleting conditions, assign values by add and not mov, etc...)
BR, Drasko
On Mon, Jul 13, 2009 at 3:38 PM, Rabin Vincent rabin@rab.in wrote:
On Fri, Jul 10, 2009 at 02:52:32PM +0200, Drasko DRASKOVIC wrote: [...]
Suppose that I allocated one register in start.S and put in it some data
I
want to have later on C side. From start.S we enter to
start_armboot(void)
function. Would this work :
void start_armboot (void) { init_fnc_t **init_fnc_ptr; char *s; #ifndef CFG_NO_FLASH ulong size; #endif #if defined(CONFIG_VFD) || defined(CONFIG_LCD) unsigned long addr; #endif *#ifdef DATA_FROM_ASM_IN_R10 register volatile unsigned long tmp asm ("r10"); #endif*
/* Pointer is writable since we allocated a register for it */ gd = (gd_t*)(_armboot_start - CFG_MALLOC_LEN - sizeof(gd_t)); /* compiler optimization barrier needed for GCC >= 3.4 */ __asm__ __volatile__("": : :"memory"); memset ((void*)gd, 0, sizeof (gd_t)); gd->bd = (bd_t*)((char*)gd - sizeof(bd_t)); memset (gd->bd, 0, sizeof (bd_t));*#ifdef DATA_FROM_ASM_IN_R10 /* data will be passed to C from assembly start-up in reg r10 */ gd->bd->bi_my_data = tmp; #endif*
[...]
Would I from this point on really have on C stack what I had in r10 in start.S?
If not, does anybody have idea how I can do it?
While the above may work, why you don't just follow the procedure call standard instead? Place the value in r0 instead of r10, and you'll have it as the first argument to the function.
Rabin