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arm: add canboot signature to request handler

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Implement through inline assembly as recommended by Kevin O'Connor.

Signed-off-by:  Eric Callahan <arksine.code@gmail.com>
This commit is contained in:
Eric Callahan 2022-04-25 15:26:02 -04:00
parent 9b4c95ee9a
commit b944d094b3
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GPG Key ID: 7027245FBBDDF59A
1 changed files with 17 additions and 11 deletions
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28
src/generic/armcm_boot.c
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@ -18,7 +18,7 @@ extern uint32_t _stack_end;
* Basic interrupt handlers * Basic interrupt handlers
****************************************************************/ ****************************************************************/
static void __noreturn void __noreturn __visible
reset_handler_stage_two(void) reset_handler_stage_two(void)
{ {
int i; int i;
@ -74,17 +74,23 @@ reset_handler_stage_two(void)
; ;
} }
// Initial code entry point - invoked by the processor after a reset #define CANBOOT_SIGNATURE 0x21746f6f426e6143 // CanBoot!
// Reset interrupts and stack to take control from bootloaders
void
ResetHandler(void)
{
__disable_irq();
// Explicitly load the stack pointer, jump to stage two // Initial code entry point - invoked by the processor after a reset
asm volatile("mov sp, %0\n bx %1" // Reset interrupts and stack to take control from bootloaders. Implemented
: : "r"(&_stack_end), "r"(reset_handler_stage_two)); // Kevin's recommendation.
} asm(".section .text.ResetHandler\n"
".8byte " __stringify(CANBOOT_SIGNATURE) "\n"
".global ResetHandler\n"
".type ResetHandler, %function\n"
"ResetHandler:\n"
" cpsid i\n"
" ldr r3, =_stack_end\n"
" mov sp, r3\n"
" b reset_handler_stage_two\n"
" .pool\n"
);
extern void ResetHandler();
DECL_ARMCM_IRQ(ResetHandler, -15); DECL_ARMCM_IRQ(ResetHandler, -15);
// Code called for any undefined interrupts // Code called for any undefined interrupts