diff options
Diffstat (limited to 'cortex-m-rt/asm.s')
| -rw-r--r-- | cortex-m-rt/asm.s | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/cortex-m-rt/asm.s b/cortex-m-rt/asm.s index 1be4a02..37dedbd 100644 --- a/cortex-m-rt/asm.s +++ b/cortex-m-rt/asm.s @@ -40,3 +40,17 @@ FpuTrampoline: # Hand execution over to `main`. bl main # Note: `main` must not return. `bl` is used only because it has a wider range than `b`. + + # ARMv6-M leaves LR in an unknown state on Reset + # this trampoline sets LR before it's pushed onto the stack by Reset + .section .PreResetTrampoline, "ax" + .global PreResetTrampoline + # .type and .thumb_func are both required; otherwise its Thumb bit does not + # get set and an invalid vector table is generated + .type PreResetTrampoline,%function + .thumb_func +PreResetTrampoline: + # set LR to the initial value used by the ARMv7-M (0xFFFF_FFFF) + ldr r0,=0xffffffff + mov lr,r0 + b Reset |