mirror of
https://github.com/trezor/trezor-firmware.git
synced 2024-11-27 01:48:17 +00:00
95 lines
2.8 KiB
ArmAsm
95 lines
2.8 KiB
ArmAsm
.syntax unified
|
|
|
|
.text
|
|
|
|
.global memset_reg
|
|
.type memset_reg, STT_FUNC
|
|
memset_reg:
|
|
// call with the following (note that the arguments are not validated prior to use):
|
|
// r0 - address of first word to write (inclusive)
|
|
// r1 - address of first word following the address in r0 to NOT write (exclusive)
|
|
// r2 - word value to be written
|
|
// both addresses in r0 and r1 needs to be divisible by 4!
|
|
.L_loop_begin:
|
|
str r2, [r0], 4 // store the word in r2 to the address in r0, post-indexed
|
|
cmp r0, r1
|
|
bne .L_loop_begin
|
|
bx lr
|
|
|
|
.global jump_to
|
|
.type jump_to, STT_FUNC
|
|
jump_to:
|
|
mov r4, r0 // save input argument r0
|
|
// this subroutine re-points the exception handlers before the C code
|
|
// that comprises them has been given a good environment to run.
|
|
// therefore, this code needs to disable interrupts before the VTOR
|
|
// update. then, the reset_handler of the next stage needs to re-enable interrupts.
|
|
// the following prevents activation of all exceptions except Non-Maskable Interrupt (NMI).
|
|
// according to "ARM Cortex-M Programming Guide to Memory Barrier Instructions" Application Note 321, section 4.8:
|
|
// "there is no requirement to insert memory barrier instructions after CPSID".
|
|
cpsid f
|
|
// wipe memory at the end of the current stage of code
|
|
ldr r0, =ccmram_start // r0 - point to beginning of CCMRAM
|
|
ldr r1, =ccmram_end // r1 - point to byte after the end of CCMRAM
|
|
ldr r2, =0 // r2 - the word-sized value to be written
|
|
bl memset_reg
|
|
ldr r0, =sram_start // r0 - point to beginning of SRAM
|
|
ldr r1, =sram_end // r1 - point to byte after the end of SRAM
|
|
ldr r2, =0 // r2 - the word-sized value to be written
|
|
bl memset_reg
|
|
// give the next stage a fresh main stack pointer
|
|
ldr r0, [r4]
|
|
msr msp, r0
|
|
// point to the next stage's exception handlers
|
|
// AN321, section 4.11: "a memory barrier is not required after a VTOR update"
|
|
.set SCB_VTOR, 0xE000ED08 // reference "Cortex-M4 Devices Generic User Guide" section 4.3
|
|
ldr r0, =SCB_VTOR
|
|
str r4, [r0]
|
|
// go on to the next stage
|
|
ldr lr, =0xffffffff // set the link register to reset value. there is no reason to return here.
|
|
ldr r0, [r4, 4]
|
|
ldr r1, =0
|
|
ldr r2, =0
|
|
ldr r3, =0
|
|
ldr r4, =0
|
|
ldr r5, =0
|
|
ldr r6, =0
|
|
ldr r7, =0
|
|
ldr r8, =0
|
|
ldr r9, =0
|
|
ldr r10, =0
|
|
ldr r11, =0
|
|
ldr r12, =0
|
|
bx r0
|
|
|
|
.global shutdown
|
|
.type shutdown, STT_FUNC
|
|
shutdown:
|
|
cpsid f
|
|
ldr r0, =ccmram_start
|
|
ldr r1, =ccmram_end
|
|
ldr r2, =0
|
|
bl memset_reg
|
|
ldr r0, =sram_start
|
|
ldr r1, =sram_end
|
|
ldr r2, =0
|
|
bl memset_reg
|
|
ldr lr, =0xffffffff
|
|
ldr r0, =0
|
|
ldr r1, =0
|
|
ldr r2, =0
|
|
ldr r3, =0
|
|
ldr r4, =0
|
|
ldr r5, =0
|
|
ldr r6, =0
|
|
ldr r7, =0
|
|
ldr r8, =0
|
|
ldr r9, =0
|
|
ldr r10, =0
|
|
ldr r11, =0
|
|
ldr r12, =0
|
|
|
|
b . // loop forever
|
|
|
|
.end
|