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mirror of https://github.com/trezor/trezor-firmware.git synced 2024-11-18 13:38:12 +00:00
trezor-firmware/startup.s
Jochen Hoenicke 98e617d874
startup: use custom reset_handler
+ group confidential data in one place
+ zero all SRAM where needed
2017-08-16 13:52:01 +02:00

40 lines
1.1 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 reset_handler
.type reset_handler, STT_FUNC
reset_handler:
ldr r0, =_ram_start // r0 - point to beginning of SRAM
ldr r1, =_ram_end // r1 - point to byte after the end of SRAM
ldr r2, =0 // r2 - the byte-sized value to be written
bl memset_reg
// copy .data section from flash to SRAM
ldr r0, =_data // dst addr
ldr r1, =_data_loadaddr // src addr
ldr r2, =_data_size // length in bytes
bl memcpy
// enter the application code
bl main
// loop forever if the application code returns
b .
.end