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trezor-firmware/legacy/firmware/startup.S

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.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:
// We need to perform VTOR setup case an old bootloader (<1.8.0)
// is starting the new firmware, these will be set incorrectly.
// To make development easier, set only if we are in privileged
// mode. This resolves annoying combinations of PRODUCTION
// settings for bootloader and FW.
// Normally only signed firmware will let bootloader start FW
// in privileged mode (PRODUCTION=1 variants with signed everything).
// But with devel bootloader we let FW start in privileged mode
// and let's do the check if we can set VTOR without fault
// These two instructions are just for debug testing how unprivileged
// FW is handled
//mov r0, 1
//msr control, r0 // set unprivileged
ldr sp, =_stack // setup stack
// are we privileged? if so, fix VTOR, otherwise skip
mrs r3, control
and r3, r3, #1
cmp r3, #1
beq .setup_as_unprivileged
ldr r0, =0xE000ED08 // r0 = VTOR address
ldr r1, =0x08010400 // r1 = FLASH_APP_START
str r1, [r0] // assign
dsb
isb
.setup_as_unprivileged:
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
// shutdown if the application code returns
b shutdown
.global shutdown
.type shutdown, STT_FUNC
shutdown:
cpsid f
ldr r0, =0
mov r1, r0
mov r2, r0
mov r3, r0
mov r4, r0
mov r5, r0
mov r6, r0
mov r7, r0
mov r8, r0
mov r9, r0
mov r10, r0
mov r11, r0
mov r12, r0
ldr lr, =0xffffffff
ldr r0, =_ram_start
ldr r1, =_ram_end
// set to value in r2
bl memset_reg
b . // loop forever
.ltorg // dump literal pool (for the ldr ...,=... commands above)
.global sv_call_handler
.type sv_call_handler, STT_FUNC
sv_call_handler:
tst lr, #4
ite eq
mrseq r0, msp
mrsne r0, psp
b svc_handler_main
.end