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trezor-firmware/core/embed/reflash/startup_stm32u5.s

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ArmAsm
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.syntax unified
.text
.global reset_handler
.type reset_handler, STT_FUNC
reset_handler:
// set the stack protection
ldr r0, =_sstack
add r0, r0, #16 // padding
msr MSPLIM, r0
// setup environment for subsequent stage of code
ldr r2, =0 // r2 - the word-sized value to be written
ldr r0, =sram1_start // r0 - point to beginning of SRAM
ldr r1, =sram1_end // r1 - point to byte after the end of SRAM
bl memset_reg
ldr r0, =sram2_start // r0 - point to beginning of SRAM
ldr r1, =sram2_end // r1 - point to byte after the end of SRAM
bl memset_reg
ldr r0, =sram4_start // r0 - point to beginning of SRAM
ldr r1, =sram4_end // r1 - point to byte after the end of SRAM
bl memset_reg
ldr r0, =sram6_start // r0 - point to beginning of SRAM
ldr r1, =sram6_end // r1 - point to byte after the end of SRAM
bl memset_reg
ldr r0, =boot_args_start // r0 - point to beginning of boot args
ldr r1, =boot_args_end // r1 - point to byte after the end of boot args
bl memset_reg
ldr r0, =sram3_start // r0 - point to beginning of SRAM
ldr r1, =__fb_start // r1 - point to beginning of framebuffer
bl memset_reg
ldr r0, =__fb_end // r0 - point to end of framebuffer
ldr r1, =sram5_end // r1 - point to byte after the end of SRAM
bl memset_reg
// copy data in from flash
ldr r0, =data_vma // dst addr
ldr r1, =data_lma // src addr
ldr r2, =data_size // size in bytes
bl memcpy
// copy confidential data in from flash
ldr r0, =confidential_vma // dst addr
ldr r1, =confidential_lma // src addr
ldr r2, =confidential_size // size in bytes
bl memcpy
// setup the stack protector (see build script "-fstack-protector-all") with an unpredictable value
bl rng_get
ldr r1, = __stack_chk_guard
str r0, [r1]
// re-enable exceptions
// according to "ARM Cortex-M Programming Guide to Memory Barrier Instructions" Application Note 321, section 4.7:
// "If it is not necessary to ensure that a pended interrupt is recognized immediately before
// subsequent operations, it is not necessary to insert a memory barrier instruction."
cpsie f
// enter the application code
bl main
b shutdown_privileged
.end