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/*
* Copyright (c) 2017-2018 Richard Braun.
* Copyright (c) 2017 Jerko Lenstra.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*/
#include "asm.h"
#include "boot.h"
#include "cpu.h"
/*
* Put the following instructions into the .text section, which is
* allocatable and executable.
*/
.section .text, "ax"
/*
* This symbol is the entry point, i.e. the first instruction that should
* be run when control is passed to the kernel. The address of this symbol
* is what the following command returns :
* readelf -aW x1 | grep "Entry point"
*/
ASM_FUNC(boot_start)
mov %r0, %r13 /* load boot stack in PSP */
msr psp, %r0
mov %r0, $2 /* use PSP as stack pointer */
msr control, %r0
isb /* force CONTROL register evaluation,
i.e. R13 is now PSP */
ldr %r0, =cpu_exc_stack /* load exception stack in MSP */
add %r0, %r0, CPU_EXC_STACK_SIZE
msr msp, %r0
bl boot_clear_bss /* boot_clear_bss() */
b boot_main /* goto boot_main */
/*
* Clear the .bss section.
*
* The stack, being part of the .bss section, must not be used to save
* data, since that data will be cleared.
*/
ASM_FUNC(boot_clear_bss) /* void */
mov %r0, #0 /* boot_clear_bss(void) */
ldr %r1, =_bss_start /* { */
ldr %r2, =_bss_end /* uint32_t *r1 = &_bss_start; */
/* uint32_t *r2 = &_bss_end; */
1:
cmp %r1, %r2 /* while (r1 < r2) { */
it hs /* *r1 = 0; */
bxhs %r14 /* r1++; */
str %r0, [%r1] /* } */
add %r1, %r1, #4 /* } */
b 1b
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