7e11c3bf78
Pass the first 4 words on the stack that may have been passed from firmware or bootloader to LK on to lk_main.
73 lines
1.6 KiB
ArmAsm
73 lines
1.6 KiB
ArmAsm
/*
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* Copyright (c) 2021 Travis Geiselbrecht
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*
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* Use of this source code is governed by a MIT-style
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* license that can be found in the LICENSE file or at
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* https://opensource.org/licenses/MIT
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*/
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#include <lk/asm.h>
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.section .text.boot
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FUNCTION(_start)
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// load the first 4 args that were pushed on whatever stack we have
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// NOTE: assumes stack is pointing at at least readable memory
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movl %sp@(4),%d0
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movl %sp@(8),%d1
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movl %sp@(12),%d2
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movl %sp@(16),%d3
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#if ARCH_DO_RELOCATION
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lea %pc@(_start),%a0 // load the current address using PC relative addressing mode
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movl #_start,%a1 // load the same symbol absolutely
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cmpal %a0,%a1
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beqs bss_clear
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// load the end address for loop termination
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movl #_end,%a2
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// copy forwards
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// NOTE: assumes the source and target do not overlap
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0:
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movel %a0@+,%a1@+
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cmpal %a1,%a2
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bne 0b
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// branch to the new location
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movl #bss_clear,%a0
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jmp %a0@
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#endif
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// clear bss
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bss_clear:
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lea __bss_start,%a0
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lea __bss_end,%a1
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cmpl %a0,%a1
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beqs 1f
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// zero 4 bytes at a time
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0:
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clrl %a0@+
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cmpal %a1,%a0
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bne 0b
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1:
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// load the initial stack pointer
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lea _default_stack_top,%sp
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// branch into C land with 4 args off the previous stack
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movl %d3,%sp@-
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movl %d2,%sp@-
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movl %d1,%sp@-
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movl %d0,%sp@-
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jsr lk_main
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// if we return from main just loop forever
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bra .
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END_FUNCTION(_start)
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.bss
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.align 4
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_default_stack_base:
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.skip 4096
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_default_stack_top:
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