102 lines
2.2 KiB
ArmAsm
102 lines
2.2 KiB
ArmAsm
/*
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* Copyright (c) 2020 Ariadne Conill <ariadne@dereferenced.org>
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*
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* Permission to use, copy, modify, and/or distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* This software is provided 'as is' and without any warranty, express or
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* implied. In no event shall the authors be liable for any damages arising
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* from the use of this software.
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*/
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LOCALSZ = 2
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#include "defs.h"
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A3_OFF = FRAMESZ + (3 * REG_SZ)
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/*
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* Because we have to fiddle with $gp, we have to implement this in
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* assembly rather than C. Annoying, that...
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*/
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ALIAS(makecontext, libucontext_makecontext)
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ALIAS(__makecontext, libucontext_makecontext)
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FUNC(libucontext_makecontext)
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PUSH_FRAME(libucontext_makecontext)
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/* store $a3 through $a7 to the stack frame. */
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sw $a3, A3_OFF($sp)
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/* set $zero in the mcontext to 1. */
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li $v0, 1
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sw $v0, REG_OFFSET(0)($a0)
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/* ensure the stack is aligned on a quad-word boundary. */
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lw $t0, UCONTEXT_STACK_PTR($a0)
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lw $t2, UCONTEXT_STACK_SIZE($a0)
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addiu $t1, $sp, A3_OFF
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addu $t0, $t2
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and $t0, ALMASK
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blez $a2, no_more_arguments
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/* store register arguments. */
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addiu $t2, $a0, MCONTEXT_GREGS + (4 * REG_SZ)
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move $t3, $zero
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store_register_arg:
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addiu $t3, 1
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lw $v1, ($t1)
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addiu $t1, REG_SZ
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sw $v1, ($t2)
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addiu $t2, REG_SZ
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bgeu $t3, $a2, no_more_arguments
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bltu $t3, 4, store_register_arg
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/* make room for stack arguments. */
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subu $t2, $a2, $t3
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sll $t2, 3
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subu $t0, $t2
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and $t0, ALMASK
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/* store stack arguments. */
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move $t2, $t0
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store_stack_arg:
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addiu $t3, 1
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lw $v1, ($t1)
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addiu $t1, REG_SZ
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sw $v1, ($t2)
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addiu $t2, REG_SZ
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bltu $t3, $a2, store_stack_arg
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no_more_arguments:
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/* make room for $a0-$a3 storage */
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addiu $t0, -(4 * REG_SZ)
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/* trampoline setup. */
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la $t9, libucontext_trampoline
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/* copy link pointer as $s0... */
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lw $v1, UCONTEXT_UC_LINK($a0)
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sw $v1, REG_OFFSET(16)($a0)
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/* set our $sp */
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sw $t0, REG_OFFSET(29)($a0)
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/* $gp is copied as $s1 */
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sw $gp, REG_OFFSET(17)($a0)
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/* set our $ra */
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sw $t9, REG_OFFSET(31)($a0)
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/* set our $pc */
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sw $a1, MCONTEXT_PC($a0)
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POP_FRAME(libucontext_makecontext)
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jr $ra
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END(libucontext_makecontext)
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