libucontext/arch/mips/makecontext.S

102 lines
2.2 KiB
ArmAsm

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