libucontext/arch/mips64/makecontext.S

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2020-03-29 12:05:52 +00:00
/*
* 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.
*/
/* $gp + 5 args */
LOCALSZ = 6
#include "defs.h"
A3_OFF = FRAMESZ - (5 * REG_SZ)
A4_OFF = FRAMESZ - (4 * REG_SZ)
A5_OFF = FRAMESZ - (3 * REG_SZ)
A6_OFF = FRAMESZ - (2 * REG_SZ)
A7_OFF = FRAMESZ - (1 * REG_SZ)
/*
* Because we have to fiddle with $gp, we have to implement this in
* assembly rather than C. Annoying, that...
*/
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ALIAS(makecontext, __makecontext)
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FUNC(__makecontext)
PUSH_FRAME(__makecontext)
/* store $a3 through $a7 to the stack frame. */
sd $a3, A3_OFF($sp)
sd $a4, A4_OFF($sp)
sd $a5, A5_OFF($sp)
sd $a6, A6_OFF($sp)
sd $a7, A7_OFF($sp)
/* set $zero in the mcontext to 1. */
li $v0, 1
sd $v0, ((0 * REG_SZ) + MCONTEXT_GREGS)($a0)
/* ensure the stack is aligned on a quad-word boundary. */
ld $t0, UCONTEXT_STACK_PTR($a0)
ld $t2, UCONTEXT_STACK_SIZE($a0)
daddiu $t1, $sp, A3_OFF
daddu $t0, $t2
and $t0, ALMASK
blez $a2, no_more_arguments
/* store register arguments. */
daddiu $t2, $a0, MCONTEXT_GREGS + (4 * REG_SZ)
move $t3, $zero
store_register_arg:
daddiu $t3, 1
ld $v1, ($t1)
daddiu $t1, REG_SZ
sd $v1, ($t2)
daddiu $t2, REG_SZ
bgeu $t3, $a2, no_more_arguments
bltu $t3, 8, store_register_arg
/* make room for stack arguments. */
dsubu $t2, $a2, $t3
dsll $t2, 3
dsubu $t0, $t2
and $t0, ALMASK
/* store stack arguments. */
move $t2, $t0
store_stack_arg:
daddiu $t3, 1
ld $v1, ($t1)
daddiu $t1, REG_SZ
sd $v1, ($t2)
daddiu $t2, REG_SZ
bltu $t3, $a2, store_stack_arg
no_more_arguments:
/* trampoline setup. */
dla $t9, __start_context
/* copy link pointer as $s0... */
ld $v1, UCONTEXT_UC_LINK($a0)
sd $v1, ((16 * REG_SZ) + MCONTEXT_GREGS)($a0)
/* set our $sp */
sd $t0, ((29 * REG_SZ) + MCONTEXT_GREGS)($a0)
/* $gp is copied as $s1 */
sd $gp, ((17 * REG_SZ) + MCONTEXT_GREGS)($a0)
/* set our $ra */
sd $t9, ((31 * REG_SZ) + MCONTEXT_GREGS)($a0)
/* set our $pc */
sd $a1, MCONTEXT_PC($a0)
POP_FRAME(__makecontext)
jr $ra
END(__makecontext)