libucontext/arch/x86/getcontext.S

52 lines
1.5 KiB
ArmAsm

/*
* Copyright (c) 2018 William Pitcock <nenolod@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.
*/
#include "defs.h"
.globl __getcontext;
__getcontext:
/* load address of the ucontext structure */
movl 4(%esp), %eax
/* EAX is not a preserved register */
movl $0, OFFSET_REG_EAX(%eax)
/* copy all of the current registers into the ucontext structure */
movl %ecx, OFFSET_REG_ECX(%eax)
movl %ebx, OFFSET_REG_EBX(%eax)
movl %edx, OFFSET_REG_EDX(%eax)
movl %edi, OFFSET_REG_EDI(%eax)
movl %esi, OFFSET_REG_ESI(%eax)
movl %ebp, OFFSET_REG_EBP(%eax)
/* the first argument on the stack is the jump target (%eip), so we store it in the EIP
register in the ucontext structure. */
movl (%esp), %ecx
movl %ecx, OFFSET_REG_EIP(%eax)
/* take the stack pointer address (%esp) offsetting by 4 to skip over the jump target. */
leal 4(%esp), %ecx
movl %ecx, OFFSET_REG_ESP(%eax)
/* finally, save the FS segment register */
xorl %ecx, %ecx
movw %fs, %cx
movl %ecx, OFFSET_REG_FS(%eax)
/* we're all done here, return 0 */
xorl %eax, %eax
ret
.weak getcontext;
getcontext = __getcontext;