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make_i386_sysv_elf_gas.S
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/*
Copyright Oliver Kowalke 2009.
Distributed under the Boost Software License, Version 1.0.
(See accompanying file LICENSE_1_0.txt or copy at
http://www.boost.org/LICENSE_1_0.txt)
*/
/****************************************************************************************
* *
* ---------------------------------------------------------------------------------- *
* | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | *
* ---------------------------------------------------------------------------------- *
* | 0x0 | 0x4 | 0x8 | 0xc | 0x10 | 0x14 | 0x18 | 0x1c | *
* ---------------------------------------------------------------------------------- *
* | fc_mxcsr|fc_x87_cw| guard | EDI | ESI | EBX | EBP | EIP | *
* ---------------------------------------------------------------------------------- *
* ---------------------------------------------------------------------------------- *
* | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | *
* ---------------------------------------------------------------------------------- *
* | 0x20 | 0x24 | 0x28 | | *
* ---------------------------------------------------------------------------------- *
* | hidden | to | data | | *
* ---------------------------------------------------------------------------------- *
* *
****************************************************************************************/
.file "make_i386_sysv_elf_gas.S"
.text
.globl make_fcontext
.align 2
.type make_fcontext,@function
make_fcontext:
/* first arg of make_fcontext() == top of context-stack */
movl 0x4(%esp), %eax
/* reserve space for first argument of context-function
eax might already point to a 16byte border */
leal -0x8(%eax), %eax
/* shift address in EAX to lower 16 byte boundary */
andl $-16, %eax
/* reserve space for context-data on context-stack, and align the stack */
leal -0x34(%eax), %eax
/* third arg of make_fcontext() == address of context-function */
/* stored in EBX */
movl 0xc(%esp), %ecx
movl %ecx, 0x14(%eax)
/* save MMX control- and status-word */
stmxcsr (%eax)
/* save x87 control-word */
fnstcw 0x4(%eax)
#if defined(BOOST_CONTEXT_TLS_STACK_PROTECTOR)
/* save stack guard */
movl %gs:0x14, %ecx /* read stack guard from TLS record */
movl %ecx, 0x8(%eax) /* save stack guard */
#endif
/* return transport_t */
/* FCTX == EDI, DATA == ESI */
leal 0xc(%eax), %ecx
movl %ecx, 0x20(%eax)
/* compute abs address of label trampoline */
call 1f
/* address of trampoline 1 */
1: popl %ecx
/* compute abs address of label trampoline */
addl $trampoline-1b, %ecx
/* save address of trampoline as return address */
/* will be entered after calling jump_fcontext() first time */
movl %ecx, 0x1c(%eax)
/* compute abs address of label finish */
call 2f
/* address of label 2 */
2: popl %ecx
/* compute abs address of label finish */
addl $finish-2b, %ecx
/* save address of finish as return-address for context-function */
/* will be entered after context-function returns */
movl %ecx, 0x18(%eax)
ret /* return pointer to context-data */
trampoline:
/* move transport_t for entering context-function */
movl %edi, (%esp)
movl %esi, 0x4(%esp)
pushl %ebp
/* jump to context-function */
jmp *%ebx
finish:
call 3f
/* address of label 3 */
3: popl %ebx
/* compute address of GOT and store it in EBX */
addl $_GLOBAL_OFFSET_TABLE_+[.-3b], %ebx
/* exit code is zero */
xorl %eax, %eax
movl %eax, (%esp)
/* exit application */
call _exit@PLT
hlt
.size make_fcontext,.-make_fcontext
/* Mark that we don't need executable stack. */
.section .note.GNU-stack,"",%progbits