summaryrefslogtreecommitdiff
path: root/sysdeps/unix/sysv/linux/x86_64/setcontext.S
blob: b42af8e291eb8302091c4d65e0ce3a175d1cd31b (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
/* Install given context.
   Copyright (C) 2002-2018 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Andreas Jaeger <aj@suse.de>, 2002.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <http://www.gnu.org/licenses/>.  */

#include <sysdep.h>

#include "ucontext_i.h"


/*  int __setcontext (const ucontext_t *ucp)

  Restores the machine context in UCP and thereby resumes execution
  in that context.

  This implementation is intended to be used for *synchronous* context
  switches only.  Therefore, it does not have to restore anything
  other than the PRESERVED state.  */

ENTRY(__setcontext)
	/* Save argument since syscall will destroy it.  */
	pushq	%rdi
	cfi_adjust_cfa_offset(8)

	/* Set the signal mask with
	   rt_sigprocmask (SIG_SETMASK, mask, NULL, _NSIG/8).  */
	leaq	oSIGMASK(%rdi), %rsi
	xorl	%edx, %edx
	movl	$SIG_SETMASK, %edi
	movl	$_NSIG8,%r10d
	movl	$__NR_rt_sigprocmask, %eax
	syscall
	/* Pop the pointer into RDX. The choice is arbitrary, but
	   leaving RDI and RSI available for use later can avoid
	   shuffling values.  */
	popq	%rdx
	cfi_adjust_cfa_offset(-8)
	cmpq	$-4095, %rax		/* Check %rax for error.  */
	jae	SYSCALL_ERROR_LABEL	/* Jump to error handler if error.  */

	/* Restore the floating-point context.  Not the registers, only the
	   rest.  */
	movq	oFPREGS(%rdx), %rcx
	fldenv	(%rcx)
	ldmxcsr oMXCSR(%rdx)


	/* Load the new stack pointer, the preserved registers and
	   registers used for passing args.  */
	cfi_def_cfa(%rdx, 0)
	cfi_offset(%rbx,oRBX)
	cfi_offset(%rbp,oRBP)
	cfi_offset(%r12,oR12)
	cfi_offset(%r13,oR13)
	cfi_offset(%r14,oR14)
	cfi_offset(%r15,oR15)
	cfi_offset(%rsp,oRSP)
	cfi_offset(%rip,oRIP)

	movq	oRSP(%rdx), %rsp
	movq	oRBX(%rdx), %rbx
	movq	oRBP(%rdx), %rbp
	movq	oR12(%rdx), %r12
	movq	oR13(%rdx), %r13
	movq	oR14(%rdx), %r14
	movq	oR15(%rdx), %r15

	/* The following ret should return to the address set with
	getcontext.  Therefore push the address on the stack.  */
	movq	oRIP(%rdx), %rcx
	pushq	%rcx

	movq	oRSI(%rdx), %rsi
	movq	oRDI(%rdx), %rdi
	movq	oRCX(%rdx), %rcx
	movq	oR8(%rdx), %r8
	movq	oR9(%rdx), %r9

	/* Setup finally %rdx.  */
	movq	oRDX(%rdx), %rdx

	/* End FDE here, we fall into another context.  */
	cfi_endproc
	cfi_startproc

	/* Clear rax to indicate success.  */
	xorl	%eax, %eax
	ret
PSEUDO_END(__setcontext)

weak_alias (__setcontext, setcontext)