1/* Save current context and install the given one.
2 Copyright (C) 2002-2017 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Andreas Jaeger <aj@suse.de>, 2002.
5
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Lesser General Public
8 License as published by the Free Software Foundation; either
9 version 2.1 of the License, or (at your option) any later version.
10
11 The GNU C Library is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details.
15
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, see
18 <http://www.gnu.org/licenses/>. */
19
20#include <sysdep.h>
21
22#include "ucontext_i.h"
23
24
25/* int __swapcontext (ucontext_t *oucp, const ucontext_t *ucp);
26
27 Saves the machine context in oucp such that when it is activated,
28 it appears as if __swapcontextt() returned again, restores the
29 machine context in ucp and thereby resumes execution in that
30 context.
31
32 This implementation is intended to be used for *synchronous* context
33 switches only. Therefore, it does not have to save anything
34 other than the PRESERVED state. */
35
36ENTRY(__swapcontext)
37 /* Save the preserved registers, the registers used for passing args,
38 and the return address. */
39 movq %rbx, oRBX(%rdi)
40 movq %rbp, oRBP(%rdi)
41 movq %r12, oR12(%rdi)
42 movq %r13, oR13(%rdi)
43 movq %r14, oR14(%rdi)
44 movq %r15, oR15(%rdi)
45
46 movq %rdi, oRDI(%rdi)
47 movq %rsi, oRSI(%rdi)
48 movq %rdx, oRDX(%rdi)
49 movq %rcx, oRCX(%rdi)
50 movq %r8, oR8(%rdi)
51 movq %r9, oR9(%rdi)
52
53 movq (%rsp), %rcx
54 movq %rcx, oRIP(%rdi)
55 leaq 8(%rsp), %rcx /* Exclude the return address. */
56 movq %rcx, oRSP(%rdi)
57
58 /* We have separate floating-point register content memory on the
59 stack. We use the __fpregs_mem block in the context. Set the
60 links up correctly. */
61 leaq oFPREGSMEM(%rdi), %rcx
62 movq %rcx, oFPREGS(%rdi)
63 /* Save the floating-point environment. */
64 fnstenv (%rcx)
65 stmxcsr oMXCSR(%rdi)
66
67
68 /* The syscall destroys some registers, save them. */
69 movq %rsi, %r12
70
71 /* Save the current signal mask and install the new one with
72 rt_sigprocmask (SIG_BLOCK, newset, oldset,_NSIG/8). */
73 leaq oSIGMASK(%rdi), %rdx
74 leaq oSIGMASK(%rsi), %rsi
75 movl $SIG_SETMASK, %edi
76 movl $_NSIG8,%r10d
77 movl $__NR_rt_sigprocmask, %eax
78 syscall
79 cmpq $-4095, %rax /* Check %rax for error. */
80 jae SYSCALL_ERROR_LABEL /* Jump to error handler if error. */
81
82 /* Restore destroyed registers. */
83 movq %r12, %rsi
84
85 /* Restore the floating-point context. Not the registers, only the
86 rest. */
87 movq oFPREGS(%rsi), %rcx
88 fldenv (%rcx)
89 ldmxcsr oMXCSR(%rsi)
90
91 /* Load the new stack pointer and the preserved registers. */
92 movq oRSP(%rsi), %rsp
93 movq oRBX(%rsi), %rbx
94 movq oRBP(%rsi), %rbp
95 movq oR12(%rsi), %r12
96 movq oR13(%rsi), %r13
97 movq oR14(%rsi), %r14
98 movq oR15(%rsi), %r15
99
100 /* The following ret should return to the address set with
101 getcontext. Therefore push the address on the stack. */
102 movq oRIP(%rsi), %rcx
103 pushq %rcx
104
105 /* Setup registers used for passing args. */
106 movq oRDI(%rsi), %rdi
107 movq oRDX(%rsi), %rdx
108 movq oRCX(%rsi), %rcx
109 movq oR8(%rsi), %r8
110 movq oR9(%rsi), %r9
111
112 /* Setup finally %rsi. */
113 movq oRSI(%rsi), %rsi
114
115 /* Clear rax to indicate success. */
116 xorl %eax, %eax
117 ret
118PSEUDO_END(__swapcontext)
119
120weak_alias (__swapcontext, swapcontext)
121