import less(1)
[unleashed/tickless.git] / usr / src / lib / libc / amd64 / sys / getcontext.s
blobbccbf79628d3ea03dc1f83079907d9efc5abe7e1
1 /*
2 * CDDL HEADER START
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
19 * CDDL HEADER END
23 * Copyright 2008 Sun Microsystems, Inc. All rights reserved.
24 * Use is subject to license terms.
27 .file "getcontext.s"
29 #include <sys/asm_linkage.h>
31 ANSI_PRAGMA_WEAK(getcontext,function)
32 ANSI_PRAGMA_WEAK(swapcontext,function)
34 #include "SYS.h"
35 #include <../assym.h>
38 * getcontext() is written in assembler since it has to capture the correct
39 * machine state of the calle.
41 * As swapcontext() is actually equivalent to getcontext() + setcontext(),
42 * swapcontext() shares the most code with getcontext().
45 #define GETCONTEXT_IMPL(offset) \
46 pushq %rdi; /* preserve the ucontext_t pointer */ \
47 call __getcontext; \
48 /* call getcontext: syscall */ \
49 popq %rdx; \
50 andl %eax, %eax; /* if (error_return_from_syscall) */ \
51 je 1f; \
52 addq $offset, %rsp; \
53 ret; /* then just return */ \
54 1: \
55 /* \
56 * fix up %rsp and %rip \
57 */ \
58 addq $UC_MCONTEXT_GREGS, %rdx; \
59 /* &ucp->uc_mcontext.gregs */ \
60 movq offset+0(%rsp), %rax; \
61 /* read return PC from stack */ \
62 movq %rax, RIP_OFF (%rdx); \
63 /* store ret PC in EIP of env var */ \
64 leaq offset+8(%rsp), %rax; \
65 /* get caller's sp at time of call */ \
66 movq %rax, RSP_OFF (%rdx); \
67 /* store the sp into UESP of env var */ \
68 xorq %rax, %rax; /* return 0 */ \
69 movq %rax, RAX_OFF (%rdx); \
70 /* getcontext returns 0 after setcontext */
72 /*
73 * getcontext(ucontext_t *ucp)
76 ENTRY(getcontext)
77 GETCONTEXT_IMPL(0)
78 ret
79 SET_SIZE(getcontext)
82 * swapcontext(ucontext_t *oucp, const ucontext_t *ucp)
85 ENTRY(swapcontext)
86 pushq %rsi /* preserve the 2nd argument */
88 GETCONTEXT_IMPL(8)
90 /* call setcontext */
91 popq %rdi
92 call setcontext
93 ret
94 SET_SIZE(swapcontext)