1 /* Save current context.
2 Copyright (C) 2002-2019 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Andreas Jaeger <aj@suse.de>, 2002.
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.
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.
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/>. */
21 #include <asm/prctl.h>
23 #include "ucontext_i.h"
25 /* int __getcontext (ucontext_t *ucp)
27 Saves the machine context in UCP such that when it is activated,
28 it appears as if __getcontext() returned again.
30 This implementation is intended to be used for *synchronous* context
31 switches only. Therefore, it does not have to save anything
32 other than the PRESERVED state. */
36 /* Save the preserved registers, the registers used for passing
37 args, and the return address. */
54 leaq 8(%rsp), %rcx /* Exclude the return address. */
58 /* Check if shadow stack is enabled. */
59 testl $X86_FEATURE_1_SHSTK, %fs:FEATURE_1_OFFSET
62 /* Save RDI in RDX which won't be clobbered by syscall. */
66 cmpq %fs:SSP_BASE_OFFSET, %rax
67 jnz L(shadow_stack_bound_recorded)
69 /* Get the base address and size of the default shadow stack
70 which must be the current shadow stack since nothing has
74 movl $ARCH_CET_STATUS, %edi
75 movl $__NR_arch_prctl, %eax
80 /* This should never happen. */
84 /* Record the base of the current shadow stack. */
86 movq %rax, %fs:SSP_BASE_OFFSET
92 L(shadow_stack_bound_recorded):
93 /* Get the current shadow stack pointer. */
95 /* NB: Save the caller's shadow stack so that we can jump back
96 to the caller directly. */
100 /* Save the current shadow stack base in ucontext. */
101 movq %fs:SSP_BASE_OFFSET, %rax
102 movq %rax, (oSSP + 8)(%rdi)
106 /* We have separate floating-point register content memory on the
107 stack. We use the __fpregs_mem block in the context. Set the
108 links up correctly. */
110 leaq oFPREGSMEM(%rdi), %rcx
111 movq %rcx, oFPREGS(%rdi)
112 /* Save the floating-point environment. */
117 /* Save the current signal mask with
118 rt_sigprocmask (SIG_BLOCK, NULL, set,_NSIG/8). */
119 leaq oSIGMASK(%rdi), %rdx
124 movl $SIG_BLOCK, %edi
127 movl $__NR_rt_sigprocmask, %eax
129 cmpq $-4095, %rax /* Check %rax for error. */
130 jae SYSCALL_ERROR_LABEL /* Jump to error handler if error. */
132 /* All done, return 0 for success. */
135 PSEUDO_END(__getcontext)
137 weak_alias (__getcontext, getcontext)