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3cf01adb | 1 | /* Save current context. |
04277e02 | 2 | Copyright (C) 2002-2019 Free Software Foundation, Inc. |
3cf01adb AJ |
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 | |
59ba27a6 | 17 | License along with the GNU C Library; if not, see |
5a82c748 | 18 | <https://www.gnu.org/licenses/>. */ |
3cf01adb AJ |
19 | |
20 | #include <sysdep.h> | |
25123a1c | 21 | #include <asm/prctl.h> |
3cf01adb AJ |
22 | |
23 | #include "ucontext_i.h" | |
24 | ||
25 | /* int __getcontext (ucontext_t *ucp) | |
26 | ||
27 | Saves the machine context in UCP such that when it is activated, | |
28 | it appears as if __getcontext() returned again. | |
29 | ||
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. */ | |
33 | ||
34 | ||
35 | ENTRY(__getcontext) | |
c816e074 AJ |
36 | /* Save the preserved registers, the registers used for passing |
37 | args, and the return address. */ | |
3cf01adb AJ |
38 | movq %rbx, oRBX(%rdi) |
39 | movq %rbp, oRBP(%rdi) | |
40 | movq %r12, oR12(%rdi) | |
41 | movq %r13, oR13(%rdi) | |
42 | movq %r14, oR14(%rdi) | |
43 | movq %r15, oR15(%rdi) | |
44 | ||
c816e074 AJ |
45 | movq %rdi, oRDI(%rdi) |
46 | movq %rsi, oRSI(%rdi) | |
47 | movq %rdx, oRDX(%rdi) | |
48 | movq %rcx, oRCX(%rdi) | |
49 | movq %r8, oR8(%rdi) | |
50 | movq %r9, oR9(%rdi) | |
51 | ||
3cf01adb AJ |
52 | movq (%rsp), %rcx |
53 | movq %rcx, oRIP(%rdi) | |
54 | leaq 8(%rsp), %rcx /* Exclude the return address. */ | |
55 | movq %rcx, oRSP(%rdi) | |
56 | ||
25123a1c L |
57 | #if SHSTK_ENABLED |
58 | /* Check if shadow stack is enabled. */ | |
59 | testl $X86_FEATURE_1_SHSTK, %fs:FEATURE_1_OFFSET | |
60 | jz L(no_shstk) | |
61 | ||
62 | /* Save RDI in RDX which won't be clobbered by syscall. */ | |
63 | movq %rdi, %rdx | |
64 | ||
65 | xorl %eax, %eax | |
66 | cmpq %fs:SSP_BASE_OFFSET, %rax | |
67 | jnz L(shadow_stack_bound_recorded) | |
68 | ||
69 | /* Get the base address and size of the default shadow stack | |
70 | which must be the current shadow stack since nothing has | |
71 | been recorded yet. */ | |
72 | sub $24, %RSP_LP | |
73 | mov %RSP_LP, %RSI_LP | |
74 | movl $ARCH_CET_STATUS, %edi | |
75 | movl $__NR_arch_prctl, %eax | |
76 | syscall | |
77 | testq %rax, %rax | |
78 | jz L(continue_no_err) | |
79 | ||
80 | /* This should never happen. */ | |
81 | hlt | |
82 | ||
83 | L(continue_no_err): | |
84 | /* Record the base of the current shadow stack. */ | |
85 | movq 8(%rsp), %rax | |
86 | movq %rax, %fs:SSP_BASE_OFFSET | |
87 | add $24, %RSP_LP | |
88 | ||
89 | /* Restore RDI. */ | |
90 | movq %rdx, %rdi | |
91 | ||
92 | L(shadow_stack_bound_recorded): | |
93 | /* Get the current shadow stack pointer. */ | |
94 | rdsspq %rax | |
95 | /* NB: Save the caller's shadow stack so that we can jump back | |
96 | to the caller directly. */ | |
97 | addq $8, %rax | |
98 | movq %rax, oSSP(%rdx) | |
99 | ||
100 | /* Save the current shadow stack base in ucontext. */ | |
101 | movq %fs:SSP_BASE_OFFSET, %rax | |
102 | movq %rax, (oSSP + 8)(%rdi) | |
103 | ||
104 | L(no_shstk): | |
105 | #endif | |
3cf01adb AJ |
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. */ | |
109 | ||
110 | leaq oFPREGSMEM(%rdi), %rcx | |
111 | movq %rcx, oFPREGS(%rdi) | |
112 | /* Save the floating-point environment. */ | |
113 | fnstenv (%rcx) | |
75ea32ab | 114 | fldenv (%rcx) |
3cf01adb AJ |
115 | stmxcsr oMXCSR(%rdi) |
116 | ||
117 | /* Save the current signal mask with | |
118 | rt_sigprocmask (SIG_BLOCK, NULL, set,_NSIG/8). */ | |
119 | leaq oSIGMASK(%rdi), %rdx | |
ee618985 UD |
120 | xorl %esi,%esi |
121 | #if SIG_BLOCK == 0 | |
122 | xorl %edi, %edi | |
123 | #else | |
124 | movl $SIG_BLOCK, %edi | |
125 | #endif | |
126 | movl $_NSIG8,%r10d | |
127 | movl $__NR_rt_sigprocmask, %eax | |
3cf01adb AJ |
128 | syscall |
129 | cmpq $-4095, %rax /* Check %rax for error. */ | |
130 | jae SYSCALL_ERROR_LABEL /* Jump to error handler if error. */ | |
131 | ||
132 | /* All done, return 0 for success. */ | |
ee618985 | 133 | xorl %eax, %eax |
3cf01adb AJ |
134 | ret |
135 | PSEUDO_END(__getcontext) | |
136 | ||
1ab18a5b | 137 | weak_alias (__getcontext, getcontext) |