1 | /* Copyright (C) 1999-2022 Free Software Foundation, Inc. |
2 | This file is part of the GNU C Library. |
3 | |
4 | The GNU C Library is free software; you can redistribute it and/or |
5 | modify it under the terms of the GNU Lesser General Public |
6 | License as published by the Free Software Foundation; either |
7 | version 2.1 of the License, or (at your option) any later version. |
8 | |
9 | The GNU C Library is distributed in the hope that it will be useful, |
10 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
11 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
12 | Lesser General Public License for more details. |
13 | |
14 | You should have received a copy of the GNU Lesser General Public |
15 | License along with the GNU C Library; if not, see |
16 | <https://www.gnu.org/licenses/>. */ |
17 | |
18 | #include <sysdep.h> |
19 | #define _ERRNO_H 1 |
20 | #include <bits/errno.h> |
21 | #include <tcb-offsets.h> |
22 | |
23 | /* Clone the calling process, but without copying the whole address space. |
24 | The calling process is suspended until the new process exits or is |
25 | replaced by a call to `execve'. Return -1 for errors, 0 to the new process, |
26 | and the process ID of the new process to the old process. */ |
27 | |
28 | ENTRY (__vfork) |
29 | |
30 | /* Pop the return PC value into ECX. */ |
31 | popl %ecx |
32 | cfi_adjust_cfa_offset (-4) |
33 | cfi_register (%eip, %ecx) |
34 | |
35 | /* Stuff the syscall number in EAX and enter into the kernel. */ |
36 | movl $SYS_ify (vfork), %eax |
37 | int $0x80 |
38 | |
39 | /* Jump to the return PC. Don't jump directly since this |
40 | disturbs the branch target cache. Instead push the return |
41 | address back on the stack. */ |
42 | pushl %ecx |
43 | cfi_adjust_cfa_offset (4) |
44 | |
45 | cmpl $-4095, %eax |
46 | /* Branch forward if it failed. */ |
47 | jae SYSCALL_ERROR_LABEL |
48 | |
49 | #if SHSTK_ENABLED |
50 | /* Check if shadow stack is in use. */ |
51 | xorl %edx, %edx |
52 | rdsspd %edx |
53 | testl %edx, %edx |
54 | /* Normal return if shadow stack isn't in use. */ |
55 | je L(no_shstk) |
56 | |
57 | testl %eax, %eax |
58 | /* In parent, normal return. */ |
59 | jnz L(no_shstk) |
60 | |
61 | /* NB: In child, jump back to caller via indirect branch without |
62 | popping shadow stack which is shared with parent. Keep shadow |
63 | stack mismatched so that child returns in the vfork-calling |
64 | function will trigger SIGSEGV. */ |
65 | popl %ecx |
66 | cfi_adjust_cfa_offset (-4) |
67 | jmp *%ecx |
68 | |
69 | L(no_shstk): |
70 | #endif |
71 | |
72 | ret |
73 | |
74 | PSEUDO_END (__vfork) |
75 | libc_hidden_def (__vfork) |
76 | |
77 | weak_alias (__vfork, vfork) |
78 | strong_alias (__vfork, __libc_vfork) |
79 | |