| 1 | /* Copyright (C) 2001-2022 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 RDI. We need a register that |
|---|
| 31 | is preserved by the syscall and that we're allowed to destroy. */ |
|---|
| 32 | popq %rdi |
|---|
| 33 | cfi_adjust_cfa_offset(-8) |
|---|
| 34 | cfi_register(%rip, %rdi) |
|---|
| 35 | |
|---|
| 36 | /* Stuff the syscall number in RAX and enter into the kernel. */ |
|---|
| 37 | movl $SYS_ify (vfork), %eax |
|---|
| 38 | syscall |
|---|
| 39 | |
|---|
| 40 | /* Push back the return PC. */ |
|---|
| 41 | pushq %rdi |
|---|
| 42 | cfi_adjust_cfa_offset(8) |
|---|
| 43 | |
|---|
| 44 | cmpl $-4095, %eax |
|---|
| 45 | jae SYSCALL_ERROR_LABEL /* Branch forward if it failed. */ |
|---|
| 46 | |
|---|
| 47 | #if SHSTK_ENABLED |
|---|
| 48 | /* Check if shadow stack is in use. */ |
|---|
| 49 | xorl %esi, %esi |
|---|
| 50 | rdsspq %rsi |
|---|
| 51 | testq %rsi, %rsi |
|---|
| 52 | /* Normal return if shadow stack isn't in use. */ |
|---|
| 53 | je L(no_shstk) |
|---|
| 54 | |
|---|
| 55 | testl %eax, %eax |
|---|
| 56 | /* In parent, normal return. */ |
|---|
| 57 | jnz L(no_shstk) |
|---|
| 58 | |
|---|
| 59 | /* NB: In child, jump back to caller via indirect branch without |
|---|
| 60 | popping shadow stack which is shared with parent. Keep shadow |
|---|
| 61 | stack mismatched so that child returns in the vfork-calling |
|---|
| 62 | function will trigger SIGSEGV. */ |
|---|
| 63 | popq %rdi |
|---|
| 64 | cfi_adjust_cfa_offset(-8) |
|---|
| 65 | jmp *%rdi |
|---|
| 66 | |
|---|
| 67 | L(no_shstk): |
|---|
| 68 | #endif |
|---|
| 69 | |
|---|
| 70 | /* Normal return. */ |
|---|
| 71 | ret |
|---|
| 72 | |
|---|
| 73 | PSEUDO_END (__vfork) |
|---|
| 74 | libc_hidden_def (__vfork) |
|---|
| 75 | |
|---|
| 76 | weak_alias (__vfork, vfork) |
|---|
| 77 | strong_alias (__vfork, __libc_vfork) |
|---|
| 78 | |
|---|
