diff options
Diffstat (limited to 'sysdeps/unix/sysv/linux/x86_64/vfork.S')
| -rw-r--r-- | sysdeps/unix/sysv/linux/x86_64/vfork.S | 58 |
1 files changed, 39 insertions, 19 deletions
diff --git a/sysdeps/unix/sysv/linux/x86_64/vfork.S b/sysdeps/unix/sysv/linux/x86_64/vfork.S index 8332ade9fb..8f1ca9f836 100644 --- a/sysdeps/unix/sysv/linux/x86_64/vfork.S +++ b/sysdeps/unix/sysv/linux/x86_64/vfork.S @@ -1,4 +1,4 @@ -/* Copyright (C) 2001-2016 Free Software Foundation, Inc. +/* Copyright (C) 2001-2018 Free Software Foundation, Inc. This file is part of the GNU C Library. The GNU C Library is free software; you can redistribute it and/or @@ -20,6 +20,21 @@ #include <bits/errno.h> #include <tcb-offsets.h> +#if SHSTK_ENABLED +/* The shadow stack prevents us from pushing the saved return PC onto + the stack and returning normally. Instead we pop the shadow stack + and return directly. This is the safest way to return and ensures + any stack manipulations done by the vfork'd child doesn't cause the + parent to terminate when CET is enabled. */ +# undef SYSCALL_ERROR_HANDLER +# define SYSCALL_ERROR_HANDLER \ +0: \ + SYSCALL_SET_ERRNO; \ + or $-1, %RAX_LP; \ + jmp 1b; +# undef SYSCALL_ERROR_LABEL +# define SYSCALL_ERROR_LABEL 0f +#endif /* Clone the calling process, but without copying the whole address space. The calling process is suspended until the new process exits or is @@ -34,35 +49,40 @@ ENTRY (__vfork) cfi_adjust_cfa_offset(-8) cfi_register(%rip, %rdi) - /* Save the TCB-cached PID away in %esi, and then negate the TCB - field. But if it's zero, set it to 0x80000000 instead. See - raise.c for the logic that relies on this value. */ - movl %fs:PID, %esi - movl $0x80000000, %ecx - movl %esi, %edx - negl %edx - cmove %ecx, %edx - movl %edx, %fs:PID - /* Stuff the syscall number in RAX and enter into the kernel. */ movl $SYS_ify (vfork), %eax syscall +#if !SHSTK_ENABLED /* Push back the return PC. */ pushq %rdi cfi_adjust_cfa_offset(8) - - /* Restore the original value of the TCB cache of the PID, if we're - the parent. But in the child (syscall return value equals zero), - leave things as they are. */ - testq %rax, %rax - je 1f - movl %esi, %fs:PID -1: +#endif cmpl $-4095, %eax jae SYSCALL_ERROR_LABEL /* Branch forward if it failed. */ +#if SHSTK_ENABLED +1: + /* Check if shadow stack is in use. */ + xorl %esi, %esi + rdsspq %rsi + testq %rsi, %rsi + /* Normal return if shadow stack isn't in use. */ + je L(no_shstk) + + /* Pop return address from shadow stack and jump back to caller + directly. */ + movl $1, %esi + incsspq %rsi + jmp *%rdi + +L(no_shstk): + /* Push back the return PC. */ + pushq %rdi + cfi_adjust_cfa_offset(8) +#endif + /* Normal return. */ ret |