diff options
Diffstat (limited to 'sysdeps/unix/sysv/linux/x86_64/vfork.S')
-rw-r--r-- | sysdeps/unix/sysv/linux/x86_64/vfork.S | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/sysdeps/unix/sysv/linux/x86_64/vfork.S b/sysdeps/unix/sysv/linux/x86_64/vfork.S index e4c8269e3d..8f1ca9f836 100644 --- a/sysdeps/unix/sysv/linux/x86_64/vfork.S +++ b/sysdeps/unix/sysv/linux/x86_64/vfork.S @@ -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 @@ -38,13 +53,36 @@ ENTRY (__vfork) movl $SYS_ify (vfork), %eax syscall +#if !SHSTK_ENABLED /* Push back the return PC. */ pushq %rdi cfi_adjust_cfa_offset(8) +#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 |