x86/vsyscall/64: Use X86_PF constants in the simulated #PF error code

Rather than hardcoding 6 with a comment, use the defined constants.

Signed-off-by: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Yu-cheng Yu <[email protected]>
Link: http://lkml.kernel.org/r/e023f20352b0d05a8b0205629897917262d2ad68.1542841400.git.luto@kernel.org
Signed-off-by: Ingo Molnar <[email protected]>

Author: amluto

arch/x86/entry/vsyscall/vsyscall_64.c

@@ -102,7 +102,7 @@ static bool write_ok_or_segv(unsigned long ptr, size_t size)
 	if (!access_ok(VERIFY_WRITE, (void __user *)ptr, size)) {
 		struct thread_struct *thread = &current->thread;
 
-		thread->error_code	= 6;  /* user fault, no page, write */
+		thread->error_code	= X86_PF_USER | X86_PF_WRITE;
 		thread->cr2		= ptr;
 		thread->trap_nr		= X86_TRAP_PF;