1/*
 2 * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 3 * Licensed under the GPL
 4 */
 5
 6#include <arch.h>
 7#include <signal.h>
 8#include <kern_util.h>
 9#include <longjmp.h>
10#include <sysdep/ptrace.h>
11#include <generated/asm-offsets.h>
12
13/* Set during early boot */
14static int host_has_cmov = 1;
15static jmp_buf cmov_test_return;
16
17static void cmov_sigill_test_handler(int sig)
18{
19	host_has_cmov = 0;
20	longjmp(cmov_test_return, 1);
21}
22
23void arch_check_bugs(void)
24{
25	struct sigaction old, new;
26
27	printk(UM_KERN_INFO "Checking for host processor cmov support...");
28	new.sa_handler = cmov_sigill_test_handler;
29
30	/* Make sure that SIGILL is enabled after the handler longjmps back */
31	new.sa_flags = SA_NODEFER;
32	sigemptyset(&new.sa_mask);
33	sigaction(SIGILL, &new, &old);
34
35	if (setjmp(cmov_test_return) == 0) {
36		unsigned long foo = 0;
37		__asm__ __volatile__("cmovz %0, %1" : "=r" (foo) : "0" (foo));
38		printk(UM_KERN_CONT "Yes\n");
39	} else
40		printk(UM_KERN_CONT "No\n");
41
42	sigaction(SIGILL, &old, &new);
43}
44
45void arch_examine_signal(int sig, struct uml_pt_regs *regs)
46{
47	unsigned char tmp[2];
48
49	/*
50	 * This is testing for a cmov (0x0f 0x4x) instruction causing a
51	 * SIGILL in init.
52	 */
53	if ((sig != SIGILL) || (get_current_pid() != 1))
54		return;
55
56	if (copy_from_user_proc(tmp, (void *) UPT_IP(regs), 2)) {
57		printk(UM_KERN_ERR "SIGILL in init, could not read "
58		       "instructions!\n");
59		return;
60	}
61
62	if ((tmp[0] != 0x0f) || ((tmp[1] & 0xf0) != 0x40))
63		return;
64
65	if (host_has_cmov == 0)
66		printk(UM_KERN_ERR "SIGILL caused by cmov, which this "
67		       "processor doesn't implement.  Boot a filesystem "
68		       "compiled for older processors");
69	else if (host_has_cmov == 1)
70		printk(UM_KERN_ERR "SIGILL caused by cmov, which this "
71		       "processor claims to implement");
72	else
73		printk(UM_KERN_ERR "Bad value for host_has_cmov (%d)",
74			host_has_cmov);
75}