1 /*
2 * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
3 * Licensed under the GPL
4 */
5
6 #include <signal.h>
7 #include "kern_constants.h"
8 #include "kern_util.h"
9 #include "longjmp.h"
10 #include "task.h"
11 #include "user.h"
12 #include "sysdep/ptrace.h"
13
14 /* Set during early boot */
15 static int host_has_cmov = 1;
16 static jmp_buf cmov_test_return;
17
cmov_sigill_test_handler(int sig)18 static void cmov_sigill_test_handler(int sig)
19 {
20 host_has_cmov = 0;
21 longjmp(cmov_test_return, 1);
22 }
23
arch_check_bugs(void)24 void arch_check_bugs(void)
25 {
26 struct sigaction old, new;
27
28 printk(UM_KERN_INFO "Checking for host processor cmov support...");
29 new.sa_handler = cmov_sigill_test_handler;
30
31 /* Make sure that SIGILL is enabled after the handler longjmps back */
32 new.sa_flags = SA_NODEFER;
33 sigemptyset(&new.sa_mask);
34 sigaction(SIGILL, &new, &old);
35
36 if (setjmp(cmov_test_return) == 0) {
37 unsigned long foo = 0;
38 __asm__ __volatile__("cmovz %0, %1" : "=r" (foo) : "0" (foo));
39 printk(UM_KERN_CONT "Yes\n");
40 } else
41 printk(UM_KERN_CONT "No\n");
42
43 sigaction(SIGILL, &old, &new);
44 }
45
arch_examine_signal(int sig,struct uml_pt_regs * regs)46 void arch_examine_signal(int sig, struct uml_pt_regs *regs)
47 {
48 unsigned char tmp[2];
49
50 /*
51 * This is testing for a cmov (0x0f 0x4x) instruction causing a
52 * SIGILL in init.
53 */
54 if ((sig != SIGILL) || (TASK_PID(get_current()) != 1))
55 return;
56
57 if (copy_from_user_proc(tmp, (void *) UPT_IP(regs), 2)) {
58 printk(UM_KERN_ERR "SIGILL in init, could not read "
59 "instructions!\n");
60 return;
61 }
62
63 if ((tmp[0] != 0x0f) || ((tmp[1] & 0xf0) != 0x40))
64 return;
65
66 if (host_has_cmov == 0)
67 printk(UM_KERN_ERR "SIGILL caused by cmov, which this "
68 "processor doesn't implement. Boot a filesystem "
69 "compiled for older processors");
70 else if (host_has_cmov == 1)
71 printk(UM_KERN_ERR "SIGILL caused by cmov, which this "
72 "processor claims to implement");
73 else
74 printk(UM_KERN_ERR "Bad value for host_has_cmov (%d)",
75 host_has_cmov);
76 }
77