arch/x86/um/bugs_32.c

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