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 <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 */
  14 static int host_has_cmov = 1;
  15 static jmp_buf cmov_test_return;
  16
  17 static void cmov_sigill_test_handler(int sig)
  18 {
  19         host_has_cmov = 0;
  20         longjmp(cmov_test_return, 1);
  21 }
  22
  23 void 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
  45 void 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 }