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 #define TASK_PID(task) *((int *) &(((char *) (task))[HOST_TASK_PID]))
  17
  18 static void cmov_sigill_test_handler(int sig)
  19 {
  20         host_has_cmov = 0;
  21         longjmp(cmov_test_return, 1);
  22 }
  23
  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
  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 }