x86/um/bugs_32.c

0001 /*
0002  * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
0003  * Licensed under the GPL
0004  */
0005
0006 #include <signal.h>
0007 #include <kern_util.h>
0008 #include <longjmp.h>
0009 #include <sysdep/ptrace.h>
0010 #include <generated/asm-offsets.h>
0011
0012 /* Set during early boot */
0013 static int host_has_cmov = 1;
0014 static jmp_buf cmov_test_return;
0015
0016 static void cmov_sigill_test_handler(int sig)
0017 {
0018     host_has_cmov = 0;
0019     longjmp(cmov_test_return, 1);
0020 }
0021
0022 void arch_check_bugs(void)
0023 {
0024     struct sigaction old, new;
0025
0026     printk(UM_KERN_INFO "Checking for host processor cmov support...");
0027     new.sa_handler = cmov_sigill_test_handler;
0028
0029     /* Make sure that SIGILL is enabled after the handler longjmps back */
0030     new.sa_flags = SA_NODEFER;
0031     sigemptyset(&new.sa_mask);
0032     sigaction(SIGILL, &new, &old);
0033
0034     if (setjmp(cmov_test_return) == 0) {
0035         unsigned long foo = 0;
0036         __asm__ __volatile__("cmovz %0, %1" : "=r" (foo) : "0" (foo));
0037         printk(UM_KERN_CONT "Yes\n");
0038     } else
0039         printk(UM_KERN_CONT "No\n");
0040
0041     sigaction(SIGILL, &old, &new);
0042 }
0043
0044 void arch_examine_signal(int sig, struct uml_pt_regs *regs)
0045 {
0046     unsigned char tmp[2];
0047
0048     /*
0049      * This is testing for a cmov (0x0f 0x4x) instruction causing a
0050      * SIGILL in init.
0051      */
0052     if ((sig != SIGILL) || (get_current_pid() != 1))
0053         return;
0054
0055     if (copy_from_user_proc(tmp, (void *) UPT_IP(regs), 2)) {
0056         printk(UM_KERN_ERR "SIGILL in init, could not read "
0057                "instructions!\n");
0058         return;
0059     }
0060
0061     if ((tmp[0] != 0x0f) || ((tmp[1] & 0xf0) != 0x40))
0062         return;
0063
0064     if (host_has_cmov == 0)
0065         printk(UM_KERN_ERR "SIGILL caused by cmov, which this "
0066                "processor doesn't implement.  Boot a filesystem "
0067                "compiled for older processors");
0068     else if (host_has_cmov == 1)
0069         printk(UM_KERN_ERR "SIGILL caused by cmov, which this "
0070                "processor claims to implement");
0071     else
0072         printk(UM_KERN_ERR "Bad value for host_has_cmov (%d)",
0073             host_has_cmov);
0074 }