bugs_32.c

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/*
 * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 * Licensed under the GPL
 */

#include <signal.h>
#include <kern_util.h>
#include <longjmp.h>
#include <sysdep/ptrace.h>
#include <generated/asm-offsets.h>

/* Set during early boot */
static int host_has_cmov = 1;
static jmp_buf cmov_test_return;

static void cmov_sigill_test_handler(int sig)
{
    host_has_cmov = 0;
    longjmp(cmov_test_return, 1);
}

void arch_check_bugs(void)
{
    struct sigaction old, new;

    printk(UM_KERN_INFO "Checking for host processor cmov support...");
    new.sa_handler = cmov_sigill_test_handler;

    /* Make sure that SIGILL is enabled after the handler longjmps back */
    new.sa_flags = SA_NODEFER;
    sigemptyset(&new.sa_mask);
    sigaction(SIGILL, &new, &old);

    if (setjmp(cmov_test_return) == 0) {
        unsigned long foo = 0;
        __asm__ __volatile__("cmovz %0, %1" : "=r" (foo) : "0" (foo));
        printk(UM_KERN_CONT "Yes\n");
    } else
        printk(UM_KERN_CONT "No\n");

    sigaction(SIGILL, &old, &new);
}

void arch_examine_signal(int sig, struct uml_pt_regs *regs)
{
    unsigned char tmp[2];

    /*
     * This is testing for a cmov (0x0f 0x4x) instruction causing a
     * SIGILL in init.
     */
    if ((sig != SIGILL) || (get_current_pid() != 1))
        return;

    if (copy_from_user_proc(tmp, (void *) UPT_IP(regs), 2)) {
        printk(UM_KERN_ERR "SIGILL in init, could not read "
               "instructions!\n");
        return;
    }

    if ((tmp[0] != 0x0f) || ((tmp[1] & 0xf0) != 0x40))
        return;

    if (host_has_cmov == 0)
        printk(UM_KERN_ERR "SIGILL caused by cmov, which this "
               "processor doesn't implement.  Boot a filesystem "
               "compiled for older processors");
    else if (host_has_cmov == 1)
        printk(UM_KERN_ERR "SIGILL caused by cmov, which this "
               "processor claims to implement");
    else
        printk(UM_KERN_ERR "Bad value for host_has_cmov (%d)",
            host_has_cmov);
}