traps.c

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#include <linux/bug.h>
#include <linux/io.h>
#include <linux/types.h>
#include <linux/kdebug.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/uaccess.h>
#include <linux/hardirq.h>
#include <linux/kernel.h>
#include <linux/kexec.h>
#include <linux/module.h>
#include <asm/unwinder.h>
#include <asm/traps.h>

static DEFINE_SPINLOCK(die_lock);

void die(const char *str, struct pt_regs *regs, long err)
{
    static int die_counter;

    oops_enter();

    spin_lock_irq(&die_lock);
    console_verbose();
    bust_spinlocks(1);

    printk("%s: %04lx [#%d]\n", str, err & 0xffff, ++die_counter);
    print_modules();
    show_regs(regs);

    printk("Process: %s (pid: %d, stack limit = %p)\n", current->comm,
            task_pid_nr(current), task_stack_page(current) + 1);

    if (!user_mode(regs) || in_interrupt())
        dump_mem("Stack: ", regs->regs[15], THREAD_SIZE +
             (unsigned long)task_stack_page(current));

    notify_die(DIE_OOPS, str, regs, err, 255, SIGSEGV);

    bust_spinlocks(0);
    add_taint(TAINT_DIE);
    spin_unlock_irq(&die_lock);
    oops_exit();

    if (kexec_should_crash(current))
        crash_kexec(regs);

    if (in_interrupt())
        panic("Fatal exception in interrupt");

    if (panic_on_oops)
        panic("Fatal exception");

    do_exit(SIGSEGV);
}

void die_if_kernel(const char *str, struct pt_regs *regs, long err)
{
    if (!user_mode(regs))
        die(str, regs, err);
}

/*
 * try and fix up kernelspace address errors
 * - userspace errors just cause EFAULT to be returned, resulting in SEGV
 * - kernel/userspace interfaces cause a jump to an appropriate handler
 * - other kernel errors are bad
 */
void die_if_no_fixup(const char *str, struct pt_regs *regs, long err)
{
    if (!user_mode(regs)) {
        const struct exception_table_entry *fixup;
        fixup = search_exception_tables(regs->pc);
        if (fixup) {
            regs->pc = fixup->fixup;
            return;
        }

        die(str, regs, err);
    }
}

#ifdef CONFIG_GENERIC_BUG
static void handle_BUG(struct pt_regs *regs)
{
    const struct bug_entry *bug;
    unsigned long bugaddr = regs->pc;
    enum bug_trap_type tt;

    if (!is_valid_bugaddr(bugaddr))
        goto invalid;

    bug = find_bug(bugaddr);

    /* Switch unwinders when unwind_stack() is called */
    if (bug->flags & BUGFLAG_UNWINDER)
        unwinder_faulted = 1;

    tt = report_bug(bugaddr, regs);
    if (tt == BUG_TRAP_TYPE_WARN) {
        regs->pc += instruction_size(bugaddr);
        return;
    }

invalid:
    die("Kernel BUG", regs, TRAPA_BUG_OPCODE & 0xff);
}

int is_valid_bugaddr(unsigned long addr)
{
    insn_size_t opcode;

    if (addr < PAGE_OFFSET)
        return 0;
    if (probe_kernel_address((insn_size_t *)addr, opcode))
        return 0;
    if (opcode == TRAPA_BUG_OPCODE)
        return 1;

    return 0;
}
#endif

/*
 * Generic trap handler.
 */
BUILD_TRAP_HANDLER(debug)
{
    TRAP_HANDLER_DECL;

    /* Rewind */
    regs->pc -= instruction_size(__raw_readw(regs->pc - 4));

    if (notify_die(DIE_TRAP, "debug trap", regs, 0, vec & 0xff,
               SIGTRAP) == NOTIFY_STOP)
        return;

    force_sig(SIGTRAP, current);
}

/*
 * Special handler for BUG() traps.
 */
BUILD_TRAP_HANDLER(bug)
{
    TRAP_HANDLER_DECL;

    /* Rewind */
    regs->pc -= instruction_size(__raw_readw(regs->pc - 4));

    if (notify_die(DIE_TRAP, "bug trap", regs, 0, TRAPA_BUG_OPCODE & 0xff,
               SIGTRAP) == NOTIFY_STOP)
        return;

#ifdef CONFIG_GENERIC_BUG
    if (__kernel_text_address(instruction_pointer(regs))) {
        insn_size_t insn = *(insn_size_t *)instruction_pointer(regs);
        if (insn == TRAPA_BUG_OPCODE)
            handle_BUG(regs);
        return;
    }
#endif

    force_sig(SIGTRAP, current);
}

BUILD_TRAP_HANDLER(nmi)
{
    unsigned int cpu = smp_processor_id();
    TRAP_HANDLER_DECL;

    nmi_enter();
    nmi_count(cpu)++;

    switch (notify_die(DIE_NMI, "NMI", regs, 0, vec & 0xff, SIGINT)) {
    case NOTIFY_OK:
    case NOTIFY_STOP:
        break;
    case NOTIFY_BAD:
        die("Fatal Non-Maskable Interrupt", regs, SIGINT);
    default:
        printk(KERN_ALERT "Got NMI, but nobody cared. Ignoring...\n");
        break;
    }

    nmi_exit();
}