// SPDX-License-Identifier: GPL-2.0
#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/sched/debug.h>
#include <linux/sched/task_stack.h>
#include <linux/uaccess.h>
#include <linux/hardirq.h>
#include <linux/kernel.h>
#include <linux/kexec.h>
#include <linux/sched/signal.h>

#include <linux/extable.h>
#include <linux/module.h>       /* print_modules */

#include <asm/ftrace.h>
#include <asm/unwinder.h>
#include <asm/traps.h>

static DEFINE_SPINLOCK(die_lock);

void __noreturn 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: ", KERN_DEFAULT, 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, LOCKDEP_NOW_UNRELIABLE);
        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");

        make_task_dead(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 (get_kernel_nofault(opcode, (insn_size_t *)addr))
                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);
}

/*
 * 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);
}

BUILD_TRAP_HANDLER(nmi)
{
        TRAP_HANDLER_DECL;

        arch_ftrace_nmi_enter();

        nmi_enter();
        this_cpu_inc(irq_stat.__nmi_count);

        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();

        arch_ftrace_nmi_exit();
}