/*
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *  Copyright (C) 2000, 2001, 2002 Andi Kleen, SuSE Labs
 */
#include <linux/kallsyms.h>
#include <linux/kprobes.h>
#include <linux/uaccess.h>
#include <linux/utsname.h>
#include <linux/hardirq.h>
#include <linux/kdebug.h>
#include <linux/module.h>
#include <linux/ptrace.h>
#include <linux/sched/debug.h>
#include <linux/sched/task_stack.h>
#include <linux/ftrace.h>
#include <linux/kexec.h>
#include <linux/bug.h>
#include <linux/nmi.h>
#include <linux/sysfs.h>

#include <asm/stacktrace.h>
#include <asm/unwind.h>

int panic_on_unrecovered_nmi;
int panic_on_io_nmi;
unsigned int code_bytes = 64;
static int die_counter;

bool in_task_stack(unsigned long *stack, struct task_struct *task,
                   struct stack_info *info)
{
        unsigned long *begin = task_stack_page(task);
        unsigned long *end   = task_stack_page(task) + THREAD_SIZE;

        if (stack < begin || stack >= end)
                return false;

        info->type      = STACK_TYPE_TASK;
        info->begin     = begin;
        info->end       = end;
        info->next_sp   = NULL;

        return true;
}

static void printk_stack_address(unsigned long address, int reliable,
                                 char *log_lvl)
{
        touch_nmi_watchdog();
        printk("%s %s%pB\n", log_lvl, reliable ? "" : "? ", (void *)address);
}

void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
                        unsigned long *stack, char *log_lvl)
{
        struct unwind_state state;
        struct stack_info stack_info = {0};
        unsigned long visit_mask = 0;
        int graph_idx = 0;

        printk("%sCall Trace:\n", log_lvl);

        unwind_start(&state, task, regs, stack);
        stack = stack ? : get_stack_pointer(task, regs);

        /*
         * Iterate through the stacks, starting with the current stack pointer.
         * Each stack has a pointer to the next one.
         *
         * x86-64 can have several stacks:
         * - task stack
         * - interrupt stack
         * - HW exception stacks (double fault, nmi, debug, mce)
         *
         * x86-32 can have up to three stacks:
         * - task stack
         * - softirq stack
         * - hardirq stack
         */
        for (regs = NULL; stack; stack = PTR_ALIGN(stack_info.next_sp, sizeof(long))) {
                const char *stack_name;

                /*
                 * If we overflowed the task stack into a guard page, jump back
                 * to the bottom of the usable stack.
                 */
                if (task_stack_page(task) - (void *)stack < PAGE_SIZE)
                        stack = task_stack_page(task);

                if (get_stack_info(stack, task, &stack_info, &visit_mask))
                        break;

                stack_name = stack_type_name(stack_info.type);
                if (stack_name)
                        printk("%s <%s>\n", log_lvl, stack_name);

                if (regs && on_stack(&stack_info, regs, sizeof(*regs)))
                        __show_regs(regs, 0);

                /*
                 * Scan the stack, printing any text addresses we find.  At the
                 * same time, follow proper stack frames with the unwinder.
                 *
                 * Addresses found during the scan which are not reported by
                 * the unwinder are considered to be additional clues which are
                 * sometimes useful for debugging and are prefixed with '?'.
                 * This also serves as a failsafe option in case the unwinder
                 * goes off in the weeds.
                 */
                for (; stack < stack_info.end; stack++) {
                        unsigned long real_addr;
                        int reliable = 0;
                        unsigned long addr = READ_ONCE_NOCHECK(*stack);
                        unsigned long *ret_addr_p =
                                unwind_get_return_address_ptr(&state);

                        if (!__kernel_text_address(addr))
                                continue;

                        /*
                         * Don't print regs->ip again if it was already printed
                         * by __show_regs() below.
                         */
                        if (regs && stack == &regs->ip)
                                goto next;

                        if (stack == ret_addr_p)
                                reliable = 1;

                        /*
                         * When function graph tracing is enabled for a
                         * function, its return address on the stack is
                         * replaced with the address of an ftrace handler
                         * (return_to_handler).  In that case, before printing
                         * the "real" address, we want to print the handler
                         * address as an "unreliable" hint that function graph
                         * tracing was involved.
                         */
                        real_addr = ftrace_graph_ret_addr(task, &graph_idx,
                                                          addr, stack);
                        if (real_addr != addr)
                                printk_stack_address(addr, 0, log_lvl);
                        printk_stack_address(real_addr, reliable, log_lvl);

                        if (!reliable)
                                continue;

next:
                        /*
                         * Get the next frame from the unwinder.  No need to
                         * check for an error: if anything goes wrong, the rest
                         * of the addresses will just be printed as unreliable.
                         */
                        unwind_next_frame(&state);

                        /* if the frame has entry regs, print them */
                        regs = unwind_get_entry_regs(&state);
                        if (regs && on_stack(&stack_info, regs, sizeof(*regs)))
                                __show_regs(regs, 0);
                }

                if (stack_name)
                        printk("%s </%s>\n", log_lvl, stack_name);
        }
}

void show_stack(struct task_struct *task, unsigned long *sp)
{
        task = task ? : current;

        /*
         * Stack frames below this one aren't interesting.  Don't show them
         * if we're printing for %current.
         */
        if (!sp && task == current)
                sp = get_stack_pointer(current, NULL);

        show_trace_log_lvl(task, NULL, sp, KERN_DEFAULT);
}

void show_stack_regs(struct pt_regs *regs)
{
        show_trace_log_lvl(current, regs, NULL, KERN_DEFAULT);
}

static arch_spinlock_t die_lock = __ARCH_SPIN_LOCK_UNLOCKED;
static int die_owner = -1;
static unsigned int die_nest_count;

unsigned long oops_begin(void)
{
        int cpu;
        unsigned long flags;

        oops_enter();

        /* racy, but better than risking deadlock. */
        raw_local_irq_save(flags);
        cpu = smp_processor_id();
        if (!arch_spin_trylock(&die_lock)) {
                if (cpu == die_owner)
                        /* nested oops. should stop eventually */;
                else
                        arch_spin_lock(&die_lock);
        }
        die_nest_count++;
        die_owner = cpu;
        console_verbose();
        bust_spinlocks(1);
        return flags;
}
EXPORT_SYMBOL_GPL(oops_begin);
NOKPROBE_SYMBOL(oops_begin);

void __noreturn rewind_stack_do_exit(int signr);

void oops_end(unsigned long flags, struct pt_regs *regs, int signr)
{
        if (regs && kexec_should_crash(current))
                crash_kexec(regs);

        bust_spinlocks(0);
        die_owner = -1;
        add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
        die_nest_count--;
        if (!die_nest_count)
                /* Nest count reaches zero, release the lock. */
                arch_spin_unlock(&die_lock);
        raw_local_irq_restore(flags);
        oops_exit();

        if (!signr)
                return;
        if (in_interrupt())
                panic("Fatal exception in interrupt");
        if (panic_on_oops)
                panic("Fatal exception");

        /*
         * We're not going to return, but we might be on an IST stack or
         * have very little stack space left.  Rewind the stack and kill
         * the task.
         */
        rewind_stack_do_exit(signr);
}
NOKPROBE_SYMBOL(oops_end);

int __die(const char *str, struct pt_regs *regs, long err)
{
#ifdef CONFIG_X86_32
        unsigned short ss;
        unsigned long sp;
#endif
        printk(KERN_DEFAULT
               "%s: %04lx [#%d]%s%s%s%s\n", str, err & 0xffff, ++die_counter,
               IS_ENABLED(CONFIG_PREEMPT) ? " PREEMPT"         : "",
               IS_ENABLED(CONFIG_SMP)     ? " SMP"             : "",
               debug_pagealloc_enabled()  ? " DEBUG_PAGEALLOC" : "",
               IS_ENABLED(CONFIG_KASAN)   ? " KASAN"           : "");

        if (notify_die(DIE_OOPS, str, regs, err,
                        current->thread.trap_nr, SIGSEGV) == NOTIFY_STOP)
                return 1;

        print_modules();
        show_regs(regs);
#ifdef CONFIG_X86_32
        if (user_mode(regs)) {
                sp = regs->sp;
                ss = regs->ss;
        } else {
                sp = kernel_stack_pointer(regs);
                savesegment(ss, ss);
        }
        printk(KERN_EMERG "EIP: %pS SS:ESP: %04x:%08lx\n",
               (void *)regs->ip, ss, sp);
#else
        /* Executive summary in case the oops scrolled away */
        printk(KERN_ALERT "RIP: %pS RSP: %016lx\n", (void *)regs->ip, regs->sp);
#endif
        return 0;
}
NOKPROBE_SYMBOL(__die);

/*
 * This is gone through when something in the kernel has done something bad
 * and is about to be terminated:
 */
void die(const char *str, struct pt_regs *regs, long err)
{
        unsigned long flags = oops_begin();
        int sig = SIGSEGV;

        if (__die(str, regs, err))
                sig = 0;
        oops_end(flags, regs, sig);
}

static int __init code_bytes_setup(char *s)
{
        ssize_t ret;
        unsigned long val;

        if (!s)
                return -EINVAL;

        ret = kstrtoul(s, 0, &val);
        if (ret)
                return ret;

        code_bytes = val;
        if (code_bytes > 8192)
                code_bytes = 8192;

        return 1;
}
__setup("code_bytes=", code_bytes_setup);