/*
 * linux/arch/unicore32/kernel/traps.c
 *
 * Code specific to PKUnity SoC and UniCore ISA
 *
 * Copyright (C) 2001-2010 GUAN Xue-tao
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 *  'traps.c' handles hardware exceptions after we have saved some state.
 *  Mostly a debugging aid, but will probably kill the offending process.
 */
#include <linux/module.h>
#include <linux/signal.h>
#include <linux/sched/signal.h>
#include <linux/sched/debug.h>
#include <linux/sched/task_stack.h>
#include <linux/spinlock.h>
#include <linux/personality.h>
#include <linux/kallsyms.h>
#include <linux/kdebug.h>
#include <linux/uaccess.h>
#include <linux/delay.h>
#include <linux/hardirq.h>
#include <linux/init.h>
#include <linux/atomic.h>
#include <linux/unistd.h>

#include <asm/cacheflush.h>
#include <asm/traps.h>

#include "setup.h"

static void dump_mem(const char *, const char *, unsigned long, unsigned long);

void dump_backtrace_entry(unsigned long where,
                unsigned long from, unsigned long frame)
{
#ifdef CONFIG_KALLSYMS
        printk(KERN_DEFAULT "[<%08lx>] (%pS) from [<%08lx>] (%pS)\n",
                        where, (void *)where, from, (void *)from);
#else
        printk(KERN_DEFAULT "Function entered at [<%08lx>] from [<%08lx>]\n",
                        where, from);
#endif
}

/*
 * Stack pointers should always be within the kernels view of
 * physical memory.  If it is not there, then we can't dump
 * out any information relating to the stack.
 */
static int verify_stack(unsigned long sp)
{
        if (sp < PAGE_OFFSET ||
            (sp > (unsigned long)high_memory && high_memory != NULL))
                return -EFAULT;

        return 0;
}

/*
 * Dump out the contents of some memory nicely...
 */
static void dump_mem(const char *lvl, const char *str, unsigned long bottom,
                     unsigned long top)
{
        unsigned long first;
        mm_segment_t fs;
        int i;

        /*
         * We need to switch to kernel mode so that we can use __get_user
         * to safely read from kernel space.  Note that we now dump the
         * code first, just in case the backtrace kills us.
         */
        fs = get_fs();
        set_fs(KERNEL_DS);

        printk(KERN_DEFAULT "%s%s(0x%08lx to 0x%08lx)\n",
                        lvl, str, bottom, top);

        for (first = bottom & ~31; first < top; first += 32) {
                unsigned long p;
                char str[sizeof(" 12345678") * 8 + 1];

                memset(str, ' ', sizeof(str));
                str[sizeof(str) - 1] = '\0';

                for (p = first, i = 0; i < 8 && p < top; i++, p += 4) {
                        if (p >= bottom && p < top) {
                                unsigned long val;
                                if (__get_user(val, (unsigned long *)p) == 0)
                                        sprintf(str + i * 9, " %08lx", val);
                                else
                                        sprintf(str + i * 9, " ????????");
                        }
                }
                printk(KERN_DEFAULT "%s%04lx:%s\n", lvl, first & 0xffff, str);
        }

        set_fs(fs);
}

static void dump_instr(const char *lvl, struct pt_regs *regs)
{
        unsigned long addr = instruction_pointer(regs);
        const int width = 8;
        mm_segment_t fs;
        char str[sizeof("00000000 ") * 5 + 2 + 1], *p = str;
        int i;

        /*
         * We need to switch to kernel mode so that we can use __get_user
         * to safely read from kernel space.  Note that we now dump the
         * code first, just in case the backtrace kills us.
         */
        fs = get_fs();
        set_fs(KERNEL_DS);

        for (i = -4; i < 1; i++) {
                unsigned int val, bad;

                bad = __get_user(val, &((u32 *)addr)[i]);

                if (!bad)
                        p += sprintf(p, i == 0 ? "(%0*x) " : "%0*x ",
                                        width, val);
                else {
                        p += sprintf(p, "bad PC value");
                        break;
                }
        }
        printk(KERN_DEFAULT "%sCode: %s\n", lvl, str);

        set_fs(fs);
}

static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
{
        unsigned int fp, mode;
        int ok = 1;

        printk(KERN_DEFAULT "Backtrace: ");

        if (!tsk)
                tsk = current;

        if (regs) {
                fp = regs->UCreg_fp;
                mode = processor_mode(regs);
        } else if (tsk != current) {
                fp = thread_saved_fp(tsk);
                mode = 0x10;
        } else {
                asm("mov %0, fp" : "=r" (fp) : : "cc");
                mode = 0x10;
        }

        if (!fp) {
                printk("no frame pointer");
                ok = 0;
        } else if (verify_stack(fp)) {
                printk("invalid frame pointer 0x%08x", fp);
                ok = 0;
        } else if (fp < (unsigned long)end_of_stack(tsk))
                printk("frame pointer underflow");
        printk("\n");

        if (ok)
                c_backtrace(fp, mode);
}

void show_stack(struct task_struct *tsk, unsigned long *sp)
{
        dump_backtrace(NULL, tsk);
        barrier();
}

static int __die(const char *str, int err, struct thread_info *thread,
                struct pt_regs *regs)
{
        struct task_struct *tsk = thread->task;
        static int die_counter;
        int ret;

        printk(KERN_EMERG "Internal error: %s: %x [#%d]\n",
               str, err, ++die_counter);

        /* trap and error numbers are mostly meaningless on UniCore */
        ret = notify_die(DIE_OOPS, str, regs, err, tsk->thread.trap_no, \
                        SIGSEGV);
        if (ret == NOTIFY_STOP)
                return ret;

        print_modules();
        __show_regs(regs);
        printk(KERN_EMERG "Process %.*s (pid: %d, stack limit = 0x%p)\n",
                TASK_COMM_LEN, tsk->comm, task_pid_nr(tsk), thread + 1);

        if (!user_mode(regs) || in_interrupt()) {
                dump_mem(KERN_EMERG, "Stack: ", regs->UCreg_sp,
                         THREAD_SIZE + (unsigned long)task_stack_page(tsk));
                dump_backtrace(regs, tsk);
                dump_instr(KERN_EMERG, regs);
        }

        return ret;
}

DEFINE_SPINLOCK(die_lock);

/*
 * This function is protected against re-entrancy.
 */
void die(const char *str, struct pt_regs *regs, int err)
{
        struct thread_info *thread = current_thread_info();
        int ret;

        oops_enter();

        spin_lock_irq(&die_lock);
        console_verbose();
        bust_spinlocks(1);
        ret = __die(str, err, thread, regs);

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

        if (in_interrupt())
                panic("Fatal exception in interrupt");
        if (panic_on_oops)
                panic("Fatal exception");
        if (ret != NOTIFY_STOP)
                do_exit(SIGSEGV);
}

void uc32_notify_die(const char *str, struct pt_regs *regs,
                struct siginfo *info, unsigned long err, unsigned long trap)
{
        if (user_mode(regs)) {
                current->thread.error_code = err;
                current->thread.trap_no = trap;

                force_sig_info(info->si_signo, info, current);
        } else
                die(str, regs, err);
}

/*
 * bad_mode handles the impossible case in the vectors.  If you see one of
 * these, then it's extremely serious, and could mean you have buggy hardware.
 * It never returns, and never tries to sync.  We hope that we can at least
 * dump out some state information...
 */
asmlinkage void bad_mode(struct pt_regs *regs, unsigned int reason)
{
        console_verbose();

        printk(KERN_CRIT "Bad mode detected with reason 0x%x\n", reason);

        die("Oops - bad mode", regs, 0);
        local_irq_disable();
        panic("bad mode");
}

void __pte_error(const char *file, int line, unsigned long val)
{
        printk(KERN_DEFAULT "%s:%d: bad pte %08lx.\n", file, line, val);
}

void __pmd_error(const char *file, int line, unsigned long val)
{
        printk(KERN_DEFAULT "%s:%d: bad pmd %08lx.\n", file, line, val);
}

void __pgd_error(const char *file, int line, unsigned long val)
{
        printk(KERN_DEFAULT "%s:%d: bad pgd %08lx.\n", file, line, val);
}

asmlinkage void __div0(void)
{
        printk(KERN_DEFAULT "Division by zero in kernel.\n");
        dump_stack();
}
EXPORT_SYMBOL(__div0);

void abort(void)
{
        BUG();

        /* if that doesn't kill us, halt */
        panic("Oops failed to kill thread");
}
EXPORT_SYMBOL(abort);

void __init trap_init(void)
{
        return;
}

void __init early_trap_init(void)
{
        unsigned long vectors = VECTORS_BASE;

        /*
         * Copy the vectors, stubs (in entry-unicore.S)
         * into the vector page, mapped at 0xffff0000, and ensure these
         * are visible to the instruction stream.
         */
        memcpy((void *)vectors,
                        __vectors_start,
                        __vectors_end - __vectors_start);
        memcpy((void *)vectors + 0x200,
                        __stubs_start,
                        __stubs_end - __stubs_start);

        early_signal_init();

        flush_icache_range(vectors, vectors + PAGE_SIZE);
}