/*
 * Based on arch/arm/kernel/traps.c
 *
 * Copyright (C) 1995-2009 Russell King
 * Copyright (C) 2012 ARM Ltd.
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <linux/bug.h>
#include <linux/signal.h>
#include <linux/personality.h>
#include <linux/kallsyms.h>
#include <linux/spinlock.h>
#include <linux/uaccess.h>
#include <linux/hardirq.h>
#include <linux/kdebug.h>
#include <linux/module.h>
#include <linux/kexec.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/syscalls.h>

#include <asm/atomic.h>
#include <asm/bug.h>
#include <asm/debug-monitors.h>
#include <asm/esr.h>
#include <asm/insn.h>
#include <asm/traps.h>
#include <asm/stacktrace.h>
#include <asm/exception.h>
#include <asm/system_misc.h>

static const char *handler[]= {
        "Synchronous Abort",
        "IRQ",
        "FIQ",
        "Error"
};

int show_unhandled_signals = 1;

/*
 * Dump out the contents of some memory nicely...
 */
static void dump_mem(const char *lvl, const char *str, unsigned long bottom,
                     unsigned long top, bool compat)
{
        unsigned long first;
        mm_segment_t fs;
        int i;
        unsigned int width = compat ? 4 : 8;

        /*
         * 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("%s%s(0x%016lx to 0x%016lx)\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 < (32 / width)
                                        && p < top; i++, p += width) {
                        if (p >= bottom && p < top) {
                                unsigned long val;

                                if (width == 8) {
                                        if (__get_user(val, (unsigned long *)p) == 0)
                                                sprintf(str + i * 17, " %016lx", val);
                                        else
                                                sprintf(str + i * 17, " ????????????????");
                                } else {
                                        if (__get_user(val, (unsigned int *)p) == 0)
                                                sprintf(str + i * 9, " %08lx", val);
                                        else
                                                sprintf(str + i * 9, " ????????");
                                }
                        }
                }
                printk("%s%04lx:%s\n", lvl, first & 0xffff, str);
        }

        set_fs(fs);
}

static void dump_backtrace_entry(unsigned long where)
{
        /*
         * Note that 'where' can have a physical address, but it's not handled.
         */
        print_ip_sym(where);
}

static void dump_instr(const char *lvl, struct pt_regs *regs)
{
        unsigned long addr = instruction_pointer(regs);
        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 ? "(%08x) " : "%08x ", val);
                else {
                        p += sprintf(p, "bad PC value");
                        break;
                }
        }
        printk("%sCode: %s\n", lvl, str);

        set_fs(fs);
}

static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
{
        struct stackframe frame;
        unsigned long irq_stack_ptr;
        int skip;

        /*
         * Switching between stacks is valid when tracing current and in
         * non-preemptible context.
         */
        if (tsk == current && !preemptible())
                irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
        else
                irq_stack_ptr = 0;

        pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);

        if (!tsk)
                tsk = current;

        if (tsk == current) {
                frame.fp = (unsigned long)__builtin_frame_address(0);
                frame.sp = current_stack_pointer;
                frame.pc = (unsigned long)dump_backtrace;
        } else {
                /*
                 * task blocked in __switch_to
                 */
                frame.fp = thread_saved_fp(tsk);
                frame.sp = thread_saved_sp(tsk);
                frame.pc = thread_saved_pc(tsk);
        }
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
        frame.graph = tsk->curr_ret_stack;
#endif

        skip = !!regs;
        printk("Call trace:\n");
        while (1) {
                unsigned long where = frame.pc;
                unsigned long stack;
                int ret;

                /* skip until specified stack frame */
                if (!skip) {
                        dump_backtrace_entry(where);
                } else if (frame.fp == regs->regs[29]) {
                        skip = 0;
                        /*
                         * Mostly, this is the case where this function is
                         * called in panic/abort. As exception handler's
                         * stack frame does not contain the corresponding pc
                         * at which an exception has taken place, use regs->pc
                         * instead.
                         */
                        dump_backtrace_entry(regs->pc);
                }
                ret = unwind_frame(tsk, &frame);
                if (ret < 0)
                        break;
                stack = frame.sp;
                if (in_exception_text(where)) {
                        /*
                         * If we switched to the irq_stack before calling this
                         * exception handler, then the pt_regs will be on the
                         * task stack. The easiest way to tell is if the large
                         * pt_regs would overlap with the end of the irq_stack.
                         */
                        if (stack < irq_stack_ptr &&
                            (stack + sizeof(struct pt_regs)) > irq_stack_ptr)
                                stack = IRQ_STACK_TO_TASK_STACK(irq_stack_ptr);

                        dump_mem("", "Exception stack", stack,
                                 stack + sizeof(struct pt_regs), false);
                }
        }
}

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

#ifdef CONFIG_PREEMPT
#define S_PREEMPT " PREEMPT"
#else
#define S_PREEMPT ""
#endif
#define S_SMP " SMP"

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;

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

        /* trap and error numbers are mostly meaningless on ARM */
        ret = notify_die(DIE_OOPS, str, regs, err, 0, SIGSEGV);
        if (ret == NOTIFY_STOP)
                return ret;

        print_modules();
        __show_regs(regs);
        pr_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->sp,
                         THREAD_SIZE + (unsigned long)task_stack_page(tsk),
                         compat_user_mode(regs));
                dump_backtrace(regs, tsk);
                dump_instr(KERN_EMERG, regs);
        }

        return ret;
}

static DEFINE_RAW_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();

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

        if (regs && kexec_should_crash(thread->task))
                crash_kexec(regs);

        bust_spinlocks(0);
        add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
        raw_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 arm64_notify_die(const char *str, struct pt_regs *regs,
                      struct siginfo *info, int err)
{
        if (user_mode(regs)) {
                current->thread.fault_address = 0;
                current->thread.fault_code = err;
                force_sig_info(info->si_signo, info, current);
        } else {
                die(str, regs, err);
        }
}

static LIST_HEAD(undef_hook);
static DEFINE_RAW_SPINLOCK(undef_lock);

void register_undef_hook(struct undef_hook *hook)
{
        unsigned long flags;

        raw_spin_lock_irqsave(&undef_lock, flags);
        list_add(&hook->node, &undef_hook);
        raw_spin_unlock_irqrestore(&undef_lock, flags);
}

void unregister_undef_hook(struct undef_hook *hook)
{
        unsigned long flags;

        raw_spin_lock_irqsave(&undef_lock, flags);
        list_del(&hook->node);
        raw_spin_unlock_irqrestore(&undef_lock, flags);
}

static int call_undef_hook(struct pt_regs *regs)
{
        struct undef_hook *hook;
        unsigned long flags;
        u32 instr;
        int (*fn)(struct pt_regs *regs, u32 instr) = NULL;
        void __user *pc = (void __user *)instruction_pointer(regs);

        if (!user_mode(regs))
                return 1;

        if (compat_thumb_mode(regs)) {
                /* 16-bit Thumb instruction */
                if (get_user(instr, (u16 __user *)pc))
                        goto exit;
                instr = le16_to_cpu(instr);
                if (aarch32_insn_is_wide(instr)) {
                        u32 instr2;

                        if (get_user(instr2, (u16 __user *)(pc + 2)))
                                goto exit;
                        instr2 = le16_to_cpu(instr2);
                        instr = (instr << 16) | instr2;
                }
        } else {
                /* 32-bit ARM instruction */
                if (get_user(instr, (u32 __user *)pc))
                        goto exit;
                instr = le32_to_cpu(instr);
        }

        raw_spin_lock_irqsave(&undef_lock, flags);
        list_for_each_entry(hook, &undef_hook, node)
                if ((instr & hook->instr_mask) == hook->instr_val &&
                        (regs->pstate & hook->pstate_mask) == hook->pstate_val)
                        fn = hook->fn;

        raw_spin_unlock_irqrestore(&undef_lock, flags);
exit:
        return fn ? fn(regs, instr) : 1;
}

asmlinkage void __exception do_undefinstr(struct pt_regs *regs)
{
        siginfo_t info;
        void __user *pc = (void __user *)instruction_pointer(regs);

        /* check for AArch32 breakpoint instructions */
        if (!aarch32_break_handler(regs))
                return;

        if (call_undef_hook(regs) == 0)
                return;

        if (unhandled_signal(current, SIGILL) && show_unhandled_signals_ratelimited()) {
                pr_info("%s[%d]: undefined instruction: pc=%p\n",
                        current->comm, task_pid_nr(current), pc);
                dump_instr(KERN_INFO, regs);
        }

        info.si_signo = SIGILL;
        info.si_errno = 0;
        info.si_code  = ILL_ILLOPC;
        info.si_addr  = pc;

        arm64_notify_die("Oops - undefined instruction", regs, &info, 0);
}

long compat_arm_syscall(struct pt_regs *regs);

asmlinkage long do_ni_syscall(struct pt_regs *regs)
{
#ifdef CONFIG_COMPAT
        long ret;
        if (is_compat_task()) {
                ret = compat_arm_syscall(regs);
                if (ret != -ENOSYS)
                        return ret;
        }
#endif

        if (show_unhandled_signals_ratelimited()) {
                pr_info("%s[%d]: syscall %d\n", current->comm,
                        task_pid_nr(current), (int)regs->syscallno);
                dump_instr("", regs);
                if (user_mode(regs))
                        __show_regs(regs);
        }

        return sys_ni_syscall();
}

static const char *esr_class_str[] = {
        [0 ... ESR_ELx_EC_MAX]          = "UNRECOGNIZED EC",
        [ESR_ELx_EC_UNKNOWN]            = "Unknown/Uncategorized",
        [ESR_ELx_EC_WFx]                = "WFI/WFE",
        [ESR_ELx_EC_CP15_32]            = "CP15 MCR/MRC",
        [ESR_ELx_EC_CP15_64]            = "CP15 MCRR/MRRC",
        [ESR_ELx_EC_CP14_MR]            = "CP14 MCR/MRC",
        [ESR_ELx_EC_CP14_LS]            = "CP14 LDC/STC",
        [ESR_ELx_EC_FP_ASIMD]           = "ASIMD",
        [ESR_ELx_EC_CP10_ID]            = "CP10 MRC/VMRS",
        [ESR_ELx_EC_CP14_64]            = "CP14 MCRR/MRRC",
        [ESR_ELx_EC_ILL]                = "PSTATE.IL",
        [ESR_ELx_EC_SVC32]              = "SVC (AArch32)",
        [ESR_ELx_EC_HVC32]              = "HVC (AArch32)",
        [ESR_ELx_EC_SMC32]              = "SMC (AArch32)",
        [ESR_ELx_EC_SVC64]              = "SVC (AArch64)",
        [ESR_ELx_EC_HVC64]              = "HVC (AArch64)",
        [ESR_ELx_EC_SMC64]              = "SMC (AArch64)",
        [ESR_ELx_EC_SYS64]              = "MSR/MRS (AArch64)",
        [ESR_ELx_EC_IMP_DEF]            = "EL3 IMP DEF",
        [ESR_ELx_EC_IABT_LOW]           = "IABT (lower EL)",
        [ESR_ELx_EC_IABT_CUR]           = "IABT (current EL)",
        [ESR_ELx_EC_PC_ALIGN]           = "PC Alignment",
        [ESR_ELx_EC_DABT_LOW]           = "DABT (lower EL)",
        [ESR_ELx_EC_DABT_CUR]           = "DABT (current EL)",
        [ESR_ELx_EC_SP_ALIGN]           = "SP Alignment",
        [ESR_ELx_EC_FP_EXC32]           = "FP (AArch32)",
        [ESR_ELx_EC_FP_EXC64]           = "FP (AArch64)",
        [ESR_ELx_EC_SERROR]             = "SError",
        [ESR_ELx_EC_BREAKPT_LOW]        = "Breakpoint (lower EL)",
        [ESR_ELx_EC_BREAKPT_CUR]        = "Breakpoint (current EL)",
        [ESR_ELx_EC_SOFTSTP_LOW]        = "Software Step (lower EL)",
        [ESR_ELx_EC_SOFTSTP_CUR]        = "Software Step (current EL)",
        [ESR_ELx_EC_WATCHPT_LOW]        = "Watchpoint (lower EL)",
        [ESR_ELx_EC_WATCHPT_CUR]        = "Watchpoint (current EL)",
        [ESR_ELx_EC_BKPT32]             = "BKPT (AArch32)",
        [ESR_ELx_EC_VECTOR32]           = "Vector catch (AArch32)",
        [ESR_ELx_EC_BRK64]              = "BRK (AArch64)",
};

const char *esr_get_class_string(u32 esr)
{
        return esr_class_str[esr >> ESR_ELx_EC_SHIFT];
}

/*
 * bad_mode handles the impossible case in the exception vector.
 */
asmlinkage void bad_mode(struct pt_regs *regs, int reason, unsigned int esr)
{
        siginfo_t info;
        void __user *pc = (void __user *)instruction_pointer(regs);
        console_verbose();

        pr_crit("Bad mode in %s handler detected, code 0x%08x -- %s\n",
                handler[reason], esr, esr_get_class_string(esr));
        __show_regs(regs);

        info.si_signo = SIGILL;
        info.si_errno = 0;
        info.si_code  = ILL_ILLOPC;
        info.si_addr  = pc;

        arm64_notify_die("Oops - bad mode", regs, &info, 0);
}

void __pte_error(const char *file, int line, unsigned long val)
{
        pr_err("%s:%d: bad pte %016lx.\n", file, line, val);
}

void __pmd_error(const char *file, int line, unsigned long val)
{
        pr_err("%s:%d: bad pmd %016lx.\n", file, line, val);
}

void __pud_error(const char *file, int line, unsigned long val)
{
        pr_err("%s:%d: bad pud %016lx.\n", file, line, val);
}

void __pgd_error(const char *file, int line, unsigned long val)
{
        pr_err("%s:%d: bad pgd %016lx.\n", file, line, val);
}

/* GENERIC_BUG traps */

int is_valid_bugaddr(unsigned long addr)
{
        /*
         * bug_handler() only called for BRK #BUG_BRK_IMM.
         * So the answer is trivial -- any spurious instances with no
         * bug table entry will be rejected by report_bug() and passed
         * back to the debug-monitors code and handled as a fatal
         * unexpected debug exception.
         */
        return 1;
}

static int bug_handler(struct pt_regs *regs, unsigned int esr)
{
        if (user_mode(regs))
                return DBG_HOOK_ERROR;

        switch (report_bug(regs->pc, regs)) {
        case BUG_TRAP_TYPE_BUG:
                die("Oops - BUG", regs, 0);
                break;

        case BUG_TRAP_TYPE_WARN:
                /* Ideally, report_bug() should backtrace for us... but no. */
                dump_backtrace(regs, NULL);
                break;

        default:
                /* unknown/unrecognised bug trap type */
                return DBG_HOOK_ERROR;
        }

        /* If thread survives, skip over the BUG instruction and continue: */
        regs->pc += AARCH64_INSN_SIZE;  /* skip BRK and resume */
        return DBG_HOOK_HANDLED;
}

static struct break_hook bug_break_hook = {
        .esr_val = 0xf2000000 | BUG_BRK_IMM,
        .esr_mask = 0xffffffff,
        .fn = bug_handler,
};

/*
 * Initial handler for AArch64 BRK exceptions
 * This handler only used until debug_traps_init().
 */
int __init early_brk64(unsigned long addr, unsigned int esr,
                struct pt_regs *regs)
{
        return bug_handler(regs, esr) != DBG_HOOK_HANDLED;
}

/* This registration must happen early, before debug_traps_init(). */
void __init trap_init(void)
{
        register_break_hook(&bug_break_hook);
}