/*
 *  linux/arch/arm/kernel/traps.c
 *
 *  Copyright (C) 1995-2002 Russell King
 *  Fragments that appear the same as linux/arch/i386/kernel/traps.c (C) Linus Torvalds
 *
 * 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 in
 *  'linux/arch/arm/lib/traps.S'.  Mostly a debugging aid, but will probably
 *  kill the offending process.
 */
#include <linux/config.h>
#include <linux/module.h>
#include <linux/signal.h>
#include <linux/spinlock.h>
#include <linux/personality.h>
#include <linux/ptrace.h>
#include <linux/kallsyms.h>
#include <linux/init.h>

#include <asm/atomic.h>
#include <asm/cacheflush.h>
#include <asm/io.h>
#include <asm/system.h>
#include <asm/uaccess.h>
#include <asm/unistd.h>
#include <asm/traps.h>

#include "ptrace.h"

const char *processor_modes[]=
{ "USER_26", "FIQ_26" , "IRQ_26" , "SVC_26" , "UK4_26" , "UK5_26" , "UK6_26" , "UK7_26" ,
  "UK8_26" , "UK9_26" , "UK10_26", "UK11_26", "UK12_26", "UK13_26", "UK14_26", "UK15_26",
  "USER_32", "FIQ_32" , "IRQ_32" , "SVC_32" , "UK4_32" , "UK5_32" , "UK6_32" , "ABT_32" ,
  "UK8_32" , "UK9_32" , "UK10_32", "UND_32" , "UK12_32", "UK13_32", "UK14_32", "SYS_32"
};

static const char *handler[]= { "prefetch abort", "data abort", "address exception", "interrupt" };

#ifdef CONFIG_DEBUG_USER
unsigned int user_debug;

static int __init user_debug_setup(char *str)
{
        get_option(&str, &user_debug);
        return 1;
}
__setup("user_debug=", user_debug_setup);
#endif

void dump_backtrace_entry(unsigned long where, unsigned long from)
{
#ifdef CONFIG_KALLSYMS
        printk("[<%08lx>] ", where);
        print_symbol("(%s) ", where);
        printk("from [<%08lx>] ", from);
        print_symbol("(%s)\n", from);
#else
        printk("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 != 0))
                return -EFAULT;

        return 0;
}

/*
 * Dump out the contents of some memory nicely...
 */
static void dump_mem(const char *str, unsigned long bottom, unsigned long top)
{
        unsigned long p = bottom & ~31;
        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("%s(0x%08lx to 0x%08lx)\n", str, bottom, top);

        for (p = bottom & ~31; p < top;) {
                printk("%04lx: ", p & 0xffff);

                for (i = 0; i < 8; i++, p += 4) {
                        unsigned int val;

                        if (p < bottom || p >= top)
                                printk("         ");
                        else {
                                __get_user(val, (unsigned long *)p);
                                printk("%08x ", val);
                        }
                }
                printk ("\n");
        }

        set_fs(fs);
}

static void dump_instr(struct pt_regs *regs)
{
        unsigned long addr = instruction_pointer(regs);
        const int thumb = thumb_mode(regs);
        const int width = thumb ? 4 : 8;
        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("Code: ");
        for (i = -4; i < 1; i++) {
                unsigned int val, bad;

                if (thumb)
                        bad = __get_user(val, &((u16 *)addr)[i]);
                else
                        bad = __get_user(val, &((u32 *)addr)[i]);

                if (!bad)
                        printk(i == 0 ? "(%0*x) " : "%0*x ", width, val);
                else {
                        printk("bad PC value.");
                        break;
                }
        }
        printk("\n");

        set_fs(fs);
}

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

        printk("Backtrace: ");
        fp = regs->ARM_fp;
        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)(tsk->thread_info + 1))
                printk("frame pointer underflow");
        printk("\n");

        if (ok)
                c_backtrace(fp, processor_mode(regs));
}

void dump_stack(void)
{
#ifdef CONFIG_DEBUG_ERRORS
        __backtrace();
#endif
}

EXPORT_SYMBOL(dump_stack);

void show_stack(struct task_struct *tsk, unsigned long *sp)
{
        unsigned long fp;

        if (!tsk)
                tsk = current;

        if (tsk != current)
                fp = thread_saved_fp(tsk);
        else
                asm("mov%? %0, fp" : "=r" (fp));

        c_backtrace(fp, 0x10);
        barrier();
}

DEFINE_SPINLOCK(die_lock);

/*
 * This function is protected against re-entrancy.
 */
NORET_TYPE void die(const char *str, struct pt_regs *regs, int err)
{
        struct task_struct *tsk = current;
        static int die_counter;

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

        printk("Internal error: %s: %x [#%d]\n", str, err, ++die_counter);
        print_modules();
        __show_regs(regs);
        printk("Process %s (pid: %d, stack limit = 0x%p)\n",
                tsk->comm, tsk->pid, tsk->thread_info + 1);

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

        bust_spinlocks(0);
        spin_unlock_irq(&die_lock);
        do_exit(SIGSEGV);
}

void die_if_kernel(const char *str, struct pt_regs *regs, int err)
{
        if (user_mode(regs))
                return;

        die(str, regs, err);
}

static void notify_die(const char *str, struct pt_regs *regs, siginfo_t *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);
        }
}

static LIST_HEAD(undef_hook);
static DEFINE_SPINLOCK(undef_lock);

void register_undef_hook(struct undef_hook *hook)
{
        spin_lock_irq(&undef_lock);
        list_add(&hook->node, &undef_hook);
        spin_unlock_irq(&undef_lock);
}

void unregister_undef_hook(struct undef_hook *hook)
{
        spin_lock_irq(&undef_lock);
        list_del(&hook->node);
        spin_unlock_irq(&undef_lock);
}

asmlinkage void do_undefinstr(struct pt_regs *regs)
{
        unsigned int correction = thumb_mode(regs) ? 2 : 4;
        unsigned int instr;
        struct undef_hook *hook;
        siginfo_t info;
        void __user *pc;

        /*
         * According to the ARM ARM, PC is 2 or 4 bytes ahead,
         * depending whether we're in Thumb mode or not.
         * Correct this offset.
         */
        regs->ARM_pc -= correction;

        pc = (void __user *)instruction_pointer(regs);
        if (thumb_mode(regs)) {
                get_user(instr, (u16 __user *)pc);
        } else {
                get_user(instr, (u32 __user *)pc);
        }

        spin_lock_irq(&undef_lock);
        list_for_each_entry(hook, &undef_hook, node) {
                if ((instr & hook->instr_mask) == hook->instr_val &&
                    (regs->ARM_cpsr & hook->cpsr_mask) == hook->cpsr_val) {
                        if (hook->fn(regs, instr) == 0) {
                                spin_unlock_irq(&undef_lock);
                                return;
                        }
                }
        }
        spin_unlock_irq(&undef_lock);

#ifdef CONFIG_DEBUG_USER
        if (user_debug & UDBG_UNDEFINED) {
                printk(KERN_INFO "%s (%d): undefined instruction: pc=%p\n",
                        current->comm, current->pid, pc);
                dump_instr(regs);
        }
#endif

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

        notify_die("Oops - undefined instruction", regs, &info, 0, 6);
}

asmlinkage void do_unexp_fiq (struct pt_regs *regs)
{
#ifndef CONFIG_IGNORE_FIQ
        printk("Hmm.  Unexpected FIQ received, but trying to continue\n");
        printk("You may have a hardware problem...\n");
#endif
}

/*
 * 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, int reason, int proc_mode)
{
        console_verbose();

        printk(KERN_CRIT "Bad mode in %s handler detected: mode %s\n",
                handler[reason], processor_modes[proc_mode]);

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

static int bad_syscall(int n, struct pt_regs *regs)
{
        struct thread_info *thread = current_thread_info();
        siginfo_t info;

        if (current->personality != PER_LINUX && thread->exec_domain->handler) {
                thread->exec_domain->handler(n, regs);
                return regs->ARM_r0;
        }

#ifdef CONFIG_DEBUG_USER
        if (user_debug & UDBG_SYSCALL) {
                printk(KERN_ERR "[%d] %s: obsolete system call %08x.\n",
                        current->pid, current->comm, n);
                dump_instr(regs);
        }
#endif

        info.si_signo = SIGILL;
        info.si_errno = 0;
        info.si_code  = ILL_ILLTRP;
        info.si_addr  = (void __user *)instruction_pointer(regs) -
                         (thumb_mode(regs) ? 2 : 4);

        notify_die("Oops - bad syscall", regs, &info, n, 0);

        return regs->ARM_r0;
}

static inline void
do_cache_op(unsigned long start, unsigned long end, int flags)
{
        struct vm_area_struct *vma;

        if (end < start || flags)
                return;

        vma = find_vma(current->active_mm, start);
        if (vma && vma->vm_start < end) {
                if (start < vma->vm_start)
                        start = vma->vm_start;
                if (end > vma->vm_end)
                        end = vma->vm_end;

                flush_cache_user_range(vma, start, end);
        }
}

/*
 * Handle all unrecognised system calls.
 *  0x9f0000 - 0x9fffff are some more esoteric system calls
 */
#define NR(x) ((__ARM_NR_##x) - __ARM_NR_BASE)
asmlinkage int arm_syscall(int no, struct pt_regs *regs)
{
        struct thread_info *thread = current_thread_info();
        siginfo_t info;

        if ((no >> 16) != 0x9f)
                return bad_syscall(no, regs);

        switch (no & 0xffff) {
        case 0: /* branch through 0 */
                info.si_signo = SIGSEGV;
                info.si_errno = 0;
                info.si_code  = SEGV_MAPERR;
                info.si_addr  = NULL;

                notify_die("branch through zero", regs, &info, 0, 0);
                return 0;

        case NR(breakpoint): /* SWI BREAK_POINT */
                regs->ARM_pc -= thumb_mode(regs) ? 2 : 4;
                ptrace_break(current, regs);
                return regs->ARM_r0;

        /*
         * Flush a region from virtual address 'r0' to virtual address 'r1'
         * _exclusive_.  There is no alignment requirement on either address;
         * user space does not need to know the hardware cache layout.
         *
         * r2 contains flags.  It should ALWAYS be passed as ZERO until it
         * is defined to be something else.  For now we ignore it, but may
         * the fires of hell burn in your belly if you break this rule. ;)
         *
         * (at a later date, we may want to allow this call to not flush
         * various aspects of the cache.  Passing '0' will guarantee that
         * everything necessary gets flushed to maintain consistency in
         * the specified region).
         */
        case NR(cacheflush):
                do_cache_op(regs->ARM_r0, regs->ARM_r1, regs->ARM_r2);
                return 0;

        case NR(usr26):
                if (!(elf_hwcap & HWCAP_26BIT))
                        break;
                regs->ARM_cpsr &= ~MODE32_BIT;
                return regs->ARM_r0;

        case NR(usr32):
                if (!(elf_hwcap & HWCAP_26BIT))
                        break;
                regs->ARM_cpsr |= MODE32_BIT;
                return regs->ARM_r0;

        case NR(set_tls):
                thread->tp_value = regs->ARM_r0;
#if defined(CONFIG_HAS_TLS_REG)
                asm ("mcr p15, 0, %0, c13, c0, 3" : : "r" (regs->ARM_r0) );
#elif !defined(CONFIG_TLS_REG_EMUL)
                /*
                 * User space must never try to access this directly.
                 * Expect your app to break eventually if you do so.
                 * The user helper at 0xffff0fe0 must be used instead.
                 * (see entry-armv.S for details)
                 */
                *((unsigned int *)0xffff0ff0) = regs->ARM_r0;
#endif
                return 0;

#ifdef CONFIG_NEEDS_SYSCALL_FOR_CMPXCHG
        /*
         * Atomically store r1 in *r2 if *r2 is equal to r0 for user space.
         * Return zero in r0 if *MEM was changed or non-zero if no exchange
         * happened.  Also set the user C flag accordingly.
         * If access permissions have to be fixed up then non-zero is
         * returned and the operation has to be re-attempted.
         *
         * *NOTE*: This is a ghost syscall private to the kernel.  Only the
         * __kuser_cmpxchg code in entry-armv.S should be aware of its
         * existence.  Don't ever use this from user code.
         */
        case 0xfff0:
        {
                extern void do_DataAbort(unsigned long addr, unsigned int fsr,
                                         struct pt_regs *regs);
                unsigned long val;
                unsigned long addr = regs->ARM_r2;
                struct mm_struct *mm = current->mm;
                pgd_t *pgd; pmd_t *pmd; pte_t *pte;

                regs->ARM_cpsr &= ~PSR_C_BIT;
                spin_lock(&mm->page_table_lock);
                pgd = pgd_offset(mm, addr);
                if (!pgd_present(*pgd))
                        goto bad_access;
                pmd = pmd_offset(pgd, addr);
                if (!pmd_present(*pmd))
                        goto bad_access;
                pte = pte_offset_map(pmd, addr);
                if (!pte_present(*pte) || !pte_write(*pte))
                        goto bad_access;
                val = *(unsigned long *)addr;
                val -= regs->ARM_r0;
                if (val == 0) {
                        *(unsigned long *)addr = regs->ARM_r1;
                        regs->ARM_cpsr |= PSR_C_BIT;
                }
                spin_unlock(&mm->page_table_lock);
                return val;

                bad_access:
                spin_unlock(&mm->page_table_lock);
                /* simulate a read access fault */
                do_DataAbort(addr, 15 + (1 << 11), regs);
                return -1;
        }
#endif

        default:
                /* Calls 9f00xx..9f07ff are defined to return -ENOSYS
                   if not implemented, rather than raising SIGILL.  This
                   way the calling program can gracefully determine whether
                   a feature is supported.  */
                if (no <= 0x7ff)
                        return -ENOSYS;
                break;
        }
#ifdef CONFIG_DEBUG_USER
        /*
         * experience shows that these seem to indicate that
         * something catastrophic has happened
         */
        if (user_debug & UDBG_SYSCALL) {
                printk("[%d] %s: arm syscall %d\n",
                       current->pid, current->comm, no);
                dump_instr(regs);
                if (user_mode(regs)) {
                        __show_regs(regs);
                        c_backtrace(regs->ARM_fp, processor_mode(regs));
                }
        }
#endif
        info.si_signo = SIGILL;
        info.si_errno = 0;
        info.si_code  = ILL_ILLTRP;
        info.si_addr  = (void __user *)instruction_pointer(regs) -
                         (thumb_mode(regs) ? 2 : 4);

        notify_die("Oops - bad syscall(2)", regs, &info, no, 0);
        return 0;
}

#ifdef CONFIG_TLS_REG_EMUL

/*
 * We might be running on an ARMv6+ processor which should have the TLS
 * register but for some reason we can't use it, or maybe an SMP system
 * using a pre-ARMv6 processor (there are apparently a few prototypes like
 * that in existence) and therefore access to that register must be
 * emulated.
 */

static int get_tp_trap(struct pt_regs *regs, unsigned int instr)
{
        int reg = (instr >> 12) & 15;
        if (reg == 15)
                return 1;
        regs->uregs[reg] = current_thread_info()->tp_value;
        regs->ARM_pc += 4;
        return 0;
}

static struct undef_hook arm_mrc_hook = {
        .instr_mask     = 0x0fff0fff,
        .instr_val      = 0x0e1d0f70,
        .cpsr_mask      = PSR_T_BIT,
        .cpsr_val       = 0,
        .fn             = get_tp_trap,
};

static int __init arm_mrc_hook_init(void)
{
        register_undef_hook(&arm_mrc_hook);
        return 0;
}

late_initcall(arm_mrc_hook_init);

#endif

void __bad_xchg(volatile void *ptr, int size)
{
        printk("xchg: bad data size: pc 0x%p, ptr 0x%p, size %d\n",
                __builtin_return_address(0), ptr, size);
        BUG();
}
EXPORT_SYMBOL(__bad_xchg);

/*
 * A data abort trap was taken, but we did not handle the instruction.
 * Try to abort the user program, or panic if it was the kernel.
 */
asmlinkage void
baddataabort(int code, unsigned long instr, struct pt_regs *regs)
{
        unsigned long addr = instruction_pointer(regs);
        siginfo_t info;

#ifdef CONFIG_DEBUG_USER
        if (user_debug & UDBG_BADABORT) {
                printk(KERN_ERR "[%d] %s: bad data abort: code %d instr 0x%08lx\n",
                        current->pid, current->comm, code, instr);
                dump_instr(regs);
                show_pte(current->mm, addr);
        }
#endif

        info.si_signo = SIGILL;
        info.si_errno = 0;
        info.si_code  = ILL_ILLOPC;
        info.si_addr  = (void __user *)addr;

        notify_die("unknown data abort code", regs, &info, instr, 0);
}

volatile void __bug(const char *file, int line, void *data)
{
        printk(KERN_CRIT"kernel BUG at %s:%d!", file, line);
        if (data)
                printk(" - extra data = %p", data);
        printk("\n");
        *(int *)0 = 0;
}
EXPORT_SYMBOL(__bug);

void __readwrite_bug(const char *fn)
{
        printk("%s called, but not implemented\n", fn);
        BUG();
}
EXPORT_SYMBOL(__readwrite_bug);

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

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

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

asmlinkage void __div0(void)
{
        printk("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)
{
        extern char __stubs_start[], __stubs_end[];
        extern char __vectors_start[], __vectors_end[];
        extern char __kuser_helper_start[], __kuser_helper_end[];
        int kuser_sz = __kuser_helper_end - __kuser_helper_start;

        /*
         * Copy the vectors, stubs and kuser helpers (in entry-armv.S)
         * into the vector page, mapped at 0xffff0000, and ensure these
         * are visible to the instruction stream.
         */
        memcpy((void *)0xffff0000, __vectors_start, __vectors_end - __vectors_start);
        memcpy((void *)0xffff0200, __stubs_start, __stubs_end - __stubs_start);
        memcpy((void *)0xffff1000 - kuser_sz, __kuser_helper_start, kuser_sz);
        flush_icache_range(0xffff0000, 0xffff0000 + PAGE_SIZE);
        modify_domain(DOMAIN_USER, DOMAIN_CLIENT);
}