mm/memory_hotplug.c: make scan_lru_pages() static

[linux-2.6/next.git] / arch / arm / kernel / ptrace.c

/*
 *  linux/arch/arm/kernel/ptrace.c
 *
 *  By Ross Biro 1/23/92
 * edited by Linus Torvalds
 * ARM modifications Copyright (C) 2000 Russell King
 *
 * 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.
 */
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/ptrace.h>
#include <linux/user.h>
#include <linux/security.h>
#include <linux/init.h>
#include <linux/signal.h>
#include <linux/uaccess.h>
#include <linux/perf_event.h>
#include <linux/hw_breakpoint.h>

#include <asm/pgtable.h>
#include <asm/system.h>
#include <asm/traps.h>

#include "ptrace.h"

#define REG_PC  15
#define REG_PSR 16
/*
 * does not yet catch signals sent when the child dies.
 * in exit.c or in signal.c.
 */

#if 0
/*
 * Breakpoint SWI instruction: SWI &9F0001
 */
#define BREAKINST_ARM   0xef9f0001
#define BREAKINST_THUMB 0xdf00          /* fill this in later */
#else
/*
 * New breakpoints - use an undefined instruction.  The ARM architecture
 * reference manual guarantees that the following instruction space
 * will produce an undefined instruction exception on all CPUs:
 *
 *  ARM:   xxxx 0111 1111 xxxx xxxx xxxx 1111 xxxx
 *  Thumb: 1101 1110 xxxx xxxx
 */
#define BREAKINST_ARM   0xe7f001f0
#define BREAKINST_THUMB 0xde01
#endif

struct pt_regs_offset {
        const char *name;
        int offset;
};

#define REG_OFFSET_NAME(r) \
        {.name = #r, .offset = offsetof(struct pt_regs, ARM_##r)}
#define REG_OFFSET_END {.name = NULL, .offset = 0}

static const struct pt_regs_offset regoffset_table[] = {
        REG_OFFSET_NAME(r0),
        REG_OFFSET_NAME(r1),
        REG_OFFSET_NAME(r2),
        REG_OFFSET_NAME(r3),
        REG_OFFSET_NAME(r4),
        REG_OFFSET_NAME(r5),
        REG_OFFSET_NAME(r6),
        REG_OFFSET_NAME(r7),
        REG_OFFSET_NAME(r8),
        REG_OFFSET_NAME(r9),
        REG_OFFSET_NAME(r10),
        REG_OFFSET_NAME(fp),
        REG_OFFSET_NAME(ip),
        REG_OFFSET_NAME(sp),
        REG_OFFSET_NAME(lr),
        REG_OFFSET_NAME(pc),
        REG_OFFSET_NAME(cpsr),
        REG_OFFSET_NAME(ORIG_r0),
        REG_OFFSET_END,
};

/**
 * regs_query_register_offset() - query register offset from its name
 * @name:       the name of a register
 *
 * regs_query_register_offset() returns the offset of a register in struct
 * pt_regs from its name. If the name is invalid, this returns -EINVAL;
 */
int regs_query_register_offset(const char *name)
{
        const struct pt_regs_offset *roff;
        for (roff = regoffset_table; roff->name != NULL; roff++)
                if (!strcmp(roff->name, name))
                        return roff->offset;
        return -EINVAL;
}

/**
 * regs_query_register_name() - query register name from its offset
 * @offset:     the offset of a register in struct pt_regs.
 *
 * regs_query_register_name() returns the name of a register from its
 * offset in struct pt_regs. If the @offset is invalid, this returns NULL;
 */
const char *regs_query_register_name(unsigned int offset)
{
        const struct pt_regs_offset *roff;
        for (roff = regoffset_table; roff->name != NULL; roff++)
                if (roff->offset == offset)
                        return roff->name;
        return NULL;
}

/**
 * regs_within_kernel_stack() - check the address in the stack
 * @regs:      pt_regs which contains kernel stack pointer.
 * @addr:      address which is checked.
 *
 * regs_within_kernel_stack() checks @addr is within the kernel stack page(s).
 * If @addr is within the kernel stack, it returns true. If not, returns false.
 */
bool regs_within_kernel_stack(struct pt_regs *regs, unsigned long addr)
{
        return ((addr & ~(THREAD_SIZE - 1))  ==
                (kernel_stack_pointer(regs) & ~(THREAD_SIZE - 1)));
}

/**
 * regs_get_kernel_stack_nth() - get Nth entry of the stack
 * @regs:       pt_regs which contains kernel stack pointer.
 * @n:          stack entry number.
 *
 * regs_get_kernel_stack_nth() returns @n th entry of the kernel stack which
 * is specified by @regs. If the @n th entry is NOT in the kernel stack,
 * this returns 0.
 */
unsigned long regs_get_kernel_stack_nth(struct pt_regs *regs, unsigned int n)
{
        unsigned long *addr = (unsigned long *)kernel_stack_pointer(regs);
        addr += n;
        if (regs_within_kernel_stack(regs, (unsigned long)addr))
                return *addr;
        else
                return 0;
}

/*
 * this routine will get a word off of the processes privileged stack.
 * the offset is how far from the base addr as stored in the THREAD.
 * this routine assumes that all the privileged stacks are in our
 * data space.
 */
static inline long get_user_reg(struct task_struct *task, int offset)
{
        return task_pt_regs(task)->uregs[offset];
}

/*
 * this routine will put a word on the processes privileged stack.
 * the offset is how far from the base addr as stored in the THREAD.
 * this routine assumes that all the privileged stacks are in our
 * data space.
 */
static inline int
put_user_reg(struct task_struct *task, int offset, long data)
{
        struct pt_regs newregs, *regs = task_pt_regs(task);
        int ret = -EINVAL;

        newregs = *regs;
        newregs.uregs[offset] = data;

        if (valid_user_regs(&newregs)) {
                regs->uregs[offset] = data;
                ret = 0;
        }

        return ret;
}

static inline int
read_u32(struct task_struct *task, unsigned long addr, u32 *res)
{
        int ret;

        ret = access_process_vm(task, addr, res, sizeof(*res), 0);

        return ret == sizeof(*res) ? 0 : -EIO;
}

static inline int
read_instr(struct task_struct *task, unsigned long addr, u32 *res)
{
        int ret;

        if (addr & 1) {
                u16 val;
                ret = access_process_vm(task, addr & ~1, &val, sizeof(val), 0);
                ret = ret == sizeof(val) ? 0 : -EIO;
                *res = val;
        } else {
                u32 val;
                ret = access_process_vm(task, addr & ~3, &val, sizeof(val), 0);
                ret = ret == sizeof(val) ? 0 : -EIO;
                *res = val;
        }
        return ret;
}

/*
 * Get value of register `rn' (in the instruction)
 */
static unsigned long
ptrace_getrn(struct task_struct *child, unsigned long insn)
{
        unsigned int reg = (insn >> 16) & 15;
        unsigned long val;

        val = get_user_reg(child, reg);
        if (reg == 15)
                val += 8;

        return val;
}

/*
 * Get value of operand 2 (in an ALU instruction)
 */
static unsigned long
ptrace_getaluop2(struct task_struct *child, unsigned long insn)
{
        unsigned long val;
        int shift;
        int type;

        if (insn & 1 << 25) {
                val = insn & 255;
                shift = (insn >> 8) & 15;
                type = 3;
        } else {
                val = get_user_reg (child, insn & 15);

                if (insn & (1 << 4))
                        shift = (int)get_user_reg (child, (insn >> 8) & 15);
                else
                        shift = (insn >> 7) & 31;

                type = (insn >> 5) & 3;
        }

        switch (type) {
        case 0: val <<= shift;  break;
        case 1: val >>= shift;  break;
        case 2:
                val = (((signed long)val) >> shift);
                break;
        case 3:
                val = (val >> shift) | (val << (32 - shift));
                break;
        }
        return val;
}

/*
 * Get value of operand 2 (in a LDR instruction)
 */
static unsigned long
ptrace_getldrop2(struct task_struct *child, unsigned long insn)
{
        unsigned long val;
        int shift;
        int type;

        val = get_user_reg(child, insn & 15);
        shift = (insn >> 7) & 31;
        type = (insn >> 5) & 3;

        switch (type) {
        case 0: val <<= shift;  break;
        case 1: val >>= shift;  break;
        case 2:
                val = (((signed long)val) >> shift);
                break;
        case 3:
                val = (val >> shift) | (val << (32 - shift));
                break;
        }
        return val;
}

#define OP_MASK 0x01e00000
#define OP_AND  0x00000000
#define OP_EOR  0x00200000
#define OP_SUB  0x00400000
#define OP_RSB  0x00600000
#define OP_ADD  0x00800000
#define OP_ADC  0x00a00000
#define OP_SBC  0x00c00000
#define OP_RSC  0x00e00000
#define OP_ORR  0x01800000
#define OP_MOV  0x01a00000
#define OP_BIC  0x01c00000
#define OP_MVN  0x01e00000

static unsigned long
get_branch_address(struct task_struct *child, unsigned long pc, unsigned long insn)
{
        u32 alt = 0;

        switch (insn & 0x0e000000) {
        case 0x00000000:
        case 0x02000000: {
                /*
                 * data processing
                 */
                long aluop1, aluop2, ccbit;

                if ((insn & 0x0fffffd0) == 0x012fff10) {
                        /*
                         * bx or blx
                         */
                        alt = get_user_reg(child, insn & 15);
                        break;
                }


                if ((insn & 0xf000) != 0xf000)
                        break;

                aluop1 = ptrace_getrn(child, insn);
                aluop2 = ptrace_getaluop2(child, insn);
                ccbit  = get_user_reg(child, REG_PSR) & PSR_C_BIT ? 1 : 0;

                switch (insn & OP_MASK) {
                case OP_AND: alt = aluop1 & aluop2;             break;
                case OP_EOR: alt = aluop1 ^ aluop2;             break;
                case OP_SUB: alt = aluop1 - aluop2;             break;
                case OP_RSB: alt = aluop2 - aluop1;             break;
                case OP_ADD: alt = aluop1 + aluop2;             break;
                case OP_ADC: alt = aluop1 + aluop2 + ccbit;     break;
                case OP_SBC: alt = aluop1 - aluop2 + ccbit;     break;
                case OP_RSC: alt = aluop2 - aluop1 + ccbit;     break;
                case OP_ORR: alt = aluop1 | aluop2;             break;
                case OP_MOV: alt = aluop2;                      break;
                case OP_BIC: alt = aluop1 & ~aluop2;            break;
                case OP_MVN: alt = ~aluop2;                     break;
                }
                break;
        }

        case 0x04000000:
        case 0x06000000:
                /*
                 * ldr
                 */
                if ((insn & 0x0010f000) == 0x0010f000) {
                        unsigned long base;

                        base = ptrace_getrn(child, insn);
                        if (insn & 1 << 24) {
                                long aluop2;

                                if (insn & 0x02000000)
                                        aluop2 = ptrace_getldrop2(child, insn);
                                else
                                        aluop2 = insn & 0xfff;

                                if (insn & 1 << 23)
                                        base += aluop2;
                                else
                                        base -= aluop2;
                        }
                        read_u32(child, base, &alt);
                }
                break;

        case 0x08000000:
                /*
                 * ldm
                 */
                if ((insn & 0x00108000) == 0x00108000) {
                        unsigned long base;
                        unsigned int nr_regs;

                        if (insn & (1 << 23)) {
                                nr_regs = hweight16(insn & 65535) << 2;

                                if (!(insn & (1 << 24)))
                                        nr_regs -= 4;
                        } else {
                                if (insn & (1 << 24))
                                        nr_regs = -4;
                                else
                                        nr_regs = 0;
                        }

                        base = ptrace_getrn(child, insn);

                        read_u32(child, base + nr_regs, &alt);
                        break;
                }
                break;

        case 0x0a000000: {
                /*
                 * bl or b
                 */
                signed long displ;
                /* It's a branch/branch link: instead of trying to
                 * figure out whether the branch will be taken or not,
                 * we'll put a breakpoint at both locations.  This is
                 * simpler, more reliable, and probably not a whole lot
                 * slower than the alternative approach of emulating the
                 * branch.
                 */
                displ = (insn & 0x00ffffff) << 8;
                displ = (displ >> 6) + 8;
                if (displ != 0 && displ != 4)
                        alt = pc + displ;
            }
            break;
        }

        return alt;
}

static int
swap_insn(struct task_struct *task, unsigned long addr,
          void *old_insn, void *new_insn, int size)
{
        int ret;

        ret = access_process_vm(task, addr, old_insn, size, 0);
        if (ret == size)
                ret = access_process_vm(task, addr, new_insn, size, 1);
        return ret;
}

static void
add_breakpoint(struct task_struct *task, struct debug_info *dbg, unsigned long addr)
{
        int nr = dbg->nsaved;

        if (nr < 2) {
                u32 new_insn = BREAKINST_ARM;
                int res;

                res = swap_insn(task, addr, &dbg->bp[nr].insn, &new_insn, 4);

                if (res == 4) {
                        dbg->bp[nr].address = addr;
                        dbg->nsaved += 1;
                }
        } else
                printk(KERN_ERR "ptrace: too many breakpoints\n");
}

/*
 * Clear one breakpoint in the user program.  We copy what the hardware
 * does and use bit 0 of the address to indicate whether this is a Thumb
 * breakpoint or an ARM breakpoint.
 */
static void clear_breakpoint(struct task_struct *task, struct debug_entry *bp)
{
        unsigned long addr = bp->address;
        union debug_insn old_insn;
        int ret;

        if (addr & 1) {
                ret = swap_insn(task, addr & ~1, &old_insn.thumb,
                                &bp->insn.thumb, 2);

                if (ret != 2 || old_insn.thumb != BREAKINST_THUMB)
                        printk(KERN_ERR "%s:%d: corrupted Thumb breakpoint at "
                                "0x%08lx (0x%04x)\n", task->comm,
                                task_pid_nr(task), addr, old_insn.thumb);
        } else {
                ret = swap_insn(task, addr & ~3, &old_insn.arm,
                                &bp->insn.arm, 4);

                if (ret != 4 || old_insn.arm != BREAKINST_ARM)
                        printk(KERN_ERR "%s:%d: corrupted ARM breakpoint at "
                                "0x%08lx (0x%08x)\n", task->comm,
                                task_pid_nr(task), addr, old_insn.arm);
        }
}

void ptrace_set_bpt(struct task_struct *child)
{
        struct pt_regs *regs;
        unsigned long pc;
        u32 insn;
        int res;

        regs = task_pt_regs(child);
        pc = instruction_pointer(regs);

        if (thumb_mode(regs)) {
                printk(KERN_WARNING "ptrace: can't handle thumb mode\n");
                return;
        }

        res = read_instr(child, pc, &insn);
        if (!res) {
                struct debug_info *dbg = &child->thread.debug;
                unsigned long alt;

                dbg->nsaved = 0;

                alt = get_branch_address(child, pc, insn);
                if (alt)
                        add_breakpoint(child, dbg, alt);

                /*
                 * Note that we ignore the result of setting the above
                 * breakpoint since it may fail.  When it does, this is
                 * not so much an error, but a forewarning that we may
                 * be receiving a prefetch abort shortly.
                 *
                 * If we don't set this breakpoint here, then we can
                 * lose control of the thread during single stepping.
                 */
                if (!alt || predicate(insn) != PREDICATE_ALWAYS)
                        add_breakpoint(child, dbg, pc + 4);
        }
}

/*
 * Ensure no single-step breakpoint is pending.  Returns non-zero
 * value if child was being single-stepped.
 */
void ptrace_cancel_bpt(struct task_struct *child)
{
        int i, nsaved = child->thread.debug.nsaved;

        child->thread.debug.nsaved = 0;

        if (nsaved > 2) {
                printk("ptrace_cancel_bpt: bogus nsaved: %d!\n", nsaved);
                nsaved = 2;
        }

        for (i = 0; i < nsaved; i++)
                clear_breakpoint(child, &child->thread.debug.bp[i]);
}

void user_disable_single_step(struct task_struct *task)
{
        task->ptrace &= ~PT_SINGLESTEP;
        ptrace_cancel_bpt(task);
}

void user_enable_single_step(struct task_struct *task)
{
        task->ptrace |= PT_SINGLESTEP;
}

/*
 * Called by kernel/ptrace.c when detaching..
 */
void ptrace_disable(struct task_struct *child)
{
        user_disable_single_step(child);
}

/*
 * Handle hitting a breakpoint.
 */
void ptrace_break(struct task_struct *tsk, struct pt_regs *regs)
{
        siginfo_t info;

        ptrace_cancel_bpt(tsk);

        info.si_signo = SIGTRAP;
        info.si_errno = 0;
        info.si_code  = TRAP_BRKPT;
        info.si_addr  = (void __user *)instruction_pointer(regs);

        force_sig_info(SIGTRAP, &info, tsk);
}

static int break_trap(struct pt_regs *regs, unsigned int instr)
{
        ptrace_break(current, regs);
        return 0;
}

static struct undef_hook arm_break_hook = {
        .instr_mask     = 0x0fffffff,
        .instr_val      = 0x07f001f0,
        .cpsr_mask      = PSR_T_BIT,
        .cpsr_val       = 0,
        .fn             = break_trap,
};

static struct undef_hook thumb_break_hook = {
        .instr_mask     = 0xffff,
        .instr_val      = 0xde01,
        .cpsr_mask      = PSR_T_BIT,
        .cpsr_val       = PSR_T_BIT,
        .fn             = break_trap,
};

static int thumb2_break_trap(struct pt_regs *regs, unsigned int instr)
{
        unsigned int instr2;
        void __user *pc;

        /* Check the second half of the instruction.  */
        pc = (void __user *)(instruction_pointer(regs) + 2);

        if (processor_mode(regs) == SVC_MODE) {
                instr2 = *(u16 *) pc;
        } else {
                get_user(instr2, (u16 __user *)pc);
        }

        if (instr2 == 0xa000) {
                ptrace_break(current, regs);
                return 0;
        } else {
                return 1;
        }
}

static struct undef_hook thumb2_break_hook = {
        .instr_mask     = 0xffff,
        .instr_val      = 0xf7f0,
        .cpsr_mask      = PSR_T_BIT,
        .cpsr_val       = PSR_T_BIT,
        .fn             = thumb2_break_trap,
};

static int __init ptrace_break_init(void)
{
        register_undef_hook(&arm_break_hook);
        register_undef_hook(&thumb_break_hook);
        register_undef_hook(&thumb2_break_hook);
        return 0;
}

core_initcall(ptrace_break_init);

/*
 * Read the word at offset "off" into the "struct user".  We
 * actually access the pt_regs stored on the kernel stack.
 */
static int ptrace_read_user(struct task_struct *tsk, unsigned long off,
                            unsigned long __user *ret)
{
        unsigned long tmp;

        if (off & 3 || off >= sizeof(struct user))
                return -EIO;

        tmp = 0;
        if (off == PT_TEXT_ADDR)
                tmp = tsk->mm->start_code;
        else if (off == PT_DATA_ADDR)
                tmp = tsk->mm->start_data;
        else if (off == PT_TEXT_END_ADDR)
                tmp = tsk->mm->end_code;
        else if (off < sizeof(struct pt_regs))
                tmp = get_user_reg(tsk, off >> 2);

        return put_user(tmp, ret);
}

/*
 * Write the word at offset "off" into "struct user".  We
 * actually access the pt_regs stored on the kernel stack.
 */
static int ptrace_write_user(struct task_struct *tsk, unsigned long off,
                             unsigned long val)
{
        if (off & 3 || off >= sizeof(struct user))
                return -EIO;

        if (off >= sizeof(struct pt_regs))
                return 0;

        return put_user_reg(tsk, off >> 2, val);
}

/*
 * Get all user integer registers.
 */
static int ptrace_getregs(struct task_struct *tsk, void __user *uregs)
{
        struct pt_regs *regs = task_pt_regs(tsk);

        return copy_to_user(uregs, regs, sizeof(struct pt_regs)) ? -EFAULT : 0;
}

/*
 * Set all user integer registers.
 */
static int ptrace_setregs(struct task_struct *tsk, void __user *uregs)
{
        struct pt_regs newregs;
        int ret;

        ret = -EFAULT;
        if (copy_from_user(&newregs, uregs, sizeof(struct pt_regs)) == 0) {
                struct pt_regs *regs = task_pt_regs(tsk);

                ret = -EINVAL;
                if (valid_user_regs(&newregs)) {
                        *regs = newregs;
                        ret = 0;
                }
        }

        return ret;
}

/*
 * Get the child FPU state.
 */
static int ptrace_getfpregs(struct task_struct *tsk, void __user *ufp)
{
        return copy_to_user(ufp, &task_thread_info(tsk)->fpstate,
                            sizeof(struct user_fp)) ? -EFAULT : 0;
}

/*
 * Set the child FPU state.
 */
static int ptrace_setfpregs(struct task_struct *tsk, void __user *ufp)
{
        struct thread_info *thread = task_thread_info(tsk);
        thread->used_cp[1] = thread->used_cp[2] = 1;
        return copy_from_user(&thread->fpstate, ufp,
                              sizeof(struct user_fp)) ? -EFAULT : 0;
}

#ifdef CONFIG_IWMMXT

/*
 * Get the child iWMMXt state.
 */
static int ptrace_getwmmxregs(struct task_struct *tsk, void __user *ufp)
{
        struct thread_info *thread = task_thread_info(tsk);

        if (!test_ti_thread_flag(thread, TIF_USING_IWMMXT))
                return -ENODATA;
        iwmmxt_task_disable(thread);  /* force it to ram */
        return copy_to_user(ufp, &thread->fpstate.iwmmxt, IWMMXT_SIZE)
                ? -EFAULT : 0;
}

/*
 * Set the child iWMMXt state.
 */
static int ptrace_setwmmxregs(struct task_struct *tsk, void __user *ufp)
{
        struct thread_info *thread = task_thread_info(tsk);

        if (!test_ti_thread_flag(thread, TIF_USING_IWMMXT))
                return -EACCES;
        iwmmxt_task_release(thread);  /* force a reload */
        return copy_from_user(&thread->fpstate.iwmmxt, ufp, IWMMXT_SIZE)
                ? -EFAULT : 0;
}

#endif

#ifdef CONFIG_CRUNCH
/*
 * Get the child Crunch state.
 */
static int ptrace_getcrunchregs(struct task_struct *tsk, void __user *ufp)
{
        struct thread_info *thread = task_thread_info(tsk);

        crunch_task_disable(thread);  /* force it to ram */
        return copy_to_user(ufp, &thread->crunchstate, CRUNCH_SIZE)
                ? -EFAULT : 0;
}

/*
 * Set the child Crunch state.
 */
static int ptrace_setcrunchregs(struct task_struct *tsk, void __user *ufp)
{
        struct thread_info *thread = task_thread_info(tsk);

        crunch_task_release(thread);  /* force a reload */
        return copy_from_user(&thread->crunchstate, ufp, CRUNCH_SIZE)
                ? -EFAULT : 0;
}
#endif

#ifdef CONFIG_VFP
/*
 * Get the child VFP state.
 */
static int ptrace_getvfpregs(struct task_struct *tsk, void __user *data)
{
        struct thread_info *thread = task_thread_info(tsk);
        union vfp_state *vfp = &thread->vfpstate;
        struct user_vfp __user *ufp = data;

        vfp_sync_hwstate(thread);

        /* copy the floating point registers */
        if (copy_to_user(&ufp->fpregs, &vfp->hard.fpregs,
                         sizeof(vfp->hard.fpregs)))
                return -EFAULT;

        /* copy the status and control register */
        if (put_user(vfp->hard.fpscr, &ufp->fpscr))
                return -EFAULT;

        return 0;
}

/*
 * Set the child VFP state.
 */
static int ptrace_setvfpregs(struct task_struct *tsk, void __user *data)
{
        struct thread_info *thread = task_thread_info(tsk);
        union vfp_state *vfp = &thread->vfpstate;
        struct user_vfp __user *ufp = data;

        vfp_sync_hwstate(thread);

        /* copy the floating point registers */
        if (copy_from_user(&vfp->hard.fpregs, &ufp->fpregs,
                           sizeof(vfp->hard.fpregs)))
                return -EFAULT;

        /* copy the status and control register */
        if (get_user(vfp->hard.fpscr, &ufp->fpscr))
                return -EFAULT;

        vfp_flush_hwstate(thread);

        return 0;
}
#endif

#ifdef CONFIG_HAVE_HW_BREAKPOINT
/*
 * Convert a virtual register number into an index for a thread_info
 * breakpoint array. Breakpoints are identified using positive numbers
 * whilst watchpoints are negative. The registers are laid out as pairs
 * of (address, control), each pair mapping to a unique hw_breakpoint struct.
 * Register 0 is reserved for describing resource information.
 */
static int ptrace_hbp_num_to_idx(long num)
{
        if (num < 0)
                num = (ARM_MAX_BRP << 1) - num;
        return (num - 1) >> 1;
}

/*
 * Returns the virtual register number for the address of the
 * breakpoint at index idx.
 */
static long ptrace_hbp_idx_to_num(int idx)
{
        long mid = ARM_MAX_BRP << 1;
        long num = (idx << 1) + 1;
        return num > mid ? mid - num : num;
}

/*
 * Handle hitting a HW-breakpoint.
 */
static void ptrace_hbptriggered(struct perf_event *bp, int unused,
                                     struct perf_sample_data *data,
                                     struct pt_regs *regs)
{
        struct arch_hw_breakpoint *bkpt = counter_arch_bp(bp);
        long num;
        int i;
        siginfo_t info;

        for (i = 0; i < ARM_MAX_HBP_SLOTS; ++i)
                if (current->thread.debug.hbp[i] == bp)
                        break;

        num = (i == ARM_MAX_HBP_SLOTS) ? 0 : ptrace_hbp_idx_to_num(i);

        info.si_signo   = SIGTRAP;
        info.si_errno   = (int)num;
        info.si_code    = TRAP_HWBKPT;
        info.si_addr    = (void __user *)(bkpt->trigger);

        force_sig_info(SIGTRAP, &info, current);
}

/*
 * Set ptrace breakpoint pointers to zero for this task.
 * This is required in order to prevent child processes from unregistering
 * breakpoints held by their parent.
 */
void clear_ptrace_hw_breakpoint(struct task_struct *tsk)
{
        memset(tsk->thread.debug.hbp, 0, sizeof(tsk->thread.debug.hbp));
}

/*
 * Unregister breakpoints from this task and reset the pointers in
 * the thread_struct.
 */
void flush_ptrace_hw_breakpoint(struct task_struct *tsk)
{
        int i;
        struct thread_struct *t = &tsk->thread;

        for (i = 0; i < ARM_MAX_HBP_SLOTS; i++) {
                if (t->debug.hbp[i]) {
                        unregister_hw_breakpoint(t->debug.hbp[i]);
                        t->debug.hbp[i] = NULL;
                }
        }
}

static u32 ptrace_get_hbp_resource_info(void)
{
        u8 num_brps, num_wrps, debug_arch, wp_len;
        u32 reg = 0;

        num_brps        = hw_breakpoint_slots(TYPE_INST);
        num_wrps        = hw_breakpoint_slots(TYPE_DATA);
        debug_arch      = arch_get_debug_arch();
        wp_len          = arch_get_max_wp_len();

        reg             |= debug_arch;
        reg             <<= 8;
        reg             |= wp_len;
        reg             <<= 8;
        reg             |= num_wrps;
        reg             <<= 8;
        reg             |= num_brps;

        return reg;
}

static struct perf_event *ptrace_hbp_create(struct task_struct *tsk, int type)
{
        struct perf_event_attr attr;

        ptrace_breakpoint_init(&attr);

        /* Initialise fields to sane defaults. */
        attr.bp_addr    = 0;
        attr.bp_len     = HW_BREAKPOINT_LEN_4;
        attr.bp_type    = type;
        attr.disabled   = 1;

        return register_user_hw_breakpoint(&attr, ptrace_hbptriggered, tsk);
}

static int ptrace_gethbpregs(struct task_struct *tsk, long num,
                             unsigned long  __user *data)
{
        u32 reg;
        int idx, ret = 0;
        struct perf_event *bp;
        struct arch_hw_breakpoint_ctrl arch_ctrl;

        if (num == 0) {
                reg = ptrace_get_hbp_resource_info();
        } else {
                idx = ptrace_hbp_num_to_idx(num);
                if (idx < 0 || idx >= ARM_MAX_HBP_SLOTS) {
                        ret = -EINVAL;
                        goto out;
                }

                bp = tsk->thread.debug.hbp[idx];
                if (!bp) {
                        reg = 0;
                        goto put;
                }

                arch_ctrl = counter_arch_bp(bp)->ctrl;

                /*
                 * Fix up the len because we may have adjusted it
                 * to compensate for an unaligned address.
                 */
                while (!(arch_ctrl.len & 0x1))
                        arch_ctrl.len >>= 1;

                if (idx & 0x1)
                        reg = encode_ctrl_reg(arch_ctrl);
                else
                        reg = bp->attr.bp_addr;
        }

put:
        if (put_user(reg, data))
                ret = -EFAULT;

out:
        return ret;
}

static int ptrace_sethbpregs(struct task_struct *tsk, long num,
                             unsigned long __user *data)
{
        int idx, gen_len, gen_type, implied_type, ret = 0;
        u32 user_val;
        struct perf_event *bp;
        struct arch_hw_breakpoint_ctrl ctrl;
        struct perf_event_attr attr;

        if (num == 0)
                goto out;
        else if (num < 0)
                implied_type = HW_BREAKPOINT_RW;
        else
                implied_type = HW_BREAKPOINT_X;

        idx = ptrace_hbp_num_to_idx(num);
        if (idx < 0 || idx >= ARM_MAX_HBP_SLOTS) {
                ret = -EINVAL;
                goto out;
        }

        if (get_user(user_val, data)) {
                ret = -EFAULT;
                goto out;
        }

        bp = tsk->thread.debug.hbp[idx];
        if (!bp) {
                bp = ptrace_hbp_create(tsk, implied_type);
                if (IS_ERR(bp)) {
                        ret = PTR_ERR(bp);
                        goto out;
                }
                tsk->thread.debug.hbp[idx] = bp;
        }

        attr = bp->attr;

        if (num & 0x1) {
                /* Address */
                attr.bp_addr    = user_val;
        } else {
                /* Control */
                decode_ctrl_reg(user_val, &ctrl);
                ret = arch_bp_generic_fields(ctrl, &gen_len, &gen_type);
                if (ret)
                        goto out;

                if ((gen_type & implied_type) != gen_type) {
                                ret = -EINVAL;
                                goto out;
                }

                attr.bp_len     = gen_len;
                attr.bp_type    = gen_type;
                attr.disabled   = !ctrl.enabled;
        }

        ret = modify_user_hw_breakpoint(bp, &attr);
out:
        return ret;
}
#endif

long arch_ptrace(struct task_struct *child, long request, long addr, long data)
{
        int ret;

        switch (request) {
                case PTRACE_PEEKUSR:
                        ret = ptrace_read_user(child, addr, (unsigned long __user *)data);
                        break;

                case PTRACE_POKEUSR:
                        ret = ptrace_write_user(child, addr, data);
                        break;

                case PTRACE_GETREGS:
                        ret = ptrace_getregs(child, (void __user *)data);
                        break;

                case PTRACE_SETREGS:
                        ret = ptrace_setregs(child, (void __user *)data);
                        break;

                case PTRACE_GETFPREGS:
                        ret = ptrace_getfpregs(child, (void __user *)data);
                        break;
                
                case PTRACE_SETFPREGS:
                        ret = ptrace_setfpregs(child, (void __user *)data);
                        break;

#ifdef CONFIG_IWMMXT
                case PTRACE_GETWMMXREGS:
                        ret = ptrace_getwmmxregs(child, (void __user *)data);
                        break;

                case PTRACE_SETWMMXREGS:
                        ret = ptrace_setwmmxregs(child, (void __user *)data);
                        break;
#endif

                case PTRACE_GET_THREAD_AREA:
                        ret = put_user(task_thread_info(child)->tp_value,
                                       (unsigned long __user *) data);
                        break;

                case PTRACE_SET_SYSCALL:
                        task_thread_info(child)->syscall = data;
                        ret = 0;
                        break;

#ifdef CONFIG_CRUNCH
                case PTRACE_GETCRUNCHREGS:
                        ret = ptrace_getcrunchregs(child, (void __user *)data);
                        break;

                case PTRACE_SETCRUNCHREGS:
                        ret = ptrace_setcrunchregs(child, (void __user *)data);
                        break;
#endif

#ifdef CONFIG_VFP
                case PTRACE_GETVFPREGS:
                        ret = ptrace_getvfpregs(child, (void __user *)data);
                        break;

                case PTRACE_SETVFPREGS:
                        ret = ptrace_setvfpregs(child, (void __user *)data);
                        break;
#endif

#ifdef CONFIG_HAVE_HW_BREAKPOINT
                case PTRACE_GETHBPREGS:
                        ret = ptrace_gethbpregs(child, addr,
                                                (unsigned long __user *)data);
                        break;
                case PTRACE_SETHBPREGS:
                        ret = ptrace_sethbpregs(child, addr,
                                                (unsigned long __user *)data);
                        break;
#endif

                default:
                        ret = ptrace_request(child, request, addr, data);
                        break;
        }

        return ret;
}

asmlinkage int syscall_trace(int why, struct pt_regs *regs, int scno)
{
        unsigned long ip;

        if (!test_thread_flag(TIF_SYSCALL_TRACE))
                return scno;
        if (!(current->ptrace & PT_PTRACED))
                return scno;

        /*
         * Save IP.  IP is used to denote syscall entry/exit:
         *  IP = 0 -> entry, = 1 -> exit
         */
        ip = regs->ARM_ip;
        regs->ARM_ip = why;

        current_thread_info()->syscall = scno;

        /* the 0x80 provides a way for the tracing parent to distinguish
           between a syscall stop and SIGTRAP delivery */
        ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD)
                                 ? 0x80 : 0));
        /*
         * this isn't the same as continuing with a signal, but it will do
         * for normal use.  strace only continues with a signal if the
         * stopping signal is not SIGTRAP.  -brl
         */
        if (current->exit_code) {
                send_sig(current->exit_code, current, 1);
                current->exit_code = 0;
        }
        regs->ARM_ip = ip;

        return current_thread_info()->syscall;
}