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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

00057 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,
             unsigned long addr, unsigned long data)
{
      int ret;
      unsigned long __user *datap = (unsigned long __user *) data;

      switch (request) {
            case PTRACE_PEEKUSR:
                  ret = ptrace_read_user(child, addr, datap);
                  break;

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

            case PTRACE_GETREGS:
                  ret = ptrace_getregs(child, datap);
                  break;

            case PTRACE_SETREGS:
                  ret = ptrace_setregs(child, datap);
                  break;

            case PTRACE_GETFPREGS:
                  ret = ptrace_getfpregs(child, datap);
                  break;
            
            case PTRACE_SETFPREGS:
                  ret = ptrace_setfpregs(child, datap);
                  break;

#ifdef CONFIG_IWMMXT
            case PTRACE_GETWMMXREGS:
                  ret = ptrace_getwmmxregs(child, datap);
                  break;

            case PTRACE_SETWMMXREGS:
                  ret = ptrace_setwmmxregs(child, datap);
                  break;
#endif

            case PTRACE_GET_THREAD_AREA:
                  ret = put_user(task_thread_info(child)->tp_value,
                               datap);
                  break;

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

#ifdef CONFIG_CRUNCH
            case PTRACE_GETCRUNCHREGS:
                  ret = ptrace_getcrunchregs(child, datap);
                  break;

            case PTRACE_SETCRUNCHREGS:
                  ret = ptrace_setcrunchregs(child, datap);
                  break;
#endif

#ifdef CONFIG_VFP
            case PTRACE_GETVFPREGS:
                  ret = ptrace_getvfpregs(child, datap);
                  break;

            case PTRACE_SETVFPREGS:
                  ret = ptrace_setvfpregs(child, datap);
                  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;
}

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