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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 <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

/*
 * 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]);
}

/*
 * Called by kernel/ptrace.c when detaching..
 */
void ptrace_disable(struct task_struct *child)
{
      single_step_disable(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 __init ptrace_break_init(void)
{
      register_undef_hook(&arm_break_hook);
      register_undef_hook(&thumb_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_state(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_state(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;

      return 0;
}
#endif

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

      switch (request) {
            /*
             * read word at location "addr" in the child process.
             */
            case PTRACE_PEEKTEXT:
            case PTRACE_PEEKDATA:
                  ret = generic_ptrace_peekdata(child, addr, data);
                  break;

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

            /*
             * write the word at location addr.
             */
            case PTRACE_POKETEXT:
            case PTRACE_POKEDATA:
                  ret = generic_ptrace_pokedata(child, addr, data);
                  break;

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

            /*
             * continue/restart and stop at next (return from) syscall
             */
            case PTRACE_SYSCALL:
            case PTRACE_CONT:
                  ret = -EIO;
                  if (!valid_signal(data))
                        break;
                  if (request == PTRACE_SYSCALL)
                        set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
                  else
                        clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
                  child->exit_code = data;
                  single_step_disable(child);
                  wake_up_process(child);
                  ret = 0;
                  break;

            /*
             * make the child exit.  Best I can do is send it a sigkill.
             * perhaps it should be put in the status that it wants to
             * exit.
             */
            case PTRACE_KILL:
                  single_step_disable(child);
                  if (child->exit_state != EXIT_ZOMBIE) {
                        child->exit_code = SIGKILL;
                        wake_up_process(child);
                  }
                  ret = 0;
                  break;

            /*
             * execute single instruction.
             */
            case PTRACE_SINGLESTEP:
                  ret = -EIO;
                  if (!valid_signal(data))
                        break;
                  single_step_enable(child);
                  clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
                  child->exit_code = data;
                  /* give it a chance to run. */
                  wake_up_process(child);
                  ret = 0;
                  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

            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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