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ptrace.c

/* ptrace.c */
/* By Ross Biro 1/23/92 */
/* edited by Linus Torvalds */
/* mangled further by Bob Manson (manson@santafe.edu) */
/* more mutilation by David Mosberger (davidm@azstarnet.com) */

#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/smp_lock.h>
#include <linux/errno.h>
#include <linux/ptrace.h>
#include <linux/user.h>
#include <linux/slab.h>
#include <linux/security.h>
#include <linux/signal.h>

#include <asm/uaccess.h>
#include <asm/pgtable.h>
#include <asm/system.h>
#include <asm/fpu.h>

#include "proto.h"

#define DEBUG     DBG_MEM
#undef DEBUG

#ifdef DEBUG
enum {
      DBG_MEM           = (1<<0),
      DBG_BPT           = (1<<1),
      DBG_MEM_ALL = (1<<2)
};
#define DBG(fac,args)   {if ((fac) & DEBUG) printk args;}
#else
#define DBG(fac,args)
#endif

#define BREAKINST 0x00000080  /* call_pal bpt */

/*
 * does not yet catch signals sent when the child dies.
 * in exit.c or in signal.c.
 */

/*
 * Processes always block with the following stack-layout:
 *
 *  +================================+ <---- task + 2*PAGE_SIZE
 *  | PALcode saved frame (ps, pc,   | ^
 *  | gp, a0, a1, a2)              | |
 *  +================================+ | struct pt_regs
 *  |                        | |
 *  | frame generated by SAVE_ALL    | |
 *  |                        | v
 *  +================================+
 *  |                        | ^
 *  | frame saved by do_switch_stack | | struct switch_stack
 *  |                        | v
 *  +================================+
 */

/* 
 * The following table maps a register index into the stack offset at
 * which the register is saved.  Register indices are 0-31 for integer
 * regs, 32-63 for fp regs, and 64 for the pc.  Notice that sp and
 * zero have no stack-slot and need to be treated specially (see
 * get_reg/put_reg below).
 */
enum {
      REG_R0 = 0, REG_F0 = 32, REG_FPCR = 63, REG_PC = 64
};

#define PT_REG(reg) \
  (PAGE_SIZE*2 - sizeof(struct pt_regs) + offsetof(struct pt_regs, reg))

#define SW_REG(reg) \
 (PAGE_SIZE*2 - sizeof(struct pt_regs) - sizeof(struct switch_stack) \
  + offsetof(struct switch_stack, reg))

static int regoff[] = {
      PT_REG(        r0), PT_REG(      r1), PT_REG(      r2), PT_REG(     r3),
      PT_REG(        r4), PT_REG(      r5), PT_REG(      r6), PT_REG(     r7),
      PT_REG(        r8), SW_REG(      r9), SW_REG(     r10), SW_REG(    r11),
      SW_REG(       r12), SW_REG(     r13), SW_REG(     r14), SW_REG(    r15),
      PT_REG(       r16), PT_REG(     r17), PT_REG(     r18), PT_REG(    r19),
      PT_REG(       r20), PT_REG(     r21), PT_REG(     r22), PT_REG(    r23),
      PT_REG(       r24), PT_REG(     r25), PT_REG(     r26), PT_REG(    r27),
      PT_REG(       r28), PT_REG(      gp),              -1,               -1,
      SW_REG(fp[ 0]), SW_REG(fp[ 1]), SW_REG(fp[ 2]), SW_REG(fp[ 3]),
      SW_REG(fp[ 4]), SW_REG(fp[ 5]), SW_REG(fp[ 6]), SW_REG(fp[ 7]),
      SW_REG(fp[ 8]), SW_REG(fp[ 9]), SW_REG(fp[10]), SW_REG(fp[11]),
      SW_REG(fp[12]), SW_REG(fp[13]), SW_REG(fp[14]), SW_REG(fp[15]),
      SW_REG(fp[16]), SW_REG(fp[17]), SW_REG(fp[18]), SW_REG(fp[19]),
      SW_REG(fp[20]), SW_REG(fp[21]), SW_REG(fp[22]), SW_REG(fp[23]),
      SW_REG(fp[24]), SW_REG(fp[25]), SW_REG(fp[26]), SW_REG(fp[27]),
      SW_REG(fp[28]), SW_REG(fp[29]), SW_REG(fp[30]), SW_REG(fp[31]),
      PT_REG(        pc)
};

static unsigned long zero;

/*
 * Get address of register REGNO in task TASK.
 */
static unsigned long *
get_reg_addr(struct task_struct * task, unsigned long regno)
{
      unsigned long *addr;

      if (regno == 30) {
            addr = &task_thread_info(task)->pcb.usp;
      } else if (regno == 65) {
            addr = &task_thread_info(task)->pcb.unique;
      } else if (regno == 31 || regno > 65) {
            zero = 0;
            addr = &zero;
      } else {
            addr = task_stack_page(task) + regoff[regno];
      }
      return addr;
}

/*
 * Get contents of register REGNO in task TASK.
 */
static unsigned long
get_reg(struct task_struct * task, unsigned long regno)
{
      /* Special hack for fpcr -- combine hardware and software bits.  */
      if (regno == 63) {
            unsigned long fpcr = *get_reg_addr(task, regno);
            unsigned long swcr
              = task_thread_info(task)->ieee_state & IEEE_SW_MASK;
            swcr = swcr_update_status(swcr, fpcr);
            return fpcr | swcr;
      }
      return *get_reg_addr(task, regno);
}

/*
 * Write contents of register REGNO in task TASK.
 */
static int
put_reg(struct task_struct *task, unsigned long regno, unsigned long data)
{
      if (regno == 63) {
            task_thread_info(task)->ieee_state
              = ((task_thread_info(task)->ieee_state & ~IEEE_SW_MASK)
                 | (data & IEEE_SW_MASK));
            data = (data & FPCR_DYN_MASK) | ieee_swcr_to_fpcr(data);
      }
      *get_reg_addr(task, regno) = data;
      return 0;
}

static inline int
read_int(struct task_struct *task, unsigned long addr, int * data)
{
      int copied = access_process_vm(task, addr, data, sizeof(int), 0);
      return (copied == sizeof(int)) ? 0 : -EIO;
}

static inline int
write_int(struct task_struct *task, unsigned long addr, int data)
{
      int copied = access_process_vm(task, addr, &data, sizeof(int), 1);
      return (copied == sizeof(int)) ? 0 : -EIO;
}

/*
 * Set breakpoint.
 */
int
ptrace_set_bpt(struct task_struct * child)
{
      int displ, i, res, reg_b, nsaved = 0;
      unsigned int insn, op_code;
      unsigned long pc;

      pc  = get_reg(child, REG_PC);
      res = read_int(child, pc, (int *) &insn);
      if (res < 0)
            return res;

      op_code = insn >> 26;
      if (op_code >= 0x30) {
            /*
             * It's a branch: instead of trying to figure out
             * whether the branch will be taken or not, we'll put
             * a breakpoint at either location.  This is simpler,
             * more reliable, and probably not a whole lot slower
             * than the alternative approach of emulating the
             * branch (emulation can be tricky for fp branches).
             */
            displ = ((s32)(insn << 11)) >> 9;
            task_thread_info(child)->bpt_addr[nsaved++] = pc + 4;
            if (displ)        /* guard against unoptimized code */
                  task_thread_info(child)->bpt_addr[nsaved++]
                    = pc + 4 + displ;
            DBG(DBG_BPT, ("execing branch\n"));
      } else if (op_code == 0x1a) {
            reg_b = (insn >> 16) & 0x1f;
            task_thread_info(child)->bpt_addr[nsaved++] = get_reg(child, reg_b);
            DBG(DBG_BPT, ("execing jump\n"));
      } else {
            task_thread_info(child)->bpt_addr[nsaved++] = pc + 4;
            DBG(DBG_BPT, ("execing normal insn\n"));
      }

      /* install breakpoints: */
      for (i = 0; i < nsaved; ++i) {
            res = read_int(child, task_thread_info(child)->bpt_addr[i],
                         (int *) &insn);
            if (res < 0)
                  return res;
            task_thread_info(child)->bpt_insn[i] = insn;
            DBG(DBG_BPT, ("    -> next_pc=%lx\n",
                        task_thread_info(child)->bpt_addr[i]));
            res = write_int(child, task_thread_info(child)->bpt_addr[i],
                        BREAKINST);
            if (res < 0)
                  return res;
      }
      task_thread_info(child)->bpt_nsaved = nsaved;
      return 0;
}

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

      task_thread_info(child)->bpt_nsaved = 0;

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

      for (i = 0; i < nsaved; ++i) {
            write_int(child, task_thread_info(child)->bpt_addr[i],
                    task_thread_info(child)->bpt_insn[i]);
      }
      return (nsaved != 0);
}

/*
 * Called by kernel/ptrace.c when detaching..
 *
 * Make sure the single step bit is not set.
 */
void ptrace_disable(struct task_struct *child)
{ 
      ptrace_cancel_bpt(child);
}

asmlinkage long
do_sys_ptrace(long request, long pid, long addr, long data,
            struct pt_regs *regs)
{
      struct task_struct *child;
      unsigned long tmp;
      size_t copied;
      long ret;

      lock_kernel();
      DBG(DBG_MEM, ("request=%ld pid=%ld addr=0x%lx data=0x%lx\n",
                  request, pid, addr, data));
      if (request == PTRACE_TRACEME) {
            ret = ptrace_traceme();
            goto out_notsk;
      }

      child = ptrace_get_task_struct(pid);
      if (IS_ERR(child)) {
            ret = PTR_ERR(child);
            goto out_notsk;
      }

      if (request == PTRACE_ATTACH) {
            ret = ptrace_attach(child);
            goto out;
      }

      ret = ptrace_check_attach(child, request == PTRACE_KILL);
      if (ret < 0)
            goto out;

      switch (request) {
      /* When I and D space are separate, these will need to be fixed.  */
      case PTRACE_PEEKTEXT: /* read word at location addr. */
      case PTRACE_PEEKDATA:
            copied = access_process_vm(child, addr, &tmp, sizeof(tmp), 0);
            ret = -EIO;
            if (copied != sizeof(tmp))
                  break;
            
            regs->r0 = 0;     /* special return: no errors */
            ret = tmp;
            break;

      /* Read register number ADDR. */
      case PTRACE_PEEKUSR:
            regs->r0 = 0;     /* special return: no errors */
            ret = get_reg(child, addr);
            DBG(DBG_MEM, ("peek $%ld->%#lx\n", addr, ret));
            break;

      /* When I and D space are separate, this will have to be fixed.  */
      case PTRACE_POKETEXT: /* write the word at location addr. */
      case PTRACE_POKEDATA:
            tmp = data;
            copied = access_process_vm(child, addr, &tmp, sizeof(tmp), 1);
            ret = (copied == sizeof(tmp)) ? 0 : -EIO;
            break;

      case PTRACE_POKEUSR: /* write the specified register */
            DBG(DBG_MEM, ("poke $%ld<-%#lx\n", addr, data));
            ret = put_reg(child, addr, data);
            break;

      case PTRACE_SYSCALL:
            /* continue and stop at next (return from) syscall */
      case PTRACE_CONT:    /* restart after signal. */
            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;
            /* make sure single-step breakpoint is gone. */
            ptrace_cancel_bpt(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:
            ret = 0;
            if (child->exit_state == EXIT_ZOMBIE)
                  break;
            child->exit_code = SIGKILL;
            /* make sure single-step breakpoint is gone. */
            ptrace_cancel_bpt(child);
            wake_up_process(child);
            goto out;

      case PTRACE_SINGLESTEP:  /* execute single instruction. */
            ret = -EIO;
            if (!valid_signal(data))
                  break;
            /* Mark single stepping.  */
            task_thread_info(child)->bpt_nsaved = -1;
            clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
            child->exit_code = data;
            wake_up_process(child);
            /* give it a chance to run. */
            ret = 0;
            goto out;

      case PTRACE_DETACH:      /* detach a process that was attached. */
            ret = ptrace_detach(child, data);
            goto out;

      default:
            ret = ptrace_request(child, request, addr, data);
            goto out;
      }
 out:
      put_task_struct(child);
 out_notsk:
      unlock_kernel();
      return ret;
}

asmlinkage void
syscall_trace(void)
{
      if (!test_thread_flag(TIF_SYSCALL_TRACE))
            return;
      if (!(current->ptrace & PT_PTRACED))
            return;
      /* 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;
      }
}

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