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ptrace.c

/*
 * Copyright (C) 2000-2003, Axis Communications AB.
 */

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

#include <asm/uaccess.h>
#include <asm/page.h>
#include <asm/pgtable.h>
#include <asm/system.h>
#include <asm/processor.h>

/* 
 * Determines which bits in DCCR the user has access to.
 * 1 = access, 0 = no access.
 */
#define DCCR_MASK 0x0000001f     /* XNZVC */

/*
 * Get contents of register REGNO in task TASK.
 */
inline long get_reg(struct task_struct *task, unsigned int regno)
{
      /* USP is a special case, it's not in the pt_regs struct but
       * in the tasks thread struct
       */

      if (regno == PT_USP)
            return task->thread.usp;
      else if (regno < PT_MAX)
            return ((unsigned long *)task_pt_regs(task))[regno];
      else
            return 0;
}

/*
 * Write contents of register REGNO in task TASK.
 */
inline int put_reg(struct task_struct *task, unsigned int regno,
                    unsigned long data)
{
      if (regno == PT_USP)
            task->thread.usp = data;
      else if (regno < PT_MAX)
            ((unsigned long *)task_pt_regs(task))[regno] = data;
      else
            return -1;
      return 0;
}

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

/* 
 * Note that this implementation of ptrace behaves differently from vanilla
 * ptrace.  Contrary to what the man page says, in the PTRACE_PEEKTEXT,
 * PTRACE_PEEKDATA, and PTRACE_PEEKUSER requests the data variable is not
 * ignored.  Instead, the data variable is expected to point at a location
 * (in user space) where the result of the ptrace call is written (instead of
 * being returned).
 */
long arch_ptrace(struct task_struct *child, long request, long addr, long data)
{
      int ret;
      unsigned long __user *datap = (unsigned long __user *)data;

      switch (request) {
            /* Read word at location address. */ 
            case PTRACE_PEEKTEXT:
            case PTRACE_PEEKDATA:
                  ret = generic_ptrace_peekdata(child, addr, data);
                  break;

            /* Read the word at location address in the USER area. */
            case PTRACE_PEEKUSR: {
                  unsigned long tmp;

                  ret = -EIO;
                  if ((addr & 3) || addr < 0 || addr > PT_MAX << 2)
                        break;

                  tmp = get_reg(child, addr >> 2);
                  ret = put_user(tmp, datap);
                  break;
            }
            
            /* Write the word at location address. */
            case PTRACE_POKETEXT:
            case PTRACE_POKEDATA:
                  ret = generic_ptrace_pokedata(child, addr, data);
                  break;
 
            /* Write the word at location address in the USER area. */
            case PTRACE_POKEUSR:
                  ret = -EIO;
                  if ((addr & 3) || addr < 0 || addr > PT_MAX << 2)
                        break;

                  addr >>= 2;

                  if (addr == PT_DCCR) {
                        /* don't allow the tracing process to change stuff like
                         * interrupt enable, kernel/user bit, dma enables etc.
                         */
                        data &= DCCR_MASK;
                        data |= get_reg(child, PT_DCCR) & ~DCCR_MASK;
                  }
                  if (put_reg(child, addr, data))
                        break;
                  ret = 0;
                  break;

            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;
                  
                  /* TODO: make sure any pending breakpoint is killed */
                  wake_up_process(child);
                  ret = 0;
                  
                  break;
            
            /* Make the child exit by sending it a sigkill. */
            case PTRACE_KILL:
                  ret = 0;
                  
                  if (child->exit_state == EXIT_ZOMBIE)
                        break;
                  
                  child->exit_code = SIGKILL;
                  
                  /* TODO: make sure any pending breakpoint is killed */
                  wake_up_process(child);
                  break;

            /* Set the trap flag. */
            case PTRACE_SINGLESTEP:
                  ret = -EIO;
                  
                  if (!valid_signal(data))
                        break;
                  
                  clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);

                  /* TODO: set some clever breakpoint mechanism... */

                  child->exit_code = data;
                  wake_up_process(child);
                  ret = 0;
                  break;

            /* Get all GP registers from the child. */
            case PTRACE_GETREGS: {
                  int i;
                  unsigned long tmp;
                  
                  ret = 0;
                  for (i = 0; i <= PT_MAX; i++) {
                        tmp = get_reg(child, i);
                        
                        if (put_user(tmp, datap)) {
                              ret = -EFAULT;
                              break;
                        }
                        
                        data += sizeof(long);
                  }

                  break;
            }

            /* Set all GP registers in the child. */
            case PTRACE_SETREGS: {
                  int i;
                  unsigned long tmp;
                  
                  ret = 0;
                  for (i = 0; i <= PT_MAX; i++) {
                        if (get_user(tmp, datap)) {
                              ret = -EFAULT;
                              break;
                        }
                        
                        if (i == PT_DCCR) {
                              tmp &= DCCR_MASK;
                              tmp |= get_reg(child, PT_DCCR) & ~DCCR_MASK;
                        }
                        
                        put_reg(child, i, tmp);
                        data += sizeof(long);
                  }
                  
                  break;
            }

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

      return ret;
}

void do_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.
       */
      if (current->exit_code) {
            send_sig(current->exit_code, current, 1);
            current->exit_code = 0;
      }
}

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