Logo Search packages:      
Sourcecode: linux version File versions  Download package

ptrace.c

/*
 * Copyright (C) 2004-2006 Atmel Corporation
 *
 * 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.
 */
#undef DEBUG
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/ptrace.h>
#include <linux/errno.h>
#include <linux/user.h>
#include <linux/security.h>
#include <linux/unistd.h>
#include <linux/notifier.h>

#include <asm/traps.h>
#include <asm/uaccess.h>
#include <asm/ocd.h>
#include <asm/mmu_context.h>
#include <linux/kdebug.h>

static struct pt_regs *get_user_regs(struct task_struct *tsk)
{
      return (struct pt_regs *)((unsigned long)task_stack_page(tsk) +
                          THREAD_SIZE - sizeof(struct pt_regs));
}

static void ptrace_single_step(struct task_struct *tsk)
{
      pr_debug("ptrace_single_step: pid=%u, PC=0x%08lx, SR=0x%08lx\n",
             tsk->pid, task_pt_regs(tsk)->pc, task_pt_regs(tsk)->sr);

      /*
       * We can't schedule in Debug mode, so when TIF_BREAKPOINT is
       * set, the system call or exception handler will do a
       * breakpoint to enter monitor mode before returning to
       * userspace.
       *
       * The monitor code will then notice that TIF_SINGLE_STEP is
       * set and return to userspace with single stepping enabled.
       * The CPU will then enter monitor mode again after exactly
       * one instruction has been executed, and the monitor code
       * will then send a SIGTRAP to the process.
       */
      set_tsk_thread_flag(tsk, TIF_BREAKPOINT);
      set_tsk_thread_flag(tsk, TIF_SINGLE_STEP);
}

/*
 * Called by kernel/ptrace.c when detaching
 *
 * Make sure any single step bits, etc. are not set
 */
void ptrace_disable(struct task_struct *child)
{
      clear_tsk_thread_flag(child, TIF_SINGLE_STEP);
      clear_tsk_thread_flag(child, TIF_BREAKPOINT);
}

/*
 * Read the word at offset "offset" into the task's "struct user". We
 * actually access the pt_regs struct stored on the kernel stack.
 */
static int ptrace_read_user(struct task_struct *tsk, unsigned long offset,
                      unsigned long __user *data)
{
      unsigned long *regs;
      unsigned long value;

      if (offset & 3 || offset >= sizeof(struct user)) {
            printk("ptrace_read_user: invalid offset 0x%08lx\n", offset);
            return -EIO;
      }

      regs = (unsigned long *)get_user_regs(tsk);

      value = 0;
      if (offset < sizeof(struct pt_regs))
            value = regs[offset / sizeof(regs[0])];

      pr_debug("ptrace_read_user(%s[%u], %#lx, %p) -> %#lx\n",
             tsk->comm, tsk->pid, offset, data, value);

      return put_user(value, data);
}

/*
 * Write the word "value" to offset "offset" into the task's "struct
 * user". We actually access the pt_regs struct stored on the kernel
 * stack.
 */
static int ptrace_write_user(struct task_struct *tsk, unsigned long offset,
                       unsigned long value)
{
      unsigned long *regs;

      pr_debug("ptrace_write_user(%s[%u], %#lx, %#lx)\n",
                  tsk->comm, tsk->pid, offset, value);

      if (offset & 3 || offset >= sizeof(struct user)) {
            pr_debug("  invalid offset 0x%08lx\n", offset);
            return -EIO;
      }

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

      regs = (unsigned long *)get_user_regs(tsk);
      regs[offset / sizeof(regs[0])] = value;

      return 0;
}

static int ptrace_getregs(struct task_struct *tsk, void __user *uregs)
{
      struct pt_regs *regs = get_user_regs(tsk);

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

static int ptrace_setregs(struct task_struct *tsk, const void __user *uregs)
{
      struct pt_regs newregs;
      int ret;

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

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

      return ret;
}

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

      pr_debug("ptrace: Enabling monitor mode...\n");
      ocd_write(DC, ocd_read(DC) | (1 << OCD_DC_MM_BIT)
                  | (1 << OCD_DC_DBE_BIT));

      switch (request) {
      /* Read the 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 in data 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 and stop at next (return from) syscall */
      case PTRACE_SYSCALL:
      /* restart after signal */
      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;
            /* XXX: Are we sure no breakpoints are active here? */
            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;
            wake_up_process(child);
            break;

      /*
       * execute single instruction.
       */
      case PTRACE_SINGLESTEP:
            ret = -EIO;
            if (!valid_signal(data))
                  break;
            clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
            ptrace_single_step(child);
            child->exit_code = data;
            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, (const void __user *)data);
            break;

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

      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) {
            pr_debug("syscall_trace: sending signal %d to PID %u\n",
                   current->exit_code, current->pid);
            send_sig(current->exit_code, current, 1);
            current->exit_code = 0;
      }
}

/*
 * debug_trampoline() is an assembly stub which will store all user
 * registers on the stack and execute a breakpoint instruction.
 *
 * If we single-step into an exception handler which runs with
 * interrupts disabled the whole time so it doesn't have to check for
 * pending work, its return address will be modified so that it ends
 * up returning to debug_trampoline.
 *
 * If the exception handler decides to store the user context and
 * enable interrupts after all, it will restore the original return
 * address and status register value. Before it returns, it will
 * notice that TIF_BREAKPOINT is set and execute a breakpoint
 * instruction.
 */
extern void debug_trampoline(void);

asmlinkage struct pt_regs *do_debug(struct pt_regs *regs)
{
      struct thread_info      *ti;
      unsigned long           trampoline_addr;
      u32               status;
      u32               ctrl;
      int               code;

      status = ocd_read(DS);
      ti = current_thread_info();
      code = TRAP_BRKPT;

      pr_debug("do_debug: status=0x%08x PC=0x%08lx SR=0x%08lx tif=0x%08lx\n",
                  status, regs->pc, regs->sr, ti->flags);

      if (!user_mode(regs)) {
            unsigned long     die_val = DIE_BREAKPOINT;

            if (status & (1 << OCD_DS_SSS_BIT))
                  die_val = DIE_SSTEP;

            if (notify_die(die_val, "ptrace", regs, 0, 0, SIGTRAP)
                        == NOTIFY_STOP)
                  return regs;

            if ((status & (1 << OCD_DS_SWB_BIT))
                        && test_and_clear_ti_thread_flag(
                              ti, TIF_BREAKPOINT)) {
                  /*
                   * Explicit breakpoint from trampoline or
                   * exception/syscall/interrupt handler.
                   *
                   * The real saved regs are on the stack right
                   * after the ones we saved on entry.
                   */
                  regs++;
                  pr_debug("  -> TIF_BREAKPOINT done, adjusted regs:"
                              "PC=0x%08lx SR=0x%08lx\n",
                              regs->pc, regs->sr);
                  BUG_ON(!user_mode(regs));

                  if (test_thread_flag(TIF_SINGLE_STEP)) {
                        pr_debug("Going to do single step...\n");
                        return regs;
                  }

                  /*
                   * No TIF_SINGLE_STEP means we're done
                   * stepping over a syscall. Do the trap now.
                   */
                  code = TRAP_TRACE;
            } else if ((status & (1 << OCD_DS_SSS_BIT))
                        && test_ti_thread_flag(ti, TIF_SINGLE_STEP)) {

                  pr_debug("Stepped into something, "
                              "setting TIF_BREAKPOINT...\n");
                  set_ti_thread_flag(ti, TIF_BREAKPOINT);

                  /*
                   * We stepped into an exception, interrupt or
                   * syscall handler. Some exception handlers
                   * don't check for pending work, so we need to
                   * set up a trampoline just in case.
                   *
                   * The exception entry code will undo the
                   * trampoline stuff if it does a full context
                   * save (which also means that it'll check for
                   * pending work later.)
                   */
                  if ((regs->sr & MODE_MASK) == MODE_EXCEPTION) {
                        trampoline_addr
                              = (unsigned long)&debug_trampoline;

                        pr_debug("Setting up trampoline...\n");
                        ti->rar_saved = sysreg_read(RAR_EX);
                        ti->rsr_saved = sysreg_read(RSR_EX);
                        sysreg_write(RAR_EX, trampoline_addr);
                        sysreg_write(RSR_EX, (MODE_EXCEPTION
                                          | SR_EM | SR_GM));
                        BUG_ON(ti->rsr_saved & MODE_MASK);
                  }

                  /*
                   * If we stepped into a system call, we
                   * shouldn't do a single step after we return
                   * since the return address is right after the
                   * "scall" instruction we were told to step
                   * over.
                   */
                  if ((regs->sr & MODE_MASK) == MODE_SUPERVISOR) {
                        pr_debug("Supervisor; no single step\n");
                        clear_ti_thread_flag(ti, TIF_SINGLE_STEP);
                  }

                  ctrl = ocd_read(DC);
                  ctrl &= ~(1 << OCD_DC_SS_BIT);
                  ocd_write(DC, ctrl);

                  return regs;
            } else {
                  printk(KERN_ERR "Unexpected OCD_DS value: 0x%08x\n",
                              status);
                  printk(KERN_ERR "Thread flags: 0x%08lx\n", ti->flags);
                  die("Unhandled debug trap in kernel mode",
                              regs, SIGTRAP);
            }
      } else if (status & (1 << OCD_DS_SSS_BIT)) {
            /* Single step in user mode */
            code = TRAP_TRACE;

            ctrl = ocd_read(DC);
            ctrl &= ~(1 << OCD_DC_SS_BIT);
            ocd_write(DC, ctrl);
      }

      pr_debug("Sending SIGTRAP: code=%d PC=0x%08lx SR=0x%08lx\n",
                  code, regs->pc, regs->sr);

      clear_thread_flag(TIF_SINGLE_STEP);
      _exception(SIGTRAP, regs, code, instruction_pointer(regs));

      return regs;
}

Generated by  Doxygen 1.6.0   Back to index