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ptrace.c

/*
 * `ptrace' system call
 *
 * Copyright (C) 2008-2009 Michal Simek <monstr@monstr.eu>
 * Copyright (C) 2007-2009 PetaLogix
 * Copyright (C) 2004-2007 John Williams <john.williams@petalogix.com>
 *
 * derived from arch/v850/kernel/ptrace.c
 *
 * Copyright (C) 2002,03 NEC Electronics Corporation
 * Copyright (C) 2002,03 Miles Bader <miles@gnu.org>
 *
 * Derived from arch/mips/kernel/ptrace.c:
 *
 * Copyright (C) 1992 Ross Biro
 * Copyright (C) Linus Torvalds
 * Copyright (C) 1994, 95, 96, 97, 98, 2000 Ralf Baechle
 * Copyright (C) 1996 David S. Miller
 * Kevin D. Kissell, kevink@mips.com and Carsten Langgaard, carstenl@mips.com
 * Copyright (C) 1999 MIPS Technologies, Inc.
 *
 * This file is subject to the terms and conditions of the GNU General
 * Public License. See the file COPYING in the main directory of this
 * archive for more details.
 */

#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/ptrace.h>
#include <linux/signal.h>
#include <linux/elf.h>
#include <linux/audit.h>
#include <linux/seccomp.h>
#include <linux/tracehook.h>

#include <linux/errno.h>
#include <asm/processor.h>
#include <linux/uaccess.h>
#include <asm/asm-offsets.h>

/* Returns the address where the register at REG_OFFS in P is stashed away. */
static microblaze_reg_t *reg_save_addr(unsigned reg_offs,
                              struct task_struct *t)
{
      struct pt_regs *regs;

      /*
       * Three basic cases:
       *
       * (1)      A register normally saved before calling the scheduler, is
       *    available in the kernel entry pt_regs structure at the top
       *    of the kernel stack. The kernel trap/irq exit path takes
       *    care to save/restore almost all registers for ptrace'd
       *    processes.
       *
       * (2)      A call-clobbered register, where the process P entered the
       *    kernel via [syscall] trap, is not stored anywhere; that's
       *    OK, because such registers are not expected to be preserved
       *    when the trap returns anyway (so we don't actually bother to
       *    test for this case).
       *
       * (3)      A few registers not used at all by the kernel, and so
       *    normally never saved except by context-switches, are in the
       *    context switch state.
       */

      /* Register saved during kernel entry (or not available). */
      regs = task_pt_regs(t);

      return (microblaze_reg_t *)((char *)regs + reg_offs);
}

long arch_ptrace(struct task_struct *child, long request, long addr, long data)
{
      int rval;
      unsigned long val = 0;
      unsigned long copied;

      switch (request) {
      case PTRACE_PEEKTEXT: /* read word at location addr. */
      case PTRACE_PEEKDATA:
            pr_debug("PEEKTEXT/PEEKDATA at %08lX\n", addr);
            copied = access_process_vm(child, addr, &val, sizeof(val), 0);
            rval = -EIO;
            if (copied != sizeof(val))
                  break;
            rval = put_user(val, (unsigned long *)data);
            break;

      case PTRACE_POKETEXT: /* write the word at location addr. */
      case PTRACE_POKEDATA:
            pr_debug("POKETEXT/POKEDATA to %08lX\n", addr);
            rval = 0;
            if (access_process_vm(child, addr, &data, sizeof(data), 1)
                == sizeof(data))
                  break;
            rval = -EIO;
            break;

      /* Read/write the word at location ADDR in the registers. */
      case PTRACE_PEEKUSR:
      case PTRACE_POKEUSR:
            pr_debug("PEEKUSR/POKEUSR : 0x%08lx\n", addr);
            rval = 0;
            if (addr >= PT_SIZE && request == PTRACE_PEEKUSR) {
                  /*
                   * Special requests that don't actually correspond
                   * to offsets in struct pt_regs.
                   */
                  if (addr == PT_TEXT_ADDR) {
                        val = child->mm->start_code;
                  } else if (addr == PT_DATA_ADDR) {
                        val = child->mm->start_data;
                  } else if (addr == PT_TEXT_LEN) {
                        val = child->mm->end_code
                              - child->mm->start_code;
                  } else {
                        rval = -EIO;
                  }
            } else if (addr >= 0 && addr < PT_SIZE && (addr & 0x3) == 0) {
                  microblaze_reg_t *reg_addr = reg_save_addr(addr, child);
                  if (request == PTRACE_PEEKUSR)
                        val = *reg_addr;
                  else
                        *reg_addr = data;
            } else
                  rval = -EIO;

            if (rval == 0 && request == PTRACE_PEEKUSR)
                  rval = put_user(val, (unsigned long *)data);
            break;
      /* Continue and stop at next (return from) syscall */
      case PTRACE_SYSCALL:
            pr_debug("PTRACE_SYSCALL\n");
      case PTRACE_SINGLESTEP:
            pr_debug("PTRACE_SINGLESTEP\n");
      /* Restart after a signal.  */
      case PTRACE_CONT:
            pr_debug("PTRACE_CONT\n");
            rval = -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;
            pr_debug("wakeup_process\n");
            wake_up_process(child);
            rval = 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:
            pr_debug("PTRACE_KILL\n");
            rval = 0;
            if (child->exit_state == EXIT_ZOMBIE)     /* already dead */
                  break;
            child->exit_code = SIGKILL;
            wake_up_process(child);
            break;

      case PTRACE_DETACH: /* detach a process that was attached. */
            pr_debug("PTRACE_DETACH\n");
            rval = ptrace_detach(child, data);
            break;
      default:
            /* rval = ptrace_request(child, request, addr, data); noMMU */
            rval = -EIO;
      }
      return rval;
}

asmlinkage long do_syscall_trace_enter(struct pt_regs *regs)
{
      long ret = 0;

      secure_computing(regs->r12);

      if (test_thread_flag(TIF_SYSCALL_TRACE) &&
          tracehook_report_syscall_entry(regs))
            /*
             * Tracing decided this syscall should not happen.
             * We'll return a bogus call number to get an ENOSYS
             * error, but leave the original number in regs->regs[0].
             */
            ret = -1L;

      if (unlikely(current->audit_context))
            audit_syscall_entry(EM_XILINX_MICROBLAZE, regs->r12,
                            regs->r5, regs->r6,
                            regs->r7, regs->r8);

      return ret ?: regs->r12;
}

asmlinkage void do_syscall_trace_leave(struct pt_regs *regs)
{
      int step;

      if (unlikely(current->audit_context))
            audit_syscall_exit(AUDITSC_RESULT(regs->r3), regs->r3);

      step = test_thread_flag(TIF_SINGLESTEP);
      if (step || test_thread_flag(TIF_SYSCALL_TRACE))
            tracehook_report_syscall_exit(regs, step);
}

#if 0
static 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;
      }
}
#endif

void ptrace_disable(struct task_struct *child)
{
      /* nothing to do */
}

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