/*
   * 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));
  }

  void user_enable_single_step(struct task_struct *tsk)

  {

  	pr_debug("user_enable_single_step: pid=%u, PC=0x%08lx, SR=0x%08lx
  ",

  		 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);
  }

  void user_disable_single_step(struct task_struct *child)
  {
  	/* XXX(hch): a no-op here seems wrong.. */
  }

  /*
   * 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);

  	ocd_disable(child);

  }
  
  /*
   * 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
  ", 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
  ",
  		 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)
  ",
  			tsk->comm, tsk->pid, offset, value);

  	if (offset & 3 || offset >= sizeof(struct user)) {

  		pr_debug("  invalid offset 0x%08lx
  ", 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,
  		 unsigned long addr, unsigned long data)

  {

  	int ret;

  	void __user *datap = (void __user *) data;

  	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, datap);

  		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;

  	case PTRACE_GETREGS:

  		ret = ptrace_getregs(child, datap);

  		break;
  
  	case PTRACE_SETREGS:

  		ret = ptrace_setregs(child, datap);

  		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
  ",
  			 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
  ",
  			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
  ",
  					regs->pc, regs->sr);
  			BUG_ON(!user_mode(regs));
  
  			if (test_thread_flag(TIF_SINGLE_STEP)) {
  				pr_debug("Going to do single step...
  ");
  				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...
  ");
  			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...
  ");
  				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
  ");
  				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
  ",
  					status);
  			printk(KERN_ERR "Thread flags: 0x%08lx
  ", 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
  ",
  			code, regs->pc, regs->sr);

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

  }