ptrace.c

上传linux-jx2410的源代码

	    }
	    break;
	}

	return alt;
}

static int
add_breakpoint_arm(struct task_struct *child, struct debug_info *dbg, unsigned long addr)
{
	int nr = dbg->nsaved;
	int res = -EINVAL;

	if (nr < 2) {
		res = read_tsk_long(child, addr, &dbg->bp[nr].insn);
		if (res == 0)
			res = write_tsk_long(child, addr, BREAKINST_ARM);

		if (res == 0) {
			dbg->bp[nr].address = addr;
			dbg->nsaved += 1;
		}
	} else
		printk(KERN_ERR "ptrace: too many breakpoints\n");

	return res;
}

int ptrace_set_bpt(struct task_struct *child)
{
	struct pt_regs *regs;
	unsigned long pc, insn;
	int res;

	regs = get_user_regs(child);
	pc = instruction_pointer(regs);

	res = read_tsk_long(child, pc, &insn);
	if (!res) {
		struct debug_info *dbg = &child->thread.debug;
		unsigned long alt;

		dbg->nsaved = 0;

		alt = get_branch_address(child, pc, insn);
		if (alt)
			res = add_breakpoint_arm(child, dbg, alt);

		/*
		 * Note that we ignore the result of setting the above
		 * breakpoint since it may fail.  When it does, this is
		 * not so much an error, but a forewarning that we may
		 * be receiving a prefetch abort shortly.
		 *
		 * If we don't set this breakpoint here, then we can
		 * loose control of the thread during single stepping.
		 */
		if (!alt || predicate(insn) != PREDICATE_ALWAYS)
			res = add_breakpoint_arm(child, dbg, pc + 4);
	}

	return res;
}

/*
 * Ensure no single-step breakpoint is pending.  Returns non-zero
 * value if child was being single-stepped.
 */
void __ptrace_cancel_bpt(struct task_struct *child)
{
	struct debug_info *dbg = &child->thread.debug;
	int i, nsaved = dbg->nsaved;

	dbg->nsaved = 0;

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

	for (i = 0; i < nsaved; i++) {
		unsigned long tmp;

		read_tsk_long(child, dbg->bp[i].address, &tmp);
		write_tsk_long(child, dbg->bp[i].address, dbg->bp[i].insn);
		if (tmp != BREAKINST_ARM)
			printk(KERN_ERR "ptrace_cancel_bpt: weirdness\n");
	}
}

/*
 * 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);
}

static int do_ptrace(int request, struct task_struct *child, long addr, long data)
{
	unsigned long tmp;
	int ret;

	switch (request) {
		/*
		 * read word at location "addr" in the child process.
		 */
		case PTRACE_PEEKTEXT:
		case PTRACE_PEEKDATA:
			ret = read_tsk_long(child, addr, &tmp);
			if (!ret)
				ret = put_user(tmp, (unsigned long *) data);
			break;

		/*
		 * read the word at location "addr" in the user registers.
		 */
		case PTRACE_PEEKUSR:
			ret = -EIO;
			if ((addr & 3) || addr < 0 || addr >= sizeof(struct user))
				break;

			tmp = 0;  /* Default return condition */
			if (addr < sizeof(struct pt_regs))
				tmp = get_stack_long(child, (int)addr >> 2);
			ret = put_user(tmp, (unsigned long *)data);
			break;

		/*
		 * write the word at location addr.
		 */
		case PTRACE_POKETEXT:
		case PTRACE_POKEDATA:
			ret = write_tsk_long(child, addr, data);
			break;

		/*
		 * write the word at location addr in the user registers.
		 */
		case PTRACE_POKEUSR:
			ret = -EIO;
			if ((addr & 3) || addr < 0 || addr >= sizeof(struct user))
				break;

			if (addr < sizeof(struct pt_regs))
				ret = put_stack_long(child, (int)addr >> 2, data);
			break;

		/*
		 * continue/restart and stop at next (return from) syscall
		 */
		case PTRACE_SYSCALL:
		case PTRACE_CONT:
			ret = -EIO;
			if ((unsigned long) data > _NSIG)
				break;
			if (request == PTRACE_SYSCALL)
				child->ptrace |= PT_TRACESYS;
			else
				child->ptrace &= ~PT_TRACESYS;
			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:
			/* already dead */
			ret = 0;
			if (child->state == TASK_ZOMBIE)
				break;
			child->exit_code = SIGKILL;
			/* make sure single-step breakpoint is gone. */
			__ptrace_cancel_bpt(child);
			wake_up_process(child);
			ret = 0;
			break;

		/*
		 * execute single instruction.
		 */
		case PTRACE_SINGLESTEP:
			ret = -EIO;
			if ((unsigned long) data > _NSIG)
				break;
			child->thread.debug.nsaved = -1;
			child->ptrace &= ~PT_TRACESYS;
			child->exit_code = data;
			/* give it a chance to run. */
			wake_up_process(child);
			ret = 0;
			break;

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

		/*
		 * Get all gp regs from the child.
		 */
		case PTRACE_GETREGS: {
			struct pt_regs *regs = get_user_regs(child);

			ret = 0;
			if (copy_to_user((void *)data, regs,
					 sizeof(struct pt_regs)))
				ret = -EFAULT;

			break;
		}

		/*
		 * Set all gp regs in the child.
		 */
		case PTRACE_SETREGS: {
			struct pt_regs newregs;

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

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

		/*
		 * Get the child FPU state.
		 */
		case PTRACE_GETFPREGS:
			ret = -EIO;
			if (!access_ok(VERIFY_WRITE, (void *)data, sizeof(struct user_fp)))
				break;

			/* we should check child->used_math here */
			ret = __copy_to_user((void *)data, &child->thread.fpstate,
					     sizeof(struct user_fp)) ? -EFAULT : 0;
			break;
		
		/*
		 * Set the child FPU state.
		 */
		case PTRACE_SETFPREGS:
			ret = -EIO;
			if (!access_ok(VERIFY_READ, (void *)data, sizeof(struct user_fp)))
				break;

			child->used_math = 1;
			ret = __copy_from_user(&child->thread.fpstate, (void *)data,
					   sizeof(struct user_fp)) ? -EFAULT : 0;
			break;

		default:
			ret = -EIO;
			break;
	}

	return ret;
}

asmlinkage int sys_ptrace(long request, long pid, long addr, long data)
{
	struct task_struct *child;
	int ret;

	lock_kernel();
	ret = -EPERM;
	if (request == PTRACE_TRACEME) {
		/* are we already being traced? */
		if (current->ptrace & PT_PTRACED)
			goto out;
		/* set the ptrace bit in the process flags. */
		current->ptrace |= PT_PTRACED;
		ret = 0;
		goto out;
	}
	ret = -ESRCH;
	read_lock(&tasklist_lock);
	child = find_task_by_pid(pid);
	if (child)
		get_task_struct(child);
	read_unlock(&tasklist_lock);
	if (!child)
		goto out;

	ret = -EPERM;
	if (pid == 1)		/* you may not mess with init */
		goto out_tsk;

	if (request == PTRACE_ATTACH) {
		ret = ptrace_attach(child);
		goto out_tsk;
	}
	ret = -ESRCH;
	if (!(child->ptrace & PT_PTRACED))
		goto out_tsk;
	if (child->state != TASK_STOPPED && request != PTRACE_KILL)
		goto out_tsk;
	if (child->p_pptr != current)
		goto out_tsk;

	ret = do_ptrace(request, child, addr, data);

out_tsk:
	free_task_struct(child);
out:
	unlock_kernel();
	return ret;
}

asmlinkage void syscall_trace(int why, struct pt_regs *regs)
{
	unsigned long ip;

	if ((current->ptrace & (PT_PTRACED|PT_TRACESYS))
			!= (PT_PTRACED|PT_TRACESYS))
		return;

	/*
	 * Save IP.  IP is used to denote syscall entry/exit:
	 *  IP = 0 -> entry, = 1 -> exit
	 */
	ip = regs->ARM_ip;
	regs->ARM_ip = why;

	/* the 0x80 provides a way for the tracing parent to distinguish
	   between a syscall stop and SIGTRAP delivery */
	current->exit_code = SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD)
					? 0x80 : 0);
	current->state = TASK_STOPPED;
	notify_parent(current, SIGCHLD);
	schedule();
	/*
	 * 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;
	}
	regs->ARM_ip = ip;
}