ptrace.c revision 1eeb66a1bb973534dc3d064920a5ca683823372e 
1/*
2 * Copyright (C) 2004-2006 Atmel Corporation
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License version 2 as
6 * published by the Free Software Foundation.
7 */
8#undef DEBUG
9#include <linux/kernel.h>
10#include <linux/sched.h>
11#include <linux/mm.h>
12#include <linux/smp_lock.h>
13#include <linux/ptrace.h>
14#include <linux/errno.h>
15#include <linux/user.h>
16#include <linux/security.h>
17#include <linux/unistd.h>
18#include <linux/notifier.h>
19
20#include <asm/traps.h>
21#include <asm/uaccess.h>
22#include <asm/ocd.h>
23#include <asm/mmu_context.h>
24#include <linux/kdebug.h>
25
26static struct pt_regs *get_user_regs(struct task_struct *tsk)
27{
28	return (struct pt_regs *)((unsigned long) tsk->thread_info +
29				  THREAD_SIZE - sizeof(struct pt_regs));
30}
31
32static void ptrace_single_step(struct task_struct *tsk)
33{
34	pr_debug("ptrace_single_step: pid=%u, SR=0x%08lx\n",
35		 tsk->pid, tsk->thread.cpu_context.sr);
36	if (!(tsk->thread.cpu_context.sr & SR_D)) {
37		/*
38		 * Set a breakpoint at the current pc to force the
39		 * process into debug mode.  The syscall/exception
40		 * exit code will set a breakpoint at the return
41		 * address when this flag is set.
42		 */
43		pr_debug("ptrace_single_step: Setting TIF_BREAKPOINT\n");
44		set_tsk_thread_flag(tsk, TIF_BREAKPOINT);
45	}
46
47	/* The monitor code will do the actual step for us */
48	set_tsk_thread_flag(tsk, TIF_SINGLE_STEP);
49}
50
51/*
52 * Called by kernel/ptrace.c when detaching
53 *
54 * Make sure any single step bits, etc. are not set
55 */
56void ptrace_disable(struct task_struct *child)
57{
58	clear_tsk_thread_flag(child, TIF_SINGLE_STEP);
59}
60
61/*
62 * Handle hitting a breakpoint
63 */
64static void ptrace_break(struct task_struct *tsk, struct pt_regs *regs)
65{
66	siginfo_t info;
67
68	info.si_signo = SIGTRAP;
69	info.si_errno = 0;
70	info.si_code  = TRAP_BRKPT;
71	info.si_addr  = (void __user *)instruction_pointer(regs);
72
73	pr_debug("ptrace_break: Sending SIGTRAP to PID %u (pc = 0x%p)\n",
74		 tsk->pid, info.si_addr);
75	force_sig_info(SIGTRAP, &info, tsk);
76}
77
78/*
79 * Read the word at offset "offset" into the task's "struct user". We
80 * actually access the pt_regs struct stored on the kernel stack.
81 */
82static int ptrace_read_user(struct task_struct *tsk, unsigned long offset,
83			    unsigned long __user *data)
84{
85	unsigned long *regs;
86	unsigned long value;
87
88	pr_debug("ptrace_read_user(%p, %#lx, %p)\n",
89		 tsk, offset, data);
90
91	if (offset & 3 || offset >= sizeof(struct user)) {
92		printk("ptrace_read_user: invalid offset 0x%08lx\n", offset);
93		return -EIO;
94	}
95
96	regs = (unsigned long *)get_user_regs(tsk);
97
98	value = 0;
99	if (offset < sizeof(struct pt_regs))
100		value = regs[offset / sizeof(regs[0])];
101
102	return put_user(value, data);
103}
104
105/*
106 * Write the word "value" to offset "offset" into the task's "struct
107 * user". We actually access the pt_regs struct stored on the kernel
108 * stack.
109 */
110static int ptrace_write_user(struct task_struct *tsk, unsigned long offset,
111			     unsigned long value)
112{
113	unsigned long *regs;
114
115	if (offset & 3 || offset >= sizeof(struct user)) {
116		printk("ptrace_write_user: invalid offset 0x%08lx\n", offset);
117		return -EIO;
118	}
119
120	if (offset >= sizeof(struct pt_regs))
121		return 0;
122
123	regs = (unsigned long *)get_user_regs(tsk);
124	regs[offset / sizeof(regs[0])] = value;
125
126	return 0;
127}
128
129static int ptrace_getregs(struct task_struct *tsk, void __user *uregs)
130{
131	struct pt_regs *regs = get_user_regs(tsk);
132
133	return copy_to_user(uregs, regs, sizeof(*regs)) ? -EFAULT : 0;
134}
135
136static int ptrace_setregs(struct task_struct *tsk, const void __user *uregs)
137{
138	struct pt_regs newregs;
139	int ret;
140
141	ret = -EFAULT;
142	if (copy_from_user(&newregs, uregs, sizeof(newregs)) == 0) {
143		struct pt_regs *regs = get_user_regs(tsk);
144
145		ret = -EINVAL;
146		if (valid_user_regs(&newregs)) {
147			*regs = newregs;
148			ret = 0;
149		}
150	}
151
152	return ret;
153}
154
155long arch_ptrace(struct task_struct *child, long request, long addr, long data)
156{
157	unsigned long tmp;
158	int ret;
159
160	pr_debug("arch_ptrace(%ld, %d, %#lx, %#lx)\n",
161		 request, child->pid, addr, data);
162
163	pr_debug("ptrace: Enabling monitor mode...\n");
164	__mtdr(DBGREG_DC, __mfdr(DBGREG_DC) | DC_MM | DC_DBE);
165
166	switch (request) {
167	/* Read the word at location addr in the child process */
168	case PTRACE_PEEKTEXT:
169	case PTRACE_PEEKDATA:
170		ret = access_process_vm(child, addr, &tmp, sizeof(tmp), 0);
171		if (ret == sizeof(tmp))
172			ret = put_user(tmp, (unsigned long __user *)data);
173		else
174			ret = -EIO;
175		break;
176
177	case PTRACE_PEEKUSR:
178		ret = ptrace_read_user(child, addr,
179				       (unsigned long __user *)data);
180		break;
181
182	/* Write the word in data at location addr */
183	case PTRACE_POKETEXT:
184	case PTRACE_POKEDATA:
185		ret = access_process_vm(child, addr, &data, sizeof(data), 1);
186		if (ret == sizeof(data))
187			ret = 0;
188		else
189			ret = -EIO;
190		break;
191
192	case PTRACE_POKEUSR:
193		ret = ptrace_write_user(child, addr, data);
194		break;
195
196	/* continue and stop at next (return from) syscall */
197	case PTRACE_SYSCALL:
198	/* restart after signal */
199	case PTRACE_CONT:
200		ret = -EIO;
201		if (!valid_signal(data))
202			break;
203		if (request == PTRACE_SYSCALL)
204			set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
205		else
206			clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
207		child->exit_code = data;
208		/* XXX: Are we sure no breakpoints are active here? */
209		wake_up_process(child);
210		ret = 0;
211		break;
212
213	/*
214	 * Make the child exit. Best I can do is send it a
215	 * SIGKILL. Perhaps it should be put in the status that it
216	 * wants to exit.
217	 */
218	case PTRACE_KILL:
219		ret = 0;
220		if (child->exit_state == EXIT_ZOMBIE)
221			break;
222		child->exit_code = SIGKILL;
223		wake_up_process(child);
224		break;
225
226	/*
227	 * execute single instruction.
228	 */
229	case PTRACE_SINGLESTEP:
230		ret = -EIO;
231		if (!valid_signal(data))
232			break;
233		clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
234		ptrace_single_step(child);
235		child->exit_code = data;
236		wake_up_process(child);
237		ret = 0;
238		break;
239
240	/* Detach a process that was attached */
241	case PTRACE_DETACH:
242		ret = ptrace_detach(child, data);
243		break;
244
245	case PTRACE_GETREGS:
246		ret = ptrace_getregs(child, (void __user *)data);
247		break;
248
249	case PTRACE_SETREGS:
250		ret = ptrace_setregs(child, (const void __user *)data);
251		break;
252
253	default:
254		ret = ptrace_request(child, request, addr, data);
255		break;
256	}
257
258	pr_debug("sys_ptrace returning %d (DC = 0x%08lx)\n", ret, __mfdr(DBGREG_DC));
259	return ret;
260}
261
262asmlinkage void syscall_trace(void)
263{
264	pr_debug("syscall_trace called\n");
265	if (!test_thread_flag(TIF_SYSCALL_TRACE))
266		return;
267	if (!(current->ptrace & PT_PTRACED))
268		return;
269
270	pr_debug("syscall_trace: notifying parent\n");
271	/* The 0x80 provides a way for the tracing parent to
272	 * distinguish between a syscall stop and SIGTRAP delivery */
273	ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD)
274				 ? 0x80 : 0));
275
276	/*
277	 * this isn't the same as continuing with a signal, but it
278	 * will do for normal use.  strace only continues with a
279	 * signal if the stopping signal is not SIGTRAP.  -brl
280	 */
281	if (current->exit_code) {
282		pr_debug("syscall_trace: sending signal %d to PID %u\n",
283			 current->exit_code, current->pid);
284		send_sig(current->exit_code, current, 1);
285		current->exit_code = 0;
286	}
287}
288
289asmlinkage void do_debug_priv(struct pt_regs *regs)
290{
291	unsigned long dc, ds;
292	unsigned long die_val;
293
294	ds = __mfdr(DBGREG_DS);
295
296	pr_debug("do_debug_priv: pc = %08lx, ds = %08lx\n", regs->pc, ds);
297
298	if (ds & DS_SSS)
299		die_val = DIE_SSTEP;
300	else
301		die_val = DIE_BREAKPOINT;
302
303	if (notify_die(die_val, "ptrace", regs, 0, 0, SIGTRAP) == NOTIFY_STOP)
304		return;
305
306	if (likely(ds & DS_SSS)) {
307		extern void itlb_miss(void);
308		extern void tlb_miss_common(void);
309		struct thread_info *ti;
310
311		dc = __mfdr(DBGREG_DC);
312		dc &= ~DC_SS;
313		__mtdr(DBGREG_DC, dc);
314
315		ti = current_thread_info();
316		set_ti_thread_flag(ti, TIF_BREAKPOINT);
317
318		/* The TLB miss handlers don't check thread flags */
319		if ((regs->pc >= (unsigned long)&itlb_miss)
320		    && (regs->pc <= (unsigned long)&tlb_miss_common)) {
321			__mtdr(DBGREG_BWA2A, sysreg_read(RAR_EX));
322			__mtdr(DBGREG_BWC2A, 0x40000001 | (get_asid() << 1));
323		}
324
325		/*
326		 * If we're running in supervisor mode, the breakpoint
327		 * will take us where we want directly, no need to
328		 * single step.
329		 */
330		if ((regs->sr & MODE_MASK) != MODE_SUPERVISOR)
331			set_ti_thread_flag(ti, TIF_SINGLE_STEP);
332	} else {
333		panic("Unable to handle debug trap at pc = %08lx\n",
334		      regs->pc);
335	}
336}
337
338/*
339 * Handle breakpoints, single steps and other debuggy things. To keep
340 * things simple initially, we run with interrupts and exceptions
341 * disabled all the time.
342 */
343asmlinkage void do_debug(struct pt_regs *regs)
344{
345	unsigned long dc, ds;
346
347	ds = __mfdr(DBGREG_DS);
348	pr_debug("do_debug: pc = %08lx, ds = %08lx\n", regs->pc, ds);
349
350	if (test_thread_flag(TIF_BREAKPOINT)) {
351		pr_debug("TIF_BREAKPOINT set\n");
352		/* We're taking care of it */
353		clear_thread_flag(TIF_BREAKPOINT);
354		__mtdr(DBGREG_BWC2A, 0);
355	}
356
357	if (test_thread_flag(TIF_SINGLE_STEP)) {
358		pr_debug("TIF_SINGLE_STEP set, ds = 0x%08lx\n", ds);
359		if (ds & DS_SSS) {
360			dc = __mfdr(DBGREG_DC);
361			dc &= ~DC_SS;
362			__mtdr(DBGREG_DC, dc);
363
364			clear_thread_flag(TIF_SINGLE_STEP);
365			ptrace_break(current, regs);
366		}
367	} else {
368		/* regular breakpoint */
369		ptrace_break(current, regs);
370	}
371}
372