ptrace.c revision f284ce7269031947326bac6bb19a977705276222 
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/ptrace.h>
13#include <linux/errno.h>
14#include <linux/user.h>
15#include <linux/security.h>
16#include <linux/unistd.h>
17#include <linux/notifier.h>
18
19#include <asm/traps.h>
20#include <asm/uaccess.h>
21#include <asm/ocd.h>
22#include <asm/mmu_context.h>
23#include <linux/kdebug.h>
24
25static struct pt_regs *get_user_regs(struct task_struct *tsk)
26{
27	return (struct pt_regs *)((unsigned long)task_stack_page(tsk) +
28				  THREAD_SIZE - sizeof(struct pt_regs));
29}
30
31static void ptrace_single_step(struct task_struct *tsk)
32{
33	pr_debug("ptrace_single_step: pid=%u, SR=0x%08lx\n",
34		 tsk->pid, tsk->thread.cpu_context.sr);
35	if (!(tsk->thread.cpu_context.sr & SR_D)) {
36		/*
37		 * Set a breakpoint at the current pc to force the
38		 * process into debug mode.  The syscall/exception
39		 * exit code will set a breakpoint at the return
40		 * address when this flag is set.
41		 */
42		pr_debug("ptrace_single_step: Setting TIF_BREAKPOINT\n");
43		set_tsk_thread_flag(tsk, TIF_BREAKPOINT);
44	}
45
46	/* The monitor code will do the actual step for us */
47	set_tsk_thread_flag(tsk, TIF_SINGLE_STEP);
48}
49
50/*
51 * Called by kernel/ptrace.c when detaching
52 *
53 * Make sure any single step bits, etc. are not set
54 */
55void ptrace_disable(struct task_struct *child)
56{
57	clear_tsk_thread_flag(child, TIF_SINGLE_STEP);
58}
59
60/*
61 * Handle hitting a breakpoint
62 */
63static void ptrace_break(struct task_struct *tsk, struct pt_regs *regs)
64{
65	siginfo_t info;
66
67	info.si_signo = SIGTRAP;
68	info.si_errno = 0;
69	info.si_code  = TRAP_BRKPT;
70	info.si_addr  = (void __user *)instruction_pointer(regs);
71
72	pr_debug("ptrace_break: Sending SIGTRAP to PID %u (pc = 0x%p)\n",
73		 tsk->pid, info.si_addr);
74	force_sig_info(SIGTRAP, &info, tsk);
75}
76
77/*
78 * Read the word at offset "offset" into the task's "struct user". We
79 * actually access the pt_regs struct stored on the kernel stack.
80 */
81static int ptrace_read_user(struct task_struct *tsk, unsigned long offset,
82			    unsigned long __user *data)
83{
84	unsigned long *regs;
85	unsigned long value;
86
87	pr_debug("ptrace_read_user(%p, %#lx, %p)\n",
88		 tsk, offset, data);
89
90	if (offset & 3 || offset >= sizeof(struct user)) {
91		printk("ptrace_read_user: invalid offset 0x%08lx\n", offset);
92		return -EIO;
93	}
94
95	regs = (unsigned long *)get_user_regs(tsk);
96
97	value = 0;
98	if (offset < sizeof(struct pt_regs))
99		value = regs[offset / sizeof(regs[0])];
100
101	return put_user(value, data);
102}
103
104/*
105 * Write the word "value" to offset "offset" into the task's "struct
106 * user". We actually access the pt_regs struct stored on the kernel
107 * stack.
108 */
109static int ptrace_write_user(struct task_struct *tsk, unsigned long offset,
110			     unsigned long value)
111{
112	unsigned long *regs;
113
114	if (offset & 3 || offset >= sizeof(struct user)) {
115		printk("ptrace_write_user: invalid offset 0x%08lx\n", offset);
116		return -EIO;
117	}
118
119	if (offset >= sizeof(struct pt_regs))
120		return 0;
121
122	regs = (unsigned long *)get_user_regs(tsk);
123	regs[offset / sizeof(regs[0])] = value;
124
125	return 0;
126}
127
128static int ptrace_getregs(struct task_struct *tsk, void __user *uregs)
129{
130	struct pt_regs *regs = get_user_regs(tsk);
131
132	return copy_to_user(uregs, regs, sizeof(*regs)) ? -EFAULT : 0;
133}
134
135static int ptrace_setregs(struct task_struct *tsk, const void __user *uregs)
136{
137	struct pt_regs newregs;
138	int ret;
139
140	ret = -EFAULT;
141	if (copy_from_user(&newregs, uregs, sizeof(newregs)) == 0) {
142		struct pt_regs *regs = get_user_regs(tsk);
143
144		ret = -EINVAL;
145		if (valid_user_regs(&newregs)) {
146			*regs = newregs;
147			ret = 0;
148		}
149	}
150
151	return ret;
152}
153
154long arch_ptrace(struct task_struct *child, long request, long addr, long data)
155{
156	int ret;
157
158	pr_debug("arch_ptrace(%ld, %d, %#lx, %#lx)\n",
159		 request, child->pid, addr, data);
160
161	pr_debug("ptrace: Enabling monitor mode...\n");
162	__mtdr(DBGREG_DC, __mfdr(DBGREG_DC) | DC_MM | DC_DBE);
163
164	switch (request) {
165	/* Read the word at location addr in the child process */
166	case PTRACE_PEEKTEXT:
167	case PTRACE_PEEKDATA:
168		ret = generic_ptrace_peekdata(child, addr, data);
169		break;
170
171	case PTRACE_PEEKUSR:
172		ret = ptrace_read_user(child, addr,
173				       (unsigned long __user *)data);
174		break;
175
176	/* Write the word in data at location addr */
177	case PTRACE_POKETEXT:
178	case PTRACE_POKEDATA:
179		ret = generic_ptrace_pokedata(child, addr, data);
180		break;
181
182	case PTRACE_POKEUSR:
183		ret = ptrace_write_user(child, addr, data);
184		break;
185
186	/* continue and stop at next (return from) syscall */
187	case PTRACE_SYSCALL:
188	/* restart after signal */
189	case PTRACE_CONT:
190		ret = -EIO;
191		if (!valid_signal(data))
192			break;
193		if (request == PTRACE_SYSCALL)
194			set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
195		else
196			clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
197		child->exit_code = data;
198		/* XXX: Are we sure no breakpoints are active here? */
199		wake_up_process(child);
200		ret = 0;
201		break;
202
203	/*
204	 * Make the child exit. Best I can do is send it a
205	 * SIGKILL. Perhaps it should be put in the status that it
206	 * wants to exit.
207	 */
208	case PTRACE_KILL:
209		ret = 0;
210		if (child->exit_state == EXIT_ZOMBIE)
211			break;
212		child->exit_code = SIGKILL;
213		wake_up_process(child);
214		break;
215
216	/*
217	 * execute single instruction.
218	 */
219	case PTRACE_SINGLESTEP:
220		ret = -EIO;
221		if (!valid_signal(data))
222			break;
223		clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
224		ptrace_single_step(child);
225		child->exit_code = data;
226		wake_up_process(child);
227		ret = 0;
228		break;
229
230	/* Detach a process that was attached */
231	case PTRACE_DETACH:
232		ret = ptrace_detach(child, data);
233		break;
234
235	case PTRACE_GETREGS:
236		ret = ptrace_getregs(child, (void __user *)data);
237		break;
238
239	case PTRACE_SETREGS:
240		ret = ptrace_setregs(child, (const void __user *)data);
241		break;
242
243	default:
244		ret = ptrace_request(child, request, addr, data);
245		break;
246	}
247
248	pr_debug("sys_ptrace returning %d (DC = 0x%08lx)\n", ret, __mfdr(DBGREG_DC));
249	return ret;
250}
251
252asmlinkage void syscall_trace(void)
253{
254	pr_debug("syscall_trace called\n");
255	if (!test_thread_flag(TIF_SYSCALL_TRACE))
256		return;
257	if (!(current->ptrace & PT_PTRACED))
258		return;
259
260	pr_debug("syscall_trace: notifying parent\n");
261	/* The 0x80 provides a way for the tracing parent to
262	 * distinguish between a syscall stop and SIGTRAP delivery */
263	ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD)
264				 ? 0x80 : 0));
265
266	/*
267	 * this isn't the same as continuing with a signal, but it
268	 * will do for normal use.  strace only continues with a
269	 * signal if the stopping signal is not SIGTRAP.  -brl
270	 */
271	if (current->exit_code) {
272		pr_debug("syscall_trace: sending signal %d to PID %u\n",
273			 current->exit_code, current->pid);
274		send_sig(current->exit_code, current, 1);
275		current->exit_code = 0;
276	}
277}
278
279asmlinkage void do_debug_priv(struct pt_regs *regs)
280{
281	unsigned long dc, ds;
282	unsigned long die_val;
283
284	ds = __mfdr(DBGREG_DS);
285
286	pr_debug("do_debug_priv: pc = %08lx, ds = %08lx\n", regs->pc, ds);
287
288	if (ds & DS_SSS)
289		die_val = DIE_SSTEP;
290	else
291		die_val = DIE_BREAKPOINT;
292
293	if (notify_die(die_val, "ptrace", regs, 0, 0, SIGTRAP) == NOTIFY_STOP)
294		return;
295
296	if (likely(ds & DS_SSS)) {
297		extern void itlb_miss(void);
298		extern void tlb_miss_common(void);
299		struct thread_info *ti;
300
301		dc = __mfdr(DBGREG_DC);
302		dc &= ~DC_SS;
303		__mtdr(DBGREG_DC, dc);
304
305		ti = current_thread_info();
306		set_ti_thread_flag(ti, TIF_BREAKPOINT);
307
308		/* The TLB miss handlers don't check thread flags */
309		if ((regs->pc >= (unsigned long)&itlb_miss)
310		    && (regs->pc <= (unsigned long)&tlb_miss_common)) {
311			__mtdr(DBGREG_BWA2A, sysreg_read(RAR_EX));
312			__mtdr(DBGREG_BWC2A, 0x40000001 | (get_asid() << 1));
313		}
314
315		/*
316		 * If we're running in supervisor mode, the breakpoint
317		 * will take us where we want directly, no need to
318		 * single step.
319		 */
320		if ((regs->sr & MODE_MASK) != MODE_SUPERVISOR)
321			set_ti_thread_flag(ti, TIF_SINGLE_STEP);
322	} else {
323		panic("Unable to handle debug trap at pc = %08lx\n",
324		      regs->pc);
325	}
326}
327
328/*
329 * Handle breakpoints, single steps and other debuggy things. To keep
330 * things simple initially, we run with interrupts and exceptions
331 * disabled all the time.
332 */
333asmlinkage void do_debug(struct pt_regs *regs)
334{
335	unsigned long dc, ds;
336
337	ds = __mfdr(DBGREG_DS);
338	pr_debug("do_debug: pc = %08lx, ds = %08lx\n", regs->pc, ds);
339
340	if (test_thread_flag(TIF_BREAKPOINT)) {
341		pr_debug("TIF_BREAKPOINT set\n");
342		/* We're taking care of it */
343		clear_thread_flag(TIF_BREAKPOINT);
344		__mtdr(DBGREG_BWC2A, 0);
345	}
346
347	if (test_thread_flag(TIF_SINGLE_STEP)) {
348		pr_debug("TIF_SINGLE_STEP set, ds = 0x%08lx\n", ds);
349		if (ds & DS_SSS) {
350			dc = __mfdr(DBGREG_DC);
351			dc &= ~DC_SS;
352			__mtdr(DBGREG_DC, dc);
353
354			clear_thread_flag(TIF_SINGLE_STEP);
355			ptrace_break(current, regs);
356		}
357	} else {
358		/* regular breakpoint */
359		ptrace_break(current, regs);
360	}
361}
362