aboutsummaryrefslogtreecommitdiffstats
path: root/kernel/ptrace.c
blob: f5cc1cec0fb4ab33cf62028c7cf9200c08343a81 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
/*
 * linux/kernel/ptrace.c
 *
 * (C) Copyright 1999 Linus Torvalds
 *
 * Common interfaces for "ptrace()" which we do not want
 * to continually duplicate across every architecture.
 */

#include <linux/module.h>
#include <linux/sched.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/highmem.h>
#include <linux/pagemap.h>
#include <linux/smp_lock.h>
#include <linux/ptrace.h>
#include <linux/security.h>

#include <asm/pgtable.h>
#include <asm/uaccess.h>

/*
 * ptrace a task: make the debugger its new parent and
 * move it to the ptrace list.
 *
 * Must be called with the tasklist lock write-held.
 */
void __ptrace_link(task_t *child, task_t *new_parent)
{
	if (!list_empty(&child->ptrace_list))
		BUG();
	if (child->parent == new_parent)
		return;
	list_add(&child->ptrace_list, &child->parent->ptrace_children);
	REMOVE_LINKS(child);
	child->parent = new_parent;
	SET_LINKS(child);
}
 
/*
 * Turn a tracing stop into a normal stop now, since with no tracer there
 * would be no way to wake it up with SIGCONT or SIGKILL.  If there was a
 * signal sent that would resume the child, but didn't because it was in
 * TASK_TRACED, resume it now.
 * Requires that irqs be disabled.
 */
void ptrace_untrace(task_t *child)
{
	spin_lock(&child->sighand->siglock);
	if (child->state == TASK_TRACED) {
		if (child->signal->flags & SIGNAL_STOP_STOPPED) {
			child->state = TASK_STOPPED;
		} else {
			signal_wake_up(child, 1);
		}
	}
	spin_unlock(&child->sighand->siglock);
}

/*
 * unptrace a task: move it back to its original parent and
 * remove it from the ptrace list.
 *
 * Must be called with the tasklist lock write-held.
 */
void __ptrace_unlink(task_t *child)
{
	if (!child->ptrace)
		BUG();
	child->ptrace = 0;
	if (!list_empty(&child->ptrace_list)) {
		list_del_init(&child->ptrace_list);
		REMOVE_LINKS(child);
		child->parent = child->real_parent;
		SET_LINKS(child);
	}

	if (child->state == TASK_TRACED)
		ptrace_untrace(child);
}

/*
 * Check that we have indeed attached to the thing..
 */
int ptrace_check_attach(struct task_struct *child, int kill)
{
	int ret = -ESRCH;

	/*
	 * We take the read lock around doing both checks to close a
	 * possible race where someone else was tracing our child and
	 * detached between these two checks.  After this locked check,
	 * we are sure that this is our traced child and that can only
	 * be changed by us so it's not changing right after this.
	 */
	read_lock(&tasklist_lock);
	if ((child->ptrace & PT_PTRACED) && child->parent == current &&
	    (!(child->ptrace & PT_ATTACHED) || child->real_parent != current)
	    && child->signal != NULL) {
		ret = 0;
		spin_lock_irq(&child->sighand->siglock);
		if (child->state == TASK_STOPPED) {
			child->state = TASK_TRACED;
		} else if (child->state != TASK_TRACED && !kill) {
			ret = -ESRCH;
		}
		spin_unlock_irq(&child->sighand->siglock);
	}
	read_unlock(&tasklist_lock);

	if (!ret && !kill) {
		wait_task_inactive(child);
	}

	/* All systems go.. */
	return ret;
}

int ptrace_attach(struct task_struct *task)
{
	int retval;
	task_lock(task);
	retval = -EPERM;
	if (task->pid <= 1)
		goto bad;
	if (task == current)
		goto bad;
	if (!task->mm)
		goto bad;
	if(((current->uid != task->euid) ||
	    (current->uid != task->suid) ||
	    (current->uid != task->uid) ||
 	    (current->gid != task->egid) ||
 	    (current->gid != task->sgid) ||
 	    (current->gid != task->gid)) && !capable(CAP_SYS_PTRACE))
		goto bad;
	smp_rmb();
	if (!task->mm->dumpable && !capable(CAP_SYS_PTRACE))
		goto bad;
	/* the same process cannot be attached many times */
	if (task->ptrace & PT_PTRACED)
		goto bad;
	retval = security_ptrace(current, task);
	if (retval)
		goto bad;

	/* Go */
	task->ptrace |= PT_PTRACED | ((task->real_parent != current)
				      ? PT_ATTACHED : 0);
	if (capable(CAP_SYS_PTRACE))
		task->ptrace |= PT_PTRACE_CAP;
	task_unlock(task);

	write_lock_irq(&tasklist_lock);
	__ptrace_link(task, current);
	write_unlock_irq(&tasklist_lock);

	force_sig_specific(SIGSTOP, task);
	return 0;

bad:
	task_unlock(task);
	return retval;
}

int ptrace_detach(struct task_struct *child, unsigned int data)
{
	if ((unsigned long) data > _NSIG)
		return	-EIO;

	/* Architecture-specific hardware disable .. */
	ptrace_disable(child);

	/* .. re-parent .. */
	child->exit_code = data;

	write_lock_irq(&tasklist_lock);
	__ptrace_unlink(child);
	/* .. and wake it up. */
	if (child->exit_state != EXIT_ZOMBIE)
		wake_up_process(child);
	write_unlock_irq(&tasklist_lock);

	return 0;
}

/*
 * Access another process' address space.
 * Source/target buffer must be kernel space, 
 * Do not walk the page table directly, use get_user_pages
 */

int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
{
	struct mm_struct *mm;
	struct vm_area_struct *vma;
	struct page *page;
	void *old_buf = buf;

	mm = get_task_mm(tsk);
	if (!mm)
		return 0;

	down_read(&mm->mmap_sem);
	/* ignore errors, just check how much was sucessfully transfered */
	while (len) {
		int bytes, ret, offset;
		void *maddr;

		ret = get_user_pages(tsk, mm, addr, 1,
				write, 1, &page, &vma);
		if (ret <= 0)
			break;

		bytes = len;
		offset = addr & (PAGE_SIZE-1);
		if (bytes > PAGE_SIZE-offset)
			bytes = PAGE_SIZE-offset;

		maddr = kmap(page);
		if (write) {
			copy_to_user_page(vma, page, addr,
					  maddr + offset, buf, bytes);
			set_page_dirty_lock(page);
		} else {
			copy_from_user_page(vma, page, addr,
					    buf, maddr + offset, bytes);
		}
		kunmap(page);
		page_cache_release(page);
		len -= bytes;
		buf += bytes;
		addr += bytes;
	}
	up_read(&mm->mmap_sem);
	mmput(mm);
	
	return buf - old_buf;
}

int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
{
	int copied = 0;

	while (len > 0) {
		char buf[128];
		int this_len, retval;

		this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
		retval = access_process_vm(tsk, src, buf, this_len, 0);
		if (!retval) {
			if (copied)
				break;
			return -EIO;
		}
		if (copy_to_user(dst, buf, retval))
			return -EFAULT;
		copied += retval;
		src += retval;
		dst += retval;
		len -= retval;			
	}
	return copied;
}

int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len)
{
	int copied = 0;

	while (len > 0) {
		char buf[128];
		int this_len, retval;

		this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
		if (copy_from_user(buf, src, this_len))
			return -EFAULT;
		retval = access_process_vm(tsk, dst, buf, this_len, 1);
		if (!retval) {
			if (copied)
				break;
			return -EIO;
		}
		copied += retval;
		src += retval;
		dst += retval;
		len -= retval;			
	}
	return copied;
}

static int ptrace_setoptions(struct task_struct *child, long data)
{
	child->ptrace &= ~PT_TRACE_MASK;

	if (data & PTRACE_O_TRACESYSGOOD)
		child->ptrace |= PT_TRACESYSGOOD;

	if (data & PTRACE_O_TRACEFORK)
		child->ptrace |= PT_TRACE_FORK;

	if (data & PTRACE_O_TRACEVFORK)
		child->ptrace |= PT_TRACE_VFORK;

	if (data & PTRACE_O_TRACECLONE)
		child->ptrace |= PT_TRACE_CLONE;

	if (data & PTRACE_O_TRACEEXEC)
		child->ptrace |= PT_TRACE_EXEC;

	if (data & PTRACE_O_TRACEVFORKDONE)
		child->ptrace |= PT_TRACE_VFORK_DONE;

	if (data & PTRACE_O_TRACEEXIT)
		child->ptrace |= PT_TRACE_EXIT;

	return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
}

static int ptrace_getsiginfo(struct task_struct *child, siginfo_t __user * data)
{
	siginfo_t lastinfo;
	int error = -ESRCH;

	read_lock(&tasklist_lock);
	if (likely(child->sighand != NULL)) {
		error = -EINVAL;
		spin_lock_irq(&child->sighand->siglock);
		if (likely(child->last_siginfo != NULL)) {
			lastinfo = *child->last_siginfo;
			error = 0;
		}
		spin_unlock_irq(&child->sighand->siglock);
	}
	read_unlock(&tasklist_lock);
	if (!error)
		return copy_siginfo_to_user(data, &lastinfo);
	return error;
}

static int ptrace_setsiginfo(struct task_struct *child, siginfo_t __user * data)
{
	siginfo_t newinfo;
	int error = -ESRCH;

	if (copy_from_user(&newinfo, data, sizeof (siginfo_t)))
		return -EFAULT;

	read_lock(&tasklist_lock);
	if (likely(child->sighand != NULL)) {
		error = -EINVAL;
		spin_lock_irq(&child->sighand->siglock);
		if (likely(child->last_siginfo != NULL)) {
			*child->last_siginfo = newinfo;
			error = 0;
		}
		spin_unlock_irq(&child->sighand->siglock);
	}
	read_unlock(&tasklist_lock);
	return error;
}

int ptrace_request(struct task_struct *child, long request,
		   long addr, long data)
{
	int ret = -EIO;

	switch (request) {
#ifdef PTRACE_OLDSETOPTIONS
	case PTRACE_OLDSETOPTIONS:
#endif
	case PTRACE_SETOPTIONS:
		ret = ptrace_setoptions(child, data);
		break;
	case PTRACE_GETEVENTMSG:
		ret = put_user(child->ptrace_message, (unsigned long __user *) data);
		break;
	case PTRACE_GETSIGINFO:
		ret = ptrace_getsiginfo(child, (siginfo_t __user *) data);
		break;
	case PTRACE_SETSIGINFO:
		ret = ptrace_setsiginfo(child, (siginfo_t __user *) data);
		break;
	default:
		break;
	}

	return ret;
}