ia64/linux-2.6.18-xen.hg

view kernel/ptrace.c @ 562:66faefe721eb

pvSCSI backend driver

Signed-off-by: Tomonari Horikoshi <t.horikoshi@jp.fujitsu.com>
Signed-off-by: Jun Kamada <kama@jp.fujitsu.com>
author Keir Fraser <keir.fraser@citrix.com>
date Mon Jun 02 09:58:27 2008 +0100 (2008-06-02)
parents 831230e53067
children
line source
1 /*
2 * linux/kernel/ptrace.c
3 *
4 * (C) Copyright 1999 Linus Torvalds
5 *
6 * Common interfaces for "ptrace()" which we do not want
7 * to continually duplicate across every architecture.
8 */
10 #include <linux/capability.h>
11 #include <linux/module.h>
12 #include <linux/sched.h>
13 #include <linux/errno.h>
14 #include <linux/mm.h>
15 #include <linux/highmem.h>
16 #include <linux/pagemap.h>
17 #include <linux/smp_lock.h>
18 #include <linux/ptrace.h>
19 #include <linux/security.h>
20 #include <linux/signal.h>
22 #include <asm/pgtable.h>
23 #include <asm/uaccess.h>
25 /*
26 * ptrace a task: make the debugger its new parent and
27 * move it to the ptrace list.
28 *
29 * Must be called with the tasklist lock write-held.
30 */
31 void __ptrace_link(struct task_struct *child, struct task_struct *new_parent)
32 {
33 BUG_ON(!list_empty(&child->ptrace_list));
34 if (child->parent == new_parent)
35 return;
36 list_add(&child->ptrace_list, &child->parent->ptrace_children);
37 remove_parent(child);
38 child->parent = new_parent;
39 add_parent(child);
40 }
42 /*
43 * Turn a tracing stop into a normal stop now, since with no tracer there
44 * would be no way to wake it up with SIGCONT or SIGKILL. If there was a
45 * signal sent that would resume the child, but didn't because it was in
46 * TASK_TRACED, resume it now.
47 * Requires that irqs be disabled.
48 */
49 void ptrace_untrace(struct task_struct *child)
50 {
51 spin_lock(&child->sighand->siglock);
52 if (child->state == TASK_TRACED) {
53 if (child->signal->flags & SIGNAL_STOP_STOPPED) {
54 child->state = TASK_STOPPED;
55 } else {
56 signal_wake_up(child, 1);
57 }
58 }
59 spin_unlock(&child->sighand->siglock);
60 }
62 /*
63 * unptrace a task: move it back to its original parent and
64 * remove it from the ptrace list.
65 *
66 * Must be called with the tasklist lock write-held.
67 */
68 void __ptrace_unlink(struct task_struct *child)
69 {
70 BUG_ON(!child->ptrace);
72 child->ptrace = 0;
73 if (!list_empty(&child->ptrace_list)) {
74 list_del_init(&child->ptrace_list);
75 remove_parent(child);
76 child->parent = child->real_parent;
77 add_parent(child);
78 }
80 if (child->state == TASK_TRACED)
81 ptrace_untrace(child);
82 }
84 /*
85 * Check that we have indeed attached to the thing..
86 */
87 int ptrace_check_attach(struct task_struct *child, int kill)
88 {
89 int ret = -ESRCH;
91 /*
92 * We take the read lock around doing both checks to close a
93 * possible race where someone else was tracing our child and
94 * detached between these two checks. After this locked check,
95 * we are sure that this is our traced child and that can only
96 * be changed by us so it's not changing right after this.
97 */
98 read_lock(&tasklist_lock);
99 if ((child->ptrace & PT_PTRACED) && child->parent == current &&
100 (!(child->ptrace & PT_ATTACHED) || child->real_parent != current)
101 && child->signal != NULL) {
102 ret = 0;
103 spin_lock_irq(&child->sighand->siglock);
104 if (child->state == TASK_STOPPED) {
105 child->state = TASK_TRACED;
106 } else if (child->state != TASK_TRACED && !kill) {
107 ret = -ESRCH;
108 }
109 spin_unlock_irq(&child->sighand->siglock);
110 }
111 read_unlock(&tasklist_lock);
113 if (!ret && !kill) {
114 wait_task_inactive(child);
115 }
117 /* All systems go.. */
118 return ret;
119 }
121 static int may_attach(struct task_struct *task)
122 {
123 /* May we inspect the given task?
124 * This check is used both for attaching with ptrace
125 * and for allowing access to sensitive information in /proc.
126 *
127 * ptrace_attach denies several cases that /proc allows
128 * because setting up the necessary parent/child relationship
129 * or halting the specified task is impossible.
130 */
131 int dumpable = 0;
132 /* Don't let security modules deny introspection */
133 if (task == current)
134 return 0;
135 if (((current->uid != task->euid) ||
136 (current->uid != task->suid) ||
137 (current->uid != task->uid) ||
138 (current->gid != task->egid) ||
139 (current->gid != task->sgid) ||
140 (current->gid != task->gid)) && !capable(CAP_SYS_PTRACE))
141 return -EPERM;
142 smp_rmb();
143 if (task->mm)
144 dumpable = task->mm->dumpable;
145 if (!dumpable && !capable(CAP_SYS_PTRACE))
146 return -EPERM;
148 return security_ptrace(current, task);
149 }
151 int ptrace_may_attach(struct task_struct *task)
152 {
153 int err;
154 task_lock(task);
155 err = may_attach(task);
156 task_unlock(task);
157 return !err;
158 }
160 int ptrace_attach(struct task_struct *task)
161 {
162 int retval;
164 retval = -EPERM;
165 if (task->pid <= 1)
166 goto out;
167 if (task->tgid == current->tgid)
168 goto out;
170 repeat:
171 /*
172 * Nasty, nasty.
173 *
174 * We want to hold both the task-lock and the
175 * tasklist_lock for writing at the same time.
176 * But that's against the rules (tasklist_lock
177 * is taken for reading by interrupts on other
178 * cpu's that may have task_lock).
179 */
180 task_lock(task);
181 local_irq_disable();
182 if (!write_trylock(&tasklist_lock)) {
183 local_irq_enable();
184 task_unlock(task);
185 do {
186 cpu_relax();
187 } while (!write_can_lock(&tasklist_lock));
188 goto repeat;
189 }
191 if (!task->mm)
192 goto bad;
193 /* the same process cannot be attached many times */
194 if (task->ptrace & PT_PTRACED)
195 goto bad;
196 retval = may_attach(task);
197 if (retval)
198 goto bad;
200 /* Go */
201 task->ptrace |= PT_PTRACED | ((task->real_parent != current)
202 ? PT_ATTACHED : 0);
203 if (capable(CAP_SYS_PTRACE))
204 task->ptrace |= PT_PTRACE_CAP;
206 __ptrace_link(task, current);
208 force_sig_specific(SIGSTOP, task);
210 bad:
211 write_unlock_irq(&tasklist_lock);
212 task_unlock(task);
213 out:
214 return retval;
215 }
217 static inline void __ptrace_detach(struct task_struct *child, unsigned int data)
218 {
219 child->exit_code = data;
220 /* .. re-parent .. */
221 __ptrace_unlink(child);
222 /* .. and wake it up. */
223 if (child->exit_state != EXIT_ZOMBIE)
224 wake_up_process(child);
225 }
227 int ptrace_detach(struct task_struct *child, unsigned int data)
228 {
229 if (!valid_signal(data))
230 return -EIO;
232 /* Architecture-specific hardware disable .. */
233 ptrace_disable(child);
235 write_lock_irq(&tasklist_lock);
236 /* protect against de_thread()->release_task() */
237 if (child->ptrace)
238 __ptrace_detach(child, data);
239 write_unlock_irq(&tasklist_lock);
241 return 0;
242 }
244 /*
245 * Access another process' address space.
246 * Source/target buffer must be kernel space,
247 * Do not walk the page table directly, use get_user_pages
248 */
250 int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
251 {
252 struct mm_struct *mm;
253 struct vm_area_struct *vma;
254 struct page *page;
255 void *old_buf = buf;
257 mm = get_task_mm(tsk);
258 if (!mm)
259 return 0;
261 down_read(&mm->mmap_sem);
262 /* ignore errors, just check how much was sucessfully transfered */
263 while (len) {
264 int bytes, ret, offset;
265 void *maddr;
267 ret = get_user_pages(tsk, mm, addr, 1,
268 write, 1, &page, &vma);
269 if (ret <= 0)
270 break;
272 bytes = len;
273 offset = addr & (PAGE_SIZE-1);
274 if (bytes > PAGE_SIZE-offset)
275 bytes = PAGE_SIZE-offset;
277 maddr = kmap(page);
278 if (write) {
279 copy_to_user_page(vma, page, addr,
280 maddr + offset, buf, bytes);
281 set_page_dirty_lock(page);
282 } else {
283 copy_from_user_page(vma, page, addr,
284 buf, maddr + offset, bytes);
285 }
286 kunmap(page);
287 page_cache_release(page);
288 len -= bytes;
289 buf += bytes;
290 addr += bytes;
291 }
292 up_read(&mm->mmap_sem);
293 mmput(mm);
295 return buf - old_buf;
296 }
298 int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
299 {
300 int copied = 0;
302 while (len > 0) {
303 char buf[128];
304 int this_len, retval;
306 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
307 retval = access_process_vm(tsk, src, buf, this_len, 0);
308 if (!retval) {
309 if (copied)
310 break;
311 return -EIO;
312 }
313 if (copy_to_user(dst, buf, retval))
314 return -EFAULT;
315 copied += retval;
316 src += retval;
317 dst += retval;
318 len -= retval;
319 }
320 return copied;
321 }
323 int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len)
324 {
325 int copied = 0;
327 while (len > 0) {
328 char buf[128];
329 int this_len, retval;
331 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
332 if (copy_from_user(buf, src, this_len))
333 return -EFAULT;
334 retval = access_process_vm(tsk, dst, buf, this_len, 1);
335 if (!retval) {
336 if (copied)
337 break;
338 return -EIO;
339 }
340 copied += retval;
341 src += retval;
342 dst += retval;
343 len -= retval;
344 }
345 return copied;
346 }
348 static int ptrace_setoptions(struct task_struct *child, long data)
349 {
350 child->ptrace &= ~PT_TRACE_MASK;
352 if (data & PTRACE_O_TRACESYSGOOD)
353 child->ptrace |= PT_TRACESYSGOOD;
355 if (data & PTRACE_O_TRACEFORK)
356 child->ptrace |= PT_TRACE_FORK;
358 if (data & PTRACE_O_TRACEVFORK)
359 child->ptrace |= PT_TRACE_VFORK;
361 if (data & PTRACE_O_TRACECLONE)
362 child->ptrace |= PT_TRACE_CLONE;
364 if (data & PTRACE_O_TRACEEXEC)
365 child->ptrace |= PT_TRACE_EXEC;
367 if (data & PTRACE_O_TRACEVFORKDONE)
368 child->ptrace |= PT_TRACE_VFORK_DONE;
370 if (data & PTRACE_O_TRACEEXIT)
371 child->ptrace |= PT_TRACE_EXIT;
373 return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
374 }
376 static int ptrace_getsiginfo(struct task_struct *child, siginfo_t __user * data)
377 {
378 siginfo_t lastinfo;
379 int error = -ESRCH;
381 read_lock(&tasklist_lock);
382 if (likely(child->sighand != NULL)) {
383 error = -EINVAL;
384 spin_lock_irq(&child->sighand->siglock);
385 if (likely(child->last_siginfo != NULL)) {
386 lastinfo = *child->last_siginfo;
387 error = 0;
388 }
389 spin_unlock_irq(&child->sighand->siglock);
390 }
391 read_unlock(&tasklist_lock);
392 if (!error)
393 return copy_siginfo_to_user(data, &lastinfo);
394 return error;
395 }
397 static int ptrace_setsiginfo(struct task_struct *child, siginfo_t __user * data)
398 {
399 siginfo_t newinfo;
400 int error = -ESRCH;
402 if (copy_from_user(&newinfo, data, sizeof (siginfo_t)))
403 return -EFAULT;
405 read_lock(&tasklist_lock);
406 if (likely(child->sighand != NULL)) {
407 error = -EINVAL;
408 spin_lock_irq(&child->sighand->siglock);
409 if (likely(child->last_siginfo != NULL)) {
410 *child->last_siginfo = newinfo;
411 error = 0;
412 }
413 spin_unlock_irq(&child->sighand->siglock);
414 }
415 read_unlock(&tasklist_lock);
416 return error;
417 }
419 int ptrace_request(struct task_struct *child, long request,
420 long addr, long data)
421 {
422 int ret = -EIO;
424 switch (request) {
425 #ifdef PTRACE_OLDSETOPTIONS
426 case PTRACE_OLDSETOPTIONS:
427 #endif
428 case PTRACE_SETOPTIONS:
429 ret = ptrace_setoptions(child, data);
430 break;
431 case PTRACE_GETEVENTMSG:
432 ret = put_user(child->ptrace_message, (unsigned long __user *) data);
433 break;
434 case PTRACE_GETSIGINFO:
435 ret = ptrace_getsiginfo(child, (siginfo_t __user *) data);
436 break;
437 case PTRACE_SETSIGINFO:
438 ret = ptrace_setsiginfo(child, (siginfo_t __user *) data);
439 break;
440 default:
441 break;
442 }
444 return ret;
445 }
447 /**
448 * ptrace_traceme -- helper for PTRACE_TRACEME
449 *
450 * Performs checks and sets PT_PTRACED.
451 * Should be used by all ptrace implementations for PTRACE_TRACEME.
452 */
453 int ptrace_traceme(void)
454 {
455 int ret = -EPERM;
457 /*
458 * Are we already being traced?
459 */
460 task_lock(current);
461 if (!(current->ptrace & PT_PTRACED)) {
462 ret = security_ptrace(current->parent, current);
463 /*
464 * Set the ptrace bit in the process ptrace flags.
465 */
466 if (!ret)
467 current->ptrace |= PT_PTRACED;
468 }
469 task_unlock(current);
470 return ret;
471 }
473 /**
474 * ptrace_get_task_struct -- grab a task struct reference for ptrace
475 * @pid: process id to grab a task_struct reference of
476 *
477 * This function is a helper for ptrace implementations. It checks
478 * permissions and then grabs a task struct for use of the actual
479 * ptrace implementation.
480 *
481 * Returns the task_struct for @pid or an ERR_PTR() on failure.
482 */
483 struct task_struct *ptrace_get_task_struct(pid_t pid)
484 {
485 struct task_struct *child;
487 /*
488 * Tracing init is not allowed.
489 */
490 if (pid == 1)
491 return ERR_PTR(-EPERM);
493 read_lock(&tasklist_lock);
494 child = find_task_by_pid(pid);
495 if (child)
496 get_task_struct(child);
497 read_unlock(&tasklist_lock);
498 if (!child)
499 return ERR_PTR(-ESRCH);
500 return child;
501 }
503 #ifndef __ARCH_SYS_PTRACE
504 asmlinkage long sys_ptrace(long request, long pid, long addr, long data)
505 {
506 struct task_struct *child;
507 long ret;
509 /*
510 * This lock_kernel fixes a subtle race with suid exec
511 */
512 lock_kernel();
513 if (request == PTRACE_TRACEME) {
514 ret = ptrace_traceme();
515 goto out;
516 }
518 child = ptrace_get_task_struct(pid);
519 if (IS_ERR(child)) {
520 ret = PTR_ERR(child);
521 goto out;
522 }
524 if (request == PTRACE_ATTACH) {
525 ret = ptrace_attach(child);
526 goto out_put_task_struct;
527 }
529 ret = ptrace_check_attach(child, request == PTRACE_KILL);
530 if (ret < 0)
531 goto out_put_task_struct;
533 ret = arch_ptrace(child, request, addr, data);
534 if (ret < 0)
535 goto out_put_task_struct;
537 out_put_task_struct:
538 put_task_struct(child);
539 out:
540 unlock_kernel();
541 return ret;
542 }
543 #endif /* __ARCH_SYS_PTRACE */