2 * linux/kernel/ptrace.c
4 * (C) Copyright 1999 Linus Torvalds
6 * Common interfaces for "ptrace()" which we do not want
7 * to continually duplicate across every architecture.
10 #include <linux/capability.h>
11 #include <linux/module.h>
12 #include <linux/sched.h>
13 #include <linux/errno.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>
21 #include <linux/audit.h>
22 #include <linux/pid_namespace.h>
23 #include <linux/syscalls.h>
25 #include <asm/pgtable.h>
26 #include <asm/uaccess.h>
29 * ptrace a task: make the debugger its new parent and
30 * move it to the ptrace list.
32 * Must be called with the tasklist lock write-held.
34 void __ptrace_link(struct task_struct *child, struct task_struct *new_parent)
36 BUG_ON(!list_empty(&child->ptrace_entry));
37 list_add(&child->ptrace_entry, &new_parent->ptraced);
38 child->parent = new_parent;
42 * Turn a tracing stop into a normal stop now, since with no tracer there
43 * would be no way to wake it up with SIGCONT or SIGKILL. If there was a
44 * signal sent that would resume the child, but didn't because it was in
45 * TASK_TRACED, resume it now.
46 * Requires that irqs be disabled.
48 static void ptrace_untrace(struct task_struct *child)
50 spin_lock(&child->sighand->siglock);
51 if (task_is_traced(child)) {
52 if (child->signal->flags & SIGNAL_STOP_STOPPED) {
53 __set_task_state(child, TASK_STOPPED);
55 signal_wake_up(child, 1);
58 spin_unlock(&child->sighand->siglock);
62 * unptrace a task: move it back to its original parent and
63 * remove it from the ptrace list.
65 * Must be called with the tasklist lock write-held.
67 void __ptrace_unlink(struct task_struct *child)
69 BUG_ON(!child->ptrace);
72 child->parent = child->real_parent;
73 list_del_init(&child->ptrace_entry);
75 if (task_is_traced(child))
76 ptrace_untrace(child);
80 * Check that we have indeed attached to the thing..
82 int ptrace_check_attach(struct task_struct *child, int kill)
87 * We take the read lock around doing both checks to close a
88 * possible race where someone else was tracing our child and
89 * detached between these two checks. After this locked check,
90 * we are sure that this is our traced child and that can only
91 * be changed by us so it's not changing right after this.
93 read_lock(&tasklist_lock);
94 if ((child->ptrace & PT_PTRACED) && child->parent == current) {
97 * child->sighand can't be NULL, release_task()
98 * does ptrace_unlink() before __exit_signal().
100 spin_lock_irq(&child->sighand->siglock);
101 if (task_is_stopped(child))
102 child->state = TASK_TRACED;
103 else if (!task_is_traced(child) && !kill)
105 spin_unlock_irq(&child->sighand->siglock);
107 read_unlock(&tasklist_lock);
110 ret = wait_task_inactive(child, TASK_TRACED) ? 0 : -ESRCH;
112 /* All systems go.. */
116 int __ptrace_may_access(struct task_struct *task, unsigned int mode)
118 const struct cred *cred = current_cred(), *tcred;
120 /* May we inspect the given task?
121 * This check is used both for attaching with ptrace
122 * and for allowing access to sensitive information in /proc.
124 * ptrace_attach denies several cases that /proc allows
125 * because setting up the necessary parent/child relationship
126 * or halting the specified task is impossible.
129 /* Don't let security modules deny introspection */
133 tcred = __task_cred(task);
134 if ((cred->uid != tcred->euid ||
135 cred->uid != tcred->suid ||
136 cred->uid != tcred->uid ||
137 cred->gid != tcred->egid ||
138 cred->gid != tcred->sgid ||
139 cred->gid != tcred->gid) &&
140 !capable(CAP_SYS_PTRACE)) {
147 dumpable = get_dumpable(task->mm);
148 if (!dumpable && !capable(CAP_SYS_PTRACE))
151 return security_ptrace_may_access(task, mode);
154 bool ptrace_may_access(struct task_struct *task, unsigned int mode)
158 err = __ptrace_may_access(task, mode);
160 return (!err ? true : false);
163 int ptrace_attach(struct task_struct *task)
171 if (same_thread_group(task, current))
178 * We want to hold both the task-lock and the
179 * tasklist_lock for writing at the same time.
180 * But that's against the rules (tasklist_lock
181 * is taken for reading by interrupts on other
182 * cpu's that may have task_lock).
185 if (!write_trylock_irqsave(&tasklist_lock, flags)) {
189 } while (!write_can_lock(&tasklist_lock));
195 /* the same process cannot be attached many times */
196 if (task->ptrace & PT_PTRACED)
198 retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH);
203 task->ptrace |= PT_PTRACED;
204 if (capable(CAP_SYS_PTRACE))
205 task->ptrace |= PT_PTRACE_CAP;
207 __ptrace_link(task, current);
209 send_sig_info(SIGSTOP, SEND_SIG_FORCED, task);
211 write_unlock_irqrestore(&tasklist_lock, flags);
217 static inline void __ptrace_detach(struct task_struct *child, unsigned int data)
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);
227 int ptrace_detach(struct task_struct *child, unsigned int data)
229 if (!valid_signal(data))
232 /* Architecture-specific hardware disable .. */
233 ptrace_disable(child);
234 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
236 write_lock_irq(&tasklist_lock);
237 /* protect against de_thread()->release_task() */
239 __ptrace_detach(child, data);
240 write_unlock_irq(&tasklist_lock);
245 int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
251 int this_len, retval;
253 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
254 retval = access_process_vm(tsk, src, buf, this_len, 0);
260 if (copy_to_user(dst, buf, retval))
270 int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len)
276 int this_len, retval;
278 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
279 if (copy_from_user(buf, src, this_len))
281 retval = access_process_vm(tsk, dst, buf, this_len, 1);
295 static int ptrace_setoptions(struct task_struct *child, long data)
297 child->ptrace &= ~PT_TRACE_MASK;
299 if (data & PTRACE_O_TRACESYSGOOD)
300 child->ptrace |= PT_TRACESYSGOOD;
302 if (data & PTRACE_O_TRACEFORK)
303 child->ptrace |= PT_TRACE_FORK;
305 if (data & PTRACE_O_TRACEVFORK)
306 child->ptrace |= PT_TRACE_VFORK;
308 if (data & PTRACE_O_TRACECLONE)
309 child->ptrace |= PT_TRACE_CLONE;
311 if (data & PTRACE_O_TRACEEXEC)
312 child->ptrace |= PT_TRACE_EXEC;
314 if (data & PTRACE_O_TRACEVFORKDONE)
315 child->ptrace |= PT_TRACE_VFORK_DONE;
317 if (data & PTRACE_O_TRACEEXIT)
318 child->ptrace |= PT_TRACE_EXIT;
320 return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
323 static int ptrace_getsiginfo(struct task_struct *child, siginfo_t *info)
327 read_lock(&tasklist_lock);
328 if (likely(child->sighand != NULL)) {
330 spin_lock_irq(&child->sighand->siglock);
331 if (likely(child->last_siginfo != NULL)) {
332 *info = *child->last_siginfo;
335 spin_unlock_irq(&child->sighand->siglock);
337 read_unlock(&tasklist_lock);
341 static int ptrace_setsiginfo(struct task_struct *child, const siginfo_t *info)
345 read_lock(&tasklist_lock);
346 if (likely(child->sighand != NULL)) {
348 spin_lock_irq(&child->sighand->siglock);
349 if (likely(child->last_siginfo != NULL)) {
350 *child->last_siginfo = *info;
353 spin_unlock_irq(&child->sighand->siglock);
355 read_unlock(&tasklist_lock);
360 #ifdef PTRACE_SINGLESTEP
361 #define is_singlestep(request) ((request) == PTRACE_SINGLESTEP)
363 #define is_singlestep(request) 0
366 #ifdef PTRACE_SINGLEBLOCK
367 #define is_singleblock(request) ((request) == PTRACE_SINGLEBLOCK)
369 #define is_singleblock(request) 0
373 #define is_sysemu_singlestep(request) ((request) == PTRACE_SYSEMU_SINGLESTEP)
375 #define is_sysemu_singlestep(request) 0
378 static int ptrace_resume(struct task_struct *child, long request, long data)
380 if (!valid_signal(data))
383 if (request == PTRACE_SYSCALL)
384 set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
386 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
388 #ifdef TIF_SYSCALL_EMU
389 if (request == PTRACE_SYSEMU || request == PTRACE_SYSEMU_SINGLESTEP)
390 set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
392 clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
395 if (is_singleblock(request)) {
396 if (unlikely(!arch_has_block_step()))
398 user_enable_block_step(child);
399 } else if (is_singlestep(request) || is_sysemu_singlestep(request)) {
400 if (unlikely(!arch_has_single_step()))
402 user_enable_single_step(child);
405 user_disable_single_step(child);
407 child->exit_code = data;
408 wake_up_process(child);
413 int ptrace_request(struct task_struct *child, long request,
414 long addr, long data)
420 case PTRACE_PEEKTEXT:
421 case PTRACE_PEEKDATA:
422 return generic_ptrace_peekdata(child, addr, data);
423 case PTRACE_POKETEXT:
424 case PTRACE_POKEDATA:
425 return generic_ptrace_pokedata(child, addr, data);
427 #ifdef PTRACE_OLDSETOPTIONS
428 case PTRACE_OLDSETOPTIONS:
430 case PTRACE_SETOPTIONS:
431 ret = ptrace_setoptions(child, data);
433 case PTRACE_GETEVENTMSG:
434 ret = put_user(child->ptrace_message, (unsigned long __user *) data);
437 case PTRACE_GETSIGINFO:
438 ret = ptrace_getsiginfo(child, &siginfo);
440 ret = copy_siginfo_to_user((siginfo_t __user *) data,
444 case PTRACE_SETSIGINFO:
445 if (copy_from_user(&siginfo, (siginfo_t __user *) data,
449 ret = ptrace_setsiginfo(child, &siginfo);
452 case PTRACE_DETACH: /* detach a process that was attached. */
453 ret = ptrace_detach(child, data);
456 #ifdef PTRACE_SINGLESTEP
457 case PTRACE_SINGLESTEP:
459 #ifdef PTRACE_SINGLEBLOCK
460 case PTRACE_SINGLEBLOCK:
464 case PTRACE_SYSEMU_SINGLESTEP:
468 return ptrace_resume(child, request, data);
471 if (child->exit_state) /* already dead */
473 return ptrace_resume(child, request, SIGKILL);
483 * ptrace_traceme -- helper for PTRACE_TRACEME
485 * Performs checks and sets PT_PTRACED.
486 * Should be used by all ptrace implementations for PTRACE_TRACEME.
488 int ptrace_traceme(void)
493 * Are we already being traced?
497 if (!(current->ptrace & PT_PTRACED)) {
499 * See ptrace_attach() comments about the locking here.
502 if (!write_trylock_irqsave(&tasklist_lock, flags)) {
503 task_unlock(current);
506 } while (!write_can_lock(&tasklist_lock));
510 ret = security_ptrace_traceme(current->parent);
513 * Set the ptrace bit in the process ptrace flags.
514 * Then link us on our parent's ptraced list.
517 current->ptrace |= PT_PTRACED;
518 __ptrace_link(current, current->real_parent);
521 write_unlock_irqrestore(&tasklist_lock, flags);
523 task_unlock(current);
528 * ptrace_get_task_struct -- grab a task struct reference for ptrace
529 * @pid: process id to grab a task_struct reference of
531 * This function is a helper for ptrace implementations. It checks
532 * permissions and then grabs a task struct for use of the actual
533 * ptrace implementation.
535 * Returns the task_struct for @pid or an ERR_PTR() on failure.
537 struct task_struct *ptrace_get_task_struct(pid_t pid)
539 struct task_struct *child;
541 read_lock(&tasklist_lock);
542 child = find_task_by_vpid(pid);
544 get_task_struct(child);
546 read_unlock(&tasklist_lock);
548 return ERR_PTR(-ESRCH);
552 #ifndef arch_ptrace_attach
553 #define arch_ptrace_attach(child) do { } while (0)
556 asmlinkage long sys_ptrace(long request, long pid, long addr, long data)
558 struct task_struct *child;
562 * This lock_kernel fixes a subtle race with suid exec
565 if (request == PTRACE_TRACEME) {
566 ret = ptrace_traceme();
568 arch_ptrace_attach(current);
572 child = ptrace_get_task_struct(pid);
574 ret = PTR_ERR(child);
578 if (request == PTRACE_ATTACH) {
579 ret = ptrace_attach(child);
581 * Some architectures need to do book-keeping after
585 arch_ptrace_attach(child);
586 goto out_put_task_struct;
589 ret = ptrace_check_attach(child, request == PTRACE_KILL);
591 goto out_put_task_struct;
593 ret = arch_ptrace(child, request, addr, data);
595 goto out_put_task_struct;
598 put_task_struct(child);
604 int generic_ptrace_peekdata(struct task_struct *tsk, long addr, long data)
609 copied = access_process_vm(tsk, addr, &tmp, sizeof(tmp), 0);
610 if (copied != sizeof(tmp))
612 return put_user(tmp, (unsigned long __user *)data);
615 int generic_ptrace_pokedata(struct task_struct *tsk, long addr, long data)
619 copied = access_process_vm(tsk, addr, &data, sizeof(data), 1);
620 return (copied == sizeof(data)) ? 0 : -EIO;
623 #if defined CONFIG_COMPAT && defined __ARCH_WANT_COMPAT_SYS_PTRACE
624 #include <linux/compat.h>
626 int compat_ptrace_request(struct task_struct *child, compat_long_t request,
627 compat_ulong_t addr, compat_ulong_t data)
629 compat_ulong_t __user *datap = compat_ptr(data);
635 case PTRACE_PEEKTEXT:
636 case PTRACE_PEEKDATA:
637 ret = access_process_vm(child, addr, &word, sizeof(word), 0);
638 if (ret != sizeof(word))
641 ret = put_user(word, datap);
644 case PTRACE_POKETEXT:
645 case PTRACE_POKEDATA:
646 ret = access_process_vm(child, addr, &data, sizeof(data), 1);
647 ret = (ret != sizeof(data) ? -EIO : 0);
650 case PTRACE_GETEVENTMSG:
651 ret = put_user((compat_ulong_t) child->ptrace_message, datap);
654 case PTRACE_GETSIGINFO:
655 ret = ptrace_getsiginfo(child, &siginfo);
657 ret = copy_siginfo_to_user32(
658 (struct compat_siginfo __user *) datap,
662 case PTRACE_SETSIGINFO:
663 memset(&siginfo, 0, sizeof siginfo);
664 if (copy_siginfo_from_user32(
665 &siginfo, (struct compat_siginfo __user *) datap))
668 ret = ptrace_setsiginfo(child, &siginfo);
672 ret = ptrace_request(child, request, addr, data);
678 asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
679 compat_long_t addr, compat_long_t data)
681 struct task_struct *child;
685 * This lock_kernel fixes a subtle race with suid exec
688 if (request == PTRACE_TRACEME) {
689 ret = ptrace_traceme();
693 child = ptrace_get_task_struct(pid);
695 ret = PTR_ERR(child);
699 if (request == PTRACE_ATTACH) {
700 ret = ptrace_attach(child);
702 * Some architectures need to do book-keeping after
706 arch_ptrace_attach(child);
707 goto out_put_task_struct;
710 ret = ptrace_check_attach(child, request == PTRACE_KILL);
712 ret = compat_arch_ptrace(child, request, addr, data);
715 put_task_struct(child);
720 #endif /* CONFIG_COMPAT && __ARCH_WANT_COMPAT_SYS_PTRACE */