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>
30 * Initialize a new task whose father had been ptraced.
32 * Called from copy_process().
34 void ptrace_fork(struct task_struct *child, unsigned long clone_flags)
36 arch_ptrace_fork(child, clone_flags);
40 * ptrace a task: make the debugger its new parent and
41 * move it to the ptrace list.
43 * Must be called with the tasklist lock write-held.
45 void __ptrace_link(struct task_struct *child, struct task_struct *new_parent)
47 BUG_ON(!list_empty(&child->ptrace_entry));
48 list_add(&child->ptrace_entry, &new_parent->ptraced);
49 child->parent = new_parent;
53 * Turn a tracing stop into a normal stop now, since with no tracer there
54 * would be no way to wake it up with SIGCONT or SIGKILL. If there was a
55 * signal sent that would resume the child, but didn't because it was in
56 * TASK_TRACED, resume it now.
57 * Requires that irqs be disabled.
59 static void ptrace_untrace(struct task_struct *child)
61 spin_lock(&child->sighand->siglock);
62 if (task_is_traced(child)) {
63 if (child->signal->flags & SIGNAL_STOP_STOPPED) {
64 __set_task_state(child, TASK_STOPPED);
66 signal_wake_up(child, 1);
69 spin_unlock(&child->sighand->siglock);
73 * unptrace a task: move it back to its original parent and
74 * remove it from the ptrace list.
76 * Must be called with the tasklist lock write-held.
78 void __ptrace_unlink(struct task_struct *child)
80 BUG_ON(!child->ptrace);
83 child->parent = child->real_parent;
84 list_del_init(&child->ptrace_entry);
86 arch_ptrace_untrace(child);
87 if (task_is_traced(child))
88 ptrace_untrace(child);
92 * Check that we have indeed attached to the thing..
94 int ptrace_check_attach(struct task_struct *child, int kill)
99 * We take the read lock around doing both checks to close a
100 * possible race where someone else was tracing our child and
101 * detached between these two checks. After this locked check,
102 * we are sure that this is our traced child and that can only
103 * be changed by us so it's not changing right after this.
105 read_lock(&tasklist_lock);
106 if ((child->ptrace & PT_PTRACED) && child->parent == current) {
109 * child->sighand can't be NULL, release_task()
110 * does ptrace_unlink() before __exit_signal().
112 spin_lock_irq(&child->sighand->siglock);
113 if (task_is_stopped(child))
114 child->state = TASK_TRACED;
115 else if (!task_is_traced(child) && !kill)
117 spin_unlock_irq(&child->sighand->siglock);
119 read_unlock(&tasklist_lock);
122 ret = wait_task_inactive(child, TASK_TRACED) ? 0 : -ESRCH;
124 /* All systems go.. */
128 int __ptrace_may_access(struct task_struct *task, unsigned int mode)
130 const struct cred *cred = current_cred(), *tcred;
132 /* May we inspect the given task?
133 * This check is used both for attaching with ptrace
134 * and for allowing access to sensitive information in /proc.
136 * ptrace_attach denies several cases that /proc allows
137 * because setting up the necessary parent/child relationship
138 * or halting the specified task is impossible.
141 /* Don't let security modules deny introspection */
145 tcred = __task_cred(task);
146 if ((cred->uid != tcred->euid ||
147 cred->uid != tcred->suid ||
148 cred->uid != tcred->uid ||
149 cred->gid != tcred->egid ||
150 cred->gid != tcred->sgid ||
151 cred->gid != tcred->gid) &&
152 !capable(CAP_SYS_PTRACE)) {
159 dumpable = get_dumpable(task->mm);
160 if (!dumpable && !capable(CAP_SYS_PTRACE))
163 return security_ptrace_may_access(task, mode);
166 bool ptrace_may_access(struct task_struct *task, unsigned int mode)
170 err = __ptrace_may_access(task, mode);
172 return (!err ? true : false);
175 int ptrace_attach(struct task_struct *task)
183 if (same_thread_group(task, current))
186 /* Protect exec's credential calculations against our interference;
187 * SUID, SGID and LSM creds get determined differently under ptrace.
189 retval = mutex_lock_interruptible(¤t->cred_exec_mutex);
198 * We want to hold both the task-lock and the
199 * tasklist_lock for writing at the same time.
200 * But that's against the rules (tasklist_lock
201 * is taken for reading by interrupts on other
202 * cpu's that may have task_lock).
205 if (!write_trylock_irqsave(&tasklist_lock, flags)) {
209 } while (!write_can_lock(&tasklist_lock));
215 /* the same process cannot be attached many times */
216 if (task->ptrace & PT_PTRACED)
218 retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH);
223 task->ptrace |= PT_PTRACED;
224 if (capable(CAP_SYS_PTRACE))
225 task->ptrace |= PT_PTRACE_CAP;
227 __ptrace_link(task, current);
229 send_sig_info(SIGSTOP, SEND_SIG_FORCED, task);
231 write_unlock_irqrestore(&tasklist_lock, flags);
233 mutex_unlock(¤t->cred_exec_mutex);
238 int ptrace_detach(struct task_struct *child, unsigned int data)
240 if (!valid_signal(data))
243 /* Architecture-specific hardware disable .. */
244 ptrace_disable(child);
245 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
247 /* protect against de_thread()->release_task() */
248 write_lock_irq(&tasklist_lock);
250 child->exit_code = data;
252 __ptrace_unlink(child);
254 if (!child->exit_state)
255 wake_up_process(child);
257 write_unlock_irq(&tasklist_lock);
262 int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
268 int this_len, retval;
270 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
271 retval = access_process_vm(tsk, src, buf, this_len, 0);
277 if (copy_to_user(dst, buf, retval))
287 int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len)
293 int this_len, retval;
295 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
296 if (copy_from_user(buf, src, this_len))
298 retval = access_process_vm(tsk, dst, buf, this_len, 1);
312 static int ptrace_setoptions(struct task_struct *child, long data)
314 child->ptrace &= ~PT_TRACE_MASK;
316 if (data & PTRACE_O_TRACESYSGOOD)
317 child->ptrace |= PT_TRACESYSGOOD;
319 if (data & PTRACE_O_TRACEFORK)
320 child->ptrace |= PT_TRACE_FORK;
322 if (data & PTRACE_O_TRACEVFORK)
323 child->ptrace |= PT_TRACE_VFORK;
325 if (data & PTRACE_O_TRACECLONE)
326 child->ptrace |= PT_TRACE_CLONE;
328 if (data & PTRACE_O_TRACEEXEC)
329 child->ptrace |= PT_TRACE_EXEC;
331 if (data & PTRACE_O_TRACEVFORKDONE)
332 child->ptrace |= PT_TRACE_VFORK_DONE;
334 if (data & PTRACE_O_TRACEEXIT)
335 child->ptrace |= PT_TRACE_EXIT;
337 return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
340 static int ptrace_getsiginfo(struct task_struct *child, siginfo_t *info)
344 read_lock(&tasklist_lock);
345 if (likely(child->sighand != NULL)) {
347 spin_lock_irq(&child->sighand->siglock);
348 if (likely(child->last_siginfo != NULL)) {
349 *info = *child->last_siginfo;
352 spin_unlock_irq(&child->sighand->siglock);
354 read_unlock(&tasklist_lock);
358 static int ptrace_setsiginfo(struct task_struct *child, const siginfo_t *info)
362 read_lock(&tasklist_lock);
363 if (likely(child->sighand != NULL)) {
365 spin_lock_irq(&child->sighand->siglock);
366 if (likely(child->last_siginfo != NULL)) {
367 *child->last_siginfo = *info;
370 spin_unlock_irq(&child->sighand->siglock);
372 read_unlock(&tasklist_lock);
377 #ifdef PTRACE_SINGLESTEP
378 #define is_singlestep(request) ((request) == PTRACE_SINGLESTEP)
380 #define is_singlestep(request) 0
383 #ifdef PTRACE_SINGLEBLOCK
384 #define is_singleblock(request) ((request) == PTRACE_SINGLEBLOCK)
386 #define is_singleblock(request) 0
390 #define is_sysemu_singlestep(request) ((request) == PTRACE_SYSEMU_SINGLESTEP)
392 #define is_sysemu_singlestep(request) 0
395 static int ptrace_resume(struct task_struct *child, long request, long data)
397 if (!valid_signal(data))
400 if (request == PTRACE_SYSCALL)
401 set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
403 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
405 #ifdef TIF_SYSCALL_EMU
406 if (request == PTRACE_SYSEMU || request == PTRACE_SYSEMU_SINGLESTEP)
407 set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
409 clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
412 if (is_singleblock(request)) {
413 if (unlikely(!arch_has_block_step()))
415 user_enable_block_step(child);
416 } else if (is_singlestep(request) || is_sysemu_singlestep(request)) {
417 if (unlikely(!arch_has_single_step()))
419 user_enable_single_step(child);
422 user_disable_single_step(child);
424 child->exit_code = data;
425 wake_up_process(child);
430 int ptrace_request(struct task_struct *child, long request,
431 long addr, long data)
437 case PTRACE_PEEKTEXT:
438 case PTRACE_PEEKDATA:
439 return generic_ptrace_peekdata(child, addr, data);
440 case PTRACE_POKETEXT:
441 case PTRACE_POKEDATA:
442 return generic_ptrace_pokedata(child, addr, data);
444 #ifdef PTRACE_OLDSETOPTIONS
445 case PTRACE_OLDSETOPTIONS:
447 case PTRACE_SETOPTIONS:
448 ret = ptrace_setoptions(child, data);
450 case PTRACE_GETEVENTMSG:
451 ret = put_user(child->ptrace_message, (unsigned long __user *) data);
454 case PTRACE_GETSIGINFO:
455 ret = ptrace_getsiginfo(child, &siginfo);
457 ret = copy_siginfo_to_user((siginfo_t __user *) data,
461 case PTRACE_SETSIGINFO:
462 if (copy_from_user(&siginfo, (siginfo_t __user *) data,
466 ret = ptrace_setsiginfo(child, &siginfo);
469 case PTRACE_DETACH: /* detach a process that was attached. */
470 ret = ptrace_detach(child, data);
473 #ifdef PTRACE_SINGLESTEP
474 case PTRACE_SINGLESTEP:
476 #ifdef PTRACE_SINGLEBLOCK
477 case PTRACE_SINGLEBLOCK:
481 case PTRACE_SYSEMU_SINGLESTEP:
485 return ptrace_resume(child, request, data);
488 if (child->exit_state) /* already dead */
490 return ptrace_resume(child, request, SIGKILL);
500 * ptrace_traceme -- helper for PTRACE_TRACEME
502 * Performs checks and sets PT_PTRACED.
503 * Should be used by all ptrace implementations for PTRACE_TRACEME.
505 int ptrace_traceme(void)
510 * Are we already being traced?
514 if (!(current->ptrace & PT_PTRACED)) {
516 * See ptrace_attach() comments about the locking here.
519 if (!write_trylock_irqsave(&tasklist_lock, flags)) {
520 task_unlock(current);
523 } while (!write_can_lock(&tasklist_lock));
527 ret = security_ptrace_traceme(current->parent);
530 * Set the ptrace bit in the process ptrace flags.
531 * Then link us on our parent's ptraced list.
534 current->ptrace |= PT_PTRACED;
535 __ptrace_link(current, current->real_parent);
538 write_unlock_irqrestore(&tasklist_lock, flags);
540 task_unlock(current);
545 * ptrace_get_task_struct -- grab a task struct reference for ptrace
546 * @pid: process id to grab a task_struct reference of
548 * This function is a helper for ptrace implementations. It checks
549 * permissions and then grabs a task struct for use of the actual
550 * ptrace implementation.
552 * Returns the task_struct for @pid or an ERR_PTR() on failure.
554 struct task_struct *ptrace_get_task_struct(pid_t pid)
556 struct task_struct *child;
558 read_lock(&tasklist_lock);
559 child = find_task_by_vpid(pid);
561 get_task_struct(child);
563 read_unlock(&tasklist_lock);
565 return ERR_PTR(-ESRCH);
569 #ifndef arch_ptrace_attach
570 #define arch_ptrace_attach(child) do { } while (0)
573 SYSCALL_DEFINE4(ptrace, long, request, long, pid, long, addr, long, data)
575 struct task_struct *child;
579 * This lock_kernel fixes a subtle race with suid exec
582 if (request == PTRACE_TRACEME) {
583 ret = ptrace_traceme();
585 arch_ptrace_attach(current);
589 child = ptrace_get_task_struct(pid);
591 ret = PTR_ERR(child);
595 if (request == PTRACE_ATTACH) {
596 ret = ptrace_attach(child);
598 * Some architectures need to do book-keeping after
602 arch_ptrace_attach(child);
603 goto out_put_task_struct;
606 ret = ptrace_check_attach(child, request == PTRACE_KILL);
608 goto out_put_task_struct;
610 ret = arch_ptrace(child, request, addr, data);
612 goto out_put_task_struct;
615 put_task_struct(child);
621 int generic_ptrace_peekdata(struct task_struct *tsk, long addr, long data)
626 copied = access_process_vm(tsk, addr, &tmp, sizeof(tmp), 0);
627 if (copied != sizeof(tmp))
629 return put_user(tmp, (unsigned long __user *)data);
632 int generic_ptrace_pokedata(struct task_struct *tsk, long addr, long data)
636 copied = access_process_vm(tsk, addr, &data, sizeof(data), 1);
637 return (copied == sizeof(data)) ? 0 : -EIO;
640 #if defined CONFIG_COMPAT
641 #include <linux/compat.h>
643 int compat_ptrace_request(struct task_struct *child, compat_long_t request,
644 compat_ulong_t addr, compat_ulong_t data)
646 compat_ulong_t __user *datap = compat_ptr(data);
652 case PTRACE_PEEKTEXT:
653 case PTRACE_PEEKDATA:
654 ret = access_process_vm(child, addr, &word, sizeof(word), 0);
655 if (ret != sizeof(word))
658 ret = put_user(word, datap);
661 case PTRACE_POKETEXT:
662 case PTRACE_POKEDATA:
663 ret = access_process_vm(child, addr, &data, sizeof(data), 1);
664 ret = (ret != sizeof(data) ? -EIO : 0);
667 case PTRACE_GETEVENTMSG:
668 ret = put_user((compat_ulong_t) child->ptrace_message, datap);
671 case PTRACE_GETSIGINFO:
672 ret = ptrace_getsiginfo(child, &siginfo);
674 ret = copy_siginfo_to_user32(
675 (struct compat_siginfo __user *) datap,
679 case PTRACE_SETSIGINFO:
680 memset(&siginfo, 0, sizeof siginfo);
681 if (copy_siginfo_from_user32(
682 &siginfo, (struct compat_siginfo __user *) datap))
685 ret = ptrace_setsiginfo(child, &siginfo);
689 ret = ptrace_request(child, request, addr, data);
695 asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
696 compat_long_t addr, compat_long_t data)
698 struct task_struct *child;
702 * This lock_kernel fixes a subtle race with suid exec
705 if (request == PTRACE_TRACEME) {
706 ret = ptrace_traceme();
710 child = ptrace_get_task_struct(pid);
712 ret = PTR_ERR(child);
716 if (request == PTRACE_ATTACH) {
717 ret = ptrace_attach(child);
719 * Some architectures need to do book-keeping after
723 arch_ptrace_attach(child);
724 goto out_put_task_struct;
727 ret = ptrace_check_attach(child, request == PTRACE_KILL);
729 ret = compat_arch_ptrace(child, request, addr, data);
732 put_task_struct(child);
737 #endif /* CONFIG_COMPAT */