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>
22 #include <asm/pgtable.h>
23 #include <asm/uaccess.h>
26 * ptrace a task: make the debugger its new parent and
27 * move it to the ptrace list.
29 * Must be called with the tasklist lock write-held.
31 void __ptrace_link(task_t *child, task_t *new_parent)
33 BUG_ON(!list_empty(&child->ptrace_list));
34 if (child->parent == new_parent)
36 list_add(&child->ptrace_list, &child->parent->ptrace_children);
38 child->parent = new_parent;
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.
49 void ptrace_untrace(task_t *child)
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;
56 signal_wake_up(child, 1);
59 spin_unlock(&child->sighand->siglock);
63 * unptrace a task: move it back to its original parent and
64 * remove it from the ptrace list.
66 * Must be called with the tasklist lock write-held.
68 void __ptrace_unlink(task_t *child)
70 BUG_ON(!child->ptrace);
73 if (!list_empty(&child->ptrace_list)) {
74 list_del_init(&child->ptrace_list);
76 child->parent = child->real_parent;
80 if (child->state == TASK_TRACED)
81 ptrace_untrace(child);
85 * Check that we have indeed attached to the thing..
87 int ptrace_check_attach(struct task_struct *child, int kill)
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.
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) {
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) {
109 spin_unlock_irq(&child->sighand->siglock);
111 read_unlock(&tasklist_lock);
114 wait_task_inactive(child);
117 /* All systems go.. */
121 static int may_attach(struct task_struct *task)
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.
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.
132 /* Don't let security modules deny introspection */
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))
144 dumpable = task->mm->dumpable;
145 if (!dumpable && !capable(CAP_SYS_PTRACE))
148 return security_ptrace(current, task);
151 int ptrace_may_attach(struct task_struct *task)
155 err = may_attach(task);
160 int ptrace_attach(struct task_struct *task)
167 if (task->tgid == current->tgid)
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).
182 if (!write_trylock(&tasklist_lock)) {
187 } while (!write_can_lock(&tasklist_lock));
193 /* the same process cannot be attached many times */
194 if (task->ptrace & PT_PTRACED)
196 retval = may_attach(task);
201 task->ptrace |= PT_PTRACED | ((task->real_parent != current)
203 if (capable(CAP_SYS_PTRACE))
204 task->ptrace |= PT_PTRACE_CAP;
206 __ptrace_link(task, current);
208 force_sig_specific(SIGSTOP, task);
211 write_unlock_irq(&tasklist_lock);
217 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);
235 write_lock_irq(&tasklist_lock);
237 __ptrace_detach(child, data);
238 write_unlock_irq(&tasklist_lock);
244 * Access another process' address space.
245 * Source/target buffer must be kernel space,
246 * Do not walk the page table directly, use get_user_pages
249 int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
251 struct mm_struct *mm;
252 struct vm_area_struct *vma;
256 mm = get_task_mm(tsk);
260 down_read(&mm->mmap_sem);
261 /* ignore errors, just check how much was sucessfully transfered */
263 int bytes, ret, offset;
266 ret = get_user_pages(tsk, mm, addr, 1,
267 write, 1, &page, &vma);
272 offset = addr & (PAGE_SIZE-1);
273 if (bytes > PAGE_SIZE-offset)
274 bytes = PAGE_SIZE-offset;
278 copy_to_user_page(vma, page, addr,
279 maddr + offset, buf, bytes);
280 set_page_dirty_lock(page);
282 copy_from_user_page(vma, page, addr,
283 buf, maddr + offset, bytes);
286 page_cache_release(page);
291 up_read(&mm->mmap_sem);
294 return buf - old_buf;
297 int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
303 int this_len, retval;
305 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
306 retval = access_process_vm(tsk, src, buf, this_len, 0);
312 if (copy_to_user(dst, buf, retval))
322 int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len)
328 int this_len, retval;
330 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
331 if (copy_from_user(buf, src, this_len))
333 retval = access_process_vm(tsk, dst, buf, this_len, 1);
347 static int ptrace_setoptions(struct task_struct *child, long data)
349 child->ptrace &= ~PT_TRACE_MASK;
351 if (data & PTRACE_O_TRACESYSGOOD)
352 child->ptrace |= PT_TRACESYSGOOD;
354 if (data & PTRACE_O_TRACEFORK)
355 child->ptrace |= PT_TRACE_FORK;
357 if (data & PTRACE_O_TRACEVFORK)
358 child->ptrace |= PT_TRACE_VFORK;
360 if (data & PTRACE_O_TRACECLONE)
361 child->ptrace |= PT_TRACE_CLONE;
363 if (data & PTRACE_O_TRACEEXEC)
364 child->ptrace |= PT_TRACE_EXEC;
366 if (data & PTRACE_O_TRACEVFORKDONE)
367 child->ptrace |= PT_TRACE_VFORK_DONE;
369 if (data & PTRACE_O_TRACEEXIT)
370 child->ptrace |= PT_TRACE_EXIT;
372 return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
375 static int ptrace_getsiginfo(struct task_struct *child, siginfo_t __user * data)
380 read_lock(&tasklist_lock);
381 if (likely(child->sighand != NULL)) {
383 spin_lock_irq(&child->sighand->siglock);
384 if (likely(child->last_siginfo != NULL)) {
385 lastinfo = *child->last_siginfo;
388 spin_unlock_irq(&child->sighand->siglock);
390 read_unlock(&tasklist_lock);
392 return copy_siginfo_to_user(data, &lastinfo);
396 static int ptrace_setsiginfo(struct task_struct *child, siginfo_t __user * data)
401 if (copy_from_user(&newinfo, data, sizeof (siginfo_t)))
404 read_lock(&tasklist_lock);
405 if (likely(child->sighand != NULL)) {
407 spin_lock_irq(&child->sighand->siglock);
408 if (likely(child->last_siginfo != NULL)) {
409 *child->last_siginfo = newinfo;
412 spin_unlock_irq(&child->sighand->siglock);
414 read_unlock(&tasklist_lock);
418 int ptrace_request(struct task_struct *child, long request,
419 long addr, long data)
424 #ifdef PTRACE_OLDSETOPTIONS
425 case PTRACE_OLDSETOPTIONS:
427 case PTRACE_SETOPTIONS:
428 ret = ptrace_setoptions(child, data);
430 case PTRACE_GETEVENTMSG:
431 ret = put_user(child->ptrace_message, (unsigned long __user *) data);
433 case PTRACE_GETSIGINFO:
434 ret = ptrace_getsiginfo(child, (siginfo_t __user *) data);
436 case PTRACE_SETSIGINFO:
437 ret = ptrace_setsiginfo(child, (siginfo_t __user *) data);
447 * ptrace_traceme -- helper for PTRACE_TRACEME
449 * Performs checks and sets PT_PTRACED.
450 * Should be used by all ptrace implementations for PTRACE_TRACEME.
452 int ptrace_traceme(void)
457 * Are we already being traced?
460 if (!(current->ptrace & PT_PTRACED)) {
461 ret = security_ptrace(current->parent, current);
463 * Set the ptrace bit in the process ptrace flags.
466 current->ptrace |= PT_PTRACED;
468 task_unlock(current);
473 * ptrace_get_task_struct -- grab a task struct reference for ptrace
474 * @pid: process id to grab a task_struct reference of
476 * This function is a helper for ptrace implementations. It checks
477 * permissions and then grabs a task struct for use of the actual
478 * ptrace implementation.
480 * Returns the task_struct for @pid or an ERR_PTR() on failure.
482 struct task_struct *ptrace_get_task_struct(pid_t pid)
484 struct task_struct *child;
487 * Tracing init is not allowed.
490 return ERR_PTR(-EPERM);
492 read_lock(&tasklist_lock);
493 child = find_task_by_pid(pid);
495 get_task_struct(child);
496 read_unlock(&tasklist_lock);
498 return ERR_PTR(-ESRCH);
502 #ifndef __ARCH_SYS_PTRACE
503 asmlinkage long sys_ptrace(long request, long pid, long addr, long data)
505 struct task_struct *child;
509 * This lock_kernel fixes a subtle race with suid exec
512 if (request == PTRACE_TRACEME) {
513 ret = ptrace_traceme();
517 child = ptrace_get_task_struct(pid);
519 ret = PTR_ERR(child);
523 if (request == PTRACE_ATTACH) {
524 ret = ptrace_attach(child);
525 goto out_put_task_struct;
528 ret = ptrace_check_attach(child, request == PTRACE_KILL);
530 goto out_put_task_struct;
532 ret = arch_ptrace(child, request, addr, data);
534 goto out_put_task_struct;
537 put_task_struct(child);
542 #endif /* __ARCH_SYS_PTRACE */