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)
125 if (((current->uid != task->euid) ||
126 (current->uid != task->suid) ||
127 (current->uid != task->uid) ||
128 (current->gid != task->egid) ||
129 (current->gid != task->sgid) ||
130 (current->gid != task->gid)) && !capable(CAP_SYS_PTRACE))
133 if (!task->mm->dumpable && !capable(CAP_SYS_PTRACE))
136 return security_ptrace(current, task);
139 int ptrace_may_attach(struct task_struct *task)
143 err = may_attach(task);
148 int ptrace_attach(struct task_struct *task)
155 if (task->tgid == current->tgid)
158 write_lock_irq(&tasklist_lock);
161 /* the same process cannot be attached many times */
162 if (task->ptrace & PT_PTRACED)
164 retval = may_attach(task);
169 task->ptrace |= PT_PTRACED | ((task->real_parent != current)
171 if (capable(CAP_SYS_PTRACE))
172 task->ptrace |= PT_PTRACE_CAP;
174 __ptrace_link(task, current);
176 force_sig_specific(SIGSTOP, task);
179 write_unlock_irq(&tasklist_lock);
185 void __ptrace_detach(struct task_struct *child, unsigned int data)
187 child->exit_code = data;
188 /* .. re-parent .. */
189 __ptrace_unlink(child);
190 /* .. and wake it up. */
191 if (child->exit_state != EXIT_ZOMBIE)
192 wake_up_process(child);
195 int ptrace_detach(struct task_struct *child, unsigned int data)
197 if (!valid_signal(data))
200 /* Architecture-specific hardware disable .. */
201 ptrace_disable(child);
203 write_lock_irq(&tasklist_lock);
205 __ptrace_detach(child, data);
206 write_unlock_irq(&tasklist_lock);
212 * Access another process' address space.
213 * Source/target buffer must be kernel space,
214 * Do not walk the page table directly, use get_user_pages
217 int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
219 struct mm_struct *mm;
220 struct vm_area_struct *vma;
224 mm = get_task_mm(tsk);
228 down_read(&mm->mmap_sem);
229 /* ignore errors, just check how much was sucessfully transfered */
231 int bytes, ret, offset;
234 ret = get_user_pages(tsk, mm, addr, 1,
235 write, 1, &page, &vma);
240 offset = addr & (PAGE_SIZE-1);
241 if (bytes > PAGE_SIZE-offset)
242 bytes = PAGE_SIZE-offset;
246 copy_to_user_page(vma, page, addr,
247 maddr + offset, buf, bytes);
248 set_page_dirty_lock(page);
250 copy_from_user_page(vma, page, addr,
251 buf, maddr + offset, bytes);
254 page_cache_release(page);
259 up_read(&mm->mmap_sem);
262 return buf - old_buf;
265 int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
271 int this_len, retval;
273 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
274 retval = access_process_vm(tsk, src, buf, this_len, 0);
280 if (copy_to_user(dst, buf, retval))
290 int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len)
296 int this_len, retval;
298 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
299 if (copy_from_user(buf, src, this_len))
301 retval = access_process_vm(tsk, dst, buf, this_len, 1);
315 static int ptrace_setoptions(struct task_struct *child, long data)
317 child->ptrace &= ~PT_TRACE_MASK;
319 if (data & PTRACE_O_TRACESYSGOOD)
320 child->ptrace |= PT_TRACESYSGOOD;
322 if (data & PTRACE_O_TRACEFORK)
323 child->ptrace |= PT_TRACE_FORK;
325 if (data & PTRACE_O_TRACEVFORK)
326 child->ptrace |= PT_TRACE_VFORK;
328 if (data & PTRACE_O_TRACECLONE)
329 child->ptrace |= PT_TRACE_CLONE;
331 if (data & PTRACE_O_TRACEEXEC)
332 child->ptrace |= PT_TRACE_EXEC;
334 if (data & PTRACE_O_TRACEVFORKDONE)
335 child->ptrace |= PT_TRACE_VFORK_DONE;
337 if (data & PTRACE_O_TRACEEXIT)
338 child->ptrace |= PT_TRACE_EXIT;
340 return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
343 static int ptrace_getsiginfo(struct task_struct *child, siginfo_t __user * data)
348 read_lock(&tasklist_lock);
349 if (likely(child->sighand != NULL)) {
351 spin_lock_irq(&child->sighand->siglock);
352 if (likely(child->last_siginfo != NULL)) {
353 lastinfo = *child->last_siginfo;
356 spin_unlock_irq(&child->sighand->siglock);
358 read_unlock(&tasklist_lock);
360 return copy_siginfo_to_user(data, &lastinfo);
364 static int ptrace_setsiginfo(struct task_struct *child, siginfo_t __user * data)
369 if (copy_from_user(&newinfo, data, sizeof (siginfo_t)))
372 read_lock(&tasklist_lock);
373 if (likely(child->sighand != NULL)) {
375 spin_lock_irq(&child->sighand->siglock);
376 if (likely(child->last_siginfo != NULL)) {
377 *child->last_siginfo = newinfo;
380 spin_unlock_irq(&child->sighand->siglock);
382 read_unlock(&tasklist_lock);
386 int ptrace_request(struct task_struct *child, long request,
387 long addr, long data)
392 #ifdef PTRACE_OLDSETOPTIONS
393 case PTRACE_OLDSETOPTIONS:
395 case PTRACE_SETOPTIONS:
396 ret = ptrace_setoptions(child, data);
398 case PTRACE_GETEVENTMSG:
399 ret = put_user(child->ptrace_message, (unsigned long __user *) data);
401 case PTRACE_GETSIGINFO:
402 ret = ptrace_getsiginfo(child, (siginfo_t __user *) data);
404 case PTRACE_SETSIGINFO:
405 ret = ptrace_setsiginfo(child, (siginfo_t __user *) data);
415 * ptrace_traceme -- helper for PTRACE_TRACEME
417 * Performs checks and sets PT_PTRACED.
418 * Should be used by all ptrace implementations for PTRACE_TRACEME.
420 int ptrace_traceme(void)
425 * Are we already being traced?
428 if (!(current->ptrace & PT_PTRACED)) {
429 ret = security_ptrace(current->parent, current);
431 * Set the ptrace bit in the process ptrace flags.
434 current->ptrace |= PT_PTRACED;
436 task_unlock(current);
441 * ptrace_get_task_struct -- grab a task struct reference for ptrace
442 * @pid: process id to grab a task_struct reference of
444 * This function is a helper for ptrace implementations. It checks
445 * permissions and then grabs a task struct for use of the actual
446 * ptrace implementation.
448 * Returns the task_struct for @pid or an ERR_PTR() on failure.
450 struct task_struct *ptrace_get_task_struct(pid_t pid)
452 struct task_struct *child;
455 * Tracing init is not allowed.
458 return ERR_PTR(-EPERM);
460 read_lock(&tasklist_lock);
461 child = find_task_by_pid(pid);
463 get_task_struct(child);
464 read_unlock(&tasklist_lock);
466 return ERR_PTR(-ESRCH);
470 #ifndef __ARCH_SYS_PTRACE
471 asmlinkage long sys_ptrace(long request, long pid, long addr, long data)
473 struct task_struct *child;
477 * This lock_kernel fixes a subtle race with suid exec
480 if (request == PTRACE_TRACEME) {
481 ret = ptrace_traceme();
485 child = ptrace_get_task_struct(pid);
487 ret = PTR_ERR(child);
491 if (request == PTRACE_ATTACH) {
492 ret = ptrace_attach(child);
493 goto out_put_task_struct;
496 ret = ptrace_check_attach(child, request == PTRACE_KILL);
498 goto out_put_task_struct;
500 ret = arch_ptrace(child, request, addr, data);
502 goto out_put_task_struct;
505 put_task_struct(child);
510 #endif /* __ARCH_SYS_PTRACE */