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/vs_base.h>
23 #include <asm/pgtable.h>
24 #include <asm/uaccess.h>
27 * ptrace a task: make the debugger its new parent and
28 * move it to the ptrace list.
30 * Must be called with the tasklist lock write-held.
32 void __ptrace_link(struct task_struct *child, struct task_struct *new_parent)
34 BUG_ON(!list_empty(&child->ptrace_list));
35 if (child->parent == new_parent)
37 list_add(&child->ptrace_list, &child->parent->ptrace_children);
39 child->parent = new_parent;
44 * Turn a tracing stop into a normal stop now, since with no tracer there
45 * would be no way to wake it up with SIGCONT or SIGKILL. If there was a
46 * signal sent that would resume the child, but didn't because it was in
47 * TASK_TRACED, resume it now.
48 * Requires that irqs be disabled.
50 void ptrace_untrace(struct task_struct *child)
52 spin_lock(&child->sighand->siglock);
53 if (child->state == TASK_TRACED) {
54 if (child->signal->flags & SIGNAL_STOP_STOPPED) {
55 child->state = TASK_STOPPED;
57 signal_wake_up(child, 1);
60 spin_unlock(&child->sighand->siglock);
64 * unptrace a task: move it back to its original parent and
65 * remove it from the ptrace list.
67 * Must be called with the tasklist lock write-held.
69 void __ptrace_unlink(struct task_struct *child)
71 BUG_ON(!child->ptrace);
74 if (!list_empty(&child->ptrace_list)) {
75 list_del_init(&child->ptrace_list);
77 child->parent = child->real_parent;
81 if (child->state == TASK_TRACED)
82 ptrace_untrace(child);
86 * Check that we have indeed attached to the thing..
88 int ptrace_check_attach(struct task_struct *child, int kill)
93 * We take the read lock around doing both checks to close a
94 * possible race where someone else was tracing our child and
95 * detached between these two checks. After this locked check,
96 * we are sure that this is our traced child and that can only
97 * be changed by us so it's not changing right after this.
99 read_lock(&tasklist_lock);
100 if ((child->ptrace & PT_PTRACED) && child->parent == current &&
101 (!(child->ptrace & PT_ATTACHED) || child->real_parent != current)
102 && child->signal != NULL) {
104 spin_lock_irq(&child->sighand->siglock);
105 if (child->state == TASK_STOPPED) {
106 child->state = TASK_TRACED;
107 } else if (child->state != TASK_TRACED && !kill) {
110 spin_unlock_irq(&child->sighand->siglock);
112 read_unlock(&tasklist_lock);
114 /* All systems go.. */
118 int __ptrace_may_attach(struct task_struct *task)
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 */
132 if (((current->uid != task->euid) ||
133 (current->uid != task->suid) ||
134 (current->uid != task->uid) ||
135 (current->gid != task->egid) ||
136 (current->gid != task->sgid) ||
137 (current->gid != task->gid)) && !capable(CAP_SYS_PTRACE))
141 dumpable = task->mm->dumpable;
142 if (!dumpable && !capable(CAP_SYS_PTRACE))
145 return security_ptrace(current, task);
148 int ptrace_may_attach(struct task_struct *task)
152 err = __ptrace_may_attach(task);
157 int ptrace_attach(struct task_struct *task)
164 if (task->tgid == current->tgid)
171 * We want to hold both the task-lock and the
172 * tasklist_lock for writing at the same time.
173 * But that's against the rules (tasklist_lock
174 * is taken for reading by interrupts on other
175 * cpu's that may have task_lock).
179 if (!write_trylock(&tasklist_lock)) {
184 } while (!write_can_lock(&tasklist_lock));
190 /* the same process cannot be attached many times */
191 if (task->ptrace & PT_PTRACED)
193 retval = __ptrace_may_attach(task);
198 task->ptrace |= PT_PTRACED | ((task->real_parent != current)
200 if (capable(CAP_SYS_PTRACE))
201 task->ptrace |= PT_PTRACE_CAP;
203 __ptrace_link(task, current);
205 force_sig_specific(SIGSTOP, task);
208 write_unlock_irq(&tasklist_lock);
214 static inline void __ptrace_detach(struct task_struct *child, unsigned int data)
216 child->exit_code = data;
217 /* .. re-parent .. */
218 __ptrace_unlink(child);
219 /* .. and wake it up. */
220 if (child->exit_state != EXIT_ZOMBIE)
221 wake_up_process(child);
224 int ptrace_detach(struct task_struct *child, unsigned int data)
226 if (!valid_signal(data))
229 /* Architecture-specific hardware disable .. */
230 ptrace_disable(child);
232 write_lock_irq(&tasklist_lock);
233 /* protect against de_thread()->release_task() */
235 __ptrace_detach(child, data);
236 write_unlock_irq(&tasklist_lock);
242 * Access another process' address space.
243 * Source/target buffer must be kernel space,
244 * Do not walk the page table directly, use get_user_pages
247 int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
249 struct mm_struct *mm;
250 struct vm_area_struct *vma;
254 mm = get_task_mm(tsk);
258 down_read(&mm->mmap_sem);
259 /* ignore errors, just check how much was sucessfully transfered */
261 int bytes, ret, offset;
264 ret = get_user_pages(tsk, mm, addr, 1,
265 write, 1, &page, &vma);
270 offset = addr & (PAGE_SIZE-1);
271 if (bytes > PAGE_SIZE-offset)
272 bytes = PAGE_SIZE-offset;
276 copy_to_user_page(vma, page, addr,
277 maddr + offset, buf, bytes);
278 set_page_dirty_lock(page);
280 copy_from_user_page(vma, page, addr,
281 buf, maddr + offset, bytes);
284 page_cache_release(page);
289 up_read(&mm->mmap_sem);
292 return buf - old_buf;
295 int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
301 int this_len, retval;
303 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
304 retval = access_process_vm(tsk, src, buf, this_len, 0);
310 if (copy_to_user(dst, buf, retval))
320 int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len)
326 int this_len, retval;
328 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
329 if (copy_from_user(buf, src, this_len))
331 retval = access_process_vm(tsk, dst, buf, this_len, 1);
345 static int ptrace_setoptions(struct task_struct *child, long data)
347 child->ptrace &= ~PT_TRACE_MASK;
349 if (data & PTRACE_O_TRACESYSGOOD)
350 child->ptrace |= PT_TRACESYSGOOD;
352 if (data & PTRACE_O_TRACEFORK)
353 child->ptrace |= PT_TRACE_FORK;
355 if (data & PTRACE_O_TRACEVFORK)
356 child->ptrace |= PT_TRACE_VFORK;
358 if (data & PTRACE_O_TRACECLONE)
359 child->ptrace |= PT_TRACE_CLONE;
361 if (data & PTRACE_O_TRACEEXEC)
362 child->ptrace |= PT_TRACE_EXEC;
364 if (data & PTRACE_O_TRACEVFORKDONE)
365 child->ptrace |= PT_TRACE_VFORK_DONE;
367 if (data & PTRACE_O_TRACEEXIT)
368 child->ptrace |= PT_TRACE_EXIT;
370 return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
373 static int ptrace_getsiginfo(struct task_struct *child, siginfo_t __user * data)
378 read_lock(&tasklist_lock);
379 if (likely(child->sighand != NULL)) {
381 spin_lock_irq(&child->sighand->siglock);
382 if (likely(child->last_siginfo != NULL)) {
383 lastinfo = *child->last_siginfo;
386 spin_unlock_irq(&child->sighand->siglock);
388 read_unlock(&tasklist_lock);
390 return copy_siginfo_to_user(data, &lastinfo);
394 static int ptrace_setsiginfo(struct task_struct *child, siginfo_t __user * data)
399 if (copy_from_user(&newinfo, data, sizeof (siginfo_t)))
402 read_lock(&tasklist_lock);
403 if (likely(child->sighand != NULL)) {
405 spin_lock_irq(&child->sighand->siglock);
406 if (likely(child->last_siginfo != NULL)) {
407 *child->last_siginfo = newinfo;
410 spin_unlock_irq(&child->sighand->siglock);
412 read_unlock(&tasklist_lock);
416 int ptrace_request(struct task_struct *child, long request,
417 long addr, long data)
422 #ifdef PTRACE_OLDSETOPTIONS
423 case PTRACE_OLDSETOPTIONS:
425 case PTRACE_SETOPTIONS:
426 ret = ptrace_setoptions(child, data);
428 case PTRACE_GETEVENTMSG:
429 ret = put_user(child->ptrace_message, (unsigned long __user *) data);
431 case PTRACE_GETSIGINFO:
432 ret = ptrace_getsiginfo(child, (siginfo_t __user *) data);
434 case PTRACE_SETSIGINFO:
435 ret = ptrace_setsiginfo(child, (siginfo_t __user *) data);
445 * ptrace_traceme -- helper for PTRACE_TRACEME
447 * Performs checks and sets PT_PTRACED.
448 * Should be used by all ptrace implementations for PTRACE_TRACEME.
450 int ptrace_traceme(void)
455 * Are we already being traced?
458 if (!(current->ptrace & PT_PTRACED)) {
459 ret = security_ptrace(current->parent, current);
461 * Set the ptrace bit in the process ptrace flags.
464 current->ptrace |= PT_PTRACED;
466 task_unlock(current);
471 * ptrace_get_task_struct -- grab a task struct reference for ptrace
472 * @pid: process id to grab a task_struct reference of
474 * This function is a helper for ptrace implementations. It checks
475 * permissions and then grabs a task struct for use of the actual
476 * ptrace implementation.
478 * Returns the task_struct for @pid or an ERR_PTR() on failure.
480 struct task_struct *ptrace_get_task_struct(pid_t pid)
482 struct task_struct *child;
485 * Tracing init is not allowed.
488 return ERR_PTR(-EPERM);
490 read_lock(&tasklist_lock);
491 child = find_task_by_pid(pid);
493 get_task_struct(child);
494 read_unlock(&tasklist_lock);
496 return ERR_PTR(-ESRCH);
500 #ifndef __ARCH_SYS_PTRACE
501 asmlinkage long sys_ptrace(long request, long pid, long addr, long data)
503 struct task_struct *child;
507 * This lock_kernel fixes a subtle race with suid exec
510 if (request == PTRACE_TRACEME) {
511 ret = ptrace_traceme();
515 child = ptrace_get_task_struct(pid);
517 ret = PTR_ERR(child);
522 if (!vx_check(vx_task_xid(child), VX_WATCH|VX_IDENT))
523 goto out_put_task_struct;
525 if (request == PTRACE_ATTACH) {
526 ret = ptrace_attach(child);
527 goto out_put_task_struct;
530 ret = ptrace_check_attach(child, request == PTRACE_KILL);
532 goto out_put_task_struct;
534 ret = arch_ptrace(child, request, addr, data);
536 goto out_put_task_struct;
539 put_task_struct(child);
544 #endif /* __ARCH_SYS_PTRACE */