xref: /openbmc/linux/include/linux/ptrace.h (revision fdd12a80)
1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _LINUX_PTRACE_H
3 #define _LINUX_PTRACE_H
4 
5 #include <linux/compiler.h>		/* For unlikely.  */
6 #include <linux/sched.h>		/* For struct task_struct.  */
7 #include <linux/sched/signal.h>		/* For send_sig(), same_thread_group(), etc. */
8 #include <linux/err.h>			/* for IS_ERR_VALUE */
9 #include <linux/bug.h>			/* For BUG_ON.  */
10 #include <linux/pid_namespace.h>	/* For task_active_pid_ns.  */
11 #include <uapi/linux/ptrace.h>
12 #include <linux/seccomp.h>
13 
14 /* Add sp to seccomp_data, as seccomp is user API, we don't want to modify it */
15 struct syscall_info {
16 	__u64			sp;
17 	struct seccomp_data	data;
18 };
19 
20 extern int ptrace_access_vm(struct task_struct *tsk, unsigned long addr,
21 			    void *buf, int len, unsigned int gup_flags);
22 
23 /*
24  * Ptrace flags
25  *
26  * The owner ship rules for task->ptrace which holds the ptrace
27  * flags is simple.  When a task is running it owns it's task->ptrace
28  * flags.  When the a task is stopped the ptracer owns task->ptrace.
29  */
30 
31 #define PT_SEIZED	0x00010000	/* SEIZE used, enable new behavior */
32 #define PT_PTRACED	0x00000001
33 
34 #define PT_OPT_FLAG_SHIFT	3
35 /* PT_TRACE_* event enable flags */
36 #define PT_EVENT_FLAG(event)	(1 << (PT_OPT_FLAG_SHIFT + (event)))
37 #define PT_TRACESYSGOOD		PT_EVENT_FLAG(0)
38 #define PT_TRACE_FORK		PT_EVENT_FLAG(PTRACE_EVENT_FORK)
39 #define PT_TRACE_VFORK		PT_EVENT_FLAG(PTRACE_EVENT_VFORK)
40 #define PT_TRACE_CLONE		PT_EVENT_FLAG(PTRACE_EVENT_CLONE)
41 #define PT_TRACE_EXEC		PT_EVENT_FLAG(PTRACE_EVENT_EXEC)
42 #define PT_TRACE_VFORK_DONE	PT_EVENT_FLAG(PTRACE_EVENT_VFORK_DONE)
43 #define PT_TRACE_EXIT		PT_EVENT_FLAG(PTRACE_EVENT_EXIT)
44 #define PT_TRACE_SECCOMP	PT_EVENT_FLAG(PTRACE_EVENT_SECCOMP)
45 
46 #define PT_EXITKILL		(PTRACE_O_EXITKILL << PT_OPT_FLAG_SHIFT)
47 #define PT_SUSPEND_SECCOMP	(PTRACE_O_SUSPEND_SECCOMP << PT_OPT_FLAG_SHIFT)
48 
49 extern long arch_ptrace(struct task_struct *child, long request,
50 			unsigned long addr, unsigned long data);
51 extern int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len);
52 extern int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len);
53 extern void ptrace_disable(struct task_struct *);
54 extern int ptrace_request(struct task_struct *child, long request,
55 			  unsigned long addr, unsigned long data);
56 extern int ptrace_notify(int exit_code, unsigned long message);
57 extern void __ptrace_link(struct task_struct *child,
58 			  struct task_struct *new_parent,
59 			  const struct cred *ptracer_cred);
60 extern void __ptrace_unlink(struct task_struct *child);
61 extern void exit_ptrace(struct task_struct *tracer, struct list_head *dead);
62 #define PTRACE_MODE_READ	0x01
63 #define PTRACE_MODE_ATTACH	0x02
64 #define PTRACE_MODE_NOAUDIT	0x04
65 #define PTRACE_MODE_FSCREDS	0x08
66 #define PTRACE_MODE_REALCREDS	0x10
67 
68 /* shorthands for READ/ATTACH and FSCREDS/REALCREDS combinations */
69 #define PTRACE_MODE_READ_FSCREDS (PTRACE_MODE_READ | PTRACE_MODE_FSCREDS)
70 #define PTRACE_MODE_READ_REALCREDS (PTRACE_MODE_READ | PTRACE_MODE_REALCREDS)
71 #define PTRACE_MODE_ATTACH_FSCREDS (PTRACE_MODE_ATTACH | PTRACE_MODE_FSCREDS)
72 #define PTRACE_MODE_ATTACH_REALCREDS (PTRACE_MODE_ATTACH | PTRACE_MODE_REALCREDS)
73 
74 /**
75  * ptrace_may_access - check whether the caller is permitted to access
76  * a target task.
77  * @task: target task
78  * @mode: selects type of access and caller credentials
79  *
80  * Returns true on success, false on denial.
81  *
82  * One of the flags PTRACE_MODE_FSCREDS and PTRACE_MODE_REALCREDS must
83  * be set in @mode to specify whether the access was requested through
84  * a filesystem syscall (should use effective capabilities and fsuid
85  * of the caller) or through an explicit syscall such as
86  * process_vm_writev or ptrace (and should use the real credentials).
87  */
88 extern bool ptrace_may_access(struct task_struct *task, unsigned int mode);
89 
ptrace_reparented(struct task_struct * child)90 static inline int ptrace_reparented(struct task_struct *child)
91 {
92 	return !same_thread_group(child->real_parent, child->parent);
93 }
94 
ptrace_unlink(struct task_struct * child)95 static inline void ptrace_unlink(struct task_struct *child)
96 {
97 	if (unlikely(child->ptrace))
98 		__ptrace_unlink(child);
99 }
100 
101 int generic_ptrace_peekdata(struct task_struct *tsk, unsigned long addr,
102 			    unsigned long data);
103 int generic_ptrace_pokedata(struct task_struct *tsk, unsigned long addr,
104 			    unsigned long data);
105 
106 /**
107  * ptrace_parent - return the task that is tracing the given task
108  * @task: task to consider
109  *
110  * Returns %NULL if no one is tracing @task, or the &struct task_struct
111  * pointer to its tracer.
112  *
113  * Must called under rcu_read_lock().  The pointer returned might be kept
114  * live only by RCU.  During exec, this may be called with task_lock() held
115  * on @task, still held from when check_unsafe_exec() was called.
116  */
ptrace_parent(struct task_struct * task)117 static inline struct task_struct *ptrace_parent(struct task_struct *task)
118 {
119 	if (unlikely(task->ptrace))
120 		return rcu_dereference(task->parent);
121 	return NULL;
122 }
123 
124 /**
125  * ptrace_event_enabled - test whether a ptrace event is enabled
126  * @task: ptracee of interest
127  * @event: %PTRACE_EVENT_* to test
128  *
129  * Test whether @event is enabled for ptracee @task.
130  *
131  * Returns %true if @event is enabled, %false otherwise.
132  */
ptrace_event_enabled(struct task_struct * task,int event)133 static inline bool ptrace_event_enabled(struct task_struct *task, int event)
134 {
135 	return task->ptrace & PT_EVENT_FLAG(event);
136 }
137 
138 /**
139  * ptrace_event - possibly stop for a ptrace event notification
140  * @event:	%PTRACE_EVENT_* value to report
141  * @message:	value for %PTRACE_GETEVENTMSG to return
142  *
143  * Check whether @event is enabled and, if so, report @event and @message
144  * to the ptrace parent.
145  *
146  * Called without locks.
147  */
ptrace_event(int event,unsigned long message)148 static inline void ptrace_event(int event, unsigned long message)
149 {
150 	if (unlikely(ptrace_event_enabled(current, event))) {
151 		ptrace_notify((event << 8) | SIGTRAP, message);
152 	} else if (event == PTRACE_EVENT_EXEC) {
153 		/* legacy EXEC report via SIGTRAP */
154 		if ((current->ptrace & (PT_PTRACED|PT_SEIZED)) == PT_PTRACED)
155 			send_sig(SIGTRAP, current, 0);
156 	}
157 }
158 
159 /**
160  * ptrace_event_pid - possibly stop for a ptrace event notification
161  * @event:	%PTRACE_EVENT_* value to report
162  * @pid:	process identifier for %PTRACE_GETEVENTMSG to return
163  *
164  * Check whether @event is enabled and, if so, report @event and @pid
165  * to the ptrace parent.  @pid is reported as the pid_t seen from the
166  * ptrace parent's pid namespace.
167  *
168  * Called without locks.
169  */
ptrace_event_pid(int event,struct pid * pid)170 static inline void ptrace_event_pid(int event, struct pid *pid)
171 {
172 	/*
173 	 * FIXME: There's a potential race if a ptracer in a different pid
174 	 * namespace than parent attaches between computing message below and
175 	 * when we acquire tasklist_lock in ptrace_stop().  If this happens,
176 	 * the ptracer will get a bogus pid from PTRACE_GETEVENTMSG.
177 	 */
178 	unsigned long message = 0;
179 	struct pid_namespace *ns;
180 
181 	rcu_read_lock();
182 	ns = task_active_pid_ns(rcu_dereference(current->parent));
183 	if (ns)
184 		message = pid_nr_ns(pid, ns);
185 	rcu_read_unlock();
186 
187 	ptrace_event(event, message);
188 }
189 
190 /**
191  * ptrace_init_task - initialize ptrace state for a new child
192  * @child:		new child task
193  * @ptrace:		true if child should be ptrace'd by parent's tracer
194  *
195  * This is called immediately after adding @child to its parent's children
196  * list.  @ptrace is false in the normal case, and true to ptrace @child.
197  *
198  * Called with current's siglock and write_lock_irq(&tasklist_lock) held.
199  */
ptrace_init_task(struct task_struct * child,bool ptrace)200 static inline void ptrace_init_task(struct task_struct *child, bool ptrace)
201 {
202 	INIT_LIST_HEAD(&child->ptrace_entry);
203 	INIT_LIST_HEAD(&child->ptraced);
204 	child->jobctl = 0;
205 	child->ptrace = 0;
206 	child->parent = child->real_parent;
207 
208 	if (unlikely(ptrace) && current->ptrace) {
209 		child->ptrace = current->ptrace;
210 		__ptrace_link(child, current->parent, current->ptracer_cred);
211 
212 		if (child->ptrace & PT_SEIZED)
213 			task_set_jobctl_pending(child, JOBCTL_TRAP_STOP);
214 		else
215 			sigaddset(&child->pending.signal, SIGSTOP);
216 	}
217 	else
218 		child->ptracer_cred = NULL;
219 }
220 
221 /**
222  * ptrace_release_task - final ptrace-related cleanup of a zombie being reaped
223  * @task:	task in %EXIT_DEAD state
224  *
225  * Called with write_lock(&tasklist_lock) held.
226  */
ptrace_release_task(struct task_struct * task)227 static inline void ptrace_release_task(struct task_struct *task)
228 {
229 	BUG_ON(!list_empty(&task->ptraced));
230 	ptrace_unlink(task);
231 	BUG_ON(!list_empty(&task->ptrace_entry));
232 }
233 
234 #ifndef force_successful_syscall_return
235 /*
236  * System call handlers that, upon successful completion, need to return a
237  * negative value should call force_successful_syscall_return() right before
238  * returning.  On architectures where the syscall convention provides for a
239  * separate error flag (e.g., alpha, ia64, ppc{,64}, sparc{,64}, possibly
240  * others), this macro can be used to ensure that the error flag will not get
241  * set.  On architectures which do not support a separate error flag, the macro
242  * is a no-op and the spurious error condition needs to be filtered out by some
243  * other means (e.g., in user-level, by passing an extra argument to the
244  * syscall handler, or something along those lines).
245  */
246 #define force_successful_syscall_return() do { } while (0)
247 #endif
248 
249 #ifndef is_syscall_success
250 /*
251  * On most systems we can tell if a syscall is a success based on if the retval
252  * is an error value.  On some systems like ia64 and powerpc they have different
253  * indicators of success/failure and must define their own.
254  */
255 #define is_syscall_success(regs) (!IS_ERR_VALUE((unsigned long)(regs_return_value(regs))))
256 #endif
257 
258 /*
259  * <asm/ptrace.h> should define the following things inside #ifdef __KERNEL__.
260  *
261  * These do-nothing inlines are used when the arch does not
262  * implement single-step.  The kerneldoc comments are here
263  * to document the interface for all arch definitions.
264  */
265 
266 #ifndef arch_has_single_step
267 /**
268  * arch_has_single_step - does this CPU support user-mode single-step?
269  *
270  * If this is defined, then there must be function declarations or
271  * inlines for user_enable_single_step() and user_disable_single_step().
272  * arch_has_single_step() should evaluate to nonzero iff the machine
273  * supports instruction single-step for user mode.
274  * It can be a constant or it can test a CPU feature bit.
275  */
276 #define arch_has_single_step()		(0)
277 
278 /**
279  * user_enable_single_step - single-step in user-mode task
280  * @task: either current or a task stopped in %TASK_TRACED
281  *
282  * This can only be called when arch_has_single_step() has returned nonzero.
283  * Set @task so that when it returns to user mode, it will trap after the
284  * next single instruction executes.  If arch_has_block_step() is defined,
285  * this must clear the effects of user_enable_block_step() too.
286  */
user_enable_single_step(struct task_struct * task)287 static inline void user_enable_single_step(struct task_struct *task)
288 {
289 	BUG();			/* This can never be called.  */
290 }
291 
292 /**
293  * user_disable_single_step - cancel user-mode single-step
294  * @task: either current or a task stopped in %TASK_TRACED
295  *
296  * Clear @task of the effects of user_enable_single_step() and
297  * user_enable_block_step().  This can be called whether or not either
298  * of those was ever called on @task, and even if arch_has_single_step()
299  * returned zero.
300  */
user_disable_single_step(struct task_struct * task)301 static inline void user_disable_single_step(struct task_struct *task)
302 {
303 }
304 #else
305 extern void user_enable_single_step(struct task_struct *);
306 extern void user_disable_single_step(struct task_struct *);
307 #endif	/* arch_has_single_step */
308 
309 #ifndef arch_has_block_step
310 /**
311  * arch_has_block_step - does this CPU support user-mode block-step?
312  *
313  * If this is defined, then there must be a function declaration or inline
314  * for user_enable_block_step(), and arch_has_single_step() must be defined
315  * too.  arch_has_block_step() should evaluate to nonzero iff the machine
316  * supports step-until-branch for user mode.  It can be a constant or it
317  * can test a CPU feature bit.
318  */
319 #define arch_has_block_step()		(0)
320 
321 /**
322  * user_enable_block_step - step until branch in user-mode task
323  * @task: either current or a task stopped in %TASK_TRACED
324  *
325  * This can only be called when arch_has_block_step() has returned nonzero,
326  * and will never be called when single-instruction stepping is being used.
327  * Set @task so that when it returns to user mode, it will trap after the
328  * next branch or trap taken.
329  */
user_enable_block_step(struct task_struct * task)330 static inline void user_enable_block_step(struct task_struct *task)
331 {
332 	BUG();			/* This can never be called.  */
333 }
334 #else
335 extern void user_enable_block_step(struct task_struct *);
336 #endif	/* arch_has_block_step */
337 
338 #ifdef ARCH_HAS_USER_SINGLE_STEP_REPORT
339 extern void user_single_step_report(struct pt_regs *regs);
340 #else
user_single_step_report(struct pt_regs * regs)341 static inline void user_single_step_report(struct pt_regs *regs)
342 {
343 	kernel_siginfo_t info;
344 	clear_siginfo(&info);
345 	info.si_signo = SIGTRAP;
346 	info.si_errno = 0;
347 	info.si_code = SI_USER;
348 	info.si_pid = 0;
349 	info.si_uid = 0;
350 	force_sig_info(&info);
351 }
352 #endif
353 
354 #ifndef arch_ptrace_stop_needed
355 /**
356  * arch_ptrace_stop_needed - Decide whether arch_ptrace_stop() should be called
357  *
358  * This is called with the siglock held, to decide whether or not it's
359  * necessary to release the siglock and call arch_ptrace_stop().  It can be
360  * defined to a constant if arch_ptrace_stop() is never required, or always
361  * is.  On machines where this makes sense, it should be defined to a quick
362  * test to optimize out calling arch_ptrace_stop() when it would be
363  * superfluous.  For example, if the thread has not been back to user mode
364  * since the last stop, the thread state might indicate that nothing needs
365  * to be done.
366  *
367  * This is guaranteed to be invoked once before a task stops for ptrace and
368  * may include arch-specific operations necessary prior to a ptrace stop.
369  */
370 #define arch_ptrace_stop_needed()	(0)
371 #endif
372 
373 #ifndef arch_ptrace_stop
374 /**
375  * arch_ptrace_stop - Do machine-specific work before stopping for ptrace
376  *
377  * This is called with no locks held when arch_ptrace_stop_needed() has
378  * just returned nonzero.  It is allowed to block, e.g. for user memory
379  * access.  The arch can have machine-specific work to be done before
380  * ptrace stops.  On ia64, register backing store gets written back to user
381  * memory here.  Since this can be costly (requires dropping the siglock),
382  * we only do it when the arch requires it for this particular stop, as
383  * indicated by arch_ptrace_stop_needed().
384  */
385 #define arch_ptrace_stop()		do { } while (0)
386 #endif
387 
388 #ifndef current_pt_regs
389 #define current_pt_regs() task_pt_regs(current)
390 #endif
391 
392 #ifndef current_user_stack_pointer
393 #define current_user_stack_pointer() user_stack_pointer(current_pt_regs())
394 #endif
395 
396 #ifndef exception_ip
397 #define exception_ip(x) instruction_pointer(x)
398 #endif
399 
400 extern int task_current_syscall(struct task_struct *target, struct syscall_info *info);
401 
402 extern void sigaction_compat_abi(struct k_sigaction *act, struct k_sigaction *oact);
403 
404 /*
405  * ptrace report for syscall entry and exit looks identical.
406  */
ptrace_report_syscall(unsigned long message)407 static inline int ptrace_report_syscall(unsigned long message)
408 {
409 	int ptrace = current->ptrace;
410 	int signr;
411 
412 	if (!(ptrace & PT_PTRACED))
413 		return 0;
414 
415 	signr = ptrace_notify(SIGTRAP | ((ptrace & PT_TRACESYSGOOD) ? 0x80 : 0),
416 			      message);
417 
418 	/*
419 	 * this isn't the same as continuing with a signal, but it will do
420 	 * for normal use.  strace only continues with a signal if the
421 	 * stopping signal is not SIGTRAP.  -brl
422 	 */
423 	if (signr)
424 		send_sig(signr, current, 1);
425 
426 	return fatal_signal_pending(current);
427 }
428 
429 /**
430  * ptrace_report_syscall_entry - task is about to attempt a system call
431  * @regs:		user register state of current task
432  *
433  * This will be called if %SYSCALL_WORK_SYSCALL_TRACE or
434  * %SYSCALL_WORK_SYSCALL_EMU have been set, when the current task has just
435  * entered the kernel for a system call.  Full user register state is
436  * available here.  Changing the values in @regs can affect the system
437  * call number and arguments to be tried.  It is safe to block here,
438  * preventing the system call from beginning.
439  *
440  * Returns zero normally, or nonzero if the calling arch code should abort
441  * the system call.  That must prevent normal entry so no system call is
442  * made.  If @task ever returns to user mode after this, its register state
443  * is unspecified, but should be something harmless like an %ENOSYS error
444  * return.  It should preserve enough information so that syscall_rollback()
445  * can work (see asm-generic/syscall.h).
446  *
447  * Called without locks, just after entering kernel mode.
448  */
ptrace_report_syscall_entry(struct pt_regs * regs)449 static inline __must_check int ptrace_report_syscall_entry(
450 	struct pt_regs *regs)
451 {
452 	return ptrace_report_syscall(PTRACE_EVENTMSG_SYSCALL_ENTRY);
453 }
454 
455 /**
456  * ptrace_report_syscall_exit - task has just finished a system call
457  * @regs:		user register state of current task
458  * @step:		nonzero if simulating single-step or block-step
459  *
460  * This will be called if %SYSCALL_WORK_SYSCALL_TRACE has been set, when
461  * the current task has just finished an attempted system call.  Full
462  * user register state is available here.  It is safe to block here,
463  * preventing signals from being processed.
464  *
465  * If @step is nonzero, this report is also in lieu of the normal
466  * trap that would follow the system call instruction because
467  * user_enable_block_step() or user_enable_single_step() was used.
468  * In this case, %SYSCALL_WORK_SYSCALL_TRACE might not be set.
469  *
470  * Called without locks, just before checking for pending signals.
471  */
ptrace_report_syscall_exit(struct pt_regs * regs,int step)472 static inline void ptrace_report_syscall_exit(struct pt_regs *regs, int step)
473 {
474 	if (step)
475 		user_single_step_report(regs);
476 	else
477 		ptrace_report_syscall(PTRACE_EVENTMSG_SYSCALL_EXIT);
478 }
479 #endif
480