1/* 2 * Tracing hooks 3 * 4 * Copyright (C) 2008-2009 Red Hat, Inc. All rights reserved. 5 * 6 * This copyrighted material is made available to anyone wishing to use, 7 * modify, copy, or redistribute it subject to the terms and conditions 8 * of the GNU General Public License v.2. 9 * 10 * This file defines hook entry points called by core code where 11 * user tracing/debugging support might need to do something. These 12 * entry points are called tracehook_*(). Each hook declared below 13 * has a detailed kerneldoc comment giving the context (locking et 14 * al) from which it is called, and the meaning of its return value. 15 * 16 * Each function here typically has only one call site, so it is ok 17 * to have some nontrivial tracehook_*() inlines. In all cases, the 18 * fast path when no tracing is enabled should be very short. 19 * 20 * The purpose of this file and the tracehook_* layer is to consolidate 21 * the interface that the kernel core and arch code uses to enable any 22 * user debugging or tracing facility (such as ptrace). The interfaces 23 * here are carefully documented so that maintainers of core and arch 24 * code do not need to think about the implementation details of the 25 * tracing facilities. Likewise, maintainers of the tracing code do not 26 * need to understand all the calling core or arch code in detail, just 27 * documented circumstances of each call, such as locking conditions. 28 * 29 * If the calling core code changes so that locking is different, then 30 * it is ok to change the interface documented here. The maintainer of 31 * core code changing should notify the maintainers of the tracing code 32 * that they need to work out the change. 33 * 34 * Some tracehook_*() inlines take arguments that the current tracing 35 * implementations might not necessarily use. These function signatures 36 * are chosen to pass in all the information that is on hand in the 37 * caller and might conceivably be relevant to a tracer, so that the 38 * core code won't have to be updated when tracing adds more features. 39 * If a call site changes so that some of those parameters are no longer 40 * already on hand without extra work, then the tracehook_* interface 41 * can change so there is no make-work burden on the core code. The 42 * maintainer of core code changing should notify the maintainers of the 43 * tracing code that they need to work out the change. 44 */ 45 46#ifndef _LINUX_TRACEHOOK_H 47#define _LINUX_TRACEHOOK_H 1 48 49#include <linux/sched.h> 50#include <linux/ptrace.h> 51#include <linux/security.h> 52struct linux_binprm; 53 54/** 55 * tracehook_expect_breakpoints - guess if task memory might be touched 56 * @task: current task, making a new mapping 57 * 58 * Return nonzero if @task is expected to want breakpoint insertion in 59 * its memory at some point. A zero return is no guarantee it won't 60 * be done, but this is a hint that it's known to be likely. 61 * 62 * May be called with @task->mm->mmap_sem held for writing. 63 */ 64static inline int tracehook_expect_breakpoints(struct task_struct *task) 65{ 66 return (task_ptrace(task) & PT_PTRACED) != 0; 67} 68 69/* 70 * ptrace report for syscall entry and exit looks identical. 71 */ 72static inline void ptrace_report_syscall(struct pt_regs *regs) 73{ 74 int ptrace = task_ptrace(current); 75 76 if (!(ptrace & PT_PTRACED)) 77 return; 78 79 ptrace_notify(SIGTRAP | ((ptrace & PT_TRACESYSGOOD) ? 0x80 : 0)); 80 81 /* 82 * this isn't the same as continuing with a signal, but it will do 83 * for normal use. strace only continues with a signal if the 84 * stopping signal is not SIGTRAP. -brl 85 */ 86 if (current->exit_code) { 87 send_sig(current->exit_code, current, 1); 88 current->exit_code = 0; 89 } 90} 91 92/** 93 * tracehook_report_syscall_entry - task is about to attempt a system call 94 * @regs: user register state of current task 95 * 96 * This will be called if %TIF_SYSCALL_TRACE has been set, when the 97 * current task has just entered the kernel for a system call. 98 * Full user register state is available here. Changing the values 99 * in @regs can affect the system call number and arguments to be tried. 100 * It is safe to block here, preventing the system call from beginning. 101 * 102 * Returns zero normally, or nonzero if the calling arch code should abort 103 * the system call. That must prevent normal entry so no system call is 104 * made. If @task ever returns to user mode after this, its register state 105 * is unspecified, but should be something harmless like an %ENOSYS error 106 * return. It should preserve enough information so that syscall_rollback() 107 * can work (see asm-generic/syscall.h). 108 * 109 * Called without locks, just after entering kernel mode. 110 */ 111static inline __must_check int tracehook_report_syscall_entry( 112 struct pt_regs *regs) 113{ 114 ptrace_report_syscall(regs); 115 return 0; 116} 117 118/** 119 * tracehook_report_syscall_exit - task has just finished a system call 120 * @regs: user register state of current task 121 * @step: nonzero if simulating single-step or block-step 122 * 123 * This will be called if %TIF_SYSCALL_TRACE has been set, when the 124 * current task has just finished an attempted system call. Full 125 * user register state is available here. It is safe to block here, 126 * preventing signals from being processed. 127 * 128 * If @step is nonzero, this report is also in lieu of the normal 129 * trap that would follow the system call instruction because 130 * user_enable_block_step() or user_enable_single_step() was used. 131 * In this case, %TIF_SYSCALL_TRACE might not be set. 132 * 133 * Called without locks, just before checking for pending signals. 134 */ 135static inline void tracehook_report_syscall_exit(struct pt_regs *regs, int step) 136{ 137 if (step) { 138 siginfo_t info; 139 user_single_step_siginfo(current, regs, &info); 140 force_sig_info(SIGTRAP, &info, current); 141 return; 142 } 143 144 ptrace_report_syscall(regs); 145} 146 147/** 148 * tracehook_unsafe_exec - check for exec declared unsafe due to tracing 149 * @task: current task doing exec 150 * 151 * Return %LSM_UNSAFE_* bits applied to an exec because of tracing. 152 * 153 * @task->cred_guard_mutex is held by the caller through the do_execve(). 154 */ 155static inline int tracehook_unsafe_exec(struct task_struct *task) 156{ 157 int unsafe = 0; 158 int ptrace = task_ptrace(task); 159 if (ptrace & PT_PTRACED) { 160 if (ptrace & PT_PTRACE_CAP) 161 unsafe |= LSM_UNSAFE_PTRACE_CAP; 162 else 163 unsafe |= LSM_UNSAFE_PTRACE; 164 } 165 return unsafe; 166} 167 168/** 169 * tracehook_tracer_task - return the task that is tracing the given task 170 * @tsk: task to consider 171 * 172 * Returns NULL if noone is tracing @task, or the &struct task_struct 173 * pointer to its tracer. 174 * 175 * Must called under rcu_read_lock(). The pointer returned might be kept 176 * live only by RCU. During exec, this may be called with task_lock() 177 * held on @task, still held from when tracehook_unsafe_exec() was called. 178 */ 179static inline struct task_struct *tracehook_tracer_task(struct task_struct *tsk) 180{ 181 if (task_ptrace(tsk) & PT_PTRACED) 182 return rcu_dereference(tsk->parent); 183 return NULL; 184} 185 186/** 187 * tracehook_report_exec - a successful exec was completed 188 * @fmt: &struct linux_binfmt that performed the exec 189 * @bprm: &struct linux_binprm containing exec details 190 * @regs: user-mode register state 191 * 192 * An exec just completed, we are shortly going to return to user mode. 193 * The freshly initialized register state can be seen and changed in @regs. 194 * The name, file and other pointers in @bprm are still on hand to be 195 * inspected, but will be freed as soon as this returns. 196 * 197 * Called with no locks, but with some kernel resources held live 198 * and a reference on @fmt->module. 199 */ 200static inline void tracehook_report_exec(struct linux_binfmt *fmt, 201 struct linux_binprm *bprm, 202 struct pt_regs *regs) 203{ 204 if (!ptrace_event(PT_TRACE_EXEC, PTRACE_EVENT_EXEC, 0) && 205 unlikely(task_ptrace(current) & PT_PTRACED)) 206 send_sig(SIGTRAP, current, 0); 207} 208 209/** 210 * tracehook_report_exit - task has begun to exit 211 * @exit_code: pointer to value destined for @current->exit_code 212 * 213 * @exit_code points to the value passed to do_exit(), which tracing 214 * might change here. This is almost the first thing in do_exit(), 215 * before freeing any resources or setting the %PF_EXITING flag. 216 * 217 * Called with no locks held. 218 */ 219static inline void tracehook_report_exit(long *exit_code) 220{ 221 ptrace_event(PT_TRACE_EXIT, PTRACE_EVENT_EXIT, *exit_code); 222} 223 224/** 225 * tracehook_prepare_clone - prepare for new child to be cloned 226 * @clone_flags: %CLONE_* flags from clone/fork/vfork system call 227 * 228 * This is called before a new user task is to be cloned. 229 * Its return value will be passed to tracehook_finish_clone(). 230 * 231 * Called with no locks held. 232 */ 233static inline int tracehook_prepare_clone(unsigned clone_flags) 234{ 235 if (clone_flags & CLONE_UNTRACED) 236 return 0; 237 238 if (clone_flags & CLONE_VFORK) { 239 if (current->ptrace & PT_TRACE_VFORK) 240 return PTRACE_EVENT_VFORK; 241 } else if ((clone_flags & CSIGNAL) != SIGCHLD) { 242 if (current->ptrace & PT_TRACE_CLONE) 243 return PTRACE_EVENT_CLONE; 244 } else if (current->ptrace & PT_TRACE_FORK) 245 return PTRACE_EVENT_FORK; 246 247 return 0; 248} 249 250/** 251 * tracehook_finish_clone - new child created and being attached 252 * @child: new child task 253 * @clone_flags: %CLONE_* flags from clone/fork/vfork system call 254 * @trace: return value from tracehook_prepare_clone() 255 * 256 * This is called immediately after adding @child to its parent's children list. 257 * The @trace value is that returned by tracehook_prepare_clone(). 258 * 259 * Called with current's siglock and write_lock_irq(&tasklist_lock) held. 260 */ 261static inline void tracehook_finish_clone(struct task_struct *child, 262 unsigned long clone_flags, int trace) 263{ 264 ptrace_init_task(child, (clone_flags & CLONE_PTRACE) || trace); 265} 266 267/** 268 * tracehook_report_clone - in parent, new child is about to start running 269 * @regs: parent's user register state 270 * @clone_flags: flags from parent's system call 271 * @pid: new child's PID in the parent's namespace 272 * @child: new child task 273 * 274 * Called after a child is set up, but before it has been started running. 275 * This is not a good place to block, because the child has not started 276 * yet. Suspend the child here if desired, and then block in 277 * tracehook_report_clone_complete(). This must prevent the child from 278 * self-reaping if tracehook_report_clone_complete() uses the @child 279 * pointer; otherwise it might have died and been released by the time 280 * tracehook_report_clone_complete() is called. 281 * 282 * Called with no locks held, but the child cannot run until this returns. 283 */ 284static inline void tracehook_report_clone(struct pt_regs *regs, 285 unsigned long clone_flags, 286 pid_t pid, struct task_struct *child) 287{ 288 if (unlikely(task_ptrace(child))) { 289 /* 290 * It doesn't matter who attached/attaching to this 291 * task, the pending SIGSTOP is right in any case. 292 */ 293 sigaddset(&child->pending.signal, SIGSTOP); 294 set_tsk_thread_flag(child, TIF_SIGPENDING); 295 } 296} 297 298/** 299 * tracehook_report_clone_complete - new child is running 300 * @trace: return value from tracehook_prepare_clone() 301 * @regs: parent's user register state 302 * @clone_flags: flags from parent's system call 303 * @pid: new child's PID in the parent's namespace 304 * @child: child task, already running 305 * 306 * This is called just after the child has started running. This is 307 * just before the clone/fork syscall returns, or blocks for vfork 308 * child completion if @clone_flags has the %CLONE_VFORK bit set. 309 * The @child pointer may be invalid if a self-reaping child died and 310 * tracehook_report_clone() took no action to prevent it from self-reaping. 311 * 312 * Called with no locks held. 313 */ 314static inline void tracehook_report_clone_complete(int trace, 315 struct pt_regs *regs, 316 unsigned long clone_flags, 317 pid_t pid, 318 struct task_struct *child) 319{ 320 if (unlikely(trace)) 321 ptrace_event(0, trace, pid); 322} 323 324/** 325 * tracehook_report_vfork_done - vfork parent's child has exited or exec'd 326 * @child: child task, already running 327 * @pid: new child's PID in the parent's namespace 328 * 329 * Called after a %CLONE_VFORK parent has waited for the child to complete. 330 * The clone/vfork system call will return immediately after this. 331 * The @child pointer may be invalid if a self-reaping child died and 332 * tracehook_report_clone() took no action to prevent it from self-reaping. 333 * 334 * Called with no locks held. 335 */ 336static inline void tracehook_report_vfork_done(struct task_struct *child, 337 pid_t pid) 338{ 339 ptrace_event(PT_TRACE_VFORK_DONE, PTRACE_EVENT_VFORK_DONE, pid); 340} 341 342/** 343 * tracehook_prepare_release_task - task is being reaped, clean up tracing 344 * @task: task in %EXIT_DEAD state 345 * 346 * This is called in release_task() just before @task gets finally reaped 347 * and freed. This would be the ideal place to remove and clean up any 348 * tracing-related state for @task. 349 * 350 * Called with no locks held. 351 */ 352static inline void tracehook_prepare_release_task(struct task_struct *task) 353{ 354} 355 356/** 357 * tracehook_finish_release_task - final tracing clean-up 358 * @task: task in %EXIT_DEAD state 359 * 360 * This is called in release_task() when @task is being in the middle of 361 * being reaped. After this, there must be no tracing entanglements. 362 * 363 * Called with write_lock_irq(&tasklist_lock) held. 364 */ 365static inline void tracehook_finish_release_task(struct task_struct *task) 366{ 367 ptrace_release_task(task); 368} 369 370/** 371 * tracehook_signal_handler - signal handler setup is complete 372 * @sig: number of signal being delivered 373 * @info: siginfo_t of signal being delivered 374 * @ka: sigaction setting that chose the handler 375 * @regs: user register state 376 * @stepping: nonzero if debugger single-step or block-step in use 377 * 378 * Called by the arch code after a signal handler has been set up. 379 * Register and stack state reflects the user handler about to run. 380 * Signal mask changes have already been made. 381 * 382 * Called without locks, shortly before returning to user mode 383 * (or handling more signals). 384 */ 385static inline void tracehook_signal_handler(int sig, siginfo_t *info, 386 const struct k_sigaction *ka, 387 struct pt_regs *regs, int stepping) 388{ 389 if (stepping) 390 ptrace_notify(SIGTRAP); 391} 392 393/** 394 * tracehook_consider_ignored_signal - suppress short-circuit of ignored signal 395 * @task: task receiving the signal 396 * @sig: signal number being sent 397 * 398 * Return zero iff tracing doesn't care to examine this ignored signal, 399 * so it can short-circuit normal delivery and never even get queued. 400 * 401 * Called with @task->sighand->siglock held. 402 */ 403static inline int tracehook_consider_ignored_signal(struct task_struct *task, 404 int sig) 405{ 406 return (task_ptrace(task) & PT_PTRACED) != 0; 407} 408 409/** 410 * tracehook_consider_fatal_signal - suppress special handling of fatal signal 411 * @task: task receiving the signal 412 * @sig: signal number being sent 413 * 414 * Return nonzero to prevent special handling of this termination signal. 415 * Normally handler for signal is %SIG_DFL. It can be %SIG_IGN if @sig is 416 * ignored, in which case force_sig() is about to reset it to %SIG_DFL. 417 * When this returns zero, this signal might cause a quick termination 418 * that does not give the debugger a chance to intercept the signal. 419 * 420 * Called with or without @task->sighand->siglock held. 421 */ 422static inline int tracehook_consider_fatal_signal(struct task_struct *task, 423 int sig) 424{ 425 return (task_ptrace(task) & PT_PTRACED) != 0; 426} 427 428/** 429 * tracehook_force_sigpending - let tracing force signal_pending(current) on 430 * 431 * Called when recomputing our signal_pending() flag. Return nonzero 432 * to force the signal_pending() flag on, so that tracehook_get_signal() 433 * will be called before the next return to user mode. 434 * 435 * Called with @current->sighand->siglock held. 436 */ 437static inline int tracehook_force_sigpending(void) 438{ 439 return 0; 440} 441 442/** 443 * tracehook_get_signal - deliver synthetic signal to traced task 444 * @task: @current 445 * @regs: task_pt_regs(@current) 446 * @info: details of synthetic signal 447 * @return_ka: sigaction for synthetic signal 448 * 449 * Return zero to check for a real pending signal normally. 450 * Return -1 after releasing the siglock to repeat the check. 451 * Return a signal number to induce an artifical signal delivery, 452 * setting *@info and *@return_ka to specify its details and behavior. 453 * 454 * The @return_ka->sa_handler value controls the disposition of the 455 * signal, no matter the signal number. For %SIG_DFL, the return value 456 * is a representative signal to indicate the behavior (e.g. %SIGTERM 457 * for death, %SIGQUIT for core dump, %SIGSTOP for job control stop, 458 * %SIGTSTP for stop unless in an orphaned pgrp), but the signal number 459 * reported will be @info->si_signo instead. 460 * 461 * Called with @task->sighand->siglock held, before dequeuing pending signals. 462 */ 463static inline int tracehook_get_signal(struct task_struct *task, 464 struct pt_regs *regs, 465 siginfo_t *info, 466 struct k_sigaction *return_ka) 467{ 468 return 0; 469} 470 471/** 472 * tracehook_notify_jctl - report about job control stop/continue 473 * @notify: zero, %CLD_STOPPED or %CLD_CONTINUED 474 * @why: %CLD_STOPPED or %CLD_CONTINUED 475 * 476 * This is called when we might call do_notify_parent_cldstop(). 477 * 478 * @notify is zero if we would not ordinarily send a %SIGCHLD, 479 * or is the %CLD_STOPPED or %CLD_CONTINUED .si_code for %SIGCHLD. 480 * 481 * @why is %CLD_STOPPED when about to stop for job control; 482 * we are already in %TASK_STOPPED state, about to call schedule(). 483 * It might also be that we have just exited (check %PF_EXITING), 484 * but need to report that a group-wide stop is complete. 485 * 486 * @why is %CLD_CONTINUED when waking up after job control stop and 487 * ready to make a delayed @notify report. 488 * 489 * Return the %CLD_* value for %SIGCHLD, or zero to generate no signal. 490 * 491 * Called with the siglock held. 492 */ 493static inline int tracehook_notify_jctl(int notify, int why) 494{ 495 return notify ?: (current->ptrace & PT_PTRACED) ? why : 0; 496} 497 498/** 499 * tracehook_finish_jctl - report about return from job control stop 500 * 501 * This is called by do_signal_stop() after wakeup. 502 */ 503static inline void tracehook_finish_jctl(void) 504{ 505} 506 507#define DEATH_REAP -1 508#define DEATH_DELAYED_GROUP_LEADER -2 509 510/** 511 * tracehook_notify_death - task is dead, ready to notify parent 512 * @task: @current task now exiting 513 * @death_cookie: value to pass to tracehook_report_death() 514 * @group_dead: nonzero if this was the last thread in the group to die 515 * 516 * A return value >= 0 means call do_notify_parent() with that signal 517 * number. Negative return value can be %DEATH_REAP to self-reap right 518 * now, or %DEATH_DELAYED_GROUP_LEADER to a zombie without notifying our 519 * parent. Note that a return value of 0 means a do_notify_parent() call 520 * that sends no signal, but still wakes up a parent blocked in wait*(). 521 * 522 * Called with write_lock_irq(&tasklist_lock) held. 523 */ 524static inline int tracehook_notify_death(struct task_struct *task, 525 void **death_cookie, int group_dead) 526{ 527 if (task_detached(task)) 528 return task->ptrace ? SIGCHLD : DEATH_REAP; 529 530 /* 531 * If something other than our normal parent is ptracing us, then 532 * send it a SIGCHLD instead of honoring exit_signal. exit_signal 533 * only has special meaning to our real parent. 534 */ 535 if (thread_group_empty(task) && !ptrace_reparented(task)) 536 return task->exit_signal; 537 538 return task->ptrace ? SIGCHLD : DEATH_DELAYED_GROUP_LEADER; 539} 540 541/** 542 * tracehook_report_death - task is dead and ready to be reaped 543 * @task: @current task now exiting 544 * @signal: return value from tracheook_notify_death() 545 * @death_cookie: value passed back from tracehook_notify_death() 546 * @group_dead: nonzero if this was the last thread in the group to die 547 * 548 * Thread has just become a zombie or is about to self-reap. If positive, 549 * @signal is the signal number just sent to the parent (usually %SIGCHLD). 550 * If @signal is %DEATH_REAP, this thread will self-reap. If @signal is 551 * %DEATH_DELAYED_GROUP_LEADER, this is a delayed_group_leader() zombie. 552 * The @death_cookie was passed back by tracehook_notify_death(). 553 * 554 * If normal reaping is not inhibited, @task->exit_state might be changing 555 * in parallel. 556 * 557 * Called without locks. 558 */ 559static inline void tracehook_report_death(struct task_struct *task, 560 int signal, void *death_cookie, 561 int group_dead) 562{ 563} 564 565#ifdef TIF_NOTIFY_RESUME 566/** 567 * set_notify_resume - cause tracehook_notify_resume() to be called 568 * @task: task that will call tracehook_notify_resume() 569 * 570 * Calling this arranges that @task will call tracehook_notify_resume() 571 * before returning to user mode. If it's already running in user mode, 572 * it will enter the kernel and call tracehook_notify_resume() soon. 573 * If it's blocked, it will not be woken. 574 */ 575static inline void set_notify_resume(struct task_struct *task) 576{ 577 if (!test_and_set_tsk_thread_flag(task, TIF_NOTIFY_RESUME)) 578 kick_process(task); 579} 580 581/** 582 * tracehook_notify_resume - report when about to return to user mode 583 * @regs: user-mode registers of @current task 584 * 585 * This is called when %TIF_NOTIFY_RESUME has been set. Now we are 586 * about to return to user mode, and the user state in @regs can be 587 * inspected or adjusted. The caller in arch code has cleared 588 * %TIF_NOTIFY_RESUME before the call. If the flag gets set again 589 * asynchronously, this will be called again before we return to 590 * user mode. 591 * 592 * Called without locks. 593 */ 594static inline void tracehook_notify_resume(struct pt_regs *regs) 595{ 596} 597#endif /* TIF_NOTIFY_RESUME */ 598 599#endif /* <linux/tracehook.h> */ 600