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Diffstat (limited to 'include/linux/tracehook.h')
| -rw-r--r-- | include/linux/tracehook.h | 582 |
1 files changed, 582 insertions, 0 deletions
diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h new file mode 100644 index 00000000000..6186a789d6c --- /dev/null +++ b/include/linux/tracehook.h @@ -0,0 +1,582 @@ +/* + * Tracing hooks + * + * Copyright (C) 2008 Red Hat, Inc. All rights reserved. + * + * This copyrighted material is made available to anyone wishing to use, + * modify, copy, or redistribute it subject to the terms and conditions + * of the GNU General Public License v.2. + * + * This file defines hook entry points called by core code where + * user tracing/debugging support might need to do something. These + * entry points are called tracehook_*(). Each hook declared below + * has a detailed kerneldoc comment giving the context (locking et + * al) from which it is called, and the meaning of its return value. + * + * Each function here typically has only one call site, so it is ok + * to have some nontrivial tracehook_*() inlines. In all cases, the + * fast path when no tracing is enabled should be very short. + * + * The purpose of this file and the tracehook_* layer is to consolidate + * the interface that the kernel core and arch code uses to enable any + * user debugging or tracing facility (such as ptrace). The interfaces + * here are carefully documented so that maintainers of core and arch + * code do not need to think about the implementation details of the + * tracing facilities. Likewise, maintainers of the tracing code do not + * need to understand all the calling core or arch code in detail, just + * documented circumstances of each call, such as locking conditions. + * + * If the calling core code changes so that locking is different, then + * it is ok to change the interface documented here. The maintainer of + * core code changing should notify the maintainers of the tracing code + * that they need to work out the change. + * + * Some tracehook_*() inlines take arguments that the current tracing + * implementations might not necessarily use. These function signatures + * are chosen to pass in all the information that is on hand in the + * caller and might conceivably be relevant to a tracer, so that the + * core code won't have to be updated when tracing adds more features. + * If a call site changes so that some of those parameters are no longer + * already on hand without extra work, then the tracehook_* interface + * can change so there is no make-work burden on the core code. The + * maintainer of core code changing should notify the maintainers of the + * tracing code that they need to work out the change. + */ + +#ifndef _LINUX_TRACEHOOK_H +#define _LINUX_TRACEHOOK_H 1 + +#include <linux/sched.h> +#include <linux/ptrace.h> +#include <linux/security.h> +struct linux_binprm; + +/** + * tracehook_expect_breakpoints - guess if task memory might be touched + * @task: current task, making a new mapping + * + * Return nonzero if @task is expected to want breakpoint insertion in + * its memory at some point. A zero return is no guarantee it won't + * be done, but this is a hint that it's known to be likely. + * + * May be called with @task->mm->mmap_sem held for writing. + */ +static inline int tracehook_expect_breakpoints(struct task_struct *task) +{ + return (task_ptrace(task) & PT_PTRACED) != 0; +} + +/* + * ptrace report for syscall entry and exit looks identical. + */ +static inline void ptrace_report_syscall(struct pt_regs *regs) +{ + int ptrace = task_ptrace(current); + + if (!(ptrace & PT_PTRACED)) + return; + + ptrace_notify(SIGTRAP | ((ptrace & PT_TRACESYSGOOD) ? 0x80 : 0)); + + /* + * this isn't the same as continuing with a signal, but it will do + * for normal use. strace only continues with a signal if the + * stopping signal is not SIGTRAP. -brl + */ + if (current->exit_code) { + send_sig(current->exit_code, current, 1); + current->exit_code = 0; + } +} + +/** + * tracehook_report_syscall_entry - task is about to attempt a system call + * @regs: user register state of current task + * + * This will be called if %TIF_SYSCALL_TRACE has been set, when the + * current task has just entered the kernel for a system call. + * Full user register state is available here. Changing the values + * in @regs can affect the system call number and arguments to be tried. + * It is safe to block here, preventing the system call from beginning. + * + * Returns zero normally, or nonzero if the calling arch code should abort + * the system call. That must prevent normal entry so no system call is + * made. If @task ever returns to user mode after this, its register state + * is unspecified, but should be something harmless like an %ENOSYS error + * return. It should preserve enough information so that syscall_rollback() + * can work (see asm-generic/syscall.h). + * + * Called without locks, just after entering kernel mode. + */ +static inline __must_check int tracehook_report_syscall_entry( + struct pt_regs *regs) +{ + ptrace_report_syscall(regs); + return 0; +} + +/** + * tracehook_report_syscall_exit - task has just finished a system call + * @regs: user register state of current task + * @step: nonzero if simulating single-step or block-step + * + * This will be called if %TIF_SYSCALL_TRACE has been set, when the + * current task has just finished an attempted system call. Full + * user register state is available here. It is safe to block here, + * preventing signals from being processed. + * + * If @step is nonzero, this report is also in lieu of the normal + * trap that would follow the system call instruction because + * user_enable_block_step() or user_enable_single_step() was used. + * In this case, %TIF_SYSCALL_TRACE might not be set. + * + * Called without locks, just before checking for pending signals. + */ +static inline void tracehook_report_syscall_exit(struct pt_regs *regs, int step) +{ + ptrace_report_syscall(regs); +} + +/** + * tracehook_unsafe_exec - check for exec declared unsafe due to tracing + * @task: current task doing exec + * + * Return %LSM_UNSAFE_* bits applied to an exec because of tracing. + * + * Called with task_lock() held on @task. + */ +static inline int tracehook_unsafe_exec(struct task_struct *task) +{ + int unsafe = 0; + int ptrace = task_ptrace(task); + if (ptrace & PT_PTRACED) { + if (ptrace & PT_PTRACE_CAP) + unsafe |= LSM_UNSAFE_PTRACE_CAP; + else + unsafe |= LSM_UNSAFE_PTRACE; + } + return unsafe; +} + +/** + * tracehook_tracer_task - return the task that is tracing the given task + * @tsk: task to consider + * + * Returns NULL if noone is tracing @task, or the &struct task_struct + * pointer to its tracer. + * + * Must called under rcu_read_lock(). The pointer returned might be kept + * live only by RCU. During exec, this may be called with task_lock() + * held on @task, still held from when tracehook_unsafe_exec() was called. + */ +static inline struct task_struct *tracehook_tracer_task(struct task_struct *tsk) +{ + if (task_ptrace(tsk) & PT_PTRACED) + return rcu_dereference(tsk->parent); + return NULL; +} + +/** + * tracehook_report_exec - a successful exec was completed + * @fmt: &struct linux_binfmt that performed the exec + * @bprm: &struct linux_binprm containing exec details + * @regs: user-mode register state + * + * An exec just completed, we are shortly going to return to user mode. + * The freshly initialized register state can be seen and changed in @regs. + * The name, file and other pointers in @bprm are still on hand to be + * inspected, but will be freed as soon as this returns. + * + * Called with no locks, but with some kernel resources held live + * and a reference on @fmt->module. + */ +static inline void tracehook_report_exec(struct linux_binfmt *fmt, + struct linux_binprm *bprm, + struct pt_regs *regs) +{ + if (!ptrace_event(PT_TRACE_EXEC, PTRACE_EVENT_EXEC, 0) && + unlikely(task_ptrace(current) & PT_PTRACED)) + send_sig(SIGTRAP, current, 0); +} + +/** + * tracehook_report_exit - task has begun to exit + * @exit_code: pointer to value destined for @current->exit_code + * + * @exit_code points to the value passed to do_exit(), which tracing + * might change here. This is almost the first thing in do_exit(), + * before freeing any resources or setting the %PF_EXITING flag. + * + * Called with no locks held. + */ +static inline void tracehook_report_exit(long *exit_code) +{ + ptrace_event(PT_TRACE_EXIT, PTRACE_EVENT_EXIT, *exit_code); +} + +/** + * tracehook_prepare_clone - prepare for new child to be cloned + * @clone_flags: %CLONE_* flags from clone/fork/vfork system call + * + * This is called before a new user task is to be cloned. + * Its return value will be passed to tracehook_finish_clone(). + * + * Called with no locks held. + */ +static inline int tracehook_prepare_clone(unsigned clone_flags) +{ + if (clone_flags & CLONE_UNTRACED) + return 0; + + if (clone_flags & CLONE_VFORK) { + if (current->ptrace & PT_TRACE_VFORK) + return PTRACE_EVENT_VFORK; + } else if ((clone_flags & CSIGNAL) != SIGCHLD) { + if (current->ptrace & PT_TRACE_CLONE) + return PTRACE_EVENT_CLONE; + } else if (current->ptrace & PT_TRACE_FORK) + return PTRACE_EVENT_FORK; + + return 0; +} + +/** + * tracehook_finish_clone - new child created and being attached + * @child: new child task + * @clone_flags: %CLONE_* flags from clone/fork/vfork system call + * @trace: return value from tracehook_prepare_clone() + * + * This is called immediately after adding @child to its parent's children list. + * The @trace value is that returned by tracehook_prepare_clone(). + * + * Called with current's siglock and write_lock_irq(&tasklist_lock) held. + */ +static inline void tracehook_finish_clone(struct task_struct *child, + unsigned long clone_flags, int trace) +{ + ptrace_init_task(child, (clone_flags & CLONE_PTRACE) || trace); +} + +/** + * tracehook_report_clone - in parent, new child is about to start running + * @trace: return value from tracehook_prepare_clone() + * @regs: parent's user register state + * @clone_flags: flags from parent's system call + * @pid: new child's PID in the parent's namespace + * @child: new child task + * + * Called after a child is set up, but before it has been started + * running. @trace is the value returned by tracehook_prepare_clone(). + * This is not a good place to block, because the child has not started + * yet. Suspend the child here if desired, and then block in + * tracehook_report_clone_complete(). This must prevent the child from + * self-reaping if tracehook_report_clone_complete() uses the @child + * pointer; otherwise it might have died and been released by the time + * tracehook_report_clone_complete() is called. + * + * Called with no locks held, but the child cannot run until this returns. + */ +static inline void tracehook_report_clone(int trace, struct pt_regs *regs, + unsigned long clone_flags, + pid_t pid, struct task_struct *child) +{ + if (unlikely(trace) || unlikely(clone_flags & CLONE_PTRACE)) { + /* + * The child starts up with an immediate SIGSTOP. + */ + sigaddset(&child->pending.signal, SIGSTOP); + set_tsk_thread_flag(child, TIF_SIGPENDING); + } +} + +/** + * tracehook_report_clone_complete - new child is running + * @trace: return value from tracehook_prepare_clone() + * @regs: parent's user register state + * @clone_flags: flags from parent's system call + * @pid: new child's PID in the parent's namespace + * @child: child task, already running + * + * This is called just after the child has started running. This is + * just before the clone/fork syscall returns, or blocks for vfork + * child completion if @clone_flags has the %CLONE_VFORK bit set. + * The @child pointer may be invalid if a self-reaping child died and + * tracehook_report_clone() took no action to prevent it from self-reaping. + * + * Called with no locks held. + */ +static inline void tracehook_report_clone_complete(int trace, + struct pt_regs *regs, + unsigned long clone_flags, + pid_t pid, + struct task_struct *child) +{ + if (unlikely(trace)) + ptrace_event(0, trace, pid); +} + +/** + * tracehook_report_vfork_done - vfork parent's child has exited or exec'd + * @child: child task, already running + * @pid: new child's PID in the parent's namespace + * + * Called after a %CLONE_VFORK parent has waited for the child to complete. + * The clone/vfork system call will return immediately after this. + * The @child pointer may be invalid if a self-reaping child died and + * tracehook_report_clone() took no action to prevent it from self-reaping. + * + * Called with no locks held. + */ +static inline void tracehook_report_vfork_done(struct task_struct *child, + pid_t pid) +{ + ptrace_event(PT_TRACE_VFORK_DONE, PTRACE_EVENT_VFORK_DONE, pid); +} + +/** + * tracehook_prepare_release_task - task is being reaped, clean up tracing + * @task: task in %EXIT_DEAD state + * + * This is called in release_task() just before @task gets finally reaped + * and freed. This would be the ideal place to remove and clean up any + * tracing-related state for @task. + * + * Called with no locks held. + */ +static inline void tracehook_prepare_release_task(struct task_struct *task) +{ +} + +/** + * tracehook_finish_release_task - final tracing clean-up + * @task: task in %EXIT_DEAD state + * + * This is called in release_task() when @task is being in the middle of + * being reaped. After this, there must be no tracing entanglements. + * + * Called with write_lock_irq(&tasklist_lock) held. + */ +static inline void tracehook_finish_release_task(struct task_struct *task) +{ + ptrace_release_task(task); +} + +/** + * tracehook_signal_handler - signal handler setup is complete + * @sig: number of signal being delivered + * @info: siginfo_t of signal being delivered + * @ka: sigaction setting that chose the handler + * @regs: user register state + * @stepping: nonzero if debugger single-step or block-step in use + * + * Called by the arch code after a signal handler has been set up. + * Register and stack state reflects the user handler about to run. + * Signal mask changes have already been made. + * + * Called without locks, shortly before returning to user mode + * (or handling more signals). + */ +static inline void tracehook_signal_handler(int sig, siginfo_t *info, + const struct k_sigaction *ka, + struct pt_regs *regs, int stepping) +{ + if (stepping) + ptrace_notify(SIGTRAP); +} + +/** + * tracehook_consider_ignored_signal - suppress short-circuit of ignored signal + * @task: task receiving the signal + * @sig: signal number being sent + * @handler: %SIG_IGN or %SIG_DFL + * + * Return zero iff tracing doesn't care to examine this ignored signal, + * so it can short-circuit normal delivery and never even get queued. + * Either @handler is %SIG_DFL and @sig's default is ignore, or it's %SIG_IGN. + * + * Called with @task->sighand->siglock held. + */ +static inline int tracehook_consider_ignored_signal(struct task_struct *task, + int sig, + void __user *handler) +{ + return (task_ptrace(task) & PT_PTRACED) != 0; +} + +/** + * tracehook_consider_fatal_signal - suppress special handling of fatal signal + * @task: task receiving the signal + * @sig: signal number being sent + * @handler: %SIG_DFL or %SIG_IGN + * + * Return nonzero to prevent special handling of this termination signal. + * Normally @handler is %SIG_DFL. It can be %SIG_IGN if @sig is ignored, + * in which case force_sig() is about to reset it to %SIG_DFL. + * When this returns zero, this signal might cause a quick termination + * that does not give the debugger a chance to intercept the signal. + * + * Called with or without @task->sighand->siglock held. + */ +static inline int tracehook_consider_fatal_signal(struct task_struct *task, + int sig, + void __user *handler) +{ + return (task_ptrace(task) & PT_PTRACED) != 0; +} + +/** + * tracehook_force_sigpending - let tracing force signal_pending(current) on + * + * Called when recomputing our signal_pending() flag. Return nonzero + * to force the signal_pending() flag on, so that tracehook_get_signal() + * will be called before the next return to user mode. + * + * Called with @current->sighand->siglock held. + */ +static inline int tracehook_force_sigpending(void) +{ + return 0; +} + +/** + * tracehook_get_signal - deliver synthetic signal to traced task + * @task: @current + * @regs: task_pt_regs(@current) + * @info: details of synthetic signal + * @return_ka: sigaction for synthetic signal + * + * Return zero to check for a real pending signal normally. + * Return -1 after releasing the siglock to repeat the check. + * Return a signal number to induce an artifical signal delivery, + * setting *@info and *@return_ka to specify its details and behavior. + * + * The @return_ka->sa_handler value controls the disposition of the + * signal, no matter the signal number. For %SIG_DFL, the return value + * is a representative signal to indicate the behavior (e.g. %SIGTERM + * for death, %SIGQUIT for core dump, %SIGSTOP for job control stop, + * %SIGTSTP for stop unless in an orphaned pgrp), but the signal number + * reported will be @info->si_signo instead. + * + * Called with @task->sighand->siglock held, before dequeuing pending signals. + */ +static inline int tracehook_get_signal(struct task_struct *task, + struct pt_regs *regs, + siginfo_t *info, + struct k_sigaction *return_ka) +{ + return 0; +} + +/** + * tracehook_notify_jctl - report about job control stop/continue + * @notify: nonzero if this is the last thread in the group to stop + * @why: %CLD_STOPPED or %CLD_CONTINUED + * + * This is called when we might call do_notify_parent_cldstop(). + * It's called when about to stop for job control; we are already in + * %TASK_STOPPED state, about to call schedule(). It's also called when + * a delayed %CLD_STOPPED or %CLD_CONTINUED report is ready to be made. + * + * Return nonzero to generate a %SIGCHLD with @why, which is + * normal if @notify is nonzero. + * + * Called with no locks held. + */ +static inline int tracehook_notify_jctl(int notify, int why) +{ + return notify || (current->ptrace & PT_PTRACED); +} + +#define DEATH_REAP -1 +#define DEATH_DELAYED_GROUP_LEADER -2 + +/** + * tracehook_notify_death - task is dead, ready to notify parent + * @task: @current task now exiting + * @death_cookie: value to pass to tracehook_report_death() + * @group_dead: nonzero if this was the last thread in the group to die + * + * A return value >= 0 means call do_notify_parent() with that signal + * number. Negative return value can be %DEATH_REAP to self-reap right + * now, or %DEATH_DELAYED_GROUP_LEADER to a zombie without notifying our + * parent. Note that a return value of 0 means a do_notify_parent() call + * that sends no signal, but still wakes up a parent blocked in wait*(). + * + * Called with write_lock_irq(&tasklist_lock) held. + */ +static inline int tracehook_notify_death(struct task_struct *task, + void **death_cookie, int group_dead) +{ + if (task->exit_signal == -1) + return task->ptrace ? SIGCHLD : DEATH_REAP; + + /* + * If something other than our normal parent is ptracing us, then + * send it a SIGCHLD instead of honoring exit_signal. exit_signal + * only has special meaning to our real parent. + */ + if (thread_group_empty(task) && !ptrace_reparented(task)) + return task->exit_signal; + + return task->ptrace ? SIGCHLD : DEATH_DELAYED_GROUP_LEADER; +} + +/** + * tracehook_report_death - task is dead and ready to be reaped + * @task: @current task now exiting + * @signal: return value from tracheook_notify_death() + * @death_cookie: value passed back from tracehook_notify_death() + * @group_dead: nonzero if this was the last thread in the group to die + * + * Thread has just become a zombie or is about to self-reap. If positive, + * @signal is the signal number just sent to the parent (usually %SIGCHLD). + * If @signal is %DEATH_REAP, this thread will self-reap. If @signal is + * %DEATH_DELAYED_GROUP_LEADER, this is a delayed_group_leader() zombie. + * The @death_cookie was passed back by tracehook_notify_death(). + * + * If normal reaping is not inhibited, @task->exit_state might be changing + * in parallel. + * + * Called without locks. + */ +static inline void tracehook_report_death(struct task_struct *task, + int signal, void *death_cookie, + int group_dead) +{ +} + +#ifdef TIF_NOTIFY_RESUME +/** + * set_notify_resume - cause tracehook_notify_resume() to be called + * @task: task that will call tracehook_notify_resume() + * + * Calling this arranges that @task will call tracehook_notify_resume() + * before returning to user mode. If it's already running in user mode, + * it will enter the kernel and call tracehook_notify_resume() soon. + * If it's blocked, it will not be woken. + */ +static inline void set_notify_resume(struct task_struct *task) +{ + if (!test_and_set_tsk_thread_flag(task, TIF_NOTIFY_RESUME)) + kick_process(task); +} + +/** + * tracehook_notify_resume - report when about to return to user mode + * @regs: user-mode registers of @current task + * + * This is called when %TIF_NOTIFY_RESUME has been set. Now we are + * about to return to user mode, and the user state in @regs can be + * inspected or adjusted. The caller in arch code has cleared + * %TIF_NOTIFY_RESUME before the call. If the flag gets set again + * asynchronously, this will be called again before we return to + * user mode. + * + * Called without locks. + */ +static inline void tracehook_notify_resume(struct pt_regs *regs) +{ +} +#endif /* TIF_NOTIFY_RESUME */ + +#endif /* <linux/tracehook.h> */ |