1 files changed, 576 insertions, 0 deletions

diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h
new file mode 100644
index 000000000000..b1875582c1a1
--- /dev/null
+++ b/include/linux/tracehook.h
@@ -0,0 +1,576 @@
+/*
+ * 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_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)) {
+                /*
+                 * 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);
+}
+
+/**
+ * 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
+ *
+ * Return the signal number to send our parent with do_notify_parent(), or
+ * zero to send no signal and leave a zombie, or -1 to self-reap right now.
+ *
+ * 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 : -1;
+
+        /*
+         * 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 : 0;
+}
+
+/**
+ * tracehook_report_death - task is dead and ready to be reaped
+ * @task:               @current task now exiting
+ * @signal:             signal number sent to parent, or 0 or -1
+ * @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 -1, this thread will self-reap.  If @signal is 0, 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> */