/*
* Tracing hooks
*
* Copyright (C) 2008-2009 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)
{
if (step) {
siginfo_t info;
user_single_step_siginfo(current, regs, &info);
force_sig_info(SIGTRAP, &info, current);
return;
}
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.
*
* @task->signal->cred_guard_mutex is held by the caller through the do_execve().
*/
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 no one 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
* @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.
* 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(struct pt_regs *regs,
unsigned long clone_flags,
pid_t pid, struct task_struct *child)
{
if (unlikely(task_ptrace(child))) {
/*
* It doesn't matter who attached/attaching to this
* task, the pending SIGSTOP is right in any case.
*/
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
*
* Return zero iff tracing doesn't care to examine this ignored signal,
* so it can short-circuit normal delivery and never even get queued.
*
* Called with @task->sighand->siglock held.
*/
static inline int tracehook_consider_ignored_signal(struct task_struct *task,
int sig)
{
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
*
* Return nonzero to prevent special handling of this termination signal.
* Normally handler for signal 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)
{
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 artificial 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: zero, %CLD_STOPPED or %CLD_CONTINUED
* @why: %CLD_STOPPED or %CLD_CONTINUED
*
* This is called when we might call do_notify_parent_cldstop().
*
* @notify is zero if we would not ordinarily send a %SIGCHLD,
* or is the %CLD_STOPPED or %CLD_CONTINUED .si_code for %SIGCHLD.
*
* @why is %CLD_STOPPED when about to stop for job control;
* we are already in %TASK_STOPPED state, about to call schedule().
* It might also be that we have just exited (check %PF_EXITING),
* but need to report that a group-wide stop is complete.
*
* @why is %CLD_CONTINUED when waking up after job control stop and
* ready to make a delayed @notify report.
*
* Return the %CLD_* value for %SIGCHLD, or zero to generate no signal.
*
* Called with the siglock held.
*/
static inline int tracehook_notify_jctl(int notify, int why)
{
return notify ?: (current->ptrace & PT_PTRACED) ? why : 0;
}
/**
* tracehook_finish_jctl - report about return from job control stop
*
* This is called by do_signal_stop() after wakeup.
*/
static inline void tracehook_finish_jctl(void)
{
}
#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_detached(task))
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> */