tracehook.h

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/*
 * 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>
#include <linux/task_work.h>
struct linux_binprm;

/*
 * ptrace report for syscall entry and exit looks identical.
 */
static inline int ptrace_report_syscall(struct pt_regs *regs)
{
    int ptrace = current->ptrace;

    if (!(ptrace & PT_PTRACED))
        return 0;

    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;
    }

    return fatal_signal_pending(current);
}

static inline __must_check int tracehook_report_syscall_entry(
    struct pt_regs *regs)
{
    return ptrace_report_syscall(regs);
}

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);
}

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);
}

static inline void set_notify_resume(struct task_struct *task)
{
#ifdef TIF_NOTIFY_RESUME
    if (!test_and_set_tsk_thread_flag(task, TIF_NOTIFY_RESUME))
        kick_process(task);
#endif
}

static inline void tracehook_notify_resume(struct pt_regs *regs)
{
    /*
     * The caller just cleared TIF_NOTIFY_RESUME. This barrier
     * pairs with task_work_add()->set_notify_resume() after
     * hlist_add_head(task->task_works);
     */
    smp_mb__after_clear_bit();
    if (unlikely(current->task_works))
        task_work_run();
}

#endif  /* <linux/tracehook.h> */