// Copyright (c) 2020-present The Bitcoin Core developers

// Distributed under the MIT software license, see the accompanying

// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#ifndef BITCOIN_UTIL_TRACE_H

#define BITCOIN_UTIL_TRACE_H

#include <bitcoin-build-config.h> // IWYU pragma: keep

#ifdef ENABLE_TRACING

// Workaround for https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103395

// systemtap 4.6 on 32-bit ARM triggers internal compiler error

// (this workaround is included in systemtap 4.7+)

#if defined(__arm__)

#  define STAP_SDT_ARG_CONSTRAINT g

#endif

// Setting SDT_USE_VARIADIC lets systemtap (sys/sdt.h) know that we want to use

// the optional variadic macros to define tracepoints.

#define SDT_USE_VARIADIC 1

// Setting _SDT_HAS_SEMAPHORES let's systemtap (sys/sdt.h) know that we want to

// use the optional semaphore feature for our tracepoints. This feature allows

// us to check if something is attached to a tracepoint. We only want to prepare

// some potentially expensive tracepoint arguments, if the tracepoint is being

// used. Here, an expensive argument preparation could, for example, be

// calculating a hash or serialization of a data structure.

#define _SDT_HAS_SEMAPHORES 1

// Used to define a counting semaphore for a tracepoint. This semaphore is

// automatically incremented by tracing frameworks (bpftrace, bcc, libbpf, ...)

// upon attaching to the tracepoint and decremented when detaching. This needs

// to be a global variable. It's placed in the '.probes' ELF section.

#define TRACEPOINT_SEMAPHORE(context, event) \

    unsigned short context##_##event##_semaphore __attribute__((section(".probes")))

#include <sys/sdt.h>

// Returns true if something is attached to the tracepoint.

#define TRACEPOINT_ACTIVE(context, event) (context##_##event##_semaphore > 0)

// A USDT tracepoint with one to twelve arguments. It's checked that the

// tracepoint is active before preparing its arguments.

#define TRACEPOINT(context, event, ...)                                         \

    do {                                                                        \

        if (TRACEPOINT_ACTIVE(context, event)) {                                \

            STAP_PROBEV(context, event __VA_OPT__(, ) __VA_ARGS__);             \

        }                                                                       \

    } while(0)

#else

#define TRACEPOINT_SEMAPHORE(context, event)

#define TRACEPOINT_ACTIVE(context, event) false

#define TRACEPOINT(context, ...)

#endif // ENABLE_TRACING

#endif // BITCOIN_UTIL_TRACE_H