mach-detours/tests/test_threads.cpp

// Copyright (c) Lysann Tranvouez.  All rights reserved.

#include <algorithm>
#include <catch2/catch_test_macros.hpp>

#include <mach_detours.h>
#include <pthread.h>
#include <unistd.h>

static const char* callee(int a, int b, int c)
{
    return "localFunction";
}
static int g_b = 6;
static int g_c = 3;

__attribute__((target("branch-protection=pac-ret+bti")))
static const char* localFunction()
{
    // This is just some "complicated" code to ensure localFunction gets the branch protection instructions (needs a callee)
    int a = 53;
    int b = g_b++;
    auto ret = callee(a, b, 17);
    g_c = g_b;
    return ret;
}
static const char* localFunctionDetour()
{
    return "localFunctionDetour";
}
static const char* (*realLocalFunction)() = localFunction;

struct threadData
{
    std::atomic<int> loopCounter;
    bool cancel = false;
};

static void* threadFunc(void* pUserArg)
{
    auto& data = *static_cast<threadData*>(pUserArg);
    while (!data.cancel) {
        localFunction();
        localFunction();
        localFunction();
        localFunction();
        localFunction();
        ++data.loopCounter;
    }
    return nullptr;
}

template<size_t numThreads>
bool resetLoopCountersAndWaitForLoop(std::array<threadData, numThreads>& threadDatas, std::optional<std::chrono::seconds> timeout = std::nullopt)
{
    for (auto i = 0; i < numThreads; i++) {
        threadDatas[i].loopCounter = 0;
    }

    const auto endTime = timeout ? std::make_optional(std::chrono::steady_clock::now() + *timeout) : std::nullopt;
    while (true) {
        // we check for >= 2 to be sure we did a full loop - we don't want to execute just the line incrementing the counter!
        const bool anyLooped = std::ranges::any_of(threadDatas, [](const threadData& data){ return data.loopCounter >= 2; });
        if (anyLooped) {
            return true;
        }
        if (endTime && std::chrono::steady_clock::now() > *endTime) {
            return false;
        }
        usleep( 100 );
    }
}

TEST_CASE( "Handling other threads", "[attach][local][threads]" )
{
    using namespace std::chrono_literals;

    constexpr auto numThreads = 150;
    pthread_t threads[numThreads];
    std::array<threadData, numThreads> threadDatas{};
    for (auto i = 0; i < numThreads; i++) {
        pthread_create(&threads[i], nullptr, threadFunc, (void*)&threadDatas[i]);
    }

    SECTION( "running threads modify a value" )
    {
        const int saved_b = g_b;
        resetLoopCountersAndWaitForLoop(threadDatas);
        CHECK( saved_b != g_b );
    }

    SECTION( "registered threads are suspended during transaction and resumed afterwards" )
    {
        SECTION( "manual thread managing" )
        {
            CHECK( detour_transaction_begin() == err_none );
            for (auto&& thread : threads) {
                CHECK( detour_manage_thread( pthread_mach_thread_np(thread) ) == err_none );
            }
        }
        SECTION( "manage_all_threads" )
        {
            CHECK( detour_transaction_begin() == err_none );
            CHECK( detour_manage_all_threads() == err_none );
        }
        SECTION( "transaction_begin_managed" )
        {
            CHECK( detour_transaction_begin_managed() == err_none );
        }

        int saved_b = g_b;
        resetLoopCountersAndWaitForLoop(threadDatas, 1s);
        CHECK( saved_b == g_b );

        CHECK( detour_transaction_commit() == err_none );

        saved_b = g_b;
        resetLoopCountersAndWaitForLoop(threadDatas);
        CHECK( saved_b != g_b );
    }

    SECTION( "aborting a transaction resumes too" )
    {
        CHECK( detour_transaction_begin_managed() == err_none );
        CHECK( detour_transaction_abort() == err_none );

        const int saved_b = g_b;
        resetLoopCountersAndWaitForLoop(threadDatas);
        CHECK( saved_b != g_b );
    }

    SECTION( "thread's PC gets redirected on commit, if it was in an overridden area" )
    {
        // Note that this test case doesn't guarantee that any thread is in the section of code that gets moved into the
        // trampoline. So if buggy it could be flaky. You can try using more threads to get a more reliable repro.

        CHECK( detour_transaction_begin_managed() == err_none );
        CHECK( detour_attach_and_commit(reinterpret_cast<detour_func_t*>(&realLocalFunction), reinterpret_cast<detour_func_t>(localFunctionDetour)) == err_none );

        const int saved_b = g_b;
        resetLoopCountersAndWaitForLoop(threadDatas);
        CHECK( saved_b == g_b );

        // clean up
        CHECK( detour_transaction_begin_managed() == err_none );
        CHECK( detour_detach_and_commit(reinterpret_cast<detour_func_t*>(&realLocalFunction), reinterpret_cast<detour_func_t>(localFunctionDetour)) == err_none );
    }

    for (auto i = 0; i < numThreads; i++) {
        threadDatas[i].cancel = true;
    }
    for (auto i = 0; i < numThreads; i++) {
        pthread_join(threads[i], nullptr);
    }
}