nt-lite/code/kernel/hal/hal_output.c

// HAL output router. This file fans typed text streams out to registered physical and runtime endpoints.

#include <stdint.h>
#include <string.h>
#include <intrin.h>
#include <ntlite/ddi/hal_api.h>
#include <kernel/hal/hal_output.h>

#define HAL_OUTPUT_ENDPOINT_CAPACITY 8u

typedef struct HAL_OUTPUT_SLOT {
    HAL_OUTPUT_ENDPOINT Endpoint;
    volatile long Published;
} HAL_OUTPUT_SLOT;

static HAL_OUTPUT_SLOT gOutputSlots[HAL_OUTPUT_ENDPOINT_CAPACITY];
static volatile long gOutputRegistrationLock;
static volatile long long gOutputRecordCount;
static volatile long long gOutputByteCount;
static volatile long long gOutputEndpointWriteCount;
static volatile long long gOutputEmergencyRecordCount;
static volatile long gOutputEndpointCount;

// Acquires the endpoint registration lock.
static void HalOutputAcquireRegistrationLock(void) {
    while (_InterlockedCompareExchange(&gOutputRegistrationLock, 1, 0) != 0)
        _mm_pause();
}

// Releases the endpoint registration lock.
static void HalOutputReleaseRegistrationLock(void) {
    _InterlockedExchange(&gOutputRegistrationLock, 0);
}

// Registers one output endpoint in the fixed endpoint table.
static KSTATUS HalOutputRegisterEndpoint(const HAL_OUTPUT_ENDPOINT* endpoint, uint32_t* endpointIdOut) {
    if (!endpoint || !endpointIdOut || !endpoint->Name || !endpoint->Write ||
        endpoint->StreamMask == 0 || (endpoint->StreamMask & ~HAL_OUTPUT_STREAM_ALL) != 0)
        return STATUS_INVALID_PARAMETER;

    KSTATUS status = STATUS_NO_MEMORY;
    HalOutputAcquireRegistrationLock();
    for (uint32_t i = 0; i < HAL_OUTPUT_ENDPOINT_CAPACITY; i++) {
        HAL_OUTPUT_SLOT* slot = &gOutputSlots[i];
        if (_InterlockedCompareExchange(&slot->Published, 0, 0) != 0)
            continue;

        slot->Endpoint = *endpoint;
        _ReadWriteBarrier();
        _InterlockedExchange(&slot->Published, 1);
        _InterlockedIncrement(&gOutputEndpointCount);
        *endpointIdOut = i;
        status = STATUS_SUCCESS;
        break;
    }
    HalOutputReleaseRegistrationLock();
    return status;
}

// Replaces the stream subscription mask for a registered endpoint.
static KSTATUS HalOutputSetEndpointStreams(uint32_t endpointId, uint32_t streamMask) {
    if (endpointId >= HAL_OUTPUT_ENDPOINT_CAPACITY ||
        (streamMask & ~HAL_OUTPUT_STREAM_ALL) != 0)
        return STATUS_INVALID_PARAMETER;

    HAL_OUTPUT_SLOT* slot = &gOutputSlots[endpointId];
    if (_InterlockedCompareExchange(&slot->Published, 0, 0) == 0)
        return STATUS_NOT_FOUND;

    _InterlockedExchange((volatile long*)&slot->Endpoint.StreamMask, (long)streamMask);
    return STATUS_SUCCESS;
}

// Fans one text record out to every subscribed endpoint.
static void HalOutputWrite(const HAL_OUTPUT_RECORD* record) {
    if (!record || !record->Buffer || record->Length == 0 ||
        (record->Stream & HAL_OUTPUT_STREAM_ALL) == 0 ||
        (record->Stream & (record->Stream - 1u)) != 0)
        return;

    _InterlockedIncrement64(&gOutputRecordCount);
    _InterlockedExchangeAdd64(&gOutputByteCount, (long long)record->Length);
    if (record->Flags & HAL_OUTPUT_WRITE_EMERGENCY)
        _InterlockedIncrement64(&gOutputEmergencyRecordCount);

    for (uint32_t i = 0; i < HAL_OUTPUT_ENDPOINT_CAPACITY; i++) {
        HAL_OUTPUT_SLOT* slot = &gOutputSlots[i];
        if (_InterlockedCompareExchange(&slot->Published, 0, 0) == 0)
            continue;

        uint32_t streams = (uint32_t)_InterlockedCompareExchange(
            (volatile long*)&slot->Endpoint.StreamMask, 0, 0);
        if ((streams & record->Stream) == 0)
            continue;
        if ((record->Flags & HAL_OUTPUT_WRITE_EMERGENCY) &&
            !(slot->Endpoint.Capabilities & HAL_OUTPUT_ENDPOINT_PANIC_SAFE))
            continue;

        HAL_OUTPUT_ENDPOINT_WRITE write = slot->Endpoint.Write;
        void* context = slot->Endpoint.Context;
        if (!write)
            continue;

        write(context, record);
        _InterlockedIncrement64(&gOutputEndpointWriteCount);
    }
}

// Returns a snapshot of output router counters.
static void HalOutputQueryStats(HAL_OUTPUT_STATS* statsOut) {
    if (!statsOut)
        return;

    memset(statsOut, 0, sizeof(*statsOut));
    statsOut->RecordCount = (uint64_t)_InterlockedCompareExchange64(&gOutputRecordCount, 0, 0);
    statsOut->ByteCount = (uint64_t)_InterlockedCompareExchange64(&gOutputByteCount, 0, 0);
    statsOut->EndpointWriteCount = (uint64_t)_InterlockedCompareExchange64(&gOutputEndpointWriteCount, 0, 0);
    statsOut->EmergencyRecordCount = (uint64_t)_InterlockedCompareExchange64(&gOutputEmergencyRecordCount, 0, 0);
    statsOut->EndpointCount = (uint32_t)_InterlockedCompareExchange(&gOutputEndpointCount, 0, 0);
}

// Initializes the fixed HAL output endpoint table.
void HalOutputInitialize(HAL_OUTPUT_ROUTER* output) {
    if (!output)
        return;

    memset(gOutputSlots, 0, sizeof(gOutputSlots));
    gOutputRegistrationLock = 0;
    gOutputRecordCount = 0;
    gOutputByteCount = 0;
    gOutputEndpointWriteCount = 0;
    gOutputEmergencyRecordCount = 0;
    gOutputEndpointCount = 0;

    memset(output, 0, sizeof(*output));
    output->RegisterEndpoint = HalOutputRegisterEndpoint;
    output->SetEndpointStreams = HalOutputSetEndpointStreams;
    output->Write = HalOutputWrite;
    output->QueryStats = HalOutputQueryStats;
    output->SerialEndpointId = HAL_OUTPUT_ENDPOINT_INVALID;
    output->BootFramebufferEndpointId = HAL_OUTPUT_ENDPOINT_INVALID;
}