nt-lite/code/kernel/ke_boot_config.c

// Kernel boot configuration parser. This file intentionally implements only the boot.ini settings the kernel owns.

#include <kernel/ke_boot_config.h>

#include <ntlite/ddk/debug.h>

#include <stdbool.h>
#include <string.h>

// Returns whether one character is horizontal configuration whitespace.
static bool KiBootConfigSpace(char c) {
    return c == ' ' || c == '\t' || c == '\r';
}

// Trims horizontal whitespace from one immutable line span.
static void KiBootConfigTrim(const char** begin, const char** end) {
    while (*begin < *end && KiBootConfigSpace(**begin))
        ++*begin;
    while (*end > *begin && KiBootConfigSpace((*end)[-1]))
        --*end;
}

// Returns whether one immutable span exactly matches a NUL-terminated string.
static bool KiBootConfigSpanEquals(const char* begin, const char* end, const char* text) {
    while (begin < end && *text) {
        if (*begin++ != *text++)
            return false;
    }
    return begin == end && *text == '\0';
}

// Parses one unsigned decimal or 0x-prefixed hexadecimal value without accepting trailing junk.
static KSTATUS KiBootConfigParseUInt32(const char* begin, const char* end, uint32_t* valueOut) {
    KiBootConfigTrim(&begin, &end);
    if (begin == end || !valueOut)
        return NTLSTATUS_INVALID_PARAMETER;

    uint32_t base = 10;
    if (end - begin >= 2 && begin[0] == '0' && (begin[1] == 'x' || begin[1] == 'X')) {
        base = 16;
        begin += 2;
        if (begin == end)
            return NTLSTATUS_INVALID_PARAMETER;
    }

    uint32_t value = 0;
    for (const char* p = begin; p < end; ++p) {
        uint32_t digit;
        if (*p >= '0' && *p <= '9') digit = (uint32_t)(*p - '0');
        else if (*p >= 'a' && *p <= 'f') digit = (uint32_t)(10 + *p - 'a');
        else if (*p >= 'A' && *p <= 'F') digit = (uint32_t)(10 + *p - 'A');
        else return NTLSTATUS_INVALID_PARAMETER;
        if (digit >= base || value > (UINT32_MAX - digit) / base)
            return NTLSTATUS_INVALID_PARAMETER;
        value = value * base + digit;
    }

    *valueOut = value;
    return NTLSTATUS_SUCCESS;
}

// Copies one trimmed configuration value into a fixed kernel-owned string.
static KSTATUS KiBootConfigCopyString(const char* begin, const char* end, char* buffer, size_t bufferSize) {
    KiBootConfigTrim(&begin, &end);
    size_t length = (size_t)(end - begin);
    if (!buffer || bufferSize == 0 || length >= bufferSize)
        return NTLSTATUS_BUFFER_TOO_SMALL;
    memcpy(buffer, begin, length);
    buffer[length] = '\0';
    return NTLSTATUS_SUCCESS;
}

// Parses the kernel-owned boot.ini settings from the raw bootloader string.
KSTATUS KeParseBootConfiguration(const char* text, size_t length, KE_BOOT_CONFIG* configOut) {
    if (!text || !configOut)
        return NTLSTATUS_INVALID_PARAMETER;

    KE_BOOT_CONFIG config = {0};
    bool systemVolumeSeen = false;
    char section[32] = {0};
    size_t offset = 0;

    while (offset < length) {
        size_t lineStart = offset;
        while (offset < length && text[offset] != '\n')
            ++offset;
        size_t lineEnd = offset;
        if (offset < length)
            ++offset;

        const char* begin = text + lineStart;
        const char* end = text + lineEnd;
        KiBootConfigTrim(&begin, &end);
        if (begin == end || *begin == ';' || *begin == '#')
            continue;

        if (*begin == '[') {
            if (end[-1] != ']')
                return NTLSTATUS_INVALID_PARAMETER;
            const char* sectionBegin = begin + 1;
            const char* sectionEnd = end - 1;
            KiBootConfigTrim(&sectionBegin, &sectionEnd);
            size_t sectionLength = (size_t)(sectionEnd - sectionBegin);
            if (sectionLength >= sizeof(section))
                return NTLSTATUS_BUFFER_TOO_SMALL;
            memcpy(section, sectionBegin, sectionLength);
            section[sectionLength] = '\0';
            continue;
        }

        const char* equals = NULL;
        for (const char* p = begin; p < end; ++p) {
            if (*p == '=') {
                equals = p;
                break;
            }
        }
        if (!equals)
            return NTLSTATUS_INVALID_PARAMETER;

        const char* keyBegin = begin;
        const char* keyEnd = equals;
        const char* valueBegin = equals + 1;
        const char* valueEnd = end;
        KiBootConfigTrim(&keyBegin, &keyEnd);

        if (strcmp(section, "boot") == 0 && KiBootConfigSpanEquals(keyBegin, keyEnd, "system_volume")) {
            if (systemVolumeSeen)
                return NTLSTATUS_INVALID_PARAMETER;
            KSTATUS status = KiBootConfigCopyString(valueBegin, valueEnd,
                                                    config.SystemVolume, sizeof(config.SystemVolume));
            if (!KSUCCESS(status) || config.SystemVolume[0] == '\0')
                return KSUCCESS(status) ? NTLSTATUS_INVALID_PARAMETER : status;
            systemVolumeSeen = true;
        } else if (strcmp(section, "kernel") == 0 && KiBootConfigSpanEquals(keyBegin, keyEnd, "debug")) {
            KSTATUS status = KiBootConfigParseUInt32(valueBegin, valueEnd, &config.Debug);
            if (!KSUCCESS(status))
                return status;
            if (config.Debug & ~KE_DEBUG_VALID_MASK)
                return NTLSTATUS_INVALID_PARAMETER;
        } else if (strcmp(section, "init") == 0 && KiBootConfigSpanEquals(keyBegin, keyEnd, "commandline")) {
            KSTATUS status = KiBootConfigCopyString(valueBegin, valueEnd,
                                                    config.CommandLine, sizeof(config.CommandLine));
            if (!KSUCCESS(status))
                return status;
        }
    }

    if (!systemVolumeSeen)
        return NTLSTATUS_NOT_FOUND;

    *configOut = config;
    return NTLSTATUS_SUCCESS;
}