WinDriver/win31drv/neload.c

// ============================================================================
// neload.c - NE (New Executable) format loader
//
// Loads Windows 3.x 16-bit DLLs/drivers (.DRV files) into protected
// mode memory.  Each NE segment gets a DPMI LDT descriptor (16-bit
// code or data), and the segment data is loaded from the file.
//
// Loading steps:
//   1. Read and validate MZ (DOS stub) + NE headers
//   2. Parse the module reference table (imported DLL names)
//   3. Parse the resident name table (module name + named exports)
//   4. Parse the entry table (ordinal -> segment:offset mappings)
//   5. Allocate memory and LDT descriptors for each segment
//   6. Load segment data from the file
//   7. Process relocations (internal refs, imports by ordinal/name)
//
// Import resolution is delegated to a caller-supplied callback
// (ImportResolverT) which returns a 16:16 far pointer for each
// imported function.  If the callback returns FARPTR16_NULL, the
// loader patches in a stub address and logs a warning.
//
// Relocations are applied as fixups to the loaded segment data.
// Supported fixup types: LOBYTE, SEGMENT, FAR_ADDR (seg:off),
// OFFSET, and additive fixups.  Chained relocations (linked lists
// within the segment) are followed to completion.
// ============================================================================

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#include <inttypes.h>
#include <dpmi.h>
#include <go32.h>
#include <sys/movedata.h>
#include <sys/nearptr.h>

#include "neload.h"
#include "wintypes.h"
#include "log.h"

// Forward declarations
static bool readHeaders(NeModuleT *mod, FILE *fp);
static bool loadSegments(NeModuleT *mod, FILE *fp, ImportResolverT resolver);
static bool allocateSegment(NeModuleT *mod, int segIdx, uint32_t size, bool isCode);
static bool loadSegmentData(NeModuleT *mod, int segIdx, FILE *fp, uint32_t fileOffset, uint32_t fileSize);
static bool processRelocations(NeModuleT *mod, int segIdx, FILE *fp, ImportResolverT resolver);
static bool parseEntryTable(NeModuleT *mod, FILE *fp);
static bool parseModuleReferences(NeModuleT *mod, FILE *fp);
static bool parseResidentNames(NeModuleT *mod, FILE *fp);
static void freeSegment(LoadedSegT *seg);
static uint16_t makeDescriptor16(uint32_t base, uint32_t limit, bool isCode);
static void dbgPrint(const char *fmt, ...);

static bool gDebug = false;


static void dbgPrint(const char *fmt, ...)
{
    if (!gDebug) {
        return;
    }
    va_list ap;
    va_start(ap, fmt);
    logErrV(fmt, ap);
    va_end(ap);
}


bool neLoadModule(NeModuleT *mod, const char *filePath, ImportResolverT resolver)
{
    memset(mod, 0, sizeof(NeModuleT));

    FILE *fp = fopen(filePath, "rb");
    if (!fp) {
        logErr("neload: cannot open '%s'\n", filePath);
        return false;
    }

    bool ok = false;

    // Step 1: Read and validate MZ + NE headers
    if (!readHeaders(mod, fp)) {
        goto done;
    }

    // Step 2: Parse module reference table (imported module names)
    if (!parseModuleReferences(mod, fp)) {
        goto done;
    }

    // Step 3: Parse resident name table (module name + exports by name)
    if (!parseResidentNames(mod, fp)) {
        goto done;
    }

    // Step 4: Parse entry table (export ordinals -> segment:offset)
    if (!parseEntryTable(mod, fp)) {
        goto done;
    }

    // Step 5: Load segments, apply relocations
    if (!loadSegments(mod, fp, resolver)) {
        goto done;
    }

    // Resolve auto data segment selector
    if (mod->neHeader.autoDataSegIndex > 0 &&
        mod->neHeader.autoDataSegIndex <= mod->segmentCount) {
        mod->autoDataSel = mod->segments[mod->neHeader.autoDataSegIndex - 1].selector;
    }

    mod->loaded = true;
    ok = true;

done:
    fclose(fp);
    if (!ok) {
        neUnloadModule(mod);
    }
    return ok;
}


void neUnloadModule(NeModuleT *mod)
{
    for (uint16_t i = 0; i < mod->segmentCount; i++) {
        freeSegment(&mod->segments[i]);
    }
    mod->segmentCount = 0;
    mod->loaded       = false;
}


bool neLookupExport(const NeModuleT *mod, uint16_t ordinal, uint16_t *seg, uint16_t *off, uint16_t *sel)
{
    if (ordinal == 0 || ordinal >= NE_MAX_EXPORTS) {
        return false;
    }
    if (mod->exports[ordinal].segIndex == 0) {
        return false;
    }

    ExportEntryT *e = (ExportEntryT *)&mod->exports[ordinal];
    uint16_t sIdx   = e->segIndex - 1;

    if (sIdx >= mod->segmentCount) {
        return false;
    }

    if (seg) {
        *seg = e->segIndex;
    }
    if (off) {
        *off = e->offset;
    }
    if (sel) {
        *sel = mod->segments[sIdx].selector;
    }
    return true;
}


uint16_t neLookupExportByName(const NeModuleT *mod, const char *name, const char *filePath)
{
    // We need to re-read the resident name table from the file to search by name.
    // The first entry is the module name; subsequent entries are exports.
    FILE *fp = fopen(filePath, "rb");
    if (!fp) {
        return 0;
    }

    uint32_t tableOff = mod->neHeaderFileOffset + mod->neHeader.resNameTableOffset;
    fseek(fp, tableOff, SEEK_SET);

    uint16_t ordinal = 0;
    while (1) {
        uint8_t nameLen;
        if (fread(&nameLen, 1, 1, fp) != 1 || nameLen == 0) {
            break;
        }

        char entryName[256];
        if (fread(entryName, 1, nameLen, fp) != nameLen) {
            break;
        }
        entryName[nameLen] = '\0';

        uint16_t ord;
        if (fread(&ord, 2, 1, fp) != 1) {
            break;
        }

        if (strcasecmp(entryName, name) == 0) {
            ordinal = ord;
            break;
        }
    }

    fclose(fp);
    return ordinal;
}


void neDumpModule(const NeModuleT *mod)
{
    logErr("=== NE Module: %s ===\n", mod->moduleName);
    logErr("  Segments: %u\n", mod->segmentCount);
    logErr("  Auto data segment: %u\n", mod->neHeader.autoDataSegIndex);
    logErr("  Module flags: 0x%04X", mod->neHeader.moduleFlags);
    if (mod->neHeader.moduleFlags & NE_FFLAGS_DLL) {
        logErr(" (DLL)");
    }
    logErr("\n");
    logErr("  Target OS: 0x%02X\n", mod->neHeader.targetOS);
    logErr("  Expected Windows version: %u.%u\n",
            mod->neHeader.expectedWinVer >> 8,
            mod->neHeader.expectedWinVer & 0xFF);

    logErr("  Segments:\n");
    for (uint16_t i = 0; i < mod->segmentCount; i++) {
        LoadedSegT *s = (LoadedSegT *)&mod->segments[i];
        logErr("    [%u] %s sel=0x%04X base=0x%08" PRIX32 " size=%" PRIu32,
                i + 1,
                s->isCode ? "CODE" : "DATA",
                s->selector,
                s->linearAddr,
                s->size);
        if (s->flags & NE_SEGF_PRELOAD) {
            logErr(" PRELOAD");
        }
        if (s->flags & NE_SEGF_MOVEABLE) {
            logErr(" MOVEABLE");
        }
        logErr("\n");
    }

    logErr("  Module references:\n");
    for (uint16_t i = 0; i < mod->modRefCount; i++) {
        logErr("    [%u] %s\n", i + 1, mod->modRefNames[i]);
    }

    logErr("  Exports:\n");
    for (uint16_t i = 1; i < NE_MAX_EXPORTS; i++) {
        if (mod->exports[i].segIndex != 0) {
            logErr("    ord %u -> seg %u : 0x%04X (sel 0x%04X)\n",
                    i,
                    mod->exports[i].segIndex,
                    mod->exports[i].offset,
                    mod->exports[i].selector);
        }
    }
}


// ============================================================================
// Internal implementation
// ============================================================================

static bool readHeaders(NeModuleT *mod, FILE *fp)
{
    // Read MZ header
    MzHeaderT mz;
    if (fread(&mz, sizeof(mz), 1, fp) != 1) {
        logErr("neload: failed to read MZ header\n");
        return false;
    }
    if (mz.signature != MZ_SIGNATURE) {
        logErr("neload: not an MZ executable (sig=0x%04X)\n", mz.signature);
        return false;
    }

    // Read NE header
    mod->neHeaderFileOffset = mz.neHeaderOffset;
    fseek(fp, mz.neHeaderOffset, SEEK_SET);

    if (fread(&mod->neHeader, sizeof(NeHeaderT), 1, fp) != 1) {
        logErr("neload: failed to read NE header\n");
        return false;
    }
    if (mod->neHeader.signature != NE_SIGNATURE) {
        logErr("neload: not an NE executable (sig=0x%04X)\n",
                mod->neHeader.signature);
        return false;
    }

    // Validate
    if (mod->neHeader.segmentCount > NE_MAX_SEGMENTS) {
        logErr("neload: too many segments (%u, max %u)\n",
                mod->neHeader.segmentCount, NE_MAX_SEGMENTS);
        return false;
    }

    mod->segmentCount     = mod->neHeader.segmentCount;
    mod->sectorAlignShift = mod->neHeader.sectorAlignShift;
    if (mod->sectorAlignShift == 0) {
        mod->sectorAlignShift = 9; // Default: 512-byte sectors
    }

    dbgPrint("neload: NE header at 0x%08" PRIX32 ", %u segments, %u align shift\n",
             mod->neHeaderFileOffset, mod->segmentCount, mod->sectorAlignShift);

    return true;
}


static bool parseModuleReferences(NeModuleT *mod, FILE *fp)
{
    if (mod->neHeader.moduleRefCount == 0) {
        return true;
    }

    mod->modRefCount = mod->neHeader.moduleRefCount;
    if (mod->modRefCount > NE_MAX_MODREFS) {
        logErr("neload: too many module references (%u, max %u)\n",
                mod->modRefCount, NE_MAX_MODREFS);
        return false;
    }

    // Read module reference table (array of offsets into imported name table)
    uint32_t modRefTableOff = mod->neHeaderFileOffset + mod->neHeader.modRefTableOffset;
    fseek(fp, modRefTableOff, SEEK_SET);

    uint16_t nameOffsets[NE_MAX_MODREFS];
    if (fread(nameOffsets, 2, mod->modRefCount, fp) != mod->modRefCount) {
        logErr("neload: failed to read module reference table\n");
        return false;
    }

    // Resolve each offset to a name from the imported name table
    uint32_t importNameTableOff = mod->neHeaderFileOffset + mod->neHeader.importNameTableOffset;

    for (uint16_t i = 0; i < mod->modRefCount; i++) {
        uint32_t nameOff = importNameTableOff + nameOffsets[i];
        fseek(fp, nameOff, SEEK_SET);

        uint8_t nameLen;
        if (fread(&nameLen, 1, 1, fp) != 1) {
            logErr("neload: failed to read module name length\n");
            return false;
        }

        if (nameLen > 31) {
            nameLen = 31;
        }
        if (fread(mod->modRefNames[i], 1, nameLen, fp) != nameLen) {
            logErr("neload: failed to read module name\n");
            return false;
        }
        mod->modRefNames[i][nameLen] = '\0';

        dbgPrint("neload: module ref [%u] = '%s'\n", i + 1, mod->modRefNames[i]);
    }

    return true;
}


static bool parseResidentNames(NeModuleT *mod, FILE *fp)
{
    uint32_t tableOff = mod->neHeaderFileOffset + mod->neHeader.resNameTableOffset;
    fseek(fp, tableOff, SEEK_SET);

    bool firstEntry = true;
    while (1) {
        uint8_t nameLen;
        if (fread(&nameLen, 1, 1, fp) != 1 || nameLen == 0) {
            break;
        }

        char name[256];
        if (fread(name, 1, nameLen, fp) != nameLen) {
            break;
        }
        name[nameLen] = '\0';

        uint16_t ordinal;
        if (fread(&ordinal, 2, 1, fp) != 1) {
            break;
        }

        if (firstEntry) {
            // First entry is the module name (ordinal 0)
            memcpy(mod->moduleName, name, sizeof(mod->moduleName) - 1);
            mod->moduleName[sizeof(mod->moduleName) - 1] = '\0';
            dbgPrint("neload: module name = '%s'\n", mod->moduleName);
            firstEntry = false;
        } else {
            dbgPrint("neload: resident name '%s' = ordinal %u\n", name, ordinal);
        }
    }

    return true;
}


static bool parseEntryTable(NeModuleT *mod, FILE *fp)
{
    uint32_t tableOff  = mod->neHeaderFileOffset + mod->neHeader.entryTableOffset;
    uint32_t tableEnd  = tableOff + mod->neHeader.entryTableSize;

    fseek(fp, tableOff, SEEK_SET);

    uint16_t currentOrdinal = 1;

    while (ftell(fp) < (long)tableEnd) {
        uint8_t bundleCount;
        uint8_t indicator;

        if (fread(&bundleCount, 1, 1, fp) != 1 || bundleCount == 0) {
            break; // End of entry table
        }
        if (fread(&indicator, 1, 1, fp) != 1) {
            break;
        }

        if (indicator == 0x00) {
            // Empty bundle - skip these ordinals
            currentOrdinal += bundleCount;
            continue;
        }

        for (uint8_t i = 0; i < bundleCount; i++) {
            if (currentOrdinal >= NE_MAX_EXPORTS) {
                logErr("neload: export ordinal %u exceeds max\n", currentOrdinal);
                currentOrdinal++;
                continue;
            }

            if (indicator == 0xFF) {
                // Moveable segment entry
                NeMoveableEntryT entry;
                if (fread(&entry, sizeof(entry), 1, fp) != 1) {
                    return false;
                }
                mod->exports[currentOrdinal].segIndex = entry.segIndex;
                mod->exports[currentOrdinal].offset   = entry.offset;
                mod->exports[currentOrdinal].flags    = entry.flags;
                mod->exportCount++;

                dbgPrint("neload: entry ord %u -> seg %u : 0x%04X (moveable)\n",
                         currentOrdinal, entry.segIndex, entry.offset);
            } else {
                // Fixed segment entry (indicator = segment number)
                NeFixedEntryT entry;
                if (fread(&entry, sizeof(entry), 1, fp) != 1) {
                    return false;
                }
                mod->exports[currentOrdinal].segIndex = indicator;
                mod->exports[currentOrdinal].offset   = entry.offset;
                mod->exports[currentOrdinal].flags    = entry.flags;
                mod->exportCount++;

                dbgPrint("neload: entry ord %u -> seg %u : 0x%04X (fixed)\n",
                         currentOrdinal, indicator, entry.offset);
            }

            currentOrdinal++;
        }
    }

    dbgPrint("neload: %u export entries parsed\n", mod->exportCount);
    return true;
}


static bool loadSegments(NeModuleT *mod, FILE *fp, ImportResolverT resolver)
{
    // Read segment table
    uint32_t segTableOff = mod->neHeaderFileOffset + mod->neHeader.segmentTableOffset;
    fseek(fp, segTableOff, SEEK_SET);

    NeSegEntryT segTable[NE_MAX_SEGMENTS];
    if (fread(segTable, sizeof(NeSegEntryT), mod->segmentCount, fp) != mod->segmentCount) {
        logErr("neload: failed to read segment table\n");
        return false;
    }

    // Load each segment
    for (uint16_t i = 0; i < mod->segmentCount; i++) {
        NeSegEntryT *se = &segTable[i];
        bool isCode     = !(se->flags & NE_SEGF_DATA);

        // Determine segment size
        uint32_t fileLen = se->fileLength;
        if (fileLen == 0 && se->fileSectorOffset != 0) {
            fileLen = 0x10000; // 64K
        }

        uint32_t allocSize = se->minAllocSize;
        if (allocSize == 0) {
            allocSize = 0x10000; // 64K
        }
        if (allocSize < fileLen) {
            allocSize = fileLen;
        }

        // Allocate memory and create descriptor
        if (!allocateSegment(mod, i, allocSize, isCode)) {
            logErr("neload: failed to allocate segment %u\n", i + 1);
            return false;
        }

        mod->segments[i].flags    = se->flags;
        mod->segments[i].fileSize = fileLen;

        // Load data from file
        if (se->fileSectorOffset != 0 && fileLen > 0) {
            uint32_t fileOffset = (uint32_t)se->fileSectorOffset << mod->sectorAlignShift;
            if (!loadSegmentData(mod, i, fp, fileOffset, fileLen)) {
                logErr("neload: failed to load segment %u data\n", i + 1);
                return false;
            }
        }

        dbgPrint("neload: loaded seg %u: %s size=%" PRIu32 " filelen=%" PRIu32 " sel=0x%04X base=0x%08" PRIX32 "\n",
                 i + 1, isCode ? "CODE" : "DATA",
                 allocSize, fileLen,
                 mod->segments[i].selector,
                 mod->segments[i].linearAddr);
    }

    // Resolve export selectors now that segments are loaded
    for (uint16_t i = 1; i < NE_MAX_EXPORTS; i++) {
        if (mod->exports[i].segIndex > 0 &&
            mod->exports[i].segIndex <= mod->segmentCount) {
            mod->exports[i].selector = mod->segments[mod->exports[i].segIndex - 1].selector;
        }
    }

    // Process relocations for each segment
    for (uint16_t i = 0; i < mod->segmentCount; i++) {
        if (segTable[i].flags & NE_SEGF_HASRELOC) {
            if (!processRelocations(mod, i, fp, resolver)) {
                logErr("neload: relocation failed for segment %u\n", i + 1);
                return false;
            }
        }
    }

    return true;
}


static bool allocateSegment(NeModuleT *mod, int segIdx, uint32_t size, bool isCode)
{
    LoadedSegT *seg = &mod->segments[segIdx];

    // Allocate memory using DJGPP's malloc (extended memory, flat model)
    // The memory is accessible via the flat DS selector, but we also need
    // a 16-bit selector pointing to it.
    uint8_t *mem = (uint8_t *)calloc(1, size);
    if (!mem) {
        logErr("neload: failed to allocate %" PRIu32 " bytes for segment %u\n", size, segIdx + 1);
        return false;
    }

    // In DJGPP, pointer values are offsets from the DS base.
    // The true linear address = pointer + __djgpp_base_address.
    // We store the pointer value (for C access) but use the linear
    // address when setting up the LDT descriptor base.
    uint32_t ptrVal    = (uint32_t)mem;
    uint32_t linearAddr = ptrVal + __djgpp_base_address;

    // Create a 16-bit LDT descriptor for this segment
    uint16_t sel = makeDescriptor16(linearAddr, size - 1, isCode);
    if (sel == 0) {
        free(mem);
        return false;
    }

    seg->linearAddr = ptrVal;  // Store DJGPP pointer (for C access via cast)
    seg->selector   = sel;
    seg->size       = size;
    seg->isCode     = isCode;

    return true;
}


static uint16_t makeDescriptor16(uint32_t base, uint32_t limit, bool isCode)
{
    int sel = __dpmi_allocate_ldt_descriptors(1);
    if (sel < 0) {
        logErr("neload: failed to allocate LDT descriptor\n");
        return 0;
    }

    if (__dpmi_set_segment_base_address(sel, base) < 0) {
        logErr("neload: failed to set segment base\n");
        __dpmi_free_ldt_descriptor(sel);
        return 0;
    }

    if (__dpmi_set_segment_limit(sel, limit) < 0) {
        logErr("neload: failed to set segment limit\n");
        __dpmi_free_ldt_descriptor(sel);
        return 0;
    }

    // Set access rights for 16-bit segment
    // Code: present, DPL 3, code, readable, non-conforming = 0xFA
    // Data: present, DPL 3, data, writable = 0xF2
    // High byte: G=0, D=0 (16-bit), 0, AVL=0 = 0x00
    uint16_t rights = isCode ? 0x00FA : 0x00F2;
    if (__dpmi_set_descriptor_access_rights(sel, rights) < 0) {
        logErr("neload: failed to set access rights (0x%04X)\n", rights);
        __dpmi_free_ldt_descriptor(sel);
        return 0;
    }

    return (uint16_t)sel;
}


static bool loadSegmentData(NeModuleT *mod, int segIdx, FILE *fp, uint32_t fileOffset, uint32_t fileSize)
{
    LoadedSegT *seg = &mod->segments[segIdx];

    fseek(fp, fileOffset, SEEK_SET);

    // Read directly into the allocated memory (flat model, so pointer works)
    uint8_t *dest = (uint8_t *)seg->linearAddr;
    if (fread(dest, 1, fileSize, fp) != fileSize) {
        logErr("neload: short read loading segment %u data\n", segIdx + 1);
        return false;
    }

    return true;
}


static bool processRelocations(NeModuleT *mod, int segIdx, FILE *fp, ImportResolverT resolver)
{
    LoadedSegT *seg = &mod->segments[segIdx];

    // Relocation data follows the segment data in the file.
    // The segment table entry gives us the file offset; relocation data
    // starts at fileOffset + fileLength.
    uint32_t segTableOff = mod->neHeaderFileOffset + mod->neHeader.segmentTableOffset;
    fseek(fp, segTableOff + segIdx * sizeof(NeSegEntryT), SEEK_SET);

    NeSegEntryT se;
    if (fread(&se, sizeof(se), 1, fp) != 1) {
        return false;
    }

    uint32_t fileOffset = (uint32_t)se.fileSectorOffset << mod->sectorAlignShift;
    uint32_t fileLen    = se.fileLength;
    if (fileLen == 0 && se.fileSectorOffset != 0) {
        fileLen = 0x10000;
    }

    // Relocation records follow the segment data
    uint32_t relocOff = fileOffset + fileLen;
    fseek(fp, relocOff, SEEK_SET);

    // First word is the count of relocation records
    uint16_t relocCount;
    if (fread(&relocCount, 2, 1, fp) != 1) {
        return false;
    }

    dbgPrint("neload: segment %u has %u relocations\n", segIdx + 1, relocCount);

    uint8_t *segData = (uint8_t *)seg->linearAddr;

    for (uint16_t i = 0; i < relocCount; i++) {
        NeRelocT rec;
        if (fread(&rec, sizeof(rec), 1, fp) != 1) {
            logErr("neload: failed to read relocation %u/%u\n", i + 1, relocCount);
            return false;
        }

        uint8_t targetType = rec.flags & NE_RELF_TARGET_MASK;
        bool    additive   = (rec.flags & NE_RELF_ADDITIVE) != 0;

        // Resolve the target address
        uint16_t targetSel = 0;
        uint16_t targetOff = 0;
        bool     resolved  = false;

        switch (targetType) {
            case NE_RELF_INTERNALREF: {
                // Internal reference: target1 = segment index (1-based)
                // For moveable segments, target2 is an entry table ordinal.
                // For fixed segments, target2 is the offset.
                uint16_t tSegIdx = rec.target1;
                if (rec.target1 == 0xFF) {
                    // Moveable reference via entry table
                    uint16_t ordinal = rec.target2;
                    if (ordinal > 0 && ordinal < NE_MAX_EXPORTS &&
                        mod->exports[ordinal].segIndex > 0) {
                        tSegIdx   = mod->exports[ordinal].segIndex;
                        targetOff = mod->exports[ordinal].offset;
                        targetSel = mod->segments[tSegIdx - 1].selector;
                        resolved  = true;
                    }
                } else if (tSegIdx > 0 && tSegIdx <= mod->segmentCount) {
                    targetSel = mod->segments[tSegIdx - 1].selector;
                    targetOff = rec.target2;
                    resolved  = true;
                }
                break;
            }

            case NE_RELF_IMPORTORD: {
                // Import by ordinal: target1 = module ref index (1-based)
                //                    target2 = ordinal number
                uint16_t modIdx  = rec.target1;
                uint16_t ordinal = rec.target2;

                if (modIdx > 0 && modIdx <= mod->modRefCount && resolver) {
                    FarPtr16T addr = resolver(mod->modRefNames[modIdx - 1], ordinal, NULL);
                    if (addr.segment != 0 || addr.offset != 0) {
                        targetSel = addr.segment;
                        targetOff = addr.offset;
                        resolved  = true;
                    }
                    dbgPrint("neload: RELOC seg %u off 0x%04X srcType=%u: %s.%u -> %04X:%04X\n",
                             segIdx + 1, rec.srcOffset, rec.srcType,
                             mod->modRefNames[modIdx - 1], ordinal,
                             targetSel, targetOff);
                }

                if (!resolved) {
                    dbgPrint("neload: UNRESOLVED import %s.%u in seg %u at 0x%04X\n",
                             (modIdx > 0 && modIdx <= mod->modRefCount) ?
                             mod->modRefNames[modIdx - 1] : "???",
                             ordinal, segIdx + 1, rec.srcOffset);
                    // Patch in a dummy value (INT 3 / breakpoint)
                    targetSel = mod->segments[0].selector; // Point to first code seg
                    targetOff = 0;
                    resolved  = true;
                }
                break;
            }

            case NE_RELF_IMPORTNAME: {
                // Import by name: target1 = module ref index (1-based)
                //                 target2 = offset into imported names table
                uint16_t modIdx    = rec.target1;
                uint16_t nameOff16 = rec.target2;

                // Read the function name from the imported names table
                char funcName[64] = "";
                uint32_t importNameTableOff = mod->neHeaderFileOffset +
                                              mod->neHeader.importNameTableOffset;
                long savedPos = ftell(fp);
                fseek(fp, importNameTableOff + nameOff16, SEEK_SET);

                uint8_t nameLen;
                if (fread(&nameLen, 1, 1, fp) == 1 && nameLen < 64) {
                    fread(funcName, 1, nameLen, fp);
                    funcName[nameLen] = '\0';
                }
                fseek(fp, savedPos, SEEK_SET);

                if (modIdx > 0 && modIdx <= mod->modRefCount && resolver) {
                    FarPtr16T addr = resolver(mod->modRefNames[modIdx - 1], 0, funcName);
                    if (addr.segment != 0 || addr.offset != 0) {
                        targetSel = addr.segment;
                        targetOff = addr.offset;
                        resolved  = true;
                    }
                }

                if (!resolved) {
                    dbgPrint("neload: UNRESOLVED import %s.%s in seg %u at 0x%04X\n",
                             (modIdx > 0 && modIdx <= mod->modRefCount) ?
                             mod->modRefNames[modIdx - 1] : "???",
                             funcName, segIdx + 1, rec.srcOffset);
                    targetSel = mod->segments[0].selector;
                    targetOff = 0;
                    resolved  = true;
                }
                break;
            }

            case NE_RELF_OSFIXUP: {
                // OS fixup (floating point emulation, etc.)
                // target1 = fixup type (1=FIARQQ, 2=FJARQQ, etc.)
                // We just patch in NOPs or a far return.
                targetSel = mod->segments[0].selector;
                targetOff = 0;
                resolved  = true;
                dbgPrint("neload: OS fixup type %u at seg %u offset 0x%04X\n",
                         rec.target1, segIdx + 1, rec.srcOffset);
                break;
            }
        }

        if (!resolved) {
            logErr("neload: failed to resolve reloc in seg %u at 0x%04X\n",
                    segIdx + 1, rec.srcOffset);
            continue;
        }

        // Apply the fixup to the segment data.
        // NE relocations can be chained: the word at srcOffset contains
        // the offset of the next fixup location (forming a linked list),
        // UNLESS the relocation is additive.
        uint32_t fixupOff = rec.srcOffset;

        if (additive) {
            // Single fixup, add to existing value
            switch (rec.srcType) {
                case NE_RELOC_LOBYTE:
                    if (fixupOff < seg->size) {
                        segData[fixupOff] += (uint8_t)targetOff;
                    }
                    break;
                case NE_RELOC_OFFSET:
                    if (fixupOff + 1 < seg->size) {
                        uint16_t *p = (uint16_t *)(segData + fixupOff);
                        *p += targetOff;
                    }
                    break;
                case NE_RELOC_SEGMENT:
                    if (fixupOff + 1 < seg->size) {
                        uint16_t *p = (uint16_t *)(segData + fixupOff);
                        *p += targetSel;
                    }
                    break;
                case NE_RELOC_FAR_ADDR:
                    if (fixupOff + 3 < seg->size) {
                        uint16_t *pOff = (uint16_t *)(segData + fixupOff);
                        uint16_t *pSeg = (uint16_t *)(segData + fixupOff + 2);
                        *pOff += targetOff;
                        *pSeg += targetSel;
                    }
                    break;
                case NE_RELOC_OFFSET32:
                    if (fixupOff + 3 < seg->size) {
                        uint32_t *p = (uint32_t *)(segData + fixupOff);
                        *p += ((uint32_t)targetSel << 16) | targetOff;
                    }
                    break;
            }
        } else {
            // Chained fixups: follow the linked list
            int chainLimit = 4096; // Safety limit
            int chainCount = 0;
            while (fixupOff != 0xFFFF && chainLimit-- > 0) {
                if (fixupOff + 1 >= seg->size) {
                    break;
                }

                uint16_t nextOff;
                chainCount++;

                switch (rec.srcType) {
                    case NE_RELOC_LOBYTE:
                        if (fixupOff < seg->size) {
                            nextOff = segData[fixupOff]; // Next in chain
                            segData[fixupOff] = (uint8_t)targetOff;
                        } else {
                            nextOff = 0xFFFF;
                        }
                        break;

                    case NE_RELOC_OFFSET: {
                        uint16_t *p = (uint16_t *)(segData + fixupOff);
                        nextOff = *p;
                        *p = targetOff;
                        break;
                    }

                    case NE_RELOC_SEGMENT: {
                        uint16_t *p = (uint16_t *)(segData + fixupOff);
                        nextOff = *p;
                        *p = targetSel;
                        break;
                    }

                    case NE_RELOC_FAR_ADDR: {
                        if (fixupOff + 3 >= seg->size) {
                            nextOff = 0xFFFF;
                            break;
                        }
                        uint16_t *pOff = (uint16_t *)(segData + fixupOff);
                        uint16_t *pSeg = (uint16_t *)(segData + fixupOff + 2);
                        nextOff = *pOff; // Chain is in offset field
                        *pOff = targetOff;
                        *pSeg = targetSel;
                        break;
                    }

                    case NE_RELOC_OFFSET32: {
                        if (fixupOff + 3 >= seg->size) {
                            nextOff = 0xFFFF;
                            break;
                        }
                        uint16_t *p16 = (uint16_t *)(segData + fixupOff);
                        nextOff = *p16;
                        uint32_t *p32 = (uint32_t *)(segData + fixupOff);
                        *p32 = ((uint32_t)targetSel << 16) | targetOff;
                        break;
                    }

                    default:
                        dbgPrint("neload: unknown reloc srcType 0x%02X\n", rec.srcType);
                        nextOff = 0xFFFF;
                        break;
                }

                fixupOff = nextOff;
            }

            if (chainCount > 1) {
                dbgPrint("neload:   chain: %d links patched\n", chainCount);
            }
        }
    }

    return true;
}


static void freeSegment(LoadedSegT *seg)
{
    if (seg->selector != 0) {
        __dpmi_free_ldt_descriptor(seg->selector);
        seg->selector = 0;
    }
    if (seg->linearAddr != 0) {
        free((void *)seg->linearAddr);
        seg->linearAddr = 0;
    }
    seg->size = 0;
}


bool neExtendSegment(NeModuleT *mod, int segIdx, uint32_t extraSize, uint32_t *oldSizeOut)
{
    if (segIdx < 0 || segIdx >= mod->segmentCount) {
        return false;
    }

    LoadedSegT *seg = &mod->segments[segIdx];
    uint32_t oldSize = seg->size;
    uint32_t newSize = oldSize + extraSize;

    // 16-bit segments are limited to 64K
    if (newSize > 0x10000) {
        logErr("neload: cannot extend segment %d beyond 64K (old=%" PRIu32 " extra=%" PRIu32 ")\n",
               segIdx + 1, oldSize, extraSize);
        return false;
    }

    uint8_t *newMem = (uint8_t *)realloc((void *)seg->linearAddr, newSize);
    if (!newMem) {
        logErr("neload: realloc failed extending segment %d\n", segIdx + 1);
        return false;
    }

    // Zero the new space
    memset(newMem + oldSize, 0, extraSize);

    uint32_t newPtrVal  = (uint32_t)newMem;
    uint32_t newLinAddr = newPtrVal + __djgpp_base_address;

    seg->linearAddr = newPtrVal;
    seg->size       = newSize;

    // Update LDT descriptor base (may have moved) and limit
    __dpmi_set_segment_base_address(seg->selector, newLinAddr);
    __dpmi_set_segment_limit(seg->selector, newSize - 1);

    if (oldSizeOut) {
        *oldSizeOut = oldSize;
    }

    return true;
}


// Enable debug output for the NE loader
void neSetDebug(bool enable)
{
    gDebug = enable;
}