lx_loader.c

#define _GNU_SOURCE 1

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdint.h>
#include <errno.h>
#include <sys/mman.h>
#include <assert.h>
#include <dlfcn.h>
#include <dirent.h>
#include <pthread.h>
#include <signal.h>
#include <ucontext.h>

// 16-bit selector kernel nonsense...
#include <sys/syscall.h>
#include <sys/types.h>
#include <asm/ldt.h>

#include "lx_loader.h"

static LxLoaderState _GLoaderState;
static LxLoaderState *GLoaderState = &_GLoaderState;
static uint8 GMainTibSpace[LXTIBSIZE];

// !!! FIXME: move this into an lx_common.c file.
static int sanityCheckLxModule(uint8 **_exe, uint32 *_exelen)
{
    if (*_exelen < 196) {
        fprintf(stderr, "not an OS/2 LX module\n");
        return 0;
    }
    const uint32 header_offset = *((uint32 *) (*_exe + 0x3C));
    //printf("header offset is %u\n", (uint) header_offset);
    if ((header_offset + sizeof (LxHeader)) >= *_exelen) {
        fprintf(stderr, "not an OS/2 LX module\n");
        return 0;
    }

    *_exe += header_offset;  // skip the DOS stub, etc.
    *_exelen -= header_offset;

    const LxHeader *lx = (const LxHeader *) *_exe;

    if ((lx->magic_l != 'L') || (lx->magic_x != 'X')) {
        fprintf(stderr, "not an OS/2 LX module\n");
        return 0;
    }

    if ((lx->byte_order != 0) || (lx->word_order != 0)) {
        fprintf(stderr, "Program is not little-endian!\n");
        return 0;
    }

    if (lx->lx_version != 0) {
        fprintf(stderr, "Program is unknown LX module version (%u)\n", (uint) lx->lx_version);
        return 0;
    }

    if (lx->cpu_type > 3) { // 1==286, 2==386, 3==486
        fprintf(stderr, "Program needs unknown CPU type (%u)\n", (uint) lx->cpu_type);
        return 0;
    }

    if (lx->os_type != 1) { // 1==OS/2, others: dos4, windows, win386, unknown.
        fprintf(stderr, "Program needs unknown OS type (%u)\n", (uint) lx->os_type);
        return 0;
    }

    if (lx->page_size != 4096) {
        fprintf(stderr, "Program page size isn't 4096 (%u)\n", (uint) lx->page_size);
        return 0;
    }

    if (lx->module_flags & 0x2000) {
        fprintf(stderr, "Module is flagged as not-loadable\n");
        return 0;
    }

    // !!! FIXME: check if EIP and ESP are non-zero vs per-process library bits, etc.

    return 1;
} // sanityCheckLxModule

static char *makeOS2Path(const char *fname)
{
    char *full = realpath(fname, NULL);
    if (!full)
        return NULL;

    char *retval = (char *) malloc(strlen(full) + 3);
    if (!retval)
        return NULL;

    retval[0] = 'C';
    retval[1] = ':';
    strcpy(retval + 2, full);
    free(full);
    for (char *ptr = retval + 2; *ptr; ptr++) {
        if (*ptr == '/')
            *ptr = '\\';
    } // for

    return retval;
} // makeOS2Path

// based on case-insensitive search code from PhysicsFS:
//    https://icculus.org/physfs/
//  It's also zlib-licensed, plus I wrote it.  :)  --ryan.
// !!! FIXME: this doesn't work as-is for UTF-8 case folding, since string
// !!! FIXNE:  length can change!
static int locateOneElement(char *buf)
{
    if (access(buf, F_OK) == 0)
        return 1;  // quick rejection: exists in current case.

    DIR *dirp;
    char *ptr = strrchr(buf, '/');  // find entry at end of path.
    if (ptr == NULL) {
        dirp = opendir(".");
        ptr = buf;
    } else if (ptr == buf) {
        dirp = opendir("/");
    } else {
        *ptr = '\0';
        dirp = opendir(buf);
        *ptr = '/';
        ptr++;  // point past dirsep to entry itself.
    } // else

    for (struct dirent *dent = readdir(dirp); dent; dent = readdir(dirp)) {
        if (strcasecmp(dent->d_name, ptr) == 0) {
            strcpy(ptr, dent->d_name); // found a match. Overwrite with this case.
            closedir(dirp);
            return 1;
        } // if
    } // for

    // no match at all...
    closedir(dirp);
    return 0;
} // locateOneElement

static int locatePathCaseInsensitive(char *buf)
{
    int rc;
    char *ptr = buf;

    if (*ptr == '\0')
        return 0;  // Uh...I guess that's success?

    if (access(buf, F_OK) == 0)
        return 0;  // quick rejection: exists in current case.

    while ( (ptr = strchr(ptr + 1, '/')) != NULL ) {
        *ptr = '\0';  // block this path section off
        rc = locateOneElement(buf);
        *ptr = '/'; // restore path separator
        if (!rc)
            return -2;  // missing element in path.
    } // while

    // check final element...
    return locateOneElement(buf) ? 0 : -1;
} // locatePathCaseInsensitive

static char *makeUnixPath(const char *os2path, uint32 *err)
{
    if ((strcasecmp(os2path, "NUL") == 0) || (strcasecmp(os2path, "\\DEV\\NUL") == 0))
        os2path = "/dev/null";
    // !!! FIXME: emulate other OS/2 device names (CON, etc).
    //else if (strcasecmp(os2path, "CON") == 0)
    else {
        char drive = os2path[0];
        if ((drive >= 'a') && (drive <= 'z'))
            drive += 'A' - 'a';

        if ((drive >= 'A') && (drive <= 'Z')) {
            if (os2path[1] == ':') {  // it's a drive letter.
                if (drive == 'C')
                    os2path += 2;  // skip "C:" if it's there.
                else {
                    *err = 26; //ERROR_NOT_DOS_DISK;
                    return NULL;
                } // else
            } // if
        } // if
    } // else

    const size_t len = strlen(os2path);
    char *retval = (char *) malloc(len + 1);
    if (!retval) {
        *err = 8;  //ERROR_NOT_ENOUGH_MEMORY;
        return NULL;
    } // else

    strcpy(retval, os2path);

    for (char *ptr = strchr(retval, '\\'); ptr; ptr = strchr(ptr + 1, '\\'))
        *ptr = '/';  // convert to Unix-style path separators.

    locatePathCaseInsensitive(retval);

    return retval;
} // makeUnixPath


/* this algorithm is from lxlite 138u. */
static int decompressExePack2(uint8 *dst, const uint32 dstlen, const uint8 *src, const uint32 srclen)
{
    uint32 sOf = 0;
    uint32 dOf = 0;
    uint32 bOf = 0;
    uint32 b1 = 0;
    uint32 b2 = 0;

    #define SRCAVAIL(n) ((sOf + (n)) <= srclen)
    #define DSTAVAIL(n) ((dOf + (n)) <= dstlen)

    do {
        if (!SRCAVAIL(1))
            break;

        b1 = src[sOf];
        switch (b1 & 3) {
            case 0:
                if (b1 == 0) {
                    if (SRCAVAIL(2)) {
                        if (src[sOf + 1] == 0) {
                            sOf += 2;
                            break;
                        } else if (SRCAVAIL(3) && DSTAVAIL(src[sOf + 1])) {
                            memset(dst + dOf, src[sOf + 2], src[sOf + 1]);
                            sOf += 3;
                            dOf += src[sOf - 2];
                        } else {
                            return 0;
                        }
                    } else {
                        return 0;
                    }
                } else if (SRCAVAIL((b1 >> 2) + 1) && DSTAVAIL(b1 >> 2)) {
                    memcpy(dst + dOf, src + (sOf + 1), b1 >> 2);
                    dOf += b1 >> 2;
                    sOf += (b1 >> 2) + 1;
                } else {
                    return 0;
                }
                break;

            case 1:
                if (!SRCAVAIL(2))
                    return 0;
                bOf = (*((const uint16 *) (src + sOf))) >> 7;
                b2 = ((b1 >> 4) & 7) + 3;
                b1 = ((b1 >> 2) & 3);
                sOf += 2;
                if (SRCAVAIL(b1) && DSTAVAIL(b1 + b2) && (dOf + b1 - bOf >= 0)) {
                    memcpy(dst + dOf, src + sOf, b1);
                    dOf += b1;
                    sOf += b1;
                    memmove(dst + dOf, dst + (dOf - bOf), b2);
                    dOf += b2;
                } else {
                    return 0;
                } // else
                break;

            case 2:
                if (!SRCAVAIL(2))
                    return 0;
                bOf = (*((const uint16 *) (src + sOf))) >> 4;
                b1 = ((b1 >> 2) & 3) + 3;
                if (DSTAVAIL(b1) && (dOf - bOf >= 0)) {
                    memmove(dst + dOf, dst + (dOf - bOf), b1);
                    dOf += b1;
                    sOf += 2;
                } else {
                    return 0;
                } // else
                break;

            case 3:
                if (!SRCAVAIL(3))
                    return 0;
                b2 = ((*((const uint16 *) (src + sOf))) >> 6) & 0x3F;
                b1 = (src[sOf] >> 2) & 0x0F;
                bOf = (*((const uint16 *) (src + (sOf + 1)))) >> 4;
                sOf += 3;
                if (SRCAVAIL(b1) && DSTAVAIL(b1 + b2) && (dOf + b1 - bOf >= 0))
                {
                    memcpy(dst + dOf, src + sOf, b1);
                    dOf += b1;
                    sOf += b1;
                    memmove(dst + dOf, dst + (dOf - bOf), b2);
                    dOf += b2;
                } else {
                    return 0;
                } // else
                break;
        } // switch
    } while (dOf < dstlen);
    #undef SRCAVAIL
    #undef DSTAVAIL

    // pad out the rest of the page with zeroes.
    if ((dstlen - dOf) > 0)
        memset(dst + dOf, '\0', dstlen - dOf);

    return 1;
} // decompressExePack2

static int decompressIterated(uint8 *dst, uint32 dstlen, const uint8 *src, uint32 srclen)
{
    while (srclen) {
        if (srclen < 4)
            return 0;
        const uint16 iterations = *((uint16 *) src); src += 2;
        const uint16 len = *((uint16 *) src); src += 2;
        srclen -= 4;
        if (dstlen < (iterations * len))
            return 0;
        else if (srclen < len)
            return 0;

        for (uint16 i = 0; i < iterations; i++) {
            memcpy(dst, src, len);
            dst += len;
            dstlen -= len;
        } // for

        src += len;
        srclen -= len;
    } // while

    // pad out the rest of the page with zeroes.
    if (dstlen > 0)
        memset(dst, '\0', dstlen);

    return 1;
} // decompressIterated


static void missingEntryPointCalled(const char *module, const char *entry)
{
    void ***ebp = NULL;
    __asm__ __volatile__ ( "movl %%ebp, %%eax  \n\t" : "=a" (ebp) );
    void *caller = ebp[0][1];

    fflush(stdout);
    fflush(stderr);
    fprintf(stderr, "\n\nMissing entry point '%s' in module '%s' called at %p!\n", entry, module, caller);
    fprintf(stderr, "Aborting.\n\n\n");
    //STUBBED("output backtrace");
    fflush(stderr);
    _exit(1);
} // missing_ordinal_called

static void *generateMissingTrampoline(const char *_module, const char *_entry)
{
    static void *page = NULL;
    static uint32 pageused = 0;
    static uint32 pagesize = 0;

    if (pagesize == 0)
        pagesize = getpagesize();

    if ((!page) || ((pagesize - pageused) < 32))
    {
        if (page)
            mprotect(page, pagesize, PROT_READ | PROT_EXEC);
        page = valloc(pagesize);
        mprotect(page, pagesize, PROT_READ | PROT_WRITE | PROT_EXEC);
        pageused = 0;
    } // if

    void *trampoline = page + pageused;
    char *ptr = (char *) trampoline;
    char *module = strdup(_module);
    char *entry = strdup(_entry);

    *(ptr++) = 0x55;  // pushl %ebp
    *(ptr++) = 0x89;  // movl %esp,%ebp
    *(ptr++) = 0xE5;  //   ...movl %esp,%ebp
    *(ptr++) = 0x68;  // pushl immediate
    memcpy(ptr, &entry, sizeof (char *));
    ptr += sizeof (uint32);
    *(ptr++) = 0x68;  // pushl immediate
    memcpy(ptr, &module, sizeof (char *));
    ptr += sizeof (uint32);
    *(ptr++) = 0xB8;  // movl immediate to %eax
    const void *fn = missingEntryPointCalled;
    memcpy(ptr, &fn, sizeof (void *));
    ptr += sizeof (void *);
    *(ptr++) = 0xFF;  // call absolute in %eax.
    *(ptr++) = 0xD0;  //   ...call absolute in %eax.

    const uint32 trampoline_len = (uint32) (ptr - ((char *) trampoline));
    assert(trampoline_len <= 32);
    pageused += trampoline_len;

    if (pageused % 4)  // keep these aligned to 32 bits.
        pageused += (4 - (pageused % 4));

    //printf("Generated trampoline %p for module '%s' export '%s'\n", trampoline, module, entry);

    return trampoline;
} // generateMissingTrampoline


// OS/2 threads keep their Thread Information Block at FS:0x0000, so we have
//  to ask the Linux kernel to screw around with 16-bit selectors on our
//  behalf so we don't crash out when apps try to access it directly.
// OS/2 provides a C-callable API to obtain the (32-bit linear!) TIB address
//  without going directly to the FS register, but lots of programs (including
//  the EMX runtime) touch the register directly, so we have to deal with it.
// You must call this once for each thread that will go into LX land, from
//  that thread, as soon as possible after starting.
static uint16 initOs2Tib(uint8 *tibspace, void *_topOfStack, const size_t stacklen, const uint32 tid)
{
    uint8 *topOfStack = (uint8 *) _topOfStack;

    LxTIB *tib = (LxTIB *) tibspace;
    LxTIB2 *tib2 = (LxTIB2 *) (tib + 1);

    FIXME("This is probably 50% wrong");
    tib->tib_pexchain = NULL;
    tib->tib_pstack = topOfStack - stacklen;
    tib->tib_pstacklimit = (void *) topOfStack;
    tib->tib_ptib2 = tib2;
    tib->tib_version = 20;  // !!! FIXME
    tib->tib_ordinal = 79;  // !!! FIXME

    tib2->tib2_ultid = tid;
    tib2->tib2_ulpri = 512;
    tib2->tib2_version = 20;
    tib2->tib2_usMCCount = 0;
    tib2->tib2_fMCForceFlag = 0;

    // !!! FIXME: I barely know what I'm doing here, this could all be wrong.
    struct user_desc entry;
    entry.entry_number = -1;
    entry.base_addr = (unsigned int) ((size_t)tib);
    entry.limit = LXTIBSIZE;
    entry.seg_32bit = 1;
    entry.contents = MODIFY_LDT_CONTENTS_DATA;
    entry.read_exec_only = 0;
    entry.limit_in_pages = 0;
    entry.seg_not_present = 0;
    entry.useable = 1;
    const long rc = syscall(SYS_set_thread_area, &entry);
    assert(rc == 0);  FIXME("this can legit fail, though!");

    // I have no idea why this needs the "<< 3 | 3", but it's probably
    //  specified in the Intel manuals. I got this from looking at how
    //  Wine does it. I still don't know why.
    const unsigned int segment = (entry.entry_number << 3) | 3;
    __asm__ __volatile__ ( "movw %%ax, %%fs  \n\t" : : "a" (segment) );
    return (uint16) entry.entry_number;
} // initOs2Tib

static void deinitOs2Tib(const uint16 selector)
{
    // !!! FIXME: I barely know what I'm doing here, this could all be wrong.
    struct user_desc entry;
    memset(&entry, '\0', sizeof (entry));
    entry.entry_number = selector;
    entry.read_exec_only = 1;
    entry.seg_not_present = 1;

    const long rc = syscall(SYS_set_thread_area, &entry);
    assert(rc == 0);  FIXME("this can legit fail, though!");
} // deinitOs2Tib


static __attribute__((noreturn)) void runLxModule(LxModule *lxmod, const int argc, char **argv, char **envp)
{
    uint8 *stack = (uint8 *) ((size_t) lxmod->esp);

    // ...and you pass it the pointer to argv0. This is (at least as far as the docs suggest) appended to the environment table.
    fprintf(stderr, "jumping into LX land for exe '%s'...! eip=%p esp=%p\n", lxmod->name, (void *) lxmod->eip, stack); fflush(stderr);

    GLoaderState->running = 1;

    __asm__ __volatile__ (
        "movl %%esi,%%esp  \n\t"  // use the OS/2 process's stack.
        "pushl %%eax       \n\t"  // cmd
        "pushl %%ecx       \n\t"  // env
        "pushl $0          \n\t"  // reserved
        "pushl %%edx       \n\t"  // module handle
        "leal 1f,%%eax     \n\t"  // address that entry point should return to.
        "pushl %%eax       \n\t"
        "pushl %%edi       \n\t"  // the OS/2 process entry point (we'll "ret" to it instead of jmp, so stack and registers are all correct).
        "xorl %%eax,%%eax  \n\t"
        "xorl %%ebx,%%ebx  \n\t"
        "xorl %%ecx,%%ecx  \n\t"
        "xorl %%edx,%%edx  \n\t"
        "xorl %%esi,%%esi  \n\t"
        "xorl %%edi,%%edi  \n\t"
        "xorl %%ebp,%%ebp  \n\t"
        "ret               \n\t"  // go to OS/2 land!
        "1:                \n\t"  //  ...and return here.
        "andl $-16, %%esp  \n\t"  // align the stack for macOS.
        "subl $-4, %%esp  \n\t"   // align the stack for macOS.
        "pushl %%eax       \n\t"  // call _exit() with whatever is in %eax.
        "call _exit        \n\t"
            : // no outputs
            : "a" (GLoaderState->pib.pib_pchcmd),
              "c" (GLoaderState->pib.pib_pchenv),
              "d" (lxmod), "S" (stack), "D" (lxmod->eip)
            : "memory"
    );

    __builtin_unreachable();
} // runLxModule

static void runLxLibraryInitOrTerm(LxModule *lxmod, const int isTermination)
{
    uint8 *stack = NULL;

    // force us over to OS/2 main module's stack if we aren't already on it.
    if (!GLoaderState->running)
        stack = (uint8 *) ((size_t) GLoaderState->main_module->esp);

    fprintf(stderr, "jumping into LX land to %s library '%s'...! eip=%p esp=%p\n", isTermination ? "terminate" : "initialize", lxmod->name, (void *) lxmod->eip, stack); fflush(stderr);

    __asm__ __volatile__ (
        "pushal            \n\t"  // save all the current registers.
        "pushfl            \n\t"  // save all the current flags.
        "movl %%esp,%%ecx  \n\t"  // save our stack to a temporary register.
        "testl %%esi,%%esi \n\t"  // force the OS/2 process's stack?
        "je 1f             \n\t"  // if 0, nope, we're already good.
        "movl %%esi,%%esp  \n\t"  // use the OS/2 process's stack.
        "1:                \n\t"  //
        "pushl %%ecx       \n\t"  // save original stack pointer for real.
        "pushl %%eax       \n\t"  // isTermination
        "pushl %%edx       \n\t"  // library module handle
        "leal 2f,%%eax     \n\t"  // address that entry point should return to.
        "pushl %%eax       \n\t"
        "pushl %%edi       \n\t"  // the OS/2 library entry point (we'll "ret" to it instead of jmp, so stack and registers are all correct).
        "xorl %%eax,%%eax  \n\t"
        "xorl %%ebx,%%ebx  \n\t"
        "xorl %%ecx,%%ecx  \n\t"
        "xorl %%edx,%%edx  \n\t"
        "xorl %%esi,%%esi  \n\t"
        "xorl %%edi,%%edi  \n\t"
        "xorl %%ebp,%%ebp  \n\t"
        "ret               \n\t"  // go to OS/2 land!
        "2:                \n\t"  //  ...and return here.
        "addl $8,%%esp     \n\t"  // drop arguments to entry point.
        "popl %%esp        \n\t"  // restore native process stack now.
        "popfl             \n\t"  // restore our original flags.
        "popal             \n\t"  // restore our original registers.
            : // no outputs
            : "a" (isTermination), "d" (lxmod), "S" (stack), "D" (lxmod->eip)
            : "memory"
    );

    fprintf(stderr, "...survived time in LX land!\n"); fflush(stderr);

    // !!! FIXME: this entry point returns a result...do we abort if it reports error?
    // !!! FIXME: (actually, DosLoadModule() can report that failure. Abort if (GLoaderState->running == 0), though!)
} // runLxLibraryInitOrTerm

static void runLxLibraryInit(LxModule *lxmod)
{
    // we don't check the LIBINIT flag, because if the EIP fields are valid
    //  but this bit is missing, we're supposed to do "global" initialization,
    //  which I guess means it runs once for all processes on the system
    //  instead of once per process...but we aren't really a full OS/2 system
    //  so maybe it's okay to do global init in isolation...? We'll cross that
    //  bridge when we come to it, I guess. Either way: this is running here,
    //  flag or not.
    if (1) { //if (lxmod->module_flags & 0x4) {  // LIBINIT flag
        if (lxmod->lx.eip_object != 0)
            runLxLibraryInitOrTerm(lxmod, 0);
    } // if
} // runLxLibraryInit

static void runLxLibraryTerm(LxModule *lxmod)
{
    // See notes about global initialization in runLxLibraryInit(); it
    //  applies to deinit here, too.
    if (1) { //if (lxmod->module_flags & 0x40000000) {  // LIBTERM flag
        if (lxmod->lx.eip_object != 0)
            runLxLibraryInitOrTerm(lxmod, 1);
    } // if
} // runLxLibraryTerm

static void freeLxModule(LxModule *lxmod)
{
    if (!lxmod)
        return;

    // !!! FIXME: mutex from here
    lxmod->refcount--;
    fprintf(stderr, "unref'd module '%s' to %u\n", lxmod->name, (uint) lxmod->refcount);
    if (lxmod->refcount > 0)
        return;  // something is still using it.

    if (lxmod->initialized) {
        if (!lxmod->nativelib) {
            runLxLibraryTerm(lxmod);
        } else {
            LxNativeModuleDeinitEntryPoint fn = (LxNativeModuleDeinitEntryPoint) dlsym(lxmod->nativelib, "lxNativeModuleDeinit");
            if (fn)
                fn();
        } // else
    } // if

    if (lxmod->next)
        lxmod->next->prev = lxmod->prev;

    if (lxmod->prev)
        lxmod->prev->next = lxmod->next;

    if (lxmod == GLoaderState->loaded_modules)
        GLoaderState->loaded_modules = lxmod->next;

    if (GLoaderState->main_module == lxmod)
        GLoaderState->main_module = NULL;
    // !!! FIXME: mutex to here

    for (uint32 i = 0; i < lxmod->lx.num_import_mod_entries; i++)
        freeLxModule(lxmod->dependencies[i]);
    free(lxmod->dependencies);

    for (uint32 i = 0; i < lxmod->lx.module_num_objects; i++) {
        if (lxmod->mmaps[i].addr)
            munmap(lxmod->mmaps[i].addr, lxmod->mmaps[i].size);
    } // for
    free(lxmod->mmaps);    

    if (lxmod->nativelib)
        dlclose(lxmod->nativelib);
    else {
        for (uint32 i = 0; i < lxmod->num_exports; i++)
            free((void *) lxmod->exports[i].name);
        free((void *) lxmod->exports);
    } // else

    free(lxmod);
} // freeLxModule

static LxModule *loadLxModuleByModuleNameInternal(const char *modname, const int dependency_tree_depth);

static void *getModuleProcAddrByOrdinal(const LxModule *module, const uint32 ordinal)
{
    //printf("lookup module == '%s', ordinal == %u\n", module->name, (uint) ordinal);

    const LxExport *lxexp = module->exports;
    for (uint32 i = 0; i < module->num_exports; i++, lxexp++) {
        if (lxexp->ordinal == ordinal)
            return lxexp->addr;
    } // for

    #if 1
    char entry[128];
    snprintf(entry, sizeof (entry), "ordinal #%u", (uint) ordinal);
    return generateMissingTrampoline(module->name, entry);
    #else
    return NULL;
    #endif
} // getModuleProcAddrByOrdinal

static void *getModuleProcAddrByName(const LxModule *module, const char *name)
{
    //printf("lookup module == '%s', name == '%s'\n", module->name, name);

    const LxExport *lxexp = module->exports;
    for (uint32 i = 0; i < module->num_exports; i++, lxexp++) {
        if (strcmp(lxexp->name, name) == 0)
            return lxexp->addr;
    } // for

    #if 1
    return generateMissingTrampoline(module->name, name);
    #else
    return NULL;
    #endif
} // getModuleProcAddrByName

static void doFixup(uint8 *page, const sint16 offset, const uint32 finalval, const uint16 finalval2, const uint32 finalsize)
{
    #if 0
    if (finalsize == 6) {
        printf("fixing up %p to 0x%X:0x%X (6 bytes)...\n", page + offset, (uint) finalval2, (uint) finalval);
    } else {
        printf("fixing up %p to 0x%X (%u bytes)...\n", page + offset, (uint) finalval, (uint) finalsize);
    } // else
    fflush(stdout);
    #endif

    switch (finalsize) {
        case 1: { uint8 *dst = (uint8 *) (page + offset); *dst = (uint8) finalval; } break;
        case 2: { uint16 *dst = (uint16 *) (page + offset); *dst = (uint16) finalval; } break;
        case 4: { uint32 *dst = (uint32 *) (page + offset); *dst = (uint32) finalval; } break;
        case 6: {
            uint16 *dst1 = (uint16 *) (page + offset);
            *dst1 = (uint16) finalval2;
            uint32 *dst2 = (uint32 *) (page + offset + 2);
            *dst2 = (uint32) finalval;
            break;
        } // case
        default:
            fprintf(stderr, "BUG! Unexpected fixup final size of %u\n", (uint) finalsize);
            exit(1);
    } // switch
} // doFixup

static void fixupPage(const uint8 *exe, LxModule *lxmod, const LxObjectTableEntry *obj, const uint32 pagenum, uint8 *page)
{
    const LxHeader *lx = &lxmod->lx;
//const LxObjectTableEntry *origobj = ((const LxObjectTableEntry *) (exe + lx->object_table_offset));
    const uint32 *fixuppage = (((const uint32 *) (exe + lx->fixup_page_table_offset)) + ((obj->page_table_index - 1) + pagenum));
    const uint32 fixupoffset = *fixuppage;
    const uint32 fixuplen = fixuppage[1] - fixuppage[0];
    const uint8 *fixup = (exe + lx->fixup_record_table_offset) + fixupoffset;
    const uint8 *fixupend = fixup + fixuplen;
//    int record = 0;
    while (fixup < fixupend) {
//record++; printf("FIXUP obj #%u page #%u record #: %d\n", (uint) (obj - origobj), (uint) pagenum, record);
        const uint8 srctype = *(fixup++);
        const uint8 fixupflags = *(fixup++);
        uint8 srclist_count = 0;
        sint16 srcoffset = 0;

        uint32 finalval = 0;
        uint16 finalval2 = 0;
        uint32 finalsize = 0;

        switch (srctype & 0xF) {
            case 0x0:  // byte fixup
                finalsize = 1;
                break;
            case 0x2:  // 16-bit selector fixup
            case 0x5:  // 16-bit offset fixup
                finalsize = 2;
                break;
            case 0x3:  // 16:16 pointer fixup
            case 0x7:  // 32-bit offset fixup
            case 0x8:  // 32-bit self-relative offset fixup
                finalsize = 4;
                break;
            case 0x6:  // 16:32 pointer fixup
                finalsize = 6;
                break;
        } // switch

        if (srctype & 0x20) { // contains a source list
            srclist_count = *(fixup++);
        } else {
            srcoffset = *((sint16 *) fixup);
            fixup += 2;
        } // else

        switch (fixupflags & 0x3) {
            case 0x0: { // Internal fixup record
                uint16 objectid = 0;
                if (fixupflags & 0x40) { // 16 bit value
                    objectid = *((uint16 *) fixup); fixup += 2;
                } else {
                    objectid = (uint16) *(fixup++);
                } // else

                uint32 targetoffset = 0;
                // !!! FIXME: where do we use 16-bit selectors? What does this mean in a 32-bit app?
                if ((srctype & 0xF) != 0x2) { // not a 16-bit selector fixup?
                    if (fixupflags & 0x10) {  // 32-bit target offset
                        targetoffset = *((uint32 *) fixup); fixup += 4;
                    } else {  // 16-bit target offset
                        targetoffset = (uint32) (*((uint16 *) fixup)); fixup += 2;
                    } // else
                } // if

                const uint32 base = (uint32) (size_t) lxmod->mmaps[objectid - 1].addr;
                finalval = base + targetoffset;
                break;
            } // case

            case 0x1: { // Import by ordinal fixup record
                uint16 moduleid = 0;  // module ordinal
                if (fixupflags & 0x40) { // 16 bit value
                    moduleid = *((uint16 *) fixup); fixup += 2;
                } else {
                    moduleid = (uint16) *(fixup++);
                } // else

                uint32 importid = 0;  // import ordinal
                if (fixupflags & 0x80) { // 8 bit value
                    importid = (uint32) *(fixup++);
                } else if (fixupflags & 0x10) {  // 32-bit value
                    importid = *((uint32 *) fixup); fixup += 4;
                } else {  // 16-bit value
                    importid = (uint32) *((uint16 *) fixup); fixup += 2;
                } // else

                if (moduleid == 0) {
                    fprintf(stderr, "uhoh, looking for module ordinal 0, which is illegal.\n");
                } else if (moduleid > lx->num_import_mod_entries) {
                    fprintf(stderr, "uhoh, looking for module ordinal %u, but only %u available.\n", (uint) moduleid, (uint) lx->num_import_mod_entries);
                } else {
                    finalval = (uint32) (size_t) getModuleProcAddrByOrdinal(lxmod->dependencies[moduleid-1], importid);
                } // else
                break;
            } // case

            case 0x2: { // Import by name fixup record
                uint16 moduleid = 0;  // module ordinal
                if (fixupflags & 0x40) { // 16 bit value
                    moduleid = *((uint16 *) fixup); fixup += 2;
                } else {
                    moduleid = (uint16) *(fixup++);
                } // else

                uint32 name_offset = 0;
                if (fixupflags & 0x10) {  // 32-bit value
                    name_offset = *((uint32 *) fixup); fixup += 4;
                } else {  // 16-bit value
                    name_offset = *((uint16 *) fixup); fixup += 2;
                } // else

                if (moduleid == 0) {
                    fprintf(stderr, "uhoh, looking for module ordinal 0, which is illegal.\n");
                } else if (moduleid > lx->num_import_mod_entries) {
                    fprintf(stderr, "uhoh, looking for module ordinal %u, but only %u available.\n", (uint) moduleid, (uint) lx->num_import_mod_entries);
                } else {
                    const uint8 *import_name = (exe + lx->import_proc_table_offset) + name_offset;
                    char name[128];
                    const uint8 namelen = *(import_name++) & 0x7F;  // the top bit is reserved.
                    memcpy(name, import_name, namelen);
                    name[namelen] = '\0';
                    finalval = (uint32) (size_t) getModuleProcAddrByName(lxmod->dependencies[moduleid-1], name);
                } // else
                break;
            } // case

            case 0x3: { // Internal entry table fixup record
                fprintf(stderr, "FIXUP 0x3 WRITE ME\n");
                exit(1);
                break;
            } // case
        } // switch

        if (fixupflags & 0x4) {  // Has additive.
            uint32 additive = 0;
            if (fixupflags & 0x20) { // 32-bit value
                additive = *((uint32 *) fixup); fixup += 4;
            } else {  // 16-bit value
                additive = (uint32) *((uint16 *) fixup);
                fixup += 2;
            } // else
            finalval += additive;
        } // if

        if (srctype & 0x20) {  // source list
            for (uint8 i = 0; i < srclist_count; i++) {
                const sint16 offset = *((sint16 *) fixup); fixup += 2;
                if ((srctype & 0xF) == 0x08) {  // self-relative fixup?
                    assert(finalval2 == 0);
                    doFixup(page, offset, finalval - (((uint32)page)+offset+4), 0, finalsize);
                } else {
                    doFixup(page, offset, finalval, finalval2, finalsize);
                }
            } // for
        } else {
            if ((srctype & 0xF) == 0x08) {  // self-relative fixup?
                assert(finalval2 == 0);
                doFixup(page, srcoffset, finalval - (((uint32)page)+srcoffset+4), 0, finalsize);
            } else {
                doFixup(page, srcoffset, finalval, finalval2, finalsize);
            }
        } // else
    } // while
} // fixupPage

static int loadLxNameTable(LxModule *lxmod, const uint8 *name_table)
{
    for (uint32 i = 0; *name_table; i++) {
        const uint8 namelen = *(name_table++);
        const uint8 *nameptr = name_table;
        name_table += namelen;
        const uint16 ordinal = *((const uint16 *) name_table); name_table += 2;

        if (ordinal == 0)
            continue;  // skip this one.

        LxExport *export = (LxExport *) lxmod->exports;
        const uint32 num_exports = lxmod->num_exports;
        for (uint32 i = 0; i < num_exports; i++, export++) {
            if (export->ordinal == ordinal) {
                char *name = (char *) malloc(namelen + 1);
                if (!name) {
                    fprintf(stderr, "Out of memory!\n");
                    return 0;
                } // if
                memcpy(name, nameptr, namelen);
                name[namelen] = '\0';
                export->name = name;
                break;
            } // if
        } // for
    } // for

    return 1;
} // loadLxNameTable

// !!! FIXME: break up this function.
static LxModule *loadLxModule(const char *fname, uint8 *exe, uint32 exelen, int dependency_tree_depth)
{
    LxModule *retval = NULL;
    const uint8 *origexe = exe;
    //const uint32 origexelen = exelen;

    if (!sanityCheckLxModule(&exe, &exelen))
        goto loadlx_failed;

    const LxHeader *lx = (const LxHeader *) exe;
    const uint32 module_type = lx->module_flags & 0x00038000;

    if ((module_type != 0x0000) && (module_type != 0x8000)) {
        fprintf(stderr, "This is not a standard .exe or .dll (maybe device driver?)\n");
        goto loadlx_failed;
    } // if

    const int isDLL = (module_type == 0x8000);

    if (isDLL && !GLoaderState->main_module) {
        fprintf(stderr, "uhoh, need to load an .exe before a .dll!\n");
        goto loadlx_failed;
    } else if (!isDLL && GLoaderState->main_module) {
        fprintf(stderr, "uhoh, loading an .exe after already loading one!\n");
        goto loadlx_failed;
    } // if else if

    retval = (LxModule *) malloc(sizeof (LxModule));
    if (!retval) {
        fprintf(stderr, "Out of memory!\n");
        goto loadlx_failed;
    } // if
    memset(retval, '\0', sizeof (*retval));
    retval->refcount = 1;
    retval->dependencies = (LxModule **) malloc(sizeof (LxModule *) * lx->num_import_mod_entries);
    retval->mmaps = (LxMmaps *) malloc(sizeof (LxMmaps) * lx->module_num_objects);
    if (!retval->dependencies || !retval->mmaps) {
        fprintf(stderr, "Out of memory!\n");
        goto loadlx_failed;
    } // if
    memset(retval->dependencies, '\0', sizeof (LxModule *) * lx->num_import_mod_entries);
    memset(retval->mmaps, '\0', sizeof (LxMmaps) * lx->module_num_objects);
    memcpy(&retval->lx, lx, sizeof (*lx));

    if (lx->resident_name_table_offset) {
        const uint8 *name_table = exe + lx->resident_name_table_offset;
        const uint8 namelen = *(name_table++);
        char *ptr = retval->name;
        for (uint32 i = 0; i < namelen; i++) {
            const char ch = *(name_table++);
            *(ptr++) = ((ch >= 'a') && (ch <= 'z')) ? (ch + ('A' - 'a')) : ch;
        } // for
        *ptr = '\0';
    } // if

    if (!isDLL) {
        GLoaderState->main_module = retval;
        GLoaderState->pib.pib_hmte = retval;
    } // else if

    const char *modname = retval->name;
    //printf("ref'd new module '%s' to %u\n", modname, 1);

    // !!! FIXME: apparently OS/2 does 1024, but they're not loading the module into RAM each time.
    // !!! FIXME: the spec mentions the 1024 thing for "forwarder" records in the entry table,
    // !!! FIXME:  specifically. _Can_ two DLLs depend on each other? We'll have to load both and
    // !!! FIXME:  then fix them up without recursing.
    if (++dependency_tree_depth > 32) {
        fprintf(stderr, "Likely circular dependency in module '%s'\n", modname);
            goto loadlx_failed;
    } // if

    const LxObjectTableEntry *obj = ((const LxObjectTableEntry *) (exe + lx->object_table_offset));
    for (uint32 i = 0; i < lx->module_num_objects; i++, obj++) {
        if (obj->object_flags & 0x8)  // !!! FIXME: resource object; ignore this until resource support is written, later.
            continue;

        uint32 vsize = obj->virtual_size;
        if ((vsize % lx->page_size) != 0)
             vsize += lx->page_size - (vsize % lx->page_size);

        const int mmapflags = MAP_POPULATE | MAP_ANON | MAP_PRIVATE | (isDLL ? 0 : MAP_FIXED);
        void *base = isDLL ? NULL : (void *) ((size_t) obj->reloc_base_addr);
        void *mmapaddr = mmap(base, vsize, PROT_READ|PROT_WRITE, mmapflags, -1, 0);
        // we'll mprotect() these pages to the proper permissions later.

        //fprintf(stderr, "mmap(%p, %u, RW-, ANON|PRIVATE%s, -1, 0) == %p\n", base, (uint) vsize, isDLL ? "" : "|FIXED", mmapaddr);

        if (mmapaddr == ((void *) MAP_FAILED)) {
            fprintf(stderr, "mmap(%p, %u, RW-, ANON|PRIVATE%s, -1, 0) failed (%d): %s\n",
                    base, (uint) vsize, isDLL ? "" : "|FIXED", errno, strerror(errno));
            goto loadlx_failed;
        } // if

        retval->mmaps[i].addr = mmapaddr;
        retval->mmaps[i].size = vsize;

        const LxObjectPageTableEntry *objpage = ((const LxObjectPageTableEntry *) (exe + lx->object_page_table_offset));
        objpage += obj->page_table_index - 1;

        uint8 *dst = (uint8 *) mmapaddr;
        const uint32 numPageTableEntries = obj->num_page_table_entries;
        for (uint32 pagenum = 0; pagenum < numPageTableEntries; pagenum++, objpage++) {
            const uint8 *src;
            switch (objpage->flags) {
                case 0x00:  // preload
                    src = origexe + lx->data_pages_offset + (objpage->page_data_offset << lx->page_offset_shift);
                    memcpy(dst, src, objpage->data_size);
                    if (objpage->data_size < lx->page_size) {
                        memset(dst + objpage->data_size, '\0', lx->page_size - objpage->data_size);
                    }
                    break;

                case 0x01:  // iterated data.
                    // LX format docs say object_iter_pages_offset must be zero or equal to data_pages_offset for OS/2 2.0. So just use data_pages_offset here.
                    //src = origexe + lx->object_iter_pages_offset + (objpage->page_data_offset << lx->page_offset_shift);
                    src = origexe + lx->data_pages_offset + (objpage->page_data_offset << lx->page_offset_shift);
                    if (!decompressIterated(dst, lx->page_size, src, objpage->data_size)) {
                        fprintf(stderr, "Failed to decompress iterated object page (corrupt file or bug).\n");
                        goto loadlx_failed;
                    } // if
                    break;

                case 0x02: // INVALID, just zero it out.
                case 0x03: // ZEROFILL, just zero it out.
                    memset(dst, '\0', lx->page_size);
                    break;

                case 0x05:  // exepack2
                    src = origexe + lx->data_pages_offset + (objpage->page_data_offset << lx->page_offset_shift);
                    if (!decompressExePack2(dst, lx->page_size, src, objpage->data_size)) {
                        fprintf(stderr, "Failed to decompress object page (corrupt file or bug).\n");
                        goto loadlx_failed;
                    } // if
                    break;

                case 0x08: // !!! FIXME: this is listed in lxlite, presumably this is exepack3 or something. Maybe this was new to Warp4, like exepack2 was new to Warp3. Pull this algorithm in from lxlite later.
                default:
                    fprintf(stderr, "Don't know how to load an object page of type %u!\n", (uint) objpage->flags);
                    goto loadlx_failed;
            } // switch

            dst += lx->page_size;
        } // for

        // any bytes at the end of this object that we didn't initialize? Zero them out.
        const uint32 remain = vsize - ((uint32) (dst - ((uint8 *) mmapaddr)));
        if (remain) {
            memset(dst, '\0', remain);
        } // if
    } // for

    // All the pages we need from the EXE are loaded into the appropriate spots in memory.
    //printf("mmap()'d everything we need!\n");

    retval->eip = lx->eip;
    if (lx->eip_object != 0) {
        const uint32 base = (uint32) ((size_t)retval->mmaps[lx->eip_object - 1].addr);
        retval->eip += base;
    } // if

    // !!! FIXME: esp==0 means something special for programs (and is ignored for library init).
    // !!! FIXME: "A zero value in this field indicates that the stack pointer is to be initialized to the highest address/offset in the object"
    if (!isDLL) {
        retval->esp = lx->esp;
        if (lx->esp_object != 0) {
            const uint32 base = (uint32) ((size_t)retval->mmaps[lx->esp_object - 1].addr);
            retval->esp += base;
        } // if
    } // if

    if (!isDLL) {
        // This needs to be set up now, so it's available to any library
        //  init code that runs in LX land.
        initOs2Tib(GMainTibSpace, (void *) ((size_t) retval->esp), retval->mmaps[retval->lx.esp_object - 1].size, 0);
    } // if

    // Set up our exports...
    uint32 total_ordinals = 0;
    const uint8 *entryptr = exe + lx->entry_table_offset;
    while (*entryptr) {  /* end field has a value of zero. */
        const uint8 numentries = *(entryptr++);  /* number of entries in this bundle */
        const uint8 bundletype = *(entryptr++) & ~0x80;
        if (bundletype != 0x00) {
            total_ordinals += numentries;
            entryptr += 2 + ((bundletype == 0x01) ? 3 : 5) * numentries;
        } // if
    } // while

    LxExport *lxexp = (LxExport *) malloc(sizeof (LxExport) * total_ordinals);
    if (!lxexp) {
        fprintf(stderr, "Out of memory!\n");
        goto loadlx_failed;
    } // if
    memset(lxexp, '\0', sizeof (LxExport) * total_ordinals);
    retval->exports = lxexp;

    uint32 ordinal = 1;
    entryptr = exe + lx->entry_table_offset;
    while (*entryptr) {  /* end field has a value of zero. */
        const uint8 numentries = *(entryptr++);  /* number of entries in this bundle */
        const uint8 bundletype = *(entryptr++) & ~0x80;
        uint16 objidx = 0;

        switch (bundletype) {
            case 0x00: // UNUSED
                ordinal += numentries;
                break;

            case 0x01: // 16BIT
                objidx = *((const uint16 *) entryptr) - 1;
                entryptr += 2;
                for (uint8 i = 0; i < numentries; i++) {
                    entryptr++;
                    lxexp->ordinal = ordinal++;
                    lxexp->addr = ((uint8 *) retval->mmaps[objidx].addr) + *((const uint16 *) entryptr);
                    lxexp++;
                    entryptr += 2;
                } // for
                break;

            case 0x03: // 32BIT
                objidx = *((const uint16 *) entryptr) - 1;
                entryptr += 2;
                for (uint8 i = 0; i < numentries; i++) {
                    entryptr++;
                    lxexp->ordinal = ordinal++;
                    lxexp->addr = ((uint8 *) retval->mmaps[objidx].addr) + *((const uint32 *) entryptr);
                    lxexp++;
                    entryptr += 4;
                }
                break;

            case 0x02: // 286CALLGATE
            case 0x04: // FORWARDER
                fprintf(stderr, "WRITE ME %s:%d\n", __FILE__, __LINE__);
                goto loadlx_failed;

            default:
                fprintf(stderr, "UNKNOWN ENTRY TYPE (%u)\n\n", (uint) bundletype);
                goto loadlx_failed;
        } // switch
    } // while

    retval->num_exports = (uint32) (lxexp - retval->exports);

    // Now load named entry points.
    if (lx->resident_name_table_offset) {
        if (!loadLxNameTable(retval, exe + lx->resident_name_table_offset))
            goto loadlx_failed;
    } // if

    if (lx->non_resident_name_table_offset && lx->non_resident_name_table_len) {
        if (!loadLxNameTable(retval, exe + lx->non_resident_name_table_offset))
            goto loadlx_failed;
    } // if

    // Load other dependencies of this module.
    const uint8 *import_modules_table = exe + lx->import_module_table_offset;
    for (uint32 i = 0; i < lx->num_import_mod_entries; i++) {
        const uint8 namelen = *(import_modules_table++);
        if (namelen > 127) {
            fprintf(stderr, "Import module %u name is > 127 chars (%u). Corrupt file or bug!\n", (uint) (i + 1), (uint) namelen);
            goto loadlx_failed;
        }
        char name[128];
        memcpy(name, import_modules_table, namelen);
        import_modules_table += namelen;
        name[namelen] = '\0';
        retval->dependencies[i] = loadLxModuleByModuleNameInternal(name, dependency_tree_depth);
        if (!retval->dependencies[i]) {
            fprintf(stderr, "Failed to load dependency '%s' for module '%s'\n", name, modname);
            goto loadlx_failed;
        } // if
    } // for

    // Run through again and do all the fixups...
    obj = ((const LxObjectTableEntry *) (exe + lx->object_table_offset));
    for (uint32 i = 0; i < lx->module_num_objects; i++, obj++) {
        if (obj->object_flags & 0x8)  // !!! FIXME: resource object; ignore this until resource support is written, later.
            continue;

        uint8 *dst = (uint8 *) retval->mmaps[i].addr;
        const uint32 numPageTableEntries = obj->num_page_table_entries;
        for (uint32 pagenum = 0; pagenum < numPageTableEntries; pagenum++) {
            fixupPage(exe, retval, obj, pagenum, dst);
            dst += lx->page_size;
        } // for

        // !!! FIXME: hack to nop out some 16-bit code in emx.dll startup...
        if ((i == 1) && (strcasecmp(modname, "EMX") == 0)) {
            // This is the 16-bit signal handler installer. nop it out.
            uint8 *ptr = ((uint8 *) retval->mmaps[1].addr) + 28596;
            for (uint32 j = 0; j < 37; j++)
                *(ptr++) = 0x90; // nop
        } // if

        // Now set all the pages of this object to the proper final permissions...
        const int prot = ((obj->object_flags & 0x1) ? PROT_READ : 0) |
                         ((obj->object_flags & 0x2) ? PROT_WRITE : 0) |
                         ((obj->object_flags & 0x4) ? PROT_EXEC : 0);

        if (mprotect(retval->mmaps[i].addr, retval->mmaps[i].size, prot) == -1) {
            fprintf(stderr, "mprotect(%p, %u, %s%s%s, ANON|PRIVATE|FIXED, -1, 0) failed (%d): %s\n",
                    retval->mmaps[i].addr, (uint) retval->mmaps[i].size,
                    (prot&PROT_READ) ? "R" : "-",
                    (prot&PROT_WRITE) ? "W" : "-",
                    (prot&PROT_EXEC) ? "X" : "-",
                    errno, strerror(errno));
            goto loadlx_failed;
        } // if
    } // for

    retval->os2path = makeOS2Path(fname);
    if (!retval->os2path)
        goto loadlx_failed;

    if (!isDLL) {
        retval->initialized = 1;
    } else {
        // call library init code...
        assert(GLoaderState->main_module != NULL);
        assert(GLoaderState->main_module != retval);
        runLxLibraryInit(retval);

        retval->initialized = 1;

        // module is ready to use, put it in the loaded list.
        // !!! FIXME: mutex this
        if (GLoaderState->loaded_modules) {
            retval->next = GLoaderState->loaded_modules;
            GLoaderState->loaded_modules->prev = retval;
        } // if
        GLoaderState->loaded_modules = retval;
    } // if

    return retval;

loadlx_failed:
    freeLxModule(retval);
    return NULL;
} // loadLxModule

static LxModule *loadLxModuleByPathInternal(const char *fname, const int dependency_tree_depth)
{
    const char *what = NULL; (void) what;
    uint8 *module = NULL;
    uint32 modulelen = 0;
    FILE *io = NULL;

    // !!! FIXME: locate correct file (case-insensitive checking, convert '\\' to '/' etc)...

    #define LOADFAIL(x) { what = x; goto loadmod_failed; }

    if ((io = fopen(fname, "rb")) == NULL) LOADFAIL("open");
    if (fseek(io, 0, SEEK_END) < 0) LOADFAIL("seek");
    modulelen = ftell(io);
    if ((module = (uint8 *) malloc(modulelen)) == NULL) LOADFAIL("malloc");
    rewind(io);
    if (fread(module, modulelen, 1, io) != 1) LOADFAIL("read");
    fclose(io);

    #undef LOADFAIL

    LxModule *retval = loadLxModule(fname, module, modulelen, dependency_tree_depth);
    free(module);
    return retval;

loadmod_failed:
    fprintf(stderr, "%s failure on '%s: %s'\n", what, fname, strerror(errno));
    if (io)
        fclose(io);
    free(module);
    return NULL;
} // loadLxModuleByPathInternal

static inline LxModule *loadLxModuleByPath(const char *fname)
{
    return loadLxModuleByPathInternal(fname, 0);
} // loadLxModuleByPath

static LxModule *loadNativeModule(const char *fname, const char *modname)
{
    LxModule *retval = (LxModule *) malloc(sizeof (LxModule));
    void *lib = NULL;
    LxNativeModuleInitEntryPoint fn = NULL;
    const LxExport *exports = NULL;
    uint32 num_exports = 0;
    char *os2path = makeOS2Path(fname);

    if (!retval || !modname || !os2path)
        goto loadnative_failed;
        
    memset(retval, '\0', sizeof(*retval));

    // !!! FIXME: mutex this.
    lib = dlopen(fname, RTLD_LOCAL | RTLD_NOW);
    if (lib == NULL) {
        fprintf(stderr, "dlopen('%s') failed: %s\n", fname, dlerror());
        goto loadnative_failed;
    } // if

    fn = (LxNativeModuleInitEntryPoint) dlsym(lib, "lxNativeModuleInit");
    if (!fn)
        goto loadnative_failed;

    exports = fn(GLoaderState, &num_exports);
    if (!exports)
        goto loadnative_failed;
    retval->refcount = 1;
    strcpy(retval->name, modname);
    retval->nativelib = lib;
    retval->os2path = os2path;
    retval->exports = exports;
    retval->num_exports = num_exports;
    retval->initialized = 1;

    //fprintf(stderr, "Loaded native module '%s' (%u exports).\n", fname, (uint) num_exports);

    return retval;

loadnative_failed:
    if (lib) dlclose(lib);
    free(os2path);
    free(retval);
    return NULL;
} // loadNativeModule

static LxModule *loadLxModuleByModuleNameInternal(const char *modname, const int dependency_tree_depth)
{
    // !!! FIXME: mutex this
    for (LxModule *i = GLoaderState->loaded_modules; i != NULL; i = i->next) {
        if (strcasecmp(i->name, modname) == 0) {
            i->refcount++;
            //printf("ref'd module '%s' to %u\n", i->name, (uint) i->refcount);
            return i;
        } // if
    } // for

    // !!! FIXME: decide the right path to the file, or if it's a native replacement library.
    char fname[256];
    snprintf(fname, sizeof (fname), "%s.dll", modname);
    locatePathCaseInsensitive(fname);

    LxModule *retval = NULL;
    if (access(fname, F_OK) == 0)
        retval = loadLxModuleByPathInternal(fname, dependency_tree_depth);

    if (!retval) {
        snprintf(fname, sizeof (fname), "./lib%s.so", modname);
        for (char *ptr = fname; *ptr; ptr++) {
            *ptr = (((*ptr >= 'A') && (*ptr <= 'Z')) ? (*ptr - ('A' - 'a')) : *ptr);
        } // for
        retval = loadNativeModule(fname, modname);

        if (retval != NULL) {
            // module is ready to use, put it in the loaded list.
            // !!! FIXME: mutex this
            if (GLoaderState->loaded_modules) {
                retval->next = GLoaderState->loaded_modules;
                GLoaderState->loaded_modules->prev = retval;
            } // if
            GLoaderState->loaded_modules = retval;
        } // if
    } // if
    return retval;
} // loadLxModuleByModuleNameInternal

static void initPib(LxPIB *pib, const int argc, char **argv, char **envp)
{
    // !!! FIXME: this is incomplete.
    memset(pib, '\0', sizeof (*pib));

    // Eventually, the environment table looks like this (double-null to terminate list):  var1=a\0var2=b\0var3=c\0\0
    // The command line looks like this: \0argv0\0argv1 argv2 argvN\0\0
    // Between env and cmd is the exe name: argv0\0

    size_t len = 1;
    for (int i = 0; i < argc; i++) {
        int needs_escape = 0;
        int num_backslashes = 0;
        for (const char *arg = argv[i]; *arg; arg++) {
            const char ch = *arg;
            if ((ch == ' ') || (ch == '\t'))
                needs_escape = 1;
            else if ((ch == '\\') || (ch == '\"'))
                num_backslashes++;
            len++;
        } // for

        if (needs_escape) {
            len += 2 + num_backslashes;
        } // if

        len++;  // terminator
    } // for

    len += strlen(argv[0]) + 1;  // for the exe name.

    const char *default_os2path = "PATH=C:\\home\\icculus\\Dropbox\\emx\\bin;C:\\WATCOM\\binp;C:\\home\\icculus";  // !!! FIXME: noooooope.
    for (int i = 0; envp[i]; i++) {
        const char *str = envp[i];
        if (strncmp(str, "PATH=", 5) == 0) {
            if (!GLoaderState->subprocess)
                str = default_os2path;
        } else if (strncmp(str, "IS_2INE=", 8) == 0) {
            continue;
        } // if
        len += strlen(str) + 1;
    } // for

    len += 4;  // null terminators.

    char *env = (char *) malloc(len);
    if (!env) {
        fprintf(stderr, "Out of memory\n");
        exit(1);
    } // if

    char *ptr = env;
    for (int i = 0; envp[i]; i++) {
        const char *str = envp[i];
        if (strncmp(str, "PATH=", 5) == 0) {
            if (!GLoaderState->subprocess)
                str = default_os2path;
        } else if (strncmp(str, "IS_2INE=", 8) == 0) {
            continue;
        } // if

        strcpy(ptr, str);
        ptr += strlen(str) + 1;
    }
    *(ptr++) = '\0';

    // put the exe name between the environment and the command line.
    strcpy(ptr, argv[0]);
    ptr += strlen(argv[0]) + 1;

    char *cmd = ptr;
    strcpy(ptr, argv[0]);
    ptr += strlen(argv[0]);
    *(ptr++) = '\0';
    for (int i = 1; i < argc; i++) {
        int needs_escape = 0;
        for (const char *arg = argv[i]; *arg; arg++) {
            const char ch = *arg;
            if ((ch == ' ') || (ch == '\t'))
                needs_escape = 1;
        } // for

        if (needs_escape) {
            *(ptr++) = '"';
            for (const char *arg = argv[i]; *arg; arg++) {
                const char ch = *arg;
                if ((ch == '\\') || (ch == '\n'))
                    *(ptr++) = '\\';
                *(ptr++) = ch;
            } // for
            *(ptr++) = '"';
        } else {
            for (const char *arg = argv[i]; *arg; arg++)
                *(ptr++) = *arg;
        } // if

        if (i < (argc-1))
            *(ptr++) = ' ';
    } // for

    *(ptr++) = '\0';

    pib->pib_ulpid = (uint32) getpid();
    pib->pib_ulppid = (uint32) getppid();
    pib->pib_pchcmd = cmd;
    pib->pib_pchenv = env;
    //pib->pib_hmte is filled in later during loadLxModule()
    // !!! FIXME: uint32 pib_flstatus;
    // !!! FIXME: uint32 pib_ultype;
} // initPib


static LxModule *loadLxModuleByModuleName(const char *modname)
{
    return loadLxModuleByModuleNameInternal(modname, 0);
} // loadLxModuleByModuleName

static __attribute__((noreturn)) void handleThreadLocalStorageAccess(const int slot, ucontext_t *uctx)
{
    greg_t *gregs = uctx->uc_mcontext.gregs;

    // use the segfaulting thread's FS register, so we can get its TIB2 pointer.
    LxTIB2 *ptib2 = NULL;
    __asm__ __volatile__ (
        "pushw %%fs            \n\t"
        "movw %%ax, %%fs       \n\t"
        "movl %%fs:0xC, %%eax  \n\t"
        "popw %%fs             \n\t"
            : "=a" (ptib2)
            : "eax" (gregs[REG_FS])
    );
    uint32 *tls = (uint32 *) (ptib2 + 1);  // The thread's TLS data is stored right after its TIB2 struct.
    tls += slot;

    printf("We wanted to access thread %p TLS slot %d (currently holds %u)\n", tls - slot, slot, (uint) *tls);

    static const int x86RegisterToUContextEnum[] = {
        REG_EAX, REG_ECX, REG_EDX, REG_EBX, REG_ESP, REG_EBP, REG_ESI, REG_EDI
    };

    // this is a hack; we'll want a much more serious x86 instruction decoder before long.
    int handled = 1;
    uint8 *eip = (void *) (size_t) gregs[REG_EIP];  // program counter at point of segfault.
    switch (eip[0]) {
        case 0xC7:  // mov imm16/32 -> r/m
            printf("setting TLS slot %d to imm %u.\n", slot, (uint) *((uint32 *) (eip + 2)));
            *tls = *((uint32 *) (eip + 2));  // !!! FIXME: verify it's a imm32, not 16
            gregs[REG_EIP] += 6;
            break;

        case 0x89:  // mov r -> r/m
            printf("setting TLS slot %d to reg %d (%u).\n", slot, x86RegisterToUContextEnum[eip[1] >> 3], (uint) gregs[x86RegisterToUContextEnum[eip[1] >> 3]]);
            *tls = (uint32) gregs[x86RegisterToUContextEnum[eip[1] >> 3]];
            gregs[REG_EIP] += 2;
            break;

        case 0x8B:  // mov r/m -> r
            printf("setting to reg %d to TLS slot %d (%u).\n", (uint) x86RegisterToUContextEnum[eip[1] >> 3], slot, *tls);
            gregs[x86RegisterToUContextEnum[eip[1] >> 3]] = (greg_t) *tls;
            gregs[REG_EIP] += 2;
            break;

        default:
            handled = 0;
            break;
    } // switch

    if (!handled) {
        fprintf(stderr, "Oh no, unhandled opcode 0x%X at %p accessing TLS register! File a bug!\n", (uint) eip[0], eip);
    } else {
        // drop out of signal handler to (hopefully) next instruction in the app,
        //  as if it accessed the TLS slot normally and none of this ever happened.
        printf("TLS access handler jumping back into app at %p...\n", (void *) gregs[REG_EIP]); fflush(stdout);
        setcontext(uctx);
        fprintf(stderr, "panic: setcontext() failed in the TLS access handler! Aborting! (%s)\n", strerror(errno));
    } // else

    fflush(stderr);
    abort();
} // handleThreadLocalStorageAccess

static void segfault_catcher(int sig, siginfo_t *info, void *ctx)
{
    const uint32 *addr = (const uint32 *) info->si_addr;
    const uint32 *tlspage = GLoaderState->tlspage;

    if (tlspage && (addr >= tlspage))
    {
        // was the app accessing one of the OS/2 TLS slots?
        const int slot = (int) (addr - tlspage);
        if (slot < 32)
            handleThreadLocalStorageAccess(slot, (ucontext_t *) ctx);
    } // if

    static int faults = 0;
    faults++;
    switch (faults) {
        // !!! FIXME: case #1 should be a much more detailed crash dump.
        case 1: fprintf(stderr, "SIGSEGV at addr=%p (eip=%p)\n", addr, (void *) ((ucontext_t *) ctx)->uc_mcontext.gregs[REG_EIP]); break;
        case 2: write(2, "SIGSEGV, aborting.\n", 19); break;
    } // switch

    abort();  // cash out.
} // segfault_catcher

static int installSignalHandlers(void)
{
    struct sigaction action;

    memset(&action, '\0', sizeof (action));
    action.sa_sigaction = segfault_catcher;
    action.sa_flags = SA_NODEFER | SA_SIGINFO;

    if (sigaction(SIGSEGV, &action, NULL) == -1) {
        fprintf(stderr, "Couldn't install signal handler! (%s)\n", strerror(errno));
        return 0;
    } // if

    return 1;
} // installSignalHandlers

int main(int argc, char **argv, char **envp)
{
    if (argc < 2) {
        fprintf(stderr, "USAGE: %s <program.exe> [...programargs...]\n", argv[0]);
        return 1;
    }

    if (!installSignalHandlers())
        return 1;

    const char *envr = getenv("IS_2INE");
    GLoaderState->subprocess = (envr != NULL);
    GLoaderState->initOs2Tib = initOs2Tib;
    GLoaderState->deinitOs2Tib = deinitOs2Tib;
    GLoaderState->loadModule = loadLxModuleByModuleName;
    GLoaderState->locatePathCaseInsensitive = locatePathCaseInsensitive;
    GLoaderState->makeUnixPath = makeUnixPath;
    GLoaderState->makeOS2Path = makeOS2Path;

    const char *modulename = GLoaderState->subprocess ? envr : argv[1];

    // standalone, drop argv[0]. As a subprocess, keep it.
    if (!GLoaderState->subprocess) {
        argc--;
        argv++;
    } // if

    initPib(&GLoaderState->pib, argc, argv, envp);

    LxModule *lxmod = loadLxModuleByPath(modulename);
    if (lxmod != NULL)
        runLxModule(lxmod, argc, argv, envp);

    return 1;
} // main

// end of lx_loader.c ...