rdfload.c   [plain text]


/* rdfload.c	RDOFF Object File loader library
 *
 * The Netwide Assembler is copyright (C) 1996 Simon Tatham and
 * Julian Hall. All rights reserved. The software is
 * redistributable under the licence given in the file "Licence"
 * distributed in the NASM archive.
 *
 * Permission to use this file in your own projects is granted, as long
 * as acknowledgement is given in an appropriate manner to its authors,
 * with instructions of how to obtain a copy via ftp.
 */

/*
 * TODO: this has been modified from previous version only in very
 * simplistic ways. Needs to be improved drastically, especially:
 *   - support for more than the 2 standard segments
 *   - support for segment relocations (hard to do in ANSI C)
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "rdfload.h"
#include "symtab.h"
#include "collectn.h"

extern int rdf_errno;

rdfmodule *rdfload(const char *filename)
{
    rdfmodule *f;
    long bsslength = 0;
    char *hdr;
    rdfheaderrec *r;

    f = malloc(sizeof(rdfmodule));
    if (f == NULL) {
        rdf_errno = RDF_ERR_NOMEM;
        return NULL;
    }

    f->symtab = symtabNew();
    if (!f->symtab) {
        free(f);
        rdf_errno = RDF_ERR_NOMEM;
        return NULL;
    }

    /* open the file */
    if (rdfopen(&(f->f), filename)) {
        free(f);
        return NULL;
    }

    /* read in text and data segments, and header */

    f->t = malloc(f->f.seg[0].length);
    f->d = malloc(f->f.seg[1].length);  /* BSS seg allocated later */
    hdr = malloc(f->f.header_len);

    if (!f->t || !f->d || !hdr) {
        rdf_errno = RDF_ERR_NOMEM;
        rdfclose(&f->f);
        if (f->t)
            free(f->t);
        if (f->d)
            free(f->d);
        free(f);
        return NULL;
    }

    if (rdfloadseg(&f->f, RDOFF_HEADER, hdr) ||
        rdfloadseg(&f->f, RDOFF_CODE, f->t) ||
        rdfloadseg(&f->f, RDOFF_DATA, f->d)) {
        rdfclose(&f->f);
        free(f->t);
        free(f->d);
        free(f);
        free(hdr);
        return NULL;
    }

    rdfclose(&f->f);

    /* Allocate BSS segment; step through header and count BSS records */

    while ((r = rdfgetheaderrec(&f->f))) {
        if (r->type == 5)
            bsslength += r->b.amount;
    }

    f->b = malloc(bsslength);
    if (bsslength && (!f->b)) {
        free(f->t);
        free(f->d);
        free(f);
        free(hdr);
        rdf_errno = RDF_ERR_NOMEM;
        return NULL;
    }

    rdfheaderrewind(&f->f);

    f->textrel = (long)f->t;
    f->datarel = (long)f->d;
    f->bssrel = (long)f->b;

    return f;
}

int rdf_relocate(rdfmodule * m)
{
    rdfheaderrec *r;
    Collection imports;
    symtabEnt e;
    long rel;
    unsigned char *seg;

    rdfheaderrewind(&m->f);
    collection_init(&imports);

    while ((r = rdfgetheaderrec(&m->f))) {
        switch (r->type) {
        case 1:                /* Relocation record */

            /* calculate relocation factor */

            if (r->r.refseg == 0)
                rel = m->textrel;
            else if (r->r.refseg == 1)
                rel = m->datarel;
            else if (r->r.refseg == 2)
                rel = m->bssrel;
            else
                /* We currently do not support load-time linkage.
                   This should be added some time soon... */

                return 1;       /* return error code */

            if ((r->r.segment & 63) == 0)
                seg = m->t;
            else if ((r->r.segment & 63) == 1)
                seg = m->d;
            else
                continue;       /* relocation not in a loaded segment */

            /* it doesn't matter in this case that the code is non-portable,
               as the entire concept of executing a module like this is
               non-portable */
            switch (r->r.length) {
            case 1:
                seg[r->r.offset] += (char)rel;
                break;
            case 2:
                *(uint16 *) (seg + r->r.offset) += (uint16) rel;
                break;
            case 4:
                *(long *)(seg + r->r.offset) += rel;
                break;
            }
            break;

        case 3:                /* export record - add to symtab */
            e.segment = r->e.segment;
            e.offset = r->e.offset + (e.segment == 0 ? m->textrel :     /* 0 -> code */
                                      e.segment == 1 ? m->datarel :     /* 1 -> data */
                                      m->bssrel);       /* 2 -> bss  */
            e.flags = 0;
            e.name = malloc(strlen(r->e.label) + 1);
            if (!e.name)
                return 1;

            strcpy(e.name, r->e.label);
            symtabInsert(m->symtab, &e);
            break;

        case 6:                /* segment relocation */
            fprintf(stderr, "%s: segment relocation not supported by this "
                    "loader\n", m->f.name);
            return 1;
        }
    }
    return 0;
}