outrdf.c

nasm的全套源代码,有些我做了些修改,以方便您更方便更容易调试成功,方便学习做编译器

/* outrdf.c	output routines for the Netwide Assembler to produce
 *		RDOFF format object files (which are intended mainly
 *		for use in proprietary projects, as the code to load and
 *		execute them is very simple). They will also be used
 *		for device drivers and possibly some executable files
 *		in the MOSCOW operating system. See Rdoff.txt for
 *		details.
 *
 * 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.
 */

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

#include "nasm.h"
#include "nasmlib.h"
#include "outform.h"

/* VERBOSE_WARNINGS: define this to add some extra warnings... */
#define VERBOSE_WARNINGS

#ifdef OF_RDF

typedef short int16;            /* not sure if this will be required to be altered
                                   at all... best to typedef it just in case */

static const char *RDOFFId = "RDOFF1";  /* written to start of RDOFF files */

/* the records that can be found in the RDOFF header */

/* Note that whenever a segment is referred to in the RDOFF file, its number
 * is always half of the segment number that NASM uses to refer to it; this
 * is because NASM only allocates even numbered segments, so as to not
 * waste any of the 16 bits of segment number written to the file - this
 * allows up to 65533 external labels to be defined; otherwise it would be
 * 32764. */

struct RelocRec {
    char type;                  /* must be 1 */
    char segment;               /* only 0 for code, or 1 for data supported,
                                 * but add 64 for relative refs (ie do not require
                                 * reloc @ loadtime, only linkage) */
    long offset;                /* from start of segment in which reference is loc'd */
    char length;                /* 1 2 or 4 bytes */
    int16 refseg;               /* segment to which reference refers to */
};

struct ImportRec {
    char type;                  /* must be 2 */
    int16 segment;              /* segment number allocated to the label for reloc
                                 * records - label is assumed to be at offset zero
                                 * in this segment, so linker must fix up with offset
                                 * of segment and of offset within segment */
    char label[33];             /* zero terminated... should be written to file until
                                 * the zero, but not after it - max len = 32 chars */
};

struct ExportRec {
    char type;                  /* must be 3 */
    char segment;               /* segment referred to (0/1) */
    long offset;                /* offset within segment */
    char label[33];             /* zero terminated as above. max len = 32 chars */
};

struct DLLRec {
    char type;                  /* must be 4 */
    char libname[128];          /* name of library to link with at load time */
};

struct BSSRec {
    char type;                  /* must be 5 */
    long amount;                /* number of bytes BSS to reserve */
};

/* code for managing buffers needed to seperate code and data into individual
 * sections until they are ready to be written to the file.
 * We'd better hope that it all fits in memory else we're buggered... */

#define BUF_BLOCK_LEN 4088      /* selected to match page size (4096)
                                 * on 80x86 machines for efficiency */

typedef struct memorybuffer {
    int length;
    char buffer[BUF_BLOCK_LEN];
    struct memorybuffer *next;
} memorybuffer;

static memorybuffer *newmembuf(void)
{
    memorybuffer *t;

    t = nasm_malloc(sizeof(memorybuffer));

    t->length = 0;
    t->next = NULL;
    return t;
}

static void membufwrite(memorybuffer * b, void *data, int bytes)
{
    int16 w;
    long l;

    if (b->next) {              /* memory buffer full - use next buffer */
        membufwrite(b->next, data, bytes);
        return;
    }
    if ((bytes < 0 && b->length - bytes > BUF_BLOCK_LEN)
        || (bytes > 0 && b->length + bytes > BUF_BLOCK_LEN)) {

        /* buffer full and no next allocated... allocate and initialise next
         * buffer */

        b->next = newmembuf();
        membufwrite(b->next, data, bytes);
        return;
    }

    switch (bytes) {
    case -4:                   /* convert to little-endian */
        l = *(long *)data;
        b->buffer[b->length++] = l & 0xFF;
        l >>= 8;
        b->buffer[b->length++] = l & 0xFF;
        l >>= 8;
        b->buffer[b->length++] = l & 0xFF;
        l >>= 8;
        b->buffer[b->length++] = l & 0xFF;
        break;

    case -2:
        w = *(int16 *) data;
        b->buffer[b->length++] = w & 0xFF;
        w >>= 8;
        b->buffer[b->length++] = w & 0xFF;
        break;

    default:
        while (bytes--) {
            b->buffer[b->length++] = *(*(unsigned char **)&data);

            (*(unsigned char **)&data)++;
        }
        break;
    }
}

static void membufdump(memorybuffer * b, FILE * fp)
{
    if (!b)
        return;

    fwrite(b->buffer, 1, b->length, fp);

    membufdump(b->next, fp);
}

static int membuflength(memorybuffer * b)
{
    if (!b)
        return 0;
    return b->length + membuflength(b->next);
}

static void freemembuf(memorybuffer * b)
{
    if (!b)
        return;
    freemembuf(b->next);
    nasm_free(b);
}

/***********************************************************************
 * Actual code to deal with RDOFF ouput format begins here...
 */

/* global variables set during the initialisation phase */

static memorybuffer *seg[2];    /* seg 0 = code, seg 1 = data */
static memorybuffer *header;    /* relocation/import/export records */

static FILE *ofile;

static efunc error;

static int segtext, segdata, segbss;
static long bsslength;

static void rdf_init(FILE * fp, efunc errfunc, ldfunc ldef, evalfunc eval)
{
    ofile = fp;
    error = errfunc;
    seg[0] = newmembuf();
    seg[1] = newmembuf();
    header = newmembuf();
    segtext = seg_alloc();
    segdata = seg_alloc();
    segbss = seg_alloc();
    if (segtext != 0 || segdata != 2 || segbss != 4)
        error(ERR_PANIC,
              "rdf segment numbers not allocated as expected (%d,%d,%d)",
              segtext, segdata, segbss);
    bsslength = 0;
}

static long rdf_section_names(char *name, int pass, int *bits)
{
    /*
     * Default is 32 bits.
     */
    if (!name)
        *bits = 32;

    if (!name)
        return 0;
    if (!strcmp(name, ".text"))
        return 0;
    else if (!strcmp(name, ".data"))
        return 2;
    else if (!strcmp(name, ".bss"))
        return 4;
    else
        return NO_SEG;
}

static void write_reloc_rec(struct RelocRec *r)
{
    if (r->refseg != NO_SEG && (r->refseg & 1))
        error(ERR_NONFATAL, "RDF format does not support segment base"
              " references");

    r->refseg >>= 1;            /* adjust segment nos to RDF rather than NASM */

    membufwrite(header, &r->type, 1);
    membufwrite(header, &r->segment, 1);
    membufwrite(header, &r->offset, -4);
    membufwrite(header, &r->length, 1);
    membufwrite(header, &r->refseg, -2);        /* 9 bytes written */
}

static void write_export_rec(struct ExportRec *r)
{
    r->segment >>= 1;

    membufwrite(header, &r->type, 1);
    membufwrite(header, &r->segment, 1);
    membufwrite(header, &r->offset, -4);
    membufwrite(header, r->label, strlen(r->label) + 1);
}

static void write_import_rec(struct ImportRec *r)
{
    r->segment >>= 1;

    membufwrite(header, &r->type, 1);
    membufwrite(header, &r->segment, -2);
    membufwrite(header, r->label, strlen(r->label) + 1);
}

static void write_bss_rec(struct BSSRec *r)
{
    membufwrite(header, &r->type, 1);
    membufwrite(header, &r->amount, -4);
}

static void write_dll_rec(struct DLLRec *r)
{
    membufwrite(header, &r->type, 1);
    membufwrite(header, r->libname, strlen(r->libname) + 1);
}