outcoff.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

/* outcoff.c	output routines for the Netwide Assembler to produce
 *		COFF object files (for DJGPP and Win32)
 *
 * 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 <time.h>

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

#if defined(OF_COFF) || defined(OF_WIN32)

/*
 * Notes on COFF:
 *
 * (0) When I say `standard COFF' below, I mean `COFF as output and
 * used by DJGPP'. I assume DJGPP gets it right.
 *
 * (1) Win32 appears to interpret the term `relative relocation'
 * differently from standard COFF. Standard COFF understands a
 * relative relocation to mean that during relocation you add the
 * address of the symbol you're referencing, and subtract the base
 * address of the section you're in. Win32 COFF, by contrast, seems
 * to add the address of the symbol and then subtract the address
 * of THE BYTE AFTER THE RELOCATED DWORD. Hence the two formats are
 * subtly incompatible.
 *
 * (2) Win32 doesn't bother putting any flags in the header flags
 * field (at offset 0x12 into the file).
 *
 * (3) Win32 uses some extra flags into the section header table:
 * it defines flags 0x80000000 (writable), 0x40000000 (readable)
 * and 0x20000000 (executable), and uses them in the expected
 * combinations. It also defines 0x00100000 through 0x00700000 for
 * section alignments of 1 through 64 bytes.
 *
 * (4) Both standard COFF and Win32 COFF seem to use the DWORD
 * field directly after the section name in the section header
 * table for something strange: they store what the address of the
 * section start point _would_ be, if you laid all the sections end
 * to end starting at zero. Dunno why. Microsoft's documentation
 * lists this field as "Virtual Size of Section", which doesn't
 * seem to fit at all. In fact, Win32 even includes non-linked
 * sections such as .drectve in this calculation.
 *
 * (5) Standard COFF does something very strange to common
 * variables: the relocation point for a common variable is as far
 * _before_ the variable as its size stretches out _after_ it. So
 * we must fix up common variable references. Win32 seems to be
 * sensible on this one.
 */

/* Flag which version of COFF we are currently outputting. */
static int win32;

struct Reloc {
    struct Reloc *next;
    long address;               /* relative to _start_ of section */
    long symbol;                /* symbol number */
    enum {
        SECT_SYMBOLS,
        ABS_SYMBOL,
        REAL_SYMBOLS
    } symbase;                  /* relocation for symbol number :) */
    int relative;               /* TRUE or FALSE */
};

struct Symbol {
    char name[9];
    long strpos;                /* string table position of name */
    int section;                /* section number where it's defined
                                 * - in COFF codes, not NASM codes */
    int is_global;              /* is it a global symbol or not? */
    long value;                 /* address, or COMMON variable size */
};

static FILE *coffp;
static efunc error;
static char coff_infile[FILENAME_MAX];

struct Section {
    struct SAA *data;
    unsigned long len;
    int nrelocs;
    long index;
    struct Reloc *head, **tail;
    unsigned long flags;        /* section flags */
    char name[9];
    long pos, relpos;
};

#define TEXT_FLAGS (win32 ? 0x60500020L : 0x20L)
#define DATA_FLAGS (win32 ? 0xC0300040L : 0x40L)
#define BSS_FLAGS (win32 ? 0xC0300080L : 0x80L)
#define INFO_FLAGS 0x00100A00L
#define RDATA_FLAGS (win32 ? 0x40400040L : 0x40L)

#define SECT_DELTA 32
static struct Section **sects;
static int nsects, sectlen;

static struct SAA *syms;
static unsigned long nsyms;

static long def_seg;

static int initsym;

static struct RAA *bsym, *symval;

static struct SAA *strs;
static unsigned long strslen;

static void coff_gen_init(FILE *, efunc);
static void coff_sect_write(struct Section *, const unsigned char *,
                            unsigned long);
static void coff_write(void);
static void coff_section_header(char *, long, long, long, long, int, long);
static void coff_write_relocs(struct Section *);
static void coff_write_symbols(void);

static void coff_win32_init(FILE * fp, efunc errfunc,
                            ldfunc ldef, evalfunc eval)
{
    win32 = TRUE;
    (void)ldef;                 /* placate optimisers */
    coff_gen_init(fp, errfunc);
}

static void coff_std_init(FILE * fp, efunc errfunc, ldfunc ldef,
                          evalfunc eval)
{
    win32 = FALSE;
    (void)ldef;                 /* placate optimisers */
    coff_gen_init(fp, errfunc);
}

static void coff_gen_init(FILE * fp, efunc errfunc)
{

    coffp = fp;
    error = errfunc;
    sects = NULL;
    nsects = sectlen = 0;
    syms = saa_init((long)sizeof(struct Symbol));
    nsyms = 0;
    bsym = raa_init();
    symval = raa_init();
    strs = saa_init(1L);
    strslen = 0;
    def_seg = seg_alloc();
}

static void coff_cleanup(int debuginfo)
{
    struct Reloc *r;
    int i;

    (void)debuginfo;

    coff_write();
    fclose(coffp);
    for (i = 0; i < nsects; i++) {
        if (sects[i]->data)
            saa_free(sects[i]->data);
        while (sects[i]->head) {
            r = sects[i]->head;
            sects[i]->head = sects[i]->head->next;
            nasm_free(r);
        }
        nasm_free(sects[i]);
    }
    nasm_free(sects);
    saa_free(syms);
    raa_free(bsym);
    raa_free(symval);
    saa_free(strs);
}

static int coff_make_section(char *name, unsigned long flags)
{
    struct Section *s;

    s = nasm_malloc(sizeof(*s));

    if (flags != BSS_FLAGS)
        s->data = saa_init(1L);
    else
        s->data = NULL;
    s->head = NULL;
    s->tail = &s->head;
    s->len = 0;
    s->nrelocs = 0;
    if (!strcmp(name, ".text"))
        s->index = def_seg;
    else
        s->index = seg_alloc();
    strncpy(s->name, name, 8);
    s->name[8] = '\0';
    s->flags = flags;

    if (nsects >= sectlen)
        sects =
            nasm_realloc(sects, (sectlen += SECT_DELTA) * sizeof(*sects));
    sects[nsects++] = s;

    return nsects - 1;
}

static long coff_section_names(char *name, int pass, int *bits)
{
    char *p;
    unsigned long flags, align_and = ~0L, align_or = 0L;
    int i;

    /*
     * Default is 32 bits.
     */
    if (!name)
        *bits = 32;

    if (!name)
        return def_seg;

    p = name;
    while (*p && !isspace(*p))
        p++;
    if (*p)
        *p++ = '\0';
    if (strlen(name) > 8) {
        error(ERR_WARNING, "COFF section names limited to 8 characters:"
              " truncating");
        name[8] = '\0';
    }
    flags = 0;

    while (*p && isspace(*p))
        p++;
    while (*p) {
        char *q = p;
        while (*p && !isspace(*p))
            p++;
        if (*p)
            *p++ = '\0';
        while (*p && isspace(*p))
            p++;

        if (!nasm_stricmp(q, "code") || !nasm_stricmp(q, "text")) {
            flags = TEXT_FLAGS;
        } else if (!nasm_stricmp(q, "data")) {
            flags = DATA_FLAGS;
        } else if (!nasm_stricmp(q, "rdata")) {
            if (win32)
                flags = RDATA_FLAGS;
            else {
                flags = DATA_FLAGS;     /* gotta do something */
                error(ERR_NONFATAL, "standard COFF does not support"
                      " read-only data sections");
            }
        } else if (!nasm_stricmp(q, "bss")) {
            flags = BSS_FLAGS;
        } else if (!nasm_stricmp(q, "info")) {
            if (win32)
                flags = INFO_FLAGS;
            else {
                flags = DATA_FLAGS;     /* gotta do something */
                error(ERR_NONFATAL, "standard COFF does not support"
                      " informational sections");
            }
        } else if (!nasm_strnicmp(q, "align=", 6)) {
            if (!win32)
                error(ERR_NONFATAL, "standard COFF does not support"
                      " section alignment specification");
            else {
                if (q[6 + strspn(q + 6, "0123456789")])
                    error(ERR_NONFATAL,
                          "argument to `align' is not numeric");
                else {
                    unsigned int align = atoi(q + 6);
                    if (!align || ((align - 1) & align))
                        error(ERR_NONFATAL, "argument to `align' is not a"
                              " power of two");
                    else if (align > 64)
                        error(ERR_NONFATAL, "Win32 cannot align sections"
                              " to better than 64-byte boundaries");
                    else {
                        align_and = ~0x00F00000L;
                        align_or = (align == 1 ? 0x00100000L :
                                    align == 2 ? 0x00200000L :
                                    align == 4 ? 0x00300000L :
                                    align == 8 ? 0x00400000L :
                                    align == 16 ? 0x00500000L :
                                    align ==
                                    32 ? 0x00600000L : 0x00700000L);
                    }
                }
            }
        }
    }

    for (i = 0; i < nsects; i++)
        if (!strcmp(name, sects[i]->name))
            break;
    if (i == nsects) {
        if (!flags) {
            if (!strcmp(name, ".data"))
                flags = DATA_FLAGS;
            else if (!strcmp(name, ".rdata"))
                flags = RDATA_FLAGS;
            else if (!strcmp(name, ".bss"))
                flags = BSS_FLAGS;
            else
                flags = TEXT_FLAGS;
        }
        i = coff_make_section(name, flags);
        if (flags)
            sects[i]->flags = flags;
        sects[i]->flags &= align_and;
        sects[i]->flags |= align_or;
    } else if (pass == 1) {
        if (flags)
            error(ERR_WARNING, "section attributes ignored on"
                  " redeclaration of section `%s'", name);
    }

    return sects[i]->index;
}

static void coff_deflabel(char *name, long segment, long offset,
                          int is_global, char *special)
{
    int pos = strslen + 4;
    struct Symbol *sym;

    if (special)
        error(ERR_NONFATAL, "binary format does not support any"
              " special symbol types");

    if (name[0] == '.' && name[1] == '.' && name[2] != '@') {
        error(ERR_NONFATAL, "unrecognised special symbol `%s'", name);
        return;
    }

    if (strlen(name) > 8) {
        saa_wbytes(strs, name, (long)(1 + strlen(name)));
        strslen += 1 + strlen(name);
    } else
        pos = -1;

    sym = saa_wstruct(syms);

    sym->strpos = pos;
    if (pos == -1)
        strcpy(sym->name, name);
    sym->is_global = !!is_global;
    if (segment == NO_SEG)
        sym->section = -1;      /* absolute symbol */
    else {
        int i;
        sym->section = 0;
        for (i = 0; i < nsects; i++)
            if (segment == sects[i]->index) {
                sym->section = i + 1;
                break;
            }
        if (!sym->section)
            sym->is_global = TRUE;
    }
    if (is_global == 2)
        sym->value = offset;
    else
        sym->value = (sym->section == 0 ? 0 : offset);

    /*
     * define the references from external-symbol segment numbers
     * to these symbol records.
     */
    if (sym->section == 0)
        bsym = raa_write(bsym, segment, nsyms);

    if (segment != NO_SEG)
        symval = raa_write(symval, segment, sym->section ? 0 : sym->value);

    nsyms++;
}

static long coff_add_reloc(struct Section *sect, long segment,
                           int relative)
{
    struct Reloc *r;

    r = *sect->tail = nasm_malloc(sizeof(struct Reloc));
    sect->tail = &r->next;
    r->next = NULL;

    r->address = sect->len;
    if (segment == NO_SEG)
        r->symbol = 0, r->symbase = ABS_SYMBOL;
    else {
        int i;
        r->symbase = REAL_SYMBOLS;
        for (i = 0; i < nsects; i++)
            if (segment == sects[i]->index) {
                r->symbol = i * 2;
                r->symbase = SECT_SYMBOLS;
                break;
            }
        if (r->symbase == REAL_SYMBOLS)
            r->symbol = raa_read(bsym, segment);
    }
    r->relative = relative;

    sect->nrelocs++;

    /*
     * Return the fixup for standard COFF common variables.
     */
    if (r->symbase == REAL_SYMBOLS && !win32)
        return raa_read(symval, segment);
    else
        return 0;
}

static void coff_out(long segto, const void *data, unsigned long type,
                     long segment, long wrt)
{
    struct Section *s;
    long realbytes = type & OUT_SIZMASK;
    unsigned char mydata[4], *p;
    int i;

    if (wrt != NO_SEG) {
        wrt = NO_SEG;           /* continue to do _something_ */
        error(ERR_NONFATAL, "WRT not supported by COFF output formats");
    }