outelf64.c

nasm早期的源代码,比较简单是学习汇编和编译原理的好例子

        WRITEDLONG(p, (int64_t)sym->value);
        WRITEDLONG(p, (int64_t)sym->size);
        saa_wbytes(s, entry, 24L);
        *len += 24;
    }

    return s;
}

static struct SAA *elf_build_reltab(int32_t *len, struct Reloc *r)
{
    struct SAA *s;
    uint8_t *p, entry[24];

    if (!r)
        return NULL;

    s = saa_init(1L);
    *len = 0;

    while (r) {
        int64_t sym = r->symbol;

        if (sym >= GLOBAL_TEMP_BASE)
            sym += -GLOBAL_TEMP_BASE + (nsects + 3) + nlocals;

        p = entry;
        WRITEDLONG(p, r->address);
        WRITEDLONG(p, (sym << 32) + r->type);
	WRITEDLONG(p, (uint64_t) 0);
        saa_wbytes(s, entry, 24L);
        *len += 24;

        r = r->next;
    }

    return s;
}

static void elf_section_header(int name, int type, int flags,
                               void *data, bool is_saa, int32_t datalen,
                               int link, int info, int align, int eltsize)
{
    elf_sects[elf_nsect].data = data;
    elf_sects[elf_nsect].len = datalen;
    elf_sects[elf_nsect].is_saa = is_saa;
    elf_nsect++;

    fwriteint32_t((int32_t)name, elffp);
    fwriteint32_t((int32_t)type, elffp);
    fwriteint64_t((int64_t)flags, elffp);
    fwriteint64_t(0L, elffp);      /* no address, ever, in object files */
    fwriteint64_t(type == 0 ? 0L : elf_foffs, elffp);
    fwriteint64_t(datalen, elffp);
    if (data)
        elf_foffs += (datalen + SEG_ALIGN_1) & ~SEG_ALIGN_1;
    fwriteint32_t((int32_t)link, elffp);
    fwriteint32_t((int32_t)info, elffp);
    fwriteint64_t((int64_t)align, elffp);
    fwriteint64_t((int64_t)eltsize, elffp);
}

static void elf_write_sections(void)
{
    int i;
    for (i = 0; i < elf_nsect; i++)
        if (elf_sects[i].data) {
            int32_t len = elf_sects[i].len;
            int32_t reallen = (len + SEG_ALIGN_1) & ~SEG_ALIGN_1;
            int32_t align = reallen - len;
            if (elf_sects[i].is_saa)
                saa_fpwrite(elf_sects[i].data, elffp);
            else
                fwrite(elf_sects[i].data, len, 1, elffp);
            fwrite(align_str, align, 1, elffp);
        }
}

static void elf_sect_write(struct Section *sect,
                           const uint8_t *data, uint32_t len)
{
    saa_wbytes(sect->data, data, len);
    sect->len += len;
}

static int32_t elf_segbase(int32_t segment)
{
    return segment;
}

static int elf_directive(char *directive, char *value, int pass)
{
    (void)directive;
    (void)value;
    (void)pass;
    return 0;
}

static void elf_filename(char *inname, char *outname, efunc error)
{
    strcpy(elf_module, inname);
    standard_extension(inname, outname, ".o", error);
}

static const char *elf_stdmac[] = {
    "%define __SECT__ [section .text]",
    "%macro __NASM_CDecl__ 1",
    "%define $_%1 $%1",
    "%endmacro",
    NULL
};
static int elf_set_info(enum geninfo type, char **val)
{
    (void)type;
    (void)val;
    return 0;
}

static struct dfmt df_stabs = {
    "ELF64 (X86_64) stabs debug format for Linux",
    "stabs",
    stabs64_init,
    stabs64_linenum,
    stabs64_deflabel,
    stabs64_directive,
    stabs64_typevalue,
    stabs64_output,
    stabs64_cleanup
};

struct dfmt *elf64_debugs_arr[2] = { &df_stabs, NULL };

struct ofmt of_elf64 = {
    "ELF64 (x86_64) object files (e.g. Linux)",
    "elf64",
    NULL,
    elf64_debugs_arr,
    &null_debug_form,
    elf_stdmac,
    elf_init,
    elf_set_info,
    elf_out,
    elf_deflabel,
    elf_section_names,
    elf_segbase,
    elf_directive,
    elf_filename,
    elf_cleanup
};

/* again, the stabs debugging stuff (code) */

void stabs64_init(struct ofmt *of, void *id, FILE * fp, efunc error)
{
    (void)of;
    (void)id;
    (void)fp;
    (void)error;
}

void stabs64_linenum(const char *filename, int32_t linenumber, int32_t segto)
{
    (void)segto;

    if (!stabs_filename) {
        stabs_filename = (char *)nasm_malloc(strlen(filename) + 1);
        strcpy(stabs_filename, filename);
    } else {
        if (strcmp(stabs_filename, filename)) {
            /* yep, a memory leak...this program is one-shot anyway, so who cares...
               in fact, this leak comes in quite handy to maintain a list of files
               encountered so far in the symbol lines... */

            /* why not nasm_free(stabs_filename); we're done with the old one */

            stabs_filename = (char *)nasm_malloc(strlen(filename) + 1);
            strcpy(stabs_filename, filename);
        }
    }
    stabs_immcall = 1;
    currentline = linenumber;
}

void stabs64_deflabel(char *name, int32_t segment, int32_t offset, int is_global,
                    char *special)
{
    (void)name;
    (void)segment;
    (void)offset;
    (void)is_global;
    (void)special;
}

void stabs64_directive(const char *directive, const char *params)
{
    (void)directive;
    (void)params;
}

void stabs64_typevalue(int32_t type)
{
    (void)type;
}

void stabs64_output(int type, void *param)
{
    struct symlininfo *s;
    struct linelist *el;
    if (type == TY_STABSSYMLIN) {
        if (stabs_immcall) {
            s = (struct symlininfo *)param;
            if (strcmp(s->name, ".text"))
                return;         /* we are only interested in the text stuff */
            numlinestabs++;
            el = (struct linelist *)nasm_malloc(sizeof(struct linelist));
            el->info.offset = s->offset;
            el->info.section = s->section;
            el->info.name = s->name;
            el->line = currentline;
            el->filename = stabs_filename;
            el->next = 0;
            if (stabslines) {
                stabslines->last->next = el;
                stabslines->last = el;
            } else {
                stabslines = el;
                stabslines->last = el;
            }
        }
    }
    stabs_immcall = 0;
}

#define WRITE_STAB(p,n_strx,n_type,n_other,n_desc,n_value) \
  do {\
    WRITELONG(p,n_strx); \
    WRITECHAR(p,n_type); \
    WRITECHAR(p,n_other); \
    WRITESHORT(p,n_desc); \
    WRITELONG(p,n_value); \
  } while (0)

/* for creating the .stab , .stabstr and .rel.stab sections in memory */

void stabs64_generate(void)
{
    int i, numfiles, strsize, numstabs = 0, currfile, mainfileindex;
    uint8_t *sbuf, *ssbuf, *rbuf, *sptr, *rptr;
    char **allfiles;
    int *fileidx;

    struct linelist *ptr;

    ptr = stabslines;

    allfiles = (char **)nasm_malloc(numlinestabs * sizeof(int8_t *));
    for (i = 0; i < numlinestabs; i++)
        allfiles[i] = 0;
    numfiles = 0;
    while (ptr) {
        if (numfiles == 0) {
            allfiles[0] = ptr->filename;
            numfiles++;
        } else {
            for (i = 0; i < numfiles; i++) {
                if (!strcmp(allfiles[i], ptr->filename))
                    break;
            }
            if (i >= numfiles) {
                allfiles[i] = ptr->filename;
                numfiles++;
            }
        }
        ptr = ptr->next;
    }
    strsize = 1;
    fileidx = (int *)nasm_malloc(numfiles * sizeof(int));
    for (i = 0; i < numfiles; i++) {
        fileidx[i] = strsize;
        strsize += strlen(allfiles[i]) + 1;
    }
    mainfileindex = 0;
    for (i = 0; i < numfiles; i++) {
        if (!strcmp(allfiles[i], elf_module)) {
            mainfileindex = i;
            break;
        }
    }

    /* worst case size of the stab buffer would be:
       the sourcefiles changes each line, which would mean 1 SOL, 1 SYMLIN per line
     */
    sbuf =
        (uint8_t *)nasm_malloc((numlinestabs * 2 + 3) *
                                     sizeof(struct stabentry));

    ssbuf = (uint8_t *)nasm_malloc(strsize);

    rbuf = (uint8_t *)nasm_malloc(numlinestabs * 16 * (2 + 3));
    rptr = rbuf;

    for (i = 0; i < numfiles; i++) {
        strcpy((char *)ssbuf + fileidx[i], allfiles[i]);
    }
    ssbuf[0] = 0;

    stabstrlen = strsize;       /* set global variable for length of stab strings */

    sptr = sbuf;
    /* this is the first stab, its strx points to the filename of the
       the source-file, the n_desc field should be set to the number
       of remaining stabs
     */
    WRITE_STAB(sptr, fileidx[0], 0, 0, 0, strlen(allfiles[0] + 12));

    ptr = stabslines;
    numstabs = 0;

    if (ptr) {
        /* this is the stab for the main source file */
        WRITE_STAB(sptr, fileidx[mainfileindex], N_SO, 0, 0, 0);

        /* relocation table entry */

        /* Since the above WRITE_STAB calls have already */
        /* created two entries, the index in the info.section */
        /* member must be adjusted by adding 3 */

        WRITEDLONG(rptr, (int64_t)(sptr - sbuf) - 4);
	WRITELONG(rptr, R_X86_64_32);
	WRITELONG(rptr, ptr->info.section + 3);

        numstabs++;
        currfile = mainfileindex;
    }

    while (ptr) {
        if (strcmp(allfiles[currfile], ptr->filename)) {
            /* oops file has changed... */
            for (i = 0; i < numfiles; i++)
                if (!strcmp(allfiles[i], ptr->filename))
                    break;
            currfile = i;
            WRITE_STAB(sptr, fileidx[currfile], N_SOL, 0, 0,
                       ptr->info.offset);
            numstabs++;

            /* relocation table entry */

            WRITEDLONG(rptr, (int64_t)(sptr - sbuf) - 4);
	    WRITELONG(rptr, R_X86_64_32);
	    WRITELONG(rptr, ptr->info.section + 3);
        }

        WRITE_STAB(sptr, 0, N_SLINE, 0, ptr->line, ptr->info.offset);
        numstabs++;

        /* relocation table entry */

        WRITEDLONG(rptr, (int64_t)(sptr - sbuf) - 4);
	WRITELONG(rptr, R_X86_64_32);
	WRITELONG(rptr, ptr->info.section + 3);

        ptr = ptr->next;

    }

    ((struct stabentry *)sbuf)->n_desc = numstabs;

    nasm_free(allfiles);
    nasm_free(fileidx);

    stablen = (sptr - sbuf);
    stabrellen = (rptr - rbuf);
    stabrelbuf = rbuf;
    stabbuf = sbuf;
    stabstrbuf = ssbuf;
}

void stabs64_cleanup(void)
{
    struct linelist *ptr, *del;
    if (!stabslines)
        return;
    ptr = stabslines;
    while (ptr) {
        del = ptr;
        ptr = ptr->next;
        nasm_free(del);
    }
    if (stabbuf)
        nasm_free(stabbuf);
    if (stabrelbuf)
        nasm_free(stabrelbuf);
    if (stabstrbuf)
        nasm_free(stabstrbuf);
}

#endif                          /* OF_ELF */