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static void elf_deflabel(char *name, long segment, long offset, int is_global, char *special)
{
int pos = strslen;
struct Symbol *sym;
int special_used = FALSE;
#if defined(DEBUG) && DEBUG>2
fprintf(stderr, " elf_deflabel: %s, seg=%ld, off=%ld, is_global=%d, %s\n", name, segment, offset, is_global, special);
#endif
if (name[0] == '.' && name[1] == '.' && name[2] != '@') { /* label1: ; a non-local label
* .local: ; this is really label1.local
* ..@@foo: ; this is a special symbol
* label2: ; another non-local label
* .local: ; this is really label2.local
* jmp ..@@foo ; this will jump three lines up
*/
/*
* This is a NASM special symbol. We never allow it into
* the ELF symbol table, even if it's a valid one. If it
* _isn't_ a valid one, we should barf immediately.
*/
/* 要么是..@,要么是下面5个特殊符号之一，要么出错 */
if (strcmp(name, "..gotpc") && strcmp(name, "..gotoff") &&
strcmp(name, "..got") && strcmp(name, "..plt") &&
strcmp(name, "..sym"))
error(ERR_NONFATAL, "unrecognised special symbol `%s'", name);
return;
}
if (is_global == 3) { /* 已经定义的全局变量，在 nasm.c 中被调用 */
struct Symbol **s;
/*
* Fix up a forward-reference symbol size from the first
* pass.
*/
for (s = &fwds; *s; s = &(*s)->nextfwd)
if (!strcmp((*s)->name, name)) {
struct tokenval tokval;
expr *e;
char *p = special;
while (*p && !isspace(*p))
p++;
while (*p && isspace(*p))
p++;
stdscan_reset();
stdscan_bufptr = p;
tokval.t_type = TOKEN_INVALID;
e = evaluate(stdscan, NULL, &tokval, NULL, 1, error, NULL); /* 计算该全局变量的 size */
if (e) {
if (!is_simple(e))
error(ERR_NONFATAL, "cannot use relocatable expression as symbol size");
else
(*s)->size = reloc_value(e);
}
/*
* Remove it from the list of unresolved sizes.
*/
nasm_free((*s)->name);
*s = (*s)->nextfwd;
return;
}
return; /* it wasn't an important one */
}
saa_wbytes(strs, name, (long)(1 + strlen(name)));
strslen += 1 + strlen(name);
sym = saa_wstruct(syms);
sym->strpos = pos;
sym->type = is_global ? SYM_GLOBAL : 0;
sym->size = 0;
if (segment == NO_SEG)
sym->section = SHN_ABS;
else {
int i;
sym->section = SHN_UNDEF;
if (nsects == 0 && segment == def_seg) {
int tempint;
if (segment != elf_section_names(".text", 2, &tempint))
error(ERR_PANIC, "strange segment conditions in ELF driver");
sym->section = nsects;
} else {
for (i = 0; i < nsects; i++)
if (segment == sects[i]->index) {
sym->section = i + 1; /* ELF 中， section ID 从 1 开始计算，0 reserved */
break;
}
}
}
if (is_global == 2) { /* 在 define_common 中传递 2 作为参数 */
sym->size = offset;
sym->value = 0;
sym->section = SHN_COMMON;
/*
* We have a common variable. Check the special text to see
* if it's a valid number and power of two; if so, store it
* as the alignment for the common variable.
*/
if (special) {
int err;
sym->value = readnum(special, &err);
if (err)
error(ERR_NONFATAL, "alignment constraint `%s' is not a valid number", special);
else if ((sym->value | (sym->value - 1)) != 2 * sym->value - 1)
error(ERR_NONFATAL, "alignment constraint `%s' is not a power of two", special);
}
special_used = TRUE;
} else
sym->value = (sym->section == SHN_UNDEF ? 0 : offset);
if (sym->type == SYM_GLOBAL) {
/*
* There's a problem here that needs fixing.
* If sym->section == SHN_ABS, then the first line of the
* else section causes a core dump, because its a reference
* beyond the end of the section array.
* This behaviour is exhibited by this code:
* GLOBAL crash_nasm
* crash_nasm equ 0
*
* I'm not sure how to procede, because I haven't got the
* first clue about how ELF works, so I don't know what to
* do with it. Furthermore, I'm not sure what the rest of this
* section of code does. Help?
*
* For now, I'll see if doing absolutely nothing with it will
* work...
*/
if (sym->section == SHN_UNDEF || sym->section == SHN_COMMON) {
bsym = raa_write(bsym, segment, nglobs);
} else if (sym->section != SHN_ABS) {
/*
* This is a global symbol; so we must add it to the linked
* list of global symbols in its section. We'll push it on
* the beginning of the list, because it doesn't matter
* much which end we put it on and it's easier like this.
*
* In addition, we check the special text for symbol
* type and size information.
*/
sym->next = sects[sym->section - 1]->gsyms;
sects[sym->section - 1]->gsyms = sym;
if (special) { /* special 的类型只能是 function 或者 data, object */
int n = strcspn(special, " ");
if (!nasm_strnicmp(special, "function", n))
sym->type |= SYM_FUNCTION;
else if (!nasm_strnicmp(special, "data", n) || !nasm_strnicmp(special, "object", n))
sym->type |= SYM_DATA;
else
error(ERR_NONFATAL, "unrecognised symbol type `%.*s'", n, special);
if (special[n]) { /* global hashtable:data (hashtable.end - hashtable) */
struct tokenval tokval;
expr *e;
int fwd = FALSE;
char *saveme = stdscan_bufptr; /* bugfix? fbk 8/10/00 */
while (special[n] && isspace(special[n]))
n++;
/*
* We have a size expression; attempt to
* evaluate it.
*/
stdscan_reset();
stdscan_bufptr = special + n;
tokval.t_type = TOKEN_INVALID;
e = evaluate(stdscan, NULL, &tokval, &fwd, 0, error, NULL);
if (fwd) {
sym->nextfwd = fwds;
fwds = sym;
sym->name = nasm_strdup(name);
} else if (e) {
if (!is_simple(e))
error(ERR_NONFATAL, "cannot use relocatable expression as symbol size");
else
sym->size = reloc_value(e);
}
stdscan_bufptr = saveme; /* bugfix? fbk 8/10/00 */
}
special_used = TRUE;
}
}
sym->globnum = nglobs;
nglobs++;
} else
nlocals++;
if (special && !special_used)
error(ERR_NONFATAL, "no special symbol features supported here"); /* extern temp:dword 显示此出错信息 */
}
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