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nasm/outelf.c
H. Peter Anvin ea8382740d NASM 0.93
2002-04-30 20:51:53 +00:00

745 lines
20 KiB
C
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/* outelf.c output routines for the Netwide Assembler to produce
* ELF32 (i386 of course) object file format
*
* 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 "nasm.h"
#include "nasmlib.h"
#include "outform.h"
#ifdef OF_ELF
struct Reloc {
struct Reloc *next;
long address; /* relative to _start_ of section */
long symbol; /* ELF symbol info thingy */
int relative; /* TRUE or FALSE */
};
struct Symbol {
long strpos; /* string table position of name */
long section; /* section ID of the symbol */
int type; /* TRUE or FALSE */
long value; /* address, or COMMON variable size */
};
#define SHT_PROGBITS 1
#define SHT_NOBITS 8
#define SHF_WRITE 1
#define SHF_ALLOC 2
#define SHF_EXECINSTR 4
struct Section {
struct SAA *data;
unsigned long len, size, nrelocs;
long index;
int type; /* SHT_PROGBITS or SHT_NOBITS */
int align; /* alignment: power of two */
unsigned long flags; /* section flags */
char *name;
struct SAA *rel;
long rellen;
struct Reloc *head, **tail;
};
#define SECT_DELTA 32
static struct Section **sects;
static int nsects, sectlen;
#define SHSTR_DELTA 256
static char *shstrtab;
static int shstrtablen, shstrtabsize;
static struct SAA *syms;
static unsigned long nlocals, nglobs;
static long def_seg;
static struct RAA *bsym;
static struct SAA *strs;
static unsigned long strslen;
static FILE *elffp;
static efunc error;
static char elf_module[FILENAME_MAX];
#define SHN_ABS 0xFFF1
#define SHN_COMMON 0xFFF2
#define SHN_UNDEF 0
#define SYM_SECTION 0x04
#define SYM_GLOBAL 0x10
#define GLOBAL_TEMP_BASE 6 /* bigger than any constant sym id */
#define SEG_ALIGN 16 /* alignment of sections in file */
#define SEG_ALIGN_1 (SEG_ALIGN-1)
static const char align_str[SEG_ALIGN] = ""; /* ANSI will pad this with 0s */
#define ELF_MAX_SECTIONS 16 /* really 10, but let's play safe */
static struct ELF_SECTDATA {
void *data;
long len;
int is_saa;
} elf_sects[ELF_MAX_SECTIONS];
static int elf_nsect;
static long elf_foffs;
static void elf_write(void);
static void elf_sect_write(struct Section *, unsigned char *, unsigned long);
static void elf_section_header (int, int, int, void *, int, long,
int, int, int, int);
static void elf_write_sections (void);
static struct SAA *elf_build_symtab (long *, long *);
static struct SAA *elf_build_reltab (long *, struct Reloc *);
static void add_sectname (char *, char *);
static void elf_init(FILE *fp, efunc errfunc, ldfunc ldef) {
elffp = fp;
error = errfunc;
(void) ldef; /* placate optimisers */
sects = NULL;
nsects = sectlen = 0;
syms = saa_init((long)sizeof(struct Symbol));
nlocals = nglobs = 0;
bsym = raa_init();
strs = saa_init(1L);
saa_wbytes (strs, "\0", 1L);
saa_wbytes (strs, elf_module, (long)(strlen(elf_module)+1));
strslen = 2+strlen(elf_module);
shstrtab = NULL;
shstrtablen = shstrtabsize = 0;;
add_sectname ("", "");
def_seg = seg_alloc();
}
static void elf_cleanup(void) {
struct Reloc *r;
int i;
elf_write();
fclose (elffp);
for (i=0; i<nsects; i++) {
if (sects[i]->type != SHT_NOBITS)
saa_free (sects[i]->data);
if (sects[i]->head)
saa_free (sects[i]->rel);
while (sects[i]->head) {
r = sects[i]->head;
sects[i]->head = sects[i]->head->next;
nasm_free (r);
}
}
nasm_free (sects);
saa_free (syms);
raa_free (bsym);
saa_free (strs);
}
static void add_sectname (char *firsthalf, char *secondhalf) {
int len = strlen(firsthalf)+strlen(secondhalf);
while (shstrtablen + len + 1 > shstrtabsize)
shstrtab = nasm_realloc (shstrtab, (shstrtabsize += SHSTR_DELTA));
strcpy (shstrtab+shstrtablen, firsthalf);
strcat (shstrtab+shstrtablen, secondhalf);
shstrtablen += len+1;
}
static int elf_make_section (char *name, int type, int flags, int align) {
struct Section *s;
s = nasm_malloc (sizeof(*s));
if (type != SHT_NOBITS)
s->data = saa_init (1L);
s->head = NULL;
s->tail = &s->head;
s->len = s->size = 0;
s->nrelocs = 0;
if (!strcmp(name, ".text"))
s->index = def_seg;
else
s->index = seg_alloc();
add_sectname ("", name);
s->name = nasm_malloc (1+strlen(name));
strcpy (s->name, name);
s->type = type;
s->flags = flags;
s->align = align;
if (nsects >= sectlen)
sects = nasm_realloc (sects, (sectlen += SECT_DELTA)*sizeof(*sects));
sects[nsects++] = s;
return nsects-1;
}
static long elf_section_names (char *name, int pass, int *bits) {
char *p;
int flags_and, flags_or, type, align, 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';
flags_and = flags_or = type = align = 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_strnicmp(q, "align=", 6)) {
align = atoi(q+6);
if (align == 0)
align = 1;
if ( (align-1) & align ) { /* means it's not a power of two */
error (ERR_NONFATAL, "section alignment %d is not"
" a power of two", align);
align = 1;
}
} else if (!nasm_stricmp(q, "alloc")) {
flags_and |= SHF_ALLOC;
flags_or |= SHF_ALLOC;
} else if (!nasm_stricmp(q, "noalloc")) {
flags_and |= SHF_ALLOC;
flags_or &= ~SHF_ALLOC;
} else if (!nasm_stricmp(q, "exec")) {
flags_and |= SHF_EXECINSTR;
flags_or |= SHF_EXECINSTR;
} else if (!nasm_stricmp(q, "noexec")) {
flags_and |= SHF_EXECINSTR;
flags_or &= ~SHF_EXECINSTR;
} else if (!nasm_stricmp(q, "write")) {
flags_and |= SHF_WRITE;
flags_or |= SHF_WRITE;
} else if (!nasm_stricmp(q, "nowrite")) {
flags_and |= SHF_WRITE;
flags_or &= ~SHF_WRITE;
} else if (!nasm_stricmp(q, "progbits")) {
type = SHT_PROGBITS;
} else if (!nasm_stricmp(q, "nobits")) {
type = SHT_NOBITS;
}
}
if (!strcmp(name, ".comment") ||
!strcmp(name, ".shstrtab") ||
!strcmp(name, ".symtab") ||
!strcmp(name, ".strtab")) {
error (ERR_NONFATAL, "attempt to redefine reserved section"
"name `%s'", name);
return NO_SEG;
}
for (i=0; i<nsects; i++)
if (!strcmp(name, sects[i]->name))
break;
if (i == nsects) {
if (!strcmp(name, ".text"))
i = elf_make_section (name, SHT_PROGBITS,
SHF_ALLOC | SHF_EXECINSTR, 16);
else if (!strcmp(name, ".data"))
i = elf_make_section (name, SHT_PROGBITS,
SHF_ALLOC | SHF_WRITE, 4);
else if (!strcmp(name, ".bss"))
i = elf_make_section (name, SHT_NOBITS,
SHF_ALLOC | SHF_WRITE, 4);
else
i = elf_make_section (name, SHT_PROGBITS, SHF_ALLOC, 1);
if (type)
sects[i]->type = type;
if (align)
sects[i]->align = align;
sects[i]->flags &= ~flags_and;
sects[i]->flags |= flags_or;
} else if (pass == 1) {
if (type || align || flags_and)
error (ERR_WARNING, "section attributes ignored on"
" redeclaration of section `%s'", name);
}
return sects[i]->index;
}
static void elf_deflabel (char *name, long segment, long offset,
int is_global) {
int pos = strslen;
struct Symbol *sym;
if (name[0] == '.' && name[1] == '.') {
return;
}
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;
if (segment == NO_SEG)
sym->section = SHN_ABS;
else {
int i;
sym->section = SHN_UNDEF;
for (i=0; i<nsects; i++)
if (segment == sects[i]->index) {
sym->section = i+1;
break;
}
}
if (is_global == 2) {
sym->value = offset;
sym->section = SHN_COMMON;
} else
sym->value = (sym->section == SHN_UNDEF ? 0 : offset);
if (sym->type == SYM_GLOBAL) {
if (sym->section == SHN_UNDEF || sym->section == SHN_COMMON)
bsym = raa_write (bsym, segment, nglobs);
nglobs++;
} else
nlocals++;
}
static void elf_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 = 2;
else {
int i;
r->symbol = 0;
for (i=0; i<nsects; i++)
if (segment == sects[i]->index)
r->symbol = i+3;
if (!r->symbol)
r->symbol = GLOBAL_TEMP_BASE + raa_read(bsym, segment);
}
r->relative = relative;
sect->nrelocs++;
}
static void elf_out (long segto, 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 ELF output format");
}
type &= OUT_TYPMASK;
/*
* handle absolute-assembly (structure definitions)
*/
if (segto == NO_SEG) {
if (type != OUT_RESERVE)
error (ERR_NONFATAL, "attempt to assemble code in [ABSOLUTE]"
" space");
return;
}
s = NULL;
for (i=0; i<nsects; i++)
if (segto == sects[i]->index) {
s = sects[i];
break;
}
if (!s) {
int tempint; /* ignored */
if (segto != elf_section_names (".text", 2, &tempint))
error (ERR_PANIC, "strange segment conditions in ELF driver");
else
s = sects[nsects-1];
}
if (s->type == SHT_NOBITS && type != OUT_RESERVE) {
error(ERR_WARNING, "attempt to initialise memory in"
" BSS section `%s': ignored", s->name);
if (type == OUT_REL2ADR)
realbytes = 2;
else if (type == OUT_REL4ADR)
realbytes = 4;
s->len += realbytes;
return;
}
if (type == OUT_RESERVE) {
if (s->type == SHT_PROGBITS) {
error(ERR_WARNING, "uninitialised space declared in"
" non-BSS section `%s': zeroing", s->name);
elf_sect_write (s, NULL, realbytes);
} else
s->len += realbytes;
} else if (type == OUT_RAWDATA) {
if (segment != NO_SEG)
error(ERR_PANIC, "OUT_RAWDATA with other than NO_SEG");
elf_sect_write (s, data, realbytes);
} else if (type == OUT_ADDRESS) {
if (wrt != NO_SEG)
error(ERR_NONFATAL, "ELF format does not support WRT types");
if (segment != NO_SEG) {
if (segment % 2) {
error(ERR_NONFATAL, "ELF format does not support"
" segment base references");
} else
elf_add_reloc (s, segment, FALSE);
}
p = mydata;
if (realbytes == 2 && segment != NO_SEG)
error (ERR_NONFATAL, "ELF format does not support 16-bit"
" relocations");
WRITELONG (p, *(long *)data);
elf_sect_write (s, mydata, realbytes);
} else if (type == OUT_REL2ADR) {
error (ERR_NONFATAL, "ELF format does not support 16-bit"
" relocations");
} else if (type == OUT_REL4ADR) {
if (segment == segto)
error(ERR_PANIC, "intra-segment OUT_REL4ADR");
if (segment != NO_SEG && segment % 2) {
error(ERR_NONFATAL, "ELF format does not support"
" segment base references");
} else
elf_add_reloc (s, segment, TRUE);
p = mydata;
WRITELONG (p, *(long*)data - realbytes);
elf_sect_write (s, mydata, 4L);
}
}
static void elf_write(void) {
int nsections, align;
char *p;
int commlen;
char comment[64];
int i;
struct SAA *symtab;
long symtablen, symtablocal;
/*
* Work out how many sections we will have. We have SHN_UNDEF,
* then the flexible user sections, then the four fixed
* sections `.comment', `.shstrtab', `.symtab' and `.strtab',
* then optionally relocation sections for the user sections.
*/
nsections = 5; /* SHN_UNDEF and the fixed ones */
add_sectname ("", ".comment");
add_sectname ("", ".shstrtab");
add_sectname ("", ".symtab");
add_sectname ("", ".strtab");
for (i=0; i<nsects; i++) {
nsections++; /* for the section itself */
if (sects[i]->head) {
nsections++; /* for its relocations */
add_sectname (".rel", sects[i]->name);
}
}
/*
* Do the comment.
*/
*comment = '\0';
commlen = 2+sprintf(comment+1, "The Netwide Assembler %s", NASM_VER);
/*
* Output the ELF header.
*/
fwrite ("\177ELF\1\1\1\0\0\0\0\0\0\0\0\0", 16, 1, elffp);
fwriteshort (1, elffp); /* ET_REL relocatable file */
fwriteshort (3, elffp); /* EM_386 processor ID */
fwritelong (1L, elffp); /* EV_CURRENT file format version */
fwritelong (0L, elffp); /* no entry point */
fwritelong (0L, elffp); /* no program header table */
fwritelong (0x40L, elffp); /* section headers straight after
* ELF header plus alignment */
fwritelong (0L, elffp); /* 386 defines no special flags */
fwriteshort (0x34, elffp); /* size of ELF header */
fwriteshort (0, elffp); /* no program header table, again */
fwriteshort (0, elffp); /* still no program header table */
fwriteshort (0x28, elffp); /* size of section header */
fwriteshort (nsections, elffp); /* number of sections */
fwriteshort (nsects+2, elffp); /* string table section index for
* section header table */
fwritelong (0L, elffp); /* align to 0x40 bytes */
fwritelong (0L, elffp);
fwritelong (0L, elffp);
/*
* Build the symbol table and relocation tables.
*/
symtab = elf_build_symtab (&symtablen, &symtablocal);
for (i=0; i<nsects; i++)
if (sects[i]->head)
sects[i]->rel = elf_build_reltab (&sects[i]->rellen,
sects[i]->head);
/*
* Now output the section header table.
*/
elf_foffs = 0x40 + 0x28 * nsections;
align = ((elf_foffs+SEG_ALIGN_1) & ~SEG_ALIGN_1) - elf_foffs;
elf_foffs += align;
elf_nsect = 0;
elf_section_header (0, 0, 0, NULL, FALSE, 0L, 0, 0, 0, 0); /* SHN_UNDEF */
p = shstrtab+1;
for (i=0; i<nsects; i++) {
elf_section_header (p - shstrtab, sects[i]->type, sects[i]->flags,
(sects[i]->type == SHT_PROGBITS ?
sects[i]->data : NULL), TRUE,
sects[i]->len, 0, 0, sects[i]->align, 0);
p += strlen(p)+1;
}
elf_section_header (p - shstrtab, 1, 0, comment, FALSE,
(long)commlen, 0, 0, 1, 0);/* .comment */
p += strlen(p)+1;
elf_section_header (p - shstrtab, 3, 0, shstrtab, FALSE,
(long)shstrtablen, 0, 0, 1, 0);/* .shstrtab */
p += strlen(p)+1;
elf_section_header (p - shstrtab, 2, 0, symtab, TRUE,
symtablen, nsects+4, symtablocal, 4, 16);/* .symtab */
p += strlen(p)+1;
elf_section_header (p - shstrtab, 3, 0, strs, TRUE,
strslen, 0, 0, 1, 0); /* .strtab */
for (i=0; i<nsects; i++) if (sects[i]->head) {
p += strlen(p)+1;
elf_section_header (p - shstrtab, 9, 0, sects[i]->rel, TRUE,
sects[i]->rellen, 6, i+1, 4, 8);
}
fwrite (align_str, align, 1, elffp);
/*
* Now output the sections.
*/
elf_write_sections();
saa_free (symtab);
}
static struct SAA *elf_build_symtab (long *len, long *local) {
struct SAA *s = saa_init(1L);
struct Symbol *sym;
unsigned char entry[16], *p;
int i;
*len = *local = 0;
/*
* First, an all-zeros entry, required by the ELF spec.
*/
saa_wbytes (s, NULL, 16L); /* null symbol table entry */
*len += 16;
(*local)++;
/*
* Next, an entry for the file name.
*/
p = entry;
WRITELONG (p, 1); /* we know it's 1st thing in strtab */
WRITELONG (p, 0); /* no value */
WRITELONG (p, 0); /* no size either */
WRITESHORT (p, 4); /* type FILE */
WRITESHORT (p, SHN_ABS);
saa_wbytes (s, entry, 16L);
*len += 16;
(*local)++;
/*
* Now some standard symbols defining the segments, for relocation
* purposes.
*/
for (i = 1; i <= nsects+1; i++) {
p = entry;
WRITELONG (p, 0); /* no symbol name */
WRITELONG (p, 0); /* offset zero */
WRITELONG (p, 0); /* size zero */
WRITESHORT (p, 3); /* local section-type thing */
WRITESHORT (p, (i==1 ? SHN_ABS : i-1)); /* the section id */
saa_wbytes (s, entry, 16L);
*len += 16;
(*local)++;
}
/*
* Now the other local symbols.
*/
saa_rewind (syms);
while ( (sym = saa_rstruct (syms)) ) {
if (sym->type == SYM_GLOBAL)
continue;
p = entry;
WRITELONG (p, sym->strpos);
WRITELONG (p, sym->value);
if (sym->section == SHN_COMMON)
WRITELONG (p, sym->value);
else
WRITELONG (p, 0);
WRITESHORT (p, 0); /* local non-typed thing */
WRITESHORT (p, sym->section);
saa_wbytes (s, entry, 16L);
*len += 16;
(*local)++;
}
/*
* Now the global symbols.
*/
saa_rewind (syms);
while ( (sym = saa_rstruct (syms)) ) {
if (sym->type != SYM_GLOBAL)
continue;
p = entry;
WRITELONG (p, sym->strpos);
WRITELONG (p, sym->value);
if (sym->section == SHN_COMMON)
WRITELONG (p, sym->value);
else
WRITELONG (p, 0);
WRITESHORT (p, SYM_GLOBAL); /* global non-typed thing */
WRITESHORT (p, sym->section);
saa_wbytes (s, entry, 16L);
*len += 16;
}
return s;
}
static struct SAA *elf_build_reltab (long *len, struct Reloc *r) {
struct SAA *s;
unsigned char *p, entry[8];
if (!r)
return NULL;
s = saa_init(1L);
*len = 0;
while (r) {
long sym = r->symbol;
if (sym >= GLOBAL_TEMP_BASE)
sym += -GLOBAL_TEMP_BASE + 6 + nlocals;
p = entry;
WRITELONG (p, r->address);
WRITELONG (p, (sym << 8) + (r->relative ? 2 : 1));
saa_wbytes (s, entry, 8L);
*len += 8;
r = r->next;
}
return s;
}
static void elf_section_header (int name, int type, int flags,
void *data, int is_saa, long 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++;
fwritelong ((long)name, elffp);
fwritelong ((long)type, elffp);
fwritelong ((long)flags, elffp);
fwritelong (0L, elffp); /* no address, ever, in object files */
fwritelong (type == 0 ? 0L : elf_foffs, elffp);
fwritelong (datalen, elffp);
if (data)
elf_foffs += (datalen+SEG_ALIGN_1) & ~SEG_ALIGN_1;
fwritelong ((long)link, elffp);
fwritelong ((long)info, elffp);
fwritelong ((long)align, elffp);
fwritelong ((long)eltsize, elffp);
}
static void elf_write_sections (void) {
int i;
for (i = 0; i < elf_nsect; i++)
if (elf_sects[i].data) {
long len = elf_sects[i].len;
long reallen = (len+SEG_ALIGN_1) & ~SEG_ALIGN_1;
long 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,
unsigned char *data, unsigned long len) {
saa_wbytes (sect->data, data, len);
sect->len += len;
}
static long elf_segbase (long segment) {
return segment;
}
static int elf_directive (char *directive, char *value, int pass) {
return 0;
}
static void elf_filename (char *inname, char *outname, efunc error) {
strcpy(elf_module, inname);
standard_extension (inname, outname, ".o", error);
}
struct ofmt of_elf = {
"ELF32 (i386) object files (e.g. Linux)",
"elf",
elf_init,
elf_out,
elf_deflabel,
elf_section_names,
elf_segbase,
elf_directive,
elf_filename,
elf_cleanup
};
#endif /* OF_ELF */
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