/* $NetBSD: elf2aout.c,v 1.25 2024/11/01 00:35:53 gutteridge Exp $ */
/*
* Copyright (c) 1995
* Ted Lemon (hereinafter referred to as the author)
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/* elf2aout.c
This program converts an elf executable to a NetBSD a.out executable.
The minimal symbol table is copied, but the debugging symbols and
other informational sections are not. */
#if HAVE_NBTOOL_CONFIG_H
#include "nbtool_config.h"
#endif
#ifndef TARGET_BYTE_ORDER
#define TARGET_BYTE_ORDER BYTE_ORDER
#endif
#include <sys/types.h>
#include <sys/endian.h>
#include <sys/exec_aout.h>
#include <sys/exec_elf.h>
#include <a.out.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
struct sect {
/* should be unsigned long, but assume no a.out binaries on LP64 */
uint32_t vaddr;
uint32_t len;
};
static void combine(struct sect *, struct sect *, int);
static int phcmp(const void *, const void *);
static void *saveRead(int file, off_t offset, size_t len, const char *name);
static void copy(int, int, off_t, off_t);
static void translate_syms(int, int, off_t, off_t, off_t, off_t);
#if TARGET_BYTE_ORDER != BYTE_ORDER
static void bswap32_region(int32_t* , int);
#endif
static int *symTypeTable;
static int debug;
static __dead void
usage(void)
{
fprintf(stderr, "Usage: %s [-Os] <elf executable> <a.out executable>\n",
getprogname());
exit(EXIT_FAILURE);
}
static const struct {
const char *n;
int v;
} nv[] = {
{ ".text", N_TEXT },
{ ".rodata", N_TEXT },
{ ".data", N_DATA },
{ ".sdata", N_DATA },
{ ".lit4", N_DATA },
{ ".lit8", N_DATA },
{ ".bss", N_BSS },
{ ".sbss", N_BSS },
};
static int
get_symtab_type(const char *name)
{
size_t i;
for (i = 0; i < __arraycount(nv); i++) {
if (strcmp(name, nv[i].n) == 0)
return nv[i].v;
}
if (debug)
warnx("section `%s' is not handled\n", name);
return 0;
}
static uint32_t
get_mid(const Elf32_Ehdr *ex)
{
switch (ex->e_machine) {
#ifdef notyet
case EM_AARCH64:
return MID_AARCH64;
case EM_ALPHA:
return MID_ALPHA;
#endif
case EM_ARM:
return MID_ARM6;
#ifdef notyet
case EM_PARISC:
return MID_HPPA;
#endif
case EM_386:
return MID_I386;
case EM_68K:
return MID_M68K;
case EM_OR1K:
return MID_OR1K;
case EM_MIPS:
if (ex->e_ident[EI_DATA] == ELFDATA2LSB)
return MID_PMAX;
else
return MID_MIPS;
case EM_PPC:
return MID_POWERPC;
#ifdef notyet
case EM_PPC64:
return MID_POWERPC64;
break;
#endif
case EM_RISCV:
return MID_RISCV;
case EM_SH:
return MID_SH3;
case EM_SPARC:
case EM_SPARC32PLUS:
case EM_SPARCV9:
if (ex->e_ident[EI_CLASS] == ELFCLASS32)
return MID_SPARC;
#ifdef notyet
return MID_SPARC64;
case EM_X86_64:
return MID_X86_64;
#else
break;
#endif
case EM_VAX:
return MID_VAX;
case EM_NONE:
return MID_ZERO;
default:
break;
}
if (debug)
warnx("Unsupported machine `%d'", ex->e_machine);
return MID_ZERO;
}
static unsigned char
get_type(Elf32_Half shndx)
{
switch (shndx) {
case SHN_UNDEF:
return N_UNDF;
case SHN_ABS:
return N_ABS;
case SHN_COMMON:
case SHN_MIPS_ACOMMON:
return N_COMM;
default:
return (unsigned char)symTypeTable[shndx];
}
}
int
main(int argc, char **argv)
{
Elf32_Ehdr ex;
Elf32_Phdr *ph;
Elf32_Shdr *sh;
char *shstrtab;
ssize_t i, strtabix, symtabix;
struct sect text, data, bss;
struct exec aex;
int infile, outfile;
uint32_t cur_vma = UINT32_MAX;
uint32_t mid;
int symflag = 0, c;
unsigned long magic = ZMAGIC;
strtabix = symtabix = 0;
text.len = data.len = bss.len = 0;
text.vaddr = data.vaddr = bss.vaddr = 0;
while ((c = getopt(argc, argv, "dOs")) != -1) {
switch (c) {
case 'd':
debug++;
break;
case 's':
symflag = 1;
break;
case 'O':
magic = OMAGIC;
break;
case '?':
default:
usage:
usage();
}
}
argc -= optind;
argv += optind;
/* Check args... */
if (argc != 2)
goto usage;
/* Try the input file... */
if ((infile = open(argv[0], O_RDONLY)) < 0)
err(EXIT_FAILURE, "Can't open `%s' for read", argv[0]);
/* Read the header, which is at the beginning of the file... */
i = read(infile, &ex, sizeof ex);
if (i != sizeof ex) {
if (i == -1)
err(EXIT_FAILURE, "Error reading `%s'", argv[1]);
else
errx(EXIT_FAILURE, "End of file reading `%s'", argv[1]);
}
#if TARGET_BYTE_ORDER != BYTE_ORDER
ex.e_type = bswap16(ex.e_type);
ex.e_machine = bswap16(ex.e_machine);
ex.e_version = bswap32(ex.e_version);
ex.e_entry = bswap32(ex.e_entry);
ex.e_phoff = bswap32(ex.e_phoff);
ex.e_shoff = bswap32(ex.e_shoff);
ex.e_flags = bswap32(ex.e_flags);
ex.e_ehsize = bswap16(ex.e_ehsize);
ex.e_phentsize = bswap16(ex.e_phentsize);
ex.e_phnum = bswap16(ex.e_phnum);
ex.e_shentsize = bswap16(ex.e_shentsize);
ex.e_shnum = bswap16(ex.e_shnum);
ex.e_shstrndx = bswap16(ex.e_shstrndx);
#endif
// Not yet
if (ex.e_ident[EI_CLASS] == ELFCLASS64)
errx(EXIT_FAILURE, "Only 32 bit is supported");
/* Read the program headers... */
ph = saveRead(infile, ex.e_phoff,
(size_t)ex.e_phnum * sizeof(Elf32_Phdr), "ph");
#if TARGET_BYTE_ORDER != BYTE_ORDER
bswap32_region((int32_t*)ph, sizeof(Elf32_Phdr) * ex.e_phnum);
#endif
/* Read the section headers... */
sh = saveRead(infile, ex.e_shoff,
(size_t)ex.e_shnum * sizeof(Elf32_Shdr), "sh");
#if TARGET_BYTE_ORDER != BYTE_ORDER
bswap32_region((int32_t*)sh, sizeof(Elf32_Shdr) * ex.e_shnum);
#endif
/* Read in the section string table. */
shstrtab = saveRead(infile, sh[ex.e_shstrndx].sh_offset,
(size_t)sh[ex.e_shstrndx].sh_size, "shstrtab");
/* Find space for a table matching ELF section indices to a.out symbol
* types. */
symTypeTable = malloc(ex.e_shnum * sizeof(int));
if (symTypeTable == NULL)
err(EXIT_FAILURE, "symTypeTable: can't allocate");
memset(symTypeTable, 0, ex.e_shnum * sizeof(int));
/* Look for the symbol table and string table... Also map section
* indices to symbol types for a.out */
for (i = 0; i < ex.e_shnum; i++) {
char *name = shstrtab + sh[i].sh_name;
if (!strcmp(name, ".symtab"))
symtabix = i;
else if (!strcmp(name, ".strtab"))
strtabix = i;
else
symTypeTable[i] = get_symtab_type(name);
}
/* Figure out if we can cram the program header into an a.out
* header... Basically, we can't handle anything but loadable
* segments, but we can ignore some kinds of segments. We can't
* handle holes in the address space, and we handle start addresses
* other than 0x1000 by hoping that the loader will know where to load
* - a.out doesn't have an explicit load address. Segments may be
* out of order, so we sort them first. */
qsort(ph, ex.e_phnum, sizeof(Elf32_Phdr), phcmp);
for (i = 0; i < ex.e_phnum; i++) {
/* Section types we can ignore... */
if (ph[i].p_type == PT_NULL || ph[i].p_type == PT_NOTE ||
ph[i].p_type == PT_PHDR || ph[i].p_type == PT_MIPS_REGINFO)
continue;
/* Section types we can't handle... */
if (ph[i].p_type == PT_TLS) {
if (debug)
warnx("Can't handle TLS section");
continue;
}
if (ph[i].p_type != PT_LOAD)
errx(EXIT_FAILURE, "Program header %zd "
"type %d can't be converted.", i, ph[i].p_type);
/* Writable (data) segment? */
if (ph[i].p_flags & PF_W) {
struct sect ndata, nbss;
ndata.vaddr = ph[i].p_vaddr;
ndata.len = ph[i].p_filesz;
nbss.vaddr = ph[i].p_vaddr + ph[i].p_filesz;
nbss.len = ph[i].p_memsz - ph[i].p_filesz;
combine(&data, &ndata, 0);
combine(&bss, &nbss, 1);
} else {
struct sect ntxt;
ntxt.vaddr = ph[i].p_vaddr;
ntxt.len = ph[i].p_filesz;
combine(&text, &ntxt, 0);
}
/* Remember the lowest segment start address. */
if (ph[i].p_vaddr < cur_vma)
cur_vma = ph[i].p_vaddr;
}
/* Sections must be in order to be converted... */
if (text.vaddr > data.vaddr || data.vaddr > bss.vaddr ||
text.vaddr + text.len > data.vaddr ||
data.vaddr + data.len > bss.vaddr)
errx(EXIT_FAILURE, "Sections ordering prevents a.out "
"conversion.");
/* If there's a data section but no text section, then the loader
* combined everything into one section. That needs to be the text
* section, so just make the data section zero length following text. */
if (data.len && text.len == 0) {
text = data;
data.vaddr = text.vaddr + text.len;
data.len = 0;
}
/* If there is a gap between text and data, we'll fill it when we copy
* the data, so update the length of the text segment as represented
* in a.out to reflect that, since a.out doesn't allow gaps in the
* program address space. */
if (text.vaddr + text.len < data.vaddr)
text.len = data.vaddr - text.vaddr;
/* We now have enough information to cons up an a.out header... */
mid = get_mid(&ex);
aex.a_midmag = (u_long)htobe32(((u_long)symflag << 26)
| ((u_long)mid << 16) | magic);
aex.a_text = text.len;
aex.a_data = data.len;
aex.a_bss = bss.len;
aex.a_entry = ex.e_entry;
aex.a_syms = (sizeof(struct nlist) *
(symtabix != -1 ? sh[symtabix].sh_size / sizeof(Elf32_Sym) : 0));
aex.a_trsize = 0;
aex.a_drsize = 0;
#if TARGET_BYTE_ORDER != BYTE_ORDER
aex.a_text = bswap32(aex.a_text);
aex.a_data = bswap32(aex.a_data);
aex.a_bss = bswap32(aex.a_bss);
aex.a_entry = bswap32(aex.a_entry);
aex.a_syms = bswap32(aex.a_syms);
aex.a_trsize = bswap32(aex.a_trsize);
aex.a_drsize = bswap32(aex.a_drsize);
#endif
/* Make the output file... */
if ((outfile = open(argv[1], O_WRONLY | O_CREAT, 0777)) < 0)
err(EXIT_FAILURE, "Unable to create `%s'", argv[1]);
/* Truncate file... */
if (ftruncate(outfile, 0)) {
warn("ftruncate %s", argv[1]);
}
/* Write the header... */
i = write(outfile, &aex, sizeof aex);
if (i != sizeof aex)
err(EXIT_FAILURE, "Can't write `%s'", argv[1]);
/* Copy the loadable sections. Zero-fill any gaps less than 64k;
* complain about any zero-filling, and die if we're asked to
* zero-fill more than 64k. */
for (i = 0; i < ex.e_phnum; i++) {
/* Unprocessable sections were handled above, so just verify
* that the section can be loaded before copying. */
if (ph[i].p_type == PT_LOAD && ph[i].p_filesz) {
if (cur_vma != ph[i].p_vaddr) {
uint32_t gap = ph[i].p_vaddr - cur_vma;
char obuf[1024];
if (gap > 65536)
errx(EXIT_FAILURE,
"Intersegment gap (%u bytes) too large", gap);
if (debug)
warnx("%u byte intersegment gap", gap);
memset(obuf, 0, sizeof obuf);
while (gap) {
ssize_t count = write(outfile, obuf,
(gap > sizeof obuf
? sizeof obuf : gap));
if (count < 0)
err(EXIT_FAILURE,
"Error writing gap");
gap -= (uint32_t)count;
}
}
copy(outfile, infile, ph[i].p_offset, ph[i].p_filesz);
cur_vma = ph[i].p_vaddr + ph[i].p_filesz;
}
}
/* Copy and translate the symbol table... */
translate_syms(outfile, infile,
sh[symtabix].sh_offset, sh[symtabix].sh_size,
sh[strtabix].sh_offset, sh[strtabix].sh_size);
free(ph);
free(sh);
free(shstrtab);
free(symTypeTable);
/* Looks like we won... */
return EXIT_SUCCESS;
}
/* translate_syms (out, in, offset, size)
Read the ELF symbol table from in at offset; translate it into a.out
nlist format and write it to out. */
void
translate_syms(int out, int in, off_t symoff, off_t symsize,
off_t stroff, off_t strsize)
{
#define SYMS_PER_PASS 64
Elf32_Sym inbuf[64];
struct nlist outbuf[64];
ssize_t i, remaining, cur;
char *oldstrings;
char *newstrings, *nsp;
size_t newstringsize;
uint32_t stringsizebuf;
/* Zero the unused fields in the output buffer.. */
memset(outbuf, 0, sizeof outbuf);
/* Find number of symbols to process... */
remaining = (ssize_t)(symsize / (off_t)sizeof(Elf32_Sym));
/* Suck in the old string table... */
oldstrings = saveRead(in, stroff, (size_t)strsize, "string table");
/*
* Allocate space for the new one. We will increase the space if
* this is too small
*/
newstringsize = (size_t)(strsize + remaining);
newstrings = malloc(newstringsize);
if (newstrings == NULL)
err(EXIT_FAILURE, "No memory for new string table!");
/* Initialize the table pointer... */
nsp = newstrings;
/* Go the start of the ELF symbol table... */
if (lseek(in, symoff, SEEK_SET) < 0)
err(EXIT_FAILURE, "Can't seek");
/* Translate and copy symbols... */
for (; remaining; remaining -= cur) {
cur = remaining;
if (cur > SYMS_PER_PASS)
cur = SYMS_PER_PASS;
if ((i = read(in, inbuf, (size_t)cur * sizeof(Elf32_Sym)))
!= cur * (ssize_t)sizeof(Elf32_Sym)) {
if (i < 0)
err(EXIT_FAILURE, "%s: read error", __func__);
else
errx(EXIT_FAILURE, "%s: premature end of file",
__func__);
}
/* Do the translation... */
for (i = 0; i < cur; i++) {
int binding, type;
size_t off, len;
#if TARGET_BYTE_ORDER != BYTE_ORDER
inbuf[i].st_name = bswap32(inbuf[i].st_name);
inbuf[i].st_value = bswap32(inbuf[i].st_value);
inbuf[i].st_size = bswap32(inbuf[i].st_size);
inbuf[i].st_shndx = bswap16(inbuf[i].st_shndx);
#endif
off = (size_t)(nsp - newstrings);
/* length of this symbol with leading '_' and trailing '\0' */
len = strlen(oldstrings + inbuf[i].st_name) + 1 + 1;
/* Does it fit? If not make more space */
if (newstringsize - off < len) {
char *nns;
newstringsize += (size_t)(remaining) * len;
nns = realloc(newstrings, newstringsize);
if (nns == NULL)
err(EXIT_FAILURE, "No memory for new string table!");
newstrings = nns;
nsp = newstrings + off;
}
/* Copy the symbol into the new table, but prepend an
* underscore. */
*nsp = '_';
strcpy(nsp + 1, oldstrings + inbuf[i].st_name);
outbuf[i].n_un.n_strx = nsp - newstrings + 4;
nsp += len;
type = ELF32_ST_TYPE(inbuf[i].st_info);
binding = ELF32_ST_BIND(inbuf[i].st_info);
/* Convert ELF symbol type/section/etc info into a.out
* type info. */
if (type == STT_FILE)
outbuf[i].n_type = N_FN;
else
outbuf[i].n_type = get_type(inbuf[i].st_shndx);
if (binding == STB_GLOBAL)
outbuf[i].n_type |= N_EXT;
/* Symbol values in executables should be compatible. */
outbuf[i].n_value = inbuf[i].st_value;
#if TARGET_BYTE_ORDER != BYTE_ORDER
outbuf[i].n_un.n_strx = bswap32(outbuf[i].n_un.n_strx);
outbuf[i].n_desc = bswap16(outbuf[i].n_desc);
outbuf[i].n_value = bswap32(outbuf[i].n_value);
#endif
}
/* Write out the symbols... */
if ((i = write(out, outbuf, (size_t)cur * sizeof(struct nlist)))
!= cur * (ssize_t)sizeof(struct nlist))
err(EXIT_FAILURE, "%s: write failed", __func__);
}
/* Write out the string table length... */
stringsizebuf = (uint32_t)newstringsize;
#if TARGET_BYTE_ORDER != BYTE_ORDER
stringsizebuf = bswap32(stringsizebuf);
#endif
if (write(out, &stringsizebuf, sizeof stringsizebuf)
!= sizeof stringsizebuf)
err(EXIT_FAILURE, "%s: newstringsize: write failed", __func__);
/* Write out the string table... */
if (write(out, newstrings, newstringsize) != (ssize_t)newstringsize)
err(EXIT_FAILURE, "%s: newstrings: write failed", __func__);
free(newstrings);
free(oldstrings);
}
static void
copy(int out, int in, off_t offset, off_t size)
{
char ibuf[4096];
ssize_t remaining, cur, count;
/* Go to the start of the segment... */
if (lseek(in, offset, SEEK_SET) < 0)
err(EXIT_FAILURE, "%s: lseek failed", __func__);
if (size > SSIZE_MAX)
err(EXIT_FAILURE, "%s: can not copy this much", __func__);
remaining = (ssize_t)size;
while (remaining) {
cur = remaining;
if (cur > (int)sizeof ibuf)
cur = sizeof ibuf;
remaining -= cur;
if ((count = read(in, ibuf, (size_t)cur)) != cur) {
if (count < 0)
err(EXIT_FAILURE, "%s: read error", __func__);
else
errx(EXIT_FAILURE, "%s: premature end of file",
__func__);
}
if ((count = write(out, ibuf, (size_t)cur)) != cur)
err(EXIT_FAILURE, "%s: write failed", __func__);
}
}
/* Combine two segments, which must be contiguous. If pad is true, it's
okay for there to be padding between. */
static void
combine(struct sect *base, struct sect *new, int pad)
{
if (base->len == 0)
*base = *new;
else
if (new->len) {
if (base->vaddr + base->len != new->vaddr) {
if (pad)
base->len = new->vaddr - base->vaddr;
else
errx(EXIT_FAILURE, "Non-contiguous "
"data can't be converted");
}
base->len += new->len;
}
}
static int
phcmp(const void *vh1, const void *vh2)
{
const Elf32_Phdr *h1, *h2;
h1 = (const Elf32_Phdr *)vh1;
h2 = (const Elf32_Phdr *)vh2;
if (h1->p_vaddr > h2->p_vaddr)
return 1;
else
if (h1->p_vaddr < h2->p_vaddr)
return -1;
else
return 0;
}
static void *
saveRead(int file, off_t offset, size_t len, const char *name)
{
char *tmp;
ssize_t count;
off_t off;
if ((off = lseek(file, offset, SEEK_SET)) < 0)
errx(EXIT_FAILURE, "%s: seek failed", name);
if ((tmp = malloc(len)) == NULL)
errx(EXIT_FAILURE,
"%s: Can't allocate %jd bytes.", name, (intmax_t)len);
count = read(file, tmp, len);
if ((size_t)count != len) {
if (count < 0)
err(EXIT_FAILURE, "%s: read error", name);
else
errx(EXIT_FAILURE, "%s: premature end of file",
name);
}
return tmp;
}
#if TARGET_BYTE_ORDER != BYTE_ORDER
/* swap a 32bit region */
static void
bswap32_region(int32_t* p, int len)
{
size_t i;
for (i = 0; i < len / sizeof(int32_t); i++, p++)
*p = bswap32(*p);
}
#endif
