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NetBSD/usr.bin/elf2aout/elf2aout.c

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/* $NetBSD: elf2aout.c,v 1.6 1998/11/27 05:09:49 simonb 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. */
#include <sys/types.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>
/* Elf Program segment permissions, in program header flags field */
#define PF_X (1 << 0)/* Segment is executable */
#define PF_W (1 << 1)/* Segment is writable */
#define PF_R (1 << 2)/* Segment is readable */
#define PF_MASKPROC 0xF0000000 /* Processor-specific reserved bits */
struct sect {
unsigned long vaddr;
unsigned long len;
};
void combine __P((struct sect *, struct sect *, int));
int phcmp __P((const void *, const void *));
char *saveRead __P((int file, off_t offset, off_t len, char *name));
void copy __P((int, int, off_t, off_t));
void translate_syms __P((int, int, off_t, off_t, off_t, off_t));
int *symTypeTable;
int
main(int argc, char **argv)
{
Elf32_Ehdr ex;
Elf32_Phdr *ph;
Elf32_Shdr *sh;
char *shstrtab;
int strtabix, symtabix;
int i;
struct sect text, data, bss;
struct exec aex;
int infile, outfile;
unsigned long cur_vma = ULONG_MAX;
int symflag = 0;
strtabix = symtabix = 0;
text.len = data.len = bss.len = 0;
text.vaddr = data.vaddr = bss.vaddr = 0;
/* Check args... */
if (argc < 3 || argc > 4) {
usage:
fprintf(stderr,
"usage: elf2aout <elf executable> <a.out executable> [-s]\n");
exit(1);
}
if (argc == 4) {
if (strcmp(argv[3], "-s"))
goto usage;
symflag = 1;
}
/* Try the input file... */
if ((infile = open(argv[1], O_RDONLY)) < 0) {
fprintf(stderr, "Can't open %s for read: %s\n",
argv[1], strerror(errno));
exit(1);
}
/* Read the header, which is at the beginning of the file... */
i = read(infile, &ex, sizeof ex);
if (i != sizeof ex) {
fprintf(stderr, "ex: %s: %s.\n",
argv[1], i ? strerror(errno) : "End of file reached");
exit(1);
}
/* Read the program headers... */
ph = (Elf32_Phdr *) saveRead(infile, ex.e_phoff,
ex.e_phnum * sizeof(Elf32_Phdr), "ph");
/* Read the section headers... */
sh = (Elf32_Shdr *) saveRead(infile, ex.e_shoff,
ex.e_shnum * sizeof(Elf32_Shdr), "sh");
/* Read in the section string table. */
shstrtab = saveRead(infile, sh[ex.e_shstrndx].sh_offset,
sh[ex.e_shstrndx].sh_size, "shstrtab");
/* Find space for a table matching ELF section indices to a.out symbol
* types. */
symTypeTable = (int *) malloc(ex.e_shnum * sizeof(int));
if (!symTypeTable) {
fprintf(stderr, "symTypeTable: can't allocate.\n");
exit(1);
}
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
if (!strcmp(name, ".text") || !strcmp(name, ".rodata"))
symTypeTable[i] = N_TEXT;
else
if (!strcmp(name, ".data") || !strcmp(name, ".sdata") ||
!strcmp(name, ".lit4") || !strcmp(name, ".lit8"))
symTypeTable[i] = N_DATA;
else
if (!strcmp(name, ".bss") || !strcmp(name, ".sbss"))
symTypeTable[i] = N_BSS;
}
/* 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 == Elf_pt_null || ph[i].p_type == Elf_pt_note ||
ph[i].p_type == Elf_pt_phdr || ph[i].p_type == Elf_pt_mips_reginfo)
continue;
/* Section types we can't handle... */
else
if (ph[i].p_type != Elf_pt_load)
errx(1, "Program header %d 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) {
fprintf(stderr, "Sections ordering prevents a.out conversion.\n");
exit(1);
}
/* 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) {
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... */
aex.a_midmag = htonl((symflag << 26) | (MID_PMAX << 16) | OMAGIC);
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;
/* Make the output file... */
if ((outfile = open(argv[2], O_WRONLY | O_CREAT, 0777)) < 0) {
fprintf(stderr, "Unable to create %s: %s\n", argv[2], strerror(errno));
exit(1);
}
/* Truncate file... */
if (ftruncate(outfile, 0)) {
warn("ftruncate %s", argv[2]);
}
/* Write the header... */
i = write(outfile, &aex, sizeof aex);
if (i != sizeof aex) {
perror("aex: write");
exit(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 == Elf_pt_load && ph[i].p_filesz) {
if (cur_vma != ph[i].p_vaddr) {
unsigned long gap = ph[i].p_vaddr - cur_vma;
char obuf[1024];
if (gap > 65536)
errx(1,
"Intersegment gap (%ld bytes) too large.", (long) gap);
#ifdef DEBUG
warnx("Warning: %ld byte intersegment gap.",
(long)gap);
#endif
memset(obuf, 0, sizeof obuf);
while (gap) {
int count = write(outfile, obuf, (gap > sizeof obuf
? sizeof obuf : gap));
if (count < 0) {
fprintf(stderr, "Error writing gap: %s\n",
strerror(errno));
exit(1);
}
gap -= 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);
/* Looks like we won... */
exit(0);
}
/* 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(out, in, symoff, symsize, stroff, strsize)
int out, in;
off_t symoff, symsize;
off_t stroff, strsize;
{
#define SYMS_PER_PASS 64
Elf32_Sym inbuf[64];
struct nlist outbuf[64];
int i, remaining, cur;
char *oldstrings;
char *newstrings, *nsp;
int newstringsize;
/* Zero the unused fields in the output buffer.. */
memset(outbuf, 0, sizeof outbuf);
/* Find number of symbols to process... */
remaining = symsize / sizeof(Elf32_Sym);
/* Suck in the old string table... */
oldstrings = saveRead(in, stroff, strsize, "string table");
/* Allocate space for the new one. XXX We make the wild assumption
* that no two symbol table entries will point at the same place in
* the string table - if that assumption is bad, this could easily
* blow up. */
newstringsize = strsize + remaining;
newstrings = (char *) malloc(newstringsize);
if (!newstrings) {
fprintf(stderr, "No memory for new string table!\n");
exit(1);
}
/* Initialize the table pointer... */
nsp = newstrings;
/* Go the the start of the ELF symbol table... */
if (lseek(in, symoff, SEEK_SET) < 0) {
perror("translate_syms: lseek");
exit(1);
}
/* Translate and copy symbols... */
while (remaining) {
cur = remaining;
if (cur > SYMS_PER_PASS)
cur = SYMS_PER_PASS;
remaining -= cur;
if ((i = read(in, inbuf, cur * sizeof(Elf32_Sym)))
!= cur * sizeof(Elf32_Sym)) {
if (i < 0)
perror("translate_syms");
else
fprintf(stderr, "translate_syms: premature end of file.\n");
exit(1);
}
/* Do the translation... */
for (i = 0; i < cur; i++) {
int binding, type;
/* 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 += strlen(nsp) + 1;
type = ELF_SYM_TYPE(inbuf[i].st_info);
binding = ELF_SYM_BIND(inbuf[i].st_info);
/* Convert ELF symbol type/section/etc info into a.out
* type info. */
if (type == Elf_estt_file)
outbuf[i].n_type = N_FN;
else
if (inbuf[i].st_shndx == Elf_eshn_undefined)
outbuf[i].n_type = N_UNDF;
else
if (inbuf[i].st_shndx == Elf_eshn_absolute)
outbuf[i].n_type = N_ABS;
else
if (inbuf[i].st_shndx == Elf_eshn_common ||
inbuf[i].st_shndx == Elf_eshn_mips_acommon)
outbuf[i].n_type = N_COMM;
else
outbuf[i].n_type = symTypeTable[inbuf[i].st_shndx];
if (binding == Elf_estb_global)
outbuf[i].n_type |= N_EXT;
/* Symbol values in executables should be compatible. */
outbuf[i].n_value = inbuf[i].st_value;
}
/* Write out the symbols... */
if ((i = write(out, outbuf, cur * sizeof(struct nlist)))
!= cur * sizeof(struct nlist)) {
fprintf(stderr, "translate_syms: write: %s\n", strerror(errno));
exit(1);
}
}
/* Write out the string table length... */
if (write(out, &newstringsize, sizeof newstringsize)
!= sizeof newstringsize) {
fprintf(stderr,
"translate_syms: newstringsize: %s\n", strerror(errno));
exit(1);
}
/* Write out the string table... */
if (write(out, newstrings, newstringsize) != newstringsize) {
fprintf(stderr, "translate_syms: newstrings: %s\n", strerror(errno));
exit(1);
}
}
void
copy(out, in, offset, size)
int out, in;
off_t offset, size;
{
char ibuf[4096];
int remaining, cur, count;
/* Go the the start of the ELF symbol table... */
if (lseek(in, offset, SEEK_SET) < 0) {
perror("copy: lseek");
exit(1);
}
remaining = size;
while (remaining) {
cur = remaining;
if (cur > sizeof ibuf)
cur = sizeof ibuf;
remaining -= cur;
if ((count = read(in, ibuf, cur)) != cur) {
fprintf(stderr, "copy: read: %s\n",
count ? strerror(errno) : "premature end of file");
exit(1);
}
if ((count = write(out, ibuf, cur)) != cur) {
perror("copy: write");
exit(1);
}
}
}
/* Combine two segments, which must be contiguous. If pad is true, it's
okay for there to be padding between. */
void
combine(base, new, pad)
struct sect *base, *new;
int pad;
{
if (!base->len)
*base = *new;
else
if (new->len) {
if (base->vaddr + base->len != new->vaddr) {
if (pad)
base->len = new->vaddr - base->vaddr;
else {
fprintf(stderr,
"Non-contiguous data can't be converted.\n");
exit(1);
}
}
base->len += new->len;
}
}
int
phcmp(vh1, vh2)
const void *vh1, *vh2;
{
Elf32_Phdr *h1, *h2;
h1 = (Elf32_Phdr *) vh1;
h2 = (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;
}
char *
saveRead(int file, off_t offset, off_t len, char *name)
{
char *tmp;
int count;
off_t off;
if ((off = lseek(file, offset, SEEK_SET)) < 0) {
fprintf(stderr, "%s: fseek: %s\n", name, strerror(errno));
exit(1);
}
if (!(tmp = (char *) malloc(len)))
errx(1, "%s: Can't allocate %ld bytes.", name, (long)len);
count = read(file, tmp, len);
if (count != len) {
fprintf(stderr, "%s: read: %s.\n",
name, count ? strerror(errno) : "End of file reached");
exit(1);
}
return tmp;
}
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