/*
* Simple tool to produce an utterly basic ELF executable
* from an absolute ack.out file. Suitable for operating
* systems like Linux.
*
* This tool produces an executable with a program header
* only and no section header.
*
* Mostly pinched from the ARM cv (and then rewritten in
* ANSI C). Which, according to the comment, was pinched
* from m68k2; therefore I am merely continuing a time-
* honoured tradition.
*
* (I was 10 when the original for this was checked into
* CVS...)
*
* dtrg, 2006-10-17
*/
#include <stdlib.h>
#include <stdio.h>
#include <stdarg.h>
#include <stdint.h>
#include <stdbool.h>
#include <string.h>
#include <inttypes.h>
#include <unistd.h>
#include <sys/stat.h>
#include "out.h"
#define ASSERT(x) switch (2) { case 0: case (x): ; }
/* Global settings. */
int bigendian = 0;
int elfabi = 3; /* abi = Linux */
int elfmachine = 3; /* machine = EM_386 */
uint32_t elfflags = 0; /* elf processor flags */
/* Header and section table of an ack object file. */
struct outhead outhead;
struct outsect outsect[S_MAX];
struct outname* outname = NULL;
char* stringarea;
uint32_t ack_off_char;
int nstab = 0; /* S_STB symbol count */
int nsym = 0; /* other symbol count */
int nlocal = 0; /* local symbols */
char* outputfile = NULL; /* Name of output file, or NULL */
char* program; /* Name of current program: argv[0] */
FILE* input; /* Input stream */
FILE* output; /* Output stream */
#define readf(a, b, c) fread((a), (b), (int)(c), input)
#define writef(a, b, c) fwrite((a), (b), (int)(c), output)
/* Contents of an ELF object file. */
#define ELF_HEADER_SIZE 0x34
#define PROGRAM_HEADER_SIZE 0x20
#define PROGRAM_HEADER_COUNT 1
#define SECTION_HEADER_SIZE 0x28
#define STAB_SYMBOL_SIZE 12
#define ELF_SYMBOL_SIZE 16
uint32_t code_offset; /* ELF segment */
uint32_t stab_offset; /* Debugger symbol table */
uint32_t symtab_offset; /* ELF symbol table */
uint32_t strtab_offset; /* String table */
uint32_t shstrtab_offset; /* Section header string table */
uint32_t sh_offset; /* ELF section headers */
int sh_count = 0; /* Number of ELF sections */
int shstrtab_nr = 0; /* Section number of .shstrtab */
int shstrtab_size;
const char elf_le_ident_string[] = {
0x7F, 'E', 'L', 'F'
};
bool verbose = false;
/* Segment numbers understood by aelflod. */
enum {
TEXT = 0,
ROM,
DATA,
BSS,
NUM_SEGMENTS
};
/*
* ELF section numbers count up in the order that we write the ELF
* section headers. If we have no debugger symbols, we will skip
* .stab and .stabstr, then subtract 2 from all later numbers.
*/
enum {
N_UNDEF = 0,
N_TEXT,
N_RODATA,
N_DATA,
N_BSS,
N_STAB,
N_STABSTR,
N_SYMTAB,
N_STRTAB,
N_SHSTRTAB,
NUM_ELF_SECTIONS,
};
const char shstrtab[] =
"\0.text\0.rodata\0.data\0.bss\0.stab\0.stabstr\0"
".symtab\0.strtab\0.shstrtab";
/* Compiler appends one more "\0". */
const int sh_name[] = {
/* Index of each name in shstrtab: */
0, 1, 7, 15, 21, 26, 32,
41, 49, 57,
};
/* Produce an error message and exit. */
void fatal(const char* s, ...)
{
va_list ap;
fprintf(stderr, "%s: ",program) ;
va_start(ap, s);
vfprintf(stderr, s, ap);
va_end(ap);
fprintf(stderr, "\n");
if (outputfile)
unlink(outputfile);
exit(1);
}
/* Calculate the result of a aligned to b (rounding up if necessary).
* b must be a power of two. */
long align(long a, long b)
{
a += b - 1;
return a & ~(b-1);
}
int follows(struct outsect* pa, struct outsect* pb)
{
/* return 1 if pa follows pb */
return (pa->os_base >= align(pb->os_base+pb->os_size, pa->os_lign));
}
/* Convert a symbol's name index from ack.out to ELF. */
uint32_t cvname(struct outname* n)
{
if (n->on_foff) {
/* ack.out: offset from beginning of file
* ELF: index in string table
* the + 1 because we prepend a '\0' */
return n->on_foff - ack_off_char + 1;
} else
return 0; /* no name */
}
/* Convert a symbol's type and binding from ack.out to ELF. */
int cvinfo(struct outname* n)
{
int bind, type;
switch (n->on_type & S_ETC) {
case S_SCT:
type = 3; /* STT_SECTION */
break;
case S_FIL:
case S_MOD:
type = 4; /* STT_FILE */
break;
default:
switch (n->on_type & S_TYP) {
case S_MIN + TEXT:
type = 2; /* STT_FUNC */
break;
case S_MIN + ROM:
case S_MIN + DATA:
case S_MIN + BSS:
case S_MIN + NUM_SEGMENTS:
type = 1; /* STT_OBJECT */
break;
default:
type = 0; /* STT_NOTYPE */
break;
}
break;
}
if (n->on_type & S_EXT)
bind = 1; /* STB_GLOBAL */
else
bind = 0; /* STB_LOCAL */
return (bind << 4) | type;
}
/* Convert a symbol's section index from ack.out to ELF. */
int cvsect(struct outname* n)
{
switch (n->on_type & S_TYP) {
case S_ABS:
return 0xfff1; /* SHN_ABS */
case S_MIN + TEXT:
return N_TEXT;
case S_MIN + ROM:
return N_RODATA;
case S_MIN + DATA:
return N_DATA;
case S_MIN + BSS:
case S_MIN + NUM_SEGMENTS:
return N_BSS;
default:
return N_UNDEF;
}
}
/* Writes a byte. */
void emit8(unsigned char value)
{
writef(&value, 1, 1);
}
/* Writes out 16 and 32 bit words in the appropriate endianness. */
void emit16(unsigned short value)
{
unsigned char buffer[2];
if (bigendian)
{
buffer[0] = (value >> 8) & 0xFF;
buffer[1] = (value >> 0) & 0xFF;
}
else
{
buffer[1] = (value >> 8) & 0xFF;
buffer[0] = (value >> 0) & 0xFF;
}
writef(buffer, 1, sizeof(buffer));
}
void emit32(unsigned long value)
{
unsigned char buffer[4];
if (bigendian)
{
buffer[0] = (value >> 24) & 0xFF;
buffer[1] = (value >> 16) & 0xFF;
buffer[2] = (value >> 8) & 0xFF;
buffer[3] = (value >> 0) & 0xFF;
}
else
{
buffer[3] = (value >> 24) & 0xFF;
buffer[2] = (value >> 16) & 0xFF;
buffer[1] = (value >> 8) & 0xFF;
buffer[0] = (value >> 0) & 0xFF;
}
writef(buffer, 1, sizeof(buffer));
}
/* Copies the contents of a section from the input stream
* to the output stream. */
void emits(struct outsect* section)
{
char buffer[BUFSIZ];
long n = section->os_flen;
while (n > 0)
{
int blocksize = (n > BUFSIZ) ? BUFSIZ : n;
readf(buffer, 1, blocksize);
writef(buffer, 1, blocksize);
n -= blocksize;
}
/* Zero fill any remaining space. */
if (section->os_flen != section->os_size)
{
long n = section->os_size - section->os_flen;
memset(buffer, 0, BUFSIZ);
while (n > 0)
{
int blocksize = (n > BUFSIZ) ? BUFSIZ : n;
writef(buffer, 1, blocksize);
n -= blocksize;
}
}
}
/* Writes out an ELF program header. */
void emitphdr(unsigned long address, unsigned long filesize,
unsigned int memsize, unsigned int alignment, int flags)
{
static unsigned long fileoffset = 0;
emit32(1); /* type = PT_LOAD */
emit32(fileoffset); /* file offset */
emit32(address); /* virtual address */
emit32(0); /* physical address */
emit32(filesize); /* file size */
emit32(memsize); /* memory size */
emit32(flags); /* executable, readable, writable */
emit32(alignment); /* alignment */
fileoffset += filesize;
}
/* The next few functions write parts of the symbol table. */
void emit_stab(void)
{
struct outname* n;
int i;
for (i = 0; i < outhead.oh_nname; i++) {
n = &outname[i];
if (n->on_type & S_STB) {
emit32(cvname(n)); /* name index */
emit8(n->on_type >> 8); /* type */
emit8(cvsect(n)); /* section */
emit16(n->on_desc); /* desc */
emit32(n->on_valu); /* value */
}
}
}
void emit_symtab(void)
{
struct outname* n;
int i, pass;
bool global;
/* ELF .symtab must have local symbols before other symbols.
* We emit locals in pass 0, globals in pass 1. */
for (pass = 0; pass < 2; pass++) {
for (i = 0; i < outhead.oh_nname; i++) {
n = &outname[i];
/* Don't emit .stab symbol in .symtab. */
if (n->on_type & S_STB)
continue;
global = (n->on_type & S_EXT);
if ((pass == 0 && !global) ||
(pass == 1 && global)) {
emit32(cvname(n)); /* name index */
emit32(n->on_valu); /* value */
emit32(0); /* size = unknown */
emit8(cvinfo(n)); /* info */
emit8(0); /* other */
emit16(cvsect(n)); /* section */
}
}
}
}
void emit_strtab(void)
{
/* We prepend a '\0' because ELF uses offset 0 for symbols
* without a name. */
emit8('\0');
writef(stringarea, outhead.oh_nchar, 1);
}
void emit_shstrtab(void)
{
if (nstab) {
writef(shstrtab, sizeof(shstrtab), 1);
} else {
/* Skip .stab and .stabstr */
int i = sh_name[N_SYMTAB];
writef(shstrtab, sh_name[N_STAB], 1);
writef(shstrtab + i, sizeof(shstrtab) - i, 1);
}
}
/* Writes out an ELF section header. */
void emit_sh(int i)
{
uint32_t name, type, flags, addr, offset, size, link, info,
addralign, entsize;
/* If no debugger symbols, skip .stab and .stabstr */
if (nstab == 0 && (i == N_STAB || i == N_STABSTR))
return;
name = sh_name[i];
if (nstab == 0 && i >= N_STAB)
name -= (sh_name[N_SYMTAB] - sh_name[N_STAB]);
switch (i) {
case N_TEXT:
case N_RODATA:
case N_DATA:
case N_STAB:
type = 1; /* SHT_PROGBITS */
break;
case N_BSS:
type = 8; /* SHT_NOBITS */
break;
case N_SYMTAB:
type = 2; /* SHT_SYMTAB */
break;
case N_STABSTR:
case N_STRTAB:
case N_SHSTRTAB:
type = 3; /* SHT_STRTAB */
break;
default:
type = 0; /* SHT_NULL */
break;
}
switch (i) {
case N_TEXT:
flags = 4|2; /* SHF_EXECINSTR|SHF_ALLOC */
addr = outsect[TEXT].os_base;
offset = code_offset;
size = outsect[TEXT].os_size;
addralign = outsect[TEXT].os_lign;
break;
case N_RODATA:
flags = 2; /* SHF_ALLOC */
addr = outsect[ROM].os_base;
offset = code_offset + outsect[TEXT].os_size;
size = outsect[ROM].os_size;
addralign = outsect[ROM].os_lign;
break;
case N_DATA:
flags = 2|1; /* SHF_ALLOC|SHF_WRITE */
addr = outsect[DATA].os_base;
offset = code_offset + outsect[TEXT].os_size +
outsect[ROM].os_size;
size = outsect[DATA].os_size;
addralign = outsect[DATA].os_lign;
break;
case N_BSS:
flags = 2|1; /* SHF_ALLOC|SHF_WRITE */
addr = outsect[BSS].os_base;
offset = code_offset + outsect[TEXT].os_size +
outsect[ROM].os_size + outsect[DATA].os_size;
size = outsect[BSS].os_size;
addralign = outsect[BSS].os_lign;
break;
default:
flags = addr = offset = size = addralign = 0;
break;
}
entsize = 0;
switch (i) {
case N_STAB:
offset = stab_offset;
size = STAB_SYMBOL_SIZE * nstab;
entsize = STAB_SYMBOL_SIZE;
break;
case N_SYMTAB:
offset = symtab_offset;
size = ELF_SYMBOL_SIZE * nsym;
entsize = ELF_SYMBOL_SIZE;
break;
case N_STABSTR:
case N_STRTAB:
/* .stabstr, .strtab share the string area */
offset = strtab_offset;
/* the + 1 because we prepend a '\0' */
size = 1 + outhead.oh_nchar;
break;
case N_SHSTRTAB:
offset = shstrtab_offset;
size = shstrtab_size;
break;
}
/* Link .stab to .stabstr and .symtab to .strtab */
switch (i) {
case N_STAB:
link = N_STABSTR;
break;
case N_SYMTAB:
link = N_STRTAB;
if (nstab == 0)
link -= 2;
break;
default:
link = 0;
break;
}
switch (i) {
case N_SYMTAB:
info = nlocal;
break;
default:
info = 0;
break;
}
emit32(name);
emit32(type);
emit32(flags);
emit32(addr);
emit32(offset);
emit32(size);
emit32(link);
emit32(info);
emit32(addralign);
emit32(entsize);
}
/* Macros from modules/src/object/obj.h */
#define Xchar(ch) ((ch) & 0377)
#define uget2(c) (Xchar((c)[0]) | ((unsigned) Xchar((c)[1]) << 8))
#define get4(c) (uget2(c) | ((long) uget2((c)+2) << 16))
/* Read the ack.out file header. */
int rhead(FILE* f, struct outhead* head)
{
char buf[SZ_HEAD], *c;
if (fread(buf, sizeof(buf), 1, f) != 1)
return 0;
c = buf;
head->oh_magic = uget2(c); c += 2;
head->oh_stamp = uget2(c); c += 2;
head->oh_flags = uget2(c); c += 2;
head->oh_nsect = uget2(c); c += 2;
head->oh_nrelo = uget2(c); c += 2;
head->oh_nname = uget2(c); c += 2;
head->oh_nemit = get4(c); c += 4;
head->oh_nchar = get4(c);
return 1;
}
/* Read an ack.out section header. */
int rsect(FILE* f, struct outsect* sect)
{
char buf[SZ_SECT], *c;
if (fread(buf, sizeof(buf), 1, f) != 1)
return 0;
c = buf;
sect->os_base = get4(c); c += 4;
sect->os_size = get4(c); c += 4;
sect->os_foff = get4(c); c += 4;
sect->os_flen = get4(c); c += 4;
sect->os_lign = get4(c);
return 1 ;
}
/*
* Read the ack.out symbol table and string area. Count symbols.
* Seek back to the current file position.
*/
int rnames(FILE* f)
{
long told;
int i;
/* If no symbols, then do nothing successfully. */
if (outhead.oh_nname == 0)
return 1;
/* Seek to the symbol table. */
told = ftell(f);
if (told == -1)
return 0;
ack_off_char = OFF_CHAR(outhead); /* for cvname() */
if (fseek(f, OFF_NAME(outhead), SEEK_SET))
return 0;
/* Using calloc(a, b) to check if a * b would overflow. */
outname = calloc(outhead.oh_nname, sizeof(outname[0]));
if (outname == NULL)
fatal("out of memory.");
for (i = 0; i < outhead.oh_nname; i++) {
char buf[SZ_NAME], *c;
if (fread(buf, SZ_NAME, 1, f) != 1)
return 0;
c = buf;
outname[i].on_foff = get4(c); c += 4;
outname[i].on_type = uget2(c); c += 2;
outname[i].on_desc = uget2(c); c += 2;
outname[i].on_valu = get4(c);
if (outname[i].on_type & S_STB) {
nstab++;
} else {
nsym++;
if (!(outname[i].on_type & S_EXT))
nlocal++;
}
}
stringarea = malloc(outhead.oh_nchar);
if (stringarea == NULL)
fatal("out of memory.");
if (fread(stringarea, outhead.oh_nchar, 1, f) != 1)
return 0;
if (fseek(f, told, SEEK_SET))
return 0;
return 1;
}
int main(int argc, char* argv[])
{
/* General housecleaning and setup. */
input = stdin;
output = stdout;
program = argv[0];
/* Read in and process any flags. */
while ((argc > 1) && (argv[1][0] == '-'))
{
switch (argv[1][1])
{
case 'a':
elfabi = strtoul(&argv[1][2], NULL, 0);
break;
case 'b':
bigendian = 1;
break;
case 'h':
fprintf(stderr, "%s: Syntax: aelflod [-a<number>] [-b] [-h] [-l]\n\t[-m<number>] [-v] <inputfile> <outputfile>\n",
program);
exit(0);
case 'l':
bigendian = 0;
break;
case 'm':
elfmachine = strtoul(&argv[1][2], NULL, 0);
break;
case 'f':
elfflags = strtoul(&argv[1][2], NULL, 0);
break;
case 'v':
verbose = true;
break;
default:
syntaxerror:
fatal("syntax error --- try -h for help");
}
argv++;
argc--;
}
/* Process the rest of the arguments. */
switch (argc)
{
case 1: /* No parameters --- read from stdin, write to stdout. */
break;
case 3: /* Both input and output files specified. */
output = fopen(argv[2], "w");
if (!output)
fatal("unable to open output file.");
outputfile = argv[2];
/* fall through */
case 2: /* Input file specified. */
input = fopen(argv[1], "r");
if (!input)
fatal("unable to open input file.");
break;
default:
goto syntaxerror;
}
/* Read and check the ack.out file header. */
if (!rhead(input,&outhead))
fatal("failed to read file header.");
if (BADMAGIC(outhead))
fatal("this isn't an ack object file.");
if (outhead.oh_nrelo > 0)
fprintf(stderr, "Warning: relocation information present.");
if (!((outhead.oh_nsect == NUM_SEGMENTS) ||
(outhead.oh_nsect == (NUM_SEGMENTS+1))))
fatal("the input file must have %d sections, not %ld.",
NUM_SEGMENTS, outhead.oh_nsect);
/* Read in the section headers. */
{
int i;
for (i=0; i<outhead.oh_nsect; i++)
{
if (!rsect(input, &outsect[i]))
fatal("failed to read section header %d.", i);
}
}
/* Read the symbol table, then seek back to the section data. */
if (!rnames(input))
fatal("failed to read symbol table.");
/* A few checks */
if (outsect[BSS].os_flen != 0)
fatal("the bss space contains initialized data.");
if (!follows(&outsect[BSS], &outsect[DATA]))
fatal("the bss segment must follow the data segment.");
if (!follows(& outsect[ROM], &outsect[TEXT]))
fatal("the rom segment must follow the text segment.");
if (!follows(&outsect[DATA], &outsect[ROM]))
fatal("the data segment must follow the rom segment.") ;
/* Check for an optional end segment (which is otherwise
* ignored). */
if (outhead.oh_nsect == (NUM_SEGMENTS+1))
{
if (!follows(&outsect[NUM_SEGMENTS], &outsect[BSS]))
fatal("end segment must follow bss");
if ( outsect[NUM_SEGMENTS].os_size != 0 )
fatal("end segment must be empty");
}
/* Ensure the base address doesn't overlap the file header. */
code_offset = outsect[TEXT].os_base & 0x1FFF;
if (code_offset < (ELF_HEADER_SIZE + PROGRAM_HEADER_SIZE*PROGRAM_HEADER_COUNT))
fatal("base address too small --- overlaps ELF header");
/* Rationalise the memory sizes. */
outsect[TEXT].os_size = outsect[ROM ].os_base - outsect[TEXT].os_base;
outsect[ROM ].os_size = outsect[DATA].os_base - outsect[ROM ].os_base;
outsect[DATA].os_size = outsect[BSS ].os_base - outsect[DATA].os_base;
outsect[BSS ].os_size = align(outsect[BSS].os_size, outsect[BSS].os_lign);
stab_offset = code_offset + outsect[TEXT].os_size +
outsect[ROM].os_size + outsect[DATA].os_size;
/* If we have symbols, then calculate some offsets. */
if (outhead.oh_nname) {
sh_count = NUM_ELF_SECTIONS;
shstrtab_nr = N_SHSTRTAB;
shstrtab_size = sizeof(shstrtab);
if (nstab == 0) {
/* Skip .stab and .stabstr */
sh_count -= 2;
shstrtab_nr -= 2;
shstrtab_size -=
(sh_name[N_SYMTAB] - sh_name[N_STAB]);
}
symtab_offset = stab_offset + STAB_SYMBOL_SIZE * nstab;
strtab_offset = symtab_offset + ELF_SYMBOL_SIZE * nsym;
/* the + 1 because we prepend a '\0' */
shstrtab_offset = strtab_offset + 1 + outhead.oh_nchar;
sh_offset = shstrtab_offset + shstrtab_size;
}
/* Write out the ELF file header. */
writef(elf_le_ident_string, 4, 1);
emit8(1); /* class = ELFCLASS32 */
emit8(bigendian ? 2 : 1); /* endianness */
emit8(1); /* ELF version */
emit8(elfabi); /* ABI */
emit8(0); /* ABI version */
emit8(0); emit16(0); /* padding... */
emit32(0); /* ...to offset 0x10 */
emit16(2); /* type = ET_EXEC */
emit16(elfmachine); /* machine */
emit32(1); /* ELF version again */
emit32(outsect[TEXT].os_base); /* entry point */
emit32(ELF_HEADER_SIZE); /* program header offset */
emit32(sh_offset); /* section header offset */
emit32(elfflags); /* flags */
emit16(ELF_HEADER_SIZE); /* elf header size */
emit16(PROGRAM_HEADER_SIZE); /* program header entry size */
emit16(1); /* number of program header entries */
emit16(SECTION_HEADER_SIZE); /* section header entry size */
emit16(sh_count); /* number of section header entries */
emit16(shstrtab_nr); /* section header string table index */
/* Write out a single rwx section for the entire program. */
{
uint32_t filelength = stab_offset;
uint32_t memlength = filelength + outsect[BSS].os_size;
emitphdr(outsect[TEXT].os_base & ~0x1FFF,
filelength, memlength, 0, 4|2|1);
}
/* Write padding until the code start. */
if (fseek(output, code_offset, SEEK_SET))
fatal("output seek error");
/* Write out the actual data. */
emits(&outsect[TEXT]);
emits(&outsect[ROM]);
emits(&outsect[DATA]);
/* Write out the symbol table and section headers. */
if (outhead.oh_nname) {
int i;
if (nstab)
emit_stab();
emit_symtab();
emit_strtab();
emit_shstrtab();
for (i = 0; i < NUM_ELF_SECTIONS; i++)
emit_sh(i);
}
if (ferror(output))
fatal("output write error");
if (outputfile)
{
/* mode = 0755 in standard UNIX */
chmod(outputfile, S_IRWXU | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH);
}
/* Summarise what we've done. */
if (verbose)
{
uint32_t ss = 0;
printf(" address length\n");
printf(" ehdr : %08"PRIx32" %08"PRIx32"\n", outsect[TEXT].os_base & ~0x1FFF, code_offset);
printf(" text : %08"PRIx32" %08"PRIx32"\n", outsect[TEXT].os_base, outsect[TEXT].os_size);
printf(" rom : %08"PRIx32" %08"PRIx32"\n", outsect[ROM].os_base, outsect[ROM].os_size);
printf(" data : %08"PRIx32" %08"PRIx32"\n", outsect[DATA].os_base, outsect[DATA].os_size);
printf(" bss : %08"PRIx32" %08"PRIx32"\n", outsect[BSS].os_base, outsect[BSS].os_size);
ss += outsect[TEXT].os_size;
ss += outsect[ROM].os_size;
ss += outsect[DATA].os_size;
ss += outsect[BSS].os_size;
printf("TOTAL : %08"PRIx32"\n", ss);
}
return 0;
}