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ack/util/amisc/aelflod.c
George Koehler 5cf2a68438 Teach aelflod to write the ELF symbol table. 
Convert each ack.out symbol to ELF, preserving its name and value, and
some but not all other symbol info.  The ELF symbol table comes with
ELF section headers.  If the input file has no symbols (ack -Rled-s),
then the output file has no ELF section headers.

Append the symbol table and section headers to the ELF file.  Linux
ignores this appended info when it execs the file.  The info might
pollute the last page of the ELF segment, but Linux clears this
pollution.  Tools like nm and gdb can read the ELF symbol table.

I include code to translate debugger symbols to an ELF .stab section.
I did not test this code, because I did not find a platform that can
put S_STB symbols in the ack.out file.
2016-12-13 16:41:22 -05:00

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/*
* 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 "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 */
/* 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 */
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;
for (i = 0; i < outhead.oh_nname; i++) {
n = &outname[i];
if (!(n->on_type & S_STB)) {
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, addralign,
link, 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:
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;
}
emit32(name);
emit32(type);
emit32(flags);
emit32(addr);
emit32(offset);
emit32(size);
emit32(link);
emit32(0); /* 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++;
}
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 = atoi(&argv[1][2]);
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 = atoi(&argv[1][2]);
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(0); /* 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)
chmod(outputfile, 0755);
/* 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;
}
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