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syms.c
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syms.c
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/*
* ELKS symbol table support
*
* July 2022 Greg Haerr
*/
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/stat.h>
#include <stdint.h>
#include "syms.h"
#if __ia16__
#define ALLOC(s,n) ((int)(s = sbrk(n)) != -1)
#else
#define ALLOC(s,n) ((s = malloc(n)) != NULL)
#endif
#define MAGIC 0x0301 /* magic number for ELKS executable progs */
/* read symbol table from executable into memory */
unsigned char * noinstrument sym_read_exe_symbols(struct exe *e, char *path)
{
int fd;
unsigned char *s;
if (e->syms) return e->syms;
if ((fd = open(path, O_RDONLY)) < 0) {
#if __ia16__
char fullpath[128];
sprintf(fullpath, "/bin/%s", path); // FIXME use PATH
if ((fd = open(fullpath, O_RDONLY)) < 0)
#endif
return NULL;
}
errno = 0;
if (read(fd, &e->aout, sizeof(e->aout)) != sizeof(e->aout)
|| ((e->aout.type & 0xFFFF) != MAGIC)
|| e->aout.syms == 0
#if __ia16__
|| e->aout.syms > 32767
#endif
|| (!ALLOC(s, (int)e->aout.syms))
|| (lseek(fd, -(int)e->aout.syms, SEEK_END) < 0)
|| (read(fd, s, (int)e->aout.syms) != (int)e->aout.syms)) {
int e = errno;
close(fd);
errno = e;
return NULL;
}
close(fd);
e->syms = s;
return s;
}
/* read symbol table file into memory */
unsigned char * noinstrument sym_read_symbols(struct exe *e, char *path)
{
int fd;
unsigned char *s;
struct stat sbuf;
if (e->syms) return e->syms;
if ((fd = open(path, O_RDONLY)) < 0)
return NULL;
errno = 0;
if (fstat(fd, &sbuf) < 0
|| sbuf.st_size == 0
#if __ia16__
|| sbuf.st_size > 32767
#endif
|| (!ALLOC(s, (int)sbuf.st_size))
|| (read(fd, s, (int)sbuf.st_size) != (int)sbuf.st_size)) {
int e = errno;
close(fd);
errno = e;
return NULL;
}
close(fd);
e->syms = s;
return s;
}
/* dealloate symbol table file in memory */
void noinstrument sym_free(struct exe *e)
{
#ifndef __ia16__ // FIXME ELKS uses sbrk()
if (e->syms)
free(e->syms);
#endif
e->syms = NULL;
}
static int noinstrument type_text(unsigned char *p)
{
return (p[TYPE] == 'T' || p[TYPE] == 't' || p[TYPE] == 'W');
}
static int noinstrument type_ftext(unsigned char *p)
{
return (p[TYPE] == 'F' || p[TYPE] == 'f');
}
static int noinstrument type_data(unsigned char *p)
{
return (p[TYPE] == 'D' || p[TYPE] == 'd' ||
p[TYPE] == 'B' || p[TYPE] == 'b' ||
p[TYPE] == 'V');
}
/* map .text address to function start address */
addr_t noinstrument sym_fn_start_address(struct exe *e, addr_t addr)
{
unsigned char *p, *lastp;
if (!e->syms) return -1;
lastp = e->syms;
for (p = next(lastp); ; lastp = p, p = next(p)) {
if (!type_text(p) || ((unsigned short)addr < *(unsigned short *)(&p[ADDR])))
break;
}
return *(unsigned short *)(&lastp[ADDR]);
}
/* convert address to symbol string */
static char * noinstrument sym_string(struct exe *e, addr_t addr, int exact,
int (*istype)(unsigned char *p))
{
unsigned char *p, *lastp;
static char buf[64];
if (!e->syms) {
hex:
sprintf(buf, "%.4x", (unsigned int)addr);
return buf;
}
lastp = e->syms;
while (!istype(lastp)) {
lastp = next(lastp);
if (!lastp[TYPE])
goto hex;
}
for (p = next(lastp); ; lastp = p, p = next(p)) {
if (!istype(p) || ((unsigned short)addr < *(unsigned short *)(&p[ADDR])))
break;
}
int lastaddr = *(unsigned short *)(&lastp[ADDR]);
if (exact && addr - lastaddr) {
sprintf(buf, "%.*s+%xh", lastp[SYMLEN], lastp+SYMBOL,
(unsigned int)addr - lastaddr);
} else sprintf(buf, "%.*s", lastp[SYMLEN], lastp+SYMBOL);
return buf;
}
/* convert .text address to symbol */
char * noinstrument sym_text_symbol(struct exe *e, addr_t addr, int exact)
{
return sym_string(e, addr, exact, type_text);
}
/* convert .fartext address to symbol */
char * noinstrument sym_ftext_symbol(struct exe *e, addr_t addr, int exact)
{
return sym_string(e, addr, exact, type_ftext);
}
/* convert .data address to symbol */
char * noinstrument sym_data_symbol(struct exe *e, addr_t addr, int exact)
{
return sym_string(e, addr, exact, type_data);
}
#if 0
static int noinstrument type_any(unsigned char *p)
{
return p[TYPE] != '\0';
}
/* convert (non-segmented local IP) address to symbol */
char * noinstrument sym_symbol(struct exe *e, addr_t addr, int exact)
{
return sym_string(e, addr, exact, type_any);
}
#endif