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#include <assert.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "mnemonics.h"
const char *progname;
#define ERROR(...) \
do { \
fprintf(stderr, "%s: ", progname); \
fprintf(stderr, __VA_ARGS__); \
fprintf(stderr, "\n"); \
} while (0)
#define PERROR(str) \
do { \
int err = errno; \
fprintf(stderr, "%s: ", progname); \
errno = err; \
perror(str); \
} while (0)
static struct line {
int label;
uint16_t value;
uint8_t mnem;
} lines[0x7fff];
static size_t maxpc;
#define LINE(addr) &lines[(uint16_t)(addr) >> 1]
#define MNEM(line) ((line)->mnem < MNEM_LAST ? &mnemonics[(line)->mnem] : NULL)
static const uint8_t match_instruction(unsigned bits)
{
for (int i = 0; i < MNEM_LAST; i++) {
const struct mnemonic *m = mnemonics + i;
if ((bits & m->mask) == m->bits) return i;
}
return MNEM_LAST;
}
static inline int get_argvalue(const struct line *line, int argidx)
{
const struct operand *op = MNEM(line)->operands + argidx;
switch (op->type) {
case REG:
case REGPTR: return 7 & (line->value >> op->shift);
case IMM: return (uint8_t) (line->value >> op->shift);
case PCOFF: return (int8_t) (line->value >> op->shift);
}
assert(0);
}
static struct line *get_pcoff_target(uint16_t pc, int argidx)
{
struct line *l = LINE(pc + get_argvalue(LINE(pc), argidx));
return l - lines >= 2*maxpc ? NULL : l;
}
static void assign_labels(void)
{
/* mark those addresses that need a label */
for (size_t pc = 0; pc < maxpc; pc += 2) {
const struct line *l = LINE(pc);
const struct mnemonic *m = MNEM(l);
if (!m) continue;
const struct operand *ops = m->operands;
for (int j = 0; j < 3 && ops[j].type; j++) {
if (ops[j].type == PCOFF) {
struct line *target = get_pcoff_target(pc, j);
if (target) target->label = 1;
}
}
}
/* assign labels in ascending order */
int label = 0;
for (size_t pc = 0; pc < maxpc; pc += 2) {
struct line *l = LINE(pc);
l->label = l->label ? label++ : -1;
}
}
static void print_operand(FILE *out, size_t pc, size_t argidx)
{
const struct line *inst = LINE(pc);
const struct operand *op = MNEM(inst)->operands + argidx;
switch (op->type) {
case REG: fprintf(out, "r%d", get_argvalue(inst, argidx)); break;
case REGPTR: fprintf(out, "@r%d", get_argvalue(inst, argidx)); break;
case IMM: fprintf(out, "%d", get_argvalue(inst, argidx)); break;
case PCOFF: {
const struct line *target = get_pcoff_target(pc, argidx);
if (target && target->label >= 0)
fprintf(out, "L%d", target->label);
else
fprintf(out, "%d", get_argvalue(inst, argidx));
break;
}
default: assert(0);
}
}
static int read_lines(FILE *in)
{
unsigned bits;
for (maxpc = 0; fscanf(in, " %x\n", &bits) > 0; maxpc += 2) {
if (maxpc > 0xffff) {
ERROR("Input exceeds 16-bit address space");
return 1;
}
*LINE(maxpc) = (struct line) {
.mnem = match_instruction(bits),
.value = bits,
};
}
return 0;
}
static void disassemble(FILE *in, FILE *out)
{
if (read_lines(in)) return;
assign_labels();
for (size_t pc = 0; pc < maxpc; pc += 2) {
const struct line *line = LINE(pc);
unsigned bits = line->value;
const struct mnemonic *m = MNEM(line);
if (line->label >= 0) fprintf(out, "L%d:", line->label);
if (!m) {
fprintf(out, "\t.word 0x%04x\n", bits);
continue;
}
fprintf(out, "\t%s", m->mnem);
for (int j = 0; j < 3 && m->operands[j].type; j++) {
if (j) fprintf(out, ", ");
else fprintf(out, "%*s", 8 - (int)strlen(m->mnem), "");
print_operand(out, pc, j);
}
fprintf(out, "\n");
}
}
static void usage(const char *progname)
{
printf("usage: %s [-o output] [input]\n", progname);
printf(" %s -h\n", progname);
printf("\n");
printf("\t%-16s %s\n", "-h", "display this help text and exit");
printf("\t%-16s %s\n", "-o output", "write output to 'output' (default=stdout)");
printf("\t%-16s %s\n", "input", "read input from 'input' (default=stdin)");
}
int main(int argc, char **argv)
{
const char *outname = NULL;
int error = 0;
extern int optind;
extern char *optarg;
progname = argv[0];
for (int opt; (opt = getopt(argc, argv, "+ho:")) != -1;) {
switch (opt) {
case 'h':
usage(argv[0]);
return 0;
case 'o':
outname = optarg;
break;
default:
error = 1;
}
}
if (optind < argc - 1) {
ERROR("Too many input files");
return 1;
}
if (error) return 1;
FILE *in = stdin;
FILE *out = stdout;
if (optind < argc && !(in = fopen(argv[optind], "r"))) {
PERROR("Error opening input file");
return 1;
}
if (outname && !(out = fopen(outname, "w"))) {
PERROR("Error opening output file");
fclose(in);
return 1;
}
disassemble(in, out);
fclose(in);
fclose(out);
return 0;
}
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