From 5a22735d1c265a0a000c77ec9b5bd74688a87370 Mon Sep 17 00:00:00 2001
From: David Phillips <david@sighup.nz>
Date: Mon, 29 Jul 2019 21:18:09 +1200
Subject: Implement quick disassembler
---
disassembler.c | 174 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 174 insertions(+)
create mode 100644 disassembler.c
(limited to 'disassembler.c')
diff --git a/disassembler.c b/disassembler.c
new file mode 100644
index 0000000..24bbc50
--- /dev/null
+++ b/disassembler.c
@@ -0,0 +1,174 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <errno.h>
+
+#include "util.h"
+
+void print_help(const char *argv0)
+{
+ fprintf(stderr, "Syntax: %s <in.bin>\0 <out.asm>\n", argv0);
+}
+
+int disasm_rtype(uint16_t i, uint16_t unused)
+{
+ const char *oper = get_asm_from_oper(GET_OPER(i));
+ const char *dest = get_asm_from_reg(GET_REG_DEST(i));
+ const char *left = get_asm_from_reg(GET_REG_LEFT(i));
+ const char *right = get_asm_from_reg(GET_REG_RIGHT(i));
+
+ /* FIXME add special cases:
+ * - nop
+ * - neg
+ * - mv
+ */
+ printf("%s %s, %s, %s\n", oper, dest, left, right);
+
+ return 0;
+}
+
+int disasm_nitype(uint16_t i, uint16_t unused)
+{
+ const char *oper = get_asm_from_oper(GET_OPER(i));
+ const char *dest = get_asm_from_reg(GET_REG_DEST(i));
+ const char *left = get_asm_from_reg(GET_REG_LEFT(i));
+ uint16_t imm = GET_NI_IMM(i);
+ /** FIXME add special cases:
+ * - ldi
+ */
+ /* FIXME review sign around immediate value */
+ printf("%si %s, %s, 0x%x\n", oper, dest, left, imm);
+ return 0;
+}
+
+int disasm_witype(uint16_t i, uint16_t unused)
+{
+ const char *oper = get_asm_from_oper(GET_OPER(i));
+ const char *dest = get_asm_from_reg(GET_REG_DEST(i));
+ const char *left = get_asm_from_reg(GET_REG_LEFT(i));
+ uint16_t imm = GET_NI_IMM(i);
+ /* FIXME handle wide imm value */
+ printf("%si, %s, %s, 0x%x\n", "oper", dest, left, "?");
+ return 0;
+}
+
+int disasm_jreg(uint16_t i, uint16_t unused)
+{
+ const char *inst = get_asm_from_j(GET_JB_COND(i));
+ const char *reg = get_asm_from_reg(GET_JUMP_REG(i));
+ printf("%s %s\n", inst, reg);
+ return 0;
+}
+
+int disasm_bimm(uint16_t i, uint16_t unused)
+{
+ const char *inst = get_asm_from_b(GET_JB_COND(i));
+ /* FIXME immediate value is meant to be signed */
+ printf("%s 0x%x\n", inst, GET_B_OFFSET(i));
+ return 0;
+}
+
+int disasm_jimm(uint16_t i, uint16_t imm)
+{
+ const char *inst = get_asm_from_j(GET_JB_COND(i));
+ printf("%s 0x%x\n", inst, imm);
+ return 0;
+}
+
+int disasm(FILE *f)
+{
+ int ret = 0;
+ size_t offs = 0;
+ size_t extra_read = 0;
+ uint16_t inst = 0;
+ uint8_t c[2] = { 0 };
+ int (*disasm_inst)(uint16_t, uint16_t);
+
+ while (!feof(f) && fread(c, sizeof(c), 1, f) == 1) {
+ extra_read = 0;
+ inst = c[0] << 8 | c[1];
+ switch (GET_INST_TYPE(inst)) {
+ case INST_TYPE_RTYPE:
+ disasm_inst = disasm_rtype;
+ break;
+ case INST_TYPE_NITYPE:
+ disasm_inst = disasm_nitype;
+ break;
+ case INST_TYPE_WITYPE:
+ if (fread(c, sizeof(c), 1, f) != 1) {
+ ret = -errno;
+ break;
+ }
+ extra_read = sizeof(c);
+ disasm_inst = disasm_witype;
+ break;
+ case INST_TYPE_JTYPE:
+ /* J Type can be split into three further subtypes:
+ * - branch (always immediate, 2 bytes)
+ * - jump reg (2 bytes)
+ * - jump immediate (4 bytes)
+ */
+ if (inst & MASK_IS_BRANCH) {
+ disasm_inst = disasm_bimm;
+ } else {
+ if (inst & MASK_JR) {
+ disasm_inst = disasm_jreg;
+ } else {
+ if (fread(c, sizeof(c), 1, f) != 1) {
+ ret = -errno;
+ break;
+ }
+ extra_read = sizeof(c);
+ disasm_inst = disasm_jimm;
+ }
+ }
+ break;
+ default:
+ printf("Unhandled instruction at byte %zd\n", offs);
+ ret = -1;
+ break;
+ }
+ /* Fall out of loop if picking a handler errored */
+ if (ret) {
+ break;
+ }
+ printf("%04x:\t", offs);
+ ret = disasm_inst(inst, c[0] << 8 | c[1]);
+ if (ret < 0) {
+ fprintf(stderr, "Error handling instruction at byte %zd\n", offs);
+ break;
+ }
+ offs += sizeof(c) + extra_read;
+ }
+
+ if (!feof(f)) {
+ perror("fread");
+ ret = errno;
+ } else {
+ /* print out final, empty label */
+ printf("%04x:\n", offs);
+ }
+
+ return ret;
+}
+
+int main(int argc, char **argv)
+{
+ int ret = 0;
+ FILE *fin = NULL;
+
+ if (argc < 2) {
+ print_help(argv[0]);
+ return 1;
+ }
+
+ if (!(fin = fopen(argv[1], "rb"))) {
+ perror("fopen");
+ return 1;
+ }
+
+ ret = disasm(fin);
+
+ fclose(fin);
+ return ret;
+}
--
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