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disassemble hello world program

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This commit is contained in:
Antoni Piasecki
2026-02-28 17:34:56 +01:00
parent 1cbf764e8b
commit f8d128c85d
1 changed files with 51 additions and 10 deletions
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61
riscv64.c
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@@ -8,11 +8,26 @@
#include <stdlib.h>
#include <string.h>
#define PARSE_I_INS(ins) \
uint8_t rd = (ins >> 7) & 0b11111; \
uint8_t funct3 = (ins >> 12) & 0b111; \
uint8_t rs1 = (ins >> 15) & 0b11111; \
uint16_t imm = ins >> 20
#define PARSE_U_INS(ins) \
uint8_t rd = (ins >> 7) & 0b11111; \
uint32_t imm = ins >> 12
typedef struct {
size_t offset;
size_t size;
} Section;
const char *REGS[32] = {"zero", "ra", "sp", "gp", "tp", "t0", "t1", "t2",
"fp", "s1", "a0", "a1", "a2", "a3", "a4", "a5",
"a6", "a7", "s2", "s3", "s4", "s5", "s6", "s7",
"s8", "s9", "s10", "s11", "t3", "t4", "t5", "t6"};
Section get_code_section(uint8_t *exe_bytes, size_t exe_size) {
Elf *elf = elf_memory((char *)exe_bytes, exe_size);
if (!elf) {
@@ -50,25 +65,50 @@ void riscv64_disassemble(uint8_t *exe_bytes, Section section) {
uint32_t ins;
memcpy(&ins, exe_bytes + offset, 4);
uint16_t opcode = ins & 0x7f; // last 7 bits
uint16_t opcode = ins & 0b1111111;
// https://stackoverflow.com/questions/62939410/how-can-i-find-out-the-instruction-format-of-a-risc-v-instruction
switch (opcode) {
case 0b1100011:
printf("B-type\n");
break;
case 0b0010011:
printf("I-type 1\n");
break;
case 0b0010011: {
PARSE_I_INS(ins);
switch (funct3) {
case 0b000:
printf("addi %s, %s, %d\n", REGS[rd], REGS[rs1], imm);
break;
default:
fprintf(stderr, "I-type 1: unrecognized funct3: %03b\n", funct3);
exit(1);
}
}; break;
case 0b0000011:
printf("I-type 2\n");
break;
case 0b1100111:
printf("I-type 3\n");
break;
case 0b1110011:
printf("I-type 4\n");
break;
case 0b1110011: {
PARSE_I_INS(ins);
switch (funct3) {
case 0b000:
switch (imm) {
case 0:
printf("ecall\n");
break;
default:
fprintf(stderr, "I-type 4: funct3=000 unrecognized imm: %b\n", imm);
exit(1);
};
break;
default:
fprintf(stderr, "I-type 4: unrecognized funct3: %03b\n", funct3);
exit(1);
}
}; break;
case 0b1101111:
printf("J-type\n");
break;
@@ -87,9 +127,10 @@ void riscv64_disassemble(uint8_t *exe_bytes, Section section) {
case 0b0110111:
printf("U-type 1\n");
break;
case 0b0010111:
printf("U-type 2\n");
break;
case 0b0010111: {
PARSE_U_INS(ins);
printf("auipc %s, %d\n", REGS[rd], imm);
}; break;
default:
fprintf(stderr, "Unrecognized opcode: %07b\n", opcode);
exit(1);