rvemu

commit 4f7fe64aa5cbd2fb181c3fece01a0b806fc885a1
parent 2cc43400b091dc7d16b7d8880ba4e2d47f2702ad
Author: Michail Konstantinos Dimopoulos <mk@mcdim.xyz>
Date:   Fri,  4 Sep 2026 21:20:17 +0300

Improved debugger output and added running mode

Diffstat:
M
disasm.c
 | 
30
+++++++++++++++---------------
M
exec.c
 | 
17
++---------------
M
main.c
 | 
111
++++++++++++++++++++++++++++++++++++++++++++++++++-----------------------------
A
mem.h
 | 
15
+++++++++++++++

4 files changed, 102 insertions(+), 71 deletions(-)
diff --git a/disasm.c b/disasm.c
@@ -19,7 +19,7 @@ static void disasm_itype(uint32_t inst) {
 		if (i.funct7 == 0x00) {
 			printf("slli");
 		} else {
-			printf("Illegal funct7\n");
+			printf(".word 0x%08" PRIx32 "\n", inst);
 			return;
 		}
 		break;
@@ -41,7 +41,7 @@ static void disasm_itype(uint32_t inst) {
 			printf("srai");
 			break;
 		default:
-			printf("Illegal funct7\n");
+			printf(".word 0x%08" PRIx32 "\n", inst);
 			return;
 		}
 		break;
@@ -52,10 +52,10 @@ static void disasm_itype(uint32_t inst) {
 		printf("andi");
 		break;
 	default:
-		printf("Illegal funct3\n");
+		printf(".word 0x%08" PRIx32 "\n", inst);
 		return;
 	}
-	printf(" x%d, %" PRIu8 ", %" PRId32 "\n", i.rd, i.rs1, i.imm);
+	printf(" x%d, x%" PRIu8 ", %" PRId32 "\n", i.rd, i.rs1, i.imm);
 }
 
 static void disasm_rtype(uint32_t inst) {
@@ -72,7 +72,7 @@ static void disasm_rtype(uint32_t inst) {
 			printf("sub x%d, x%d\n", r.rs1, r.rs2);
 			break;
 		default:
-			printf("Illegal funct7\n");
+			printf(".word 0x%08" PRIx32 "\n", inst);
 			return;
 		}
 		break;
@@ -97,7 +97,7 @@ static void disasm_rtype(uint32_t inst) {
 			printf("sra x%d, x%d\n", r.rs1, r.rs2);
 			break;
 		default:
-			printf("Illegal funct7\n");
+			printf(".word 0x%08" PRIx32 "\n", inst);
 			return;
 		}
 		break;
@@ -108,7 +108,7 @@ static void disasm_rtype(uint32_t inst) {
 		printf("and x%d, x%d\n", r.rs1, r.rs2);
 		break;
 	default:
-		printf("Illegal funct3\n");
+		printf(".word 0x%08" PRIx32 "\n", inst);
 		return;
 	}
 }
@@ -134,7 +134,7 @@ static void disasm_itype_loads(uint32_t inst) {
 		printf("lhu");
 		break;
 	default:
-		printf("Illegal funct3\n");
+		printf(".word 0x%08" PRIx32 "\n", inst);
 		return;
 	}
 
@@ -157,7 +157,7 @@ static void disasm_stype(uint32_t inst) {
 		printf("sw");
 		break;
 	default:
-		printf("Illegal funct3\n");
+		printf(".word 0x%08" PRIx32 "\n", inst);
 		return;
 	}
 
@@ -189,7 +189,7 @@ static void disasm_btype(uint32_t inst) {
 		printf("bgeu");
 		break;
 	default:
-		printf("Illegal funct3\n");
+		printf(".word 0x%08" PRIx32 "\n", inst);
 		return;
 	}
 
@@ -204,7 +204,7 @@ static void disasm_itype_jalr(uint32_t inst) {
 	decode_itype(&i, inst);
 	
 	if (i.funct3 != 0x0u) {
-		fprintf(stderr, "Illegal JALR funct3\n");
+		printf(".word 0x%08" PRIx32 "\n", inst);
 		return;
 	}
 	
@@ -243,7 +243,7 @@ disasm_itype_control(uint32_t inst)
 	decode_itype(&i, inst);
 
 	if (i.funct3 != 0x0) {
-		puts("Illegal instruction");
+		printf(".word 0x%08" PRIx32 "\n", inst);
 		return;
 	}
 
@@ -254,7 +254,7 @@ disasm_itype_control(uint32_t inst)
 		puts("ebreak");
 		return;
 	} else {
-		puts("Illegal instruction");
+		printf(".word 0x%08" PRIx32 "\n", inst);
 		return;
 	}
 }
@@ -266,7 +266,7 @@ disasm_itype_fence(uint32_t inst)
 	decode_itype(&i, inst);
 
 	if (i.funct3 != 0x0) {
-		puts("Illegal instruction");
+		printf(".word 0x%08" PRIx32 "\n", inst);
 		return;
 	}
 
@@ -299,7 +299,7 @@ void disassemble_instruction(uint32_t inst) {
 	uint16_t opcode = inst & 0x7f;
 	disasm_fn fn = opcode_table[opcode];
 	if (!fn) {
-		fprintf(stderr, "Illegal opcode\n");
+		printf(".word 0x%08" PRIx32 "\n", inst);
 		return;
 	}
 	fn(inst);
diff --git a/exec.c b/exec.c
@@ -5,11 +5,11 @@
 #include <string.h>
 
 #include "exec.h"
+#include "mem.h"
 #include "decode.h"
 #include "disasm.h"
 #include "trap.h"
 
-
 static inline void print_bin16(uint16_t x) {
 	for (int i = 15; i >= 0; i--) {
 		putchar((x >> i) & 1 ? '1' : '0');
@@ -463,18 +463,6 @@ exec_itype_fence(cpu_state_t *cpu, uint32_t inst, uint8_t *mem)
 	cpu->pc += 4;
 }
 
-static inline uint32_t
-make_instruction(uint8_t *mem, uint32_t index)
-{
-	uint32_t inst = 0;
-	inst |= (uint32_t)(mem[index+0]) << 0;
-	inst |= (uint32_t)(mem[index+1]) << 8;
-	inst |= (uint32_t)(mem[index+2]) << 16;
-	inst |= (uint32_t)(mem[index+3]) << 24;
-	return inst;
-
-}
-
 /* Function pointer dispatch */
 typedef void (*exec_fn)(cpu_state_t *, uint32_t inst, uint8_t *mem);
 
@@ -496,8 +484,7 @@ static exec_fn opcode_table[128] = {
 void
 cpu_step(cpu_state_t *cpu, uint8_t *mem)
 {
-	uint32_t inst = make_instruction(mem, cpu->pc);
-	disassemble_instruction(inst);
+	uint32_t inst = load_u32_le(mem, cpu->pc); /* load little endian */
 
 	/* decode opcode */
 	uint16_t opcode = inst & 127;
diff --git a/main.c b/main.c
@@ -4,8 +4,15 @@
 #include <stdlib.h>
 #include <string.h>
 
-#include "disasm.h"
+//#include "disasm.h"
 #include "exec.h"
+#include "mem.h"
+#include "disasm.h"
+
+typedef enum {
+	MODE_RUN,
+	MODE_STEP
+} emu_mode_t;
 
 static void
 load_program(uint8_t *mem)
@@ -62,14 +69,13 @@ load_program(uint8_t *mem)
 0x00058067	//jr      a1
 */
 
-/*
       0x00700513,  // addi x10, x0, 7
       0x00451513,  // slli x10, x10, 4
       0x00d50513,  // addi x10, x10, 13
       0x05554513,  // xori x10, x10, 0x55
       0xff750513,  // addi x10, x10, -9
       0x00100073   // ebreak
-*/
+/*
 0x10000593,	//li      a1,256
 0xfff00513,	//li      a0,-1
 0x00a58023,	//sb      a0,0(a1)
@@ -89,6 +95,7 @@ load_program(uint8_t *mem)
 0x0085a503,	//lw      a0,8(a1)
 0x00000593,	//li      a1,0
 0x00100073	//ebreak
+*/
 	};
 
 	size_t len = sizeof(arr) / sizeof(arr[0]);
@@ -105,15 +112,15 @@ load_program(uint8_t *mem)
 	}
 }
 
-
-void
+static emu_mode_t
 trap_handler(cpu_state_t *cpu)
 {
 	if (cpu->status == CPU_TRAPPED) {
 		printf("CPU trapped\n");
-		switch(cpu.trap.cause) {
+		switch(cpu->trap.cause) {
 		case TRAP_EBREAK:
 			printf("Code reached breakpoint\n");
+			return MODE_STEP;
 			break;
 		case TRAP_ECALL:
 			printf("Code ECALL\n");
@@ -132,8 +139,59 @@ trap_handler(cpu_state_t *cpu)
 			break;
 		}
 	}
+	return MODE_RUN;
 }
 
+static emu_mode_t
+debugger(cpu_state_t *cpu, uint8_t *mem)
+{
+	printf("PC 0x%x>", cpu->pc);
+	char line[256];
+	if (!fgets(line, sizeof(line), stdin)) {
+		fprintf(stderr, "Error reading"
+			"interactive input\n");
+	}
+
+	if (strncmp(line, "s", 1) == 0 ||
+	    strncmp(line, "step", 4) == 0  ||
+	    strncmp(line, "n", 1) == 0 ||
+	    strncmp(line, "next", 4) == 0) {
+
+		uint32_t inst = load_u32_le(mem, cpu->pc); /* load little endian */
+		disassemble_instruction(inst);
+		cpu_step(cpu, mem);
+
+		trap_handler(cpu);
+
+	} else if (strncmp(line, "r", 1) == 0 ||
+		   strncmp(line, "registers", 9) == 0) {
+		printf("Registers:\n");
+		for (int i=0; i<32; i++) {
+			printf("0x%x: 0x%x\n", i, cpu->x[i]);
+		}
+	} else if (strncmp(line, "m", 1) == 0 ||
+		   strncmp(line, "memory", 6) == 0) {
+		printf("Memory:\n");
+		for (int i=0; i<128; i+=4) {
+			if (cpu->pc == i) {
+				printf("-> ");
+			} else {
+				printf("   ");
+			}
+			printf("0x%.8x: 0x%.2x 0x%.2x 0x%.2x 0x%.2x     ",
+			       i, mem[i], mem[i+1], mem[i+2], mem[i+3]);
+			disassemble_instruction(load_u32_le(mem,i));
+		}
+	} else if (strncmp(line, "ip", 2) == 0 ||
+		   strncmp(line, "pc", 2) == 0) {
+		printf("Instruction poiter:\n");
+		printf("PC: %" PRIu32 "\n", cpu->pc);
+	} else if (strncmp(line, "e", 1) == 0) {
+		return MODE_RUN;
+	}
+
+	return MODE_STEP;
+}
 
 int
 main()
@@ -145,43 +203,14 @@ main()
 	load_program(mem);
 	
 	/* fetch & run */
-	while (1) {
-		printf("PC 0x%x>", cpu.pc);
-		char line[256];
-		if (!fgets(line, sizeof(line), stdin)) {
-			fprintf(stderr, "Error reading"
-				"interactive input\n");
-		}
-
-		if (strncmp(line, "s", 1) == 0 ||
-		    strncmp(line, "step", 4) == 0  ||
-		    strncmp(line, "n", 1) == 0 ||
-		    strncmp(line, "next", 4) == 0) {
+	emu_mode_t mode = MODE_STEP;	
 
+	while (1) {
+		if (mode == MODE_RUN) {
 			cpu_step(&cpu, mem);
-
-			trap_handler(&cpu);
-
-		} else if (strncmp(line, "r", 1) == 0 ||
-			   strncmp(line, "registers", 9) == 0) {
-			printf("Registers:\n");
-			for (int i=0; i<32; i++) {
-				printf("0x%x: 0x%x\n", i, cpu.x[i]);
-			}
-		} else if (strncmp(line, "m", 1) == 0 ||
-			   strncmp(line, "memory", 6) == 0) {
-			printf("Memory:\n");
-			for (int i=0; i<32; i++) {
-				printf("0x%x: 0x%x\n", i, mem[i]);
-			}
-			printf("\n");
-			for (int i=256; i<268; i++) {
-				printf("0x%x: 0x%x\n", i, mem[i]);
-			}
-		} else if (strncmp(line, "ip", 2) == 0 ||
-			   strncmp(line, "pc", 2) == 0) {
-			printf("Instruction poiter:\n");
-			printf("PC: %" PRIu32 "\n", cpu.pc);
+			mode = trap_handler(&cpu);
+		} else {
+			mode = debugger(&cpu, mem);
 		}
 	}
 
diff --git a/mem.h b/mem.h
@@ -0,0 +1,15 @@
+#ifndef MEMORY_H
+#define MEMORY_H
+
+static inline uint32_t
+load_u32_le(uint8_t *mem, uint32_t index)
+{
+	uint32_t inst = 0;
+	inst |= (uint32_t)(mem[index+0]) << 0;
+	inst |= (uint32_t)(mem[index+1]) << 8;
+	inst |= (uint32_t)(mem[index+2]) << 16;
+	inst |= (uint32_t)(mem[index+3]) << 24;
+	return inst;
+}
+
+#endif