rvemu

commit 51338a4f65ca4f32e7c62461d0b0c59ea670af1c
parent e2aa4903fefda539540b4dc39619291196c02159
Author: Michail Konstantinos Dimopoulos <mk@mcdim.xyz>
Date:   Wed,  2 Sep 2026 16:26:51 +0300

Added jump address and 0 reg invariance checks

Diffstat:
M
main.c
 | 
78
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-----------------

1 file changed, 61 insertions(+), 17 deletions(-)
diff --git a/main.c b/main.c
@@ -33,18 +33,39 @@ static inline void print_binless(uint32_t x, int a) {
 	}
 }
 
-static int32_t get_valid_branch_target(uint32_t pc, int32_t offset, uint32_t *target)
+static inline int is_instruction_address_valid(int64_t addr)
 {
-	int64_t candidate = (int64_t)pc + (int64_t)offset;
-	
-	if (candidate < 0)
-	    return -1;
+	if (addr < 0)
+	    return 0;
 	
-	if (candidate > (int64_t)MEMSIZE-4)
-	    return -1;
+	if (addr > (int64_t)MEMSIZE-4)
+	    return 0;
 	
-	if ((candidate & 0x3) != 0)
-	    return -1;
+	if ((addr & 0x3) != 0)
+	    return 0;
+
+	return 1;
+}
+
+static int32_t get_valid_branch_target(uint32_t pc, int32_t offset,
+				       uint32_t *target)
+{
+	int64_t candidate = (int64_t)pc + (int64_t)offset;
+	if (!is_instruction_address_valid(candidate))
+		return 1;
+
+	*target = (uint32_t)candidate;
+
+	return 0;
+}
+
+static int32_t get_valid_jalr_target(uint32_t base, int32_t offset,
+				     uint32_t *target)
+{
+	int64_t candidate = ((int64_t)base + (int64_t)offset)
+			    & ~INT64_C(1);
+	if (!is_instruction_address_valid(candidate))
+		return 1;
 	
 	*target = (uint32_t)candidate;
 	return 0;
@@ -460,16 +481,25 @@ static void exec_itype_jalr(cpu_state_t *cpu, uint32_t inst, uint8_t *mem) {
 	/*********/
 
 	uint32_t x;
-	if (i.funct3 == 0x0) {
-		x = cpu->pc + 4;
-		cpu->pc = i.rs1 + i.imm;
-	} else {
+	if (i.funct3 != 0x0) {
 		fprintf(stderr, "Illegal funct3\n");
+		return;
+	}
+
+	x = cpu->pc + 4;
+
+	uint32_t target;
+	if (get_valid_jalr_target(cpu->x[i.rs1], i.imm, &target) == 0) {
+		cpu->pc = target;
+	} else {
+		fprintf(stderr, "Illegal branch target: base=%"
+		        PRIu32 ", offset=%" PRId32 "\n",
+			cpu->x[i.rs1], i.imm);
+		return;
 	}
 
 	printf("rs1:%u  imm:%u  rd:%u\n",cpu->x[i.rs1],i.imm,cpu->x[i.rd]);
 	if (i.rd != 0) {
-		/* TODO: calculate & check addr */
 		cpu->x[i.rd] = x;
 	}
 
@@ -494,9 +524,18 @@ static void exec_jtype(cpu_state_t *cpu, uint32_t inst, uint8_t *mem) {
 	x = cpu->pc + 4;
 	cpu->pc += j.imm;
 
+	uint32_t target;
+	if (get_valid_branch_target(cpu->pc, (int32_t)j.imm, &target) == 0) {
+		cpu->pc = target;
+	} else {
+		fprintf(stderr, "Illegal branch target: base=%"
+		        PRIu32 ", offset=%" PRId32 "\n",
+			cpu->pc, j.imm);
+		return;
+	}
+
 	printf("imm:%u  rd:%u\n",j.imm,cpu->x[j.rd]);
 	if (j.rd != 0) {
-		/* TODO: calculate & check addr */
 		cpu->x[j.rd] = x;
 	}
 
@@ -517,9 +556,12 @@ static void exec_utype(cpu_state_t *cpu, uint32_t inst, uint8_t *mem) {
 	printf("\n");
 	/*********/
 
-	cpu->x[u.rd] = u.imm << 12;
+	if (u.rd != 0)
+		cpu->x[u.rd] = u.imm << 12;
+
 	cpu->pc += 4;
 
+
 	printf("rd:%u\n", cpu->x[u.rd]);
 	printf("rd:%x\n", cpu->x[u.rd]);
 }
@@ -538,7 +580,9 @@ static void exec_utype_auipc(cpu_state_t *cpu, uint32_t inst, uint8_t *mem) {
 	printf("\n");
 	/*********/
 
-	cpu->x[u.rd] = cpu->pc + (u.imm << 12);
+	if (u.rd != 0)
+		cpu->x[u.rd] = cpu->pc + (u.imm << 12);
+
 	cpu->pc += 4;
 
 	printf("rd:%u\n", cpu->x[u.rd]);