.gitignore

@@ -1,4 +1,2 @@
 /bin
 /fuzz
-/test/mld
-/test/msim

include/mips.h

@@ -84,6 +84,8 @@ enum mips_instruction_type {
 	MIPS_INS_LHU,
 	MIPS_INS_LUI,
 	MIPS_INS_LW,
+	MIPS_INS_LWL,
+	MIPS_INS_LWR,
 	MIPS_INS_MFHI,
 	MIPS_INS_MFLO,
 	MIPS_INS_MTHI,
@@ -92,9 +94,12 @@ enum mips_instruction_type {
 	MIPS_INS_MUH,
 	MIPS_INS_MULU,
 	MIPS_INS_MUHU,
+	MIPS_INS_MULT,
 	MIPS_INS_SB,
 	MIPS_INS_SH,
 	MIPS_INS_SW,
+	MIPS_INS_SWL,
+	MIPS_INS_SWR,
 	MIPS_INS_SLL,
 	MIPS_INS_SLLV,
 	MIPS_INS_SLT,
@@ -198,7 +203,7 @@ MIPS_INS(ANDI, .op = MIPS_OP_ANDI)
 /* BAL - branch and link */
 #define MIPS_OP_REGIMM     0b000001
 #define MIPS_FUNCT_BAL     0b10001
-MIPS_INS(BAL, .op = MIPS_OP_REGIMM, .bfunct = MIPS_FUNCT_BAL)
+MIPS_INS(BAL, .op = MIPS_OP_REGIMM, .funct = MIPS_FUNCT_BAL)
 
 /* BALC - branch and link, compact */
 #define MIPS_OP_BALC       0b111010
@@ -338,6 +343,14 @@ MIPS_INS(LUI, .op = MIPS_OP_LUI)
 #define MIPS_OP_LW         0b100011
 MIPS_INS(LW, .op = MIPS_OP_LW)
 
+/* LWL - load word left */
+#define MIPS_OP_LWL        0b100010
+MIPS_INS(LWL, .op = MIPS_OP_LWL)
+
+/* LWR - load word right */
+#define MIPS_OP_LWR        0b100110
+MIPS_INS(LWR, .op = MIPS_OP_LWR)
+
 /* MFHI - move from hi */
 #define MIPS_FUNCT_MFHI    0b010000
 MIPS_INS(MFHI, .op = MIPS_OP_SPECIAL, .funct = MIPS_FUNCT_MFHI)
@@ -376,6 +389,10 @@ MIPS_INS(MULU, .op = MIPS_OP_SPECIAL, .shamt = MIPS_SOP31_MULU,
 MIPS_INS(MUHU, .op = MIPS_OP_SPECIAL, .shamt = MIPS_SOP31_MUHU,
 	 .funct = MIPS_FUNCT_SOP31)
 
+/* MULT - multiply (OLD) */
+#define MIPS_FUNCT_MULT    0b011000
+MIPS_INS(MULT, .op = MIPS_OP_SPECIAL, .funct = MIPS_FUNCT_MULT)
+
 /* SB - store byte */
 #define MIPS_OP_SB         0b101000
 MIPS_INS(SB, .op = MIPS_OP_SB)
@@ -388,6 +405,14 @@ MIPS_INS(SH, .op = MIPS_OP_SH)
 #define MIPS_OP_SW         0b101011
 MIPS_INS(SW, .op = MIPS_OP_SW)
 
+/* SWL - store word left */
+#define MIPS_OP_SWL        0b101010
+MIPS_INS(SWL, .op = MIPS_OP_SWL)
+
+/* SWR - store word right */
+#define MIPS_OP_SWR        0b101110
+MIPS_INS(SWR, .op = MIPS_OP_SWR)
+
 /* SLL - shift left logical */
 #define MIPS_FUNCT_SLL     0b000000
 MIPS_INS(SLL, .op = MIPS_OP_SPECIAL, .funct = MIPS_FUNCT_SLL)

lib/runtime.asm

@@ -25,6 +25,6 @@ _start:
 	jal main
 
 	# exit
-	move	$a0, $v0
+	move $a0, $v0
-	li	$v0, 60
+	li $v0, 1
 	syscall

masm/lex.c

@@ -101,12 +101,6 @@ static int lex_string(struct lexer *lexer,char text[MAX_LEX_LENGTH])
 		if (c == '"')
 			break;
 
-		// strings cannot span multiple lines
-		if (c == '\n') {
-			ERROR_POS(pos, "reached newline before end of string");
-			return M_ERROR;
-		}
-
 		// match escape character
 		if (c == '\\') {
 			switch (lex_peek(lexer)) {
@@ -129,6 +123,12 @@ static int lex_string(struct lexer *lexer,char text[MAX_LEX_LENGTH])
 			}
 		}
 
+		// strings cannot span multiple lines
+		if (c == '\n') {
+			ERROR_POS(pos, "reached newline before end of string");
+			return M_ERROR;
+		}
+
 		if (len + 1 == MAX_LEX_LENGTH) {
 			ERROR_POS(pos, "string has max length of %d",
 				MAX_LEX_LENGTH);

masm/parse.c

@@ -148,6 +148,8 @@ const enum mips_parse_format mips_parse_formats[] = {
 	FORMAT(LHU, SL)
 	FORMAT(LUI, SLI)
 	FORMAT(LW, SL)
+	FORMAT(LWL, SL)
+	FORMAT(LWR, SL)
 	FORMAT(MFHI, RD)
 	FORMAT(MFLO, RD)
 	FORMAT(MTHI, RS)
@@ -156,9 +158,11 @@ const enum mips_parse_format mips_parse_formats[] = {
 	FORMAT(MUH, R)
 	FORMAT(MULU, R)
 	FORMAT(MUHU, R)
+	FORMAT(MULT, R2)
 	FORMAT(SB, SL)
 	FORMAT(SH, SL)
 	FORMAT(SW, SL)
+	FORMAT(SWL, SL)
 	FORMAT(SLL, S)
 	FORMAT(SLLV, SV)
 	FORMAT(SLT, R)
@@ -858,9 +862,9 @@ static int parse_pseudo_la(struct parser *parser, struct ins_expr *expr)
 	expr->ins[0] = mips_instructions[MIPS_INS_LUI];
 	expr->ins[0].data.rt = reg;
 	expr->ins[0].data.immd = B16(hi);
-	expr->ins[1] = mips_instructions[MIPS_INS_ADDI];
+	expr->ins[1] = mips_instructions[MIPS_INS_ORI];
 	expr->ins[1].data.rt = reg;
-	expr->ins[1].data.rs = reg;
+	expr->ins[1].data.rs = MIPS_REG_ZERO;
 	expr->ins[1].data.immd = B16(lo);
 
 	return M_SUCCESS;
@@ -912,14 +916,13 @@ static int parse_pseudo_instruction(struct parser *parser,
 	else CHK(move)
 		res = parse_pseudo_move(parser, expr);
 
-	if (res) {
+	if (res)
-		// reset on fail
 		lexer_load(parser->lexer, &state);
-		expr->ins[0].data.raw = 0;
+
-		expr->ins[1].data.raw = 0;
+	expr->ins[0].data.raw = 0;
-		expr->ref[0] = (struct reference) {0};
+	expr->ins[1].data.raw = 0;
-		expr->ref[1] = (struct reference) {0};
+	expr->ref[0] = (struct reference) {0};
-	}
+	expr->ref[1] = (struct reference) {0};
 
 	log_disabled = 0;
 	return res;

mld/link.c

@@ -125,18 +125,7 @@ static int relocate_segment_name(struct linker *linker, const char *name)
 				if (segtab_ent_push(ent, seg))
 					return M_ERROR;
 			} else {
-				// update vaddr to be page aligned
+				// else create a new segment
-				uint32_t m = seg->new_vaddr % SEC_ALIGN;
-				if (m) {
-					uint32_t add = SEC_ALIGN - m;
-					seg->new_vaddr += add;
-					if (B32(seg->phdr->p_flags) & PF_X)
-						linker->text_vaddr += add;
-					else
-						linker->data_vaddr += add;
-				}
-
-                                // else create a new segment
 				if (segtab_push(&linker->segments, NULL, seg))
 					return M_ERROR;
 			}
@@ -547,23 +536,19 @@ static void update_offsets(struct linker *linker)
 	linker->ehdr.e_phoff = B32(ptr);
 	ptr += linker->phdr_len * sizeof(Elf32_Phdr);
 
+	// section padding
+	{
+		uint32_t mod = ptr % SEC_ALIGN;
+		if (mod != 0)
+			linker->secalign = (SEC_ALIGN - mod);
+		else
+			 linker->secalign = 0;
+		ptr += linker->secalign;
+	}
+
 	// sections
 	for (uint32_t i = 0; i < linker->segments.len; i++) {
 		struct segment_table_entry *ent = &linker->segments.entries[i];
-
-		// section padding
-		{
-			uint32_t m = ptr % SEC_ALIGN;
-			if (m) {
-				uint32_t add = SEC_ALIGN - m;
-				ptr += add;
-				ent->off = ptr;
-				ent->padding = add;
-			} else {
-				ent->padding = 0;
-			}
-		}
-
 		uint32_t idx = i + 1;
 		uint32_t size = segtab_ent_size(ent);
 		linker->phdr[i].p_offset = B32(ptr);
@@ -619,16 +604,15 @@ static int write_file(struct linker *linker)
 	// phdr
 	res |= fwrite(linker->phdr, sizeof(Elf32_Phdr), linker->phdr_len, out);
 
+	// section padding
+	for (uint32_t i = 0; i < linker->secalign; i++) {
+		uint8_t zero = 0;
+		res |= fwrite(&zero, 1, 1, out);
+	}
+
 	// sections
 	for (uint32_t i = 0; i < linker->segments.len; i++) {
 		struct segment_table_entry *ent = &linker->segments.entries[i];
-		// section padding
-		{
-			for (uint32_t i = 0; i < ent->padding; i++) {
-				uint8_t zero = 0;
-				res |= fwrite(&zero, 1, 1, out);
-			}
-		}
 		for (uint32_t j = 0; j < ent->len; j++) {
 			struct segment *seg = ent->parts[j];
 			res |= fwrite(seg->bytes, 1, seg->size, out);

mld/link.h

@@ -170,8 +170,6 @@ struct segment_table_entry {
 	uint32_t vaddr;
 	// weak segment pointers. we do not own these!!!
 	struct segment **parts;
-	// section padding
-	uint32_t padding;
 };
 
 int segtab_ent_init(struct segment_table_entry *ent);
@@ -275,6 +273,9 @@ struct linker {
 	uint32_t strtab_shidx;
 	uint32_t shstrtab_shidx;
 
+	// section alignment after phdr bytes
+	uint32_t secalign;
+
 	// all segments
 	struct segment_table segments;
 };

msim/debug.c

@@ -1,79 +0,0 @@
-#include <merror.h>
-#include <stdint.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <melf.h>
-
-#include "sim.h"
-
-static uint32_t read_num() {
-	int i = 0;
-	while (1) {
-		int c = getc(stdin);
-		if (c < '0' || c > '9') {
-			ungetc(c, stdin);
-			break;
-		}
-		i *= 10;
-		i += c - '0';
-	}
-
-	if (i)
-		return i;
-	return 1;
-}
-
-_Noreturn void sim_debug(struct simulator *sim) {
-
-	int c;
-	sim->pc = sim->entry;
-	sim->current_pc = sim->pc;
-
-prompt:
-	printf(">> ");
-	fflush(stdout);
-next:
-	switch ((c = getchar())) {
-
-	/* skip whitespace */
-	case ' ':
-	case '\t':
-		goto next;
-
-	/* ignore nl */
-	case '\n':
-		goto prompt;
-
-	/* exit on eof */
-	case EOF:
-		exit(0);
-		break;
-
-	/* dump registers */
-	case 'r':
-		sim_dump_reg(sim);
-		break;
-
-	/* step ins */
-	case 's': {
-		for (uint32_t i = read_num(); i > 0; i--)
-			sim_step(sim);
-		break;
-	}
-
-	/* print curr ins */
-	case 'i':
-		printf("0x%08x\n", B32(* (uint32_t *) (uintptr_t) sim->pc));
-		break;
-
-	case 'a':
-		printf("0x%08x\n", sim->pc);
-		break;
-
-	default:
-		ERROR("unknown command '%c'", c);
-		break;
-	}
-
-	goto next;
-}

msim/fault.c

@@ -1,56 +0,0 @@
-#include "fault.h"
-#include "sim.h"
-#include <signal.h>
-#include <time.h>
-
-static struct simulator *sim;
-
-static void sigsegv_handler(int sig, siginfo_t *info, void *ucontext)
-{
-	(void) sig;
-	(void) ucontext;
-
-	const char *inner = "";
-	switch (info->si_code) {
-	case SEGV_MAPERR:
-		inner = ": address not mapped to object";
-		break;
-	case SEGV_ACCERR:
-		inner = ": invalid premissions for mapped object";
-		break;
-	case SEGV_BNDERR:
-		inner = ": failed address bound checks";
-		break;
-	case SEGV_PKUERR:
-		inner = ": access was denied by memory protection";
-		break;
-	}
-
-	sim_dump(sim, "page fault at %p%s", info->si_addr, inner);
-}
-
-static void sigfpe_handler(int sig, siginfo_t *info, void *ucontext)
-{
-	(void) sig;
-	(void) info;
-	(void) ucontext;
-
-	sim_dump(sim, "floating point exception");
-
-}
-
-void init_handlers(struct simulator *s)
-{
-	struct sigaction act = {0};
-	sim = s;
-
-	/* sigsegv */
-	act.sa_sigaction = sigsegv_handler;
-	act.sa_flags = SA_SIGINFO;
-	sigaction(SIGSEGV, &act, NULL);
-
-	/* sigfpe */
-	act.sa_sigaction = sigfpe_handler;
-	act.sa_flags = SA_SIGINFO;
-	sigaction(SIGFPE, &act, NULL);
-}

msim/fault.h

@@ -1,10 +0,0 @@
-/* Copyright (c) 2024 Freya Murphy */
-
-#ifndef __FAULT_H__
-#define __FAULT_H__
-
-#include "sim.h"
-
-void init_handlers(struct simulator *s);
-
-#endif /* __FAULT_H__ */

msim/ins.c

@@ -1,373 +0,0 @@
-#include <mips.h>
-#include <melf.h>
-#include <stdint.h>
-#include <stdio.h>
-#include <unistd.h>
-
-#include "sim.h"
-
-#define I16(n) ((int32_t)(uint16_t)(n))
-
-static void sim_ins_special_sop30(struct simulator *sim,
-				  union mips_instruction_data ins)
-{
-	switch (ins.shamt) {
-	case MIPS_SOP30_MUL:
-		sim->reg[ins.rd] = ((int64_t)sim->reg[ins.rs] /
-				(int64_t)sim->reg[ins.rt]) >> 0;
-		break;
-
-	case MIPS_SOP30_MUH:
-		sim->reg[ins.rd] = ((int64_t)sim->reg[ins.rs] /
-				(int64_t)sim->reg[ins.rt]) >> 32;
-		break;
-
-	default:
-		sim_dump(sim, "unknown sop30 funct (0b%06b)", ins.shamt);
-	}
-}
-
-static void sim_ins_special_sop31(struct simulator *sim,
-				  union mips_instruction_data ins)
-{
-	switch (ins.shamt) {
-	case MIPS_SOP31_MULU:
-		sim->reg[ins.rd] = ((uint64_t)sim->reg[ins.rs] /
-				(uint64_t)sim->reg[ins.rt]) >> 0;
-		break;
-
-	case MIPS_SOP31_MUHU:
-		sim->reg[ins.rd] = ((uint64_t)sim->reg[ins.rs] /
-				(uint64_t)sim->reg[ins.rt]) >> 32;
-		break;
-
-	default:
-		sim_dump(sim, "unknown sop31 funct (0b%06b)", ins.shamt);
-	}
-}
-
-static void sim_ins_special_sop32(struct simulator *sim,
-				  union mips_instruction_data ins)
-{
-	switch (ins.shamt) {
-	case MIPS_SOP32_DIV:
-		sim->reg[ins.rd] = (int32_t)sim->reg[ins.rs] /
-				(int32_t)sim->reg[ins.rt];
-		break;
-
-	case MIPS_SOP32_MOD:
-		sim->reg[ins.rd] = (int32_t)sim->reg[ins.rs] %
-				(int32_t)sim->reg[ins.rt];
-		break;
-
-	default:
-		sim_dump(sim, "unknown sop32 funct (0b%06b)", ins.shamt);
-	}
-}
-
-static void sim_ins_special_sop33(struct simulator *sim,
-				  union mips_instruction_data ins)
-{
-	switch (ins.shamt) {
-	case MIPS_SOP33_DIVU:
-		sim->reg[ins.rd] = sim->reg[ins.rs] / sim->reg[ins.rt];
-		break;
-
-	case MIPS_SOP33_MODU:
-		sim->reg[ins.rd] = sim->reg[ins.rs] % sim->reg[ins.rt];
-		break;
-
-	default:
-		sim_dump(sim, "unknown sop33 funct (0b%06b)", ins.shamt);
-	}
-}
-
-static void sim_ins_special(struct simulator *sim,
-			    union mips_instruction_data ins)
-{
-	switch (ins.funct) {
-	case MIPS_FUNCT_ADD:
-		sim->reg[ins.rd] = (int32_t)sim->reg[ins.rs] +
-				(int32_t)sim->reg[ins.rt];
-		break;
-
-	case MIPS_FUNCT_ADDU:
-		sim->reg[ins.rd] = sim->reg[ins.rs] + sim->reg[ins.rt];
-		break;
-
-	case MIPS_FUNCT_AND:
-		sim->reg[ins.rd] = sim->reg[ins.rs] & sim->reg[ins.rt];
-		break;
-
-	case MIPS_FUNCT_SOP30:
-		sim_ins_special_sop30(sim, ins);
-		break;
-
-	case MIPS_FUNCT_SOP31:
-		sim_ins_special_sop31(sim, ins);
-		break;
-
-	case MIPS_FUNCT_SOP32:
-		sim_ins_special_sop32(sim, ins);
-		break;
-
-	case MIPS_FUNCT_SOP33:
-		sim_ins_special_sop33(sim, ins);
-		break;
-
-	case MIPS_FUNCT_JALR:
-		sim->reg[MIPS_REG_RA] = sim->pc;
-		/* fall through */
-	case MIPS_FUNCT_JR:
-		sim->pc = sim->reg[ins.rs];
-		break;
-
-	case MIPS_FUNCT_MFHI:
-		sim->reg[ins.rd] = sim->hi;
-		break;
-
-	case MIPS_FUNCT_MFLO:
-		sim->reg[ins.rd] = sim->low;
-		break;
-
-	case MIPS_FUNCT_MTHI:
-		sim->hi = sim->reg[ins.rd];
-		break;
-
-	case MIPS_FUNCT_MTLO:
-		sim->low = sim->reg[ins.rd];
-		break;
-
-	case MIPS_FUNCT_SLL:
-		sim->reg[ins.rd] = sim->reg[ins.rt] << ins.shamt;
-		break;
-
-	case MIPS_FUNCT_SLLV:
-		sim->reg[ins.rd] = sim->reg[ins.rt] << sim->reg[ins.rs];
-		break;
-
-	case MIPS_FUNCT_SLT:
-		sim->reg[ins.rd] = (int32_t)sim->reg[ins.rs] < (int32_t)sim->reg[ins.rt] ? 1 : 0;
-		break;
-
-	case MIPS_FUNCT_SLTU:
-		sim->reg[ins.rd] = sim->reg[ins.rs] < sim->reg[ins.rt] ? 1 : 0;
-		break;
-
-	case MIPS_FUNCT_SRA:
-		sim->reg[ins.rd] = (int32_t)sim->reg[ins.rt] >> ins.shamt;
-		break;
-
-	case MIPS_FUNCT_SRAV:
-		sim->reg[ins.rd] = (int32_t)sim->reg[ins.rt] >> sim->reg[ins.rs];
-		break;
-
-	case MIPS_FUNCT_SRL:
-		sim->reg[ins.rd] = sim->reg[ins.rt] >> ins.shamt;
-		break;
-
-	case MIPS_FUNCT_SRLV:
-		sim->reg[ins.rd] = sim->reg[ins.rt] >> sim->reg[ins.rs];
-		break;
-
-	case MIPS_FUNCT_SUB:
-		sim->reg[ins.rd] = (int32_t)sim->reg[ins.rs] -
-				(int32_t)sim->reg[ins.rt];
-		break;
-
-	case MIPS_FUNCT_SUBU:
-		sim->reg[ins.rd] = sim->reg[ins.rs] - sim->reg[ins.rt];
-		break;
-
-	case MIPS_FUNCT_SYSCALL:
-		sim->reg[MIPS_REG_V0] = syscall(
-				sim->reg[MIPS_REG_V0],
-				sim->reg[MIPS_REG_A0],
-				sim->reg[MIPS_REG_A1],
-				sim->reg[MIPS_REG_A2],
-				sim->reg[MIPS_REG_A3]
-			);
-		break;
-
-	case MIPS_FUNCT_OR:
-		sim->reg[ins.rd] = sim->reg[ins.rs] | sim->reg[ins.rt];
-		break;
-
-	case MIPS_FUNCT_NOR:
-		sim->reg[ins.rd] = !(sim->reg[ins.rs] | sim->reg[ins.rt]);
-		break;
-
-	case MIPS_FUNCT_XOR:
-		sim->reg[ins.rd] = sim->reg[ins.rs] ^ sim->reg[ins.rt];
-		break;
-
-	default:
-		sim_dump(sim, "unknown funct (0b%05b)", ins.funct);
-	}
-}
-
-static void sim_ins_regimm(struct simulator *sim,
-			   union mips_instruction_data ins)
-{
-	switch (ins.bfunct) {
-	case MIPS_FUNCT_BGEZAL:
-	case MIPS_FUNCT_BGEZALL:
-		sim->reg[MIPS_REG_RA] = sim->pc;
-		/* fall through */
-	case MIPS_FUNCT_BGEZ:
-	case MIPS_FUNCT_BGEZL:
-		if ((int32_t)sim->reg[ins.rs] >= 0)
-			sim->pc += ins.offset << 2;
-		break;
-
-	case MIPS_FUNCT_BLTZAL:
-	case MIPS_FUNCT_BLTZALL:
-		sim->reg[MIPS_REG_RA] = sim->pc;
-		/* fall through */
-	case MIPS_FUNCT_BLTZ:
-	case MIPS_FUNCT_BLTZL:
-		if ((int32_t)sim->reg[ins.rs] < 0)
-			sim->pc += ins.offset << 2;
-		break;
-
-	default:
-		sim_dump(sim, "unknown bfunct (0b%06b)", ins.bfunct);
-	}
-}
-
-void sim_ins(struct simulator *sim, uint32_t raw)
-{
-	// get ins parts
-	union mips_instruction_data ins = {
-		.raw = B32(raw)
-	};
-
-	// reset zero reg
-	sim->reg[MIPS_REG_ZERO] = 0;
-
-	switch (ins.op) {
-	case MIPS_OP_SPECIAL:
-		sim_ins_special(sim, ins);
-		break;
-
-	case MIPS_OP_REGIMM:
-		sim_ins_regimm(sim, ins);
-		break;
-
-	case MIPS_OP_ADDI:
-		sim->reg[ins.rt] = (int32_t)sim->reg[ins.rs] +
-				(int16_t) ins.immd;
-		break;
-
-	case MIPS_OP_ADDIU:
-		sim->reg[ins.rt] = sim->reg[ins.rs] + ins.immd;
-		break;
-
-	case MIPS_OP_ANDI:
-		sim->reg[ins.rt] = sim->reg[ins.rs] & ins.immd;
-		break;
-
-	case MIPS_OP_BALC:
-		sim->reg[MIPS_REG_RA] = sim->pc;
-		/* fall through */
-	case MIPS_OP_BC:
-		sim->pc += ins.offs26 << 2;
-		break;
-
-	case MIPS_OP_BEQ:
-	case MIPS_OP_BEQL:
-		if (sim->reg[ins.rs] == sim->reg[ins.rt])
-			sim->pc += ins.offset << 2;
-		break;
-
-	case MIPS_OP_BGTZ:
-	case MIPS_OP_BGTZL:
-		if ((int32_t)sim->reg[ins.rs] <= 0)
-			sim->pc += ins.offset << 2;
-		break;
-
-	case MIPS_OP_BLEZ:
-	case MIPS_OP_BLEZL:
-		if ((int32_t)sim->reg[ins.rs] <= 0)
-			sim->pc += ins.offset << 2;
-		break;
-
-	case MIPS_OP_BNE:
-	case MIPS_OP_BNEL:
-		if (sim->reg[ins.rs] != sim->reg[ins.rt])
-			sim->pc += ins.offset << 2;
-		break;
-
-	case MIPS_OP_JAL:
-		sim->reg[MIPS_REG_RA] = sim->pc;
-		/* fall through */
-	case MIPS_OP_J:
-		sim->pc = ins.target << 2;
-		break;
-
-	case MIPS_OP_LB:
-		sim->reg[ins.rt] = * (int8_t *) (uintptr_t) (sim->reg[ins.rs]
-				+ ins.offset);
-		break;
-
-	case MIPS_OP_LBU:
-		sim->reg[ins.rt] = * (uint8_t *) (uintptr_t) (sim->reg[ins.rs]
-				+ ins.offset);
-		break;
-
-	case MIPS_OP_LH:
-		sim->reg[ins.rt] = * (int16_t *) (uintptr_t) (sim->reg[ins.rs]
-				+ ins.offset);
-		break;
-
-	case MIPS_OP_LHU:
-		sim->reg[ins.rt] = * (uint16_t *) (uintptr_t) (sim->reg[ins.rs]
-				+ ins.offset);
-		break;
-
-	case MIPS_OP_LUI:
-		sim->reg[ins.rt] = ins.immd << 16;
-		break;
-
-	case MIPS_OP_LW:
-		sim->reg[ins.rt] = * (uint32_t *) (uintptr_t) (sim->reg[ins.rs]
-				+ ins.offset);
-		break;
-
-	case MIPS_OP_SB:
-		* (uint8_t *) (uintptr_t) (sim->reg[ins.rs] +
-				+ ins.offset) = sim->reg[ins.rt];
-		break;
-
-	case MIPS_OP_SH:
-		* (uint16_t *) (uintptr_t) (sim->reg[ins.rs] +
-				ins.offset) = sim->reg[ins.rt];
-		break;
-
-	case MIPS_OP_SW:
-		* (uint32_t *) (uintptr_t) (sim->reg[ins.rs] +
-				ins.offset) = sim->reg[ins.rt];
-		break;
-
-	case MIPS_OP_SLTI:
-		sim->reg[ins.rt] = (int32_t)sim->reg[ins.rs] <
-				(int16_t)ins.immd ? 1 : 0;
-		break;
-
-	case MIPS_OP_SLTIU:
-		sim->reg[ins.rt] = sim->reg[ins.rs] < ins.immd ? 1 : 0;
-		break;
-
-	case MIPS_OP_ORI:
-		sim->reg[ins.rt] = sim->reg[ins.rs] | ins.immd;
-		break;
-
-	case MIPS_OP_XORI:
-		sim->reg[ins.rt] = sim->reg[ins.rs] ^ ins.immd;
-		break;
-
-	default:
-		sim_dump(sim, "unknown op code (0b%05b)", ins.op);
-	}
-}
-

msim/load.c

@@ -1,226 +0,0 @@
-#include <merror.h>
-#include <elf.h>
-#include <melf.h>
-#include <stdint.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <sys/mman.h>
-
-#include "sim.h"
-
-#define SEC_ALIGN 0x1000
-
-struct load_state {
-	FILE *file;
-	int fd;
-	uint32_t file_sz;
-
-	Elf32_Phdr *phdr;
-	uint32_t phdr_len;
-	Elf32_Ehdr ehdr;
-};
-
-static int assert_ehdr(const void *const given, const void *const assert,
-		       size_t size)
-{
-	if (memcmp(given, assert, size) == 0)
-		return M_SUCCESS;
-	ERROR("invalid elf ehdr");
-	return M_ERROR;
-}
-
-static int load_ehdr(struct simulator *sim, struct load_state *state)
-{
-	Elf32_Ehdr ehdr;
-	fseek(state->file, 0, SEEK_SET);
-	if (fread(&ehdr, sizeof(Elf32_Ehdr), 1, state->file) != 1) {
-		ERROR("cannot load ehdr");
-		return M_ERROR;
-	}
-
-	/**
-	 * Compare each "static" value in the ehdr and make sure it
-	 * is what it should be. If not throw and error and eventually
-	 * return.
-	 */
-
-	Elf32_Ehdr baseline = MIPS_ELF_EHDR;
-	baseline.e_type = B16(ET_EXEC);
-
-	#define EHDR_ASSERT(name, size)                          \
-			if (res == M_SUCCESS)                    \
-			  res |= assert_ehdr(&baseline.e_##name, \
-			  &ehdr.e_##name, size)                  \
-
-	int res = 0;
-	EHDR_ASSERT(ident,     EI_NIDENT);
-	EHDR_ASSERT(type,      sizeof(Elf32_Half));
-	EHDR_ASSERT(machine,   sizeof(Elf32_Half));
-	EHDR_ASSERT(version,   sizeof(Elf32_Word));
-	EHDR_ASSERT(flags,     sizeof(Elf32_Word));
-	EHDR_ASSERT(ehsize,    sizeof(Elf32_Half));
-	EHDR_ASSERT(phentsize, sizeof(Elf32_Half));
-	EHDR_ASSERT(shentsize, sizeof(Elf32_Half));
-
-	#undef EHDR_ASSERT
-
-	if (res)
-		return M_ERROR;
-
-	state->ehdr = ehdr;
-	sim->entry = B32(ehdr.e_entry);
-
-	return M_SUCCESS;
-}
-
-static int load_phdr(struct load_state *state)
-{
-	Elf32_Phdr *phdr = NULL;
-
-	uint32_t off = B32(state->ehdr.e_phoff);
-	uint16_t len = B16(state->ehdr.e_phnum);
-
-	if (BOUND_CHK(state->file_sz, len, off)) {
-		ERROR("elf phdr location invalid");
-		return M_ERROR;
-	}
-
-	phdr = malloc(sizeof(Elf32_Phdr) * len);
-	if (phdr == NULL) {
-		PERROR("cannot alloc");
-		return M_ERROR;
-	}
-
-	fseek(state->file, off, SEEK_SET);
-	if (fread(phdr, sizeof(Elf32_Phdr), len, state->file) != len) {
-		free(phdr);
-		PERROR("cannot read phdr");
-		return M_ERROR;
-	}
-
-	state->phdr = phdr;
-	state->phdr_len = len;
-	return M_SUCCESS;
-}
-
-static int load_segment(struct simulator *sim,
-			struct load_state *state, Elf32_Phdr *hdr)
-{
-	uint32_t off = B32(hdr->p_offset);
-	uint32_t len = B32(hdr->p_filesz);
-	uint32_t is_text = B32(hdr->p_flags) & PF_X;
-
-	if (BOUND_CHK(state->file_sz, len, off)) {
-		ERROR("segment location invalid");
-		return M_ERROR;
-	}
-
-	uintptr_t addr = 0;
-	uint32_t add = 0;
-
-	if (len % SEC_ALIGN) {
-		add = SEC_ALIGN - (len % SEC_ALIGN);
-		len += add;
-	}
-
-	if (is_text) {
-		addr = sim->text_max;
-		sim->text_max += len;
-	} else {
-		addr = sim->data_max;
-		sim->data_max += len;
-	}
-
-	bool read = B32(hdr->p_flags) & PF_R;
-	bool write = B32(hdr->p_flags) & PF_W;
-
-	uint32_t prot = 0;
-	if (read)
-		prot |= PROT_READ;
-	if (write)
-		prot |= PROT_WRITE;
-
-	void *res = mmap((void*)addr, len, prot, MAP_PRIVATE | MAP_FIXED,
-		  state->fd, off);
-
-	if ((uintptr_t)res != addr) {
-		PERROR("failed to map executable");
-		return M_ERROR;
-	}
-
-	return M_SUCCESS;
-}
-
-static int load_memory(struct simulator *sim, struct load_state *state)
-{
-	uint32_t base = 0;
-
-	for (uint32_t i = 0; i < state->phdr_len; i++) {
-		Elf32_Phdr *hdr = NULL;
-		uint32_t min = UINT32_MAX;
-
-		if (B32(state->phdr[i].p_filesz) < 1)
-			continue;
-
-		// we need to load segments in order
-		for (uint32_t j = 0; j < state->phdr_len; j++) {
-			Elf32_Phdr *temp = &state->phdr[j];
-			uint32_t off = B32(temp->p_offset);
-			uint32_t len = B32(temp->p_filesz);
-
-			if (len < 1)
-				continue;
-
-			if (off <= base)
-				continue;
-
-			if (off >= min)
-				continue;
-
-			min = off;
-			hdr = temp;
-		}
-
-		base = min;
-
-		if (hdr == NULL) {
-			ERROR("invalid elf phdr");
-			return M_ERROR;
-		}
-
-		if (load_segment(sim, state, hdr))
-			return M_ERROR;
-	}
-
-	return M_SUCCESS;
-}
-
-int sim_load_file(struct simulator *sim) {
-	struct load_state state;
-
-	state.file = fopen(sim->args->executable, "r");
-	if (state.file == NULL) {
-		PERROR("cannot read '%s'", state.file);
-		return M_ERROR;
-	}
-	state.fd = fileno(state.file);
-
-	// get filesize
-	fseek(state.file, 0, SEEK_END);
-	state.file_sz = ftell(state.file);
-	state.phdr = NULL;
-
-	int res = M_SUCCESS;
-	if (res == M_SUCCESS)
-		res = load_ehdr(sim, &state);
-	if (res == M_SUCCESS)
-		res = load_phdr(&state);
-	if (res == M_SUCCESS)
-		res = load_memory(sim, &state);
-
-	if (state.phdr)
-		free(state.phdr);
-	fclose(state.file);
-
-	return res;
-}

msim/main.c

@@ -1,73 +1,5 @@
-#include <stdlib.h>
-#include <stdio.h>
-#include <unistd.h>
-#include <merror.h>
-#include <signal.h>
 
-#include "fault.h"
+int main(void) {
-#include "sim.h"
+	// NOT YET IMPLEMENTED
-
+	return 1;
-static void help(void) {
-	printf("usage: msim [options] executable\n\n");
-	printf("options:\n");
-	printf("\t-h\t\tprints this help messaage\n");
-	printf("\t-c\t\tdisable runtime memory checks (allows segfault)\n");
-	printf("\t-d\t\truns the debugger\n");
-}
-
-int main(int argc, char **argv) {
-
-	struct simulator sim;
-	struct simulator_args args = {
-		.executable = NULL,
-		.debug = false,
-		.memchk = true,
-	};
-
-	int c;
-
-	while ((c = getopt(argc, argv, "hcd")) != 1) {
-		switch (c) {
-		case 'h':
-			help();
-			return M_SUCCESS;
-		case 'c':
-			args.memchk = false;
-			break;
-		case 'd':
-			args.debug = true;
-			break;
-		case '?':
-			return M_ERROR;
-		default:
-			goto next;
-		}
-	}
-
-next:
-	if (optind < argc - 1) {
-		ERROR("too many executables passed");
-		return M_ERROR;
-	}
-
-	if (optind >= argc) {
-		ERROR("no executable passed");
-		return M_ERROR;
-	}
-
-	/// set file name
-	args.executable = argv[optind];
-
-	/// create handlers
-	init_handlers(&sim);
-
-	/// init
-	if (sim_init(&sim, &args))
-		return M_ERROR;
-
-	/* _Noreturn */
-	if (args.debug)
-		sim_debug(&sim);
-	else
-		sim_run(&sim);
 }

msim/sim.c

@@ -1,93 +0,0 @@
-#include <merror.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <stdarg.h>
-
-#include "sim.h"
-#include "melf.h"
-
-void sim_dump_reg(struct simulator *sim)
-{
-	const char *names[32] = {
-		"zero", "at", "v0", "v1", "a0", "a1", "a2", "a3", "t0", "t1",
-		"t2", "t3", "t4", "t5", "t6", "t7", "s0", "s1", "s2", "s3",
-		"s4", "s5", "s6", "s7", "t8", "t9", "k0", "k1", "gp", "sp",
-		"fp", "ra"
-	};
-
-	for (uint32_t i = 0; i < 8; i++) {
-		for (uint32_t j = 0; j < 4; j++) {
-			if (j != 0)
-				fputc(' ', stderr);
-			int idx = i+j*8;
-			fprintf(stderr, "$%s:\t0x%08x", names[idx], sim->reg[idx]);
-		}
-		fputc('\n', stderr);
-	}
-}
-
-__attribute__((format(printf, 2, 3)))
-_Noreturn void sim_dump(struct simulator *sim, const char *format, ...) {
-
-	va_list list;
-	va_start(list, format);
-
-	// header
-	fprintf(stderr, "\n\t\t!!! An exception has occurred !!!\n\n");
-	fprintf(stderr, "\033[31merror: \033[0m");
-	vfprintf(stderr, format, list);
-	fputc('\n', stderr);
-
-	// pc
-	uint32_t pc = sim->current_pc;
-	fprintf(stderr, "pc: 0x%08x\n", pc);
-
-	if (pc >= sim->text_min && pc < sim->text_max)
-		fprintf(stderr, "ins: 0x%08x\n", B32(* (uint32_t *) (uintptr_t) pc));
-
-	// registers
-	fprintf(stderr, "registers:\n");
-	sim_dump_reg(sim);
-
-	exit(1);
-}
-
-void sim_step(struct simulator *sim)
-{
-	if (sim->pc < sim->text_min || sim->pc >= sim->text_max)
-		sim_dump(sim, "program counter reached non executable memory");
-
-	uint32_t ins = * (uint32_t *) (uintptr_t) sim->pc;
-	sim->pc += 4;
-	sim_ins(sim, ins);
-	sim->current_pc = sim->pc;
-}
-
-_Noreturn void sim_run(struct simulator *sim)
-{
-	sim->pc = sim->entry;
-	sim->current_pc = sim->pc;
-	while (1)
-		sim_step(sim);
-}
-
-int sim_init(struct simulator *sim, struct simulator_args *args) {
-	memset(sim->reg, 0, sizeof(uint32_t) * 32);
-	sim->data_max = MEM_DATA_ADDR;
-	sim->data_min = MEM_DATA_ADDR;
-	sim->text_max = MEM_TEXT_ADDR;
-	sim->text_min = MEM_TEXT_ADDR;
-	sim->args = args;
-
-	// load executable
-	if (sim_load_file(sim))
-		return M_ERROR;
-
-	// check entry
-	if (sim->entry < sim->text_min || sim->entry >= sim->text_max) {
-		ERROR("elf entrypoint invalid");
-		return M_ERROR;
-	}
-
-	return M_SUCCESS;
-}

msim/sim.h

@@ -1,87 +0,0 @@
-/* Copyright (c) 2024 Freya Murphy */
-
-#ifndef __SIM_H__
-#define __SIM_H__
-
-#include <elf.h>
-#include <stdint.h>
-
-/// arguments
-struct simulator_args {
-	char *executable;
-	bool memchk;
-	bool debug;
-};
-
-
-// when loading the executable, we need to bounds check to
-// make sure its within the file size
-//
-// this checks that
-// 1. the end is in the file
-// 2. the off and len doesnt integer overflow
-#define BOUND_CHK(size, len, off) \
-	((off) > UINT32_MAX - (len) || (off) + (len) > (size))
-
-///
-/// data must start at these
-/// addresses or the executable is
-/// invalid
-///
-#define MEM_TEXT_ADDR 0x00400000
-#define MEM_DATA_ADDR 0x10000000
-
-struct simulator {
-	struct simulator_args *args;
-
-
-	/// the registers
-	uint32_t reg[32];
-
-	/// the program counter
-	uint32_t pc;
-
-	/// the current executing pc
-	uint32_t current_pc;
-
-	/// low and hi
-	uint32_t low;
-	uint32_t hi;
-
-	/// memory address bounds
-	uint32_t data_min;
-	uint32_t data_max;
-	uint32_t text_min;
-	uint32_t text_max;
-
-	// entrypoint
-	uint32_t entry;
-};
-
-/* initalize a simulator */
-int sim_init(struct simulator *sim, struct simulator_args *args);
-
-/* load a file into a simulator */
-int sim_load_file(struct simulator *sim);
-
-/* execute and instruction */
-void sim_ins(struct simulator *sim, uint32_t ins);
-
-/* execute the next instruction in the simulator */
-void sim_step(struct simulator *sim);
-
-/* run the simulator with the loaded state */
-_Noreturn void sim_run(struct simulator *sim);
-
-/* run the debugger for a simulator */
-_Noreturn void sim_debug(struct simulator *sim);
-
-/* panics the simulator */
-__attribute__((format(printf, 2, 3)))
-_Noreturn void sim_dump(struct simulator *sim, const char *format, ...);
-
-/* dumps registers */
-void sim_dump_reg(struct simulator *sim);
-
-#endif /* __SIM_H__ */
-

test/Makefile

@@ -1,25 +1,17 @@
+CC=afl-cc
+LD=afl-cc
+
 BIN=../bin
 
-ASM = $(shell find ./masm -type f -name "*.asm")
+.PHONY: masm mld msim
-OBJ = $(patsubst ./masm/%.asm,./mld/%.o,$(ASM))
-ELF = $(patsubst ./mld/%.o,./msim/%,$(OBJ))
-TEST = $(patsubst ./msim/%,%,$(ELF))
 
-.PHONY: build clean
+masm:
+	make -C ../masm clean build CC=$(CC) LD=$(LD)
+	$(BIN)/masm/masm -o ./mld/test.o ./masm/test.asm
 
-build: $(TEST)
+mld:
+	make -C ../mld clean build CC=$(CC) LD=$(LD)
+	$(BIN)/mld/mld -o ./msim/test ./mld/test.o
 
-clean:
+msim:
-	rm -fr ./mld
+	make -C ../msim clean build CC=$(CC) LD=$(LD)
-	rm -fr ./msim
-
-$(OBJ): ./mld/%.o : ./masm/%.asm
-	@mkdir -p $(@D)
-	$(BIN)/masm/masm -o $@ $<
-
-$(ELF): ./msim/% : ./mld/%.o ../lib/runtime.asm
-	@mkdir -p $(@D)
-	$(BIN)/mld/mld -o $@ $<
-
-$(TEST): % : ./msim/%
-	../tools/test.sh $@

test/masm/div.asm

@@ -1,17 +0,0 @@
-# Copyright (c) 2024 Freya Murphy
-
-# file: div.asm
-# test: should cause floting point exception
-
-.text
-.align 2
-.globl main
-
-main:
-	# divide by zero
-	li	$t0, 0
-	div	$t0, $t0, $t0
-
-	# return
-	li	$v0, 0
-	jr	$ra

test/masm/fault.asm

@@ -1,15 +0,0 @@
-# Copyright (c) 2024 Freya Murphy
-
-# file: div.asm
-# test: should cause page fault
-
-.text
-.align 2
-.globl main
-
-main:
-	lw	$t0, 0($zero)
-
-	# return
-	li	$v0, 0
-	jr	$ra

test/masm/fncall.asm

@@ -1,29 +0,0 @@
-# Copyright (c) 2024 Freya Murphy
-
-# file: fncall.asm
-# test: should return value from function call
-
-.text
-.align 2
-.globl main
-
-result:
-	move	$t0, $a0
-	move	$v0, $t0
-	jr	$ra
-
-main:
-	# save ra on stack
-	addi	$sp, $sp, -4
-	sw	$ra, 0($sp)
-
-	# set return to 17
-	li	$a0, 17
-	jal	result
-
-	# pop ra from stack
-	lw	$ra, 0($sp)
-	addi	$sp, $sp, 4
-
-	# return result
-	jr	$ra

test/masm/hello.asm

@@ -1,26 +0,0 @@
-# Copyright (c) 2024 Freya Murphy
-
-# file: div.asm
-# test: should print hello world
-
-.data
-.align 1
-
-hw:
-	.asciiz "Hello, world!\n"
-
-.text
-.align 2
-.globl main
-
-main:
-	# print hello world
-	li	$v0, 1
-	li	$a0, 1	# stdout
-	la	$a1, hw # load string
-	li	$a2, 14 # load length
-	syscall
-
-	# return 1
-	li	$v0, 0
-	jr	$ra

test/masm/test.asm

@@ -0,0 +1,242 @@
+# Copyright (c) 2024 Freya Murphy
+
+.data
+.align 2
+
+heap_start:
+	.space 4
+heap_len:
+	.space 4
+heap_free:
+	.space 4
+heap_ptr:
+	.space 4
+
+null:
+	.space 4
+
+.text
+.align 2
+.globl main
+
+# init the heap
+heap_init:
+	# sbrk(0)
+	li	$v0, 9
+	li	$a0, 0
+	syscall
+	sw	$v0, heap_start
+	sw	$v1, heap_len
+
+	# heap is empty, ptr at start
+	sw	$v0, heap_ptr
+	# heap is empty, size = len
+	sw	$v1, heap_free
+
+	jr	$ra
+
+
+
+# $a0 : amount of bytes to increase
+heap_increase:
+	# t0 : OLD heap len + 1
+	# t1 : heap ptr
+	# t2 : heap end
+	# t2 : heap free
+	# t3 : a0
+
+	# save current length
+	lw	$t0, heap_len
+
+	# save a0
+	move	$t3, $a0
+
+	# sbrk(amt)
+	li	$v0, 9
+	syscall
+	# sbrk(0)
+	li	$v0, 9
+	li	$a0, 0
+	syscall
+	sw	$v0, heap_start
+	sw	$v1, heap_len
+
+	lw	$t1, heap_ptr    # heap ptr
+	add	$t2, $v0, $v1   # heap end
+	sub	$t3, $t2, $t1   # heap free
+	sw	$t3, heap_free
+
+	# set return code to 1 if fail to allocate
+	# i.e. $v1 = $t0 or ($v1 < $t0 + 1)
+	# i.e. heap size hasen't changed
+	addi	$t0, $t0, 1
+	slt	$v0, $v1, $t0
+	jr	$ra
+
+
+
+# $a0 : amount of bytes to allocate
+malloc:
+	# t0 : heap free + 1
+	# t1 : if enough mem is free
+	# t2 : alloc size [(a0 align 4) + 4096 + 4]
+	# t3 : temp for heap_ptr
+	# t7 : alloc amt (a0 align 4) + 4
+	# t8 : temp for modulo
+
+	# save $a0
+	move	$t7, $a0
+	addi	$t7, $t7, 4 # add 4 bytes to save INTERAL ptr size
+
+	# align $t7 by 4
+	# allows us to use lw and sw in realloc
+	li	$t8, 4
+	div	$t8, $t7, $t8
+	mfhi	$t8
+	beq	$t8, $zero, malloc_aligned
+	addi	$t7, $t7, 4
+	sub	$t7, $t7, $t8
+
+malloc_aligned:
+	# check if we have enough memory free
+	lw	$t0, heap_free
+	addi	$t0, $t0, 1
+	slt	$t1, $t7, $t0
+	bne	$t1, $zero, malloc_hasmem
+
+	# set needed mem to alloc
+	# page size + alloc request
+
+	# save $ra and $t7
+	addi	$sp, $sp, -8
+	sw	$ra, 0($sp)
+	sw	$t7, 4($sp)
+
+	li	$t2, 4096
+	add	$t2, $t2, $t7
+	move	$a0, $t2
+	jal	heap_increase
+
+	# pop $ra and $t7
+	lw	$ra, 0($sp)
+	lw	$t7, 4($sp)
+	addi	$sp, $sp, 8
+
+	# check heap_increase return code
+	beq	$v0, $zero, malloc_hasmem
+
+malloc_error:
+	# failed to sbrk, return null
+	la	$v0, null
+	jr	$ra
+
+malloc_hasmem:
+	# set return value, and save ptr size in it
+	# add 4 to return ptr, since first 4 bytes are INTERNAL
+	addi	$t3, $t7, -4
+	lw	$v0, heap_ptr
+	sw	$t3, ($v0)
+	addi	$v0, $v0, 4
+
+	lw	$t3, heap_ptr
+	add	$t3, $t3, $t7 # increase ptr by alloc size
+	sw	$t3, heap_ptr
+
+	jr	$ra
+
+
+
+# $a0 : address of ptr
+free:
+	# haha hehe hoho
+	jr	$ra
+
+
+
+# $a0 : new size
+# $a1 : old ptr
+realloc:
+	# t0 : old ptr size
+	# t2 : new ptr addr
+
+	# check if $a0 is zero, if so then just free
+	bne	$a0, $zero, realloc_inner
+	move	$a0, $a1
+	la	$v0, null
+	j	free
+
+	# save to stack
+	addi	$sp, $sp, -12
+	sw	$ra, 0($sp)
+	sw	$a0, 4($sp)
+	sw	$a1, 8($sp)
+
+	jal	malloc
+
+	# pop to stack
+	lw	$ra, 0($sp)
+	lw	$a0, 4($sp)
+	lw	$a1, 8($sp)
+	addi	$sp, $sp, 12
+
+realloc_inner:
+	addi	$a1, $a1, -4
+	lw	$t0, ($a1)
+	addi	$a1, $a1, 4
+
+realloc_loop:
+	# loop until $t0 or $t1 is zero
+	beq	$t0, $zero, realloc_end
+	beq	$a0, $zero, realloc_end
+
+	addi	$a1, $a1, 4
+	addi	$t0, $t0, -4
+	addi	$a0, $a0, -4
+	#lw	$t3,
+
+	j	realloc_loop
+
+realloc_end:
+
+
+realloc_free:
+	jr	$ra
+
+
+main:
+	# push return address
+	addi	$sp, $sp, -4
+	sw	$ra, ($sp)
+
+	jal	heap_init
+
+	li	$a0, 24
+	jal	malloc
+
+	move	$a0, $v0
+	li	$v0, 1
+	syscall
+
+	li	$v0, 11
+	li	$a0, 10
+	syscall
+
+	li	$a0, 24
+	jal	malloc
+
+	move	$a0, $v0
+	li	$v0, 1
+	syscall
+
+	li	$v0, 11
+	li	$a0, 10
+	syscall
+
+	# pop return address
+	lw	$ra, ($sp)
+	addi	$sp, $sp, 4
+
+exit:
+	# exit with code 0
+	li	$v0, 0
+	jr	$ra

test/out/div

@@ -1,15 +0,0 @@
-
-		!!! An exception has occurred !!!
-
-error: floating point exception
-pc: 0x00400004
-ins: 0x0108409a
-registers:
-$zero:	0x00000000 $t0:	0x00000000 $s0:	0x00000000 $t8:	0x00000000
-$at:	0x00000000 $t1:	0x00000000 $s1:	0x00000000 $t9:	0x00000000
-$v0:	0x00000000 $t2:	0x00000000 $s2:	0x00000000 $k0:	0x00000000
-$v1:	0x00000000 $t3:	0x00000000 $s3:	0x00000000 $k1:	0x00000000
-$a0:	0x00000000 $t4:	0x00000000 $s4:	0x00000000 $gp:	0x00000000
-$a1:	0x00000000 $t5:	0x00000000 $s5:	0x00000000 $sp:	0x10001000
-$a2:	0x00000000 $t6:	0x00000000 $s6:	0x00000000 $fp:	0x00000000
-$a3:	0x00000000 $t7:	0x00000000 $s7:	0x00000000 $ra:	0x0040001c

test/out/div.status

@@ -1 +0,0 @@
-1

test/out/fault

@@ -1,15 +0,0 @@
-
-		!!! An exception has occurred !!!
-
-error: page fault at (nil): address not mapped to object
-pc: 0x00400000
-ins: 0x8c080000
-registers:
-$zero:	0x00000000 $t0:	0x00000000 $s0:	0x00000000 $t8:	0x00000000
-$at:	0x00000000 $t1:	0x00000000 $s1:	0x00000000 $t9:	0x00000000
-$v0:	0x00000000 $t2:	0x00000000 $s2:	0x00000000 $k0:	0x00000000
-$v1:	0x00000000 $t3:	0x00000000 $s3:	0x00000000 $k1:	0x00000000
-$a0:	0x00000000 $t4:	0x00000000 $s4:	0x00000000 $gp:	0x00000000
-$a1:	0x00000000 $t5:	0x00000000 $s5:	0x00000000 $sp:	0x10001000
-$a2:	0x00000000 $t6:	0x00000000 $s6:	0x00000000 $fp:	0x00000000
-$a3:	0x00000000 $t7:	0x00000000 $s7:	0x00000000 $ra:	0x00400018

test/out/fault.status

@@ -1 +0,0 @@
-1

test/out/fncall.status

@@ -1 +0,0 @@
-17

test/out/hello

@@ -1 +0,0 @@
-Hello, world!

test/out/hello.status

@@ -1 +0,0 @@
-0

tools/test.sh

@@ -1,41 +0,0 @@
-#!/bin/sh
-
-#
-# tests a binary
-# against a output and an exit code
-#
-
-dir="$(dirname "$0")"
-
-msim="$dir/../bin/msim/msim"
-bin="$dir/../test/msim/$1"
-
-out=$(cat "$dir/../test/out/$1")
-status=$(cat "$dir/../test/out/$1.status")
-
-temp=$(mktemp)
-
-$msim $bin &> $temp
-
-rstatus="$?"
-rout=$(cat $temp)
-rm $temp
-
-res=0
-
-if [ "$out" != "$rout" ]; then
-	res=1
-fi
-
-if [ "$status" != "$rstatus" ]; then
-	res=1
-fi
-
-if [ $res = 0 ]; then
-	printf "\033[32mPASSED\033[0m\n"
-else
-	printf "\033[31mFAILED\033[0m\n"
-	diff <(echo $out) <(echo $rout)
-fi
-
-exit $res