From c878dee7e0593c98836349fa98e76e7ee4a8c941 Mon Sep 17 00:00:00 2001
From: vhaudiquet <vhaudiquet343@hotmail.fr>
Date: Sun, 8 Oct 2023 16:40:03 +0200
Subject: [PATCH] Make CPU code thread safe

---
 Makefile              |  2 +-
 src/cpu/rv32cpu.c     |  8 ++++++++
 src/cpu/rv32cpu.h     |  2 ++
 src/gdbstub/gdbstub.c | 12 ++++++++++++
 4 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index b696ce1..f1f1728 100644
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,7 @@
 NAME=vriscv
 CC=gcc
 CFLAGS=-O3 -Wall -I src
-LDFLAGS=
+LDFLAGS=-lpthread
 BUILD_DIR=build
 
 C_FILES := $(shell find src/ -name '*.c')
diff --git a/src/cpu/rv32cpu.c b/src/cpu/rv32cpu.c
index c3d26a8..603ccff 100644
--- a/src/cpu/rv32cpu.c
+++ b/src/cpu/rv32cpu.c
@@ -9,6 +9,7 @@
 #include <stdio.h>
 
 rv32_cpu_t* cpu0;
+pthread_mutex_t* cpu0_mutex;
 
 typedef union RAW_INSTRUCTION
 {
@@ -40,6 +41,7 @@ static void cpu_print_instruction(instruction_t* instruction);
 void cpu_init()
 {
 	cpu0 = calloc(1, sizeof(rv32_cpu_t));
+	pthread_mutex_init(cpu0_mutex, 0);
 	cpu0->regs.zero = 0;
 }
 
@@ -645,6 +647,9 @@ void cpu_loop(rv32_cpu_t* cpu)
 {
 	while(1)
 	{
+		// Aquire CPU mutex
+		pthread_mutex_lock(cpu0_mutex);
+
 		// Fetch
 		raw_instruction_t raw_instruction;
 		if(cpu->pc > memory_size - 4)
@@ -668,6 +673,9 @@ void cpu_loop(rv32_cpu_t* cpu)
 		cpu->regs.zero = 0;
 
 		cpu->pc += 4;
+
+		// Let go of cpu mutex
+		pthread_mutex_unlock(cpu0_mutex);
 	}
 }
 
diff --git a/src/cpu/rv32cpu.h b/src/cpu/rv32cpu.h
index 5925c88..a2f947d 100644
--- a/src/cpu/rv32cpu.h
+++ b/src/cpu/rv32cpu.h
@@ -2,6 +2,7 @@
 #define RV32CPU_H
 
 #include <stdint.h>
+#include <pthread.h>
 
 /*
 * This is a structure encoding for the registers of
@@ -188,6 +189,7 @@ typedef struct RV32_CPU
 } rv32_cpu_t;
 
 extern rv32_cpu_t* cpu0;
+extern pthread_mutex_t* cpu0_mutex;
 void cpu_init();
 void cpu_loop(rv32_cpu_t* cpu);
 
diff --git a/src/gdbstub/gdbstub.c b/src/gdbstub/gdbstub.c
index 2caa5c8..b22911f 100644
--- a/src/gdbstub/gdbstub.c
+++ b/src/gdbstub/gdbstub.c
@@ -183,6 +183,9 @@ void gdbstub_thread_gdb()
 			// g : read all registers -> send back all registers
 			char resp[32 * 8 + 8 + 1] = {0};
 
+			// Obtain CPU0 mutex
+			pthread_mutex_lock(cpu0_mutex);
+
 			// All general purpose registers in host byte order as chars
 			for(size_t i = 0; i < 32; i++)
 			{
@@ -194,6 +197,9 @@ void gdbstub_thread_gdb()
 			uint32_t pc = htonl(cpu0->pc);
 			snprintf(resp + 32 * 8, 9, "%08x", pc);
 
+			// Let go of CPU0 mutex
+			pthread_mutex_unlock(cpu0_mutex);
+
 			// Final packet size, send packet
 			size_t size = 32 * 8 + 8;
 			gdbstub_send_packet(resp, size);
@@ -202,6 +208,9 @@ void gdbstub_thread_gdb()
 		{
 			// G : write all registers -> read and set all registers
 
+			// Obtain CPU0 mutex
+			pthread_mutex_lock(cpu0_mutex);
+
 			// All general purpose registers in host byte order as chars
 			for(size_t i = 1; i < 32; i++)
 			{
@@ -218,6 +227,9 @@ void gdbstub_thread_gdb()
 			pc = ntohl(pc);
 			cpu0->pc = pc;
 
+			// Let go of CPU0 Mutex
+			pthread_mutex_unlock(cpu0_mutex);
+
 			gdbstub_send_packet("OK", 2);
 		}
 		else if(packet[0] == 'm')