From 5b020b0444e4167727d17b475f870de1bc7a49c9 Mon Sep 17 00:00:00 2001
From: vhaudiquet <vhaudiquet343@hotmail.fr>
Date: Thu, 5 Oct 2023 23:04:59 +0200
Subject: [PATCH] Added mock gdbstub implementation

---
 src/gdbstub/gdbstub.c | 71 +++++++++++++++++++++++++++++++++++++++++++
 src/gdbstub/gdbstub.h |  7 +++++
 src/main.c            |  7 +++++
 src/option.c          | 14 ++++++++-
 src/vriscv.h          |  1 +
 5 files changed, 99 insertions(+), 1 deletion(-)
 create mode 100644 src/gdbstub/gdbstub.c
 create mode 100644 src/gdbstub/gdbstub.h

diff --git a/src/gdbstub/gdbstub.c b/src/gdbstub/gdbstub.c
new file mode 100644
index 0000000..5e9cfbe
--- /dev/null
+++ b/src/gdbstub/gdbstub.c
@@ -0,0 +1,71 @@
+#include "gdbstub.h"
+
+#include <errno.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+/* Sockets */
+#include <sys/types.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#define INVALID_SOCKET -1
+#define SOCKET_ERROR -1
+typedef int socket_t;
+typedef struct sockaddr_in sockaddr_in_t;
+typedef struct sockaddr sockaddr_t;
+
+#define GDBSTUB_PORT 1234
+
+socket_t gdbstub_server_socket;
+socket_t gdb_socket;
+
+/*
+* Starts a server that will listen for GDB connections
+*/
+void gdbstub_start()
+{
+    socket_t sock = socket(AF_INET, SOCK_STREAM, 0);
+    if(sock == INVALID_SOCKET)
+    {
+        fprintf(stderr, "Could not create gdbstub server socket: %s\n", strerror(errno));
+        exit(EXIT_FAILURE);
+    }
+    sockaddr_in_t sin = {0};
+    sin.sin_addr.s_addr = htonl(INADDR_ANY);
+    sin.sin_family = AF_INET;
+    sin.sin_port = htons(GDBSTUB_PORT);
+
+    if(bind(sock, (sockaddr_t*) &sin, sizeof(sin)) == SOCKET_ERROR)
+    {
+        fprintf(stderr, "Could not bind gdbstub server socket: %s\n", strerror(errno));
+        exit(EXIT_FAILURE);
+    }
+
+    if(listen(sock, 1) == SOCKET_ERROR)
+    {
+        fprintf(stderr, "Could not listen gdbstub server socket: %s\n", strerror(errno));
+        exit(EXIT_FAILURE);
+    }
+
+    gdbstub_server_socket = sock;
+}
+
+/*
+* Wait for a client (gdb) to connect to this server
+*/
+void gdbstub_wait_for_connection()
+{
+    sockaddr_in_t csin = {0};
+    socket_t c_socket;
+    socklen_t sinsize = sizeof(csin);
+
+    c_socket = accept(gdbstub_server_socket, (sockaddr_t*) &csin, &sinsize);
+    if(c_socket == INVALID_SOCKET)
+    {
+        fprintf(stderr, "Could not accept client on gdbstub server: %s\n", strerror(errno));
+        exit(EXIT_FAILURE);
+    }
+
+    gdb_socket = c_socket;
+}
diff --git a/src/gdbstub/gdbstub.h b/src/gdbstub/gdbstub.h
new file mode 100644
index 0000000..5a56014
--- /dev/null
+++ b/src/gdbstub/gdbstub.h
@@ -0,0 +1,7 @@
+#ifndef GDBSTUB_H
+#define GDBSTUB_H
+
+void gdbstub_start();
+void gdbstub_wait_for_connection();
+
+#endif
diff --git a/src/main.c b/src/main.c
index 2bf27ad..b275777 100644
--- a/src/main.c
+++ b/src/main.c
@@ -2,6 +2,7 @@
 #include "memory/memory.h"
 #include "bootloader/bootloader.h"
 #include "cpu/rv32cpu.h"
+#include "gdbstub/gdbstub.h"
 
 char* CURRENT_NAME;
 
@@ -20,6 +21,12 @@ int main(int argc, char** argv)
     cpu_init();
     cpu0->pc = entry_point;
 
+    if(gdbstub)
+    {
+        gdbstub_start();
+        gdbstub_wait_for_connection();
+    }
+
     // CPU simulation
     cpu_loop(cpu0);
     
diff --git a/src/option.c b/src/option.c
index 0a6e896..7c36ed8 100644
--- a/src/option.c
+++ b/src/option.c
@@ -7,6 +7,7 @@
 
 uint64_t memory_size = 512 * 1024 * 1024;
 char* file_path;
+bool gdbstub = false;
 
 static void print_usage();
 static void print_help();
@@ -94,6 +95,11 @@ void parse_options(int argc, char** argv)
 
 					break;
 				}
+				case 's':
+				{
+					gdbstub = true;
+					break;
+				}
 				default:
 				{
 					fprintf(stderr, "Error: Unknown short option -%c\n", argv[i][k]);
@@ -150,6 +156,11 @@ static int parse_long_option(char* str, char* argq)
 
 		return 1;
 	}
+	else if(strcmp(str, "gdb-stub") == 0)
+	{
+		gdbstub = true;
+		return 0;
+	}
 	else
 	{
 		fprintf(stderr, "Error: Unknown long option " OPTION_SEPARATOR OPTION_SEPARATOR "%s\n", str);
@@ -169,7 +180,8 @@ static void print_help()
 	printf("Options:\n");
 	printf("  " OPTION_SEPARATOR "h, " OPTION_SEPARATOR "?, --help\t\tPrint this help message\n");
 	printf("  " OPTION_SEPARATOR "v, --version\t\t\tPrint version information\n");
-	printf("  " OPTION_SEPARATOR "m, --memory\t\t\tSet the simulated memory size, in MiB\n");
+	printf("  " OPTION_SEPARATOR "m, --memory\t\t\tSet the simulated memory size, in MiB (max 4096)\n");
+	printf("  " OPTION_SEPARATOR "s, --gdb-stub\t\t\tLaunch a gdb stub server, for remote gdb debugging\n");
 }
 
 static void print_version()
diff --git a/src/vriscv.h b/src/vriscv.h
index 4009074..b34c4b7 100644
--- a/src/vriscv.h
+++ b/src/vriscv.h
@@ -14,6 +14,7 @@ extern char* CURRENT_NAME;
 /* Program options */
 extern size_t memory_size;
 extern char* file_path;
+extern bool gdbstub;
 void parse_options(int argc, char** argv);
 
 #endif