From 980070b204bd35839f90ea0a237699032b1c5261 Mon Sep 17 00:00:00 2001
From: vhaudiquet <vhaudiquet343@hotmail.fr>
Date: Sun, 8 Oct 2023 19:04:25 +0200
Subject: [PATCH] correct ebreak implementation, gdbstub watcher everything in
 gdb should work now :)

---
 src/cpu/rv32cpu.c     | 10 +++++++++-
 src/gdbstub/gdbstub.c | 38 ++++++++++++++++++++++++++++----------
 2 files changed, 37 insertions(+), 11 deletions(-)

diff --git a/src/cpu/rv32cpu.c b/src/cpu/rv32cpu.c
index a85dae9..a1ea41f 100644
--- a/src/cpu/rv32cpu.c
+++ b/src/cpu/rv32cpu.c
@@ -512,7 +512,10 @@ static void cpu_execute(rv32_cpu_t* cpu, instruction_t* instruction)
 							fprintf(stderr, "ECALL: a7(sbi ext id) = %d, a6(sbi funct id) = %d\n", cpu->regs.a7, cpu->regs.a6);
 							break;
 						case IMM_EBREAK:
-							fprintf(stderr, "EBREAK\n");
+							// EBREAK : on debug, give back hand to debugger ; without debug, end simulation
+							// In any way, we set back simulation ticks to 0
+							cpu->sim_ticks_left = 1;
+							cpu->pc -= 4;
 							break;
 						default:
 							fprintf(stderr, "FATAL: Unknown IMM for ECALL/EBREAK instruction while executing (IMM=0x%x)\n", instruction->immediate);
@@ -650,6 +653,11 @@ void cpu_loop(rv32_cpu_t* cpu)
 	{
 		// Aquire CPU and memory mutex
 		pthread_mutex_lock(&cpu0_mutex);
+
+		// No simulation ticks left : wakeup people waiting on sim end
+		if(!cpu->sim_ticks_left)
+			pthread_cond_signal(&cpu0->sim_condition);
+		// Then, wait for simulation state to change until we get more ticks to simulate
 		while(!cpu->sim_ticks_left)
 			pthread_cond_wait(&cpu0->sim_condition, &cpu0_mutex);
 
diff --git a/src/gdbstub/gdbstub.c b/src/gdbstub/gdbstub.c
index d556dd2..337eeac 100644
--- a/src/gdbstub/gdbstub.c
+++ b/src/gdbstub/gdbstub.c
@@ -25,10 +25,13 @@ typedef struct sockaddr sockaddr_t;
 socket_t gdbstub_server_socket;
 socket_t gdb_socket;
 pthread_t gdbstub_thread;
+pthread_t gdbstub_watcher_thread;
 
 void gdbstub_thread_gdb();
+void gdbstub_cpu_watcher_thread();
 static void gdbstub_handle_ctrlc();
 
+
 /*
  * Receive a packet from client gdb
  * Ignores the ACK on the way, and only returns the packet (not initial '$' symbol)
@@ -161,6 +164,7 @@ void gdbstub_wait_for_connection()
 	gdb_socket = c_socket;
 
 	pthread_create(&gdbstub_thread, 0, (void*) gdbstub_thread_gdb, 0);
+	pthread_create(&gdbstub_watcher_thread, 0, (void*) gdbstub_cpu_watcher_thread, 0);
 }
 
 void gdbstub_thread_gdb()
@@ -286,12 +290,14 @@ void gdbstub_thread_gdb()
 		{
 			// s : single-step
 
-			// TODO : Implement that correctly
+			// Send an ACK
+			send(gdb_socket, "+", 1, 0);
 
-			// Send back halt reason
-			// Halt Reason : Signal 05 (SIGTRAP)
-			char* resp = "S05";
-			gdbstub_send_packet(resp, 3);
+			// Continue simulation, for 1 tick
+			pthread_mutex_lock(&cpu0_mutex);
+			cpu0->sim_ticks_left = 1;
+			pthread_mutex_unlock(&cpu0_mutex);
+			pthread_cond_signal(&cpu0->sim_condition);
 		}
 		else if(packet[0] == 'c')
 		{
@@ -310,6 +316,23 @@ void gdbstub_thread_gdb()
 	}
 }
 
+void gdbstub_cpu_watcher_thread()
+{
+	while(1)
+	{
+		pthread_mutex_lock(&cpu0_mutex);
+		pthread_cond_wait(&cpu0->sim_condition, &cpu0_mutex);
+		if(!cpu0->sim_ticks_left && cpu0->sim_ticks_done > 0)
+		{
+			// Send back halt reason
+			// Halt Reason : Signal 05 (SIGTRAP)
+			char* resp = "S05";
+			gdbstub_send_packet(resp, 3);
+		}
+		pthread_mutex_unlock(&cpu0_mutex);
+	}
+}
+
 /*
  * Handles the GDB CTRL+C (^C) command, that
  * should interrupt the simulation
@@ -320,9 +343,4 @@ static void gdbstub_handle_ctrlc()
 	pthread_mutex_lock(&cpu0_mutex);
 	cpu0->sim_ticks_left = 0;
 	pthread_mutex_unlock(&cpu0_mutex);
-
-	// Send back halt signal to gdb
-	// Halt Reason : Signal 05 (SIGTRAP)
-	char* resp = "S05";
-	gdbstub_send_packet(resp, 3);
 }