From 1f3cdd951347bc5a73ca4a4c3418aad998267bb4 Mon Sep 17 00:00:00 2001
From: Rekai Musuka <rekai@musuka.dev>
Date: Thu, 15 Dec 2022 19:37:38 -0400
Subject: [PATCH] feat: add gdb support to zba

---
 lib/zba-gdbstub  |  2 +-
 src/core/emu.zig | 56 ++++++++++++++++++++++++++++++++++++++++++++++++
 src/main.zig     | 34 ++++++++++++++++++++++++++---
 3 files changed, 88 insertions(+), 4 deletions(-)

diff --git a/lib/zba-gdbstub b/lib/zba-gdbstub
index 08bf0f9..4bca44e 160000
--- a/lib/zba-gdbstub
+++ b/lib/zba-gdbstub
@@ -1 +1 @@
-Subproject commit 08bf0f9201a0cd6d317e3f73a26d245eedfd1121
+Subproject commit 4bca44e5f2a4aa19361b51b7617a21f46f88eef4
diff --git a/src/core/emu.zig b/src/core/emu.zig
index 1d97864..ece7e58 100644
--- a/src/core/emu.zig
+++ b/src/core/emu.zig
@@ -162,3 +162,59 @@ fn sleep(timer: *Timer, wake_time: u64) ?u64 {
 fn spinLoop(timer: *Timer, wake_time: u64) void {
     while (true) if (timer.read() > wake_time) break;
 }
+
+pub const EmuThing = struct {
+    const Self = @This();
+    const Interface = @import("gdbstub").Emulator;
+
+    cpu: *Arm7tdmi,
+    scheduler: *Scheduler,
+
+    pub fn init(cpu: *Arm7tdmi, scheduler: *Scheduler) Self {
+        return .{ .cpu = cpu, .scheduler = scheduler };
+    }
+
+    pub fn interface(self: *Self) Interface {
+        return Interface.init(self);
+    }
+
+    pub fn read(self: *const Self, addr: u32) u8 {
+        return self.cpu.bus.dbgRead(u8, addr);
+    }
+
+    pub fn write(self: *Self, addr: u32, value: u8) void {
+        _ = value;
+        _ = self;
+        _ = addr;
+
+        std.debug.panic("TODO: Implement Debug Writes?", .{});
+    }
+
+    pub fn registers(self: *const Self) *[16]u32 {
+        return &self.cpu.r;
+    }
+
+    pub fn cpsr(self: *const Self) u32 {
+        return self.cpu.cpsr.raw;
+    }
+
+    pub fn step(self: *Self) void {
+        const cpu = self.cpu;
+        const sched = self.scheduler;
+
+        // TODO: How can I make it easier to keep this in lock-step with runFrame?
+        while (true) {
+            if (!cpu.stepDmaTransfer()) {
+                if (cpu.isHalted()) {
+                    // Fast-forward to next Event
+                    sched.tick = sched.queue.peek().?.tick;
+                } else {
+                    cpu.step();
+                    break; // this function won't return until we've actually stepped once
+                }
+            }
+
+            if (sched.tick >= sched.nextTimestamp()) sched.handleEvent(cpu);
+        }
+    }
+};
diff --git a/src/main.zig b/src/main.zig
index 463f388..cc89a24 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -22,6 +22,7 @@ const params = clap.parseParamsComptime(
     \\-h, --help            Display this help and exit.
     \\-s, --skip            Skip BIOS.
     \\-b, --bios <str>      Optional path to a GBA BIOS ROM.
+    \\ --gdb                Run ZBA from the context of a GDB Server
     \\<str>                 Path to the GBA GamePak ROM.
     \\
 );
@@ -87,10 +88,37 @@ pub fn main() void {
         cpu.fastBoot();
     }
 
-    var gui = Gui.init(&bus.pak.title, &bus.apu, width, height) catch |e| exitln("failed to init gui: {}", .{e});
-    defer gui.deinit();
+    if (result.args.gdb) {
+        const Server = @import("gdbstub").Server;
+        const EmuThing = @import("core/emu.zig").EmuThing;
 
-    gui.run(&cpu, &scheduler) catch |e| exitln("failed to run gui thread: {}", .{e});
+        var emu_thing = EmuThing.init(&cpu, &scheduler);
+        const emulator = emu_thing.interface();
+
+        {
+            const frames_per_second: usize = 60;
+            const emu = @import("core/emu.zig");
+
+            var i: usize = 0;
+            while (i < frames_per_second * 120) : (i += 1) {
+                emu.runFrame(&scheduler, &cpu);
+
+                std.debug.print("Frame {:0>3}/{:0>3}\r", .{ i, frames_per_second * 120 });
+            }
+        }
+
+        log.info("Ready to connect", .{});
+
+        var server = Server.init(emulator) catch |e| exitln("failed to init gdb server: {}", .{e});
+        defer server.deinit(allocator);
+
+        server.run(allocator) catch |e| exitln("gdb server crashed: {}", .{e});
+    } else {
+        var gui = Gui.init(&bus.pak.title, &bus.apu, width, height) catch |e| exitln("failed to init gui: {}", .{e});
+        defer gui.deinit();
+
+        gui.run(&cpu, &scheduler) catch |e| exitln("failed to run gui thread: {}", .{e});
+    }
 }
 
 fn handleArguments(allocator: Allocator, data_path: []const u8, result: *const clap.Result(clap.Help, &params, clap.parsers.default)) !FilePaths {