[kernel] Add channel objects

Add the channel object for sending messages between threads. Currently
no good of passing channels to other threads, but global variables in a
single process work. Currently channels are slow and do double copies,
need to refine more.

Tags: ipc

modules.yaml

@@ -37,7 +37,7 @@ modules:
             - src/kernel/main.cpp
             - src/kernel/memory_bootstrap.cpp
             - src/kernel/msr.cpp
-            - src/kernel/objects/handle.cpp
+            - src/kernel/objects/channel.cpp
             - src/kernel/objects/kobject.cpp
             - src/kernel/objects/thread.cpp
             - src/kernel/objects/process.cpp
@@ -48,6 +48,7 @@ modules:
             - src/kernel/serial.cpp
             - src/kernel/syscall.cpp
             - src/kernel/syscall.s
+            - src/kernel/syscalls/channel.cpp
             - src/kernel/syscalls/object.cpp
             - src/kernel/syscalls/process.cpp
             - src/kernel/syscalls/system.cpp

src/drivers/nulldrv/main.cpp

@@ -5,6 +5,10 @@
 #include "j6/errors.h"
 #include "j6/signals.h"
 
+const char message[] = "Hello! This is a message being sent over a channel!";
+char inbuf[1024];
+j6_handle_t chan = j6_handle_invalid;
+
 extern "C" {
 	j6_status_t system_log(const char *msg);
 
@@ -17,6 +21,11 @@ extern "C" {
 	j6_status_t thread_sleep(uint64_t til);
 	j6_status_t thread_exit(int64_t status);
 
+	j6_status_t channel_create(j6_handle_t *handle);
+	j6_status_t channel_close(j6_handle_t handle);
+	j6_status_t channel_send(j6_handle_t handle, size_t len, void *data);
+	j6_status_t channel_receive(j6_handle_t handle, size_t *len, void *data);
+
 	int main(int, const char **);
 }
 
@@ -24,6 +33,13 @@ void
 thread_proc()
 {
 	system_log("sub thread starting");
+
+	j6_status_t result = channel_send(chan, sizeof(message), (void*)message);
+	if (result != j6_status_ok)
+		thread_exit(result);
+
+	system_log("sub thread sent on channel");
+
 	for (int i = 1; i < 5; ++i)
 		thread_sleep(i*10);
 
@@ -34,21 +50,49 @@ thread_proc()
 int
 main(int argc, const char **argv)
 {
-	j6_handle_t child = 0;
+	j6_handle_t child = j6_handle_invalid;
 	j6_signal_t out = 0;
 
 	system_log("main thread starting");
 
-	j6_status_t result = thread_create(&thread_proc, &child);
+	j6_status_t result = channel_create(&chan);
 	if (result != j6_status_ok)
 		return result;
 
+	system_log("main thread created channel");
+
+	result = thread_create(&thread_proc, &child);
+	if (result != j6_status_ok)
+		return result;
+
+	result = object_wait(chan, j6_signal_channel_can_recv, &out);
+	if (result != j6_status_ok)
+		return result;
+
+	size_t len = sizeof(inbuf);
+	result = channel_receive(chan, &len, (void*)inbuf);
+	if (result != j6_status_ok)
+		return result;
+
+	for (int i = 0; i < sizeof(message); ++i) {
+		if (inbuf[i] != message[i])
+			return 127;
+	}
+
+	system_log("main thread received on channel");
+
 	system_log("main thread waiting on child");
 
 	result = object_wait(child, -1ull, &out);
 	if (result != j6_status_ok)
 		return result;
 
+	result = channel_close(chan);
+	if (result != j6_status_ok)
+		return result;
+
+	system_log("main thread closed channel");
+
 	system_log("main thread done, exiting");
 	return 0;
 }

src/drivers/nulldrv/main.s

@@ -30,6 +30,10 @@ SYSCALL thread_create, 0x19
 SYSCALL thread_exit, 0x1a
 SYSCALL thread_pause, 0x1b
 SYSCALL thread_sleep, 0x1c
+SYSCALL channel_create, 0x20
+SYSCALL channel_close, 0x21
+SYSCALL channel_send, 0x22
+SYSCALL channel_receive, 0x23
 
 global _start
 _start:

src/include/j6/errors.h

@@ -8,9 +8,12 @@
 
 #define j6_status_ok				0x0000
 
+#define j6_status_closed			0x1000
 #define j6_status_destroyed			0x1001
 
 #define j6_err_nyi					j6_err(0x0001)
 #define j6_err_unexpected			j6_err(0x0002)
 #define j6_err_invalid_arg			j6_err(0x0003)
+#define j6_err_not_ready			j6_err(0x0004)
+#define j6_err_insufficient			j6_err(0x0005)
 

src/include/j6/signals.h

@@ -13,6 +13,11 @@
 // Thread signals
 #define j6_signal_thread_exit		(1ull << 16)
 
+// Channel signals
+#define j6_signal_channel_closed	(1ull << 16)
+#define j6_signal_channel_can_send	(1ull << 17)
+#define j6_signal_channel_can_recv	(1ull << 18)
+
 // Signals 48-63 are user-defined signals
 #define j6_signal_user0				(1ull << 48)
 #define j6_signal_user1				(1ull << 49)

src/kernel/objects/channel.cpp

@@ -0,0 +1,70 @@
+#include "kutil/assert.h"
+
+#include "objects/channel.h"
+
+channel::channel() :
+	m_len(0),
+	m_capacity(0),
+	m_data(nullptr),
+	kobject(kobject::type::channel, j6_signal_channel_can_send)
+{
+}
+
+channel::~channel()
+{
+	kutil::kfree(m_data);
+}
+
+j6_status_t
+channel::enqueue(size_t len, void *data)
+{
+	// TODO: Make this thread safe!
+	if (closed())
+		return j6_status_closed;
+
+	if (!can_send())
+		return j6_err_not_ready;
+
+	if (m_capacity < len) {
+		kutil::kfree(m_data);
+		m_data = kutil::kalloc(len);
+		m_capacity = len;
+		kassert(m_data, "Failed to allocate memory to copy channel message");
+	}
+
+	m_len = len;
+	kutil::memcpy(m_data, data, len);
+	assert_signal(j6_signal_channel_can_recv);
+
+	return j6_status_ok;
+}
+
+j6_status_t
+channel::dequeue(size_t *len, void *data)
+{
+	// TODO: Make this thread safe!
+	if (closed())
+		return j6_status_closed;
+
+	if (!can_receive())
+		return j6_err_not_ready;
+
+	if (!len)
+		return j6_err_invalid_arg;
+
+	if (*len < m_len)
+		return j6_err_insufficient;
+
+	kutil::memcpy(data, m_data, m_len);
+	*len = m_len;
+	assert_signal(j6_signal_channel_can_send);
+
+	return j6_status_ok;
+}
+
+void
+channel::on_no_handles()
+{
+	kobject::on_no_handles();
+	delete this;
+}

src/kernel/objects/channel.h

@@ -0,0 +1,49 @@
+#pragma once
+/// \file channel.h
+/// Definition of channel objects and related functions
+
+#include "j6/signals.h"
+#include "objects/kobject.h"
+
+/// Channels are bi-directional means of sending messages
+class channel :
+	public kobject
+{
+public:
+	channel();
+	virtual ~channel();
+
+	/// Check if the channel has space for a message to be sent
+	inline bool can_send() const { return check_signal(j6_signal_channel_can_send); }
+
+	/// Check if the channel has a message wiating already
+	inline bool can_receive() const { return check_signal(j6_signal_channel_can_recv); }
+
+	/// Put a message into the channel
+	/// \arg len  Length of data, in bytes
+	/// \arg data Pointer to the message data
+	/// \returns  j6_status_ok on success
+	j6_status_t enqueue(size_t len, void *data);
+
+	/// Get a message from the channel, copied into a provided buffer
+	/// \arg len  On input, the size of the provided buffer. On output,
+	///           the size of the message copied into the buffer.
+	/// \arg data Pointer to the buffer
+	/// \returns  j6_status_ok on success
+	j6_status_t dequeue(size_t *len, void *data);
+
+	/// Mark this channel as closed, all future calls to enqueue or
+	/// dequeue messages will fail with j6_status_closed.
+	inline void close() { assert_signal(j6_signal_channel_closed); }
+
+	/// Check if this channel has been closed
+	inline bool closed() { return check_signal(j6_signal_channel_closed); }
+
+protected:
+	virtual void on_no_handles() override;
+
+private:
+	size_t m_len;
+	size_t m_capacity;
+	void *m_data;
+};

src/kernel/objects/kobject.h

@@ -19,6 +19,7 @@ public:
 
 		event,
 		eventpair,
+		channel,
 
 		vms,
 		vmo,
@@ -55,6 +56,10 @@ public:
 	/// \arg s  The set of signals to deassert
 	void deassert_signal(j6_signal_t s);
 
+	/// Check if the given signals are set on this object
+	/// \arg s  The set of signals to check
+	inline bool check_signal(j6_signal_t s) const { return (m_signals & s) == s; }
+
 	/// Increment the handle refcount
 	inline void handle_retain() { ++m_handle_count; }
 

src/kernel/syscalls.inc

@@ -12,3 +12,7 @@ SYSCALL(0x1a, thread_exit,      int64_t)
 SYSCALL(0x1b, thread_pause,     void)
 SYSCALL(0x1c, thread_sleep,     uint64_t)
 
+SYSCALL(0x20, channel_create,   j6_handle_t *)
+SYSCALL(0x21, channel_close,    j6_handle_t)
+SYSCALL(0x22, channel_send,     j6_handle_t, size_t, void *)
+SYSCALL(0x23, channel_receive,  j6_handle_t, size_t *, void *)

src/kernel/syscalls/channel.cpp

@@ -0,0 +1,76 @@
+#include "j6/errors.h"
+#include "j6/types.h"
+
+#include "objects/channel.h"
+#include "objects/thread.h"
+#include "objects/process.h"
+#include "scheduler.h"
+
+namespace syscalls {
+
+j6_status_t
+channel_create(j6_handle_t *handle)
+{
+	scheduler &s = scheduler::get();
+	TCB *tcb = s.current();
+	thread *parent = thread::from_tcb(tcb);
+	process &p = parent->parent();
+
+	channel *c = new channel;
+	*handle = p.add_handle(c);
+
+	return j6_status_ok;
+}
+
+j6_status_t
+channel_close(j6_handle_t handle)
+{
+	scheduler &s = scheduler::get();
+	TCB *tcb = s.current();
+	thread *parent = thread::from_tcb(tcb);
+	process &p = parent->parent();
+
+	kobject *o = p.lookup_handle(handle);
+	if (!o || o->get_type() != kobject::type::channel)
+		return j6_err_invalid_arg;
+
+	p.remove_handle(handle);
+	channel *c = static_cast<channel*>(o);
+	c->close();
+
+	return j6_status_ok;
+}
+
+j6_status_t
+channel_send(j6_handle_t handle, size_t len, void *data)
+{
+	scheduler &s = scheduler::get();
+	TCB *tcb = s.current();
+	thread *parent = thread::from_tcb(tcb);
+	process &p = parent->parent();
+
+	kobject *o = p.lookup_handle(handle);
+	if (!o || o->get_type() != kobject::type::channel)
+		return j6_err_invalid_arg;
+
+	channel *c = static_cast<channel*>(o);
+	return c->enqueue(len, data);
+}
+
+j6_status_t
+channel_receive(j6_handle_t handle, size_t *len, void *data)
+{
+	scheduler &s = scheduler::get();
+	TCB *tcb = s.current();
+	thread *parent = thread::from_tcb(tcb);
+	process &p = parent->parent();
+
+	kobject *o = p.lookup_handle(handle);
+	if (!o || o->get_type() != kobject::type::channel)
+		return j6_err_invalid_arg;
+
+	channel *c = static_cast<channel*>(o);
+	return c->dequeue(len, data);
+}
+
+} // namespace syscalls