[kernel] Make stdout channel available to processes

The "fake" stdout channel is now being passed in the new j6_process_init
structure to processes, and nulldrv now uses it to print a message to
the console.

src/drivers/nulldrv/main.cpp

@@ -7,11 +7,14 @@
 
 #include <j6libc/syscalls.h>
 
-const char message[] = "Hello! This is a message being sent over a channel!";
+const char message[] = "Hello! This is a message being sent over a channel!\n";
 char inbuf[1024];
 j6_handle_t chan = j6_handle_invalid;
 
+j6_process_init *init = nullptr;
+
 extern "C" {
+	void _init_libc(j6_process_init *);
 	int main(int, const char **);
 }
 
@@ -40,6 +43,12 @@ thread_proc()
 	_syscall_thread_exit(0);
 }
 
+void
+_init_libc(j6_process_init *i)
+{
+	init = i;
+}
+
 int
 main(int argc, const char **argv)
 {
@@ -52,6 +61,11 @@ main(int argc, const char **argv)
 	if (result != j6_status_ok)
 		return result;
 
+	size_t size = sizeof(message);
+	result = _syscall_channel_send(init->output, &size, (void*)message);
+	if (result != j6_status_ok)
+		return result;
+
 	_syscall_system_log("main thread created channel");
 
 	result = _syscall_thread_create(reinterpret_cast<void*>(&thread_proc), &child);

src/drivers/nulldrv/main.s

@@ -3,19 +3,22 @@ mymessage:
 	resq 1024
 
 extern main
+extern _init_libc
 extern exit
 
 section .text
 
 global _start
 _start:
-	xor rbp, rbp	; Sentinel rbp
-	push rbp
-	push rbp
 	mov rbp, rsp
 
+	mov rdi, rsp
+	sub rdi, 8
+	call _init_libc
+
 	mov rdi, 0
 	mov rsi, 0
+
 	call main
 
 	mov rdi, rax

src/include/j6/types.h

@@ -20,3 +20,10 @@ typedef uint64_t j6_signal_t;
 typedef uint64_t j6_rights_t;
 
 #define j6_handle_invalid 0xffffffff
+
+/// A process' initial data structure for communicating with the system
+struct j6_process_init
+{
+	j6_handle_t input;
+	j6_handle_t output;
+};

src/kernel/console.cpp

@@ -261,13 +261,18 @@ console::set_color(uint8_t fg, uint8_t bg)
 	}
 }
 
-void
+size_t
 console::puts(const char *message)
 {
-	while (message && *message)
+	size_t n = 0;
+	while (message && *message) {
+		n++;
 		putc(*message++);
 	}
 
+	return n;
+}
+
 void
 console::putc(char c)
 {

src/kernel/console.h

@@ -16,7 +16,7 @@ public:
 	void set_color(uint8_t fg = 7, uint8_t bg = 0);
 
 	void putc(char c);
-	void puts(const char *message);
+	size_t puts(const char *message);
 	void vprintf(const char *fmt, va_list args);
 
 	inline void printf(const char *fmt, ...)

src/kernel/main.cpp

@@ -92,7 +92,13 @@ stdout_task()
 		}
 
 		buffer[n] = 0;
-		cons->puts(reinterpret_cast<const char *>(buffer));
+		const char *s = reinterpret_cast<const char *>(buffer);
+
+		while (n) {
+			size_t r = cons->puts(s);
+			n -= r + 1;
+			s += r + 1;
+		}
 	}
 }
 
@@ -193,6 +199,8 @@ kernel_main(args::header *header)
 	syscall_enable();
 	scheduler *sched = new scheduler(devices.get_lapic());
 
+	std_out = new channel;
+
 	for (auto &ird : initrds) {
 		for (auto &f : ird.files()) {
 			if (f.executable()) {
@@ -203,8 +211,6 @@ kernel_main(args::header *header)
 		}
 	}
 
-	std_out = new channel;
-
 	sched->create_kernel_task(logger_task, scheduler::max_priority-1, true);
 	sched->create_kernel_task(stdout_task, scheduler::max_priority-1, true);
 

src/kernel/scheduler.cpp

@@ -11,6 +11,7 @@
 #include "kernel_memory.h"
 #include "log.h"
 #include "msr.h"
+#include "objects/channel.h"
 #include "objects/process.h"
 #include "page_manager.h"
 #include "scheduler.h"
@@ -18,6 +19,7 @@
 #include "elf/elf.h"
 #include "kutil/assert.h"
 
+
 scheduler *scheduler::s_instance = nullptr;
 
 const uint64_t rflags_noint = 0x002;
@@ -69,6 +71,7 @@ load_process_image(const void *image_start, size_t bytes, TCB *tcb)
 	page_manager *pager = page_manager::get();
 
 	thread *th = thread::from_tcb(tcb);
+	process &proc = th->parent();
 
 	log::debug(logs::loader, "Loading task! ELF: %016lx [%d]", image_start, bytes);
 
@@ -115,6 +118,16 @@ load_process_image(const void *image_start, size_t bytes, TCB *tcb)
 		kutil::memcpy(dest, src, header->size);
 	}
 
+	tcb->rsp3 -= 2 * sizeof(uint64_t);
+	uint64_t *sentinel = reinterpret_cast<uint64_t*>(tcb->rsp3);
+	sentinel[0] = sentinel[1] = 0;
+
+	tcb->rsp3 -= sizeof(j6_process_init);
+	j6_process_init *init = reinterpret_cast<j6_process_init*>(tcb->rsp3);
+
+	extern channel *std_out;
+	init->output = proc.add_handle(std_out);
+
 	th->clear_state(thread::state::loading);
 
 	uintptr_t entrypoint = image.entrypoint();