[kernel] Improve process init

Move process init from each process needing a main.s with _start to
crt0.s in libc. Also change to a sysv-like initial stack with a
j6-specific array of initialization values after the program arguments.

modules.yaml

@@ -84,7 +84,6 @@ modules:
         source:
             - src/drivers/nulldrv/io.cpp
             - src/drivers/nulldrv/main.cpp
-            - src/drivers/nulldrv/main.s
             - src/drivers/nulldrv/serial.cpp
 
     fb:
@@ -95,7 +94,6 @@ modules:
           - libc
         source:
             - src/drivers/fb/main.cpp
-            - src/drivers/fb/main.s
 
     kutil:
         kind: lib
@@ -132,6 +130,8 @@ modules:
               #- LACKS_TIME_H
         source:
             - src/libraries/libc/arch/x86_64/_Exit.s
+            - src/libraries/libc/arch/x86_64/crt0.s
+            - src/libraries/libc/arch/x86_64/init_libc.c
             - src/libraries/libc/arch/x86_64/syscalls.s
             - src/libraries/libc/ctype/isalnum.c
             - src/libraries/libc/ctype/isalpha.c

src/drivers/fb/main.cpp

@@ -1,25 +1,16 @@
 #include <stdint.h>
 #include <stdlib.h>
 
-#include "j6/types.h"
+#include "j6/init.h"
 #include "j6/errors.h"
 #include "j6/signals.h"
+#include "j6/types.h"
 
 #include <j6libc/syscalls.h>
 
 extern "C" {
-	void _init_libc(j6_process_init *);
 	int main(int, const char **);
-}
+	void _get_init(size_t *initc, struct j6_init_value **initv);
-
-j6_handle_t sys = j6_handle_invalid;
-size_t size = 0;
-
-void
-_init_libc(j6_process_init *init)
-{
-	sys = init->handles[0];
-	size = reinterpret_cast<size_t>(init->handles[1]);
 }
 
 int
@@ -27,12 +18,25 @@ main(int argc, const char **argv)
 {
 	_syscall_system_log("fb driver starting");
 
-	if (size == 0)
+	size_t initc = 0;
+	j6_init_value *initv = nullptr;
+	_get_init(&initc, &initv);
+
+	j6_init_framebuffer *fb = nullptr;
+	for (unsigned i = 0; i < initc; ++i) {
+		if (initv[i].type == j6_init_desc_framebuffer) {
+			fb = reinterpret_cast<j6_init_framebuffer*>(initv[i].value);
+			break;
+		}
+	}
+
+	if (!fb)
 		return 1;
 
-	uint32_t *fb = reinterpret_cast<uint32_t*>(0x100000000);
+	uint32_t *fbp = reinterpret_cast<uint32_t*>(fb->addr);
+	size_t size = fb->size;
 	for (size_t i=0; i < size/4; ++i) {
-		fb[i] = 0xff;
+		fbp[i] = 0xff;
 	}
 
 	_syscall_system_log("fb driver done, exiting");

src/drivers/nulldrv/main.cpp

@@ -11,7 +11,7 @@
 #include "serial.h"
 
 char inbuf[1024];
-j6_handle_t sys = j6_handle_invalid;
+extern j6_handle_t __handle_sys;
 j6_handle_t endp = j6_handle_invalid;
 
 extern "C" {
@@ -51,12 +51,6 @@ thread_proc()
 	_syscall_thread_exit(0);
 }
 
-void
-_init_libc(j6_process_init *init)
-{
-	sys = init->handles[0];
-}
-
 int
 main(int argc, const char **argv)
 {
@@ -65,6 +59,9 @@ main(int argc, const char **argv)
 
 	_syscall_system_log("main thread starting");
 
+	for (int i = 0; i < argc; ++i)
+		_syscall_system_log(argv[i]);
+
 	void *base = malloc(0x1000);
 	if (!base)
 		return 1;
@@ -97,7 +94,7 @@ main(int argc, const char **argv)
 	if (tag != 17)
 		_syscall_system_log("GOT WRONG TAG FROM SENDRECV");
 
-	result = _syscall_system_bind_irq(sys, endp, 3);
+	result = _syscall_system_bind_irq(__handle_sys, endp, 3);
 	if (result != j6_status_ok)
 		return result;
 

src/drivers/nulldrv/main.s

@@ -1,24 +0,0 @@
-section .bss
-mymessage:
-	resq 1024
-
-extern main
-extern _init_libc
-extern exit
-
-section .text
-
-global _start
-_start:
-	mov rbp, rsp
-
-	mov rdi, rsp
-	call _init_libc
-
-	mov rdi, 0
-	mov rsi, 0
-
-	call main
-
-	mov rdi, rax
-	call exit

src/include/j6/init.h

@@ -0,0 +1,30 @@
+#pragma once
+/// \file init.h
+/// Types used in process and thread initialization
+
+#include <stdint.h>
+
+enum j6_init_type {					// `value` is a:
+	j6_init_handle_system,			// Handle to the system
+	j6_init_handle_process,			// Handle to this process
+	j6_init_handle_thread,			// Handle to this thread
+	j6_init_handle_space,			// Handle to this process' address space
+	j6_init_desc_framebuffer		// Pointer to a j6_init_framebuffer descriptor
+};
+
+struct j6_init_value {
+	enum j6_init_type type;
+	uint64_t value;
+};
+
+/// Structure defining a framebuffer.
+/// `flags` has the following bits:
+///   0-3:   Pixel layout. 0000: bgr8, 0001: rgb8
+struct j6_init_framebuffer {
+	void* addr;
+	size_t size;
+	uint32_t vertical;
+	uint32_t horizontal;
+	uint32_t scanline;
+	uint32_t flags;
+};

src/kernel/scheduler.cpp

@@ -1,5 +1,7 @@
 #include <stddef.h>
 
+#include <j6/init.h>
+
 #include "apic.h"
 #include "clock.h"
 #include "console.h"
@@ -63,6 +65,14 @@ scheduler::scheduler(lapic *apic) :
 	bsp_cpu_data.t = idle;
 }
 
+template <typename T>
+inline T * push(uintptr_t &rsp, size_t size = sizeof(T)) {
+	rsp -= size;
+	T *p = reinterpret_cast<T*>(rsp);
+	rsp &= ~(sizeof(uint64_t)-1); // Align the stack
+	return p;
+}
+
 uintptr_t
 load_process_image(uintptr_t phys, uintptr_t virt, size_t bytes, TCB *tcb)
 {
@@ -72,31 +82,60 @@ load_process_image(uintptr_t phys, uintptr_t virt, size_t bytes, TCB *tcb)
 	// We're now in the process space for this process, allocate memory for the
 	// process code and load it
 	process &proc = process::current();
+	thread &th = thread::current();
 	vm_space &space = proc.space();
 
 	vm_area *vma = new vm_area_open(bytes, space, vm_flags::zero|vm_flags::write);
 	space.add(virt, vma);
 	vma->commit(phys, 0, memory::page_count(bytes));
 
-	tcb->rsp3 -= 2 * sizeof(uint64_t);
+	// double zero stack sentinel
-	uint64_t *sentinel = reinterpret_cast<uint64_t*>(tcb->rsp3);
+	*push<uint64_t>(tcb->rsp3) = 0;
-	sentinel[0] = sentinel[1] = 0;
+	*push<uint64_t>(tcb->rsp3) = 0;
 
-	tcb->rsp3 -= sizeof(j6_process_init);
+	const char message[] = "Hello from the kernel!";
-	j6_process_init *init = reinterpret_cast<j6_process_init*>(tcb->rsp3);
+	char *message_arg = push<char>(tcb->rsp3, sizeof(message));
+	kutil::memcpy(message_arg, message, sizeof(message));
 
-	init->process = proc.add_handle(&proc);
+	j6_init_framebuffer *fb_desc = push<j6_init_framebuffer>(tcb->rsp3);
-	init->handles[0] = proc.add_handle(system::get());
+	fb_desc->addr = reinterpret_cast<void*>(0x100000000);
-	init->handles[1] = j6_handle_invalid;
+	fb_desc->size = fb_size;
-	init->handles[2] = j6_handle_invalid;
+
+	j6_init_value *initv = push<j6_init_value>(tcb->rsp3);
+	initv->type = j6_init_handle_system;
+	initv->value = static_cast<uint64_t>(proc.add_handle(system::get()));
+
+	initv = push<j6_init_value>(tcb->rsp3);
+	initv->type = j6_init_handle_process;
+	initv->value = static_cast<uint64_t>(proc.add_handle(&proc));
+
+	initv = push<j6_init_value>(tcb->rsp3);
+	initv->type = j6_init_handle_thread;
+	initv->value = static_cast<uint64_t>(proc.add_handle(&th));
+
+	initv = push<j6_init_value>(tcb->rsp3);
+	initv->type = j6_init_handle_space;
+	//initv->value = static_cast<uint64_t>(proc.add_handle(&space));
+
+	initv = push<j6_init_value>(tcb->rsp3);
+	initv->type = j6_init_desc_framebuffer;
+	initv->value = reinterpret_cast<uint64_t>(fb_desc);
+
+	uint64_t *initc = push<uint64_t>(tcb->rsp3);
+	*initc = 5;
+
+	char **argv0 = push<char*>(tcb->rsp3);
+	*argv0 = message_arg;
+
+	uint64_t *argc = push<uint64_t>(tcb->rsp3);
+	*argc = 1;
 
 	// Crazypants framebuffer part
-	init->handles[1] = reinterpret_cast<j6_handle_t>(fb_size);
 	vma = new vm_area_open(fb_size, space, vm_flags::write|vm_flags::mmio);
 	space.add(0x100000000, vma);
 	vma->commit(fb_loc, 0, memory::page_count(fb_size));
 
-	thread::current().clear_state(thread::state::loading);
+	th.clear_state(thread::state::loading);
 	return tcb->rsp3;
 }
 

src/libraries/libc/arch/x86_64/crt0.s

@@ -1,24 +1,19 @@
-section .bss
-mymessage:
-	resq 1024
-
 extern main
-extern _init_libc
 extern exit
+extern _init_libc
 
-section .text
+global _start:function (_start.end - _start)
-
-global _start
 _start:
 	mov rbp, rsp
-
 	mov rdi, rsp
+
 	call _init_libc
 
-	mov rdi, 0
+	pop rdi
-	mov rsi, 0
+	mov rsi, rsp
 
 	call main
 
 	mov rdi, rax
 	call exit
+.end:

src/libraries/libc/arch/x86_64/init_libc.c

@@ -0,0 +1,36 @@
+#include <stdint.h>
+#include <j6/init.h>
+#include <j6/types.h>
+
+static size_t __initc = 0;
+static struct j6_init_value *__initv = 0;
+
+j6_handle_t __handle_sys = j6_handle_invalid;
+
+void
+_get_init(size_t *initc, struct j6_init_value **initv)
+{
+	if (!initc)
+		return;
+
+	*initc = __initc;
+	if (initv)
+		*initv = __initv;
+}
+
+void
+_init_libc(uint64_t *rsp)
+{
+	uint64_t argc = *rsp++;
+	rsp += argc;
+
+	__initc = *rsp++;
+	__initv = (struct j6_init_value *)rsp;
+
+	for (unsigned i = 0; i < __initc; ++i) {
+		if (__initv[i].type == j6_init_handle_system) {
+			__handle_sys = __initv[i].value;
+			break;
+		}
+	}
+}