[kernel] Remove getpid and fork system calls

The getpid and fork system calls were stubbed out previously, this
commit removes them and adds process_koid as a getpid replacement.

src/drivers/nulldrv/main.cpp

@@ -5,8 +5,7 @@
 #include "j6/errors.h"
 
 extern "C" {
-	j6_status_t getpid(uint64_t *);
-	j6_status_t fork(uint64_t *);
+	j6_status_t get_process_koid(j6_koid_t *koid);
 	j6_status_t sleep(uint64_t til);
 	j6_status_t debug();
 	j6_status_t message(const char *msg);
@@ -20,17 +19,14 @@ main(int argc, const char **argv)
 {
 	uint64_t pid = 0;
 	uint64_t child = 0;
+	j6_koid_t process = 0;
 
-	j6_status_t result = fork(&child);
+	j6_status_t result = get_process_koid(&process);
 	if (result != j6_status_ok)
 		return result;
 
 	message("hello from nulldrv!");
 
-	result = getpid(&pid);
-	if (result != j6_status_ok)
-		return result;
-
 	for (int i = 1; i < 5; ++i)
 		sleep(i*10);
 

src/drivers/nulldrv/main.s

@@ -6,13 +6,13 @@ extern main
 extern exit
 
 section .text
-global getpid
-getpid:
+global get_process_koid
+get_process_koid:
 	push rbp
 	mov rbp, rsp
 
 	; address of out var should already be in rdi
-	mov rax, 0x13  ; getpid syscall
+	mov rax, 0x10  ; getpid syscall
 	syscall        ; result is now already in rax, so just return
 
 	pop rbp
@@ -34,32 +34,19 @@ sleep:
 	push rbp
 	mov rbp, rsp
 
-	mov rax, 0x16  ; sleep syscall
+	mov rax, 0x14  ; sleep syscall
 	syscall
 
 	pop rbp
 	ret
 
-global fork
-fork:
-	push rbp
-	mov rbp, rsp
-
-	; address of out var should already be in rdi
-	mov rax, 0x12
-	syscall    ; result left in rax
-
-	pop rbp
-	ret
-	
-
 global message
 message:
 	push rbp
 	mov rbp, rsp
 
 	; message should already be in rdi
-	mov rax, 0x14
+	mov rax, 0x12
 	syscall
 
 	pop rbp