From b9f5f92bff69059471a76e73539780eedb356455 Mon Sep 17 00:00:00 2001
From: dzwdz
Date: Mon, 25 Dec 2023 19:08:04 +0100
Subject: kernel: _sys_getnull()  (basically /dev/null)

---
 src/kernel/handle.h   |  1 +
 src/kernel/syscalls.c | 22 ++++++++++++++++++++--
 2 files changed, 21 insertions(+), 2 deletions(-)

(limited to 'src/kernel')

diff --git a/src/kernel/handle.h b/src/kernel/handle.h
index 21b4364..d502d5d 100644
--- a/src/kernel/handle.h
+++ b/src/kernel/handle.h
@@ -10,6 +10,7 @@ enum handle_type {
 	HANDLE_PIPE,
 	HANDLE_FS_FRONT,
 	HANDLE_FS_REQ,
+	HANDLE_NULL,
 };
 
 struct Handle {
diff --git a/src/kernel/syscalls.c b/src/kernel/syscalls.c
index e449953..5f53ccb 100644
--- a/src/kernel/syscalls.c
+++ b/src/kernel/syscalls.c
@@ -166,7 +166,13 @@ static long simple_vfsop(
 		|| vfsop == VFSOP_WRITE
 		|| vfsop == VFSOP_GETSIZE);
 	Handle *h = proc_handle_get(proc_cur, hid);
-	if (!h) SYSCALL_RETURN(-EBADF);
+	if (!h) {
+		SYSCALL_RETURN(-EBADF);
+	}
+	if (h->type != HANDLE_FILE && h->type != HANDLE_PIPE) {
+		SYSCALL_RETURN(-ENOSYS);
+	}
+
 	// TODO those checks really need some comprehensive tests
 	if (vfsop == VFSOP_READ && !h->readable)
 		SYSCALL_RETURN(-EACCES);
@@ -196,7 +202,9 @@ static long simple_vfsop(
 			/* already checked if this is the correct pipe end */
 			pipe_joinqueue(h, proc_cur, buf, len);
 		} else SYSCALL_RETURN(-ENOSYS);
-	} else SYSCALL_RETURN(-ENOSYS);
+	} else {
+		panic_invalid_state();
+	}
 	return 0;
 }
 
@@ -436,6 +444,15 @@ uint64_t _sys_time(int flags) {
 	SYSCALL_RETURN(now - proc_cur->basetime);
 }
 
+hid_t _sys_getnull(int flags) {
+	if (flags != 0) {
+		SYSCALL_RETURN(-ENOSYS);
+	}
+
+	hid_t hid = proc_handle_init(proc_cur, HANDLE_NULL, NULL);
+	SYSCALL_RETURN((0 <= hid) ? hid : -EMFILE);
+}
+
 long _sys_execbuf(void __user *ubuf, size_t len) {
 	if (len == 0) SYSCALL_RETURN(0);
 	if (len > EXECBUF_MAX_LEN)
@@ -491,6 +508,7 @@ long _syscall(long num, long a, long b, long c, long d, long e) {
 		break; case _SYS_WAIT2:	_sys_wait2(a, b, (userptr_t)c);
 		break; case _SYS_GETPROCFS:	_sys_getprocfs(a);
 		break; case _SYS_TIME:	_sys_time(a);
+		break; case _SYS_GETNULL:	_sys_getnull(a);
 		break; case _SYS_EXECBUF:	_sys_execbuf((userptr_t)a, b);
 		break; case _SYS_DEBUG_KLOG:	_sys_debug_klog((userptr_t)a, b);
 		break;
-- 
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