kernel: seek syscall

kernel-src/sys/syscalls/seek.c

@@ -0,0 +1,68 @@
+#include <kernel/syscalls.h>
+#include <kernel/file.h>
+#include <kernel/vfs.h>
+#include <errno.h>
+
+#define SEEK_SET 0
+#define SEEK_CUR 1
+#define SEEK_END 2
+
+syscallret_t syscall_seek(context_t *context, int fd, off_t offset, int whence) {
+	syscallret_t ret = {
+		.ret = -1
+	};
+
+	if (whence > 2) {
+		ret.errno = EINVAL;
+		return ret;
+	}
+
+	file_t *file = fd_get(fd);
+	if (file == NULL) {
+		ret.errno = EBADF;
+		return ret;
+	}
+
+	if (file->vnode->type == V_TYPE_SOCKET || file->vnode->type == V_TYPE_FIFO) {
+		ret.errno = ESPIPE;
+		goto cleanup;
+	}
+
+	// TODO device check seek
+
+	switch (whence) {
+		case SEEK_SET:
+		file->offset = offset;
+		break;
+		case SEEK_CUR: {
+			uintmax_t newoffset = file->offset + offset;
+			if (offset > 0 && newoffset < file->offset) {
+				ret.errno = EOVERFLOW;
+				goto cleanup;
+			}
+			if (offset < 0 && newoffset > file->offset) {
+				ret.errno = EINVAL;
+				goto cleanup;
+			}
+			file->offset = newoffset;
+			break;
+		}
+		case SEEK_END: {
+			vattr_t attr;
+			VOP_LOCK(file->vnode);
+			ret.errno = VOP_GETATTR(file->vnode, &attr, &_cpu()->thread->proc->cred);
+			VOP_UNLOCK(file->vnode);
+			if (ret.errno) 
+				goto cleanup;
+			file->offset = attr.size;
+			break;
+		}
+	}
+
+	ret.ret = file->offset;
+	ret.errno = 0;
+
+	cleanup:
+	fd_release(file);
+	return ret;
+}