kernel: vm: Add objects, page struct and pagers

This commit expands the virtual memory subsystem by providing the
initial implementation of virtual memory objects, pager descriptors and
pagers. This change currently implemenents a minimal vnode pager.

Signed-off-by: Ian Moffett <ian@osmora.org>

1 files changed, 65 insertions, 0 deletions

diff --git a/sys/include/vm/vm_page.h b/sys/include/vm/vm_page.h
new file mode 100644
index 0000000..665431c
--- /dev/null
+++ b/sys/include/vm/vm_page.h
@@ -0,0 +1,65 @@
+/*
+ * Copyright (c) 2023-2024 Ian Marco Moffett and the Osmora Team.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of Hyra nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _VM_PAGE_H_
+#define _VM_PAGE_H_
+
+#include <sys/types.h>
+#include <sys/tree.h>
+#include <sys/queue.h>
+#include <sys/param.h>
+#include <sys/spinlock.h>
+
+struct vm_object;
+
+/*
+ * Represents a single virtual memory page.
+ */
+struct vm_page {
+    TAILQ_ENTRY(vm_page) pageq;     /* Queue data */
+    RBT_ENTRY(vm_page) objt;        /* Object tree */
+    paddr_t phys_addr;              /* Physical address of page */
+    struct spinlock lock;           /* Page lock */
+    uint32_t flags;                 /* Page flags */
+    off_t offset;                   /* Offset into object */
+};
+
+/* Page flags */
+#define PG_VALID    BIT(0)      /* Has to be set to be valid */
+#define PG_CLEAN    BIT(1)      /* Page has not be written to */
+#define PG_REQ      BIT(2)      /* Page has been requested by someone */
+
+/* Page alloc flags */
+#define PALLOC_ZERO BIT(0)
+
+struct vm_page *vm_pagelookup(struct vm_object *obj, off_t off);
+struct vm_page *vm_pagealloc(struct vm_object *obj, int flags);
+void vm_pagefree(struct vm_object *obj, struct vm_page *pg, int flags);
+
+#endif  /* !_VM_PAGE_H_ */