From 0bdb884b331c58d33c3ccf29070e2955095a1acc Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Sun, 15 Dec 2024 22:57:21 -0500
Subject: 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>
---
 sys/vm/vm_page.c | 106 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 106 insertions(+)
 create mode 100644 sys/vm/vm_page.c

(limited to 'sys/vm/vm_page.c')

diff --git a/sys/vm/vm_page.c b/sys/vm/vm_page.c
new file mode 100644
index 0000000..8ada183
--- /dev/null
+++ b/sys/vm/vm_page.c
@@ -0,0 +1,106 @@
+/*
+ * 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.
+ */
+
+#include <vm/vm_page.h>
+#include <vm/vm_obj.h>
+#include <vm/physmem.h>
+#include <vm/dynalloc.h>
+#include <vm/vm.h>
+#include <assert.h>
+#include <string.h>
+
+RBT_GENERATE(vm_objtree, vm_page, objt, vm_pagecmp);
+
+/*
+ * Insert a page into an object.
+ */
+static inline void
+vm_pageinsert(struct vm_page *pg, struct vm_object *obp)
+{
+   struct vm_page *tmp;
+
+   tmp = RBT_INSERT(vm_objtree, &obp->objt, pg);
+   __assert(tmp == NULL);
+   ++obp->npages;
+}
+
+static inline void
+vm_pageremove(struct vm_page *pg, struct vm_object *obp)
+{
+    RBT_REMOVE(vm_objtree, &obp->objt, pg);
+    --obp->npages;
+}
+
+struct vm_page *
+vm_pagelookup(struct vm_object *obj, off_t off)
+{
+    struct vm_page tmp;
+
+    tmp.offset = off;
+    return RBT_FIND(vm_objtree, &obj->objt, &tmp);
+}
+
+struct vm_page *
+vm_pagealloc(struct vm_object *obj, int flags)
+{
+    struct vm_page *tmp;
+
+    tmp = dynalloc(sizeof(*tmp));
+    if (tmp == NULL) {
+        return NULL;
+    }
+
+    memset(tmp, 0, sizeof(*tmp));
+    tmp->phys_addr = vm_alloc_frame(1);
+    tmp->flags |= (PG_VALID | PG_CLEAN);
+    __assert(tmp->phys_addr != 0);
+
+    if (ISSET(flags, PALLOC_ZERO)) {
+        memset(PHYS_TO_VIRT(tmp->phys_addr), 0, DEFAULT_PAGESIZE);
+    }
+
+    vm_pageinsert(tmp, obj);
+    return tmp;
+}
+
+void
+vm_pagefree(struct vm_object *obj, struct vm_page *pg, int flags)
+{
+    __assert(pg->phys_addr != 0);
+
+    vm_pageremove(pg, obj);
+    vm_free_frame(pg->phys_addr, 1);
+    dynfree(pg);
+}
+
+int
+vm_pagecmp(const struct vm_page *a, const struct vm_page *b)
+{
+    return (a->offset < b->offset) ? -1 : a->offset > b->offset;
+}
-- 
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