kernel: vm: Add device pager

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

3 files changed, 158 insertions, 1 deletions

diff --git a/sys/vm/vm_device.c b/sys/vm/vm_device.c
new file mode 100644
index 0000000..976dec7
--- /dev/null
+++ b/sys/vm/vm_device.c
@@ -0,0 +1,119 @@
+/*
+ * 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 <sys/types.h>
+#include <sys/errno.h>
+#include <sys/sio.h>
+#include <sys/vfs.h>
+#include <sys/cdefs.h>
+#include <fs/devfs.h>
+#include <vm/obj.h>
+#include <vm/vm.h>
+#include <vm/pager.h>
+
+static int dv_pager_get(struct vm_object *obj, off_t off, size_t len,
+                        struct vm_page *pg);
+
+static int dv_pager_store(struct vm_object *obj, off_t off, size_t len,
+                          struct vm_page *pg);
+
+static int dv_pager_paddr(struct vm_object *obj, paddr_t *paddr,
+                          vm_prot_t prot);
+
+/* Pager operations */
+struct vm_pagerops g_dev_pagerops = {
+    .get = dv_pager_get,
+    .store = dv_pager_store,
+    .get_paddr = dv_pager_paddr
+};
+
+/*
+ * Fetch a device descriptor from a memory
+ * object.
+ *
+ * Returns 0 on success.
+ */
+static int
+dv_get_dev(struct vm_object *obj, struct device **res)
+{
+    struct device *dev;
+    struct vnode *vp;
+    int status;
+
+    if ((vp = obj->vnode) == NULL)
+        return -EIO;
+
+    /* Now try to fetch the device */
+    if ((status = devfs_get_dev(vp, &dev)) != 0)
+        return status;
+
+    *res = dev;
+    return 0;
+}
+
+static int
+dv_pager_paddr(struct vm_object *obj, paddr_t *paddr, vm_prot_t prot)
+{
+    struct device *dev;
+    int status;
+
+    if (paddr == NULL) {
+        return -EINVAL;
+    }
+
+    /* Try to fetch the device */
+    if ((status = dv_get_dev(obj, &dev)) != 0) {
+        return status;
+    }
+
+    if (dev->mmap == NULL) {
+        /*
+         * mmap() is not supported, this is not an object
+         * we can handle so try switching its operations
+         * to the vnode pager ops...
+         */
+        obj->pgops = &g_vnode_pagerops;
+        return -ENOTSUP;
+    }
+
+    *paddr = dev->mmap(dev, 0, prot);
+    return 0;
+}
+
+static int
+dv_pager_store(struct vm_object *obj, off_t off, size_t len, struct vm_page *pg)
+{
+    return -1;
+}
+
+static int
+dv_pager_get(struct vm_object *obj, off_t off, size_t len, struct vm_page *pg)
+{
+    return -1;
+}
diff --git a/sys/vm/vm_obj.c b/sys/vm/vm_obj.c
index c5fc921..589ca47 100644
--- a/sys/vm/vm_obj.c
+++ b/sys/vm/vm_obj.c
@@ -32,6 +32,22 @@
 #include <sys/errno.h>
 #include <string.h>
 
+static void
+vm_set_pgops(struct vm_object *obj, struct vnode *vnode)
+{
+    if (vnode == NULL) {
+        obj->vnode = NULL;
+        return;
+    }
+
+    /* Is this a device? */
+    if (vnode->type == VCHR || vnode->type == VBLK) {
+        obj->pgops = &g_dev_pagerops;
+    } else {
+        obj->pgops = &g_vnode_pagerops;
+    }
+}
+
 int
 vm_obj_init(struct vm_object **res, struct vnode *vnode)
 {
@@ -43,7 +59,8 @@ vm_obj_init(struct vm_object **res, struct vnode *vnode)
 
     memset(obj, 0, sizeof(struct vm_object));
     obj->vnode = vnode;
-    obj->pgops = &g_vnode_pagerops;
+
+    vm_set_pgops(obj, vnode);
     *res = obj;
     return 0;
 }
diff --git a/sys/vm/vm_pager.c b/sys/vm/vm_pager.c
index b82a9e1..0046e9c 100644
--- a/sys/vm/vm_pager.c
+++ b/sys/vm/vm_pager.c
@@ -45,3 +45,24 @@ vm_pager_get(struct vm_object *obj, off_t off, size_t len, struct vm_page *pg)
 
     return pgops->get(obj, off, len, pg);
 }
+
+/*
+ * Get physical address.
+ *
+ * TODO: Remove this and add demanding paging.
+ */
+int
+vm_pager_paddr(struct vm_object *obj, paddr_t *paddr, vm_prot_t prot)
+{
+    struct vm_pagerops *pgops = obj->pgops;
+
+    if (obj->is_anon) {
+        return -1;
+    }
+
+    if (pgops->get_paddr == NULL) {
+        return 0;
+    }
+
+    return pgops->get_paddr(obj, paddr, prot);
+}