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, 185 insertions, 0 deletions

diff --git a/sys/vm/vm_vnode.c b/sys/vm/vm_vnode.c
new file mode 100644
index 0000000..31e74cc
--- /dev/null
+++ b/sys/vm/vm_vnode.c
@@ -0,0 +1,185 @@
+/*
+ * 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/cdefs.h>
+#include <sys/errno.h>
+#include <sys/syslog.h>
+#include <sys/systm.h>
+#include <sys/vnode.h>
+#include <vm/vm_vnode.h>
+#include <vm/vm_page.h>
+#include <vm/pmap.h>
+#include <vm/vm.h>
+
+#define VN_TIMEOUT_USEC 200000
+
+#define pr_trace(fmt, ...) kprintf("vm_vnode: " fmt, ##__VA_ARGS__)
+#define pr_error(...) pr_trace(__VA_ARGS__)
+
+/* Debug print helper */
+#if defined(PR_DEBUG)
+#define pr_debug(...) pr_trace(__VA_ARGS__)
+#else
+#define pr_debug(...) __nothing
+#endif  /* PR_DEBUG */
+
+const struct vm_pagerops vm_vnops;
+
+/*
+ * Perform read/write operation on vnode to/from pages.
+ *
+ * Returns number of bytes read.
+ */
+static int
+vn_io(struct vnode *vp, struct vm_page **pgs, unsigned int npages, int rw)
+{
+    struct vop_getattr_args args;
+    struct sio_txn sio;
+    struct vattr vattr;
+    size_t c, read = 0;
+    int err;
+
+    /* TODO: Add support for writes */
+    if (rw != 0) {
+        return -ENOTSUP;
+    }
+
+    args.vp = vp;
+    args.res = &vattr;
+    c = MAX(vattr.size / DEFAULT_PAGESIZE, 1);
+
+    if ((err = vfs_vop_getattr(vp, &args)) != 0) {
+        return err;
+    }
+
+    if (npages > c) {
+        npages = c;
+    }
+
+    /* Prepare SIO constants */
+    sio.len = DEFAULT_PAGESIZE;
+    sio.offset = 0;
+
+    /* Copy in each page */
+    for (size_t i = 0; i < npages; ++i) {
+        sio.buf = PHYS_TO_VIRT(pgs[i]->phys_addr);
+        read = vfs_vop_read(vp, &sio);
+        if (read < 0)
+            pr_debug("vn_io: page-in @ %p failed (err=%d)\n", err);
+    }
+
+    return read;
+}
+
+/*
+ * Get pages from backing store.
+ *
+ * @obp: Object representing the backing store.
+ * @pgs: Page descriptors to be filled.
+ * @off: Offset to read from in backing store.
+ * @len: Length to read in bytes.
+ */
+static int
+vn_get(struct vm_object *obp, struct vm_page **pgs, off_t off, size_t len)
+{
+    struct vm_page *pgtmp;
+    size_t j, pgcnt;
+
+    spinlock_acquire(&obp->lock);
+
+    for (int i = off; i < len; i += DEFAULT_PAGESIZE) {
+        j = i / DEFAULT_PAGESIZE;
+        pgtmp = vm_pagelookup(obp, i);
+
+        /*
+         * If we have no corresponding page in the object
+         * at this offset, we will need to make our own.
+         */
+        if (pgtmp == NULL) {
+            pgtmp = vm_pagealloc(obp, PALLOC_ZERO);
+            if (pgtmp == NULL) {
+                pgs[j]->flags &= ~PG_VALID;
+                continue;
+            }
+            pgtmp->offset = i;
+            pgs[j] = pgtmp;
+        }
+
+        if (spinlock_usleep(&pgtmp->lock, VN_TIMEOUT_USEC) != 0) {
+            pgs[j]->flags &= ~PG_VALID;
+            continue;
+        }
+
+        /* Set the page count and ensure it is valid */
+        pgcnt = ALIGN_DOWN(len, DEFAULT_PAGESIZE);
+        pgcnt = MAX(pgcnt, 1);
+
+        /* Page in and save this pgtmp */
+        vn_io(obp->data, &pgtmp, pgcnt, 0);
+        pgs[j] = pgtmp;
+        spinlock_release(&pgtmp->lock);
+    }
+
+    spinlock_release(&obp->lock);
+    return 0;
+}
+
+/*
+ * Attach a virtual memory object to a vnode.
+ *
+ * @vp: Vnode to attach to.
+ */
+struct vm_object *
+vn_attach(struct vnode *vp, vm_prot_t prot)
+{
+    struct vm_object *vmobj;
+    int error;
+
+    if (vp->type != VREG) {
+        pr_error("vn_attach: vp=%p, prot=%x\n", vp, prot);
+        pr_error("vn_attach: Special files not supported yet!\n");
+        return NULL;
+    }
+
+    error = vm_obj_init(&vp->vobj, &vm_vnops, 1);
+    if (error != 0) {
+        return NULL;
+    }
+
+    vmobj = &vp->vobj;
+    vmobj->prot = prot;
+    vmobj->data = vp;
+    vmobj->pgops = &vm_vnops;
+    return vmobj;
+}
+
+const struct vm_pagerops vm_vnops = {
+    .get = vn_get
+};