kernel: vm: Add initial demand paging support

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

1 files changed, 114 insertions, 0 deletions

diff --git a/sys/vm/vm_fault.c b/sys/vm/vm_fault.c
new file mode 100644
index 0000000..ec733e8
--- /dev/null
+++ b/sys/vm/vm_fault.c
@@ -0,0 +1,114 @@
+/*
+ * 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/sched.h>
+#include <vm/fault.h>
+#include <vm/map.h>
+#include <vm/pmap.h>
+#include <vm/vm.h>
+#include <vm/physseg.h>
+
+static struct vm_mapping *
+vm_mapq_search(vm_mapq_t *mq, vaddr_t addr)
+{
+    struct vm_mapping *mapping;
+    const struct vm_range *range;
+
+    TAILQ_FOREACH(mapping, mq, link) {
+        range = &mapping->range;
+        if (addr >= range->start && addr <= range->end) {
+            return mapping;
+        }
+    }
+
+    return NULL;
+}
+
+static struct vm_mapping *
+vm_find_mapping(vaddr_t addr)
+{
+    struct vm_mapping *mapping;
+    struct proc *td;
+    vm_mapq_t *mapq;
+
+    mapping = vm_mapping_fetch(&td->mapspace, addr);
+    if (mapping != NULL)
+        return mapping;
+
+    /* Need to search other maps */
+    td = this_td();
+    for (size_t i = 0; i < MTAB_ENTRIES; ++i) {
+        mapq = &td->mapspace.mtab[i];
+        mapping = vm_mapq_search(mapq, addr);
+        if (mapping != NULL)
+            return mapping;
+    }
+
+    return NULL;
+}
+
+int
+vm_fault(vaddr_t va, vm_prot_t access_type)
+{
+    struct proc *td = this_td();
+    struct vm_mapping *mapping;
+    struct vm_object *vmobj;
+
+    size_t granule = vm_get_page_size();
+    vaddr_t va_base = va &= ~(granule - 1);
+
+    int s;
+    paddr_t pa_base;
+
+    mapping = vm_find_mapping(va_base);
+    if (mapping == NULL)
+        return -1;
+
+    if ((vmobj = mapping->vmobj) == NULL)
+        /* Virtual memory object non-existent */
+        return -1;
+    if (!vmobj->demand)
+        /* Demand paging not enabled for this object */
+        return -1;
+    if ((access_type & ~mapping->prot) != 0)
+        /* Invalid access type */
+        return -1;
+
+    /* Allocate physical memory if needed */
+    if (mapping->physmem_base == 0) {
+        pa_base = vm_alloc_pageframe(1);
+        mapping->physmem_base = pa_base;
+    } else {
+        pa_base = mapping->physmem_base;
+    }
+
+    s = vm_map_create(td->addrsp, va_base, pa_base, access_type, granule);
+    return s;
+}