kern: security: Add initial support for MAC

This commit introduces initial support for mandatory access control. As
one may recall, L5 follows "everything is memory". In order to interact
with a resource, a process must request it from the kernel in the form
of a (sometimes) syncable memory buffer.

Each resource as well as processes have an access level, if a process
attempts to request a resource with a higher access level than it, the
request is rejected by the kernel. However, if a process has a greater
than or equal access level as a resource, the request can be granted.

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

1 files changed, 92 insertions, 0 deletions

diff --git a/src/sys/io/video/fbdev.c b/src/sys/io/video/fbdev.c
new file mode 100644
index 0000000..51abea3
--- /dev/null
+++ b/src/sys/io/video/fbdev.c
@@ -0,0 +1,92 @@
+/*
+ * Copyright (c) 2025 Ian Marco Moffett and L5 engineers
+ * 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 the project 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/bootvars.h>
+#include <sys/proc.h>
+#include <sys/mman.h>
+#include <sys/types.h>
+#include <io/video/fbdev.h>
+#include <vm/map.h>
+#include <vm/mmu.h>
+
+/*
+ * Map the framebuffer, we'll decided how many bytes
+ * is mapped.
+ */
+static ssize_t
+fbdev_map(struct mac_border *mbp, struct mac_map_args *args)
+{
+    int prot = PROT_READ | PROT_WRITE | PROT_USER;
+    size_t max_size = 0;
+    struct bootvars bv;
+    struct proc *self = proc_self();
+    struct vm_vas vas;
+    struct bootvar_fb *fbvar;
+    struct mmu_map spec;
+    int error;
+
+    /* Grab the bootvars */
+    error = bootvars_read(&bv, 0);
+    if (error < 0) {
+        return error;
+    }
+
+    /* Grab the current VAS for mapping */
+    error = mmu_this_vas(&vas);
+    if (error < 0) {
+        return error;
+    }
+
+    fbvar = &bv.fbvars;
+    max_size = fbvar->width * fbvar->pitch;
+    if (args->len > max_size) {
+        args->len = max_size;
+    }
+
+    spec.pa = VIRT_TO_PHYS(fbvar->io);
+    spec.va = spec.pa;
+    error = vm_map(&vas, &spec, args->len, prot);
+    if (error < 0) {
+        return error;
+    }
+
+    *args->dp_res = (void *)VIRT_TO_PHYS(fbvar->io);
+    return args->len;
+}
+
+static struct mac_ops ops = {
+    .map = fbdev_map,
+    .sync = NULL,
+    .getattr = NULL
+};
+
+struct mac_border g_fbdev_border = {
+    .level = MAC_RESTRICTED,
+    .ops = &ops
+};