kernel: driver: Implement driver blacklist

Sometimes one may not want *all* of the drivers to start up during
system boot. The driver blacklist allows one to mark a driver to be
ignored during startup.

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

2 files changed, 180 insertions, 0 deletions

diff --git a/sys/kern/driver_blacklist.c b/sys/kern/driver_blacklist.c
new file mode 100644
index 0000000..982d5c9
--- /dev/null
+++ b/sys/kern/driver_blacklist.c
@@ -0,0 +1,170 @@
+/*
+ * Copyright (c) 2023-2025 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/queue.h>
+#include <sys/driver.h>
+#include <vm/dynalloc.h>
+#include <string.h>
+
+#define BLACKLIST_SIZE 64
+
+/*
+ * A driver blacklist entry
+ *
+ * @name: Name of driver to be blacklisted
+ * @buckets: To handle collisions
+ */
+struct blacklist_entry {
+    char *name;
+    TAILQ_ENTRY(blacklist_entry) link;
+    TAILQ_HEAD(, blacklist_entry) buckets;
+};
+
+static struct blacklist_entry blacklist[BLACKLIST_SIZE];
+
+static uint32_t
+fnv1_hash(const char *s)
+{
+    uint32_t hash = 2166136261UL;
+    const uint8_t *p = (uint8_t *)s;
+
+    while (*p != '\0') {
+        hash ^= *p;
+        hash = hash * 0x01000193;
+        ++p;
+    }
+
+    return hash;
+}
+
+/*
+ * Returns a bucket in case of collision
+ */
+static struct blacklist_entry *
+blacklist_collide(struct blacklist_entry *entp, const char *name)
+{
+    struct blacklist_entry *tmp;
+
+    if (entp->name == NULL) {
+        return NULL;
+    }
+
+    TAILQ_FOREACH(tmp, &entp->buckets, link) {
+        if (strcmp(name, tmp->name) == 0) {
+            return tmp;
+        }
+    }
+
+    return NULL;
+}
+
+/*
+ * Mark a driver to be ignored during startup.
+ * Blacklisted drivers will not be ran.
+ *
+ * @name: Name of driver (e.g., 'ahci')
+ */
+int
+driver_blacklist(const char *name)
+{
+    struct blacklist_entry *ent;
+    struct blacklist_entry *bucket;
+    size_t name_len;
+    uint32_t hash;
+
+    if (name == NULL) {
+        return -EINVAL;
+    }
+
+    hash = fnv1_hash(name);
+    ent = &blacklist[hash % BLACKLIST_SIZE];
+    if (ent->name != NULL) {
+        bucket = dynalloc(sizeof(*bucket));
+        if (bucket == NULL) {
+            return -EINVAL;
+        }
+        TAILQ_INSERT_TAIL(&ent->buckets, bucket, link);
+        return 0;
+    }
+
+    name_len = strlen(name);
+    ent->name = dynalloc(name_len + 1);
+    if (ent->name == NULL) {
+        return -ENOMEM;
+    }
+    memcpy(ent->name, name, name_len + 1);
+    return 0;
+}
+
+/*
+ * Checks if a driver name is in the blacklist.
+ * Returns 0 if not, otherwise 1.
+ */
+int
+driver_blacklist_check(const char *name)
+{
+    struct blacklist_entry *ent;
+    uint32_t hash;
+
+    if (name == NULL) {
+        return -EINVAL;
+    }
+
+    hash = fnv1_hash(name);
+    ent = &blacklist[hash % BLACKLIST_SIZE];
+    if (ent->name == NULL) {
+        return 0;
+    }
+
+    if (strcmp(ent->name, name) == 0) {
+        return 1;
+    }
+
+    ent = blacklist_collide(ent, name);
+    if (ent != NULL) {
+        return 1;
+    }
+
+    return 0;
+}
+
+/*
+ * Initialize each entry in the driver
+ * blacklist
+ */
+void
+driver_blacklist_init(void)
+{
+    for (size_t i = 0; i < BLACKLIST_SIZE; ++i) {
+        blacklist[i].name = NULL;
+        TAILQ_INIT(&blacklist[i].buckets);
+    }
+}
diff --git a/sys/kern/driver_subr.c b/sys/kern/driver_subr.c
index b53463a..a0f9f73 100644
--- a/sys/kern/driver_subr.c
+++ b/sys/kern/driver_subr.c
@@ -55,6 +55,16 @@ __driver_init_td(void)
 
     for (dp = (void *)start; (uintptr_t)dp < end; ++dp) {
         var = dp->data;
+
+        /*
+         * Check the blacklist to see if this driver
+         * is marked to be ignored. If so, just continue
+         * to the next.
+         */
+        if (driver_blacklist_check(dp->name)) {
+            continue;
+        }
+
         if (var->deferred) {
             dp->init();
             var->deferred = 0;