kernel: Introduce initial VSR impl

This commit introduces the initial implementation of Virtual System
Resources (VSRs). Virtual system resources enable specific subsystems to
control global state while the VSR acts as a middle man between the
process, and the actual resource itself. This allows the products of
certain operations to be routed to either the global state or a local
(per-process) "shallow copy" whose data and side effects are only
visible through that process. An example of something this would be
useful for is some sort of transparent access control mechanism where
if a process should not modify global system-wide state, it can at least
modify the state for itself.

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

1 files changed, 360 insertions, 0 deletions

diff --git a/sys/kern/kern_vsr.c b/sys/kern/kern_vsr.c
new file mode 100644
index 0000000..8fb7fc7
--- /dev/null
+++ b/sys/kern/kern_vsr.c
@@ -0,0 +1,360 @@
+/*
+ * 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/vsr.h>
+#include <sys/proc.h>
+#include <sys/param.h>
+#include <sys/limits.h>
+#include <sys/syslog.h>
+#include <vm/dynalloc.h>
+#include <string.h>
+
+#define pr_trace(fmt, ...) kprintf("vsr: " fmt, ##__VA_ARGS__)
+#define pr_error(...) pr_trace(__VA_ARGS__)
+
+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;
+}
+
+/*
+ * Add a VSR capsule to a domain.
+ */
+static void
+vsr_domain_add(struct vsr_domain *vsp, struct vsr_capsule *cap)
+{
+    struct vsr_table *tab;
+    struct vsr_capsule **slot;
+    uint32_t hash;
+
+    if (vsp == NULL || cap == NULL) {
+        return;
+    }
+
+    if (cap->name == NULL) {
+        pr_error("vsr_domain_add: cap->name == NULL\n");
+        return;
+    }
+
+    tab = &vsp->table;
+    hash = fnv1_hash(cap->name);
+    slot = &tab->capsules[hash % VSR_MAX_CAPSULE];
+
+    /* If this slot is free, set it */
+    if (*slot == NULL) {
+        *slot = cap;
+        return;
+    }
+
+    /* Handle collision */
+    TAILQ_INSERT_TAIL(&(*slot)->buckets, cap, link);
+}
+
+/*
+ * Handle VSR domain hashmap collisions.
+ *
+ * @slot: Slot that we have collided with
+ * @name: Name to lookup
+ *
+ * Returns the pointer to the actual capsule if the
+ * collision has been resolved, otherwise, NULL if the
+ * entry to look up was not found.
+ */
+static struct vsr_capsule *
+vsr_domain_clash(struct vsr_capsule *slot, const char *name)
+{
+    struct vsr_capsule *cap_ent;
+
+    TAILQ_FOREACH(cap_ent, &slot->buckets, link) {
+        if (cap_ent == NULL) {
+            continue;
+        }
+
+        if (strcmp(cap_ent->name, name) == 0) {
+            return cap_ent;
+        }
+    }
+
+    return NULL;
+}
+
+/*
+ * Lookup a capsule within a VSR domain
+ * by name.
+ *
+ * @vsp: Domain to lookup within
+ * @name: Name to use as lookup key
+ *
+ * Returns NULL if no entry was found.
+ */
+static struct vsr_capsule *
+vfs_domain_lookup(struct vsr_domain *vsp, const char *name)
+{
+    uint32_t hash;
+    struct vsr_table *tab;
+    struct vsr_capsule **slot;
+
+    if (vsp == NULL || name == NULL) {
+        return NULL;
+    }
+
+    tab = &vsp->table;
+    hash = fnv1_hash(name);
+    slot = &tab->capsules[hash % VSR_MAX_CAPSULE];
+
+    if (*slot == NULL) {
+        return NULL;
+    }
+
+    if (strcmp((*slot)->name, name) != 0) {
+        return vsr_domain_clash(*slot, name);
+    }
+
+    return *slot;
+}
+
+/*
+ * Destroy a VSR capsule
+ *
+ * @capule: Capsule to destroy
+ */
+static void
+vsr_destroy_capsule(struct vsr_capsule *capsule)
+{
+    struct vsr_capsule *bucket;
+    struct capsule_ops *ops;
+
+    if (capsule->name != NULL) {
+        dynfree(capsule->name);
+        capsule->name = NULL;
+    }
+
+    ops = &capsule->ops;
+    if (ops->reclaim != NULL) {
+        ops->reclaim(capsule, 0);
+    }
+
+    TAILQ_FOREACH(bucket, &capsule->buckets, link) {
+        if (bucket == NULL) {
+            continue;
+        }
+        vsr_destroy_capsule(bucket);
+    }
+
+    /* Release any held locks */
+    mutex_release(&capsule->lock);
+}
+
+/*
+ * Destroy a VSR table
+ *
+ * @tab: Table to destroy.
+ */
+static void
+vsr_destroy_table(struct vsr_table *tab)
+{
+    struct vsr_capsule *capsule;
+
+    if (tab == NULL) {
+        pr_error("vsr_destroy_table: tab is NULL\n");
+        return;
+    }
+
+    for (int i = 0; i < VSR_MAX_CAPSULE; ++i) {
+        if ((capsule = tab->capsules[i]) == NULL) {
+            continue;
+        }
+
+        vsr_destroy_capsule(capsule);
+    }
+}
+
+/*
+ * Allocate a new VSR capsule and add it to
+ * VSR domain.
+ */
+struct vsr_capsule *
+vsr_new_capsule(vsr_domain_t type, const char *name)
+{
+    struct vsr_capsule *capsule;
+    struct vsr_domain *domain;
+    struct proc *td = this_td();
+
+    /* Valid type? */
+    if (type >= VSR_MAX_DOMAIN) {
+        return NULL;
+    }
+
+    if (__unlikely(td == NULL)) {
+        return NULL;
+    }
+
+    /*
+     * The VSR domain must be registered for
+     * us to add any capsules to it.
+     */
+    if ((domain = td->vsr_tab[type]) == NULL) {
+        pr_error("VSR domain %d not registered\n", type);
+        return NULL;
+    }
+
+    /* Allocate a new capsule */
+    capsule = dynalloc(sizeof(*capsule));
+    if (capsule == NULL) {
+        return NULL;
+    }
+
+    memset(capsule, 0, sizeof(*capsule));
+    capsule->name = strdup(name);
+
+    TAILQ_INIT(&capsule->buckets);
+    vsr_domain_add(domain, capsule);
+    return capsule;
+}
+
+/*
+ * Allocate a new VSR domain and add it to
+ * the current process.
+ *
+ * @type: VSR type (e.g., VSR_FILE)
+ */
+struct vsr_domain *
+vsr_new_domain(vsr_domain_t type)
+{
+    struct vsr_domain *domain;
+    struct vsr_table *tablep;
+    struct proc *td = this_td();
+
+    /* Valid type? */
+    if (type >= VSR_MAX_DOMAIN) {
+        return NULL;
+    }
+
+    /*
+     * The scheduler should be set up before any
+     * calls to vsr_new_vec() should be made.
+     */
+    if (__unlikely(td == NULL)) {
+        return NULL;
+    }
+
+    /*
+     * Do not overwrite the entry if it is
+     * already allocated and log this anomalous
+     * activity.
+     */
+    if (td->vsr_tab[type] != NULL) {
+        pr_error("[security]: type %d already allocated\n", type);
+        return NULL;
+    }
+
+    domain = dynalloc(sizeof(*domain));
+    if (domain == NULL) {
+        return NULL;
+    }
+
+    /* Initialize the domain */
+    memset(domain, 0, sizeof(*domain));
+    domain->type = type;
+
+    /* Initialize the domain's table */
+    tablep = &domain->table;
+    td->vsr_tab[type] = domain;
+    return domain;
+}
+
+/*
+ * Lookup a capsule by name for the current
+ * process.
+ */
+struct vsr_capsule *
+vsr_lookup_capsule(vsr_domain_t type, const char *name)
+{
+    struct vsr_domain *domain;
+    struct proc *td = this_td();
+
+    /* Must be on a process */
+    if (__unlikely(td == NULL)) {
+        return NULL;
+    }
+
+    /*
+     * The VSR domain must be registered for
+     * us to lookup any capsules from it.
+     */
+    if ((domain = td->vsr_tab[type]) == NULL) {
+        pr_error("VSR domain %d not registered\n", type);
+        return NULL;
+    }
+
+    return vfs_domain_lookup(domain, name);
+}
+
+/*
+ * Initialize per-process domains
+ */
+void
+vsr_init_domains(void)
+{
+    if (vsr_new_domain(VSR_FILE) == NULL) {
+        pr_error("failed to initialize VSR file domain\n");
+    }
+}
+
+/*
+ * Destroy per-process domains
+ */
+void
+vsr_destroy_domains(void)
+{
+    struct proc *td = this_td();
+    struct vsr_domain *domain;
+
+    if (__unlikely(td == NULL)) {
+        return;
+    }
+
+    for (int i = 0; i < VSR_MAX_DOMAIN; ++i) {
+        if ((domain = td->vsr_tab[i]) == NULL) {
+            continue;
+        }
+
+        vsr_destroy_table(&domain->table);
+    }
+}