kernel: vm: Add physical memory allocator

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

2 files changed, 191 insertions, 0 deletions

diff --git a/sys/vm/vm_init.c b/sys/vm/vm_init.c
index 255821a..3e9718d 100644
--- a/sys/vm/vm_init.c
+++ b/sys/vm/vm_init.c
@@ -29,8 +29,15 @@
 
 #include <sys/limine.h>
 #include <vm/vm.h>
+#include <vm/physmem.h>
 
 volatile struct limine_hhdm_request g_hhdm_request = {
     .id = LIMINE_HHDM_REQUEST,
     .revision = 0
 };
+
+void
+vm_init(void)
+{
+    vm_physmem_init();
+}
diff --git a/sys/vm/vm_physmem.c b/sys/vm/vm_physmem.c
new file mode 100644
index 0000000..19e3927
--- /dev/null
+++ b/sys/vm/vm_physmem.c
@@ -0,0 +1,184 @@
+/*
+ * 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/param.h>
+#include <sys/types.h>
+#include <sys/limine.h>
+#include <sys/syslog.h>
+#include <sys/spinlock.h>
+#include <vm/physmem.h>
+#include <vm/vm.h>
+#include <string.h>
+
+size_t highest_frame_idx = 0;
+size_t bitmap_size = 0;
+size_t bitmap_free_start = 0;
+
+uint8_t *bitmap;
+static struct limine_memmap_response *resp = NULL;
+static struct spinlock lock = {0};
+
+static struct limine_memmap_request mmap_req = {
+    .id = LIMINE_MEMMAP_REQUEST,
+    .revision = 0
+};
+
+/*
+ * Populate physical memory bitmap.
+ */
+static void
+physmem_populate_bitmap(void)
+{
+    struct limine_memmap_entry *ent;
+
+    for (size_t i = 0; i < resp->entry_count; ++i) {
+        ent = resp->entries[i];
+
+        if (ent->type != LIMINE_MEMMAP_USABLE) {
+            /* This memory is not usable */
+            continue;
+        }
+
+        if (bitmap_free_start == 0) {
+            bitmap_free_start = ent->base / DEFAULT_PAGESIZE;
+        }
+
+        for (size_t j = 0; j < ent->length; j += DEFAULT_PAGESIZE) {
+            clrbit(bitmap, (ent->base + j) / DEFAULT_PAGESIZE);
+        }
+    }
+}
+
+/*
+ * Allocate physical memory for the bitmap
+ * we'll use to keep track of free memory.
+ */
+static void
+physmem_alloc_bitmap(void)
+{
+    struct limine_memmap_entry *ent;
+    uintptr_t highest_addr = 0;
+
+    for (size_t i = 0; i < resp->entry_count; ++i) {
+        ent = resp->entries[i];
+
+        if (ent->type != LIMINE_MEMMAP_USABLE) {
+            /* This memory is not usable */
+            continue;
+        }
+
+        if (ent->length >= bitmap_size) {
+            bitmap = PHYS_TO_VIRT(ent->base);
+            memset(bitmap, 0xFF, bitmap_size);
+            ent->length -= bitmap_size;
+            ent->base += bitmap_size;
+            return;
+        }
+
+        highest_addr = MAX(highest_addr, ent->base + ent->length);
+    }
+}
+
+
+/*
+ * Init the physical memory bitmap.
+ */
+static void
+physmem_init_bitmap(void)
+{
+    uintptr_t highest_addr = 0;
+    struct limine_memmap_entry *ent;
+
+    for (size_t i = 0; i < resp->entry_count; ++i) {
+        ent = resp->entries[i];
+
+        if (ent->type != LIMINE_MEMMAP_USABLE) {
+            continue;
+        }
+
+        highest_addr = MAX(highest_addr, ent->base + ent->length);
+    }
+
+    highest_frame_idx = highest_addr / DEFAULT_PAGESIZE;
+    bitmap_size = ALIGN_UP(highest_frame_idx / 8, DEFAULT_PAGESIZE);
+
+    physmem_alloc_bitmap();
+    physmem_populate_bitmap();
+}
+
+/*
+ * Allocate page frames.
+ *
+ * @count: Number of frames to allocate.
+ */
+uintptr_t
+vm_alloc_frame(size_t count)
+{
+    size_t frames = 0;
+    uintptr_t ret = 0;
+
+    spinlock_acquire(&lock);
+    for (size_t i = 0; i < highest_frame_idx; ++i) {
+        if (!testbit(bitmap, i)) {
+            /* We have a free page */
+            if (++frames != count) {
+                continue;
+            }
+
+            for (size_t j = i; j < i + count; ++j) {
+                setbit(bitmap, j);
+            }
+
+            ret = i * DEFAULT_PAGESIZE;
+            break;
+        }
+    }
+
+    spinlock_release(&lock);
+    return ret;
+}
+
+void
+vm_free_frame(uintptr_t base, size_t count)
+{
+    size_t stop_at = base + (count * DEFAULT_PAGESIZE);
+
+    spinlock_acquire(&lock);
+    for (uintptr_t p = base; p < stop_at; p += DEFAULT_PAGESIZE) {
+        clrbit(bitmap, p / DEFAULT_PAGESIZE);
+    }
+    spinlock_release(&lock);
+}
+
+void
+vm_physmem_init(void)
+{
+    resp = mmap_req.response;
+    physmem_init_bitmap();
+}