os: vm: Add physical memory manager

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

1 files changed, 264 insertions, 0 deletions

diff --git a/src/sys/vm/vm_seg.c b/src/sys/vm/vm_seg.c
new file mode 100644
index 0000000..94a00ee
--- /dev/null
+++ b/src/sys/vm/vm_seg.c
@@ -0,0 +1,264 @@
+/*
+ * 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/param.h>
+#include <sys/types.h>
+#include <sys/syslog.h>
+#include <sys/panic.h>
+#include <os/spinlock.h>
+#include <vm/physseg.h>
+#include <vm/vm.h>
+#include <limine.h>
+#include <string.h>
+
+#define BYTES_PER_MIB 8388608
+
+static size_t pages_free = 0;
+static size_t pages_used = 0;
+static size_t pages_total = 0;
+static size_t highest_frame_idx = 0;
+static size_t bitmap_size = 0;
+static size_t bitmap_free_start = 0;
+static ssize_t last_idx = 0;
+
+static 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
+};
+
+static const char *memstr_tab[] = {
+    [LIMINE_MEMMAP_USABLE] = "usable",
+    [LIMINE_MEMMAP_RESERVED] = "reserved",
+    [LIMINE_MEMMAP_ACPI_RECLAIMABLE] = "ACPI reclaimable",
+    [LIMINE_MEMMAP_ACPI_NVS] = "ACPI NVS",
+    [LIMINE_MEMMAP_BAD_MEMORY] = "bad",
+    [LIMINE_MEMMAP_BOOTLOADER_RECLAIMABLE] = "bootloader reclaimable",
+    [LIMINE_MEMMAP_KERNEL_AND_MODULES] = "ethos0",
+    [LIMINE_MEMMAP_FRAMEBUFFER] = "vram"
+};
+
+/*
+ * 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];
+        pages_total += ent->length / DEFAULT_PAGESIZE;
+
+        if (ent->type != LIMINE_MEMMAP_USABLE) {
+            /* This memory is not usable */
+            pages_used += ent->length / DEFAULT_PAGESIZE;
+            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);
+        }
+
+        pages_free += ent->length / 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;
+    uintptr_t start, end;
+    const char *typestr = "bad";
+
+    for (size_t i = 0; i < resp->entry_count; ++i) {
+        ent = resp->entries[i];
+
+        if (ent->type < NELEM(memstr_tab)) {
+            typestr = memstr_tab[ent->type];
+        }
+
+        start = ent->base;
+        end = ent->base + ent->length;
+        printf("sysmem: [%p -> %p]: %s\n", start, end, typestr);
+
+        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.
+ */
+static uintptr_t
+__vm_alloc_frame(size_t count)
+{
+    size_t frames = 0;
+    ssize_t idx = -1;
+    uintptr_t ret = 0;
+
+    for (size_t i = last_idx; i < highest_frame_idx; ++i) {
+        if (!testbit(bitmap, i)) {
+            if (idx < 0)
+                idx = i;
+            if (++frames >= count)
+                break;
+
+            continue;
+        }
+
+        idx = -1;
+        frames = 0;
+    }
+
+    if (idx < 0 || frames != count) {
+        ret = 0;
+        goto done;
+    }
+
+    for (size_t i = idx; i < idx + count; ++i) {
+        setbit(bitmap, i);
+    }
+    ret = idx * DEFAULT_PAGESIZE;
+    last_idx = idx;
+    memset(PHYS_TO_VIRT(ret), 0, count * DEFAULT_PAGESIZE);
+done:
+    return ret;
+}
+
+/*
+ * Central frame allocation routine
+ */
+uintptr_t
+vm_alloc_frame(size_t count)
+{
+    uintptr_t ret;
+
+    spinlock_acquire(&lock);
+    if ((ret = __vm_alloc_frame(count)) == 0) {
+        last_idx = 0;
+        ret = __vm_alloc_frame(count);
+    }
+
+    if (ret == 0) {
+        panic("out of memory\n");
+    }
+
+    pages_used += count;
+    pages_free -= count;
+    spinlock_release(&lock);
+    return ret;
+}
+
+/*
+ * Central frame freeing routine
+ */
+void
+vm_free_frame(uintptr_t base, size_t count)
+{
+    size_t stop_at = base + (count * DEFAULT_PAGESIZE);
+
+    base = ALIGN_UP(base, DEFAULT_PAGESIZE);
+
+    spinlock_acquire(&lock);
+    for (uintptr_t p = base; p < stop_at; p += DEFAULT_PAGESIZE) {
+        clrbit(bitmap, p / DEFAULT_PAGESIZE);
+    }
+    pages_used -= count;
+    pages_free += count;
+    spinlock_release(&lock);
+}
+
+int
+vm_seg_init(struct physmem_stat *stat)
+{
+    resp = mmap_req.response;
+    physmem_init_bitmap();
+
+    stat->pages_free = pages_free;
+    stat->pages_used = pages_used;
+    printf(
+        "physseg initialized [free: %d, used: %d]\n",
+        pages_free,
+        pages_used
+    );
+    return 0;
+}