vm: verbatim import of x15's physical page allocator

5 files changed, 1812 insertions, 281 deletions

diff --git a/Makefrag.am b/Makefrag.am
index b9d96c5..35a4884 100644
--- a/Makefrag.am
+++ b/Makefrag.am
@@ -259,6 +259,7 @@ libkernel_a_SOURCES += \
 	vm/vm_map.h \
 	vm/vm_object.c \
 	vm/vm_object.h \
+	vm/vm_page.c \
 	vm/vm_page.h \
 	vm/vm_pageout.c \
 	vm/vm_pageout.h \
diff --git a/i386/i386at/biosmem.c b/i386/i386at/biosmem.c
new file mode 100644
index 0000000..f626df8
--- /dev/null
+++ b/i386/i386at/biosmem.c
@@ -0,0 +1,831 @@
+/*
+ * Copyright (c) 2010-2014 Richard Braun.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <kern/assert.h>
+#include <kern/init.h>
+#include <kern/macros.h>
+#include <kern/panic.h>
+#include <kern/param.h>
+#include <kern/printk.h>
+#include <kern/stddef.h>
+#include <kern/stdint.h>
+#include <kern/string.h>
+#include <kern/types.h>
+#include <machine/biosmem.h>
+#include <machine/boot.h>
+#include <machine/cpu.h>
+#include <machine/elf.h>
+#include <machine/multiboot.h>
+#include <vm/vm_kmem.h>
+#include <vm/vm_page.h>
+
+/*
+ * Maximum number of entries in the BIOS memory map.
+ *
+ * Because of adjustments of overlapping ranges, the memory map can grow
+ * to twice this size.
+ */
+#define BIOSMEM_MAX_MAP_SIZE 128
+
+/*
+ * Memory range types.
+ */
+#define BIOSMEM_TYPE_AVAILABLE  1
+#define BIOSMEM_TYPE_RESERVED   2
+#define BIOSMEM_TYPE_ACPI       3
+#define BIOSMEM_TYPE_NVS        4
+#define BIOSMEM_TYPE_UNUSABLE   5
+#define BIOSMEM_TYPE_DISABLED   6
+
+/*
+ * Memory map entry.
+ */
+struct biosmem_map_entry {
+    uint64_t base_addr;
+    uint64_t length;
+    unsigned int type;
+};
+
+/*
+ * Contiguous block of physical memory.
+ *
+ * Tha "available" range records what has been passed to the VM system as
+ * available inside the segment.
+ */
+struct biosmem_segment {
+    phys_addr_t start;
+    phys_addr_t end;
+    phys_addr_t avail_start;
+    phys_addr_t avail_end;
+};
+
+/*
+ * Memory map built from the information passed by the boot loader.
+ *
+ * If the boot loader didn't pass a valid memory map, a simple map is built
+ * based on the mem_lower and mem_upper multiboot fields.
+ */
+static struct biosmem_map_entry biosmem_map[BIOSMEM_MAX_MAP_SIZE * 2]
+    __bootdata;
+static unsigned int biosmem_map_size __bootdata;
+
+/*
+ * Physical segment boundaries.
+ */
+static struct biosmem_segment biosmem_segments[VM_PAGE_MAX_SEGS] __bootdata;
+
+/*
+ * Boundaries of the simple bootstrap heap.
+ *
+ * This heap is located above BIOS memory.
+ */
+static uint32_t biosmem_heap_start __bootdata;
+static uint32_t biosmem_heap_cur __bootdata;
+static uint32_t biosmem_heap_end __bootdata;
+
+static char biosmem_panic_toobig_msg[] __bootdata
+    = "biosmem: too many memory map entries";
+static char biosmem_panic_setup_msg[] __bootdata
+    = "biosmem: unable to set up the early memory allocator";
+static char biosmem_panic_noseg_msg[] __bootdata
+    = "biosmem: unable to find any memory segment";
+static char biosmem_panic_inval_msg[] __bootdata
+    = "biosmem: attempt to allocate 0 page";
+static char biosmem_panic_nomem_msg[] __bootdata
+    = "biosmem: unable to allocate memory";
+
+static void __boot
+biosmem_map_build(const struct multiboot_raw_info *mbi)
+{
+    struct multiboot_raw_mmap_entry *mb_entry, *mb_end;
+    struct biosmem_map_entry *start, *entry, *end;
+    unsigned long addr;
+
+    addr = mbi->mmap_addr;
+    mb_entry = (struct multiboot_raw_mmap_entry *)addr;
+    mb_end = (struct multiboot_raw_mmap_entry *)(addr + mbi->mmap_length);
+    start = biosmem_map;
+    entry = start;
+    end = entry + BIOSMEM_MAX_MAP_SIZE;
+
+    while ((mb_entry < mb_end) && (entry < end)) {
+        entry->base_addr = mb_entry->base_addr;
+        entry->length = mb_entry->length;
+        entry->type = mb_entry->type;
+
+        mb_entry = (void *)mb_entry + sizeof(mb_entry->size) + mb_entry->size;
+        entry++;
+    }
+
+    biosmem_map_size = entry - start;
+}
+
+static void __boot
+biosmem_map_build_simple(const struct multiboot_raw_info *mbi)
+{
+    struct biosmem_map_entry *entry;
+
+    entry = biosmem_map;
+    entry->base_addr = 0;
+    entry->length = mbi->mem_lower << 10;
+    entry->type = BIOSMEM_TYPE_AVAILABLE;
+
+    entry++;
+    entry->base_addr = BIOSMEM_END;
+    entry->length = mbi->mem_upper << 10;
+    entry->type = BIOSMEM_TYPE_AVAILABLE;
+
+    biosmem_map_size = 2;
+}
+
+static int __boot
+biosmem_map_entry_is_invalid(const struct biosmem_map_entry *entry)
+{
+    return (entry->base_addr + entry->length) <= entry->base_addr;
+}
+
+static void __boot
+biosmem_map_filter(void)
+{
+    struct biosmem_map_entry *entry;
+    unsigned int i;
+
+    i = 0;
+
+    while (i < biosmem_map_size) {
+        entry = &biosmem_map[i];
+
+        if (biosmem_map_entry_is_invalid(entry)) {
+            biosmem_map_size--;
+            boot_memmove(entry, entry + 1,
+                         (biosmem_map_size - i) * sizeof(*entry));
+            continue;
+        }
+
+        i++;
+    }
+}
+
+static void __boot
+biosmem_map_sort(void)
+{
+    struct biosmem_map_entry tmp;
+    unsigned int i, j;
+
+    /*
+     * Simple insertion sort.
+     */
+    for (i = 1; i < biosmem_map_size; i++) {
+        tmp = biosmem_map[i];
+
+        for (j = i - 1; j < i; j--) {
+            if (biosmem_map[j].base_addr < tmp.base_addr)
+                break;
+
+            biosmem_map[j + 1] = biosmem_map[j];
+        }
+
+        biosmem_map[j + 1] = tmp;
+    }
+}
+
+static void __boot
+biosmem_map_adjust(void)
+{
+    struct biosmem_map_entry tmp, *a, *b, *first, *second;
+    uint64_t a_end, b_end, last_end;
+    unsigned int i, j, last_type;
+
+    biosmem_map_filter();
+
+    /*
+     * Resolve overlapping areas, giving priority to most restrictive
+     * (i.e. numerically higher) types.
+     */
+    for (i = 0; i < biosmem_map_size; i++) {
+        a = &biosmem_map[i];
+        a_end = a->base_addr + a->length;
+
+        j = i + 1;
+
+        while (j < biosmem_map_size) {
+            b = &biosmem_map[j];
+            b_end = b->base_addr + b->length;
+
+            if ((a->base_addr >= b_end) || (a_end <= b->base_addr)) {
+                j++;
+                continue;
+            }
+
+            if (a->base_addr < b->base_addr) {
+                first = a;
+                second = b;
+            } else {
+                first = b;
+                second = a;
+            }
+
+            if (a_end > b_end) {
+                last_end = a_end;
+                last_type = a->type;
+            } else {
+                last_end = b_end;
+                last_type = b->type;
+            }
+
+            tmp.base_addr = second->base_addr;
+            tmp.length = MIN(a_end, b_end) - tmp.base_addr;
+            tmp.type = MAX(a->type, b->type);
+            first->length = tmp.base_addr - first->base_addr;
+            second->base_addr += tmp.length;
+            second->length = last_end - second->base_addr;
+            second->type = last_type;
+
+            /*
+             * Filter out invalid entries.
+             */
+            if (biosmem_map_entry_is_invalid(a)
+                && biosmem_map_entry_is_invalid(b)) {
+                *a = tmp;
+                biosmem_map_size--;
+                memmove(b, b + 1, (biosmem_map_size - j) * sizeof(*b));
+                continue;
+            } else if (biosmem_map_entry_is_invalid(a)) {
+                *a = tmp;
+                j++;
+                continue;
+            } else if (biosmem_map_entry_is_invalid(b)) {
+                *b = tmp;
+                j++;
+                continue;
+            }
+
+            if (tmp.type == a->type)
+                first = a;
+            else if (tmp.type == b->type)
+                first = b;
+            else {
+
+                /*
+                 * If the overlapping area can't be merged with one of its
+                 * neighbors, it must be added as a new entry.
+                 */
+
+                if (biosmem_map_size >= ARRAY_SIZE(biosmem_map))
+                    boot_panic(biosmem_panic_toobig_msg);
+
+                biosmem_map[biosmem_map_size] = tmp;
+                biosmem_map_size++;
+                j++;
+                continue;
+            }
+
+            if (first->base_addr > tmp.base_addr)
+                first->base_addr = tmp.base_addr;
+
+            first->length += tmp.length;
+            j++;
+        }
+    }
+
+    biosmem_map_sort();
+}
+
+static int __boot
+biosmem_map_find_avail(phys_addr_t *phys_start, phys_addr_t *phys_end)
+{
+    const struct biosmem_map_entry *entry, *map_end;
+    phys_addr_t seg_start, seg_end;
+    uint64_t start, end;
+
+    seg_start = (phys_addr_t)-1;
+    seg_end = (phys_addr_t)-1;
+    map_end = biosmem_map + biosmem_map_size;
+
+    for (entry = biosmem_map; entry < map_end; entry++) {
+        if (entry->type != BIOSMEM_TYPE_AVAILABLE)
+            continue;
+
+        start = vm_page_round(entry->base_addr);
+
+        if (start >= *phys_end)
+            break;
+
+        end = vm_page_trunc(entry->base_addr + entry->length);
+
+        if ((start < end) && (start < *phys_end) && (end > *phys_start)) {
+            if (seg_start == (phys_addr_t)-1)
+                seg_start = start;
+
+            seg_end = end;
+        }
+    }
+
+    if ((seg_start == (phys_addr_t)-1) || (seg_end == (phys_addr_t)-1))
+        return -1;
+
+    if (seg_start > *phys_start)
+        *phys_start = seg_start;
+
+    if (seg_end < *phys_end)
+        *phys_end = seg_end;
+
+    return 0;
+}
+
+static void __boot
+biosmem_set_segment(unsigned int seg_index, phys_addr_t start, phys_addr_t end)
+{
+    biosmem_segments[seg_index].start = start;
+    biosmem_segments[seg_index].end = end;
+}
+
+static phys_addr_t __boot
+biosmem_segment_end(unsigned int seg_index)
+{
+    return biosmem_segments[seg_index].end;
+}
+
+static phys_addr_t __boot
+biosmem_segment_size(unsigned int seg_index)
+{
+    return biosmem_segments[seg_index].end - biosmem_segments[seg_index].start;
+}
+
+static void __boot
+biosmem_save_cmdline_sizes(struct multiboot_raw_info *mbi)
+{
+    struct multiboot_raw_module *mod;
+    uint32_t i;
+
+    if (mbi->flags & MULTIBOOT_LOADER_CMDLINE)
+        mbi->unused0 = boot_strlen((char *)(unsigned long)mbi->cmdline) + 1;
+
+    if (mbi->flags & MULTIBOOT_LOADER_MODULES) {
+        unsigned long addr;
+
+        addr = mbi->mods_addr;
+
+        for (i = 0; i < mbi->mods_count; i++) {
+            mod = (struct multiboot_raw_module *)addr + i;
+            mod->reserved = boot_strlen((char *)(unsigned long)mod->string) + 1;
+        }
+    }
+}
+
+static void __boot
+biosmem_find_boot_data_update(uint32_t min, uint32_t *start, uint32_t *end,
+                              uint32_t data_start, uint32_t data_end)
+{
+    if ((min <= data_start) && (data_start < *start)) {
+        *start = data_start;
+        *end = data_end;
+    }
+}
+
+/*
+ * Find the first boot data in the given range, and return their containing
+ * area (start address is returned directly, end address is returned in end).
+ * The following are considered boot data :
+ *  - the kernel
+ *  - the kernel command line
+ *  - the module table
+ *  - the modules
+ *  - the modules command lines
+ *  - the ELF section header table
+ *  - the ELF .shstrtab, .symtab and .strtab sections
+ *
+ * If no boot data was found, 0 is returned, and the end address isn't set.
+ */
+static uint32_t __boot
+biosmem_find_boot_data(const struct multiboot_raw_info *mbi, uint32_t min,
+                       uint32_t max, uint32_t *endp)
+{
+    struct multiboot_raw_module *mod;
+    struct elf_shdr *shdr;
+    uint32_t i, start, end = end;
+    unsigned long tmp;
+
+    start = max;
+
+    biosmem_find_boot_data_update(min, &start, &end, (unsigned long)&_boot,
+                                  BOOT_VTOP((unsigned long)&_end));
+
+    if ((mbi->flags & MULTIBOOT_LOADER_CMDLINE) && (mbi->cmdline != 0))
+        biosmem_find_boot_data_update(min, &start, &end, mbi->cmdline,
+                                      mbi->cmdline + mbi->unused0);
+
+    if (mbi->flags & MULTIBOOT_LOADER_MODULES) {
+        i = mbi->mods_count * sizeof(struct multiboot_raw_module);
+        biosmem_find_boot_data_update(min, &start, &end, mbi->mods_addr,
+                                      mbi->mods_addr + i);
+        tmp = mbi->mods_addr;
+
+        for (i = 0; i < mbi->mods_count; i++) {
+            mod = (struct multiboot_raw_module *)tmp + i;
+            biosmem_find_boot_data_update(min, &start, &end, mod->mod_start,
+                                          mod->mod_end);
+
+            if (mod->string != 0)
+                biosmem_find_boot_data_update(min, &start, &end, mod->string,
+                                              mod->string + mod->reserved);
+        }
+    }
+
+    if (mbi->flags & MULTIBOOT_LOADER_SHDR) {
+        tmp = mbi->shdr_num * mbi->shdr_size;
+        biosmem_find_boot_data_update(min, &start, &end, mbi->shdr_addr,
+                                      mbi->shdr_addr + tmp);
+        tmp = mbi->shdr_addr;
+
+        for (i = 0; i < mbi->shdr_num; i++) {
+            shdr = (struct elf_shdr *)(tmp + (i * mbi->shdr_size));
+
+            if ((shdr->type != ELF_SHT_SYMTAB)
+                && (shdr->type != ELF_SHT_STRTAB))
+                continue;
+
+            biosmem_find_boot_data_update(min, &start, &end, shdr->addr,
+                                          shdr->addr + shdr->size);
+        }
+    }
+
+    if (start == max)
+        return 0;
+
+    *endp = end;
+    return start;
+}
+
+static void __boot
+biosmem_setup_allocator(struct multiboot_raw_info *mbi)
+{
+    uint32_t heap_start, heap_end, max_heap_start, max_heap_end;
+    uint32_t mem_end, next;
+
+    /*
+     * Find some memory for the heap. Look for the largest unused area in
+     * upper memory, carefully avoiding all boot data.
+     */
+    mem_end = vm_page_trunc((mbi->mem_upper + 1024) << 10);
+
+#ifndef __LP64__
+    if (mem_end > VM_PAGE_DIRECTMAP_LIMIT)
+        mem_end = VM_PAGE_DIRECTMAP_LIMIT;
+#endif /* __LP64__ */
+
+    max_heap_start = 0;
+    max_heap_end = 0;
+    next = BIOSMEM_END;
+
+    do {
+        heap_start = next;
+        heap_end = biosmem_find_boot_data(mbi, heap_start, mem_end, &next);
+
+        if (heap_end == 0) {
+            heap_end = mem_end;
+            next = 0;
+        }
+
+        if ((heap_end - heap_start) > (max_heap_end - max_heap_start)) {
+            max_heap_start = heap_start;
+            max_heap_end = heap_end;
+        }
+    } while (next != 0);
+
+    max_heap_start = vm_page_round(max_heap_start);
+    max_heap_end = vm_page_trunc(max_heap_end);
+
+    if (max_heap_start >= max_heap_end)
+        boot_panic(biosmem_panic_setup_msg);
+
+    biosmem_heap_start = max_heap_start;
+    biosmem_heap_end = max_heap_end;
+    biosmem_heap_cur = biosmem_heap_end;
+}
+
+void __boot
+biosmem_bootstrap(struct multiboot_raw_info *mbi)
+{
+    phys_addr_t phys_start, phys_end;
+    int error;
+
+    if (mbi->flags & MULTIBOOT_LOADER_MMAP)
+        biosmem_map_build(mbi);
+    else
+        biosmem_map_build_simple(mbi);
+
+    biosmem_map_adjust();
+
+    phys_start = BIOSMEM_BASE;
+    phys_end = VM_PAGE_DMA_LIMIT;
+    error = biosmem_map_find_avail(&phys_start, &phys_end);
+
+    if (error)
+        boot_panic(biosmem_panic_noseg_msg);
+
+    biosmem_set_segment(VM_PAGE_SEG_DMA, phys_start, phys_end);
+
+    phys_start = VM_PAGE_DMA_LIMIT;
+#ifdef VM_PAGE_DMA32_LIMIT
+    phys_end = VM_PAGE_DMA32_LIMIT;
+    error = biosmem_map_find_avail(&phys_start, &phys_end);
+
+    if (error)
+        goto out;
+
+    biosmem_set_segment(VM_PAGE_SEG_DMA32, phys_start, phys_end);
+
+    phys_start = VM_PAGE_DMA32_LIMIT;
+#endif /* VM_PAGE_DMA32_LIMIT */
+    phys_end = VM_PAGE_DIRECTMAP_LIMIT;
+    error = biosmem_map_find_avail(&phys_start, &phys_end);
+
+    if (error)
+        goto out;
+
+    biosmem_set_segment(VM_PAGE_SEG_DIRECTMAP, phys_start, phys_end);
+
+    phys_start = VM_PAGE_DIRECTMAP_LIMIT;
+    phys_end = VM_PAGE_HIGHMEM_LIMIT;
+    error = biosmem_map_find_avail(&phys_start, &phys_end);
+
+    if (error)
+        goto out;
+
+    biosmem_set_segment(VM_PAGE_SEG_HIGHMEM, phys_start, phys_end);
+
+out:
+
+    /*
+     * The kernel and modules command lines will be memory mapped later
+     * during initialization. Their respective sizes must be saved.
+     */
+    biosmem_save_cmdline_sizes(mbi);
+    biosmem_setup_allocator(mbi);
+}
+
+void * __boot
+biosmem_bootalloc(unsigned int nr_pages)
+{
+    unsigned long addr, size;
+
+    size = vm_page_ptoa(nr_pages);
+
+    if (size == 0)
+        boot_panic(biosmem_panic_inval_msg);
+
+    /* Top-down allocation to avoid unnecessarily filling DMA segments */
+    addr = biosmem_heap_cur - size;
+
+    if ((addr < biosmem_heap_start) || (addr > biosmem_heap_cur))
+        boot_panic(biosmem_panic_nomem_msg);
+
+    biosmem_heap_cur = addr;
+    return boot_memset((void *)addr, 0, size);
+}
+
+phys_addr_t __boot
+biosmem_directmap_size(void)
+{
+    if (biosmem_segment_size(VM_PAGE_SEG_DIRECTMAP) != 0)
+        return biosmem_segment_end(VM_PAGE_SEG_DIRECTMAP);
+    else if (biosmem_segment_size(VM_PAGE_SEG_DMA32) != 0)
+        return biosmem_segment_end(VM_PAGE_SEG_DMA32);
+    else
+        return biosmem_segment_end(VM_PAGE_SEG_DMA);
+}
+
+static const char * __init
+biosmem_type_desc(unsigned int type)
+{
+    switch (type) {
+    case BIOSMEM_TYPE_AVAILABLE:
+        return "available";
+    case BIOSMEM_TYPE_RESERVED:
+        return "reserved";
+    case BIOSMEM_TYPE_ACPI:
+        return "ACPI";
+    case BIOSMEM_TYPE_NVS:
+        return "ACPI NVS";
+    case BIOSMEM_TYPE_UNUSABLE:
+        return "unusable";
+    default:
+        return "unknown (reserved)";
+    }
+}
+
+static void __init
+biosmem_map_show(void)
+{
+    const struct biosmem_map_entry *entry, *end;
+
+    printk("biosmem: physical memory map:\n");
+
+    for (entry = biosmem_map, end = entry + biosmem_map_size;
+         entry < end;
+         entry++)
+        printk("biosmem: %018llx:%018llx, %s\n", entry->base_addr,
+               entry->base_addr + entry->length,
+               biosmem_type_desc(entry->type));
+
+    printk("biosmem: heap: %x-%x\n", biosmem_heap_start, biosmem_heap_end);
+}
+
+static void __init
+biosmem_load_segment(struct biosmem_segment *seg, uint64_t max_phys_end,
+                     phys_addr_t phys_start, phys_addr_t phys_end,
+                     phys_addr_t avail_start, phys_addr_t avail_end)
+{
+    unsigned int seg_index;
+
+    seg_index = seg - biosmem_segments;
+
+    if (phys_end > max_phys_end) {
+        if (max_phys_end <= phys_start) {
+            printk("biosmem: warning: segment %s physically unreachable, "
+                   "not loaded\n", vm_page_seg_name(seg_index));
+            return;
+        }
+
+        printk("biosmem: warning: segment %s truncated to %#llx\n",
+               vm_page_seg_name(seg_index), max_phys_end);
+        phys_end = max_phys_end;
+    }
+
+    if ((avail_start < phys_start) || (avail_start > phys_end))
+        avail_start = phys_start;
+
+    if ((avail_end < phys_start) || (avail_end > phys_end))
+        avail_end = phys_end;
+
+    seg->avail_start = avail_start;
+    seg->avail_end = avail_end;
+    vm_page_load(seg_index, phys_start, phys_end, avail_start, avail_end);
+}
+
+void __init
+biosmem_setup(void)
+{
+    uint64_t max_phys_end;
+    struct biosmem_segment *seg;
+    struct cpu *cpu;
+    unsigned int i;
+
+    biosmem_map_show();
+
+    cpu = cpu_current();
+    max_phys_end = (cpu->phys_addr_width == 0)
+                   ? (uint64_t)-1
+                   : (uint64_t)1 << cpu->phys_addr_width;
+
+    for (i = 0; i < ARRAY_SIZE(biosmem_segments); i++) {
+        if (biosmem_segment_size(i) == 0)
+            break;
+
+        seg = &biosmem_segments[i];
+        biosmem_load_segment(seg, max_phys_end, seg->start, seg->end,
+                             biosmem_heap_start, biosmem_heap_cur);
+    }
+}
+
+static void __init
+biosmem_free_usable_range(phys_addr_t start, phys_addr_t end)
+{
+    struct vm_page *page;
+
+    printk("biosmem: release to vm_page: %llx-%llx (%lluk)\n",
+           (unsigned long long)start, (unsigned long long)end,
+           (unsigned long long)((end - start) >> 10));
+
+    while (start < end) {
+        page = vm_page_lookup(start);
+        assert(page != NULL);
+        vm_page_manage(page);
+        start += PAGE_SIZE;
+    }
+}
+
+static void __init
+biosmem_free_usable_update_start(phys_addr_t *start, phys_addr_t res_start,
+                                 phys_addr_t res_end)
+{
+    if ((*start >= res_start) && (*start < res_end))
+        *start = res_end;
+}
+
+static phys_addr_t __init
+biosmem_free_usable_start(phys_addr_t start)
+{
+    const struct biosmem_segment *seg;
+    unsigned int i;
+
+    biosmem_free_usable_update_start(&start, (unsigned long)&_boot,
+                                     BOOT_VTOP((unsigned long)&_end));
+    biosmem_free_usable_update_start(&start, biosmem_heap_start,
+                                     biosmem_heap_end);
+
+    for (i = 0; i < ARRAY_SIZE(biosmem_segments); i++) {
+        seg = &biosmem_segments[i];
+        biosmem_free_usable_update_start(&start, seg->avail_start,
+                                         seg->avail_end);
+    }
+
+    return start;
+}
+
+static int __init
+biosmem_free_usable_reserved(phys_addr_t addr)
+{
+    const struct biosmem_segment *seg;
+    unsigned int i;
+
+    if ((addr >= (unsigned long)&_boot)
+        && (addr < BOOT_VTOP((unsigned long)&_end)))
+        return 1;
+
+    if ((addr >= biosmem_heap_start) && (addr < biosmem_heap_end))
+        return 1;
+
+    for (i = 0; i < ARRAY_SIZE(biosmem_segments); i++) {
+        seg = &biosmem_segments[i];
+
+        if ((addr >= seg->avail_start) && (addr < seg->avail_end))
+            return 1;
+    }
+
+    return 0;
+}
+
+static phys_addr_t __init
+biosmem_free_usable_end(phys_addr_t start, phys_addr_t entry_end)
+{
+    while (start < entry_end) {
+        if (biosmem_free_usable_reserved(start))
+            break;
+
+        start += PAGE_SIZE;
+    }
+
+    return start;
+}
+
+static void __init
+biosmem_free_usable_entry(phys_addr_t start, phys_addr_t end)
+{
+    phys_addr_t entry_end;
+
+    entry_end = end;
+
+    for (;;) {
+        start = biosmem_free_usable_start(start);
+
+        if (start >= entry_end)
+            return;
+
+        end = biosmem_free_usable_end(start, entry_end);
+        biosmem_free_usable_range(start, end);
+        start = end;
+    }
+}
+
+void __init
+biosmem_free_usable(void)
+{
+    struct biosmem_map_entry *entry;
+    uint64_t start, end;
+    unsigned int i;
+
+    for (i = 0; i < biosmem_map_size; i++) {
+        entry = &biosmem_map[i];
+
+        if (entry->type != BIOSMEM_TYPE_AVAILABLE)
+            continue;
+
+        start = vm_page_round(entry->base_addr);
+
+        if (start >= VM_PAGE_HIGHMEM_LIMIT)
+            break;
+
+        end = vm_page_trunc(entry->base_addr + entry->length);
+
+        if (start < BIOSMEM_BASE)
+            start = BIOSMEM_BASE;
+
+        biosmem_free_usable_entry(start, end);
+    }
+}
diff --git a/i386/i386at/biosmem.h b/i386/i386at/biosmem.h
new file mode 100644
index 0000000..b32e027
--- /dev/null
+++ b/i386/i386at/biosmem.h
@@ -0,0 +1,84 @@
+/*
+ * Copyright (c) 2010-2014 Richard Braun.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef _X86_BIOSMEM_H
+#define _X86_BIOSMEM_H
+
+#include <kern/types.h>
+#include <machine/multiboot.h>
+
+/*
+ * Address where the address of the Extended BIOS Data Area segment can be
+ * found.
+ */
+#define BIOSMEM_EBDA_PTR 0x40e
+
+/*
+ * Significant low memory addresses.
+ *
+ * The first 64 KiB are reserved for various reasons (e.g. to preserve BIOS
+ * data and to work around data corruption on some hardware).
+ */
+#define BIOSMEM_BASE        0x010000
+#define BIOSMEM_BASE_END    0x0a0000
+#define BIOSMEM_EXT_ROM     0x0e0000
+#define BIOSMEM_ROM         0x0f0000
+#define BIOSMEM_END         0x100000
+
+/*
+ * Early initialization of the biosmem module.
+ *
+ * This function processes the given multiboot data for BIOS-provided
+ * memory information, and sets up a bootstrap physical page allocator.
+ *
+ * It is called before paging is enabled.
+ */
+void biosmem_bootstrap(struct multiboot_raw_info *mbi);
+
+/*
+ * Allocate contiguous physical pages during bootstrap.
+ *
+ * This function is called before paging is enabled. It should only be used
+ * to allocate initial page table pages. Those pages are later loaded into
+ * the VM system (as reserved pages) which means they can be freed like other
+ * regular pages. Users should fix up the type of those pages once the VM
+ * system is initialized.
+ */
+void * biosmem_bootalloc(unsigned int nr_pages);
+
+/*
+ * Return the amount of physical memory that can be directly mapped.
+ *
+ * This includes the size of both the DMA/DMA32 and DIRECTMAP segments.
+ */
+phys_addr_t biosmem_directmap_size(void);
+
+/*
+ * Set up physical memory based on the information obtained during bootstrap
+ * and load it in the VM system.
+ */
+void biosmem_setup(void);
+
+/*
+ * Free all usable memory.
+ *
+ * This includes ranges that weren't part of the bootstrap allocator initial
+ * heap, e.g. because they contained boot data.
+ */
+void biosmem_free_usable(void);
+
+#endif /* _X86_BIOSMEM_H */
diff --git a/vm/vm_page.c b/vm/vm_page.c
new file mode 100644
index 0000000..cc184ca
--- /dev/null
+++ b/vm/vm_page.c
@@ -0,0 +1,735 @@
+/*
+ * Copyright (c) 2010-2014 Richard Braun.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *
+ * This implementation uses the binary buddy system to manage its heap.
+ * Descriptions of the buddy system can be found in the following works :
+ * - "UNIX Internals: The New Frontiers", by Uresh Vahalia.
+ * - "Dynamic Storage Allocation: A Survey and Critical Review",
+ *    by Paul R. Wilson, Mark S. Johnstone, Michael Neely, and David Boles.
+ *
+ * In addition, this allocator uses per-CPU pools of pages for order 0
+ * (i.e. single page) allocations. These pools act as caches (but are named
+ * differently to avoid confusion with CPU caches) that reduce contention on
+ * multiprocessor systems. When a pool is empty and cannot provide a page,
+ * it is filled by transferring multiple pages from the backend buddy system.
+ * The symmetric case is handled likewise.
+ */
+
+#include <kern/assert.h>
+#include <kern/init.h>
+#include <kern/list.h>
+#include <kern/macros.h>
+#include <kern/mutex.h>
+#include <kern/panic.h>
+#include <kern/param.h>
+#include <kern/printk.h>
+#include <kern/sprintf.h>
+#include <kern/stddef.h>
+#include <kern/string.h>
+#include <kern/thread.h>
+#include <kern/types.h>
+#include <machine/cpu.h>
+#include <machine/pmap.h>
+#include <vm/vm_kmem.h>
+#include <vm/vm_page.h>
+
+/*
+ * Number of free block lists per segment.
+ */
+#define VM_PAGE_NR_FREE_LISTS 11
+
+/*
+ * The size of a CPU pool is computed by dividing the number of pages in its
+ * containing segment by this value.
+ */
+#define VM_PAGE_CPU_POOL_RATIO 1024
+
+/*
+ * Maximum number of pages in a CPU pool.
+ */
+#define VM_PAGE_CPU_POOL_MAX_SIZE 128
+
+/*
+ * The transfer size of a CPU pool is computed by dividing the pool size by
+ * this value.
+ */
+#define VM_PAGE_CPU_POOL_TRANSFER_RATIO 2
+
+/*
+ * Per-processor cache of pages.
+ */
+struct vm_page_cpu_pool {
+    struct mutex lock;
+    int size;
+    int transfer_size;
+    int nr_pages;
+    struct list pages;
+} __aligned(CPU_L1_SIZE);
+
+/*
+ * Special order value for pages that aren't in a free list. Such pages are
+ * either allocated, or part of a free block of pages but not the head page.
+ */
+#define VM_PAGE_ORDER_UNLISTED ((unsigned short)-1)
+
+/*
+ * Doubly-linked list of free blocks.
+ */
+struct vm_page_free_list {
+    unsigned long size;
+    struct list blocks;
+};
+
+/*
+ * Segment name buffer size.
+ */
+#define VM_PAGE_NAME_SIZE 16
+
+/*
+ * Segment of contiguous memory.
+ */
+struct vm_page_seg {
+    struct vm_page_cpu_pool cpu_pools[MAX_CPUS];
+
+    phys_addr_t start;
+    phys_addr_t end;
+    struct vm_page *pages;
+    struct vm_page *pages_end;
+    struct mutex lock;
+    struct vm_page_free_list free_lists[VM_PAGE_NR_FREE_LISTS];
+    unsigned long nr_free_pages;
+};
+
+/*
+ * Bootstrap information about a segment.
+ */
+struct vm_page_boot_seg {
+    phys_addr_t start;
+    phys_addr_t end;
+    phys_addr_t avail_start;
+    phys_addr_t avail_end;
+};
+
+static int vm_page_is_ready __read_mostly;
+
+/*
+ * Segment table.
+ *
+ * The system supports a maximum of 4 segments :
+ *  - DMA: suitable for DMA
+ *  - DMA32: suitable for DMA when devices support 32-bits addressing
+ *  - DIRECTMAP: direct physical mapping, allows direct access from
+ *    the kernel with a simple offset translation
+ *  - HIGHMEM: must be mapped before it can be accessed
+ *
+ * Segments are ordered by priority, 0 being the lowest priority. Their
+ * relative priorities are DMA < DMA32 < DIRECTMAP < HIGHMEM. Some segments
+ * may actually be aliases for others, e.g. if DMA is always possible from
+ * the direct physical mapping, DMA and DMA32 are aliases for DIRECTMAP,
+ * in which case the segment table contains DIRECTMAP and HIGHMEM only.
+ */
+static struct vm_page_seg vm_page_segs[VM_PAGE_MAX_SEGS];
+
+/*
+ * Bootstrap segment table.
+ */
+static struct vm_page_boot_seg vm_page_boot_segs[VM_PAGE_MAX_SEGS] __initdata;
+
+/*
+ * Number of loaded segments.
+ */
+static unsigned int vm_page_segs_size __read_mostly;
+
+static void __init
+vm_page_init(struct vm_page *page, unsigned short seg_index, phys_addr_t pa)
+{
+    memset(page, 0, sizeof(*page));
+    page->type = VM_PAGE_RESERVED;
+    page->seg_index = seg_index;
+    page->order = VM_PAGE_ORDER_UNLISTED;
+    page->phys_addr = pa;
+}
+
+void
+vm_page_set_type(struct vm_page *page, unsigned int order, unsigned short type)
+{
+    unsigned int i, nr_pages;
+
+    nr_pages = 1 << order;
+
+    for (i = 0; i < nr_pages; i++)
+        page[i].type = type;
+}
+
+static void __init
+vm_page_free_list_init(struct vm_page_free_list *free_list)
+{
+    free_list->size = 0;
+    list_init(&free_list->blocks);
+}
+
+static inline void
+vm_page_free_list_insert(struct vm_page_free_list *free_list,
+                         struct vm_page *page)
+{
+    assert(page->order == VM_PAGE_ORDER_UNLISTED);
+
+    free_list->size++;
+    list_insert_head(&free_list->blocks, &page->node);
+}
+
+static inline void
+vm_page_free_list_remove(struct vm_page_free_list *free_list,
+                         struct vm_page *page)
+{
+    assert(page->order != VM_PAGE_ORDER_UNLISTED);
+
+    free_list->size--;
+    list_remove(&page->node);
+}
+
+static struct vm_page *
+vm_page_seg_alloc_from_buddy(struct vm_page_seg *seg, unsigned int order)
+{
+    struct vm_page_free_list *free_list = free_list;
+    struct vm_page *page, *buddy;
+    unsigned int i;
+
+    assert(order < VM_PAGE_NR_FREE_LISTS);
+
+    for (i = order; i < VM_PAGE_NR_FREE_LISTS; i++) {
+        free_list = &seg->free_lists[i];
+
+        if (free_list->size != 0)
+            break;
+    }
+
+    if (i == VM_PAGE_NR_FREE_LISTS)
+        return NULL;
+
+    page = list_first_entry(&free_list->blocks, struct vm_page, node);
+    vm_page_free_list_remove(free_list, page);
+    page->order = VM_PAGE_ORDER_UNLISTED;
+
+    while (i > order) {
+        i--;
+        buddy = &page[1 << i];
+        vm_page_free_list_insert(&seg->free_lists[i], buddy);
+        buddy->order = i;
+    }
+
+    seg->nr_free_pages -= (1 << order);
+    return page;
+}
+
+static void
+vm_page_seg_free_to_buddy(struct vm_page_seg *seg, struct vm_page *page,
+                          unsigned int order)
+{
+    struct vm_page *buddy;
+    phys_addr_t pa, buddy_pa;
+    unsigned int nr_pages;
+
+    assert(page >= seg->pages);
+    assert(page < seg->pages_end);
+    assert(page->order == VM_PAGE_ORDER_UNLISTED);
+    assert(order < VM_PAGE_NR_FREE_LISTS);
+
+    nr_pages = (1 << order);
+    pa = page->phys_addr;
+
+    while (order < (VM_PAGE_NR_FREE_LISTS - 1)) {
+        buddy_pa = pa ^ vm_page_ptoa(1 << order);
+
+        if ((buddy_pa < seg->start) || (buddy_pa >= seg->end))
+            break;
+
+        buddy = &seg->pages[vm_page_atop(buddy_pa - seg->start)];
+
+        if (buddy->order != order)
+            break;
+
+        vm_page_free_list_remove(&seg->free_lists[order], buddy);
+        buddy->order = VM_PAGE_ORDER_UNLISTED;
+        order++;
+        pa &= -vm_page_ptoa(1 << order);
+        page = &seg->pages[vm_page_atop(pa - seg->start)];
+    }
+
+    vm_page_free_list_insert(&seg->free_lists[order], page);
+    page->order = order;
+    seg->nr_free_pages += nr_pages;
+}
+
+static void __init
+vm_page_cpu_pool_init(struct vm_page_cpu_pool *cpu_pool, int size)
+{
+    mutex_init(&cpu_pool->lock);
+    cpu_pool->size = size;
+    cpu_pool->transfer_size = (size + VM_PAGE_CPU_POOL_TRANSFER_RATIO - 1)
+                              / VM_PAGE_CPU_POOL_TRANSFER_RATIO;
+    cpu_pool->nr_pages = 0;
+    list_init(&cpu_pool->pages);
+}
+
+static inline struct vm_page_cpu_pool *
+vm_page_cpu_pool_get(struct vm_page_seg *seg)
+{
+    return &seg->cpu_pools[cpu_id()];
+}
+
+static inline struct vm_page *
+vm_page_cpu_pool_pop(struct vm_page_cpu_pool *cpu_pool)
+{
+    struct vm_page *page;
+
+    assert(cpu_pool->nr_pages != 0);
+    cpu_pool->nr_pages--;
+    page = list_first_entry(&cpu_pool->pages, struct vm_page, node);
+    list_remove(&page->node);
+    return page;
+}
+
+static inline void
+vm_page_cpu_pool_push(struct vm_page_cpu_pool *cpu_pool, struct vm_page *page)
+{
+    assert(cpu_pool->nr_pages < cpu_pool->size);
+    cpu_pool->nr_pages++;
+    list_insert_head(&cpu_pool->pages, &page->node);
+}
+
+static int
+vm_page_cpu_pool_fill(struct vm_page_cpu_pool *cpu_pool,
+                      struct vm_page_seg *seg)
+{
+    struct vm_page *page;
+    int i;
+
+    assert(cpu_pool->nr_pages == 0);
+
+    mutex_lock(&seg->lock);
+
+    for (i = 0; i < cpu_pool->transfer_size; i++) {
+        page = vm_page_seg_alloc_from_buddy(seg, 0);
+
+        if (page == NULL)
+            break;
+
+        vm_page_cpu_pool_push(cpu_pool, page);
+    }
+
+    mutex_unlock(&seg->lock);
+
+    return i;
+}
+
+static void
+vm_page_cpu_pool_drain(struct vm_page_cpu_pool *cpu_pool,
+                       struct vm_page_seg *seg)
+{
+    struct vm_page *page;
+    int i;
+
+    assert(cpu_pool->nr_pages == cpu_pool->size);
+
+    mutex_lock(&seg->lock);
+
+    for (i = cpu_pool->transfer_size; i > 0; i--) {
+        page = vm_page_cpu_pool_pop(cpu_pool);
+        vm_page_seg_free_to_buddy(seg, page, 0);
+    }
+
+    mutex_unlock(&seg->lock);
+}
+
+static phys_addr_t __init
+vm_page_seg_size(struct vm_page_seg *seg)
+{
+    return seg->end - seg->start;
+}
+
+static int __init
+vm_page_seg_compute_pool_size(struct vm_page_seg *seg)
+{
+    phys_addr_t size;
+
+    size = vm_page_atop(vm_page_seg_size(seg)) / VM_PAGE_CPU_POOL_RATIO;
+
+    if (size == 0)
+        size = 1;
+    else if (size > VM_PAGE_CPU_POOL_MAX_SIZE)
+        size = VM_PAGE_CPU_POOL_MAX_SIZE;
+
+    return size;
+}
+
+static void __init
+vm_page_seg_init(struct vm_page_seg *seg, phys_addr_t start, phys_addr_t end,
+                 struct vm_page *pages)
+{
+    phys_addr_t pa;
+    int pool_size;
+    unsigned int i;
+
+    seg->start = start;
+    seg->end = end;
+    pool_size = vm_page_seg_compute_pool_size(seg);
+
+    for (i = 0; i < ARRAY_SIZE(seg->cpu_pools); i++)
+        vm_page_cpu_pool_init(&seg->cpu_pools[i], pool_size);
+
+    seg->pages = pages;
+    seg->pages_end = pages + vm_page_atop(vm_page_seg_size(seg));
+    mutex_init(&seg->lock);
+
+    for (i = 0; i < ARRAY_SIZE(seg->free_lists); i++)
+        vm_page_free_list_init(&seg->free_lists[i]);
+
+    seg->nr_free_pages = 0;
+    i = seg - vm_page_segs;
+
+    for (pa = seg->start; pa < seg->end; pa += PAGE_SIZE)
+        vm_page_init(&pages[vm_page_atop(pa - seg->start)], i, pa);
+}
+
+static struct vm_page *
+vm_page_seg_alloc(struct vm_page_seg *seg, unsigned int order,
+                  unsigned short type)
+{
+    struct vm_page_cpu_pool *cpu_pool;
+    struct vm_page *page;
+    int filled;
+
+    assert(order < VM_PAGE_NR_FREE_LISTS);
+
+    if (order == 0) {
+        thread_pin();
+        cpu_pool = vm_page_cpu_pool_get(seg);
+        mutex_lock(&cpu_pool->lock);
+
+        if (cpu_pool->nr_pages == 0) {
+            filled = vm_page_cpu_pool_fill(cpu_pool, seg);
+
+            if (!filled) {
+                mutex_unlock(&cpu_pool->lock);
+                thread_unpin();
+                return NULL;
+            }
+        }
+
+        page = vm_page_cpu_pool_pop(cpu_pool);
+        mutex_unlock(&cpu_pool->lock);
+        thread_unpin();
+    } else {
+        mutex_lock(&seg->lock);
+        page = vm_page_seg_alloc_from_buddy(seg, order);
+        mutex_unlock(&seg->lock);
+    }
+
+    assert(page->type == VM_PAGE_FREE);
+    vm_page_set_type(page, order, type);
+    return page;
+}
+
+static void
+vm_page_seg_free(struct vm_page_seg *seg, struct vm_page *page,
+                 unsigned int order)
+{
+    struct vm_page_cpu_pool *cpu_pool;
+
+    assert(page->type != VM_PAGE_FREE);
+    assert(order < VM_PAGE_NR_FREE_LISTS);
+
+    vm_page_set_type(page, order, VM_PAGE_FREE);
+
+    if (order == 0) {
+        thread_pin();
+        cpu_pool = vm_page_cpu_pool_get(seg);
+        mutex_lock(&cpu_pool->lock);
+
+        if (cpu_pool->nr_pages == cpu_pool->size)
+            vm_page_cpu_pool_drain(cpu_pool, seg);
+
+        vm_page_cpu_pool_push(cpu_pool, page);
+        mutex_unlock(&cpu_pool->lock);
+        thread_unpin();
+    } else {
+        mutex_lock(&seg->lock);
+        vm_page_seg_free_to_buddy(seg, page, order);
+        mutex_unlock(&seg->lock);
+    }
+}
+
+void __init
+vm_page_load(unsigned int seg_index, phys_addr_t start, phys_addr_t end,
+             phys_addr_t avail_start, phys_addr_t avail_end)
+{
+    struct vm_page_boot_seg *seg;
+
+    assert(seg_index < ARRAY_SIZE(vm_page_boot_segs));
+    assert(vm_page_aligned(start));
+    assert(vm_page_aligned(end));
+    assert(vm_page_aligned(avail_start));
+    assert(vm_page_aligned(avail_end));
+    assert(start < end);
+    assert(start <= avail_start);
+    assert(avail_end <= end);
+    assert(vm_page_segs_size < ARRAY_SIZE(vm_page_boot_segs));
+
+    seg = &vm_page_boot_segs[seg_index];
+    seg->start = start;
+    seg->end = end;
+    seg->avail_start = avail_start;
+    seg->avail_end = avail_end;
+    vm_page_segs_size++;
+}
+
+int
+vm_page_ready(void)
+{
+    return vm_page_is_ready;
+}
+
+static unsigned int
+vm_page_select_alloc_seg(unsigned int selector)
+{
+    unsigned int seg_index;
+
+    switch (selector) {
+    case VM_PAGE_SEL_DMA:
+        seg_index = VM_PAGE_SEG_DMA;
+        break;
+    case VM_PAGE_SEL_DMA32:
+        seg_index = VM_PAGE_SEG_DMA32;
+        break;
+    case VM_PAGE_SEL_DIRECTMAP:
+        seg_index = VM_PAGE_SEG_DIRECTMAP;
+        break;
+    case VM_PAGE_SEL_HIGHMEM:
+        seg_index = VM_PAGE_SEG_HIGHMEM;
+        break;
+    default:
+        panic("vm_page: invalid selector");
+    }
+
+    return MIN(vm_page_segs_size - 1, seg_index);
+}
+
+static int __init
+vm_page_boot_seg_loaded(const struct vm_page_boot_seg *seg)
+{
+    return (seg->end != 0);
+}
+
+static void __init
+vm_page_check_boot_segs(void)
+{
+    unsigned int i;
+    int expect_loaded;
+
+    if (vm_page_segs_size == 0)
+        panic("vm_page: no physical memory loaded");
+
+    for (i = 0; i < ARRAY_SIZE(vm_page_boot_segs); i++) {
+        expect_loaded = (i < vm_page_segs_size);
+
+        if (vm_page_boot_seg_loaded(&vm_page_boot_segs[i]) == expect_loaded)
+            continue;
+
+        panic("vm_page: invalid boot segment table");
+    }
+}
+
+static phys_addr_t __init
+vm_page_boot_seg_size(struct vm_page_boot_seg *seg)
+{
+    return seg->end - seg->start;
+}
+
+static phys_addr_t __init
+vm_page_boot_seg_avail_size(struct vm_page_boot_seg *seg)
+{
+    return seg->avail_end - seg->avail_start;
+}
+
+static void * __init
+vm_page_bootalloc(size_t size)
+{
+    struct vm_page_boot_seg *seg;
+    phys_addr_t pa;
+    unsigned int i;
+
+    for (i = vm_page_select_alloc_seg(VM_PAGE_SEL_DIRECTMAP);
+         i < vm_page_segs_size;
+         i--) {
+        seg = &vm_page_boot_segs[i];
+
+        if (size <= vm_page_boot_seg_avail_size(seg)) {
+            pa = seg->avail_start;
+            seg->avail_start += vm_page_round(size);
+            return (void *)vm_page_direct_va(pa);
+        }
+    }
+
+    panic("vm_page: no physical memory available");
+}
+
+void __init
+vm_page_setup(void)
+{
+    struct vm_page_boot_seg *boot_seg;
+    struct vm_page_seg *seg;
+    struct vm_page *table, *page, *end;
+    size_t nr_pages, table_size;
+    unsigned long va;
+    unsigned int i;
+    phys_addr_t pa;
+
+    vm_page_check_boot_segs();
+
+    /*
+     * Compute the page table size.
+     */
+    nr_pages = 0;
+
+    for (i = 0; i < vm_page_segs_size; i++)
+        nr_pages += vm_page_atop(vm_page_boot_seg_size(&vm_page_boot_segs[i]));
+
+    table_size = vm_page_round(nr_pages * sizeof(struct vm_page));
+    printk("vm_page: page table size: %zu entries (%zuk)\n", nr_pages,
+           table_size >> 10);
+    table = vm_page_bootalloc(table_size);
+    va = (unsigned long)table;
+
+    /*
+     * Initialize the segments, associating them to the page table. When
+     * the segments are initialized, all their pages are set allocated.
+     * Pages are then released, which populates the free lists.
+     */
+    for (i = 0; i < vm_page_segs_size; i++) {
+        seg = &vm_page_segs[i];
+        boot_seg = &vm_page_boot_segs[i];
+        vm_page_seg_init(seg, boot_seg->start, boot_seg->end, table);
+        page = seg->pages + vm_page_atop(boot_seg->avail_start
+                                         - boot_seg->start);
+        end = seg->pages + vm_page_atop(boot_seg->avail_end
+                                        - boot_seg->start);
+
+        while (page < end) {
+            page->type = VM_PAGE_FREE;
+            vm_page_seg_free_to_buddy(seg, page, 0);
+            page++;
+        }
+
+        table += vm_page_atop(vm_page_seg_size(seg));
+    }
+
+    while (va < (unsigned long)table) {
+        pa = vm_page_direct_pa(va);
+        page = vm_page_lookup(pa);
+        assert((page != NULL) && (page->type == VM_PAGE_RESERVED));
+        page->type = VM_PAGE_TABLE;
+        va += PAGE_SIZE;
+    }
+
+    vm_page_is_ready = 1;
+}
+
+void __init
+vm_page_manage(struct vm_page *page)
+{
+    assert(page->seg_index < ARRAY_SIZE(vm_page_segs));
+    assert(page->type == VM_PAGE_RESERVED);
+
+    vm_page_set_type(page, 0, VM_PAGE_FREE);
+    vm_page_seg_free_to_buddy(&vm_page_segs[page->seg_index], page, 0);
+}
+
+struct vm_page *
+vm_page_lookup(phys_addr_t pa)
+{
+    struct vm_page_seg *seg;
+    unsigned int i;
+
+    for (i = 0; i < vm_page_segs_size; i++) {
+        seg = &vm_page_segs[i];
+
+        if ((pa >= seg->start) && (pa < seg->end))
+            return &seg->pages[vm_page_atop(pa - seg->start)];
+    }
+
+    return NULL;
+}
+
+struct vm_page *
+vm_page_alloc(unsigned int order, unsigned int selector, unsigned short type)
+{
+    struct vm_page *page;
+    unsigned int i;
+
+    for (i = vm_page_select_alloc_seg(selector); i < vm_page_segs_size; i--) {
+        page = vm_page_seg_alloc(&vm_page_segs[i], order, type);
+
+        if (page != NULL)
+            return page;
+    }
+
+    if (type == VM_PAGE_PMAP)
+        panic("vm_page: unable to allocate pmap page");
+
+    return NULL;
+}
+
+void
+vm_page_free(struct vm_page *page, unsigned int order)
+{
+    assert(page->seg_index < ARRAY_SIZE(vm_page_segs));
+
+    vm_page_seg_free(&vm_page_segs[page->seg_index], page, order);
+}
+
+const char *
+vm_page_seg_name(unsigned int seg_index)
+{
+    /* Don't use a switch statement since segments can be aliased */
+    if (seg_index == VM_PAGE_SEG_HIGHMEM)
+        return "HIGHMEM";
+    else if (seg_index == VM_PAGE_SEG_DIRECTMAP)
+        return "DIRECTMAP";
+    else if (seg_index == VM_PAGE_SEG_DMA32)
+        return "DMA32";
+    else if (seg_index == VM_PAGE_SEG_DMA)
+        return "DMA";
+    else
+        panic("vm_page: invalid segment index");
+}
+
+void
+vm_page_info(void)
+{
+    struct vm_page_seg *seg;
+    unsigned long pages;
+    unsigned int i;
+
+    for (i = 0; i < vm_page_segs_size; i++) {
+        seg = &vm_page_segs[i];
+        pages = (unsigned long)(seg->pages_end - seg->pages);
+        printk("vm_page: %s: pages: %lu (%luM), free: %lu (%luM)\n",
+               vm_page_seg_name(i), pages, pages >> (20 - PAGE_SHIFT),
+               seg->nr_free_pages, seg->nr_free_pages >> (20 - PAGE_SHIFT));
+    }
+}
diff --git a/vm/vm_page.h b/vm/vm_page.h
index e6a8c49..23c8c47 100644
--- a/vm/vm_page.h
+++ b/vm/vm_page.h
@@ -1,315 +1,195 @@
-/* 
- * Mach Operating System
- * Copyright (c) 1993-1988 Carnegie Mellon University
- * All Rights Reserved.
- * 
- * Permission to use, copy, modify and distribute this software and its
- * documentation is hereby granted, provided that both the copyright
- * notice and this permission notice appear in all copies of the
- * software, derivative works or modified versions, and any portions
- * thereof, and that both notices appear in supporting documentation.
- * 
- * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
- * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
- * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
- * 
- * Carnegie Mellon requests users of this software to return to
- * 
- *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
- *  School of Computer Science
- *  Carnegie Mellon University
- *  Pittsburgh PA 15213-3890
- * 
- * any improvements or extensions that they make and grant Carnegie Mellon
- * the rights to redistribute these changes.
- */
 /*
- *	File:	vm/vm_page.h
- *	Author:	Avadis Tevanian, Jr., Michael Wayne Young
- *	Date:	1985
+ * Copyright (c) 2010-2014 Richard Braun.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *
- *	Resident memory system definitions.
+ *
+ * Physical page management.
  */
 
-#ifndef	_VM_VM_PAGE_H_
-#define _VM_VM_PAGE_H_
-
-#include <mach/boolean.h>
-#include <mach/vm_prot.h>
-#include <mach/vm_param.h>
-#include <vm/vm_object.h>
-#include <vm/vm_types.h>
-#include <kern/queue.h>
-#include <kern/lock.h>
+#ifndef _VM_VM_PAGE_H
+#define _VM_VM_PAGE_H
 
+#include <kern/assert.h>
+#include <kern/list.h>
+#include <kern/log2.h>
 #include <kern/macros.h>
-#include <kern/sched_prim.h>	/* definitions of wait/wakeup */
+//#include <kern/param.h>
+//#include <kern/stddef.h>
+//#include <kern/types.h>
+#include <machine/pmap.h>
 
-#if	MACH_VM_DEBUG
-#include <mach_debug/hash_info.h>
-#endif
+/*
+ * Address/page conversion and rounding macros (not inline functions to
+ * be easily usable on both virtual and physical addresses, which may not
+ * have the same type size).
+ */
+#define vm_page_atop(addr)      ((addr) >> PAGE_SHIFT)
+#define vm_page_ptoa(page)      ((page) << PAGE_SHIFT)
+#define vm_page_trunc(addr)     P2ALIGN(addr, PAGE_SIZE)
+#define vm_page_round(addr)     P2ROUND(addr, PAGE_SIZE)
+#define vm_page_aligned(addr)   P2ALIGNED(addr, PAGE_SIZE)
 
 /*
- *	Management of resident (logical) pages.
- *
- *	A small structure is kept for each resident
- *	page, indexed by page number.  Each structure
- *	is an element of several lists:
- *
- *		A hash table bucket used to quickly
- *		perform object/offset lookups
- *
- *		A list of all pages for a given object,
- *		so they can be quickly deactivated at
- *		time of deallocation.
+ * Segment selectors.
  *
- *		An ordered list of pages due for pageout.
- *
- *	In addition, the structure contains the object
- *	and offset to which this page belongs (for pageout),
- *	and sundry status bits.
+ * Selector-to-segment-list translation table :
+ * DMA          DMA
+ * DMA32        DMA32 DMA
+ * DIRECTMAP    DIRECTMAP DMA32 DMA
+ * HIGHMEM      HIGHMEM DIRECTMAP DMA32 DMA
+ */
+#define VM_PAGE_SEL_DMA         0
+#define VM_PAGE_SEL_DMA32       1
+#define VM_PAGE_SEL_DIRECTMAP   2
+#define VM_PAGE_SEL_HIGHMEM     3
+
+/*
+ * Page usage types.
  *
- *	Fields in this structure are locked either by the lock on the
- *	object that the page belongs to (O) or by the lock on the page
- *	queues (P).  [Some fields require that both locks be held to
- *	change that field; holding either lock is sufficient to read.]
+ * Failing to allocate pmap pages will cause a kernel panic.
+ * TODO Obviously, this needs to be addressed, e.g. with a reserved pool of
+ * pages.
  */
+#define VM_PAGE_FREE        0   /* Page unused */
+#define VM_PAGE_RESERVED    1   /* Page reserved at boot time */
+#define VM_PAGE_TABLE       2   /* Page is part of the page table */
+#define VM_PAGE_PMAP        3   /* Page stores pmap-specific data */
+#define VM_PAGE_KMEM        4   /* Page is part of a kmem slab */
+#define VM_PAGE_OBJECT      5   /* Page is part of a VM object */
+#define VM_PAGE_KERNEL      6   /* Type for generic kernel allocations */
 
+/*
+ * Physical page descriptor.
+ */
 struct vm_page {
-	queue_chain_t	pageq;		/* queue info for FIFO
-					 * queue or free list (P) */
-	queue_chain_t	listq;		/* all pages in same object (O) */
-	struct vm_page	*next;		/* VP bucket link (O) */
-
-	vm_object_t	object;		/* which object am I in (O,P) */
-	vm_offset_t	offset;		/* offset into that object (O,P) */
-
-	unsigned int	wire_count:15,	/* how many wired down maps use me?
-					   (O&P) */
-	/* boolean_t */	inactive:1,	/* page is in inactive list (P) */
-			active:1,	/* page is in active list (P) */
-			laundry:1,	/* page is being cleaned now (P)*/
-			free:1,		/* page is on free list (P) */
-			reference:1,	/* page has been used (P) */
-			external:1,	/* page considered external (P) */
-			extcounted:1,   /* page counted in ext counts (P) */
-			busy:1,		/* page is in transit (O) */
-			wanted:1,	/* someone is waiting for page (O) */
-			tabled:1,	/* page is in VP table (O) */
-			fictitious:1,	/* Physical page doesn't exist (O) */
-			private:1,	/* Page should not be returned to
-					 *  the free list (O) */
-			absent:1,	/* Data has been requested, but is
-					 *  not yet available (O) */
-			error:1,	/* Data manager was unable to provide
-					 *  data due to error (O) */
-			dirty:1,	/* Page must be cleaned (O) */
-			precious:1,	/* Page is precious; data must be
-					 *  returned even if clean (O) */
-			overwriting:1;	/* Request to unlock has been made
-					 * without having data. (O)
-					 * [See vm_object_overwrite] */
-
-	vm_offset_t	phys_addr;	/* Physical address of page, passed
-					 *  to pmap_enter (read-only) */
-	vm_prot_t	page_lock;	/* Uses prohibited by data manager (O) */
-	vm_prot_t	unlock_request;	/* Outstanding unlock request (O) */
+    struct list node;
+    unsigned short type;
+    unsigned short seg_index;
+    unsigned short order;
+    phys_addr_t phys_addr;
+    void *slab_priv;
 };
 
+static inline unsigned short
+vm_page_type(const struct vm_page *page)
+{
+    return page->type;
+}
+
+void vm_page_set_type(struct vm_page *page, unsigned int order,
+                      unsigned short type);
+
+static inline unsigned int
+vm_page_order(size_t size)
+{
+    return iorder2(vm_page_atop(vm_page_round(size)));
+}
+
+static inline phys_addr_t
+vm_page_to_pa(const struct vm_page *page)
+{
+    return page->phys_addr;
+}
+
+static inline unsigned long
+vm_page_direct_va(phys_addr_t pa)
+{
+    assert(pa < VM_PAGE_DIRECTMAP_LIMIT);
+    return ((unsigned long)pa + VM_MIN_DIRECTMAP_ADDRESS);
+}
+
+static inline phys_addr_t
+vm_page_direct_pa(unsigned long va)
+{
+    assert(va >= VM_MIN_DIRECTMAP_ADDRESS);
+    assert(va < VM_MAX_DIRECTMAP_ADDRESS);
+    return (va - VM_MIN_DIRECTMAP_ADDRESS);
+}
+
+static inline void *
+vm_page_direct_ptr(const struct vm_page *page)
+{
+    return (void *)vm_page_direct_va(vm_page_to_pa(page));
+}
+
 /*
- *	For debugging, this macro can be defined to perform
- *	some useful check on a page structure.
+ * Load physical memory into the vm_page module at boot time.
+ *
+ * The avail_start and avail_end parameters are used to maintain a simple
+ * heap for bootstrap allocations.
+ *
+ * All addresses must be page-aligned. Segments can be loaded in any order.
  */
+void vm_page_load(unsigned int seg_index, phys_addr_t start, phys_addr_t end,
+                  phys_addr_t avail_start, phys_addr_t avail_end);
 
-#define VM_PAGE_CHECK(mem)
+/*
+ * Return true if the vm_page module is completely initialized, false
+ * otherwise, in which case only vm_page_bootalloc() can be used for
+ * allocations.
+ */
+int vm_page_ready(void);
 
 /*
- *	Each pageable resident page falls into one of three lists:
+ * Set up the vm_page module.
+ *
+ * Architecture-specific code must have loaded segments before calling this
+ * function. Segments must comply with the selector-to-segment-list table,
+ * e.g. HIGHMEM is loaded if and only if DIRECTMAP, DMA32 and DMA are loaded,
+ * notwithstanding segment aliasing.
  *
- *	free	
- *		Available for allocation now.
- *	inactive
- *		Not referenced in any map, but still has an
- *		object/offset-page mapping, and may be dirty.
- *		This is the list of pages that should be
- *		paged out next.
- *	active
- *		A list of pages which have been placed in
- *		at least one physical map.  This list is
- *		ordered, in LRU-like fashion.
+ * Once this function returns, the vm_page module is ready, and normal
+ * allocation functions can be used.
  */
-
-extern
-vm_page_t	vm_page_queue_free;	/* memory free queue */
-extern
-vm_page_t	vm_page_queue_fictitious;	/* fictitious free queue */
-extern
-queue_head_t	vm_page_queue_active;	/* active memory queue */
-extern
-queue_head_t	vm_page_queue_inactive;	/* inactive memory queue */
-
-extern
-int	vm_page_free_count;	/* How many pages are free? */
-extern
-int	vm_page_fictitious_count;/* How many fictitious pages are free? */
-extern
-int	vm_page_active_count;	/* How many pages are active? */
-extern
-int	vm_page_inactive_count;	/* How many pages are inactive? */
-extern
-int	vm_page_wire_count;	/* How many pages are wired? */
-extern
-int	vm_page_free_target;	/* How many do we want free? */
-extern
-int	vm_page_free_min;	/* When to wakeup pageout */
-extern
-int	vm_page_inactive_target;/* How many do we want inactive? */
-extern
-int	vm_page_free_reserved;	/* How many pages reserved to do pageout */
-extern
-int	vm_page_laundry_count;	/* How many pages being laundered? */
-extern
-int	vm_page_external_limit;	/* Max number of pages for external objects  */
-
-/* Only objects marked with the extcounted bit are included in this total.
-   Pages which we scan for possible pageout, but which are not actually
-   dirty, don't get considered against the external page limits any more
-   in this way.  */
-extern
-int	vm_page_external_count;	/* How many pages for external objects? */
-
-
-
-decl_simple_lock_data(extern,vm_page_queue_lock)/* lock on active and inactive
-						   page queues */
-decl_simple_lock_data(extern,vm_page_queue_free_lock)
-						/* lock on free page queue */
-
-extern unsigned int	vm_page_free_wanted;
-				/* how many threads are waiting for memory */
-
-extern vm_offset_t	vm_page_fictitious_addr;
-				/* (fake) phys_addr of fictitious pages */
-
-extern void		vm_page_bootstrap(
-	vm_offset_t	*startp,
-	vm_offset_t	*endp);
-extern void		vm_page_module_init(void);
-
-extern void		vm_page_create(
-	vm_offset_t	start,
-	vm_offset_t	end);
-extern vm_page_t	vm_page_lookup(
-	vm_object_t	object,
-	vm_offset_t	offset);
-extern vm_page_t	vm_page_grab_fictitious(void);
-extern void		vm_page_release_fictitious(vm_page_t);
-extern boolean_t	vm_page_convert(vm_page_t, boolean_t);
-extern void		vm_page_more_fictitious(void);
-extern vm_page_t	vm_page_grab(boolean_t);
-extern void		vm_page_release(vm_page_t, boolean_t);
-extern void		vm_page_wait(void (*)(void));
-extern vm_page_t	vm_page_alloc(
-	vm_object_t	object,
-	vm_offset_t	offset);
-extern void		vm_page_init(
-	vm_page_t	mem,
-	vm_offset_t	phys_addr);
-extern void		vm_page_free(vm_page_t);
-extern void		vm_page_activate(vm_page_t);
-extern void		vm_page_deactivate(vm_page_t);
-extern void		vm_page_rename(
-	vm_page_t	mem,
-	vm_object_t	new_object,
-	vm_offset_t	new_offset);
-extern void		vm_page_insert(
-	vm_page_t	mem,
-	vm_object_t	object,
-	vm_offset_t	offset);
-extern void		vm_page_remove(
-	vm_page_t	mem);
-
-extern void		vm_page_zero_fill(vm_page_t);
-extern void		vm_page_copy(vm_page_t src_m, vm_page_t dest_m);
-
-extern void		vm_page_wire(vm_page_t);
-extern void		vm_page_unwire(vm_page_t);
-
-#if	MACH_VM_DEBUG
-extern unsigned int	vm_page_info(
-	hash_info_bucket_t	*info,
-	unsigned int		count);
-#endif
+void vm_page_setup(void);
 
 /*
- *	Functions implemented as macros
+ * Make the given page managed by the vm_page module.
+ *
+ * If additional memory can be made usable after the VM system is initialized,
+ * it should be reported through this function.
  */
-
-#define PAGE_ASSERT_WAIT(m, interruptible)			\
-		MACRO_BEGIN					\
-		(m)->wanted = TRUE;				\
-		assert_wait((event_t) (m), (interruptible));	\
-		MACRO_END
-
-#define PAGE_WAKEUP_DONE(m)					\
-		MACRO_BEGIN					\
-		(m)->busy = FALSE;				\
-		if ((m)->wanted) {				\
-			(m)->wanted = FALSE;			\
-			thread_wakeup(((event_t) m));		\
-		}						\
-		MACRO_END
-
-#define PAGE_WAKEUP(m)						\
-		MACRO_BEGIN					\
-		if ((m)->wanted) {				\
-			(m)->wanted = FALSE;			\
-			thread_wakeup((event_t) (m));		\
-		}						\
-		MACRO_END
-
-#define VM_PAGE_FREE(p) 			\
-		MACRO_BEGIN			\
-		vm_page_lock_queues();		\
-		vm_page_free(p);		\
-		vm_page_unlock_queues();	\
-		MACRO_END
+void vm_page_manage(struct vm_page *page);
 
 /*
- *	Macro to be used in place of pmap_enter()
+ * Return the page descriptor for the given physical address.
  */
+struct vm_page * vm_page_lookup(phys_addr_t pa);
 
-#define PMAP_ENTER(pmap, virtual_address, page, protection, wired) \
-		MACRO_BEGIN					\
-		pmap_enter(					\
-			(pmap),					\
-			(virtual_address),			\
-			(page)->phys_addr,			\
-			(protection) & ~(page)->page_lock,	\
-			(wired)					\
-		 );						\
-		MACRO_END
+/*
+ * Allocate a block of 2^order physical pages.
+ *
+ * The selector is used to determine the segments from which allocation can
+ * be attempted.
+ */
+struct vm_page * vm_page_alloc(unsigned int order, unsigned int selector,
+                               unsigned short type);
 
-#define	VM_PAGE_WAIT(continuation)	vm_page_wait(continuation)
+/*
+ * Release a block of 2^order physical pages.
+ */
+void vm_page_free(struct vm_page *page, unsigned int order);
 
-#define vm_page_lock_queues()	simple_lock(&vm_page_queue_lock)
-#define vm_page_unlock_queues()	simple_unlock(&vm_page_queue_lock)
+/*
+ * Return the name of the given segment.
+ */
+const char * vm_page_seg_name(unsigned int seg_index);
 
-#define VM_PAGE_QUEUES_REMOVE(mem)				\
-	MACRO_BEGIN						\
-	if (mem->active) {					\
-		queue_remove(&vm_page_queue_active,		\
-			mem, vm_page_t, pageq);			\
-		mem->active = FALSE;				\
-		vm_page_active_count--;				\
-	}							\
-								\
-	if (mem->inactive) {					\
-		queue_remove(&vm_page_queue_inactive,		\
-			mem, vm_page_t, pageq);			\
-		mem->inactive = FALSE;				\
-		vm_page_inactive_count--;			\
-	}							\
-	MACRO_END
+/*
+ * Display internal information about the module.
+ */
+void vm_page_info(void);
 
-#endif	/* _VM_VM_PAGE_H_ */
+#endif /* _VM_VM_PAGE_H */