diff --git a/kernel/arch/arm/flags.cmake b/kernel/arch/arm/flags.cmake
index 7b70c3e..ea89365 100644
--- a/kernel/arch/arm/flags.cmake
+++ b/kernel/arch/arm/flags.cmake
@@ -1,3 +1,3 @@
-SET(PLATFORM_C_FLAGS "-I../../kernel/arch/arm/include")
-SET(PLATFORM_CXX_FLAGS "${PLATFORM_C_FLAGS}")
-SET(PLATFORM_ASM_FLAGS "${PLATFORM_C_FLAGS}")
+SET(ISA_C_FLAGS "-I../../kernel/arch/arm/include")
+SET(ISA_CXX_FLAGS "${ISA_C_FLAGS}")
+SET(ISA_ASM_FLAGS "${ISA_C_FLAGS}")
diff --git a/kernel/arch/x86/include/paging.h b/kernel/arch/x86/include/paging.h
new file mode 100644
index 0000000..2fa0dbc
--- /dev/null
+++ b/kernel/arch/x86/include/paging.h
@@ -0,0 +1,52 @@
+#pragma once
+#include <stdint.h>
+#include <pmm.hpp>
+#include <regs.h>
+#include <paging.hpp>
+struct pagedir {
+    bool active:1;
+    bool writeable:1;
+    bool privileged:1;
+    bool no_write_cache:1;
+    bool no_read_cache:1;
+    bool accessed:1;
+    bool ignored:1;
+    bool size:1;
+    bool ignored2:1;
+    uint8_t ignored3:3;
+    phys_t pagetable:20;
+}__attribute__((packed));
+static_assert(sizeof(pagedir)==4);
+
+struct pagetbl {
+    bool active:1;
+    bool writeable:1;
+    bool privileged:1;
+    bool no_write_cache:1;
+    bool no_read_cache:1;
+    bool accessed:1;
+    bool written:1;
+    bool pat:1;
+    bool no_flush_after_cr3:1;
+    uint8_t ignored:2;
+    bool lazy:1;
+    phys_t page:20;
+}__attribute__((packed));
+static_assert(sizeof(pagetbl)==4);
+
+struct paging_context_x86: public paging_context {
+    phys_t pagedir_addr;
+    paging_context_x86();
+    virtual ~paging_context_x86();
+    virtual void switch_context();
+    virtual void map_pagetable(struct paging_context *);
+    virtual void *mmap(phys_t addr, void *dest, protection prot=protection::RW, bool lazy=true);
+    virtual void munmap(void *addr);
+    virtual bool is_mapped(void *addr);
+    virtual void mprotect(void *addr, protection prot);
+    virtual bool has_no_exec();
+    virtual void *get_exception_address(cpu_state *cpu);
+    virtual bool lazymap(void *addr, cpu_state *cpu);
+    pagedir * operator*();
+    pagetbl * operator[](phys_t);
+};
diff --git a/kernel/arch/x86/paging.cpp b/kernel/arch/x86/paging.cpp
new file mode 100644
index 0000000..2c77eda
--- /dev/null
+++ b/kernel/arch/x86/paging.cpp
@@ -0,0 +1,347 @@
+#include <paging.h>
+#include <base.hpp>
+extern int kernel_start;
+extern int kernel_end;
+paging_context_x86::paging_context_x86(): paging_context() {
+    *pmm >> pagedir_addr;
+    if(context_enabled) {
+        //Copy System section (first 256 entries) over to the new context
+        current_context->mmap(pagedir_addr, (void*)0x401000, protection::RW, false);
+        pagedir *src=(pagedir *)0x400000;
+        pagedir *dest=(pagedir *)0x401000;
+        for(int i=0;i<256;i++)
+            dest[i]=src[i];
+        for(int i=256;i<1024;i++)
+            dest[i].active=false;
+        //remap self-map correctly
+        dest[1].active=false;
+        dest[2].active=false;
+        dest[3].active=false;
+        phys_t selfmap_meta;
+        *pmm >> selfmap_meta;
+
+        dest[1].pagetable = selfmap_meta >> 12;
+        dest[1].writeable = true;
+        dest[1].privileged = false;
+        dest[1].no_write_cache = true;
+        dest[1].no_read_cache = false;
+        dest[1].size = false;
+        dest[1].active = true;
+
+        phys_t selfmap;
+        *pmm >> selfmap;
+        dest[2].pagetable = selfmap >> 12;
+        dest[2].writeable = true;
+        dest[2].privileged = false;
+        dest[2].no_write_cache = true;
+        dest[2].no_read_cache = false;
+        dest[2].size = false;
+        dest[2].active = true;
+
+        current_context->map_pagetable(this);
+
+        //Remap all parts of the system
+        for(int i=0;i<256;i++) {
+            if(!src[i].active)
+                continue;
+            if(i == 1 || i == 2 || i == 3)
+                continue;
+            pagetbl *pagetbl_start = (pagetbl *)(0x800000 + i << 22);
+            for(int j=0;j<1024;j++) {
+                if(!pagetbl_start[j].active)
+                    continue;
+                mmap(pagetbl_start[j].page << 12, pagetbl_start+1024, protection::RW, false);
+
+            }
+        }
+        return;
+    }
+    //Map the entire kernel
+    pagedir *context=(pagedir *)pagedir_addr;
+    for(int i=0;i<1024;i++)
+        context[i].active=false;
+    phys_t kernel_tbl;
+    *pmm >> kernel_tbl;
+    context[0].pagetable=kernel_tbl >> 12;
+    context[0].writeable=true;
+    context[0].privileged=false;
+    context[0].no_write_cache=false;
+    context[0].no_read_cache=false;
+    context[0].size=false;
+    context[0].active=true;
+
+    pagetbl *kerneltbl = (pagetbl *)kernel_tbl;
+    for(int i=0;i<1024;i++)
+        kerneltbl[i].active=false;
+    for(phys_t i=((phys_t)&kernel_start)>>12,p = (phys_t)&kernel_start; p < (phys_t)&kernel_end; p+=0x1000, i++) {
+        kerneltbl[i].page=i;
+        kerneltbl[i].writeable=true;
+        kerneltbl[i].privileged=false;
+        kerneltbl[i].no_write_cache=false;
+        kerneltbl[i].no_read_cache=false;
+        kerneltbl[i].pat=false;
+        kerneltbl[i].no_flush_after_cr3=true;
+        kerneltbl[i].active=true;
+    }
+
+    //self-mapping page directory
+    phys_t pdir_selfmap_addr;
+    *pmm >> pdir_selfmap_addr;
+    context[1].pagetable = pdir_selfmap_addr >> 12;
+    context[1].writeable=true;
+    context[1].privileged=false;
+    context[1].no_write_cache=true;
+    context[1].no_read_cache=false;
+    context[1].size=false;
+    context[1].active=true;
+    pagetbl *pdir_selfmap=(pagetbl *)pdir_selfmap_addr;
+    for(int i=0;i<1024;i++) {
+        pdir_selfmap[i].active=false;
+        pdir_selfmap[i].lazy=false;
+    }
+
+    pdir_selfmap[0].page=pagedir_addr >> 12;
+    pdir_selfmap[0].writeable=true;
+    pdir_selfmap[0].privileged=false;
+    pdir_selfmap[0].no_write_cache=true;
+    pdir_selfmap[0].no_read_cache=false;
+    pdir_selfmap[0].pat=false;
+    pdir_selfmap[0].no_flush_after_cr3=false;
+    pdir_selfmap[0].active=true;
+
+    phys_t ptbl_selfmap_addr;
+    *pmm >> ptbl_selfmap_addr;
+    context[2].pagetable = ptbl_selfmap_addr>>12;
+    context[2].writeable=true;
+    context[2].privileged=false;
+    context[2].no_write_cache=true;
+    context[2].no_read_cache=false;
+    context[2].size=false;
+    context[2].active=true;
+    pagetbl *ptbl_selfmap=(pagetbl *)ptbl_selfmap_addr;
+    for(int i=0;i<1024;i++) {
+        ptbl_selfmap[i].active=false;
+        ptbl_selfmap[i].lazy=false;
+    }
+
+
+    //Create a self-map
+    for(int i=0;i<1024;i++) {
+        if(!context[i].active)
+            continue;
+        ptbl_selfmap[i].page = context[i].pagetable;
+        ptbl_selfmap[i].writeable=true;
+        ptbl_selfmap[i].privileged=false;
+        ptbl_selfmap[i].no_write_cache=true;
+        ptbl_selfmap[i].no_read_cache=false;
+        ptbl_selfmap[i].pat=false;
+        ptbl_selfmap[i].no_flush_after_cr3=false;
+        ptbl_selfmap[i].active=true;
+    }
+}
+
+paging_context_x86::~paging_context_x86() {
+    //Deallocate user space
+    pagedir *pd = (pagedir*)0x401000;
+    for(int i=256;i<1024;i++) {
+        if(!pd[i].active)
+            continue;
+        pagetbl *pt = (pagetbl*)(0xC00000+i<<12);
+        for(int j=0;j<1024;j++) {
+            if(!pt[j].active)
+                continue;
+            void * addr = (void *)((i<<22)+(j<<12));
+            munmap(addr);
+        }
+        munmap(pt);
+        *pmm << (pd[i].pagetable << 12);
+    }
+    //Deallocate selfmap
+    for(int i=1;i<3;i++) {
+        if(!pd[i].active)
+            continue;
+        pagetbl *pt = (pagetbl*)(0xC00000+i<<12);
+        for(int j=0;j<1024;j++) {
+            if(!pt[j].active)
+                continue;
+            void * addr = (void *)((i<<22)+(j<<12));
+            munmap(addr);
+        }
+        munmap(pt);
+        *pmm << (pd[i].pagetable << 12);
+    }
+    munmap(pd);
+    *pmm << pagedir_addr;
+}
+
+void paging_context_x86::switch_context() {
+    asm volatile("mov %0, %%cr3" :: "r"(pagedir_addr) : "memory");
+    if(!context_enabled) {
+        uint32_t cr0;
+        asm volatile("mov %%cr0, %0" : "=r"(cr0));
+        cr0 |= (1<<31);
+        asm volatile("mov %0, %%cr0" :: "r"(cr0) : "memory");
+    }
+    paging_context::switch_context();
+}
+
+void paging_context_x86::map_pagetable(struct paging_context *pc_t) {
+    paging_context_x86 *pc = (paging_context_x86*)pc_t;
+    mmap(pc->pagedir_addr, (void*)0x401000, protection::RW, false);
+    pagedir * pd = (pagedir*)0x401000;
+    for(int i=0;i<1024;i++) {
+        if(!pd[i].active)
+            continue;
+        mmap(pd[i].pagetable<<12, (void*)(0xC00000), protection::RW, false);
+    }
+}
+
+void *paging_context_x86::mmap(phys_t addr, void *dest, protection prot, bool lazy) {
+    if((!addr)&&(!lazy)) {
+        *pmm >> addr;
+    }
+    if(!dest) {
+        if(!lazy) {
+            for(phys_t i=16; i < 256; i++) {
+                if((**this)[i].active) {
+                    for(phys_t j=0; j<1024; j++) {
+                        if((*this)[i][j].active)
+                            continue;
+                        dest = (void*)((i<<22)|(j<<12));
+                    }
+                    continue;
+                }
+                dest = (void*)(i<<22);
+            }
+        } else {
+            for(phys_t i=256; i; i++) {
+                if((**this)[i].active) {
+                    for(phys_t j=0; j<1024; j++) {
+                        if((*this)[i][j].active)
+                            continue;
+                        if((*this)[i][j].lazy)
+                            continue;
+                        dest = (void*)((i<<22)|(j<<12));
+                    }
+                    continue;
+                }
+                dest = (void*)(i<<22);
+            }
+        }
+    }
+    if(!dest) {
+        panic("Not enough virtual memory is available for mmap()");
+    }
+    phys_t i=((phys_t)dest)>>22;
+    phys_t j=((phys_t)dest)>>12;
+    j&=0x3FF;
+    if(!(**this)[i].active) {
+        phys_t ptbl_addr;
+        *pmm >> ptbl_addr;
+        mmap(ptbl_addr, (*this)[i], protection::RW, false);
+        pagetbl *pent = (*this)[i];
+        for(int i=0;i<1024;i++)
+            pent[i].active=false;
+        pagedir *ptbl = &((**this)[i]);
+        ptbl->pagetable = ptbl_addr >> 12;
+        ptbl->writeable = true;
+        ptbl->privileged = (i < 256) ? false: true;
+        ptbl->no_write_cache = (i < 16) ? true : false;
+        ptbl->no_read_cache = false;
+        ptbl->size = false;
+        ptbl->active=true;
+    }
+    pagetbl *pent = (*this)[i] + j;
+    uint8_t p = (uint8_t)prot;
+    pent->page = addr >> 12;
+    pent->writeable = (p & 2)? true : false;
+    pent->privileged = (p & 4)? true : false;
+    pent->no_write_cache = (i < 16) ? true : false;
+    pent->no_read_cache = false;
+    pent->pat = false;
+    pent->no_flush_after_cr3 = false;
+    pent->lazy = lazy;
+    pent->active = !lazy;
+    if(current_context == this) {
+        asm volatile("invlpg %0" :: "m"(*(char*)dest) : "memory");
+    }
+    return dest;
+}
+
+void paging_context_x86::munmap(void *addr) {
+    phys_t i=((phys_t)addr)>>22;
+    phys_t j=((phys_t)addr)>>12;
+    j &= 0x3FF;
+    if(!(**this)[i].active)
+        return;
+    if(!(*this)[i][j].active)
+        (*this)[i][j].lazy = false;
+    *pmm << ((*this)[i][j].page << 12);
+    (*this)[i][j].active=false;
+}
+
+bool paging_context_x86::is_mapped(void *addr) {
+    phys_t i=((phys_t)addr)>>22;
+    phys_t j=((phys_t)addr)>>12;
+    j &= 0x3FF;
+    if(!(**this)[i].active)
+        return false;
+    return (*this)[i][j].active;
+}
+
+void paging_context_x86::mprotect(void *addr, protection prot) {
+    phys_t i=((phys_t)addr)>>22;
+    phys_t j=((phys_t)addr)>>12;
+    j &= 0x3FF;
+    if(!(**this)[i].active)
+        return;
+    if((!(*this)[i][j].active) && (!(*this)[i][j].lazy))
+        return;
+    pagetbl *pent=  &((*this)[i][j]);
+    uint8_t p = (uint8_t)prot;
+    pent->writeable = (p & 2) ? true : false;
+    pent->privileged = (p & 4) ? true : false;
+    if(current_context == this)
+        asm volatile("invlpg %0" :: "m"(*(char*)addr) : "memory");
+}
+
+bool paging_context_x86::has_no_exec() {
+    return false;
+}
+
+void *paging_context_x86::get_exception_address(cpu_state *cpu) {
+    uint32_t cr2;
+    asm volatile("mov %%cr2, %0" : "=r"(cr2));
+    return (void*)cr2;
+}
+
+bool paging_context_x86::lazymap(void *addr, cpu_state *cpu) {
+    phys_t i=((phys_t)addr)>>22;
+    phys_t j=((phys_t)addr)>>12;
+    j &= 0x3FF;
+    if(!(**this)[i].active)
+        return false;
+    if((*this)[i][j].active)
+        return false;
+    if(!(*this)[i][j].lazy)
+        return false;
+    phys_t page;
+    *pmm >> page;
+    pagetbl *pent = &((*this)[i][j]);
+    pent->page = page >> 12;
+    pent->lazy = false;
+    pent->active = true;
+    return true;
+}
+
+pagedir * paging_context_x86::operator*() {
+    if(current_context == this)
+        return (pagedir*)0x400000;
+    return (pagedir*)0x401000;
+}
+
+pagetbl * paging_context_x86::operator[](phys_t i) {
+    if(current_context == this)
+        return (pagetbl *)(0x800000+(i<<12));
+    return (pagetbl *)(0xC00000+(i<<12));
+}
diff --git a/kernel/arch/x86/pc/flags.cmake b/kernel/arch/x86/pc/flags.cmake
index 1ef2bef..f8f7c29 100644
--- a/kernel/arch/x86/pc/flags.cmake
+++ b/kernel/arch/x86/pc/flags.cmake
@@ -1,3 +1,3 @@
-SET(PLATFORM_C_FLAGS "-I../../kernel/arch/x86/pc/include -O2")
+SET(PLATFORM_C_FLAGS "-I../../kernel/arch/x86/pc/include -O0")
 SET(PLATFORM_CXX_FLAGS "${PLATFORM_C_FLAGS}")
 SET(PLATFORM_ASM_FLAGS "${PLATFORM_C_FLAGS}")
diff --git a/kernel/arch/x86/pc/start.cpp b/kernel/arch/x86/pc/start.cpp
index ff3a5a4..bc49c54 100644
--- a/kernel/arch/x86/pc/start.cpp
+++ b/kernel/arch/x86/pc/start.cpp
@@ -8,6 +8,7 @@
 #include "../../../hw/pc/8259/pic.hpp"
 #include "../../../hw/pc/idt/idt.hpp"
 #include "../../../hw/pc/pmm/pmm.hpp"
+#include <paging.h>
 
 #include <base.hpp>
 static multiboot_info_t *mb_info;
@@ -17,6 +18,8 @@ CGATerm term;
 VESAfb term(mb_info);
 #endif
 PMM_MB lpmm(mb_info);
+
+paging_context_x86 main_context;
 void main();
 extern "C" void start(int eax, multiboot_info_t *ebx) {
     mb_info = ebx;
@@ -27,6 +30,13 @@ void drivers_init() {
     setMainTTY(&term);
     --term;
     initIDT();
+    main_context.switch_context();
+    main_context.mmap((phys_t)mb_info, mb_info, protection::RW, false);
+    phys_t start_fb = (phys_t)(mb_info->framebuffer_addr);
+    phys_t end_fb = start_fb + mb_info->framebuffer_height * mb_info->framebuffer_pitch;
+    for(phys_t i=start_fb; i<end_fb; i+=0x1000) {
+        main_context.mmap(i, (void*)i, protection::RW, false);
+    }
     PIC::initPIC(0x20, 0x28);
     asm volatile("sti");
 }
diff --git a/kernel/arch/x86/sourcegen.py b/kernel/arch/x86/sourcegen.py
index 4d917c8..698672d 100644
--- a/kernel/arch/x86/sourcegen.py
+++ b/kernel/arch/x86/sourcegen.py
@@ -45,6 +45,7 @@ int_handler.write("    push %esp\n    jmp panic2\n")
 int_handler.write(".section .data\n"+data_section)
 
 print("Generating cpu_state struct")
+reg_struct.write("#pragma once\n")
 reg_struct.write("#include <stdint.h>\n")
 if config["ENABLE_FPU"] and not config["ENABLE_SSE"]:
     reg_struct.write("struct fpu_state {\n")
diff --git a/kernel/hw/pc/config.py b/kernel/hw/pc/config.py
index bd9a8dc..c4659c9 100644
--- a/kernel/hw/pc/config.py
+++ b/kernel/hw/pc/config.py
@@ -9,3 +9,4 @@ else:
 add_driver(False, "8259")
 add_driver(False, "idt")
 add_driver(False, "pmm")
+
diff --git a/kernel/hw/pc/pmm/pmm.cpp b/kernel/hw/pc/pmm/pmm.cpp
index 35a3d7f..192c3a2 100644
--- a/kernel/hw/pc/pmm/pmm.cpp
+++ b/kernel/hw/pc/pmm/pmm.cpp
@@ -28,7 +28,7 @@ auto PMM_MB::isFree(phys_t addr) -> bool {
     }
     if(!free)
         return false;
-    if(addr == (phys_t)((uintptr_t)mb_info))
+    if((addr >= (phys_t)((uintptr_t)mb_info)) && (addr < (phys_t)((uintptr_t)mb_info)+0x1000))
         return false;
     return PMM::isFree(addr);
 }
diff --git a/kernel/src/include/paging.hpp b/kernel/src/include/paging.hpp
new file mode 100644
index 0000000..4f90053
--- /dev/null
+++ b/kernel/src/include/paging.hpp
@@ -0,0 +1,32 @@
+#pragma once
+#include <stdint.h>
+#include <pmm.hpp>
+#include <regs.h>
+
+enum class protection: uint8_t {
+    NONE=0,
+    X=1,
+    W=2,
+    WX=3,
+    R=4,
+    RX=5,
+    RW=6,
+    RWX=7
+};
+
+struct paging_context {
+    paging_context();
+    virtual ~paging_context();
+    virtual void switch_context();
+    virtual void map_pagetable(struct paging_context *);
+    virtual void* mmap(phys_t addr, void* dest, protection prot=protection::RW, bool lazy=true);
+    virtual void munmap(void* addr);
+    virtual bool is_mapped(void* addr);
+    virtual void mprotect(void* addr, protection prot);
+    virtual bool has_no_exec();
+    virtual void *get_exception_address(cpu_state *cpu);
+    virtual bool lazymap(void* addr, cpu_state *cpu);
+};
+
+extern paging_context *current_context;
+extern bool context_enabled;
diff --git a/kernel/src/include/pmm.hpp b/kernel/src/include/pmm.hpp
index 0d5510a..5327b4b 100644
--- a/kernel/src/include/pmm.hpp
+++ b/kernel/src/include/pmm.hpp
@@ -20,10 +20,11 @@ class PMM {
         PMM(phys_t page_size);
         virtual ~PMM();
         virtual auto operator<<(phys_t page) -> PMM &; ///< Frees a page. O(1)
-        virtual auto operator>>(phys_t &page) -> PMM &; ///< Allocates a page. O(1)
-        virtual auto operator,(size_t no_pages) -> phys_t; ///< Allocates multiple pages. O(n²)
+        virtual auto operator>>(phys_t &page) -> PMM &; ///< Allocates a page. Probably O(log n)
+        virtual auto operator,(size_t no_pages) -> phys_t; ///< Allocates multiple pages. O(n)
         virtual auto operator()(phys_t pages,size_t no_pages) -> void; ///< Deallocates multiple pages. O(n)
-        virtual auto operator&&(phys_t page) -> bool; //Returns true if this page is free. O(n).
+        virtual auto operator&&(phys_t page) -> bool; //Returns true if this page is free. O(1).
+        virtual auto setUsed(phys_t page) -> void; //Marks a page as used. O(1).
 };
 /**
  * This definition is for having a python-like syntax - like `page in pmm`
diff --git a/kernel/src/paging.cpp b/kernel/src/paging.cpp
new file mode 100644
index 0000000..5efb294
--- /dev/null
+++ b/kernel/src/paging.cpp
@@ -0,0 +1,36 @@
+#include <paging.hpp>
+paging_context *current_context(nullptr);
+bool context_enabled=false;
+paging_context::paging_context() {}
+paging_context::~paging_context() {}
+
+void paging_context::switch_context() {
+    current_context = this;
+    context_enabled = true;
+}
+
+void paging_context::map_pagetable(struct paging_context *) {}
+
+void* paging_context::mmap(phys_t addr, void* dest, protection prot, bool lazy) {
+    return nullptr;
+}
+
+void paging_context::munmap(void *addr) {}
+
+bool paging_context::is_mapped(void *addr) {
+    return false;
+}
+
+void paging_context::mprotect(void *addr, protection prot) {}
+
+bool paging_context::has_no_exec() {
+    return false;
+}
+
+void *paging_context::get_exception_address(cpu_state *cpu) {
+    return nullptr;
+}
+
+bool paging_context::lazymap(void *addr, cpu_state *cpu) {
+    return false;
+}
diff --git a/kernel/src/pmm.cpp b/kernel/src/pmm.cpp
index 22b8157..f0e85df 100644
--- a/kernel/src/pmm.cpp
+++ b/kernel/src/pmm.cpp
@@ -16,7 +16,12 @@ auto PMM::isFree(phys_t addr) -> bool {
         return false;
     return true;
 }
-PMM::PMM(phys_t page_size): page_size(page_size), first_free(0), lowest_page(~0), highest_page(0) {}
+PMM::PMM(phys_t page_size): page_size(page_size), first_free(0), lowest_page(~0), highest_page(0) {
+    for(int i=0;i<32768;i++) {
+        pmm_bitmap[i]=0;
+    }
+    pmm = this;
+}
 void PMM::fill() {
     for(phys_t i=highest_page; i>=lowest_page && i; i-=page_size) {
         if(isFree(i))
@@ -97,6 +102,8 @@ auto PMM::operator()(phys_t pages, size_t no_pages) -> void {
     if(pages < first_free)
         first_free = pages;
     for(size_t i=0; i<no_pages; i++, pages+=page_size) {
+        if(!isFree(pages))
+            continue;
         phys_t index = pageno >> 5;
         phys_t bit = pageno & 31;
         pmm_bitmap[index] |= 1<<bit;
@@ -113,6 +120,12 @@ auto PMM::operator&&(phys_t page) -> bool {
         return false;
     return true;
 }
+auto PMM::setUsed(phys_t page) -> void {
+    phys_t pageno = page / page_size;
+    phys_t index = pageno >> 5;
+    phys_t bit = pageno & 31;
+    pmm_bitmap[index] &= ~(1<<bit);
+}
 auto operator&&(phys_t a, PMM mm) -> bool {
     return mm && a;
 }