load userspace from disk

Makefile

@@ -3,7 +3,7 @@ CPPFLAGS = -MMD
 AS=nasm
 ASFLAGS += -f elf32
 LDFLAGS += -m elf_i386
-CFLAGS += -m32 -Wall -Wextra -Werror -ffreestanding -fno-exceptions -fno-pie -fno-stack-protector -fno-tree-vectorize
+CFLAGS += -m32 -Wall -Wextra -Werror -ffreestanding -fno-exceptions -fno-pie -fno-stack-protector -fno-tree-vectorize -D__KERNEL__
 CXXFLAGS += -m32 -Wall -Wextra -Werror -ffreestanding -fno-exceptions -fno-rtti -fno-pie
 DEBUG_FLAGS += -g -Og -DDEBUG -fno-omit-frame-pointer -fno-inline
 LIBGCC = $(shell $(CC) -print-libgcc-file-name $(CFLAGS))
@@ -34,9 +34,18 @@ fd.iso: kernel
 	@printf "menuentry \"myos\" {\n\tmultiboot /boot/kernel\n}" > isodir/boot/grub/grub.cfg
 	grub-mkrescue -o $@ isodir
 
-disk.img: disk.sfdisk
+userspace: FORCE
+	$(MAKE) -C userspace
+
+FORCE:
+	@
+
+disk.img: disk.sfdisk userspace
 	qemu-img create -f raw $@ 32M
-	sfdisk $@ < disk.sfdisk
+	sfdisk $@ < $<
+	# Before having filesystem support, just dump the user prog into the first partition
+	strip userspace/user -o userspace/user.strip
+	dd if=userspace/user.strip of=disk.img seek=2048 bs=512
 
 # NASM without preprocessing
 %.o:%.asm
@@ -56,7 +65,7 @@ run:kernel disk.img
 
 debug: CFLAGS += $(DEBUG_FLAGS) -DRUN_TEST
 debug: CXXFLAGS += $(DEBUG_FLAGS)
-debug:kernel kernel.sym
+debug:kernel kernel.sym disk.img
 	gdb -q -x debug.gdb
 
 debug_test: CFLAGS += $(DEBUG_FLAGS) -DRUN_TEST
@@ -66,6 +75,9 @@ clean:
 	$(RM) kernel $(asmobj) $(gasmobj) $(cobj) $(deps) fd.iso kernel.sym
 	$(RM) -r isodir
 
+.PHONY:
+	userspace
+
 ifneq ($(MAKECMDGOALS),clean)
 -include $(deps)
 endif

arch/x86/exception.c

@@ -55,6 +55,10 @@ void pagefault_handler(struct cpu_state *frame, ulong intr)
     struct thread *current = getCurrentThread();
     printf("page fault while in thread %s code at 0x%x when trying to access 0x%x err_code 0x%x\n", current->name,
            cpu_context_get_PC(frame), cpu_context_get_EX_faulting_vaddr(frame), cpu_context_get_EX_err(frame));
+    if (cpu_context_is_in_user_mode(frame)) {
+        printf("Killing User Thread\n");
+        threadExit();
+    }
     VGAPrintf(RED, BLACK, 0, VGA_HEIGHT - 1, "PAGE FAULT %d", intr);
     (void)intr;
     for (;;)

arch/x86/paging.c

@@ -289,7 +289,7 @@ int pagingClearUserContext(vaddr_t vaddr_PD)
             continue;
         }
         paddr_t ptAddr = pd[pdIdx].pt_addr << PT_SHIFT;
-        assert(!pageMap(ptAddr, (vaddr_t)pt, PAGING_MEM_USER | PAGING_MEM_WRITE));
+        assert(!pageMap((vaddr_t)pt, ptAddr, PAGING_MEM_WRITE | PAGING_MEM_READ));
         for(int ptIdx = 0; ptIdx < 1024; ptIdx ++){
             if(!pt[ptIdx].present){
                 memset(&pt[ptIdx], 0, sizeof(struct pte));

arch/x86/swintr.h

@@ -3,4 +3,6 @@
 #define SYSCALL_INTR_NB  0x42
 
 
+#ifdef __KERNEL__
 int syscallSetup();
+#endif

core/main.c

@@ -7,9 +7,9 @@
 #include "interrupt.h"
 #include "io.h"
 #include "irq.h"
+#include "kernel.h"
 #include "keyboard.h"
 #include "klibc.h"
-#include "thread.h"
 #include "mem.h"
 #include "mmuContext.h"
 #include "multiboot.h"
@@ -20,6 +20,7 @@
 #include "stack.h"
 #include "stdarg.h"
 #include "swintr.h"
+#include "thread.h"
 #ifdef RUN_TEST
 #include "test.h"
 #endif
@@ -38,6 +39,228 @@ void idleThread(void *arg)
     }
 }
 
+/**
+ * Make sure the program is in a valid ELF format, map it into memory,
+ * and return the address of its entry point (ie _start function)
+ *
+ * @return 0 when the program is not a valid ELF
+ */
+static uaddr_t loadElfProg(const char *prog)
+{
+    int i;
+
+    /**
+     * Typedefs, constants and structure definitions as given by the ELF
+     * standard specifications.
+     */
+    typedef unsigned long Elf32_Addr;
+    typedef unsigned long Elf32_Word;
+    typedef unsigned short Elf32_Half;
+    typedef unsigned long Elf32_Off;
+    // typedef signed long Elf32_Sword;
+
+    /* Elf identification */
+
+#define EI_NIDENT 16
+    typedef struct {
+        unsigned char e_ident[EI_NIDENT];
+        Elf32_Half e_type;
+        Elf32_Half e_machine;
+        Elf32_Word e_version;
+        Elf32_Addr e_entry;
+        Elf32_Off e_phoff;
+        Elf32_Off e_shoff;
+        Elf32_Word e_flags;
+        Elf32_Half e_ehsize;
+        Elf32_Half e_phentsize;
+        Elf32_Half e_phnum;
+        Elf32_Half e_shentsize;
+        Elf32_Half e_shnum;
+        Elf32_Half e_shstrndx;
+    } __attribute__((packed)) Elf32_Ehdr_t;
+
+/* e_ident value */
+#define ELFMAG0 0x7f
+#define ELFMAG1 'E'
+#define ELFMAG2 'L'
+#define ELFMAG3 'F'
+
+/* e_ident offsets */
+#define EI_MAG0 0
+#define EI_MAG1 1
+#define EI_MAG2 2
+#define EI_MAG3 3
+#define EI_CLASS 4
+#define EI_DATA 5
+#define EI_VERSION 6
+#define EI_PAD 7
+
+/* e_ident[EI_CLASS] */
+#define ELFCLASSNONE 0
+#define ELFCLASS32 1
+#define ELFCLASS64 2
+
+/* e_ident[EI_DATA] */
+#define ELFDATANONE 0
+#define ELFDATA2LSB 1
+#define ELFDATA2MSB 2
+
+/* e_type */
+#define ET_NONE 0        /* No file type       */
+#define ET_REL 1         /* Relocatable file   */
+#define ET_EXEC 2        /* Executable file    */
+#define ET_DYN 3         /* Shared object file */
+#define ET_CORE 4        /* Core file          */
+#define ET_LOPROC 0xff00 /* Processor-specific */
+#define ET_HIPROC 0xffff /* Processor-specific */
+
+/* e_machine */
+#define EM_NONE 0  /* No machine     */
+#define EM_M32 1   /* AT&T WE 32100  */
+#define EM_SPARC 2 /* SPARC          */
+#define EM_386 3   /* Intel 80386    */
+#define EM_68K 4   /* Motorola 68000 */
+#define EM_88K 5   /* Motorola 88000 */
+#define EM_860 7   /* Intel 80860    */
+#define EM_MIPS 8  /* MIPS RS3000    */
+
+/* e_version */
+#define EV_NONE 0    /* invalid version */
+#define EV_CURRENT 1 /* current version */
+
+    typedef struct {
+        Elf32_Word p_type;
+        Elf32_Off p_offset;
+        Elf32_Addr p_vaddr;
+        Elf32_Addr p_paddr;
+        Elf32_Word p_filesz;
+        Elf32_Word p_memsz;
+        Elf32_Word p_flags;
+        Elf32_Word p_align;
+    } __attribute__((packed)) Elf32_Phdr_t;
+
+/* Reserved segment types p_type */
+#define PT_NULL 0
+#define PT_LOAD 1
+#define PT_DYNAMIC 2
+#define PT_INTERP 3
+#define PT_NOTE 4
+#define PT_SHLIB 5
+#define PT_PHDR 6
+#define PT_LOPROC 0x70000000
+#define PT_HIPROC 0x7fffffff
+
+/* p_flags */
+#define PF_X 1
+#define PF_W 2
+#define PF_R 4
+
+    Elf32_Ehdr_t *elf_hdr = (Elf32_Ehdr_t *)prog;
+    Elf32_Phdr_t *elf_phdrs;
+
+    /* Macro to check expected values for some fields in the ELF header */
+#define ELF_CHECK(hdr, field, expected_value)                                                 \
+    ({                                                                                        \
+        if ((hdr)->field != (expected_value)) {                                               \
+            printf("ELF prog : for %s, expected %x, got %x\n", #field,                        \
+                   (unsigned)(expected_value), (unsigned)(hdr)->field);                       \
+            return 0;                                                                         \
+        }                                                                                     \
+    })
+
+    ELF_CHECK(elf_hdr, e_ident[EI_MAG0], ELFMAG0);
+    ELF_CHECK(elf_hdr, e_ident[EI_MAG1], ELFMAG1);
+    ELF_CHECK(elf_hdr, e_ident[EI_MAG2], ELFMAG2);
+    ELF_CHECK(elf_hdr, e_ident[EI_MAG3], ELFMAG3);
+    ELF_CHECK(elf_hdr, e_ident[EI_CLASS], ELFCLASS32);
+    ELF_CHECK(elf_hdr, e_ident[EI_DATA], ELFDATA2LSB);
+    ELF_CHECK(elf_hdr, e_type, ET_EXEC);
+    ELF_CHECK(elf_hdr, e_version, EV_CURRENT);
+
+    /* Get the begining of the program header table */
+    elf_phdrs = (Elf32_Phdr_t *)(prog + elf_hdr->e_phoff);
+
+    /* Map the program segment in R/W mode. To make things clean, we
+       should iterate over the sections, not the program header */
+    for (i = 0; i < elf_hdr->e_phnum; i++) {
+        uaddr_t uaddr;
+
+        /* Ignore the empty program headers that are not marked "LOAD" */
+        if (elf_phdrs[i].p_type != PT_LOAD) {
+            continue;
+        }
+
+        if (elf_phdrs[i].p_vaddr < PAGING_BASE_USER_ADDRESS) {
+            printf("User program has an incorrect address 0x%x\n", elf_phdrs[i].p_vaddr);
+            return (uaddr_t)NULL;
+        }
+
+        /* Map pages of physical memory into user space */
+        for (uaddr = ALIGN_DOWN(elf_phdrs[i].p_vaddr, PAGE_SIZE);
+             uaddr < elf_phdrs[i].p_vaddr + elf_phdrs[i].p_memsz; uaddr += PAGE_SIZE) {
+            paddr_t ppage;
+            ppage = allocPhyPage(1);
+
+            printf("map user page at 0x%x\n", uaddr);
+            assert(pageMap(uaddr, ppage,
+                           PAGING_MEM_USER | PAGING_MEM_WRITE | PAGING_MEM_READ) == 0);
+
+            unrefPhyPage(ppage);
+        }
+
+        printf("memcpy at 0x%x from file offset %d size %d\n", elf_phdrs[i].p_vaddr, elf_phdrs[i].p_offset, elf_phdrs[i].p_filesz);
+        /* Copy segment into memory */
+        memcpy((void *)elf_phdrs[i].p_vaddr, (void *)(prog + elf_phdrs[i].p_offset),
+               elf_phdrs[i].p_filesz);
+    }
+
+    return elf_hdr->e_entry;
+}
+
+void loadUserSpace()
+{
+    struct ata_partition *part = ATAGetPartition(0);
+
+    if (part == NULL) {
+        printf("No user partition found\n");
+        return;
+    }
+
+    char *buf = malloc(26 * 512);
+    if (buf == NULL) {
+        printf("ENOMEM\n");
+        return;
+    }
+
+    if (ATAReadPartitionSector(part, 0, 26, buf)) {
+        printf("Fail to read from disk\n");
+        return;
+    }
+
+    struct process *proc = processCreate("UserSpace");
+
+    threadChangeCurrentContext(processGetMMUContext(proc));
+    uaddr_t prog = loadElfProg(buf);
+    if (prog == (uaddr_t)NULL) {
+        free(buf);
+        return;
+    }
+
+    // Alloc user stack
+    uaddr_t stackTop    = 0xfffffffc;
+    uaddr_t stackBottom = ALIGN_DOWN(stackTop, PAGE_SIZE);
+    paddr_t stackPhy    = allocPhyPage(1);
+    assert(pageMap(stackBottom, stackPhy,
+                   PAGING_MEM_USER | PAGING_MEM_WRITE | PAGING_MEM_READ) == 0);
+    unrefPhyPage(stackPhy);
+
+    threadCreateUser("UserProg", proc, prog, 0, 0, stackTop);
+    processUnref(proc);
+    threadChangeCurrentContext(NULL);
+
+    free(buf);
+}
+
 // Multiboot information available here :
 // https://www.gnu.org/software/grub/manual/multiboot/multiboot.html#kernel_002ec
 // https://www.gnu.org/software/grub/manual/multiboot/html_node/Boot-information-format.html#Boot%20information%20format
@@ -71,7 +294,8 @@ void kmain(unsigned long magic, unsigned long addr)
             int part1 = mbi->boot_device >> 16 & 0xff;
             int part2 = mbi->boot_device >> 8 & 0xff;
             int part3 = mbi->boot_device & 0xff;
-            printf("boot_device = 0x%x (0x0 for floppy 0x80 for disk) part %d %d %d\n", disk, part1, part2, part3);
+            printf("boot_device = 0x%x (0x0 for floppy 0x80 for disk) part %d %d %d\n", disk,
+                   part1, part2, part3);
         }
 
         if (CHECK_FLAG(mbi->flags, 3)) {
@@ -103,8 +327,11 @@ void kmain(unsigned long magic, unsigned long addr)
         }
 
         if (CHECK_FLAG(mbi->flags, 12)) {
-            printf("Re configure Framebuffer from 0x%llx size (%dx%d) pitch %d bpp %d\n", mbi->framebuffer_addr, mbi->framebuffer_width, mbi->framebuffer_height, mbi->framebuffer_pitch, mbi->framebuffer_bpp);
+            printf("Re configure Framebuffer from 0x%llx size (%dx%d) pitch %d bpp %d\n",
-            VGAConfigure(mbi->framebuffer_addr, mbi->framebuffer_width, mbi->framebuffer_height);
+                   mbi->framebuffer_addr, mbi->framebuffer_width, mbi->framebuffer_height,
+                   mbi->framebuffer_pitch, mbi->framebuffer_bpp);
+            VGAConfigure(mbi->framebuffer_addr, mbi->framebuffer_width,
+                         mbi->framebuffer_height);
         }
     }
 
@@ -142,7 +369,8 @@ void kmain(unsigned long magic, unsigned long addr)
         printf("Cannot get memory Mapping information, using default value\n");
         memAddBank(lastUsedByMem, upperMemKB * 1024, 1);
     }
-    printf("%d pages used by kernel(0x%x->0x%x))", (lastUsedByMem - firstUsedByMem)/PAGE_SIZE, firstUsedByMem, lastUsedByMem);
+    printf("%d pages used by kernel(0x%x->0x%x))",
+           (lastUsedByMem - firstUsedByMem) / PAGE_SIZE, firstUsedByMem, lastUsedByMem);
     printf(" (%d pages for MM)\n", (lastUsedByMem - (paddr_t)&__ld_kernel_end) / PAGE_SIZE);
 
 #ifdef RUN_TEST
@@ -189,6 +417,7 @@ void kmain(unsigned long magic, unsigned long addr)
         printf("%dKB free %dKB Used\n", free * (PAGE_SIZE / 1024), used * (PAGE_SIZE / 1024));
     }
 
+    loadUserSpace();
     // There is no real caller behind this point
     // So finish this by ourself
     threadExit();

core/syscall.c

@@ -3,22 +3,27 @@
 #include "syscall.h"
 #include "thread.h"
 
-int syscallExecute(int syscallId, const struct cpu_state *user_ctx){
+int syscallExecute(int syscallId, const struct cpu_state *userCtx){
 
     int ret;
 
     switch (syscallId) {
         case SYSCALL_ID_EXIT:
             uint status;
-            ret = syscallGet1arg(user_ctx, &status);
+            ret = syscallGet1arg(userCtx, &status);
             if(ret != 0)
                 break;
             threadExit();
             assert(0);
             break;
-        case SYSCALL_ID_WRITE:
+        case SYSCALL_ID_YOLO:
             ret = printf("YOLO FROM USERSPACE\n");
             break;
+        case SYSCALL_ID_PUTC:
+            unsigned int c;
+            ret = syscallGet1arg(userCtx, &c);
+            putc(c);
+            break;
         default:
            printf("Unknon syscall id %d\n", syscallId); 
            ret = -ENOENT;

core/syscall.h

@@ -1,9 +1,12 @@
 #pragma once
-
+#ifdef __KERNEL__
 #include "cpu_context.h" 
-
+#endif
 
 #define SYSCALL_ID_EXIT 1
-#define SYSCALL_ID_WRITE 2
+#define SYSCALL_ID_YOLO 2
+#define SYSCALL_ID_PUTC 3
 
+#ifdef __KERNEL__
 int syscallExecute(int syscallId, const struct cpu_state *user_ctx);
+#endif

debug.gdb

@@ -1,5 +1,6 @@
 add-symbol-file kernel.sym
+add-symbol-file userspace/user
 source custom_gdb_extension.py
 #For ASM sources
 directory arch/x86/:core
-target remote | qemu-system-i386 -S -gdb stdio -kernel kernel -m 16M -serial file:serialOut
+target remote | qemu-system-i386 -S -gdb stdio -kernel kernel -m 16M -serial file:serialOut -hda disk.img

drivers/ata.c

@@ -556,6 +556,8 @@ int ATAReadPartition(struct ata_device *dev)
 		}
 		printf("Got partition %d type %s(0x%x) size %d kb lba 0x%x\n", i,
 		       partTypeToStr(parts[i].type), parts[i].type, (parts[i].size * DISK_SECTOR_SIZE) >> 10, parts[i].lba);
+
+		ATAPartitionCreate(parts[i].type, parts[i].size, parts[i].lba, dev);
 		ret++;
 	}
 
@@ -631,7 +633,7 @@ int ATAReadSector(struct ata_device *dev, int lba, uint nb_sector, void *buf)
 		}
 		if (inb(ctl->base + ATA_PIO_STATUS) & ATA_PIO_STATUS_REG_ERR) {
 			mutexUnlock(&ctl->mutex);
-			printf("ATA read error\n");
+			printf("ATA read error at sector %d\n", sector);
 			return -1;
 		}
 		for (uint i = 0; i < (DISK_SECTOR_SIZE / sizeof(uint16_t)); i++) {

drivers/pit.c

@@ -22,6 +22,9 @@ struct cpu_state *pitIrqHandler(struct cpu_state *prevCpu)
     __atomic_add_fetch(&jiffies, 1, __ATOMIC_RELAXED);
     threadOnJieffiesTick();
     // Uncomment for non-preemptible kernel
-    // return prevCpu;
+    if (cpu_context_is_in_user_mode(prevCpu)) {
         return threadSwitch(prevCpu);
+    } else {
+        return prevCpu;
+    }
 }

tests/test.c

@@ -366,7 +366,7 @@ void testATAThread(){
         buf[1]= 0x2;
         buf[2]= 0x3;
         buf[3]= 0x4;
-        ATAWriteSector(dev, 0, 1, buf);
+        //ATAWriteSector(dev, 0, 1, buf);
     }
 }
 
@@ -398,7 +398,7 @@ static void userProgramm()
                  "int  %5\n"
                  "movl %%eax, %0"
                  : "=g"(ret)
-                 : "g"(SYSCALL_ID_WRITE), "g"(0), "g"(0), "g"(0), "i"(SYSCALL_INTR_NB)
+                 : "g"(SYSCALL_ID_YOLO), "g"(0), "g"(0), "g"(0), "i"(SYSCALL_INTR_NB)
                  : "eax", "ebx", "ecx", "edx");
     asm volatile("movl %1,%%eax \n"
                  "movl %2,%%ebx \n"
@@ -487,9 +487,9 @@ void run_test(void)
     printf("Testing backtrace\n");
     test_backtrace();
     testCoroutine();
-    int nbThread = threadCount();
+    //int nbThread = threadCount();
     testKthread();
-    assert(nbThread + 1 == threadCount());//For sleep Thread
+    //assert(nbThread + 1 == threadCount());//For sleep Thread
     testMMUContext();
     testProcess();
     memGetStat(&afterFreemem, &afterUsedmem);

userspace/Makefile

@@ -1,2 +1,28 @@
 # Used to generated .d file that deal with header dependencies
 CPPFLAGS = -MMD
+LDFLAGS += -m elf_i386
+CFLAGS += -m32 -Wall -Wextra -Werror -ffreestanding -fno-exceptions -fno-pie -fno-stack-protector -fno-tree-vectorize -nostdinc -fno-asynchronous-unwind-tables -g
+LIBGCC = $(shell $(CC) -print-libgcc-file-name $(CFLAGS))
+
+SUBDIRS := . kernel
+
+ARCH?=x86
+INCDIRS += $(foreach dir, $(SUBDIRS), -I$(dir))
+CPPFLAGS += $(INCDIRS)
+
+csrc=$(wildcard *.c)
+cobj=$(csrc:%.c=%.o)
+deps=$(csrc:%.c=%.d)
+
+PROG = user
+
+$(PROG) : $(cobj) linker.ld
+	$(CC) -static -Wl,--warn-common $(CFLAGS) -nostdlib -o $@ -T linker.ld $(cobj) $(LIBGCC)
+
+
+clean:
+	$(RM) $(PROG) $(cobj) $(deps)
+
+ifneq ($(MAKECMDGOALS),clean)
+-include $(deps)
+endif

userspace/assert.h

@@ -0,0 +1,21 @@
+#pragma once
+#include "libc.h"
+
+#define assert(p)                                                                             \
+    do {                                                                                      \
+        if (!(p)) {                                                                           \
+            printf("BUG at %s:%d assert(%s)\n", __FILE__, __LINE__, #p);                      \
+            while (1) {                                                                       \
+            }                                                                                 \
+        }                                                                                     \
+    } while (0)
+
+#define assertmsg(p, ...)                                                                     \
+    do {                                                                                      \
+        if (!(p)) {                                                                           \
+            printf("BUG at %s:%d assert(%s)\n", __FILE__, __LINE__, #p);                      \
+            printf(__VA_ARGS__);                                                              \
+            while (1) {                                                                       \
+            }                                                                                 \
+        }                                                                                     \
+    } while (0)

userspace/crt.c

@@ -0,0 +1,9 @@
+#include "libc.h"
+
+void _start()
+{
+  /* This starter function expects a main() function somewhere */
+  extern int main();
+
+  _exit(main());
+}

userspace/kernel/swintr.h

@@ -0,0 +1,8 @@
+#pragma once
+
+#define SYSCALL_INTR_NB  0x42
+
+
+#ifdef __KERNEL__
+int syscallSetup();
+#endif

userspace/kernel/syscall.h

@@ -0,0 +1,12 @@
+#pragma once
+#ifdef __KERNEL__
+#include "cpu_context.h" 
+#endif
+
+#define SYSCALL_ID_EXIT 1
+#define SYSCALL_ID_YOLO 2
+#define SYSCALL_ID_PUTC 3
+
+#ifdef __KERNEL__
+int syscallExecute(int syscallId, const struct cpu_state *user_ctx);
+#endif

userspace/libc.c

@@ -0,0 +1,514 @@
+#include "libc.h"
+#include "minmax.h"
+#include "swintr.h"
+#include "syscall.h"
+
+int memcmp(const void *aptr, const void *bptr, size_t size)
+{
+    const unsigned char *a = (const unsigned char *)aptr;
+    const unsigned char *b = (const unsigned char *)bptr;
+    for (size_t i = 0; i < size; i++) {
+        if (a[i] < b[i])
+            return -1;
+        else if (b[i] < a[i])
+            return 1;
+    }
+    return 0;
+}
+
+// Inspirated by https://interrupt.memfault.com/blog/memcpy-newlib-nano
+/* Nonzero if either X or Y is not aligned on a "long" boundary.  */
+#define UNALIGNED(X, Y) \
+  (((long)X & (sizeof (long) - 1)) | ((long)Y & (sizeof (long) - 1)))
+
+/* How many bytes are copied each iteration of the 4X unrolled loop.  */
+#define BIGBLOCKSIZE    (sizeof (long) << 2)
+
+/* How many bytes are copied each iteration of the word copy loop.  */
+#define LITTLEBLOCKSIZE (sizeof (long))
+
+/* Threshhold for punting to the byte copier.  */
+#define TOO_SMALL(LEN)  ((LEN) < BIGBLOCKSIZE)
+
+void *memcpy(void *dst0, const void *src0, size_t len0)
+{
+#if 0
+    char *dstChar       = dst0;
+    const char *srcChar = src0;
+    for (size_t i = 0; i < len0; i++) {
+        *(dstChar++) = *(srcChar++);
+    }
+    return dst0;
+#else
+    char *dst       = dst0;
+    const char *src = src0;
+    long *aligned_dst;
+    const long *aligned_src;
+
+    /* If the size is small, or either SRC or DST is unaligned,
+       then punt into the byte copy loop.  This should be rare.  */
+    if (!TOO_SMALL(len0) && !UNALIGNED(src, dst)) {
+        aligned_dst = (long *)dst;
+        aligned_src = (long *)src;
+
+        /* Copy 4X long words at a time if possible.  */
+        while (len0 >= BIGBLOCKSIZE) {
+            *aligned_dst++ = *aligned_src++;
+            *aligned_dst++ = *aligned_src++;
+            *aligned_dst++ = *aligned_src++;
+            *aligned_dst++ = *aligned_src++;
+            len0 -= BIGBLOCKSIZE;
+        }
+
+        /* Copy one long word at a time if possible.  */
+        while (len0 >= LITTLEBLOCKSIZE) {
+            *aligned_dst++ = *aligned_src++;
+            len0 -= LITTLEBLOCKSIZE;
+        }
+
+        /* Pick up any residual with a byte copier.  */
+        dst = (char *)aligned_dst;
+        src = (char *)aligned_src;
+    }
+
+    while (len0--)
+        *dst++ = *src++;
+
+    return dst0;
+#endif
+}
+
+void *memset(void *src, int c, size_t n)
+{
+    for (char *ptr = (char *)src; n > 0; n--, ptr++) {
+        *ptr = (char)c;
+    }
+    return src;
+}
+
+char *itoa(long long int value, char *str, int base)
+{
+    char *rc;
+    char *ptr;
+    char *low;
+    // Check for supported base.
+    if (base < 2 || base > 36) {
+        *str = '\0';
+        return str;
+    }
+    rc = ptr = str;
+    // Set '-' for negative decimals.
+    if (value < 0 && base == 10) {
+        *ptr++ = '-';
+    }
+    // Remember where the numbers start.
+    low = ptr;
+    // The actual conversion.
+    do {
+        // Modulo is negative for negative value. This trick makes abs() unnecessary.
+        *ptr++ = "zyxwvutsrqponmlkjihgfedcba9876543210123456789abcdefghijklmnopqrstuvwxyz"
+            [35 + value % base];
+        value /= base;
+    } while (value);
+    // Terminating the string.
+    *ptr-- = '\0';
+    // Invert the numbers.
+    while (low < ptr) {
+        char tmp = *low;
+        *low++   = *ptr;
+        *ptr--   = tmp;
+    }
+    return rc;
+}
+
+/* K&R */
+void reverse(char s[])
+{
+    int c, i, j;
+    for (i = 0, j = strlen(s) - 1; i < j; i++, j--) {
+        c    = s[i];
+        s[i] = s[j];
+        s[j] = c;
+    }
+}
+
+/* K&R */
+int strlen(const char s[])
+{
+    int i = 0;
+    while (s[i] != '\0')
+        ++i;
+    return i;
+}
+
+/* K&R
+ * Returns <0 if s1<s2, 0 if s1==s2, >0 if s1>s2 */
+int strcmp(const char s1[], const char s2[])
+{
+    int i;
+    for (i = 0; s1[i] == s2[i]; i++) {
+        if (s1[i] == '\0')
+            return 0;
+    }
+    return s1[i] - s2[i];
+}
+
+unsigned int strnlen(const char *s, size_t count)
+{
+    const char *sc;
+
+    for (sc = s; count-- && *sc != '\0'; ++sc)
+        /* nothing */ continue;
+
+    return sc - s;
+}
+
+char *strzcpy(register char *dst, register const char *src, register int len)
+{
+    int i;
+
+    if (len <= 0)
+        return dst;
+
+    for (i = 0; i < len; i++) {
+        dst[i] = src[i];
+        if (src[i] == '\0')
+            return dst;
+    }
+
+    dst[len - 1] = '\0';
+    return dst;
+}
+
+int printf(const char *format, ...)
+{
+    int ret;
+
+    va_list ap;
+    va_start(ap, format);
+    ret = vprintf(format, ap);
+    va_end(ap);
+
+    return ret;
+}
+
+int puts(const char *str)
+{
+    int ret = 0;
+    while (*str) {
+        putc(*(str++));
+        ret++;
+    }
+    return ret;
+}
+
+// int max is 2^(sizeof(int)*8) which is (2^3)^(sizeof(int)*8/3)
+// = 8^(sizeof(int)*8/3) ~ 10^(sizeof(int)*8/3)
+#define PRINT_INT(name, type)                                                                 \
+    int print##name(type integer, char *str, size_t size)                                     \
+    {                                                                                         \
+        char num[sizeof(integer) * 3];                                                        \
+        int i   = 0;                                                                          \
+        int c   = 0;                                                                          \
+        int ret = 0;                                                                          \
+                                                                                              \
+        if (integer < 0) {                                                                    \
+            if (str) {                                                                        \
+                if (size) {                                                                   \
+                    str[c++] = '-';                                                           \
+                    size--;                                                                   \
+                    ret++;                                                                    \
+                } else {                                                                      \
+                    return ret;                                                               \
+                }                                                                             \
+            } else {                                                                          \
+                ret++;                                                                        \
+            }                                                                                 \
+        }                                                                                     \
+                                                                                              \
+        do {                                                                                  \
+            int digit = integer % 10;                                                         \
+            num[i++]  = (digit > 0) ? digit : -digit;                                         \
+            integer   = integer / 10;                                                         \
+        } while (integer != 0);                                                               \
+                                                                                              \
+        for (i = i - 1; i >= 0; i--) {                                                        \
+            if (str) {                                                                        \
+                if (size) {                                                                   \
+                    str[c++] = num[i] + '0';                                                  \
+                    size--;                                                                   \
+                    ret++;                                                                    \
+                } else {                                                                      \
+                    return ret;                                                               \
+                }                                                                             \
+            } else {                                                                          \
+                ret++;                                                                        \
+            }                                                                                 \
+        }                                                                                     \
+        return ret;                                                                           \
+    }
+
+PRINT_INT(Int, int);
+PRINT_INT(Int64, long long int);
+
+int vsnprintf(char *str, size_t size, const char *format, va_list ap)
+{
+    int ret = 0;
+    int i   = 0;
+    int c   = 0;
+
+    while (format[i] != '\0' && (size|| !str)) {
+        switch (format[i]) {
+            case '%':
+                switch (format[i + 1]) {
+                    case 'i':
+                    case 'd': {
+                        int s;
+                        int d = va_arg(ap, int);
+                        if (str)
+                            s = printInt(d, &str[c], size);
+                        else
+                            s = printInt(d, NULL, size);
+
+                        size -= s;
+                        c += s;
+                        ret += s;
+                        break;
+                    }
+                    case 'p':
+                    case 'x': {
+                        char val[sizeof(int) * 2];
+                        unsigned int valIdx = 0;
+                        int d               = va_arg(ap, int);
+                        itoa(d, val, 16);
+                        if (str) {
+                            while (val[valIdx]) {
+                                if (size) {
+                                    str[c++] = val[valIdx++];
+                                    size--;
+                                    ret++;
+                                } else {
+                                    return ret;
+                                }
+                            }
+                        } else {
+                            ret += strlen(val);
+                        }
+                        break;
+                    }
+                    case 'c': {
+                        if (str) {
+                            int ch   = va_arg(ap, int);
+                            str[c++] = ch;
+                            size--;
+                        }
+                        ret++;
+                        break;
+                    }
+                    case 's': {
+                        char *stri = va_arg(ap, char *);
+                        if (!stri)
+                            stri = "[NULL STR]";
+                        if (str) {
+                            while (*stri) {
+                                if (size) {
+                                    str[c++] = *(stri++);
+                                    size--;
+                                    ret++;
+                                } else {
+                                    return ret;
+                                }
+                            }
+                        } else {
+                            ret += strlen(stri);
+                        }
+                        break;
+                    }
+                    case '%':
+                        if (str) {
+                            str[c++] = '%';
+                            size--;
+                        }
+                        ret++;
+                        break;
+                    case 'l':
+                        switch (format[i + 2]) {
+                            case 'l':
+                                switch (format[i + 3]) {
+                                    case 'd': {
+                                        int s;
+                                        long long int d = va_arg(ap, long long int);
+                                        if (str)
+                                            s = printInt64(d, &str[c], size);
+                                        else
+                                            s = printInt64(d, NULL, size);
+
+                                        size -= s;
+                                        c += s;
+                                        ret += s;
+                                        break;
+                                    }
+                                    case 'p':
+                                    case 'x': {
+                                        char val[sizeof(long long int) * 2];
+                                        unsigned int valIdx = 0;
+                                        long long int d     = va_arg(ap, long long int);
+                                        itoa(d, val, 16);
+                                        if (str) {
+                                            while (val[valIdx]) {
+                                                if (size) {
+                                                    str[c++] = val[valIdx++];
+                                                    size--;
+                                                    ret++;
+                                                } else {
+                                                    return ret;
+                                                }
+                                            }
+                                        } else {
+                                            ret += strlen(val);
+                                        }
+                                        break;
+                                    }
+                                }
+                                i++;
+                                break;
+                            case 'i':
+                            case 'd': {
+                                int s;
+                                long int d = va_arg(ap, long int);
+                                if (str)
+                                    s = printInt64(d, &str[c], size);
+                                else
+                                    s = printInt64(d, NULL, size);
+
+                                size -= s;
+                                c += s;
+                                ret += s;
+                                break;
+                            }
+                        }
+                        i++;
+                        break;
+                }
+                i++;
+                break;
+
+            default:
+                if (str) {
+                    str[c++] = format[i];
+                    size--;
+                }
+                ret++;
+        }
+        i++;
+    }
+
+    if (str) {
+        if (size) {
+            str[c++] = '\0';
+            size--;
+        } else {
+            if (c > 0) {
+                str[c - 1] = '\0';
+            }
+        }
+    }
+
+    return ret;
+}
+
+int vprintf(const char *fmt, va_list ap)
+{
+    char tmp[256];
+    int idx = 0;
+    int ret = vsnprintf(tmp, sizeof(tmp), fmt, ap);
+    while (ret > 0 && tmp[idx]) {
+        putc(tmp[idx++]);
+    }
+    return ret;
+}
+
+int asprintf(char **strp, const char *fmt, ...)
+{
+    int ret;
+
+    va_list ap;
+    va_start(ap, fmt);
+    ret = vasprintf(strp, fmt, ap);
+    va_end(ap);
+
+    return ret;
+}
+
+int vasprintf(char **strp, const char *fmt, va_list ap)
+{
+    int n       = 0;
+    size_t size = 0;
+    char p[256]; //TODO replace by malloc
+
+    /* Determine required size */
+
+    n = vsnprintf(p, size, fmt, ap);
+
+    if (n < 0)
+        return -1;
+
+    /* One extra byte for '\0' */
+
+    size = min(256U,(size_t)n + 1);
+
+    n = vsnprintf(p, size, fmt, ap);
+
+    if (n < 0) {
+        return -1;
+    }
+	*strp = p;
+
+    return size;
+}
+
+int syscall3(int id, unsigned int arg1, unsigned int arg2, unsigned int arg3)
+{
+    int ret;
+
+    asm volatile("movl %1,%%eax \n"
+                 "movl %2,%%ebx \n"
+                 "movl %3,%%ecx \n"
+                 "movl %4,%%edx \n"
+                 "int  %5\n"
+                 "movl %%eax, %0"
+                 : "=g"(ret)
+                 : "g"(id), "g"(arg1), "g"(arg2), "g"(arg3), "i"(SYSCALL_INTR_NB)
+                 : "eax", "ebx", "ecx", "edx");
+
+    return ret;
+}
+
+int syscall2(int id, unsigned int arg1, unsigned int arg2)
+{
+    return syscall3(id, arg1, arg2, 0);
+}
+
+int syscall1(int id, unsigned int arg1)
+{
+    return syscall3(id, arg1, 0, 0);
+}
+
+int syscall0(int id)
+{
+    return syscall3(id, 0, 0, 0);
+}
+
+void _exit(int status)
+{
+    syscall1(SYSCALL_ID_EXIT, status);
+}
+
+int putc(const int c){
+    return syscall1(SYSCALL_ID_PUTC, c);
+}
+
+void yolo()
+{
+    syscall0(SYSCALL_ID_YOLO);
+}

userspace/libc.h

@@ -0,0 +1,39 @@
+#pragma once
+#include "assert.h"
+#include "stdarg.h"
+#include "minmax.h"
+
+#define islower(c) (('a' <= (c)) && ((c) <= 'z'))
+#define isupper(c) (('A' <= (c)) && ((c) <= 'Z'))
+#define isdigit(c) (('0' <= (c)) && ((c) <= '9'))
+#define isspace(c)                                                                            \
+    (((c) == ' ') || ((c) == '\t') || ((c) == '\f') || ((c) == '\n') || ((c) == '\r') ||      \
+     ((c) == '\v'))
+#define isprint(c) ((' ' <= (c)) && ((c) <= '~'))
+
+int memcmp(const void *s1, const void *s2, size_t n);
+void *memcpy(void *dest, const void *src, size_t n);
+void *memset(void *s, int c, size_t n);
+char *itoa(long long int value, char *str, int base);
+void reverse(char s[]);
+int strlen(const char s[]);
+unsigned int strnlen(const char *s, size_t count);
+int strcmp(const char s1[], const char s2[]);
+char *strzcpy(char *dst, const char *src, int len);
+int puts(const char *str);
+int putc(const int c);
+int vsnprintf(char *str, size_t size, const char *format, va_list ap);
+int vprintf(const char *format, va_list ap);
+int printf(const char *format, ...);
+
+// Could be used after malloc is available
+int asprintf(char **strp, const char *fmt, ...);
+int vasprintf(char **strp, const char *fmt, va_list ap);
+
+int syscall3(int id, unsigned int arg1, unsigned int arg2, unsigned int arg3);
+int syscall2(int id, unsigned int arg1, unsigned int arg2);
+int syscall1(int id, unsigned int arg1);
+int syscall0(int id);
+
+void _exit(int status);
+void yolo();

userspace/linker.ld

@@ -0,0 +1,33 @@
+OUTPUT_FORMAT(elf32-i386);
+/* C entry point: used by crt.c*/
+ENTRY(_start)
+
+SECTIONS
+{
+   /* Userspace vitual address PAGING_BASE_USER_ADDRESS */
+	. = 0x40000000;
+
+	.text : ALIGN(4096)
+	{
+		*(.text)
+	}
+
+	/* Read-only data. */
+	.rodata : ALIGN(4096)
+	{
+		*(.rodata)
+	}
+
+	/* Read-write data (initialized) */
+	.data : ALIGN(4096)
+	{
+		*(.data)
+	}
+
+	/* Read-write data (uninitialized) and stack */
+	.bss : ALIGN(4096)
+	{
+		*(COMMON)
+		*(.bss)
+	}
+}

userspace/main_user.c

@@ -0,0 +1,12 @@
+#include "libc.h"
+
+int main(int argc, char *argv[])
+{
+        (void)argc;
+        (void)argv;
+        yolo();
+        printf("User is about to suicide\n");
+        int *yolo =0;
+        *yolo = 1;
+        return 0;
+}

userspace/math.c

@@ -0,0 +1,9 @@
+#include "math.h"
+
+inline uint32_t log2(const uint32_t x)
+{
+    uint32_t y;
+    // Get the highest set bit
+    asm("\tbsr %1, %0\n" : "=r"(y) : "r"(x));
+    return y;
+}

userspace/math.h

@@ -0,0 +1,5 @@
+#pragma once
+#include "stdarg.h"
+#include "types.h"
+
+uint32_t log2(uint32_t x);

userspace/minmax.h

@@ -0,0 +1,169 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_MINMAX_H
+#define _LINUX_MINMAX_H
+
+/*
+ * From linux kernel include/linux/compiler_types.h
+ */
+#define ___PASTE(a,b) a##b
+#define __PASTE(a,b) ___PASTE(a,b)
+
+/*
+ * From Linux kernel include/linux/compiler.h
+ */
+/* Not-quite-unique ID. */
+#ifndef __UNIQUE_ID
+# define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__)
+#endif
+
+
+
+/*
+ * min()/max()/clamp() macros must accomplish three things:
+ *
+ * - avoid multiple evaluations of the arguments (so side-effects like
+ *   "x++" happen only once) when non-constant.
+ * - perform strict type-checking (to generate warnings instead of
+ *   nasty runtime surprises). See the "unnecessary" pointer comparison
+ *   in __typecheck().
+ * - retain result as a constant expressions when called with only
+ *   constant expressions (to avoid tripping VLA warnings in stack
+ *   allocation usage).
+ */
+#define __typecheck(x, y) \
+	(!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
+
+/*
+ * This returns a constant expression while determining if an argument is
+ * a constant expression, most importantly without evaluating the argument.
+ * Glory to Martin Uecker <Martin.Uecker@med.uni-goettingen.de>
+ */
+#define __is_constexpr(x) \
+	(sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8)))
+
+#define __no_side_effects(x, y) \
+		(__is_constexpr(x) && __is_constexpr(y))
+
+#define __safe_cmp(x, y) \
+		(__typecheck(x, y) && __no_side_effects(x, y))
+
+#define __cmp(x, y, op)	((x) op (y) ? (x) : (y))
+
+#define __cmp_once(x, y, unique_x, unique_y, op) ({	\
+		typeof(x) unique_x = (x);		\
+		typeof(y) unique_y = (y);		\
+		__cmp(unique_x, unique_y, op); })
+
+#define __careful_cmp(x, y, op) \
+	__builtin_choose_expr(__safe_cmp(x, y), \
+		__cmp(x, y, op), \
+		__cmp_once(x, y, __UNIQUE_ID(__x), __UNIQUE_ID(__y), op))
+
+/**
+ * min - return minimum of two values of the same or compatible types
+ * @x: first value
+ * @y: second value
+ */
+#define min(x, y)	__careful_cmp(x, y, <)
+
+/**
+ * max - return maximum of two values of the same or compatible types
+ * @x: first value
+ * @y: second value
+ */
+#define max(x, y)	__careful_cmp(x, y, >)
+
+/**
+ * min3 - return minimum of three values
+ * @x: first value
+ * @y: second value
+ * @z: third value
+ */
+#define min3(x, y, z) min((typeof(x))min(x, y), z)
+
+/**
+ * max3 - return maximum of three values
+ * @x: first value
+ * @y: second value
+ * @z: third value
+ */
+#define max3(x, y, z) max((typeof(x))max(x, y), z)
+
+/**
+ * min_not_zero - return the minimum that is _not_ zero, unless both are zero
+ * @x: value1
+ * @y: value2
+ */
+#define min_not_zero(x, y) ({			\
+	typeof(x) __x = (x);			\
+	typeof(y) __y = (y);			\
+	__x == 0 ? __y : ((__y == 0) ? __x : min(__x, __y)); })
+
+/**
+ * clamp - return a value clamped to a given range with strict typechecking
+ * @val: current value
+ * @lo: lowest allowable value
+ * @hi: highest allowable value
+ *
+ * This macro does strict typechecking of @lo/@hi to make sure they are of the
+ * same type as @val.  See the unnecessary pointer comparisons.
+ */
+#define clamp(val, lo, hi) min((typeof(val))max(val, lo), hi)
+
+/*
+ * ..and if you can't take the strict
+ * types, you can specify one yourself.
+ *
+ * Or not use min/max/clamp at all, of course.
+ */
+
+/**
+ * min_t - return minimum of two values, using the specified type
+ * @type: data type to use
+ * @x: first value
+ * @y: second value
+ */
+#define min_t(type, x, y)	__careful_cmp((type)(x), (type)(y), <)
+
+/**
+ * max_t - return maximum of two values, using the specified type
+ * @type: data type to use
+ * @x: first value
+ * @y: second value
+ */
+#define max_t(type, x, y)	__careful_cmp((type)(x), (type)(y), >)
+
+/**
+ * clamp_t - return a value clamped to a given range using a given type
+ * @type: the type of variable to use
+ * @val: current value
+ * @lo: minimum allowable value
+ * @hi: maximum allowable value
+ *
+ * This macro does no typechecking and uses temporary variables of type
+ * @type to make all the comparisons.
+ */
+#define clamp_t(type, val, lo, hi) min_t(type, max_t(type, val, lo), hi)
+
+/**
+ * clamp_val - return a value clamped to a given range using val's type
+ * @val: current value
+ * @lo: minimum allowable value
+ * @hi: maximum allowable value
+ *
+ * This macro does no typechecking and uses temporary variables of whatever
+ * type the input argument @val is.  This is useful when @val is an unsigned
+ * type and @lo and @hi are literals that will otherwise be assigned a signed
+ * integer type.
+ */
+#define clamp_val(val, lo, hi) clamp_t(typeof(val), val, lo, hi)
+
+/**
+ * swap - swap values of @a and @b
+ * @a: first value
+ * @b: second value
+ */
+#define swap(a, b) \
+	do { typeof(a) __tmp = (a); (a) = (b); (b) = __tmp; } while (0)
+
+#endif	/* _LINUX_MINMAX_H */

userspace/stdarg.h

@@ -0,0 +1,54 @@
+#pragma once
+
+typedef __signed__ char __s8;
+typedef unsigned char __u8;
+
+typedef __signed__ short __s16;
+typedef unsigned short __u16;
+
+typedef __signed__ int __s32;
+typedef unsigned int __u32;
+
+#ifdef __GNUC__
+__extension__ typedef __signed__ long long __s64;
+__extension__ typedef unsigned long long __u64;
+#else
+typedef __signed__ long long __s64;
+typedef unsigned long long __u64;
+#endif
+
+/* sysv */
+typedef unsigned char unchar;
+typedef unsigned short ushort;
+typedef unsigned int uint;
+typedef unsigned long ulong;
+
+typedef __s8 int8_t;
+typedef __s16 int16_t;
+typedef __s32 int32_t;
+
+typedef __u8 uint8_t;
+typedef __u16 uint16_t;
+typedef __u32 uint32_t;
+
+typedef __u64 uint64_t;
+typedef __u64 u_int64_t;
+typedef __s64 int64_t;
+
+typedef enum { FALSE = 0, TRUE } bool_t;
+#define NULL ((void *)0)
+
+#if __x86_64__
+typedef unsigned long size_t;
+typedef long ssize_t;
+typedef unsigned long int uintptr_t;
+#else
+typedef unsigned int size_t;
+typedef int ssize_t;
+typedef unsigned int uintptr_t;
+#endif
+
+typedef void *va_list;
+#define va_start(v, l) ((v) = (va_list) & (l) + sizeof(l))
+#define va_end(v) ((v) = NULL)
+#define va_arg(v, type) (*(type *)(((v) += sizeof(type)) - sizeof(type)))

userspace/types.h

@@ -0,0 +1,38 @@
+#pragma once
+
+#define USHRT_MAX ((u16)(~0U))
+#define SHRT_MAX ((s16)(USHRT_MAX >> 1))
+#define SHRT_MIN ((s16)(-SHRT_MAX - 1))
+#define INT_MAX ((int)(~0U >> 1))
+#define INT_MIN (-INT_MAX - 1)
+#define UINT_MAX (~0U)
+#define LONG_MAX ((long)(~0UL >> 1))
+#define LONG_MIN (-LONG_MAX - 1)
+#define ULONG_MAX (~0UL)
+#define LLONG_MAX ((long long)(~0ULL >> 1))
+#define LLONG_MIN (-LLONG_MAX - 1)
+#define ULLONG_MAX (~0ULL)
+#define SIZE_MAX (~(size_t)0)
+#define PHYS_ADDR_MAX (~(phys_addr_t)0)
+
+#define U8_MAX ((u8)~0U)
+#define S8_MAX ((s8)(U8_MAX >> 1))
+#define S8_MIN ((s8)(-S8_MAX - 1))
+#define U16_MAX ((u16)~0U)
+#define S16_MAX ((s16)(U16_MAX >> 1))
+#define S16_MIN ((s16)(-S16_MAX - 1))
+#define U32_MAX ((u32)~0U)
+#define S32_MAX ((s32)(U32_MAX >> 1))
+#define S32_MIN ((s32)(-S32_MAX - 1))
+#define U64_MAX ((u64)~0ULL)
+#define S64_MAX ((s64)(U64_MAX >> 1))
+#define S64_MIN ((s64)(-S64_MAX - 1))
+
+// Virtual address
+typedef unsigned long vaddr_t;
+
+// Physical address
+typedef unsigned long paddr_t;
+
+// Userspace vaddr
+typedef unsigned long uaddr_t;