diff --git a/asm.h b/asm.h
index b8a7353e4c..599479c818 100644
--- a/asm.h
+++ b/asm.h
@@ -1,3 +1,5 @@
+#ifndef ASM_H_5FC4D1F4_CAAF_11EE_AA2B_90B11C0C0FF8
+#define ASM_H_5FC4D1F4_CAAF_11EE_AA2B_90B11C0C0FF8
 //
 // assembler macros to create x86 segments
 //
@@ -16,3 +18,4 @@
 #define STA_X     0x8       // Executable segment
 #define STA_W     0x2       // Writeable (non-executable segments)
 #define STA_R     0x2       // Readable (executable segments)
+#endif
diff --git a/buf.h b/buf.h
index 3266495cf3..61e8145eba 100644
--- a/buf.h
+++ b/buf.h
@@ -1,3 +1,5 @@
+#ifndef BUF_H_5FB86900_CAAF_11EE_8313_90B11C0C0FF8
+#define BUF_H_5FB86900_CAAF_11EE_8313_90B11C0C0FF8
 struct buf {
   int flags;
   uint dev;
@@ -12,3 +14,4 @@ struct buf {
 #define B_VALID 0x2  // buffer has been read from disk
 #define B_DIRTY 0x4  // buffer needs to be written to disk
 
+#endif
diff --git a/date.h b/date.h
index 94aec4b77d..c393c4f62f 100644
--- a/date.h
+++ b/date.h
@@ -1,3 +1,5 @@
+#ifndef DATE_H_5FBD64BE_CAAF_11EE_B4B1_90B11C0C0FF8
+#define DATE_H_5FBD64BE_CAAF_11EE_B4B1_90B11C0C0FF8
 struct rtcdate {
   uint second;
   uint minute;
@@ -6,3 +8,4 @@ struct rtcdate {
   uint month;
   uint year;
 };
+#endif
diff --git a/defs.h b/defs.h
index 82fb982837..bb3f5dc11a 100644
--- a/defs.h
+++ b/defs.h
@@ -1,3 +1,5 @@
+#ifndef DEFS_H_5FCEEDA6_CAAF_11EE_B851_90B11C0C0FF8
+#define DEFS_H_5FCEEDA6_CAAF_11EE_B851_90B11C0C0FF8
 struct buf;
 struct context;
 struct file;
@@ -188,3 +190,4 @@ void            clearpteu(pde_t *pgdir, char *uva);
 
 // number of elements in fixed-size array
 #define NELEM(x) (sizeof(x)/sizeof((x)[0]))
+#endif
diff --git a/elf.h b/elf.h
index d16c96753a..5dcb4cb756 100644
--- a/elf.h
+++ b/elf.h
@@ -1,3 +1,5 @@
+#ifndef ELF_H_5FA195AE_CAAF_11EE_8AD1_90B11C0C0FF8
+#define ELF_H_5FA195AE_CAAF_11EE_8AD1_90B11C0C0FF8
 // Format of an ELF executable file
 
 #define ELF_MAGIC 0x464C457FU  // "\x7FELF" in little endian
@@ -40,3 +42,4 @@ struct proghdr {
 #define ELF_PROG_FLAG_EXEC      1
 #define ELF_PROG_FLAG_WRITE     2
 #define ELF_PROG_FLAG_READ      4
+#endif
diff --git a/fcntl.h b/fcntl.h
index d565483ad9..8d26504958 100644
--- a/fcntl.h
+++ b/fcntl.h
@@ -1,4 +1,7 @@
+#ifndef FCNTL_H_5FB34556_CAAF_11EE_8D47_90B11C0C0FF8
+#define FCNTL_H_5FB34556_CAAF_11EE_8D47_90B11C0C0FF8
 #define O_RDONLY  0x000
 #define O_WRONLY  0x001
 #define O_RDWR    0x002
 #define O_CREATE  0x200
+#endif
diff --git a/file.h b/file.h
index 0990c82f46..f32685e094 100644
--- a/file.h
+++ b/file.h
@@ -1,3 +1,5 @@
+#ifndef FILE_H_5FBFEB30_CAAF_11EE_B018_90B11C0C0FF8
+#define FILE_H_5FBFEB30_CAAF_11EE_B018_90B11C0C0FF8
 struct file {
   enum { FD_NONE, FD_PIPE, FD_INODE } type;
   int ref; // reference count
@@ -35,3 +37,4 @@ struct devsw {
 extern struct devsw devsw[];
 
 #define CONSOLE 1
+#endif
diff --git a/fs.h b/fs.h
index 3214f1d7f7..6ee818cdbc 100644
--- a/fs.h
+++ b/fs.h
@@ -1,3 +1,5 @@
+#ifndef FS_H_5FC27350_CAAF_11EE_8DCB_90B11C0C0FF8
+#define FS_H_5FC27350_CAAF_11EE_8DCB_90B11C0C0FF8
 // On-disk file system format.
 // Both the kernel and user programs use this header file.
 
@@ -55,3 +57,4 @@ struct dirent {
   char name[DIRSIZ];
 };
 
+#endif
diff --git a/kbd.h b/kbd.h
index babbd6ed4e..79da4876f8 100644
--- a/kbd.h
+++ b/kbd.h
@@ -1,3 +1,5 @@
+#ifndef KBD_H_5FC7143C_CAAF_11EE_A572_90B11C0C0FF8
+#define KBD_H_5FC7143C_CAAF_11EE_A572_90B11C0C0FF8
 // PC keyboard interface constants
 
 #define KBSTATP         0x64    // kbd controller status port(I)
@@ -110,3 +112,4 @@ static uchar ctlmap[256] =
   [0xD2] KEY_INS,   [0xD3] KEY_DEL
 };
 
+#endif
diff --git a/memlayout.h b/memlayout.h
index d1615f7abc..e85069d301 100644
--- a/memlayout.h
+++ b/memlayout.h
@@ -1,3 +1,5 @@
+#ifndef MEMLAYOUT_H_5FABE5CC_CAAF_11EE_9944_90B11C0C0FF8
+#define MEMLAYOUT_H_5FABE5CC_CAAF_11EE_9944_90B11C0C0FF8
 // Memory layout
 
 #define EXTMEM  0x100000            // Start of extended memory
@@ -13,3 +15,4 @@
 
 #define V2P_WO(x) ((x) - KERNBASE)    // same as V2P, but without casts
 #define P2V_WO(x) ((x) + KERNBASE)    // same as P2V, but without casts
+#endif
diff --git a/mmu.h b/mmu.h
index a82d8e26ec..c347d68fde 100644
--- a/mmu.h
+++ b/mmu.h
@@ -1,3 +1,5 @@
+#ifndef MMU_H_5FCC4614_CAAF_11EE_B100_90B11C0C0FF8
+#define MMU_H_5FCC4614_CAAF_11EE_B100_90B11C0C0FF8
 // This file contains definitions for the
 // x86 memory management unit (MMU).
 
@@ -179,3 +181,4 @@ struct gatedesc {
 }
 
 #endif
+#endif
diff --git a/mp.h b/mp.h
index 4d172839bb..18c97c1927 100644
--- a/mp.h
+++ b/mp.h
@@ -1,3 +1,5 @@
+#ifndef MP_H_5FA4371E_CAAF_11EE_9652_90B11C0C0FF8
+#define MP_H_5FA4371E_CAAF_11EE_9652_90B11C0C0FF8
 // See MultiProcessor Specification Version 1.[14]
 
 struct mp {             // floating pointer
@@ -54,3 +56,4 @@ struct mpioapic {       // I/O APIC table entry
 
 //PAGEBREAK!
 // Blank page.
+#endif
diff --git a/param.h b/param.h
index a7e90efff4..a8e11347c3 100644
--- a/param.h
+++ b/param.h
@@ -1,3 +1,5 @@
+#ifndef PARAM_H_5FA945E2_CAAF_11EE_ADF4_90B11C0C0FF8
+#define PARAM_H_5FA945E2_CAAF_11EE_ADF4_90B11C0C0FF8
 #define NPROC        64  // maximum number of processes
 #define KSTACKSIZE 4096  // size of per-process kernel stack
 #define NCPU          8  // maximum number of CPUs
@@ -12,3 +14,4 @@
 #define NBUF         (MAXOPBLOCKS*3)  // size of disk block cache
 #define FSSIZE       1000  // size of file system in blocks
 
+#endif
diff --git a/proc.h b/proc.h
index 1647114179..827a69a564 100644
--- a/proc.h
+++ b/proc.h
@@ -1,3 +1,5 @@
+#ifndef PROC_H_5FBAE11C_CAAF_11EE_B85B_90B11C0C0FF8
+#define PROC_H_5FBAE11C_CAAF_11EE_B85B_90B11C0C0FF8
 // Per-CPU state
 struct cpu {
   uchar apicid;                // Local APIC ID
@@ -56,3 +58,4 @@ struct proc {
 //   original data and bss
 //   fixed-size stack
 //   expandable heap
+#endif
diff --git a/sleeplock.h b/sleeplock.h
index 110e6f3d7f..de77151dfd 100644
--- a/sleeplock.h
+++ b/sleeplock.h
@@ -1,3 +1,5 @@
+#ifndef SLEEPLOCK_H_5FB5EE8C_CAAF_11EE_B022_90B11C0C0FF8
+#define SLEEPLOCK_H_5FB5EE8C_CAAF_11EE_B022_90B11C0C0FF8
 // Long-term locks for processes
 struct sleeplock {
   uint locked;       // Is the lock held?
@@ -8,3 +10,4 @@ struct sleeplock {
   int pid;           // Process holding lock
 };
 
+#endif
diff --git a/spinlock.h b/spinlock.h
index 0a9d8e23a7..ce6fdb3bf4 100644
--- a/spinlock.h
+++ b/spinlock.h
@@ -1,3 +1,5 @@
+#ifndef SPINLOCK_H_5FAE6694_CAAF_11EE_AA29_90B11C0C0FF8
+#define SPINLOCK_H_5FAE6694_CAAF_11EE_AA29_90B11C0C0FF8
 // Mutual exclusion lock.
 struct spinlock {
   uint locked;       // Is the lock held?
@@ -9,3 +11,4 @@ struct spinlock {
                      // that locked the lock.
 };
 
+#endif
diff --git a/stat.h b/stat.h
index 8a809339f4..d439bd9b9f 100644
--- a/stat.h
+++ b/stat.h
@@ -1,3 +1,5 @@
+#ifndef STAT_H_5F9EF308_CAAF_11EE_9131_90B11C0C0FF8
+#define STAT_H_5F9EF308_CAAF_11EE_9131_90B11C0C0FF8
 #define T_DIR  1   // Directory
 #define T_FILE 2   // File
 #define T_DEV  3   // Device
@@ -9,3 +11,4 @@ struct stat {
   short nlink; // Number of links to file
   uint size;   // Size of file in bytes
 };
+#endif
diff --git a/syscall.h b/syscall.h
index bc5f35651c..bedbf85d94 100644
--- a/syscall.h
+++ b/syscall.h
@@ -1,3 +1,5 @@
+#ifndef SYSCALL_H_5FC98D3E_CAAF_11EE_81F6_90B11C0C0FF8
+#define SYSCALL_H_5FC98D3E_CAAF_11EE_81F6_90B11C0C0FF8
 // System call numbers
 #define SYS_fork    1
 #define SYS_exit    2
@@ -20,3 +22,4 @@
 #define SYS_link   19
 #define SYS_mkdir  20
 #define SYS_close  21
+#endif
diff --git a/traps.h b/traps.h
index 0bd1fd8454..d570f1be88 100644
--- a/traps.h
+++ b/traps.h
@@ -1,3 +1,5 @@
+#ifndef TRAPS_H_5FD18188_CAAF_11EE_ADFC_90B11C0C0FF8
+#define TRAPS_H_5FD18188_CAAF_11EE_ADFC_90B11C0C0FF8
 // x86 trap and interrupt constants.
 
 // Processor-defined:
@@ -36,3 +38,4 @@
 #define IRQ_ERROR       19
 #define IRQ_SPURIOUS    31
 
+#endif
diff --git a/types.h b/types.h
index e4adf644ae..c9b2426c59 100644
--- a/types.h
+++ b/types.h
@@ -1,4 +1,7 @@
+#ifndef TYPES_H_5FA6C7AE_CAAF_11EE_B06B_90B11C0C0FF8
+#define TYPES_H_5FA6C7AE_CAAF_11EE_B06B_90B11C0C0FF8
 typedef unsigned int   uint;
 typedef unsigned short ushort;
 typedef unsigned char  uchar;
 typedef uint pde_t;
+#endif
diff --git a/user.h b/user.h
index 4f99c52ba6..0acb10e457 100644
--- a/user.h
+++ b/user.h
@@ -1,3 +1,5 @@
+#ifndef USER_H_5FB0CF7E_CAAF_11EE_B782_90B11C0C0FF8
+#define USER_H_5FB0CF7E_CAAF_11EE_B782_90B11C0C0FF8
 struct stat;
 struct rtcdate;
 
@@ -37,3 +39,4 @@ void* memset(void*, int, uint);
 void* malloc(uint);
 void free(void*);
 int atoi(const char*);
+#endif
diff --git a/x86.h b/x86.h
index 07312a539f..5414af3923 100644
--- a/x86.h
+++ b/x86.h
@@ -1,3 +1,5 @@
+#ifndef X86_H_5F9C3CA8_CAAF_11EE_B26D_90B11C0C0FF8
+#define X86_H_5F9C3CA8_CAAF_11EE_B26D_90B11C0C0FF8
 // Routines to let C code use special x86 instructions.
 
 static inline uchar
@@ -181,3 +183,4 @@ struct trapframe {
   ushort ss;
   ushort padding6;
 };
+#endif