diff --git a/arch/x86/kernel/syscall.c b/arch/x86/kernel/syscall.c
index d0b96b83..f44bb66a 100644
--- a/arch/x86/kernel/syscall.c
+++ b/arch/x86/kernel/syscall.c
@@ -27,9 +27,6 @@
 #include <mman.h>
 
 void terminate(int, int);
-int copy_from_user(void *dst, const void *src, size_t siz);
-int copy_to_user(void *dst, const void *src, size_t siz);
-int write_process_vm(struct process_vm *vm, void *dst, const void *src, size_t siz);
 extern long do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact);
 long syscall(int num, ihk_mc_user_context_t *ctx);
 extern void save_fp_regs(struct thread *proc);
diff --git a/kernel/procfs.c b/kernel/procfs.c
index 894268b6..c5479460 100644
--- a/kernel/procfs.c
+++ b/kernel/procfs.c
@@ -38,9 +38,6 @@ extern int sscanf(const char * buf, const char * fmt, ...);
 
 extern int osnum;
 
-int copy_from_user(void *dst, const void *src, size_t siz);
-int copy_to_user(void *dst, const void *src, size_t siz);
-
 static void
 procfs_thread_ctl(struct thread *thread, int msg)
 {
diff --git a/kernel/syscall.c b/kernel/syscall.c
index 163b9ac8..2faa6611 100644
--- a/kernel/syscall.c
+++ b/kernel/syscall.c
@@ -105,10 +105,6 @@ void check_signal(unsigned long, void *, int);
 void do_signal(long rc, void *regs, struct thread *thread, struct sig_pending *pending, int num);
 extern unsigned long do_kill(struct thread *thread, int pid, int tid, int sig, struct siginfo *info, int ptracecont);
 extern struct sigpending *hassigpending(struct thread *thread);
-int copy_from_user(void *, const void *, size_t);
-int read_process_vm(struct process_vm *, void *, const void *, size_t);
-int copy_to_user(void *, const void *, size_t);
-int patch_process_vm(struct process_vm *, void *, const void *, size_t);
 extern long alloc_debugreg(struct thread *thread);
 extern int num_processors;
 extern unsigned long ihk_mc_get_ns_per_tsc(void);
diff --git a/lib/include/memory.h b/lib/include/memory.h
index 0da3a0cd..b4ad4f33 100644
--- a/lib/include/memory.h
+++ b/lib/include/memory.h
@@ -28,8 +28,21 @@ static void *phys_to_virt(unsigned long p)
 }
 #endif
 
+struct process_vm;
+
 unsigned long virt_to_phys(void *v);
 void *phys_to_virt(unsigned long p);
+int copy_from_user(void *dst, const void *src, size_t siz);
+int strlen_user(const char *s);
+int strcpy_from_user(char *dst, const char *src);
+long getlong_user(const long *p);
+int getint_user(const int *p);
+int read_process_vm(struct process_vm *vm, void *kdst, const void *usrc, size_t siz);
+int copy_to_user(void *dst, const void *src, size_t siz);
+int setlong_user(long *dst, long data);
+int setint_user(int *dst, int data);
+int write_process_vm(struct process_vm *vm, void *udst, const void *ksrc, size_t siz);
+int patch_process_vm(struct process_vm *vm, void *udst, const void *ksrc, size_t siz);
 
 #endif
 
diff --git a/lib/string.c b/lib/string.c
index 55a93f7a..711c18fb 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -12,10 +12,7 @@
 
 #include <kmalloc.h>
 #include <string.h>
-
-extern int strlen_user(const char *);
-extern int strcpy_from_user(char *, const char *);
-extern long getlong_user(const void *);
+#include <memory.h>
 
 size_t strlen(const char *p)
 {