ia64: Make mremap() work properly when returning "negative" addresses.

	Based on patch by Matt Chapman.

arch/ia64/kernel/entry.S

@@ -1160,7 +1160,7 @@ sys_call_table:
 	data8 sys_mlock
 	data8 sys_mlockall
 	data8 sys_mprotect			// 1155
-	data8 sys_mremap
+	data8 ia64_mremap
 	data8 sys_msync
 	data8 sys_munlock
 	data8 sys_munlockall

arch/ia64/kernel/sys_ia64.c

@@ -316,6 +316,29 @@ sys_free_hugepages (unsigned long  addr)
 
 #endif /* !CONFIG_HUGETLB_PAGE */
 
+asmlinkage unsigned long
+ia64_mremap (unsigned long addr, unsigned long old_len, unsigned long new_len, unsigned long flags,
+	     unsigned long new_addr)
+{
+	extern unsigned long do_mremap (unsigned long addr,
+					unsigned long old_len,
+					unsigned long new_len,
+					unsigned long flags,
+					unsigned long new_addr);
+
+	down_write(&current->mm->mmap_sem);
+	{
+		addr = do_mremap(addr, old_len, new_len, flags, new_addr);
+	}
+	up_write(&current->mm->mmap_sem);
+
+	if (IS_ERR((void *) addr))
+		return addr;
+
+	force_successful_syscall_return();
+	return addr;
+}
+
 asmlinkage long
 sys_vm86 (long arg0, long arg1, long arg2, long arg3)
 {