[PW_SID:1057353] mm: arch/shstk: Common shadow stack mapping helper and VM_NOHUGEPAGE

arch/arm64/mm/gcs.c

@@ -12,19 +12,7 @@
 
 static unsigned long alloc_gcs(unsigned long addr, unsigned long size)
 {
-	int flags = MAP_ANONYMOUS | MAP_PRIVATE;
-	struct mm_struct *mm = current->mm;
-	unsigned long mapped_addr, unused;
-
-	if (addr)
-		flags |= MAP_FIXED_NOREPLACE;
-
-	mmap_write_lock(mm);
-	mapped_addr = do_mmap(NULL, addr, size, PROT_READ, flags,
-			      VM_SHADOW_STACK | VM_WRITE, 0, &unused, NULL);
-	mmap_write_unlock(mm);
-
-	return mapped_addr;
+	return vm_mmap_shadow_stack(addr, size, 0);
 }
 
 static unsigned long gcs_size(unsigned long size)

arch/riscv/kernel/usercfi.c

@@ -230,17 +230,7 @@ int restore_user_shstk(struct task_struct *tsk, unsigned long shstk_ptr)
 static unsigned long allocate_shadow_stack(unsigned long addr, unsigned long size,
 					   unsigned long token_offset, bool set_tok)
 {
-	int flags = MAP_ANONYMOUS | MAP_PRIVATE;
-	struct mm_struct *mm = current->mm;
-	unsigned long populate;
-
-	if (addr)
-		flags |= MAP_FIXED_NOREPLACE;
-
-	mmap_write_lock(mm);
-	addr = do_mmap(NULL, addr, size, PROT_READ, flags,
-		       VM_SHADOW_STACK | VM_WRITE, 0, &populate, NULL);
-	mmap_write_unlock(mm);
+	addr = vm_mmap_shadow_stack(addr, size, 0);
 
 	if (!set_tok || IS_ERR_VALUE(addr))
 		goto out;

arch/x86/kernel/shstk.c

@@ -100,17 +100,9 @@ static int create_rstor_token(unsigned long ssp, unsigned long *token_addr)
 static unsigned long alloc_shstk(unsigned long addr, unsigned long size,
 				 unsigned long token_offset, bool set_res_tok)
 {
-	int flags = MAP_ANONYMOUS | MAP_PRIVATE | MAP_ABOVE4G;
-	struct mm_struct *mm = current->mm;
-	unsigned long mapped_addr, unused;
+	unsigned long mapped_addr;
 
-	if (addr)
-		flags |= MAP_FIXED_NOREPLACE;
-
-	mmap_write_lock(mm);
-	mapped_addr = do_mmap(NULL, addr, size, PROT_READ, flags,
-			      VM_SHADOW_STACK | VM_WRITE, 0, &unused, NULL);
-	mmap_write_unlock(mm);
+	mapped_addr = vm_mmap_shadow_stack(addr, size, MAP_ABOVE4G);
 
 	if (!set_res_tok || IS_ERR_VALUE(mapped_addr))
 		goto out;

include/linux/mm.h

@@ -3698,6 +3698,10 @@ extern int vm_munmap(unsigned long, size_t);
 extern unsigned long __must_check vm_mmap(struct file *, unsigned long,
         unsigned long, unsigned long,
         unsigned long, unsigned long);
+#ifdef CONFIG_ARCH_HAS_USER_SHADOW_STACK
+extern unsigned long __must_check vm_mmap_shadow_stack(unsigned long addr,
+	unsigned long len, unsigned long flags);
+#endif
 
 struct vm_unmapped_area_info {
 #define VM_UNMAPPED_AREA_TOPDOWN 1

mm/util.c

@@ -618,6 +618,35 @@ unsigned long vm_mmap(struct file *file, unsigned long addr,
 }
 EXPORT_SYMBOL(vm_mmap);
 
+#ifdef CONFIG_ARCH_HAS_USER_SHADOW_STACK
+/*
+ * Perform a userland memory mapping for a shadow stack into the current
+ * process address space. This is intended to be used by architectures that
+ * support user shadow stacks.
+ */
+unsigned long vm_mmap_shadow_stack(unsigned long addr, unsigned long len,
+				   unsigned long flags)
+{
+	struct mm_struct *mm = current->mm;
+	unsigned long ret, unused;
+	vm_flags_t vm_flags = VM_SHADOW_STACK;
+
+	flags |= MAP_ANONYMOUS | MAP_PRIVATE;
+	if (addr)
+		flags |= MAP_FIXED_NOREPLACE;
+
+	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
+		vm_flags |= VM_NOHUGEPAGE;
+
+	mmap_write_lock(mm);
+	ret = do_mmap(NULL, addr, len, PROT_READ | PROT_WRITE, flags,
+		      vm_flags, 0, &unused, NULL);
+	mmap_write_unlock(mm);
+
+	return ret;
+}
+#endif /* CONFIG_ARCH_HAS_USER_SHADOW_STACK */
+
 /**
  * __vmalloc_array - allocate memory for a virtually contiguous array.
  * @n: number of elements.