[PATCH v9 01/26] mm: helper `is_shadow_stack_vma` to check shadow stack vma

[Deepak Gupta <debug@xxxxxxxxxxxx>]

VM_SHADOW_STACK (alias to VM_HIGH_ARCH_5) is used to encode shadow stack
VMA on three architectures (x86 shadow stack, arm GCS and RISC-V shadow
stack). In case architecture doesn't implement shadow stack, it's VM_NONE
Introducing a helper `is_shadow_stack_vma` to determine shadow stack vma
or not.

Signed-off-by: Deepak Gupta <debug@xxxxxxxxxxxx>
Reviewed-by: Mark Brown <broonie@xxxxxxxxxx>
---
 mm/gup.c  |  2 +-
 mm/mmap.c |  2 +-
 mm/vma.h  | 10 +++++++---
 3 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index 3883b307780e..8c64f3ff34ab 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1291,7 +1291,7 @@ static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)
 		    !writable_file_mapping_allowed(vma, gup_flags))
 			return -EFAULT;
 
-		if (!(vm_flags & VM_WRITE) || (vm_flags & VM_SHADOW_STACK)) {
+		if (!(vm_flags & VM_WRITE) || is_shadow_stack_vma(vm_flags)) {
 			if (!(gup_flags & FOLL_FORCE))
 				return -EFAULT;
 			/*
diff --git a/mm/mmap.c b/mm/mmap.c
index cda01071c7b1..7b6be4eec35d 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -648,7 +648,7 @@ SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg)
  */
 static inline unsigned long stack_guard_placement(vm_flags_t vm_flags)
 {
-	if (vm_flags & VM_SHADOW_STACK)
+	if (is_shadow_stack_vma(vm_flags))
 		return PAGE_SIZE;
 
 	return 0;
diff --git a/mm/vma.h b/mm/vma.h
index a2e8710b8c47..47482a25f5c3 100644
--- a/mm/vma.h
+++ b/mm/vma.h
@@ -278,7 +278,7 @@ static inline struct vm_area_struct *vma_prev_limit(struct vma_iterator *vmi,
 }
 
 /*
- * These three helpers classifies VMAs for virtual memory accounting.
+ * These four helpers classifies VMAs for virtual memory accounting.
  */
 
 /*
@@ -289,6 +289,11 @@ static inline bool is_exec_mapping(vm_flags_t flags)
 	return (flags & (VM_EXEC | VM_WRITE | VM_STACK)) == VM_EXEC;
 }
 
+static inline bool is_shadow_stack_vma(vm_flags_t vm_flags)
+{
+	return !!(vm_flags & VM_SHADOW_STACK);
+}
+
 /*
  * Stack area (including shadow stacks)
  *
@@ -297,7 +302,7 @@ static inline bool is_exec_mapping(vm_flags_t flags)
  */
 static inline bool is_stack_mapping(vm_flags_t flags)
 {
-	return ((flags & VM_STACK) == VM_STACK) || (flags & VM_SHADOW_STACK);
+	return ((flags & VM_STACK) == VM_STACK) || is_shadow_stack_vma(flags);
 }
 
 /*
@@ -308,7 +313,6 @@ static inline bool is_data_mapping(vm_flags_t flags)
 	return (flags & (VM_WRITE | VM_SHARED | VM_STACK)) == VM_WRITE;
 }
 
-
 static inline void vma_iter_config(struct vma_iterator *vmi,
 		unsigned long index, unsigned long last)
 {

-- 
2.34.1