[PATCH v8 02/29] mm: helper `is_shadow_stack_vma` to check shadow stack vma

Deepak Gupta
2024-11-11T21:06:09Z

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@rivosinc.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
---
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 a82890b46a36..8e6e14179f6c 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1282,7 +1282,7 @@ 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;
/* hugetlb does not support FOLL_FORCE|FOLL_WRITE. */
diff --git a/mm/mmap.c b/mm/mmap.c
index 9c0fb43064b5..f17573469c42 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -708,7 +708,7 @@ static unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info)
*/
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 819f994cf727..0f238dc37231 100644
--- a/mm/vma.h
+++ b/mm/vma.h
@@ -357,7 +357,7 @@ 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.
*/

/*
@@ -368,6 +368,11 @@ 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)
*
@@ -376,7 +381,7 @@ 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);
}

/*
@@ -387,7 +392,6 @@ 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)
{