On Thu, Jan 25, 2024 at 09:18:07AM +0100, David Hildenbrand wrote:
On 25.01.24 07:21, debug@rivosinc.com wrote:
From: Deepak Gupta debug@rivosinc.com
x86 has used VM_SHADOW_STACK (alias to VM_HIGH_ARCH_5) to encode shadow stack VMA. VM_SHADOW_STACK is thus not possible on 32bit. Some arches may need a way to encode shadow stack on 32bit and 64bit both and they may encode this information differently in VMAs.
This patch changes checks of VM_SHADOW_STACK flag in generic code to call to a function `arch_is_shadow_stack` which will return true if arch supports shadow stack and vma is shadow stack else stub returns false.
There was a suggestion to name it as `vma_is_shadow_stack`. I preferred to keep `arch` prefix in there because it's each arch specific.
Signed-off-by: Deepak Gupta debug@rivosinc.com
include/linux/mm.h | 18 +++++++++++++++++- mm/gup.c | 5 +++-- mm/internal.h | 2 +- 3 files changed, 21 insertions(+), 4 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h index dfe0e8118669..15c70fc677a3 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -352,6 +352,10 @@ extern unsigned int kobjsize(const void *objp);
- for more details on the guard size.
*/ # define VM_SHADOW_STACK VM_HIGH_ARCH_5 +static inline bool arch_is_shadow_stack(vm_flags_t vm_flags) +{
- return (vm_flags & VM_SHADOW_STACK);
+} #endif #ifdef CONFIG_RISCV_USER_CFI @@ -362,10 +366,22 @@ extern unsigned int kobjsize(const void *objp);
- with VM_SHARED.
*/ #define VM_SHADOW_STACK VM_WRITE
+static inline bool arch_is_shadow_stack(vm_flags_t vm_flags) +{
- return ((vm_flags & (VM_WRITE | VM_READ | VM_EXEC)) == VM_WRITE);
+}
Please no such hacks just to work around the 32bit vmflags limitation.
As I said in another response. Noted. And if there're no takers for 32bit on riscv (which highly likely is the case) This will go away in next version of patchsets.
-- Cheers,
David / dhildenb