On Fri, Feb 07, 2025 at 10:27:10AM +0100, Vlastimil Babka wrote:
>On 2/5/25 02:21, Deepak Gupta wrote:
>> VM_SHADOW_STACK (alias to VM_HIGH_ARCH_5) is used to encode shadow stack
>
>I see that arm GCS uses VM_HIGH_ARCH_6.
Stale commit message. I thought I had fixed it.
Sorry about that, will fix it.
>
>> VMA on three architectures (x86 shadow stack, arm GCS and RISC-V shadow
>
>And RISC-V doesn't define it at all, not even in this patchset, or did I
>miss it somewhere?
>
>> 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.
>
>This looks like an unfinished sentence. As if it was to continue with "...
>will allow us to ..." what?
>
>I'm not against a helper but this changelog is rather confusing and also
>code in arch/x86 and arch/arm64 isn't converted to the helper but testing
>VM_SHADOW_STACK still.
Yes I didn't pay attention during rebase, will update the commit message.
>
>> 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 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)
>> {
>>
>