On 04.04.24 01:34, Deepak Gupta wrote:
VM_SHADOW_STACK (alias to VM_HIGH_ARCH_5) to encode shadow stack VMA.
This patch changes checks of VM_SHADOW_STACK flag in generic code to call to a function `vma_is_shadow_stack` which will return true if its a shadow stack vma and default stub (when support doesnt exist) returns false.
Signed-off-by: Deepak Gupta debug@rivosinc.com Suggested-by: Mike Rapoport rppt@kernel.org
include/linux/mm.h | 13 ++++++++++++- mm/gup.c | 5 +++-- mm/internal.h | 2 +- 3 files changed, 16 insertions(+), 4 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h index 64109f6c70f5..9952937be659 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -363,8 +363,19 @@ extern unsigned int kobjsize(const void *objp); #ifndef VM_SHADOW_STACK # define VM_SHADOW_STACK VM_NONE
+static inline bool vma_is_shadow_stack(vm_flags_t vm_flags) +{
- return false;
+} +#else +static inline bool vma_is_shadow_stack(vm_flags_t vm_flags) +{
- return (vm_flags & VM_SHADOW_STACK);
+} #endif
You can simply do outside the ifdef
static inline bool vma_is_shadow_stack(vm_flags_t vm_flags) { return !!(vm_flags & VM_SHADOW_STACK); }
This will work even when VM_SHADOW_STACK is defined to be VM_NONE.
unrelated code change
#if defined(CONFIG_X86) # define VM_PAT VM_ARCH_1 /* PAT reserves whole VMA at once (x86) */ #elif defined(CONFIG_PPC) @@ -3473,7 +3484,7 @@ static inline unsigned long stack_guard_start_gap(struct vm_area_struct *vma) return stack_guard_gap; /* See reasoning around the VM_SHADOW_STACK definition */
- if (vma->vm_flags & VM_SHADOW_STACK)
- if (vma->vm_flags && vma_is_shadow_stack(vma->vm_flags))
Pretty sure:
if (vma_is_shadow_stack(vma->vm_flags))
return PAGE_SIZE;return 0; diff --git a/mm/gup.c b/mm/gup.c index df83182ec72d..a7a02eb0a6b3 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1053,7 +1053,7 @@ 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) || vma_is_shadow_stack(vm_flags)) { if (!(gup_flags & FOLL_FORCE)) return -EFAULT; /* hugetlb does not support FOLL_FORCE|FOLL_WRITE. */@@ -1071,7 +1071,8 @@ static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags) if (!is_cow_mapping(vm_flags)) return -EFAULT; }
- } else if (!(vm_flags & VM_READ)) {
- } else if (!(vm_flags & VM_READ) && !vma_is_shadow_stack(vm_flags)) {
- /* reads allowed if its shadow stack vma */ if (!(gup_flags & FOLL_FORCE)) return -EFAULT; /*
Unless I am missing something, this is not a simple cleanup. It should go into a separate patch with a clearly documented reason for that change.