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[RFC,v2,08/27] mm: Introduce VM_SHSTK for shadow stack memory

Message ID 20180710222639.8241-9-yu-cheng.yu@intel.com (mailing list archive)
State New, archived
Headers show

Commit Message

Yu, Yu-cheng July 10, 2018, 10:26 p.m. UTC
VM_SHSTK indicates a shadow stack memory area.

A shadow stack PTE must be read-only and dirty.  For non shadow
stack, we use a spare bit of the 64-bit PTE for dirty.  The PTE
changes are in the next patch.

There is no more spare bit in the 32-bit PTE (except for PAE) and
the shadow stack is not implemented for the 32-bit kernel.

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
---
 include/linux/mm.h | 8 ++++++++
 mm/internal.h      | 8 ++++++++
 2 files changed, 16 insertions(+)

Comments

Peter Zijlstra July 11, 2018, 8:34 a.m. UTC | #1
On Tue, Jul 10, 2018 at 03:26:20PM -0700, Yu-cheng Yu wrote:
> VM_SHSTK indicates a shadow stack memory area.
> 
> A shadow stack PTE must be read-only and dirty.  For non shadow
> stack, we use a spare bit of the 64-bit PTE for dirty.  The PTE
> changes are in the next patch.

This doesn't make any sense.. the $subject and the patch seem completely
unrelated to this Changelog.
Yu, Yu-cheng July 11, 2018, 4:15 p.m. UTC | #2
On Wed, 2018-07-11 at 10:34 +0200, Peter Zijlstra wrote:
> On Tue, Jul 10, 2018 at 03:26:20PM -0700, Yu-cheng Yu wrote:
> > 
> > VM_SHSTK indicates a shadow stack memory area.
> > 
> > A shadow stack PTE must be read-only and dirty.  For non shadow
> > stack, we use a spare bit of the 64-bit PTE for dirty.  The PTE
> > changes are in the next patch.
> This doesn't make any sense.. the $subject and the patch seem
> completely
> unrelated to this Changelog.

I was trying to say why this is only defined for 64-bit.  I will fix
it.

Yu-cheng
diff mbox

Patch

diff --git a/include/linux/mm.h b/include/linux/mm.h
index a0fbb9ffe380..d7b338b41593 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -222,11 +222,13 @@  extern unsigned int kobjsize(const void *objp);
 #define VM_HIGH_ARCH_BIT_2	34	/* bit only usable on 64-bit architectures */
 #define VM_HIGH_ARCH_BIT_3	35	/* bit only usable on 64-bit architectures */
 #define VM_HIGH_ARCH_BIT_4	36	/* bit only usable on 64-bit architectures */
+#define VM_HIGH_ARCH_BIT_5	37	/* bit only usable on 64-bit architectures */
 #define VM_HIGH_ARCH_0	BIT(VM_HIGH_ARCH_BIT_0)
 #define VM_HIGH_ARCH_1	BIT(VM_HIGH_ARCH_BIT_1)
 #define VM_HIGH_ARCH_2	BIT(VM_HIGH_ARCH_BIT_2)
 #define VM_HIGH_ARCH_3	BIT(VM_HIGH_ARCH_BIT_3)
 #define VM_HIGH_ARCH_4	BIT(VM_HIGH_ARCH_BIT_4)
+#define VM_HIGH_ARCH_5	BIT(VM_HIGH_ARCH_BIT_5)
 #endif /* CONFIG_ARCH_USES_HIGH_VMA_FLAGS */
 
 #ifdef CONFIG_ARCH_HAS_PKEYS
@@ -264,6 +266,12 @@  extern unsigned int kobjsize(const void *objp);
 # define VM_MPX		VM_NONE
 #endif
 
+#ifdef CONFIG_X86_INTEL_SHADOW_STACK_USER
+# define VM_SHSTK	VM_HIGH_ARCH_5
+#else
+# define VM_SHSTK	VM_NONE
+#endif
+
 #ifndef VM_GROWSUP
 # define VM_GROWSUP	VM_NONE
 #endif
diff --git a/mm/internal.h b/mm/internal.h
index 9e3654d70289..b09c29762d85 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -280,6 +280,14 @@  static inline bool is_data_mapping(vm_flags_t flags)
 	return (flags & (VM_WRITE | VM_SHARED | VM_STACK)) == VM_WRITE;
 }
 
+/*
+ * Shadow stack area
+ */
+static inline bool is_shstk_mapping(vm_flags_t flags)
+{
+	return (flags & VM_SHSTK);
+}
+
 /* mm/util.c */
 void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
 		struct vm_area_struct *prev, struct rb_node *rb_parent);