[PATCH v14 14/26] x86/mm: Update maybe_mkwrite() for shadow stack

[Yu-cheng Yu]

Shadow stack memory is writable, but its VMA has VM_SHSTK instead of
VM_WRITE.  Update maybe_mkwrite() to include the shadow stack.

Signed-off-by: Yu-cheng Yu <yu-cheng...@intel.com>
---
 arch/x86/Kconfig        |  4 ++++
 arch/x86/mm/pgtable.c   | 18 ++++++++++++++++++
 include/linux/mm.h      |  2 ++
 include/linux/pgtable.h | 24 ++++++++++++++++++++++++
 mm/huge_memory.c        |  2 ++
 5 files changed, 50 insertions(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 415fcc869afc..7578327226e3 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1935,6 +1935,9 @@ config AS_HAS_SHADOW_STACK
 config X86_CET
        def_bool n
 
+config ARCH_MAYBE_MKWRITE
+       def_bool n
+
 config ARCH_HAS_SHADOW_STACK
        def_bool n
 
@@ -1945,6 +1948,7 @@ config X86_SHADOW_STACK_USER
        depends on AS_HAS_SHADOW_STACK
        select ARCH_USES_HIGH_VMA_FLAGS
        select X86_CET
+       select ARCH_MAYBE_MKWRITE
        select ARCH_HAS_SHADOW_STACK
        help
          Shadow Stacks provides protection against program stack
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index dfd82f51ba66..a9666b64bc05 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -610,6 +610,24 @@ int pmdp_clear_flush_young(struct vm_area_struct *vma,
 }
 #endif
 
+#ifdef CONFIG_ARCH_MAYBE_MKWRITE
+pte_t arch_maybe_mkwrite(pte_t pte, struct vm_area_struct *vma)
+{
+       if (likely(vma->vm_flags & VM_SHSTK))
+               pte = pte_mkwrite_shstk(pte);
+       return pte;
+}
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+pmd_t arch_maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
+{
+       if (likely(vma->vm_flags & VM_SHSTK))
+               pmd = pmd_mkwrite_shstk(pmd);
+       return pmd;
+}
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+#endif /* CONFIG_ARCH_MAYBE_MKWRITE */
+
 /**
  * reserve_top_address - reserves a hole in the top of kernel address space
  * @reserve - size of hole to reserve
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 12be96b061c7..4f6305106feb 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -969,6 +969,8 @@ static inline pte_t maybe_mkwrite(pte_t pte, struct 
vm_area_struct *vma)
 {
        if (likely(vma->vm_flags & VM_WRITE))
                pte = pte_mkwrite(pte);
+       else
+               pte = arch_maybe_mkwrite(pte, vma);
        return pte;
 }
 
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 90654cb63e9e..157f5e726896 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -1356,6 +1356,30 @@ static inline bool arch_has_pfn_modify_check(void)
 }
 #endif /* !_HAVE_ARCH_PFN_MODIFY_ALLOWED */
 
+#ifdef CONFIG_MMU
+#ifdef CONFIG_ARCH_MAYBE_MKWRITE
+pte_t arch_maybe_mkwrite(pte_t pte, struct vm_area_struct *vma);
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+pmd_t arch_maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma);
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+
+#else /* !CONFIG_ARCH_MAYBE_MKWRITE */
+static inline pte_t arch_maybe_mkwrite(pte_t pte, struct vm_area_struct *vma)
+{
+       return pte;
+}
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+static inline pmd_t arch_maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct 
*vma)
+{
+       return pmd;
+}
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+
+#endif /* CONFIG_ARCH_MAYBE_MKWRITE */
+#endif /* CONFIG_MMU */
+
 /*
  * Architecture PAGE_KERNEL_* fallbacks
  *
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index da397779a6d4..01252b00cd06 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -464,6 +464,8 @@ pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct 
*vma)
 {
        if (likely(vma->vm_flags & VM_WRITE))
                pmd = pmd_mkwrite(pmd);
+       else
+               pmd = arch_maybe_pmd_mkwrite(pmd, vma);
        return pmd;
 }
 
-- 
2.21.0