arm64: Distinguish between user and kernel XN bits

On AArch64, the meaning of the XN bit has changed to UXN (user). The PXN
(privileged) bit must be set to prevent kernel execution. Without the
PXN bit set, the CPU may speculatively access device memory. This patch
ensures that all the mappings that the kernel must not execute from
(including user mappings) have the PXN bit set.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

3 files changed, 25 insertions, 23 deletions

diff --git a/arch/arm64/include/asm/io.h b/arch/arm64/include/asm/io.h
index 54f6116697f7..d2f05a608274 100644
--- a/arch/arm64/include/asm/io.h
+++ b/arch/arm64/include/asm/io.h
@@ -222,7 +222,7 @@ extern void __iomem *__ioremap(phys_addr_t phys_addr, size_t size, pgprot_t prot
 extern void __iounmap(volatile void __iomem *addr);
 
 #define PROT_DEFAULT            (PTE_TYPE_PAGE | PTE_AF | PTE_DIRTY)
-#define PROT_DEVICE_nGnRE       (PROT_DEFAULT | PTE_XN | PTE_ATTRINDX(MT_DEVICE_nGnRE))
+#define PROT_DEVICE_nGnRE       (PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_ATTRINDX(MT_DEVICE_nGnRE))
 #define PROT_NORMAL_NC          (PROT_DEFAULT | PTE_ATTRINDX(MT_NORMAL_NC))
 
 #define ioremap(addr, size)             __ioremap((addr), (size), __pgprot(PROT_DEVICE_nGnRE))
diff --git a/arch/arm64/include/asm/pgtable-hwdef.h b/arch/arm64/include/asm/pgtable-hwdef.h
index 0f3b4581d925..75fd13d289b9 100644
--- a/arch/arm64/include/asm/pgtable-hwdef.h
+++ b/arch/arm64/include/asm/pgtable-hwdef.h
@@ -38,7 +38,8 @@
 #define PMD_SECT_S              (_AT(pmdval_t, 3) << 8)
 #define PMD_SECT_AF             (_AT(pmdval_t, 1) << 10)
 #define PMD_SECT_NG             (_AT(pmdval_t, 1) << 11)
-#define PMD_SECT_XN             (_AT(pmdval_t, 1) << 54)
+#define PMD_SECT_PXN            (_AT(pmdval_t, 1) << 53)
+#define PMD_SECT_UXN            (_AT(pmdval_t, 1) << 54)
 
 /*
  * AttrIndx[2:0] encoding (mapping attributes defined in the MAIR* registers).
@@ -57,7 +58,8 @@
 #define PTE_SHARED              (_AT(pteval_t, 3) << 8)         /* SH[1:0], inner shareable */
 #define PTE_AF                  (_AT(pteval_t, 1) << 10)        /* Access Flag */
 #define PTE_NG                  (_AT(pteval_t, 1) << 11)        /* nG */
-#define PTE_XN                  (_AT(pteval_t, 1) << 54)        /* XN */
+#define PTE_PXN                 (_AT(pteval_t, 1) << 53)        /* Privileged XN */
+#define PTE_UXN                 (_AT(pteval_t, 1) << 54)        /* User XN */
 
 /*
  * AttrIndx[2:0] encoding (mapping attributes defined in the MAIR* registers).
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 8960239be722..14aba2db6776 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -62,23 +62,23 @@ extern pgprot_t pgprot_default;
 
 #define _MOD_PROT(p, b) __pgprot(pgprot_val(p) | (b))
 
-#define PAGE_NONE               _MOD_PROT(pgprot_default, PTE_NG | PTE_XN | PTE_RDONLY)
-#define PAGE_SHARED             _MOD_PROT(pgprot_default, PTE_USER | PTE_NG | PTE_XN)
-#define PAGE_SHARED_EXEC        _MOD_PROT(pgprot_default, PTE_USER | PTE_NG)
-#define PAGE_COPY               _MOD_PROT(pgprot_default, PTE_USER | PTE_NG | PTE_XN | PTE_RDONLY)
-#define PAGE_COPY_EXEC          _MOD_PROT(pgprot_default, PTE_USER | PTE_NG | PTE_RDONLY)
-#define PAGE_READONLY           _MOD_PROT(pgprot_default, PTE_USER | PTE_NG | PTE_XN | PTE_RDONLY)
-#define PAGE_READONLY_EXEC      _MOD_PROT(pgprot_default, PTE_USER | PTE_NG | PTE_RDONLY)
-#define PAGE_KERNEL             _MOD_PROT(pgprot_default, PTE_XN | PTE_DIRTY)
-#define PAGE_KERNEL_EXEC        _MOD_PROT(pgprot_default, PTE_DIRTY)
-
-#define __PAGE_NONE             __pgprot(_PAGE_DEFAULT | PTE_NG | PTE_XN | PTE_RDONLY)
-#define __PAGE_SHARED           __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_XN)
-#define __PAGE_SHARED_EXEC      __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG)
-#define __PAGE_COPY             __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_XN | PTE_RDONLY)
-#define __PAGE_COPY_EXEC        __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_RDONLY)
-#define __PAGE_READONLY         __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_XN | PTE_RDONLY)
-#define __PAGE_READONLY_EXEC    __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_RDONLY)
+#define PAGE_NONE               _MOD_PROT(pgprot_default, PTE_NG | PTE_PXN | PTE_UXN | PTE_RDONLY)
+#define PAGE_SHARED             _MOD_PROT(pgprot_default, PTE_USER | PTE_NG | PTE_PXN | PTE_UXN)
+#define PAGE_SHARED_EXEC        _MOD_PROT(pgprot_default, PTE_USER | PTE_NG | PTE_PXN)
+#define PAGE_COPY               _MOD_PROT(pgprot_default, PTE_USER | PTE_NG | PTE_PXN | PTE_UXN | PTE_RDONLY)
+#define PAGE_COPY_EXEC          _MOD_PROT(pgprot_default, PTE_USER | PTE_NG | PTE_PXN | PTE_RDONLY)
+#define PAGE_READONLY           _MOD_PROT(pgprot_default, PTE_USER | PTE_NG | PTE_PXN | PTE_UXN | PTE_RDONLY)
+#define PAGE_READONLY_EXEC      _MOD_PROT(pgprot_default, PTE_USER | PTE_NG | PTE_PXN | PTE_RDONLY)
+#define PAGE_KERNEL             _MOD_PROT(pgprot_default, PTE_PXN | PTE_UXN | PTE_DIRTY)
+#define PAGE_KERNEL_EXEC        _MOD_PROT(pgprot_default, PTE_UXN | PTE_DIRTY)
+
+#define __PAGE_NONE             __pgprot(_PAGE_DEFAULT | PTE_NG | PTE_PXN | PTE_UXN | PTE_RDONLY)
+#define __PAGE_SHARED           __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN | PTE_UXN)
+#define __PAGE_SHARED_EXEC      __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN)
+#define __PAGE_COPY             __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN | PTE_UXN | PTE_RDONLY)
+#define __PAGE_COPY_EXEC        __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN | PTE_RDONLY)
+#define __PAGE_READONLY         __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN | PTE_UXN | PTE_RDONLY)
+#define __PAGE_READONLY_EXEC    __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN | PTE_RDONLY)
 
 #endif /* __ASSEMBLY__ */
 
@@ -130,10 +130,10 @@ extern struct page *empty_zero_page;
 #define pte_young(pte)          (pte_val(pte) & PTE_AF)
 #define pte_special(pte)        (pte_val(pte) & PTE_SPECIAL)
 #define pte_write(pte)          (!(pte_val(pte) & PTE_RDONLY))
-#define pte_exec(pte)           (!(pte_val(pte) & PTE_XN))
+#define pte_exec(pte)           (!(pte_val(pte) & PTE_UXN))
 
 #define pte_present_exec_user(pte) \
-        ((pte_val(pte) & (PTE_VALID | PTE_USER | PTE_XN)) == \
+        ((pte_val(pte) & (PTE_VALID | PTE_USER | PTE_UXN)) == \
          (PTE_VALID | PTE_USER))
 
 #define PTE_BIT_FUNC(fn,op) \
@@ -262,7 +262,7 @@ static inline pmd_t *pmd_offset(pud_t *pud, unsigned long addr)
 
 static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
 {
-        const pteval_t mask = PTE_USER | PTE_XN | PTE_RDONLY;
+        const pteval_t mask = PTE_USER | PTE_PXN | PTE_UXN | PTE_RDONLY;
         pte_val(pte) = (pte_val(pte) & ~mask) | (pgprot_val(newprot) & mask);
         return pte;
 }