[PATCH 3/3] powerpc: mm: support page table check

[Rohan McLure <rmclure@linux.ibm.com>]

On creation and clearing of a page table mapping, instrument such calls
by invoking page_table_check_pte_set and page_table_check_pte_clear
respectively. These calls serve as a sanity check against illegal
mappings.

Enable ARCH_SUPPORTS_PAGE_TABLE_CHECK for all ppc64, and 32-bit
platforms implementing Book3S.

Change pud_pfn to be a runtime bug rather than a build bug as it is
consumed by page_table_check_pud_{clear,set} which are not called.

See also:

riscv support in commit 3fee229a8eb9 ("riscv/mm: enable ARCH_SUPPORTS_PAGE_TABLE_CHECK")
arm64 in commit 42b2547137f5 ("arm64/mm: enable ARCH_SUPPORTS_PAGE_TABLE_CHECK")
x86_64 in commit d283d422c6c4 ("x86: mm: add x86_64 support for page table
    check")

Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
---
 arch/powerpc/Kconfig                         | 1 +
 arch/powerpc/include/asm/book3s/32/pgtable.h | 7 ++++++-
 arch/powerpc/include/asm/book3s/64/pgtable.h | 9 ++++++++-
 arch/powerpc/include/asm/nohash/32/pgtable.h | 5 ++++-
 arch/powerpc/include/asm/nohash/64/pgtable.h | 2 ++
 arch/powerpc/include/asm/nohash/pgtable.h    | 1 +
 arch/powerpc/include/asm/pgtable.h           | 4 ++++
 7 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 4c466acdc70d..6c213ac46a92 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -149,6 +149,7 @@ config PPC
 	select ARCH_STACKWALK
 	select ARCH_SUPPORTS_ATOMIC_RMW
 	select ARCH_SUPPORTS_DEBUG_PAGEALLOC	if PPC_BOOK3S || PPC_8xx || 40x
+	select ARCH_SUPPORTS_PAGE_TABLE_CHECK
 	select ARCH_USE_BUILTIN_BSWAP
 	select ARCH_USE_CMPXCHG_LOCKREF		if PPC64
 	select ARCH_USE_MEMTEST
diff --git a/arch/powerpc/include/asm/book3s/32/pgtable.h b/arch/powerpc/include/asm/book3s/32/pgtable.h
index 40041ac713d9..3d05c8fe4604 100644
--- a/arch/powerpc/include/asm/book3s/32/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/32/pgtable.h
@@ -53,6 +53,8 @@
 
 #ifndef __ASSEMBLY__
 
+#include <linux/page_table_check.h>
+
 static inline bool pte_user(pte_t pte)
 {
 	return pte_val(pte) & _PAGE_USER;
@@ -353,7 +355,9 @@ static inline int __ptep_test_and_clear_young(struct mm_struct *mm,
 static inline pte_t ptep_get_and_clear(struct mm_struct *mm, unsigned long addr,
 				       pte_t *ptep)
 {
-	return __pte(pte_update(mm, addr, ptep, ~_PAGE_HASHPTE, 0, 0));
+	unsigned long old = pte_update(mm, addr, ptep, ~_PAGE_HASHPTE, 0, 0);
+	page_table_check_pte_clear(mm, addr, __pte(old));
+	return __pte(old);
 }
 
 #define __HAVE_ARCH_PTEP_SET_WRPROTECT
@@ -541,6 +545,7 @@ static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
 static inline void __set_pte_at(struct mm_struct *mm, unsigned long addr,
 				pte_t *ptep, pte_t pte, int percpu)
 {
+	page_table_check_pte_set(mm, addr, ptep, pte);
 #if defined(CONFIG_SMP) && !defined(CONFIG_PTE_64BIT)
 	/* First case is 32-bit Hash MMU in SMP mode with 32-bit PTEs. We use the
 	 * helper pte_update() which does an atomic update. We need to do that
diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index 8874f2a3661d..cbb7bd99c897 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -179,6 +179,8 @@
 #define PAGE_AGP		(PAGE_KERNEL_NC)
 
 #ifndef __ASSEMBLY__
+#include <linux/page_table_check.h>
+
 /*
  * page table defines
  */
@@ -483,6 +485,7 @@ static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
 				       unsigned long addr, pte_t *ptep)
 {
 	unsigned long old = pte_update(mm, addr, ptep, ~0UL, 0, 0);
+	page_table_check_pte_clear(mm, addr, __pte(old));
 	return __pte(old);
 }
 
@@ -491,12 +494,15 @@ static inline pte_t ptep_get_and_clear_full(struct mm_struct *mm,
 					    unsigned long addr,
 					    pte_t *ptep, int full)
 {
+	pte_t old_pte;
 	if (full && radix_enabled()) {
 		/*
 		 * We know that this is a full mm pte clear and
 		 * hence can be sure there is no parallel set_pte.
 		 */
-		return radix__ptep_get_and_clear_full(mm, addr, ptep, full);
+		old_pte = radix__ptep_get_and_clear_full(mm, addr, ptep, full);
+		page_table_check_pte_clear(mm, addr, old_pte);
+		return old_pte;
 	}
 	return ptep_get_and_clear(mm, addr, ptep);
 }
@@ -872,6 +878,7 @@ static inline void __set_pte_at(struct mm_struct *mm, unsigned long addr,
 	 */
 	pte = __pte_raw(pte_raw(pte) | cpu_to_be64(_PAGE_PTE));
 
+	page_table_check_pte_set(mm, addr, ptep, pte);
 	if (radix_enabled())
 		return radix__set_pte_at(mm, addr, ptep, pte, percpu);
 	return hash__set_pte_at(mm, addr, ptep, pte, percpu);
diff --git a/arch/powerpc/include/asm/nohash/32/pgtable.h b/arch/powerpc/include/asm/nohash/32/pgtable.h
index 9091e4904a6b..a3416cfb75d7 100644
--- a/arch/powerpc/include/asm/nohash/32/pgtable.h
+++ b/arch/powerpc/include/asm/nohash/32/pgtable.h
@@ -166,6 +166,7 @@ void unmap_kernel_page(unsigned long va);
 #define _PAGE_CHG_MASK	(PTE_RPN_MASK | _PAGE_DIRTY | _PAGE_ACCESSED | _PAGE_SPECIAL)
 
 #ifndef __ASSEMBLY__
+#include <linux/page_table_check.h>
 
 #define pte_clear(mm, addr, ptep) \
 	do { pte_update(mm, addr, ptep, ~0, 0, 0); } while (0)
@@ -305,7 +306,9 @@ static inline int __ptep_test_and_clear_young(struct mm_struct *mm,
 static inline pte_t ptep_get_and_clear(struct mm_struct *mm, unsigned long addr,
 				       pte_t *ptep)
 {
-	return __pte(pte_update(mm, addr, ptep, ~0, 0, 0));
+	unsigned long old = pte_update(mm, addr, ptep, ~0, 0, 0);
+	page_table_check_pte_clear(mm, addr, __pte(old));
+	return __pte(old);
 }
 
 #define __HAVE_ARCH_PTEP_SET_WRPROTECT
diff --git a/arch/powerpc/include/asm/nohash/64/pgtable.h b/arch/powerpc/include/asm/nohash/64/pgtable.h
index 599921cc257e..5f2e10842a0d 100644
--- a/arch/powerpc/include/asm/nohash/64/pgtable.h
+++ b/arch/powerpc/include/asm/nohash/64/pgtable.h
@@ -83,6 +83,7 @@
 #define H_PAGE_4K_PFN 0
 
 #ifndef __ASSEMBLY__
+#include <linux/page_table_check.h>
 /* pte_clear moved to later in this file */
 
 static inline pte_t pte_mkwrite(pte_t pte)
@@ -244,6 +245,7 @@ static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
 				       unsigned long addr, pte_t *ptep)
 {
 	unsigned long old = pte_update(mm, addr, ptep, ~0UL, 0, 0);
+	page_table_check_pte_clear(mm, addr, __pte(old));
 	return __pte(old);
 }
 
diff --git a/arch/powerpc/include/asm/nohash/pgtable.h b/arch/powerpc/include/asm/nohash/pgtable.h
index b499da6c1a99..62b221b7cccf 100644
--- a/arch/powerpc/include/asm/nohash/pgtable.h
+++ b/arch/powerpc/include/asm/nohash/pgtable.h
@@ -185,6 +185,7 @@ extern void set_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep,
 static inline void __set_pte_at(struct mm_struct *mm, unsigned long addr,
 				pte_t *ptep, pte_t pte, int percpu)
 {
+	page_table_check_pte_set(mm, addr, ptep, pte);
 	/* Second case is 32-bit with 64-bit PTE.  In this case, we
 	 * can just store as long as we do the two halves in the right order
 	 * with a barrier in between.
diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
index 8c1f5feb9360..5e1032d12499 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h
@@ -166,7 +166,11 @@ static inline int pud_pfn(pud_t pud)
 	 * check so this should never be used. If it grows another user we
 	 * want to know about it.
 	 */
+#ifndef CONFIG_PAGE_TABLE_CHECK
 	BUILD_BUG();
+#else
+	BUG();
+#endif
 	return 0;
 }
 
-- 
2.34.1