From: Hans-Joachim Picht <hpicht@redhat.com>
Date: Fri, 16 Nov 2007 13:59:20 +0100
Subject: [s390] pte type cleanup
Message-id: 20071116125920.GV6053@redhat.com
O-Subject: [RHEL5 U2 PATCH 14/14] s390 - pte type cleanup for rhel5
Bugzilla: 360701

Description
============

When running RHEL 5.1  under System z, without swap, after starting the
installation of a program that uses Java to install, the console
shows: swap_dup: Bad swap file entry <XXXXXXXX> , where X is an hex. address.

handle_pte_fault uses pte_present, pte_none and pte_file to find out the pte
type WITHOUT holding the page table lock. ptep_establish on the other hand
uses ptep_clear_flush to invalidate a given pte. ipte sets the hw invalid bit
and clears all tlbs for the page. The page table entry is set to
PAGE_TYPE_EMPTY
afterwards. This change is done while holding the lock, but the intermediate
step of a previously valid pte with the hw invalid bit set can be observed by
handle_pte_fault and the pte can be mistaken for a swap pte.

This mistake will be recognized in do_swap_page by a check on pte_same after
acquiring the pte lock, so there will be no damaging effect. However, in the
case where no swap is configured there will be the "Bad swap file entry" error
message.

This patch is a backport from an upstream cleanup of the pte types, eliminating
this pte type ambiguity.

Bugzilla
=========

BZ 360701
https://bugzilla.redhat.com/show_bug.cgi?id=360701

Upstream status of the patch:
=============================

This patch is a combination of two upstream patches, which depend on each
other:

[S390] Cleanup in page table related code.
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=9282ed929758b82f448a40d3c17319d794970624

[S390] Fix pte type checking.
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=833774849d50a59f58e9bdfc3d9c88e682b3596d

Test status:
============
Kernel with patch was built and successfully tested

Please ACK.

With best regards,

Hans

diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
index e71c5ee..02f90f8 100644
--- a/arch/s390/mm/init.c
+++ b/arch/s390/mm/init.c
@@ -108,16 +108,23 @@ void __init paging_init(void)
         unsigned long pgdir_k = (__pa(swapper_pg_dir) & PAGE_MASK) | _KERNSEG_TABLE;
         static const int ssm_mask = 0x04000000L;
 	unsigned long ro_start_pfn, ro_end_pfn;
+	unsigned long zones_size[MAX_NR_ZONES];
 
 	ro_start_pfn = PFN_DOWN((unsigned long)&__start_rodata);
 	ro_end_pfn = PFN_UP((unsigned long)&__end_rodata);
 
+	memset(zones_size, 0, sizeof(zones_size));
+	zones_size[ZONE_DMA] = max_low_pfn;
+	free_area_init_node(0, &contig_page_data, zones_size,
+			    __pa(PAGE_OFFSET) >> PAGE_SHIFT,
+			    zholes_size);
+
 	/* unmap whole virtual address space */
 	
         pg_dir = swapper_pg_dir;
 
-	for (i=0;i<KERNEL_PGD_PTRS;i++) 
-	        pmd_clear((pmd_t*)pg_dir++);
+	for (i = 0; i < PTRS_PER_PGD; i++)
+		pmd_clear((pmd_t *) pg_dir++);
 		
 	/*
 	 * map whole physical memory to virtual memory (identity mapping) 
@@ -131,10 +138,7 @@ void __init paging_init(void)
                  */
 		pg_table = (pte_t *) alloc_bootmem_pages(PAGE_SIZE);
 
-                pg_dir->pgd0 =  (_PAGE_TABLE | __pa(pg_table));
-                pg_dir->pgd1 =  (_PAGE_TABLE | (__pa(pg_table)+1024));
-                pg_dir->pgd2 =  (_PAGE_TABLE | (__pa(pg_table)+2048));
-                pg_dir->pgd3 =  (_PAGE_TABLE | (__pa(pg_table)+3072));
+		pmd_populate_kernel(&init_mm, (pmd_t *) pg_dir, pg_table);
                 pg_dir++;
 
                 for (tmp = 0 ; tmp < PTRS_PER_PTE ; tmp++,pg_table++) {
@@ -143,8 +147,8 @@ void __init paging_init(void)
 			else
 				pte = pfn_pte(pfn, PAGE_KERNEL);
                         if (pfn >= max_low_pfn)
-                                pte_clear(&init_mm, 0, &pte);
-                        set_pte(pg_table, pte);
+				pte_val(pte) = _PAGE_TYPE_EMPTY;
+			set_pte(pg_table, pte);
                         pfn++;
                 }
         }
@@ -159,16 +163,6 @@ void __init paging_init(void)
 			     : : "m" (pgdir_k), "m" (ssm_mask));
 
         local_flush_tlb();
-
-	{
-		unsigned long zones_size[MAX_NR_ZONES];
-
-		memset(zones_size, 0, sizeof(zones_size));
-		zones_size[ZONE_DMA] = max_low_pfn;
-		free_area_init_node(0, &contig_page_data, zones_size,
-				    __pa(PAGE_OFFSET) >> PAGE_SHIFT,
-				    zholes_size);
-	}
         return;
 }
 
@@ -236,10 +230,8 @@ void __init paging_init(void)
 					pte = pfn_pte(pfn, __pgprot(_PAGE_RO));
 				else
 					pte = pfn_pte(pfn, PAGE_KERNEL);
-                                if (pfn >= max_low_pfn) {
-                                        pte_clear(&init_mm, 0, &pte); 
-                                        continue;
-                                }
+				if (pfn >= max_low_pfn)
+					pte_val(pte) = _PAGE_TYPE_EMPTY;
                                 set_pte(pt_dir, pte);
                                 pfn++;
                         }
diff --git a/include/asm-s390/pgalloc.h b/include/asm-s390/pgalloc.h
index 808c15e..151c838 100644
--- a/include/asm-s390/pgalloc.h
+++ b/include/asm-s390/pgalloc.h
@@ -26,6 +26,16 @@
 extern void diag10(unsigned long addr);
 
 /*
+ * Page allocation orders.
+ */
+#ifndef __s390x__
+# define PGD_ALLOC_ORDER	1
+#else /* __s390x__ */
+# define PMD_ALLOC_ORDER	2
+# define PGD_ALLOC_ORDER	2
+#endif /* __s390x__ */
+
+/*
  * Allocate and free page tables. The xxx_kernel() versions are
  * used to allocate a kernel page table - this turns on ASN bits
  * if any.
@@ -33,30 +43,23 @@ extern void diag10(unsigned long addr);
 
 static inline pgd_t *pgd_alloc(struct mm_struct *mm)
 {
-	pgd_t *pgd;
+	pgd_t *pgd = (pgd_t *) __get_free_pages(GFP_KERNEL, PGD_ALLOC_ORDER);
 	int i;
 
+	if (!pgd)
+		return NULL;
+	for (i = 0; i < PTRS_PER_PGD; i++)
 #ifndef __s390x__
-	pgd = (pgd_t *) __get_free_pages(GFP_KERNEL,1);
-        if (pgd != NULL)
-		for (i = 0; i < USER_PTRS_PER_PGD; i++)
-			pmd_clear(pmd_offset(pgd + i, i*PGDIR_SIZE));
-#else /* __s390x__ */
-	pgd = (pgd_t *) __get_free_pages(GFP_KERNEL,2);
-        if (pgd != NULL)
-		for (i = 0; i < PTRS_PER_PGD; i++)
-			pgd_clear(pgd + i);
-#endif /* __s390x__ */
+		pmd_clear(pmd_offset(pgd + i, i*PGDIR_SIZE));
+#else
+		pgd_clear(pgd + i);
+#endif
 	return pgd;
 }
 
 static inline void pgd_free(pgd_t *pgd)
 {
-#ifndef __s390x__
-        free_pages((unsigned long) pgd, 1);
-#else /* __s390x__ */
-        free_pages((unsigned long) pgd, 2);
-#endif /* __s390x__ */
+	free_pages((unsigned long) pgd, PGD_ALLOC_ORDER);
 }
 
 #ifndef __s390x__
@@ -72,20 +75,19 @@ static inline void pgd_free(pgd_t *pgd)
 #else /* __s390x__ */
 static inline pmd_t * pmd_alloc_one(struct mm_struct *mm, unsigned long vmaddr)
 {
-	pmd_t *pmd;
-        int i;
+	pmd_t *pmd = (pmd_t *) __get_free_pages(GFP_KERNEL, PMD_ALLOC_ORDER);
+	int i;
 
-	pmd = (pmd_t *) __get_free_pages(GFP_KERNEL, 2);
-	if (pmd != NULL) {
-		for (i=0; i < PTRS_PER_PMD; i++)
-			pmd_clear(pmd+i);
-	}
+	if (!pmd)
+		return NULL;
+	for (i=0; i < PTRS_PER_PMD; i++)
+		pmd_clear(pmd + i);
 	return pmd;
 }
 
 static inline void pmd_free (pmd_t *pmd)
 {
-	free_pages((unsigned long) pmd, 2);
+	free_pages((unsigned long) pmd, PMD_ALLOC_ORDER);
 }
 
 #define __pmd_free_tlb(tlb,pmd)			\
@@ -127,15 +129,14 @@ pmd_populate(struct mm_struct *mm, pmd_t *pmd, struct page *page)
 static inline pte_t *
 pte_alloc_one_kernel(struct mm_struct *mm, unsigned long vmaddr)
 {
-	pte_t *pte;
-        int i;
-
-	pte = (pte_t *)__get_free_page(GFP_KERNEL|__GFP_REPEAT);
-	if (pte != NULL) {
-		for (i=0; i < PTRS_PER_PTE; i++) {
-			pte_clear(mm, vmaddr, pte+i);
-			vmaddr += PAGE_SIZE;
-		}
+	pte_t *pte = (pte_t *) __get_free_page(GFP_KERNEL|__GFP_REPEAT);
+	int i;
+
+	if (!pte)
+		return NULL;
+	for (i=0; i < PTRS_PER_PTE; i++) {
+		pte_clear(mm, vmaddr, pte + i);
+		vmaddr += PAGE_SIZE;
 	}
 	return pte;
 }
diff --git a/include/asm-s390/pgtable.h b/include/asm-s390/pgtable.h
index 2431238..8a4774f 100644
--- a/include/asm-s390/pgtable.h
+++ b/include/asm-s390/pgtable.h
@@ -89,19 +89,6 @@ extern char empty_zero_page[PAGE_SIZE];
 # define PTRS_PER_PGD    2048
 #endif /* __s390x__ */
 
-/*
- * pgd entries used up by user/kernel:
- */
-#ifndef __s390x__
-# define USER_PTRS_PER_PGD  512
-# define USER_PGD_PTRS      512
-# define KERNEL_PGD_PTRS    512
-#else /* __s390x__ */
-# define USER_PTRS_PER_PGD  2048
-# define USER_PGD_PTRS      2048
-# define KERNEL_PGD_PTRS    2048
-#endif /* __s390x__ */
-
 #define FIRST_USER_ADDRESS  0
 
 #define pte_ERROR(e) \
@@ -213,15 +200,44 @@ extern char empty_zero_page[PAGE_SIZE];
  */
 
 /* Hardware bits in the page table entry */
-#define _PAGE_RO        0x200          /* HW read-only                     */
-#define _PAGE_INVALID   0x400          /* HW invalid                       */
+#define _PAGE_RO	0x200		/* HW read-only bit  */
+#define _PAGE_INVALID	0x400		/* HW invalid bit    */
+#define _PAGE_SWT	0x001		/* SW pte type bit t */
+#define _PAGE_SWX	0x002		/* SW pte type bit x */
+
+/* Six different types of pages. */
+#define _PAGE_TYPE_EMPTY	0x400
+#define _PAGE_TYPE_NONE		0x401
+#define _PAGE_TYPE_SWAP		0x403
+#define _PAGE_TYPE_FILE		0x601	/* bit 0x002 is used for offset !! */
+#define _PAGE_TYPE_RO		0x200
+#define _PAGE_TYPE_RW		0x000
 
-/* Mask and four different kinds of invalid pages. */
-#define _PAGE_INVALID_MASK	0x601
-#define _PAGE_INVALID_EMPTY	0x400
-#define _PAGE_INVALID_NONE	0x401
-#define _PAGE_INVALID_SWAP	0x600
-#define _PAGE_INVALID_FILE	0x601
+/*
+ * PTE type bits are rather complicated. handle_pte_fault uses pte_present,
+ * pte_none and pte_file to find out the pte type WITHOUT holding the page
+ * table lock. ptep_clear_flush on the other hand uses ptep_clear_flush to
+ * invalidate a given pte. ipte sets the hw invalid bit and clears all tlbs
+ * for the page. The page table entry is set to _PAGE_TYPE_EMPTY afterwards.
+ * This change is done while holding the lock, but the intermediate step
+ * of a previously valid pte with the hw invalid bit set can be observed by
+ * handle_pte_fault. That makes it necessary that all valid pte types with
+ * the hw invalid bit set must be distinguishable from the four pte types
+ * empty, none, swap and file.
+ *
+ *			irxt  ipte  irxt
+ * _PAGE_TYPE_EMPTY	1000   ->   1000
+ * _PAGE_TYPE_NONE	1001   ->   1001
+ * _PAGE_TYPE_SWAP	1011   ->   1011
+ * _PAGE_TYPE_FILE	11?1   ->   11?1
+ * _PAGE_TYPE_RO	0100   ->   1100
+ * _PAGE_TYPE_RW	0000   ->   1000
+ *
+ * pte_none is true for bits combinations 1000, 1100
+ * pte_present is true for bits combinations 0000, 0010, 0100, 0110, 1001
+ * pte_file is true for bits combinations 1101, 1111
+ * swap pte is 1011 and 0001, 0011, 0101, 0111, 1010 and 1110 are invalid.
+ */
 
 #ifndef __s390x__
 
@@ -280,15 +296,14 @@ extern char empty_zero_page[PAGE_SIZE];
 #endif /* __s390x__ */
 
 /*
- * No mapping available
+ * Page protection definitions.
  */
-#define PAGE_NONE_SHARED  __pgprot(_PAGE_INVALID_NONE)
-#define PAGE_NONE_PRIVATE __pgprot(_PAGE_INVALID_NONE)
-#define PAGE_RO_SHARED	  __pgprot(_PAGE_RO)
-#define PAGE_RO_PRIVATE	  __pgprot(_PAGE_RO)
-#define PAGE_COPY	  __pgprot(_PAGE_RO)
-#define PAGE_SHARED	  __pgprot(0)
-#define PAGE_KERNEL	  __pgprot(0)
+#define PAGE_NONE	__pgprot(_PAGE_TYPE_NONE)
+#define PAGE_RO		__pgprot(_PAGE_TYPE_RO)
+#define PAGE_RW		__pgprot(_PAGE_TYPE_RW)
+
+#define PAGE_KERNEL	PAGE_RW
+#define PAGE_COPY	PAGE_RO
 
 /*
  * The S390 can't do page protection for execute, and considers that the
@@ -296,23 +311,23 @@ extern char empty_zero_page[PAGE_SIZE];
  * the closest we can get..
  */
          /*xwr*/
-#define __P000  PAGE_NONE_PRIVATE
-#define __P001  PAGE_RO_PRIVATE
-#define __P010  PAGE_COPY
-#define __P011  PAGE_COPY
-#define __P100  PAGE_RO_PRIVATE
-#define __P101  PAGE_RO_PRIVATE
-#define __P110  PAGE_COPY
-#define __P111  PAGE_COPY
-
-#define __S000  PAGE_NONE_SHARED
-#define __S001  PAGE_RO_SHARED
-#define __S010  PAGE_SHARED
-#define __S011  PAGE_SHARED
-#define __S100  PAGE_RO_SHARED
-#define __S101  PAGE_RO_SHARED
-#define __S110  PAGE_SHARED
-#define __S111  PAGE_SHARED
+#define __P000	PAGE_NONE
+#define __P001	PAGE_RO
+#define __P010	PAGE_RO
+#define __P011	PAGE_RO
+#define __P100	PAGE_RO
+#define __P101	PAGE_RO
+#define __P110	PAGE_RO
+#define __P111	PAGE_RO
+
+#define __S000	PAGE_NONE
+#define __S001	PAGE_RO
+#define __S010	PAGE_RW
+#define __S011	PAGE_RW
+#define __S100	PAGE_RO
+#define __S101	PAGE_RO
+#define __S110	PAGE_RW
+#define __S111	PAGE_RW
 
 /*
  * Certain architectures need to do special things when PTEs
@@ -377,18 +392,21 @@ static inline int pmd_bad(pmd_t pmd)
 
 static inline int pte_none(pte_t pte)
 {
-	return (pte_val(pte) & _PAGE_INVALID_MASK) == _PAGE_INVALID_EMPTY;
+	return (pte_val(pte) & _PAGE_INVALID) && !(pte_val(pte) & _PAGE_SWT);
 }
 
 static inline int pte_present(pte_t pte)
 {
-	return !(pte_val(pte) & _PAGE_INVALID) ||
-		(pte_val(pte) & _PAGE_INVALID_MASK) == _PAGE_INVALID_NONE;
+	unsigned long mask = _PAGE_RO | _PAGE_INVALID | _PAGE_SWT | _PAGE_SWX;
+	return (pte_val(pte) & mask) == _PAGE_TYPE_NONE ||
+		(!(pte_val(pte) & _PAGE_INVALID) &&
+		 !(pte_val(pte) & _PAGE_SWT));
 }
 
 static inline int pte_file(pte_t pte)
 {
-	return (pte_val(pte) & _PAGE_INVALID_MASK) == _PAGE_INVALID_FILE;
+	unsigned long mask = _PAGE_RO | _PAGE_INVALID | _PAGE_SWT;
+	return (pte_val(pte) & mask) == _PAGE_TYPE_FILE;
 }
 
 #define pte_same(a,b)	(pte_val(a) == pte_val(b))
@@ -461,7 +479,7 @@ static inline void pmd_clear(pmd_t * pmdp)
 
 static inline void pte_clear(struct mm_struct *mm, unsigned long addr, pte_t *ptep)
 {
-	pte_val(*ptep) = _PAGE_INVALID_EMPTY;
+	pte_val(*ptep) = _PAGE_TYPE_EMPTY;
 }
 
 /*
@@ -477,7 +495,7 @@ static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
 
 static inline pte_t pte_wrprotect(pte_t pte)
 {
-	/* Do not clobber _PAGE_INVALID_NONE pages!  */
+	/* Do not clobber _PAGE_TYPE_NONE pages!  */
 	if (!(pte_val(pte) & _PAGE_INVALID))
 		pte_val(pte) |= _PAGE_RO;
 	return pte;
@@ -556,26 +574,30 @@ static inline pte_t ptep_get_and_clear(struct mm_struct *mm, unsigned long addr,
 	return pte;
 }
 
-static inline pte_t
-ptep_clear_flush(struct vm_area_struct *vma,
-		 unsigned long address, pte_t *ptep)
+static inline void __ptep_ipte(unsigned long address, pte_t *ptep)
 {
-	pte_t pte = *ptep;
+	if (!(pte_val(*ptep) & _PAGE_INVALID)) {
 #ifndef __s390x__
-	if (!(pte_val(pte) & _PAGE_INVALID)) {
 		/* S390 has 1mb segments, we are emulating 4MB segments */
 		pte_t *pto = (pte_t *) (((unsigned long) ptep) & 0x7ffffc00);
-		__asm__ __volatile__ ("ipte %2,%3"
-				      : "=m" (*ptep) : "m" (*ptep),
-				        "a" (pto), "a" (address) );
+#else
+		/* ipte in zarch mode can do the math */
+		pte_t *pto = ptep;
+#endif
+		asm volatile ("ipte %2,%3"
+			      : "=m" (*ptep) : "m" (*ptep),
+				"a" (pto), "a" (address) );
 	}
-#else /* __s390x__ */
-	if (!(pte_val(pte) & _PAGE_INVALID)) 
-		__asm__ __volatile__ ("ipte %2,%3"
-				      : "=m" (*ptep) : "m" (*ptep),
-				        "a" (ptep), "a" (address) );
-#endif /* __s390x__ */
-	pte_val(*ptep) = _PAGE_INVALID_EMPTY;
+	pte_val(*ptep) = _PAGE_TYPE_EMPTY;
+}
+
+static inline pte_t
+ptep_clear_flush(struct vm_area_struct *vma,
+		 unsigned long address, pte_t *ptep)
+{
+	pte_t pte = *ptep;
+
+	__ptep_ipte(address, ptep);
 	return pte;
 }
 
@@ -755,7 +777,7 @@ static inline pte_t mk_swap_pte(unsigned long type, unsigned long offset)
 {
 	pte_t pte;
 	offset &= __SWP_OFFSET_MASK;
-	pte_val(pte) = _PAGE_INVALID_SWAP | ((type & 0x1f) << 2) |
+	pte_val(pte) = _PAGE_TYPE_SWAP | ((type & 0x1f) << 2) |
 		((offset & 1UL) << 7) | ((offset & ~1UL) << 11);
 	return pte;
 }
@@ -778,7 +800,7 @@ static inline pte_t mk_swap_pte(unsigned long type, unsigned long offset)
 
 #define pgoff_to_pte(__off) \
 	((pte_t) { ((((__off) & 0x7f) << 1) + (((__off) >> 7) << 12)) \
-		   | _PAGE_INVALID_FILE })
+		   | _PAGE_TYPE_FILE })
 
 #endif /* !__ASSEMBLY__ */