[XTENSA] Add support for executable/non-executable feature in the mmu

Newer processor versions starting with Xtensa6/LX2 support an 'executable'
bit for memory pages. This bit replaces the 'valid' bit, so it must be
always set to one for older processor versions. To mark a page invalid, we now
set the cache-attributes to b11, which is backward compatible.

Signed-off-by: Chris Zankel <chris@zankel.net>

1 files changed, 101 insertions, 112 deletions

diff --git a/include/asm-xtensa/pgtable.h b/include/asm-xtensa/pgtable.h
index 06850f3b26a7..667a6c46b5a1 100644
--- a/include/asm-xtensa/pgtable.h
+++ b/include/asm-xtensa/pgtable.h
@@ -2,10 +2,10 @@
  * linux/include/asm-xtensa/pgtable.h
  *
  * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version2 as
+ * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  *
- * Copyright (C) 2001 - 2005 Tensilica Inc.
+ * Copyright (C) 2001 - 2007 Tensilica Inc.
  */
 
 #ifndef _XTENSA_PGTABLE_H
@@ -23,7 +23,7 @@
 
 /*
  * The Xtensa architecture port of Linux has a two-level page table system,
- * i.e. the logical three-level Linux page table layout are folded.
+ * i.e. the logical three-level Linux page table layout is folded.
  * Each task has the following memory page tables:
  *
  *   PGD table (page directory), ie. 3rd-level page table:
@@ -43,6 +43,7 @@
  *
  * The individual pages are 4 kB big with special pages for the empty_zero_page.
  */
+
 #define PGDIR_SHIFT     22
 #define PGDIR_SIZE      (1UL << PGDIR_SHIFT)
 #define PGDIR_MASK      (~(PGDIR_SIZE-1))
@@ -53,12 +54,10 @@
  */
 #define PTRS_PER_PTE            1024
 #define PTRS_PER_PTE_SHIFT      10
-#define PTRS_PER_PMD            1
 #define PTRS_PER_PGD            1024
 #define PGD_ORDER               0
-#define PMD_ORDER               0
 #define USER_PTRS_PER_PGD       (TASK_SIZE/PGDIR_SIZE)
-#define FIRST_USER_ADDRESS      0
+#define FIRST_USER_ADDRESS      0
 #define FIRST_USER_PGD_NR       (FIRST_USER_ADDRESS >> PGDIR_SHIFT)
 
 /* virtual memory area. We keep a distance to other memory regions to be
@@ -86,47 +85,54 @@
  * See further below for PTE layout for swapped-out pages.
  */
 
-#define _PAGE_VALID             (1<<0)  /* hardware: page is accessible */
-#define _PAGE_WRENABLE          (1<<1)  /* hardware: page is writable */
+#define _PAGE_HW_EXEC           (1<<0)  /* hardware: page is executable */
+#define _PAGE_HW_WRITE          (1<<1)  /* hardware: page is writable */
+
+#define _PAGE_FILE              (1<<1)  /* non-linear mapping, if !present */
+#define _PAGE_PROTNONE          (3<<0)  /* special case for VM_PROT_NONE */
 
 /* None of these cache modes include MP coherency:  */
-#define _PAGE_NO_CACHE          (0<<2)  /* bypass, non-speculative */
-#if XCHAL_DCACHE_IS_WRITEBACK
-# define _PAGE_WRITEBACK        (1<<2)  /* write back */
-# define _PAGE_WRITETHRU        (2<<2)  /* write through */
-#else
-# define _PAGE_WRITEBACK        (1<<2)  /* assume write through */
-# define _PAGE_WRITETHRU        (1<<2)
-#endif
-#define _PAGE_NOALLOC           (3<<2)  /* don't allocate cache,if not cached */
-#define _CACHE_MASK             (3<<2)
+#define _PAGE_CA_BYPASS         (0<<2)  /* bypass, non-speculative */
+#define _PAGE_CA_WB             (1<<2)  /* write-back */
+#define _PAGE_CA_WT             (2<<2)  /* write-through */
+#define _PAGE_CA_MASK           (3<<2)
+#define _PAGE_INVALID           (3<<2)
 
 #define _PAGE_USER              (1<<4)  /* user access (ring=1) */
-#define _PAGE_KERNEL            (0<<4)  /* kernel access (ring=0) */
 
 /* Software */
-#define _PAGE_RW                (1<<6)  /* software: page writable */
+#define _PAGE_WRITABLE_BIT      6
+#define _PAGE_WRITABLE          (1<<6)  /* software: page writable */
 #define _PAGE_DIRTY             (1<<7)  /* software: page dirty */
 #define _PAGE_ACCESSED          (1<<8)  /* software: page accessed (read) */
-#define _PAGE_FILE              (1<<9)  /* nonlinear file mapping*/
 
-#define _PAGE_CHG_MASK  (PAGE_MASK | _PAGE_ACCESSED | _CACHE_MASK | _PAGE_DIRTY)
-#define _PAGE_PRESENT   ( _PAGE_VALID | _PAGE_WRITEBACK | _PAGE_ACCESSED)
+/* On older HW revisions, we always have to set bit 0 */
+#if XCHAL_HW_VERSION_MAJOR < 2000
+# define _PAGE_VALID            (1<<0)
+#else
+# define _PAGE_VALID            0
+#endif
+
+#define _PAGE_CHG_MASK  (PAGE_MASK | _PAGE_ACCESSED | _PAGE_DIRTY)
+#define _PAGE_PRESENT   (_PAGE_VALID | _PAGE_CA_WB | _PAGE_ACCESSED)
 
 #ifdef CONFIG_MMU
 
-# define PAGE_NONE      __pgprot(_PAGE_PRESENT)
-# define PAGE_SHARED    __pgprot(_PAGE_PRESENT | _PAGE_USER | _PAGE_RW)
-# define PAGE_COPY      __pgprot(_PAGE_PRESENT | _PAGE_USER)
-# define PAGE_READONLY  __pgprot(_PAGE_PRESENT | _PAGE_USER)
-# define PAGE_KERNEL    __pgprot(_PAGE_PRESENT | _PAGE_KERNEL | _PAGE_WRENABLE)
-# define PAGE_INVALID   __pgprot(_PAGE_USER)
-
-# if (DCACHE_WAY_SIZE > PAGE_SIZE)
-#  define PAGE_DIRECTORY  __pgprot(_PAGE_VALID | _PAGE_ACCESSED | _PAGE_KERNEL)
-# else
-#  define PAGE_DIRECTORY  __pgprot(_PAGE_PRESENT | _PAGE_KERNEL)
-# endif
+#define PAGE_NONE          __pgprot(_PAGE_INVALID | _PAGE_USER | _PAGE_PROTNONE)
+#define PAGE_COPY          __pgprot(_PAGE_PRESENT | _PAGE_USER)
+#define PAGE_COPY_EXEC     __pgprot(_PAGE_PRESENT | _PAGE_USER | _PAGE_HW_EXEC)
+#define PAGE_READONLY      __pgprot(_PAGE_PRESENT | _PAGE_USER)
+#define PAGE_READONLY_EXEC __pgprot(_PAGE_PRESENT | _PAGE_USER | _PAGE_HW_EXEC)
+#define PAGE_SHARED        __pgprot(_PAGE_PRESENT | _PAGE_USER | _PAGE_WRITABLE)
+#define PAGE_SHARED_EXEC \
+        __pgprot(_PAGE_PRESENT | _PAGE_USER | _PAGE_WRITABLE | _PAGE_HW_EXEC)
+#define PAGE_KERNEL        __pgprot(_PAGE_PRESENT)
+
+#if (DCACHE_WAY_SIZE > PAGE_SIZE)
+# define _PAGE_DIRECTORY (_PAGE_VALID | _PAGE_ACCESSED | _PAGE_HW_WRITE)
+#else
+# define _PAGE_DIRECTORY (_PAGE_VALID|_PAGE_ACCESSED|_PAGE_HW_WRITE|_PAGE_CA_WB)
+#endif
 
 #else /* no mmu */
 
@@ -145,23 +151,23 @@
  * What follows is the closest we can get by reasonable means..
  * See linux/mm/mmap.c for protection_map[] array that uses these definitions.
  */
-#define __P000  PAGE_NONE       /* private --- */
-#define __P001  PAGE_READONLY   /* private --r */
-#define __P010  PAGE_COPY       /* private -w- */
-#define __P011  PAGE_COPY       /* private -wr */
-#define __P100  PAGE_READONLY   /* private x-- */
-#define __P101  PAGE_READONLY   /* private x-r */
-#define __P110  PAGE_COPY       /* private xw- */
-#define __P111  PAGE_COPY       /* private xwr */
-
-#define __S000  PAGE_NONE       /* shared  --- */
-#define __S001  PAGE_READONLY   /* shared  --r */
-#define __S010  PAGE_SHARED     /* shared  -w- */
-#define __S011  PAGE_SHARED     /* shared  -wr */
-#define __S100  PAGE_READONLY   /* shared  x-- */
-#define __S101  PAGE_READONLY   /* shared  x-r */
-#define __S110  PAGE_SHARED     /* shared  xw- */
-#define __S111  PAGE_SHARED     /* shared  xwr */
+#define __P000  PAGE_NONE               /* private --- */
+#define __P001  PAGE_READONLY           /* private --r */
+#define __P010  PAGE_COPY               /* private -w- */
+#define __P011  PAGE_COPY               /* private -wr */
+#define __P100  PAGE_READONLY_EXEC      /* private x-- */
+#define __P101  PAGE_READONLY_EXEC      /* private x-r */
+#define __P110  PAGE_COPY_EXEC          /* private xw- */
+#define __P111  PAGE_COPY_EXEC          /* private xwr */
+
+#define __S000  PAGE_NONE               /* shared  --- */
+#define __S001  PAGE_READONLY           /* shared  --r */
+#define __S010  PAGE_SHARED             /* shared  -w- */
+#define __S011  PAGE_SHARED             /* shared  -wr */
+#define __S100  PAGE_READONLY_EXEC      /* shared  x-- */
+#define __S101  PAGE_READONLY_EXEC      /* shared  x-r */
+#define __S110  PAGE_SHARED_EXEC        /* shared  xw- */
+#define __S111  PAGE_SHARED_EXEC        /* shared  xwr */
 
 #ifndef __ASSEMBLY__
 
@@ -183,35 +189,42 @@ extern pgd_t swapper_pg_dir[PAGE_SIZE/sizeof(pgd_t)];
 #define pmd_page(pmd) virt_to_page(pmd_val(pmd))
 
 /*
- * The following only work if pte_present() is true.
+ * pte status.
  */
-#define pte_none(pte)    (!(pte_val(pte) ^ _PAGE_USER))
-#define pte_present(pte) (pte_val(pte) & _PAGE_VALID)
+#define pte_none(pte)    (pte_val(pte) == _PAGE_INVALID)
+#define pte_present(pte)                                                \
+        (((pte_val(pte) & _PAGE_CA_MASK) != _PAGE_INVALID)              \
+         || ((pte_val(pte) & _PAGE_PROTNONE) == _PAGE_PROTNONE))
 #define pte_clear(mm,addr,ptep)                                         \
-        do { update_pte(ptep, __pte(_PAGE_USER)); } while(0)
+        do { update_pte(ptep, __pte(_PAGE_INVALID)); } while(0)
 
 #define pmd_none(pmd)    (!pmd_val(pmd))
 #define pmd_present(pmd) (pmd_val(pmd) & PAGE_MASK)
-#define pmd_clear(pmdp)  do { set_pmd(pmdp, __pmd(0)); } while (0)
 #define pmd_bad(pmd)     (pmd_val(pmd) & ~PAGE_MASK)
+#define pmd_clear(pmdp)  do { set_pmd(pmdp, __pmd(0)); } while (0)
 
-/* Note: We use the _PAGE_USER bit to indicate write-protect kernel memory */
-
-static inline int pte_write(pte_t pte) { return pte_val(pte) & _PAGE_RW; }
+static inline int pte_write(pte_t pte) { return pte_val(pte) & _PAGE_WRITABLE; }
 static inline int pte_dirty(pte_t pte) { return pte_val(pte) & _PAGE_DIRTY; }
 static inline int pte_young(pte_t pte) { return pte_val(pte) & _PAGE_ACCESSED; }
 static inline int pte_file(pte_t pte)  { return pte_val(pte) & _PAGE_FILE; }
-static inline pte_t pte_wrprotect(pte_t pte)    { pte_val(pte) &= ~(_PAGE_RW | _PAGE_WRENABLE); return pte; }
-static inline pte_t pte_mkclean(pte_t pte)      { pte_val(pte) &= ~_PAGE_DIRTY; return pte; }
-static inline pte_t pte_mkold(pte_t pte)        { pte_val(pte) &= ~_PAGE_ACCESSED; return pte; }
-static inline pte_t pte_mkdirty(pte_t pte)      { pte_val(pte) |= _PAGE_DIRTY; return pte; }
-static inline pte_t pte_mkyoung(pte_t pte)      { pte_val(pte) |= _PAGE_ACCESSED; return pte; }
-static inline pte_t pte_mkwrite(pte_t pte)      { pte_val(pte) |= _PAGE_RW; return pte; }
+static inline pte_t pte_wrprotect(pte_t pte)    
+        { pte_val(pte) &= ~(_PAGE_WRITABLE | _PAGE_HW_WRITE); return pte; }
+static inline pte_t pte_mkclean(pte_t pte)
+        { pte_val(pte) &= ~(_PAGE_DIRTY | _PAGE_HW_WRITE); return pte; }
+static inline pte_t pte_mkold(pte_t pte)
+        { pte_val(pte) &= ~_PAGE_ACCESSED; return pte; }
+static inline pte_t pte_mkdirty(pte_t pte)
+        { pte_val(pte) |= _PAGE_DIRTY; return pte; }
+static inline pte_t pte_mkyoung(pte_t pte)
+        { pte_val(pte) |= _PAGE_ACCESSED; return pte; }
+static inline pte_t pte_mkwrite(pte_t pte)
+        { pte_val(pte) |= _PAGE_WRITABLE; return pte; }
 
 /*
  * Conversion functions: convert a page and protection to a page entry,
  * and a page entry and page directory to the page they refer to.
  */
+
 #define pte_pfn(pte)            (pte_val(pte) >> PAGE_SHIFT)
 #define pte_same(a,b)           (pte_val(a) == pte_val(b))
 #define pte_page(x)             pfn_to_page(pte_pfn(x))
@@ -231,9 +244,6 @@ static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
 static inline void update_pte(pte_t *ptep, pte_t pteval)
 {
         *ptep = pteval;
-#if (DCACHE_WAY_SIZE > PAGE_SIZE) && XCHAL_DCACHE_IS_WRITEBACK
-        __asm__ __volatile__ ("memw; dhwb %0, 0; dsync" :: "a" (ptep));
-#endif
 }
 
 struct mm_struct;
@@ -249,9 +259,6 @@ static inline void
 set_pmd(pmd_t *pmdp, pmd_t pmdval)
 {
         *pmdp = pmdval;
-#if (DCACHE_WAY_SIZE > PAGE_SIZE) && XCHAL_DCACHE_IS_WRITEBACK
-        __asm__ __volatile__ ("memw; dhwb %0, 0; dsync" :: "a" (pmdp));
-#endif
 }
 
 struct vm_area_struct;
@@ -306,52 +313,34 @@ ptep_set_wrprotect(struct mm_struct *mm, unsigned long addr, pte_t *ptep)
 
 /*
  * Encode and decode a swap entry.
- * Each PTE in a process VM's page table is either:
- *   "present" -- valid and not swapped out, protection bits are meaningful;
- *   "not present" -- which further subdivides in these two cases:
- *      "none" -- no mapping at all; identified by pte_none(), set by pte_clear(
- *      "swapped out" -- the page is swapped out, and the SWP macros below
- *                      are used to store swap file info in the PTE itself.
- *
- * In the Xtensa processor MMU, any PTE entries in user space (or anywhere
- * in virtual memory that can map differently across address spaces)
- * must have a correct ring value that represents the RASID field that
- * is changed when switching address spaces.  Eg. such PTE entries cannot
- * be set to ring zero, because that can cause a (global) kernel ASID
- * entry to be created in the TLBs (even with invalid cache attribute),
- * potentially causing a multihit exception when going back to another
- * address space that mapped the same virtual address at another ring.
- *
- * SO: we avoid using ring bits (_PAGE_RING_MASK) in "not present" PTEs.
- * We also avoid using the _PAGE_VALID bit which must be zero for non-present
- * pages.
  *
- * We end up with the following available bits:  1..3 and 7..31.
- * We don't bother with 1..3 for now (we can use them later if needed),
- * and chose to allocate 6 bits for SWP_TYPE and the remaining 19 bits
- * for SWP_OFFSET.  At least 5 bits are needed for SWP_TYPE, because it
- * is currently implemented as an index into swap_info[MAX_SWAPFILES]
- * and MAX_SWAPFILES is currently defined as 32 in <linux/swap.h>.
- * However, for some reason all other architectures in the 2.4 kernel
- * reserve either 6, 7, or 8 bits so I'll not detract from that for now.  :)
- * SWP_OFFSET is an offset into the swap file in page-size units, so
- * with 4 kB pages, 19 bits supports a maximum swap file size of 2 GB.
- *
- * FIXME:  2 GB isn't very big.  Other bits can be used to allow
- * larger swap sizes.  In the meantime, it appears relatively easy to get
- * around the 2 GB limitation by simply using multiple swap files.
+ * Format of swap pte:
+ *  bit    0       MBZ
+ *  bit    1       page-file (must be zero)
+ *  bits   2 -  3  page hw access mode (must be 11: _PAGE_INVALID)
+ *  bits   4 -  5  ring protection (must be 01: _PAGE_USER)
+ *  bits   6 - 10  swap type (5 bits -> 32 types)
+ *  bits  11 - 31  swap offset / PAGE_SIZE (21 bits -> 8GB)
+ 
+ * Format of file pte:
+ *  bit    0       MBZ
+ *  bit    1       page-file (must be one: _PAGE_FILE)
+ *  bits   2 -  3  page hw access mode (must be 11: _PAGE_INVALID)
+ *  bits   4 -  5  ring protection (must be 01: _PAGE_USER)
+ *  bits   6 - 31  file offset / PAGE_SIZE
  */
 
-#define __swp_type(entry)       (((entry).val >> 7) & 0x3f)
-#define __swp_offset(entry)     ((entry).val >> 13)
-#define __swp_entry(type,offs)  ((swp_entry_t) {((type) << 7) | ((offs) << 13)})
+#define __swp_type(entry)       (((entry).val >> 6) & 0x1f)
+#define __swp_offset(entry)     ((entry).val >> 11)
+#define __swp_entry(type,offs)  \
+        ((swp_entry_t) {((type) << 6) | ((offs) << 11) | _PAGE_INVALID})
 #define __pte_to_swp_entry(pte) ((swp_entry_t) { pte_val(pte) })
 #define __swp_entry_to_pte(x)   ((pte_t) { (x).val })
 
-#define PTE_FILE_MAX_BITS       29
-#define pte_to_pgoff(pte)       (pte_val(pte) >> 3)
-#define pgoff_to_pte(off)       ((pte_t) { ((off) << 3) | _PAGE_FILE })
-
+#define PTE_FILE_MAX_BITS       28
+#define pte_to_pgoff(pte)       (pte_val(pte) >> 4)
+#define pgoff_to_pte(off)       \
+        ((pte_t) { ((off) << 4) | _PAGE_INVALID | _PAGE_FILE })
 
 #endif /*  !defined (__ASSEMBLY__) */