arch/sh/mm/tlbex_64.c

   1 /*
   2  * The SH64 TLB miss.
   3  *
   4  * Original code from fault.c
   5  * Copyright (C) 2000, 2001  Paolo Alberelli
   6  *
   7  * Fast PTE->TLB refill path
   8  * Copyright (C) 2003 Richard.Curnow@superh.com
   9  *
  10  * IMPORTANT NOTES :
  11  * The do_fast_page_fault function is called from a context in entry.S
  12  * where very few registers have been saved.  In particular, the code in
  13  * this file must be compiled not to use ANY caller-save registers that
  14  * are not part of the restricted save set.  Also, it means that code in
  15  * this file must not make calls to functions elsewhere in the kernel, or
  16  * else the excepting context will see corruption in its caller-save
  17  * registers.  Plus, the entry.S save area is non-reentrant, so this code
  18  * has to run with SR.BL==1, i.e. no interrupts taken inside it and panic
  19  * on any exception.
  20  *
  21  * This file is subject to the terms and conditions of the GNU General Public
  22  * License.  See the file "COPYING" in the main directory of this archive
  23  * for more details.
  24  */
  25 #include <linux/signal.h>
  26 #include <linux/sched.h>
  27 #include <linux/kernel.h>
  28 #include <linux/errno.h>
  29 #include <linux/string.h>
  30 #include <linux/types.h>
  31 #include <linux/ptrace.h>
  32 #include <linux/mman.h>
  33 #include <linux/mm.h>
  34 #include <linux/smp.h>
  35 #include <linux/interrupt.h>
  36 #include <linux/kprobes.h>
  37 #include <asm/tlb.h>
  38 #include <asm/io.h>
  39 #include <linux/uaccess.h>
  40 #include <asm/pgalloc.h>
  41 #include <asm/mmu_context.h>
  42
  43 static int handle_tlbmiss(unsigned long long protection_flags,
  44                           unsigned long address)
  45 {
  46         pgd_t *pgd;
  47         pud_t *pud;
  48         pmd_t *pmd;
  49         pte_t *pte;
  50         pte_t entry;
  51
  52         if (is_vmalloc_addr((void *)address)) {
  53                 pgd = pgd_offset_k(address);
  54         } else {
  55                 if (unlikely(address >= TASK_SIZE || !current->mm))
  56                         return 1;
  57
  58                 pgd = pgd_offset(current->mm, address);
  59         }
  60
  61         pud = pud_offset(pgd, address);
  62         if (pud_none(*pud) || !pud_present(*pud))
  63                 return 1;
  64
  65         pmd = pmd_offset(pud, address);
  66         if (pmd_none(*pmd) || !pmd_present(*pmd))
  67                 return 1;
  68
  69         pte = pte_offset_kernel(pmd, address);
  70         entry = *pte;
  71         if (pte_none(entry) || !pte_present(entry))
  72                 return 1;
  73
  74         /*
  75          * If the page doesn't have sufficient protection bits set to
  76          * service the kind of fault being handled, there's not much
  77          * point doing the TLB refill.  Punt the fault to the general
  78          * handler.
  79          */
  80         if ((pte_val(entry) & protection_flags) != protection_flags)
  81                 return 1;
  82
  83         update_mmu_cache(NULL, address, pte);
  84
  85         return 0;
  86 }
  87
  88 /*
  89  * Put all this information into one structure so that everything is just
  90  * arithmetic relative to a single base address.  This reduces the number
  91  * of movi/shori pairs needed just to load addresses of static data.
  92  */
  93 struct expevt_lookup {
  94         unsigned short protection_flags[8];
  95         unsigned char  is_text_access[8];
  96         unsigned char  is_write_access[8];
  97 };
  98
  99 #define PRU (1<<9)
 100 #define PRW (1<<8)
 101 #define PRX (1<<7)
 102 #define PRR (1<<6)
 103
 104 /* Sized as 8 rather than 4 to allow checking the PTE's PRU bit against whether
 105    the fault happened in user mode or privileged mode. */
 106 static struct expevt_lookup expevt_lookup_table = {
 107         .protection_flags = {PRX, PRX, 0, 0, PRR, PRR, PRW, PRW},
 108         .is_text_access   = {1,   1,   0, 0, 0,   0,   0,   0}
 109 };
 110
 111 static inline unsigned int
 112 expevt_to_fault_code(unsigned long expevt)
 113 {
 114         if (expevt == 0xa40)
 115                 return FAULT_CODE_ITLB;
 116         else if (expevt == 0x060)
 117                 return FAULT_CODE_WRITE;
 118
 119         return 0;
 120 }
 121
 122 /*
 123    This routine handles page faults that can be serviced just by refilling a
 124    TLB entry from an existing page table entry.  (This case represents a very
 125    large majority of page faults.) Return 1 if the fault was successfully
 126    handled.  Return 0 if the fault could not be handled.  (This leads into the
 127    general fault handling in fault.c which deals with mapping file-backed
 128    pages, stack growth, segmentation faults, swapping etc etc)
 129  */
 130 asmlinkage int __kprobes
 131 do_fast_page_fault(unsigned long long ssr_md, unsigned long long expevt,
 132                    unsigned long address)
 133 {
 134         unsigned long long protection_flags;
 135         unsigned long long index;
 136         unsigned long long expevt4;
 137         unsigned int fault_code;
 138
 139         /* The next few lines implement a way of hashing EXPEVT into a
 140          * small array index which can be used to lookup parameters
 141          * specific to the type of TLBMISS being handled.
 142          *
 143          * Note:
 144          *      ITLBMISS has EXPEVT==0xa40
 145          *      RTLBMISS has EXPEVT==0x040
 146          *      WTLBMISS has EXPEVT==0x060
 147          */
 148         expevt4 = (expevt >> 4);
 149         /* TODO : xor ssr_md into this expression too. Then we can check
 150          * that PRU is set when it needs to be. */
 151         index = expevt4 ^ (expevt4 >> 5);
 152         index &= 7;
 153
 154         fault_code = expevt_to_fault_code(expevt);
 155
 156         protection_flags = expevt_lookup_table.protection_flags[index];
 157
 158         if (expevt_lookup_table.is_text_access[index])
 159                 fault_code |= FAULT_CODE_ITLB;
 160         if (!ssr_md)
 161                 fault_code |= FAULT_CODE_USER;
 162
 163         set_thread_fault_code(fault_code);
 164
 165         return handle_tlbmiss(protection_flags, address);
 166 }