arch/sh64/mm/tlbmiss.c

   1 /*
   2  * This file is subject to the terms and conditions of the GNU General Public
   3  * License.  See the file "COPYING" in the main directory of this archive
   4  * for more details.
   5  *
   6  * arch/sh64/mm/tlbmiss.c
   7  *
   8  * Original code from fault.c
   9  * Copyright (C) 2000, 2001  Paolo Alberelli
  10  *
  11  * Fast PTE->TLB refill path
  12  * Copyright (C) 2003 Richard.Curnow@superh.com
  13  *
  14  * IMPORTANT NOTES :
  15  * The do_fast_page_fault function is called from a context in entry.S where very few registers
  16  * have been saved.  In particular, the code in this file must be compiled not to use ANY
  17  * caller-save regiseters that are not part of the restricted save set.  Also, it means that
  18  * code in this file must not make calls to functions elsewhere in the kernel, or else the
  19  * excepting context will see corruption in its caller-save registers.  Plus, the entry.S save
  20  * area is non-reentrant, so this code has to run with SR.BL==1, i.e. no interrupts taken inside
  21  * it and panic on any exception.
  22  *
  23  */
  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/smp_lock.h>
  36 #include <linux/interrupt.h>
  37
  38 #include <asm/system.h>
  39 #include <asm/tlb.h>
  40 #include <asm/io.h>
  41 #include <asm/uaccess.h>
  42 #include <asm/pgalloc.h>
  43 #include <asm/mmu_context.h>
  44 #include <asm/registers.h>              /* required by inline asm statements */
  45
  46 /* Callable from fault.c, so not static */
  47 inline void __do_tlb_refill(unsigned long address,
  48                             unsigned long long is_text_not_data, pte_t *pte)
  49 {
  50         unsigned long long ptel;
  51         unsigned long long pteh=0;
  52         struct tlb_info *tlbp;
  53         unsigned long long next;
  54
  55         /* Get PTEL first */
  56         ptel = pte_val(*pte);
  57
  58         /*
  59          * Set PTEH register
  60          */
  61         pteh = address & MMU_VPN_MASK;
  62
  63         /* Sign extend based on neff. */
  64 #if (NEFF == 32)
  65         /* Faster sign extension */
  66         pteh = (unsigned long long)(signed long long)(signed long)pteh;
  67 #else
  68         /* General case */
  69         pteh = (pteh & NEFF_SIGN) ? (pteh | NEFF_MASK) : pteh;
  70 #endif
  71
  72         /* Set the ASID. */
  73         pteh |= get_asid() << PTEH_ASID_SHIFT;
  74         pteh |= PTEH_VALID;
  75
  76         /* Set PTEL register, set_pte has performed the sign extension */
  77         ptel &= _PAGE_FLAGS_HARDWARE_MASK; /* drop software flags */
  78
  79         tlbp = is_text_not_data ? &(cpu_data->itlb) : &(cpu_data->dtlb);
  80         next = tlbp->next;
  81         __flush_tlb_slot(next);
  82         asm volatile ("putcfg %0,1,%2\n\n\t"
  83                       "putcfg %0,0,%1\n"
  84                       :  : "r" (next), "r" (pteh), "r" (ptel) );
  85
  86         next += TLB_STEP;
  87         if (next > tlbp->last) next = tlbp->first;
  88         tlbp->next = next;
  89
  90 }
  91
  92 static int handle_vmalloc_fault(struct mm_struct *mm, unsigned long protection_flags,
  93                                 unsigned long long textaccess,
  94                                 unsigned long address)
  95 {
  96         pgd_t *dir;
  97         pmd_t *pmd;
  98         static pte_t *pte;
  99         pte_t entry;
 100
 101         dir = pgd_offset_k(address);
 102         pmd = pmd_offset(dir, address);
 103
 104         if (pmd_none(*pmd)) {
 105                 return 0;
 106         }
 107
 108         if (pmd_bad(*pmd)) {
 109                 pmd_clear(pmd);
 110                 return 0;
 111         }
 112
 113         pte = pte_offset_kernel(pmd, address);
 114         entry = *pte;
 115
 116         if (pte_none(entry) || !pte_present(entry)) {
 117                 return 0;
 118         }
 119
 120         if ((pte_val(entry) & protection_flags) != protection_flags) {
 121                 return 0;
 122         }
 123
 124         __do_tlb_refill(address, textaccess, pte);
 125
 126         return 1;
 127 }
 128
 129 static int handle_tlbmiss(struct mm_struct *mm, unsigned long long protection_flags,
 130                         unsigned long long textaccess,
 131                         unsigned long address)
 132 {
 133         pgd_t *dir;
 134         pmd_t *pmd;
 135         pte_t *pte;
 136         pte_t entry;
 137
 138         /* NB. The PGD currently only contains a single entry - there is no
 139            page table tree stored for the top half of the address space since
 140            virtual pages in that region should never be mapped in user mode.
 141            (In kernel mode, the only things in that region are the 512Mb super
 142            page (locked in), and vmalloc (modules) +  I/O device pages (handled
 143            by handle_vmalloc_fault), so no PGD for the upper half is required
 144            by kernel mode either).
 145
 146            See how mm->pgd is allocated and initialised in pgd_alloc to see why
 147            the next test is necessary.  - RPC */
 148         if (address >= (unsigned long) TASK_SIZE) {
 149                 /* upper half - never has page table entries. */
 150                 return 0;
 151         }
 152         dir = pgd_offset(mm, address);
 153         if (pgd_none(*dir)) {
 154                 return 0;
 155         }
 156         if (!pgd_present(*dir)) {
 157                 return 0;
 158         }
 159
 160         pmd = pmd_offset(dir, address);
 161         if (pmd_none(*pmd)) {
 162                 return 0;
 163         }
 164         if (!pmd_present(*pmd)) {
 165                 return 0;
 166         }
 167         pte = pte_offset_kernel(pmd, address);
 168         entry = *pte;
 169         if (pte_none(entry)) {
 170                 return 0;
 171         }
 172         if (!pte_present(entry)) {
 173                 return 0;
 174         }
 175
 176         /* If the page doesn't have sufficient protection bits set to service the
 177            kind of fault being handled, there's not much point doing the TLB refill.
 178            Punt the fault to the general handler. */
 179         if ((pte_val(entry) & protection_flags) != protection_flags) {
 180                 return 0;
 181         }
 182
 183         __do_tlb_refill(address, textaccess, pte);
 184
 185         return 1;
 186 }
 187
 188 /* Put all this information into one structure so that everything is just arithmetic
 189    relative to a single base address.  This reduces the number of movi/shori pairs needed
 190    just to load addresses of static data. */
 191 struct expevt_lookup {
 192         unsigned short protection_flags[8];
 193         unsigned char  is_text_access[8];
 194         unsigned char  is_write_access[8];
 195 };
 196
 197 #define PRU (1<<9)
 198 #define PRW (1<<8)
 199 #define PRX (1<<7)
 200 #define PRR (1<<6)
 201
 202 #define DIRTY (_PAGE_DIRTY | _PAGE_ACCESSED)
 203 #define YOUNG (_PAGE_ACCESSED)
 204
 205 /* Sized as 8 rather than 4 to allow checking the PTE's PRU bit against whether
 206    the fault happened in user mode or privileged mode. */
 207 static struct expevt_lookup expevt_lookup_table = {
 208         .protection_flags = {PRX, PRX, 0, 0, PRR, PRR, PRW, PRW},
 209         .is_text_access   = {1,   1,   0, 0, 0,   0,   0,   0}
 210 };
 211
 212 /*
 213    This routine handles page faults that can be serviced just by refilling a
 214    TLB entry from an existing page table entry.  (This case represents a very
 215    large majority of page faults.) Return 1 if the fault was successfully
 216    handled.  Return 0 if the fault could not be handled.  (This leads into the
 217    general fault handling in fault.c which deals with mapping file-backed
 218    pages, stack growth, segmentation faults, swapping etc etc)
 219  */
 220 asmlinkage int do_fast_page_fault(unsigned long long ssr_md, unsigned long long expevt,
 221                                   unsigned long address)
 222 {
 223         struct task_struct *tsk;
 224         struct mm_struct *mm;
 225         unsigned long long textaccess;
 226         unsigned long long protection_flags;
 227         unsigned long long index;
 228         unsigned long long expevt4;
 229
 230         /* The next few lines implement a way of hashing EXPEVT into a small array index
 231            which can be used to lookup parameters specific to the type of TLBMISS being
 232            handled.  Note:
 233            ITLBMISS has EXPEVT==0xa40
 234            RTLBMISS has EXPEVT==0x040
 235            WTLBMISS has EXPEVT==0x060
 236         */
 237
 238         expevt4 = (expevt >> 4);
 239         /* TODO : xor ssr_md into this expression too.  Then we can check that PRU is set
 240            when it needs to be. */
 241         index = expevt4 ^ (expevt4 >> 5);
 242         index &= 7;
 243         protection_flags = expevt_lookup_table.protection_flags[index];
 244         textaccess       = expevt_lookup_table.is_text_access[index];
 245
 246 #ifdef CONFIG_SH64_PROC_TLB
 247         ++calls_to_do_fast_page_fault;
 248 #endif
 249
 250         /* SIM
 251          * Note this is now called with interrupts still disabled
 252          * This is to cope with being called for a missing IO port
 253          * address with interupts disabled. This should be fixed as
 254          * soon as we have a better 'fast path' miss handler.
 255          *
 256          * Plus take care how you try and debug this stuff.
 257          * For example, writing debug data to a port which you
 258          * have just faulted on is not going to work.
 259          */
 260
 261         tsk = current;
 262         mm = tsk->mm;
 263
 264         if ((address >= VMALLOC_START && address < VMALLOC_END) ||
 265             (address >= IOBASE_VADDR  && address < IOBASE_END)) {
 266                 if (ssr_md) {
 267                         /* Process-contexts can never have this address range mapped */
 268                         if (handle_vmalloc_fault(mm, protection_flags, textaccess, address)) {
 269                                 return 1;
 270                         }
 271                 }
 272         } else if (!in_interrupt() && mm) {
 273                 if (handle_tlbmiss(mm, protection_flags, textaccess, address)) {
 274                         return 1;
 275                 }
 276         }
 277
 278         return 0;
 279 }
 280