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