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