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Linux/arch/sh64/mm/tlbmiss.c

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  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/hardirq.h>
 44 #include <asm/mmu_context.h>
 45 #include <asm/registers.h>              /* required by inline asm statements */
 46 
 47 /* Callable from fault.c, so not static */
 48 __inline__ void __do_tlb_refill(unsigned long address, 
 49                             unsigned long long is_text_not_data, pte_t *pte)
 50 {
 51         unsigned long long ptel;
 52         unsigned long long pteh=0;
 53         struct tlb_info *tlbp;
 54         unsigned long long next;
 55 
 56         /* Get PTEL first */
 57         ptel = pte_val(*pte);
 58 
 59         /*
 60          * Set PTEH register
 61          */
 62         pteh = address & MMU_VPN_MASK;
 63 
 64         /* Sign extend based on neff. */
 65 #if (NEFF == 32)
 66         /* Faster sign extension */
 67         pteh = (unsigned long long)(signed long long)(signed long)pteh;
 68 #else
 69         /* General case */
 70         pteh = (pteh & NEFF_SIGN) ? (pteh | NEFF_MASK) : pteh;
 71 #endif
 72 
 73         /* Set the ASID. */
 74         pteh |= get_asid() << PTEH_ASID_SHIFT;
 75      
 76         pteh |= PTEH_VALID;
 77 
 78         /* Set PTEL register, set_pte has performed the sign extension */
 79         ptel &= _PAGE_FLAGS_HARDWARE_MASK; /* drop software flags */
 80         ptel |= _PAGE_FLAGS_HARDWARE_DEFAULT; /* add default flags */
 81 
 82         tlbp = is_text_not_data ? &(cpu_data->itlb) : &(cpu_data->dtlb);
 83         next = tlbp->next;
 84         __flush_tlb_slot(next);
 85         asm volatile ("putcfg %0,1,%2\n\n\t"
 86                       "putcfg %0,0,%1\n"
 87                       :  : "r" (next), "r" (pteh), "r" (ptel) );
 88 
 89         next += TLB_STEP;
 90         if (next > tlbp->last) next = tlbp->first;
 91         tlbp->next = next;
 92 
 93 }
 94 
 95 static int handle_vmalloc_fault(struct mm_struct *mm, unsigned long protection_flags, 
 96                                 unsigned long long textaccess,
 97                                 unsigned long address)
 98 {
 99         pgd_t *dir;
100         pmd_t *pmd;
101         static pte_t *pte;
102         pte_t entry;
103 
104         dir = pgd_offset_k(address);
105         pmd = pmd_offset(dir, address);
106 
107         
108         if (pmd_none(*pmd)) {
109                 return 0;
110         }
111         if (pmd_bad(*pmd)) {
112                 pmd_clear(pmd);
113                 return 0;
114         }
115         pte = pte_offset(pmd, address);
116         entry = *pte;
117         if (pte_none(entry) || !pte_present(entry)) {
118                 return 0;
119         }
120 
121         if ((pte_val(entry) & protection_flags) != protection_flags) {
122                 return 0;
123         }
124 
125         __do_tlb_refill(address, textaccess, pte);
126 
127         return 1;
128 }
129 
130 static int handle_tlbmiss(struct mm_struct *mm, unsigned long long protection_flags,
131                         unsigned long long textaccess,
132                         unsigned long address)
133 {       
134         pgd_t *dir;
135         pmd_t *pmd;
136         pte_t *pte;
137         pte_t entry;
138         
139 
140         /* NB. The PGD currently only contains a single entry - there is no
141            page table tree stored for the top half of the address space since
142            virtual pages in that region should never be mapped in user mode.
143            (In kernel mode, the only things in that region are the 512Mb super
144            page (locked in), and vmalloc (modules) +  I/O device pages (handled
145            by handle_vmalloc_fault), so no PGD for the upper half is required
146            by kernel mode either).
147 
148            See how mm->pgd is allocated and initialised in pgd_alloc to see why
149            the next test is necessary.  - RPC */
150         if (address >= (unsigned long) TASK_SIZE) {
151                 /* upper half - never has page table entries. */
152                 return 0;
153         }
154         dir = pgd_offset(mm, address);
155         if (pgd_none(*dir)) {
156                 return 0;
157         }
158         if (!pgd_present(*dir)) {
159                 return 0;
160         }
161 
162         pmd = pmd_offset(dir, address);
163         if (pmd_none(*pmd)) {
164                 return 0;
165         }
166         if (!pmd_present(*pmd)) {
167                 return 0;
168         }
169         pte = pte_offset(pmd, address);
170         entry = *pte;
171         if (pte_none(entry)) {
172                 return 0;
173         }
174         if (!pte_present(entry)) {
175                 return 0;
176         }
177 
178         /* If the page doesn't have sufficient protection bits set to service the
179            kind of fault being handled, there's not much point doing the TLB refill.
180            Punt the fault to the general handler. */
181         if ((pte_val(entry) & protection_flags) != protection_flags) {
182                 return 0;
183         }
184 
185         __do_tlb_refill(address, textaccess, pte);
186 
187         return 1;
188 }
189 
190 /* Put all this information into one structure so that everything is just arithmetic
191    relative to a single base address.  This reduces the number of movi/shori pairs needed
192    just to load addresses of static data. */
193 struct expevt_lookup {
194         unsigned short protection_flags[8];
195         unsigned char  is_text_access[8];
196         unsigned char  is_write_access[8];
197 };
198 
199 #define PRU (1<<9)
200 #define PRW (1<<8)
201 #define PRX (1<<7)
202 #define PRR (1<<6)
203 
204 #define DIRTY (_PAGE_DIRTY | _PAGE_ACCESSED)
205 #define YOUNG (_PAGE_ACCESSED)
206 
207 /* Sized as 8 rather than 4 to allow checking the PTE's PRU bit against whether
208    the fault happened in user mode or privileged mode. */
209 static struct expevt_lookup expevt_lookup_table = {
210         .protection_flags = {PRX, PRX, 0, 0, PRR, PRR, PRW, PRW},
211         .is_text_access   = {1,   1,   0, 0, 0,   0,   0,   0}
212 };
213 
214 /*
215    This routine handles page faults that can be serviced just by refilling a
216    TLB entry from an existing page table entry.  (This case represents a very
217    large majority of page faults.) Return 1 if the fault was successfully
218    handled.  Return 0 if the fault could not be handled.  (This leads into the
219    general fault handling in fault.c which deals with mapping file-backed
220    pages, stack growth, segmentation faults, swapping etc etc)
221  */
222 asmlinkage int do_fast_page_fault(unsigned long long ssr_md, unsigned long long expevt,
223                                   unsigned long address)
224 {
225         struct task_struct *tsk;
226         struct mm_struct *mm;
227         unsigned long long textaccess;
228         unsigned long long protection_flags;
229         unsigned long long index;
230         unsigned long long expevt4;
231 
232         /* The next few lines implement a way of hashing EXPEVT into a small array index
233            which can be used to lookup parameters specific to the type of TLBMISS being
234            handled.  Note:
235            ITLBMISS has EXPEVT==0xa40
236            RTLBMISS has EXPEVT==0x040
237            WTLBMISS has EXPEVT==0x060
238         */
239 
240         expevt4 = (expevt >> 4);
241         /* TODO : xor ssr_md into this expression too.  Then we can check that PRU is set
242            when it needs to be. */
243         index = expevt4 ^ (expevt4 >> 5);
244         index &= 7;
245         protection_flags = expevt_lookup_table.protection_flags[index];
246         textaccess       = expevt_lookup_table.is_text_access[index];
247 
248 #if (CONFIG_SH64_PROC_TLB)
249         ++calls_to_do_fast_page_fault;
250 #endif
251 
252         /* SIM
253          * Note this is now called with interrupts still disabled
254          * This is to cope with being called for a missing IO port
255          * address with interupts disabled. This should be fixed as
256          * soon as we have a better 'fast path' miss handler.
257          *
258          * Plus take care how you try and debug this stuff.
259          * For example, writing debug data to a port which you
260          * have just faulted on is not going to work.
261          */
262 
263         tsk = current;
264         mm = tsk->mm;
265 
266         if ((address >= VMALLOC_START && address < VMALLOC_END) ||
267             (address >= IOBASE_VADDR  && address < IOBASE_END)) {
268                 if (ssr_md) {
269                         /* Process-contexts can never have this address range mapped */
270                         if (handle_vmalloc_fault(mm, protection_flags, textaccess, address)) {
271                                 return 1;
272                         }
273                 }
274         } else if (!in_interrupt() && mm) {
275                 if (handle_tlbmiss(mm, protection_flags, textaccess, address)) {
276                         return 1;
277                 }
278         }
279 
280         return 0;
281 
282 }
283 
284 

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