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Linux/arch/alpha/mm/fault.c

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  1 /*
  2  *  linux/arch/alpha/mm/fault.c
  3  *
  4  *  Copyright (C) 1995  Linus Torvalds
  5  */
  6 
  7 #include <linux/config.h>
  8 #include <linux/sched.h>
  9 #include <linux/kernel.h>
 10 #include <linux/mm.h>
 11 #include <asm/io.h>
 12 
 13 #define __EXTERN_INLINE inline
 14 #include <asm/mmu_context.h>
 15 #include <asm/tlbflush.h>
 16 #undef  __EXTERN_INLINE
 17 
 18 #include <linux/signal.h>
 19 #include <linux/errno.h>
 20 #include <linux/string.h>
 21 #include <linux/types.h>
 22 #include <linux/ptrace.h>
 23 #include <linux/mman.h>
 24 #include <linux/smp.h>
 25 #include <linux/smp_lock.h>
 26 #include <linux/interrupt.h>
 27 #include <linux/module.h>
 28 
 29 #include <asm/system.h>
 30 #include <asm/uaccess.h>
 31 
 32 extern void die_if_kernel(char *,struct pt_regs *,long, unsigned long *);
 33 
 34 
 35 /*
 36  * Force a new ASN for a task.
 37  */
 38 
 39 #ifndef CONFIG_SMP
 40 unsigned long last_asn = ASN_FIRST_VERSION;
 41 #endif
 42 
 43 extern void
 44 __load_new_mm_context(struct mm_struct *next_mm)
 45 {
 46         unsigned long mmc;
 47         struct pcb_struct *pcb;
 48 
 49         mmc = __get_new_mm_context(next_mm, smp_processor_id());
 50         next_mm->context[smp_processor_id()] = mmc;
 51 
 52         pcb = &current_thread_info()->pcb;
 53         pcb->asn = mmc & HARDWARE_ASN_MASK;
 54         pcb->ptbr = ((unsigned long) next_mm->pgd - IDENT_ADDR) >> PAGE_SHIFT;
 55 
 56         __reload_thread(pcb);
 57 }
 58 
 59 
 60 /*
 61  * This routine handles page faults.  It determines the address,
 62  * and the problem, and then passes it off to handle_mm_fault().
 63  *
 64  * mmcsr:
 65  *      0 = translation not valid
 66  *      1 = access violation
 67  *      2 = fault-on-read
 68  *      3 = fault-on-execute
 69  *      4 = fault-on-write
 70  *
 71  * cause:
 72  *      -1 = instruction fetch
 73  *      0 = load
 74  *      1 = store
 75  *
 76  * Registers $9 through $15 are saved in a block just prior to `regs' and
 77  * are saved and restored around the call to allow exception code to
 78  * modify them.
 79  */
 80 
 81 /* Macro for exception fixup code to access integer registers.  */
 82 #define dpf_reg(r)                                                      \
 83         (((unsigned long *)regs)[(r) <= 8 ? (r) : (r) <= 15 ? (r)-16 :  \
 84                                  (r) <= 18 ? (r)+8 : (r)-10])
 85 
 86 asmlinkage void
 87 do_page_fault(unsigned long address, unsigned long mmcsr,
 88               long cause, struct pt_regs *regs)
 89 {
 90         struct vm_area_struct * vma;
 91         struct mm_struct *mm = current->mm;
 92         const struct exception_table_entry *fixup;
 93         int fault, si_code = SEGV_MAPERR;
 94         siginfo_t info;
 95 
 96         /* As of EV6, a load into $31/$f31 is a prefetch, and never faults
 97            (or is suppressed by the PALcode).  Support that for older CPUs
 98            by ignoring such an instruction.  */
 99         if (cause == 0) {
100                 unsigned int insn;
101                 __get_user(insn, (unsigned int *)regs->pc);
102                 if ((insn >> 21 & 0x1f) == 0x1f &&
103                     /* ldq ldl ldt lds ldg ldf ldwu ldbu */
104                     (1ul << (insn >> 26) & 0x30f00001400ul)) {
105                         regs->pc += 4;
106                         return;
107                 }
108         }
109 
110         /* If we're in an interrupt context, or have no user context,
111            we must not take the fault.  */
112         if (!mm || in_interrupt())
113                 goto no_context;
114 
115 #ifdef CONFIG_ALPHA_LARGE_VMALLOC
116         if (address >= TASK_SIZE)
117                 goto vmalloc_fault;
118 #endif
119 
120         down_read(&mm->mmap_sem);
121         vma = find_vma(mm, address);
122         if (!vma)
123                 goto bad_area;
124         if (vma->vm_start <= address)
125                 goto good_area;
126         if (!(vma->vm_flags & VM_GROWSDOWN))
127                 goto bad_area;
128         if (expand_stack(vma, address))
129                 goto bad_area;
130 
131         /* Ok, we have a good vm_area for this memory access, so
132            we can handle it.  */
133  good_area:
134         si_code = SEGV_ACCERR;
135         if (cause < 0) {
136                 if (!(vma->vm_flags & VM_EXEC))
137                         goto bad_area;
138         } else if (!cause) {
139                 /* Allow reads even for write-only mappings */
140                 if (!(vma->vm_flags & (VM_READ | VM_WRITE)))
141                         goto bad_area;
142         } else {
143                 if (!(vma->vm_flags & VM_WRITE))
144                         goto bad_area;
145         }
146 
147  survive:
148         /* If for any reason at all we couldn't handle the fault,
149            make sure we exit gracefully rather than endlessly redo
150            the fault.  */
151         fault = handle_mm_fault(mm, vma, address, cause > 0);
152         up_read(&mm->mmap_sem);
153 
154         switch (fault) {
155               case VM_FAULT_MINOR:
156                 current->min_flt++;
157                 break;
158               case VM_FAULT_MAJOR:
159                 current->maj_flt++;
160                 break;
161               case VM_FAULT_SIGBUS:
162                 goto do_sigbus;
163               case VM_FAULT_OOM:
164                 goto out_of_memory;
165               default:
166                 BUG();
167         }
168         return;
169 
170         /* Something tried to access memory that isn't in our memory map.
171            Fix it, but check if it's kernel or user first.  */
172  bad_area:
173         up_read(&mm->mmap_sem);
174 
175         if (user_mode(regs))
176                 goto do_sigsegv;
177 
178  no_context:
179         /* Are we prepared to handle this fault as an exception?  */
180         if ((fixup = search_exception_tables(regs->pc)) != 0) {
181                 unsigned long newpc;
182                 newpc = fixup_exception(dpf_reg, fixup, regs->pc);
183                 regs->pc = newpc;
184                 return;
185         }
186 
187         /* Oops. The kernel tried to access some bad page. We'll have to
188            terminate things with extreme prejudice.  */
189         printk(KERN_ALERT "Unable to handle kernel paging request at "
190                "virtual address %016lx\n", address);
191         die_if_kernel("Oops", regs, cause, (unsigned long*)regs - 16);
192         do_exit(SIGKILL);
193 
194         /* We ran out of memory, or some other thing happened to us that
195            made us unable to handle the page fault gracefully.  */
196  out_of_memory:
197         if (current->pid == 1) {
198                 yield();
199                 down_read(&mm->mmap_sem);
200                 goto survive;
201         }
202         printk(KERN_ALERT "VM: killing process %s(%d)\n",
203                current->comm, current->pid);
204         if (!user_mode(regs))
205                 goto no_context;
206         do_exit(SIGKILL);
207 
208  do_sigbus:
209         /* Send a sigbus, regardless of whether we were in kernel
210            or user mode.  */
211         info.si_signo = SIGBUS;
212         info.si_errno = 0;
213         info.si_code = BUS_ADRERR;
214         info.si_addr = (void *) address;
215         force_sig_info(SIGBUS, &info, current);
216         if (!user_mode(regs))
217                 goto no_context;
218         return;
219 
220  do_sigsegv:
221         info.si_signo = SIGSEGV;
222         info.si_errno = 0;
223         info.si_code = si_code;
224         info.si_addr = (void *) address;
225         force_sig_info(SIGSEGV, &info, current);
226         return;
227 
228 #ifdef CONFIG_ALPHA_LARGE_VMALLOC
229  vmalloc_fault:
230         if (user_mode(regs))
231                 goto do_sigsegv;
232         else {
233                 /* Synchronize this task's top level page-table
234                    with the "reference" page table from init.  */
235                 long index = pgd_index(address);
236                 pgd_t *pgd, *pgd_k;
237 
238                 pgd = current->active_mm->pgd + index;
239                 pgd_k = swapper_pg_dir + index;
240                 if (!pgd_present(*pgd) && pgd_present(*pgd_k)) {
241                         pgd_val(*pgd) = pgd_val(*pgd_k);
242                         return;
243                 }
244                 goto no_context;
245         }
246 #endif
247 }
248 

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