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Linux/arch/alpha/mm/fault.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  *  linux/arch/alpha/mm/fault.c
  4  *
  5  *  Copyright (C) 1995  Linus Torvalds
  6  */
  7 
  8 #include <linux/sched/signal.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/interrupt.h>
 26 #include <linux/extable.h>
 27 #include <linux/uaccess.h>
 28 #include <linux/perf_event.h>
 29 
 30 extern void die_if_kernel(char *,struct pt_regs *,long, unsigned long *);
 31 
 32 
 33 /*
 34  * Force a new ASN for a task.
 35  */
 36 
 37 #ifndef CONFIG_SMP
 38 unsigned long last_asn = ASN_FIRST_VERSION;
 39 #endif
 40 
 41 void
 42 __load_new_mm_context(struct mm_struct *next_mm)
 43 {
 44         unsigned long mmc;
 45         struct pcb_struct *pcb;
 46 
 47         mmc = __get_new_mm_context(next_mm, smp_processor_id());
 48         next_mm->context[smp_processor_id()] = mmc;
 49 
 50         pcb = &current_thread_info()->pcb;
 51         pcb->asn = mmc & HARDWARE_ASN_MASK;
 52         pcb->ptbr = ((unsigned long) next_mm->pgd - IDENT_ADDR) >> PAGE_SHIFT;
 53 
 54         __reload_thread(pcb);
 55 }
 56 
 57 
 58 /*
 59  * This routine handles page faults.  It determines the address,
 60  * and the problem, and then passes it off to handle_mm_fault().
 61  *
 62  * mmcsr:
 63  *      0 = translation not valid
 64  *      1 = access violation
 65  *      2 = fault-on-read
 66  *      3 = fault-on-execute
 67  *      4 = fault-on-write
 68  *
 69  * cause:
 70  *      -1 = instruction fetch
 71  *      0 = load
 72  *      1 = store
 73  *
 74  * Registers $9 through $15 are saved in a block just prior to `regs' and
 75  * are saved and restored around the call to allow exception code to
 76  * modify them.
 77  */
 78 
 79 /* Macro for exception fixup code to access integer registers.  */
 80 #define dpf_reg(r)                                                      \
 81         (((unsigned long *)regs)[(r) <= 8 ? (r) : (r) <= 15 ? (r)-16 :  \
 82                                  (r) <= 18 ? (r)+10 : (r)-10])
 83 
 84 asmlinkage void
 85 do_page_fault(unsigned long address, unsigned long mmcsr,
 86               long cause, struct pt_regs *regs)
 87 {
 88         struct vm_area_struct * vma;
 89         struct mm_struct *mm = current->mm;
 90         const struct exception_table_entry *fixup;
 91         int si_code = SEGV_MAPERR;
 92         vm_fault_t fault;
 93         unsigned int flags = FAULT_FLAG_DEFAULT;
 94 
 95         /* As of EV6, a load into $31/$f31 is a prefetch, and never faults
 96            (or is suppressed by the PALcode).  Support that for older CPUs
 97            by ignoring such an instruction.  */
 98         if (cause == 0) {
 99                 unsigned int insn;
100                 __get_user(insn, (unsigned int __user *)regs->pc);
101                 if ((insn >> 21 & 0x1f) == 0x1f &&
102                     /* ldq ldl ldt lds ldg ldf ldwu ldbu */
103                     (1ul << (insn >> 26) & 0x30f00001400ul)) {
104                         regs->pc += 4;
105                         return;
106                 }
107         }
108 
109         /* If we're in an interrupt context, or have no user context,
110            we must not take the fault.  */
111         if (!mm || faulthandler_disabled())
112                 goto no_context;
113 
114 #ifdef CONFIG_ALPHA_LARGE_VMALLOC
115         if (address >= TASK_SIZE)
116                 goto vmalloc_fault;
117 #endif
118         if (user_mode(regs))
119                 flags |= FAULT_FLAG_USER;
120         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
121 retry:
122         mmap_read_lock(mm);
123         vma = find_vma(mm, address);
124         if (!vma)
125                 goto bad_area;
126         if (vma->vm_start <= address)
127                 goto good_area;
128         if (!(vma->vm_flags & VM_GROWSDOWN))
129                 goto bad_area;
130         if (expand_stack(vma, address))
131                 goto bad_area;
132 
133         /* Ok, we have a good vm_area for this memory access, so
134            we can handle it.  */
135  good_area:
136         si_code = SEGV_ACCERR;
137         if (cause < 0) {
138                 if (!(vma->vm_flags & VM_EXEC))
139                         goto bad_area;
140         } else if (!cause) {
141                 /* Allow reads even for write-only mappings */
142                 if (!(vma->vm_flags & (VM_READ | VM_WRITE)))
143                         goto bad_area;
144         } else {
145                 if (!(vma->vm_flags & VM_WRITE))
146                         goto bad_area;
147                 flags |= FAULT_FLAG_WRITE;
148         }
149 
150         /* If for any reason at all we couldn't handle the fault,
151            make sure we exit gracefully rather than endlessly redo
152            the fault.  */
153         fault = handle_mm_fault(vma, address, flags, regs);
154 
155         if (fault_signal_pending(fault, regs))
156                 return;
157 
158         if (unlikely(fault & VM_FAULT_ERROR)) {
159                 if (fault & VM_FAULT_OOM)
160                         goto out_of_memory;
161                 else if (fault & VM_FAULT_SIGSEGV)
162                         goto bad_area;
163                 else if (fault & VM_FAULT_SIGBUS)
164                         goto do_sigbus;
165                 BUG();
166         }
167 
168         if (flags & FAULT_FLAG_ALLOW_RETRY) {
169                 if (fault & VM_FAULT_RETRY) {
170                         flags |= FAULT_FLAG_TRIED;
171 
172                          /* No need to mmap_read_unlock(mm) as we would
173                          * have already released it in __lock_page_or_retry
174                          * in mm/filemap.c.
175                          */
176 
177                         goto retry;
178                 }
179         }
180 
181         mmap_read_unlock(mm);
182 
183         return;
184 
185         /* Something tried to access memory that isn't in our memory map.
186            Fix it, but check if it's kernel or user first.  */
187  bad_area:
188         mmap_read_unlock(mm);
189 
190         if (user_mode(regs))
191                 goto do_sigsegv;
192 
193  no_context:
194         /* Are we prepared to handle this fault as an exception?  */
195         if ((fixup = search_exception_tables(regs->pc)) != 0) {
196                 unsigned long newpc;
197                 newpc = fixup_exception(dpf_reg, fixup, regs->pc);
198                 regs->pc = newpc;
199                 return;
200         }
201 
202         /* Oops. The kernel tried to access some bad page. We'll have to
203            terminate things with extreme prejudice.  */
204         printk(KERN_ALERT "Unable to handle kernel paging request at "
205                "virtual address %016lx\n", address);
206         die_if_kernel("Oops", regs, cause, (unsigned long*)regs - 16);
207         do_exit(SIGKILL);
208 
209         /* We ran out of memory, or some other thing happened to us that
210            made us unable to handle the page fault gracefully.  */
211  out_of_memory:
212         mmap_read_unlock(mm);
213         if (!user_mode(regs))
214                 goto no_context;
215         pagefault_out_of_memory();
216         return;
217 
218  do_sigbus:
219         mmap_read_unlock(mm);
220         /* Send a sigbus, regardless of whether we were in kernel
221            or user mode.  */
222         force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *) address, 0);
223         if (!user_mode(regs))
224                 goto no_context;
225         return;
226 
227  do_sigsegv:
228         force_sig_fault(SIGSEGV, si_code, (void __user *) address, 0);
229         return;
230 
231 #ifdef CONFIG_ALPHA_LARGE_VMALLOC
232  vmalloc_fault:
233         if (user_mode(regs))
234                 goto do_sigsegv;
235         else {
236                 /* Synchronize this task's top level page-table
237                    with the "reference" page table from init.  */
238                 long index = pgd_index(address);
239                 pgd_t *pgd, *pgd_k;
240 
241                 pgd = current->active_mm->pgd + index;
242                 pgd_k = swapper_pg_dir + index;
243                 if (!pgd_present(*pgd) && pgd_present(*pgd_k)) {
244                         pgd_val(*pgd) = pgd_val(*pgd_k);
245                         return;
246                 }
247                 goto no_context;
248         }
249 #endif
250 }
251 

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