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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 
 29 extern void die_if_kernel(char *,struct pt_regs *,long, unsigned long *);
 30 
 31 
 32 /*
 33  * Force a new ASN for a task.
 34  */
 35 
 36 #ifndef CONFIG_SMP
 37 unsigned long last_asn = ASN_FIRST_VERSION;
 38 #endif
 39 
 40 void
 41 __load_new_mm_context(struct mm_struct *next_mm)
 42 {
 43         unsigned long mmc;
 44         struct pcb_struct *pcb;
 45 
 46         mmc = __get_new_mm_context(next_mm, smp_processor_id());
 47         next_mm->context[smp_processor_id()] = mmc;
 48 
 49         pcb = &current_thread_info()->pcb;
 50         pcb->asn = mmc & HARDWARE_ASN_MASK;
 51         pcb->ptbr = ((unsigned long) next_mm->pgd - IDENT_ADDR) >> PAGE_SHIFT;
 52 
 53         __reload_thread(pcb);
 54 }
 55 
 56 
 57 /*
 58  * This routine handles page faults.  It determines the address,
 59  * and the problem, and then passes it off to handle_mm_fault().
 60  *
 61  * mmcsr:
 62  *      0 = translation not valid
 63  *      1 = access violation
 64  *      2 = fault-on-read
 65  *      3 = fault-on-execute
 66  *      4 = fault-on-write
 67  *
 68  * cause:
 69  *      -1 = instruction fetch
 70  *      0 = load
 71  *      1 = store
 72  *
 73  * Registers $9 through $15 are saved in a block just prior to `regs' and
 74  * are saved and restored around the call to allow exception code to
 75  * modify them.
 76  */
 77 
 78 /* Macro for exception fixup code to access integer registers.  */
 79 #define dpf_reg(r)                                                      \
 80         (((unsigned long *)regs)[(r) <= 8 ? (r) : (r) <= 15 ? (r)-16 :  \
 81                                  (r) <= 18 ? (r)+8 : (r)-10])
 82 
 83 asmlinkage void
 84 do_page_fault(unsigned long address, unsigned long mmcsr,
 85               long cause, struct pt_regs *regs)
 86 {
 87         struct vm_area_struct * vma;
 88         struct mm_struct *mm = current->mm;
 89         const struct exception_table_entry *fixup;
 90         int fault, si_code = SEGV_MAPERR;
 91         siginfo_t info;
 92         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 93 
 94         /* As of EV6, a load into $31/$f31 is a prefetch, and never faults
 95            (or is suppressed by the PALcode).  Support that for older CPUs
 96            by ignoring such an instruction.  */
 97         if (cause == 0) {
 98                 unsigned int insn;
 99                 __get_user(insn, (unsigned int __user *)regs->pc);
100                 if ((insn >> 21 & 0x1f) == 0x1f &&
101                     /* ldq ldl ldt lds ldg ldf ldwu ldbu */
102                     (1ul << (insn >> 26) & 0x30f00001400ul)) {
103                         regs->pc += 4;
104                         return;
105                 }
106         }
107 
108         /* If we're in an interrupt context, or have no user context,
109            we must not take the fault.  */
110         if (!mm || faulthandler_disabled())
111                 goto no_context;
112 
113 #ifdef CONFIG_ALPHA_LARGE_VMALLOC
114         if (address >= TASK_SIZE)
115                 goto vmalloc_fault;
116 #endif
117         if (user_mode(regs))
118                 flags |= FAULT_FLAG_USER;
119 retry:
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                 flags |= FAULT_FLAG_WRITE;
146         }
147 
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(vma, address, flags);
152 
153         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
154                 return;
155 
156         if (unlikely(fault & VM_FAULT_ERROR)) {
157                 if (fault & VM_FAULT_OOM)
158                         goto out_of_memory;
159                 else if (fault & VM_FAULT_SIGSEGV)
160                         goto bad_area;
161                 else if (fault & VM_FAULT_SIGBUS)
162                         goto do_sigbus;
163                 BUG();
164         }
165 
166         if (flags & FAULT_FLAG_ALLOW_RETRY) {
167                 if (fault & VM_FAULT_MAJOR)
168                         current->maj_flt++;
169                 else
170                         current->min_flt++;
171                 if (fault & VM_FAULT_RETRY) {
172                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
173 
174                          /* No need to up_read(&mm->mmap_sem) as we would
175                          * have already released it in __lock_page_or_retry
176                          * in mm/filemap.c.
177                          */
178 
179                         goto retry;
180                 }
181         }
182 
183         up_read(&mm->mmap_sem);
184 
185         return;
186 
187         /* Something tried to access memory that isn't in our memory map.
188            Fix it, but check if it's kernel or user first.  */
189  bad_area:
190         up_read(&mm->mmap_sem);
191 
192         if (user_mode(regs))
193                 goto do_sigsegv;
194 
195  no_context:
196         /* Are we prepared to handle this fault as an exception?  */
197         if ((fixup = search_exception_tables(regs->pc)) != 0) {
198                 unsigned long newpc;
199                 newpc = fixup_exception(dpf_reg, fixup, regs->pc);
200                 regs->pc = newpc;
201                 return;
202         }
203 
204         /* Oops. The kernel tried to access some bad page. We'll have to
205            terminate things with extreme prejudice.  */
206         printk(KERN_ALERT "Unable to handle kernel paging request at "
207                "virtual address %016lx\n", address);
208         die_if_kernel("Oops", regs, cause, (unsigned long*)regs - 16);
209         do_exit(SIGKILL);
210 
211         /* We ran out of memory, or some other thing happened to us that
212            made us unable to handle the page fault gracefully.  */
213  out_of_memory:
214         up_read(&mm->mmap_sem);
215         if (!user_mode(regs))
216                 goto no_context;
217         pagefault_out_of_memory();
218         return;
219 
220  do_sigbus:
221         up_read(&mm->mmap_sem);
222         /* Send a sigbus, regardless of whether we were in kernel
223            or user mode.  */
224         info.si_signo = SIGBUS;
225         info.si_errno = 0;
226         info.si_code = BUS_ADRERR;
227         info.si_addr = (void __user *) address;
228         force_sig_info(SIGBUS, &info, current);
229         if (!user_mode(regs))
230                 goto no_context;
231         return;
232 
233  do_sigsegv:
234         info.si_signo = SIGSEGV;
235         info.si_errno = 0;
236         info.si_code = si_code;
237         info.si_addr = (void __user *) address;
238         force_sig_info(SIGSEGV, &info, current);
239         return;
240 
241 #ifdef CONFIG_ALPHA_LARGE_VMALLOC
242  vmalloc_fault:
243         if (user_mode(regs))
244                 goto do_sigsegv;
245         else {
246                 /* Synchronize this task's top level page-table
247                    with the "reference" page table from init.  */
248                 long index = pgd_index(address);
249                 pgd_t *pgd, *pgd_k;
250 
251                 pgd = current->active_mm->pgd + index;
252                 pgd_k = swapper_pg_dir + index;
253                 if (!pgd_present(*pgd) && pgd_present(*pgd_k)) {
254                         pgd_val(*pgd) = pgd_val(*pgd_k);
255                         return;
256                 }
257                 goto no_context;
258         }
259 #endif
260 }
261 

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