arch/alpha/mm/fault.c

   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 }