root/arch/alpha/mm/fault.c

DEFINITIONS

1. __load_new_mm_context
2. do_page_fault

   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)+10 : (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 si_code = SEGV_MAPERR;
  91         vm_fault_t fault;
  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         force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *) address, 0);
 225         if (!user_mode(regs))
 226                 goto no_context;
 227         return;
 228 
 229  do_sigsegv:
 230         force_sig_fault(SIGSEGV, si_code, (void __user *) address, 0);
 231         return;
 232 
 233 #ifdef CONFIG_ALPHA_LARGE_VMALLOC
 234  vmalloc_fault:
 235         if (user_mode(regs))
 236                 goto do_sigsegv;
 237         else {
 238                 /* Synchronize this task's top level page-table
 239                    with the "reference" page table from init.  */
 240                 long index = pgd_index(address);
 241                 pgd_t *pgd, *pgd_k;
 242 
 243                 pgd = current->active_mm->pgd + index;
 244                 pgd_k = swapper_pg_dir + index;
 245                 if (!pgd_present(*pgd) && pgd_present(*pgd_k)) {
 246                         pgd_val(*pgd) = pgd_val(*pgd_k);
 247                         return;
 248                 }
 249                 goto no_context;
 250         }
 251 #endif
 252 }