arch/arc/mm/fault.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* Page Fault Handling for ARC (TLB Miss / ProtV)
   3  *
   4  * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
   5  */
   6
   7 #include <linux/signal.h>
   8 #include <linux/interrupt.h>
   9 #include <linux/sched/signal.h>
  10 #include <linux/errno.h>
  11 #include <linux/ptrace.h>
  12 #include <linux/uaccess.h>
  13 #include <linux/kdebug.h>
  14 #include <linux/perf_event.h>
  15 #include <linux/mm_types.h>
  16 #include <asm/pgalloc.h>
  17 #include <asm/mmu.h>
  18
  19 /*
  20  * kernel virtual address is required to implement vmalloc/pkmap/fixmap
  21  * Refer to asm/processor.h for System Memory Map
  22  *
  23  * It simply copies the PMD entry (pointer to 2nd level page table or hugepage)
  24  * from swapper pgdir to task pgdir. The 2nd level table/page is thus shared
  25  */
  26 noinline static int handle_kernel_vaddr_fault(unsigned long address)
  27 {
  28         /*
  29          * Synchronize this task's top level page-table
  30          * with the 'reference' page table.
  31          */
  32         pgd_t *pgd, *pgd_k;
  33         p4d_t *p4d, *p4d_k;
  34         pud_t *pud, *pud_k;
  35         pmd_t *pmd, *pmd_k;
  36
  37         pgd = pgd_offset_fast(current->active_mm, address);
  38         pgd_k = pgd_offset_k(address);
  39
  40         if (!pgd_present(*pgd_k))
  41                 goto bad_area;
  42
  43         p4d = p4d_offset(pgd, address);
  44         p4d_k = p4d_offset(pgd_k, address);
  45         if (!p4d_present(*p4d_k))
  46                 goto bad_area;
  47
  48         pud = pud_offset(p4d, address);
  49         pud_k = pud_offset(p4d_k, address);
  50         if (!pud_present(*pud_k))
  51                 goto bad_area;
  52
  53         pmd = pmd_offset(pud, address);
  54         pmd_k = pmd_offset(pud_k, address);
  55         if (!pmd_present(*pmd_k))
  56                 goto bad_area;
  57
  58         set_pmd(pmd, *pmd_k);
  59
  60         /* XXX: create the TLB entry here */
  61         return 0;
  62
  63 bad_area:
  64         return 1;
  65 }
  66
  67 void do_page_fault(unsigned long address, struct pt_regs *regs)
  68 {
  69         struct vm_area_struct *vma = NULL;
  70         struct task_struct *tsk = current;
  71         struct mm_struct *mm = tsk->mm;
  72         int sig, si_code = SEGV_MAPERR;
  73         unsigned int write = 0, exec = 0, mask;
  74         vm_fault_t fault = VM_FAULT_SIGSEGV;    /* handle_mm_fault() output */
  75         unsigned int flags;                     /* handle_mm_fault() input */
  76
  77         /*
  78          * NOTE! We MUST NOT take any locks for this case. We may
  79          * be in an interrupt or a critical region, and should
  80          * only copy the information from the master page table,
  81          * nothing more.
  82          */
  83         if (address >= VMALLOC_START && !user_mode(regs)) {
  84                 if (unlikely(handle_kernel_vaddr_fault(address)))
  85                         goto no_context;
  86                 else
  87                         return;
  88         }
  89
  90         /*
  91          * If we're in an interrupt or have no user
  92          * context, we must not take the fault..
  93          */
  94         if (faulthandler_disabled() || !mm)
  95                 goto no_context;
  96
  97         if (regs->ecr_cause & ECR_C_PROTV_STORE)        /* ST/EX */
  98                 write = 1;
  99         else if ((regs->ecr_vec == ECR_V_PROTV) &&
 100                  (regs->ecr_cause == ECR_C_PROTV_INST_FETCH))
 101                 exec = 1;
 102
 103         flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 104         if (user_mode(regs))
 105                 flags |= FAULT_FLAG_USER;
 106         if (write)
 107                 flags |= FAULT_FLAG_WRITE;
 108
 109 retry:
 110         down_read(&mm->mmap_sem);
 111
 112         vma = find_vma(mm, address);
 113         if (!vma)
 114                 goto bad_area;
 115         if (unlikely(address < vma->vm_start)) {
 116                 if (!(vma->vm_flags & VM_GROWSDOWN) || expand_stack(vma, address))
 117                         goto bad_area;
 118         }
 119
 120         /*
 121          * vm_area is good, now check permissions for this memory access
 122          */
 123         mask = VM_READ;
 124         if (write)
 125                 mask = VM_WRITE;
 126         if (exec)
 127                 mask = VM_EXEC;
 128
 129         if (!(vma->vm_flags & mask)) {
 130                 si_code = SEGV_ACCERR;
 131                 goto bad_area;
 132         }
 133
 134         fault = handle_mm_fault(vma, address, flags);
 135
 136         /*
 137          * Fault retry nuances
 138          */
 139         if (unlikely(fault & VM_FAULT_RETRY)) {
 140
 141                 /*
 142                  * If fault needs to be retried, handle any pending signals
 143                  * first (by returning to user mode).
 144                  * mmap_sem already relinquished by core mm for RETRY case
 145                  */
 146                 if (fatal_signal_pending(current)) {
 147                         if (!user_mode(regs))
 148                                 goto no_context;
 149                         return;
 150                 }
 151                 /*
 152                  * retry state machine
 153                  */
 154                 if (flags & FAULT_FLAG_ALLOW_RETRY) {
 155                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
 156                         flags |= FAULT_FLAG_TRIED;
 157                         goto retry;
 158                 }
 159         }
 160
 161 bad_area:
 162         up_read(&mm->mmap_sem);
 163
 164         /*
 165          * Major/minor page fault accounting
 166          * (in case of retry we only land here once)
 167          */
 168         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 169
 170         if (likely(!(fault & VM_FAULT_ERROR))) {
 171                 if (fault & VM_FAULT_MAJOR) {
 172                         tsk->maj_flt++;
 173                         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
 174                                       regs, address);
 175                 } else {
 176                         tsk->min_flt++;
 177                         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
 178                                       regs, address);
 179                 }
 180
 181                 /* Normal return path: fault Handled Gracefully */
 182                 return;
 183         }
 184
 185         if (!user_mode(regs))
 186                 goto no_context;
 187
 188         if (fault & VM_FAULT_OOM) {
 189                 pagefault_out_of_memory();
 190                 return;
 191         }
 192
 193         if (fault & VM_FAULT_SIGBUS) {
 194                 sig = SIGBUS;
 195                 si_code = BUS_ADRERR;
 196         }
 197         else {
 198                 sig = SIGSEGV;
 199         }
 200
 201         tsk->thread.fault_address = address;
 202         force_sig_fault(sig, si_code, (void __user *)address);
 203         return;
 204
 205 no_context:
 206         if (fixup_exception(regs))
 207                 return;
 208
 209         die("Oops", regs, address);
 210 }