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