arch/riscv/mm/fault.c

   1 /*
   2  * Copyright (C) 2009 Sunplus Core Technology Co., Ltd.
   3  *  Lennox Wu <lennox.wu@sunplusct.com>
   4  *  Chen Liqin <liqin.chen@sunplusct.com>
   5  * Copyright (C) 2012 Regents of the University of California
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, see the file COPYING, or write
  19  * to the Free Software Foundation, Inc.,
  20  */
  21
  22
  23 #include <linux/mm.h>
  24 #include <linux/kernel.h>
  25 #include <linux/interrupt.h>
  26 #include <linux/perf_event.h>
  27 #include <linux/signal.h>
  28 #include <linux/uaccess.h>
  29
  30 #include <asm/pgalloc.h>
  31 #include <asm/ptrace.h>
  32
  33 /*
  34  * This routine handles page faults.  It determines the address and the
  35  * problem, and then passes it off to one of the appropriate routines.
  36  */
  37 asmlinkage void do_page_fault(struct pt_regs *regs)
  38 {
  39         struct task_struct *tsk;
  40         struct vm_area_struct *vma;
  41         struct mm_struct *mm;
  42         unsigned long addr, cause;
  43         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
  44         int code = SEGV_MAPERR;
  45         vm_fault_t fault;
  46
  47         cause = regs->scause;
  48         addr = regs->sbadaddr;
  49
  50         tsk = current;
  51         mm = tsk->mm;
  52
  53         /*
  54          * Fault-in kernel-space virtual memory on-demand.
  55          * The 'reference' page table is init_mm.pgd.
  56          *
  57          * NOTE! We MUST NOT take any locks for this case. We may
  58          * be in an interrupt or a critical region, and should
  59          * only copy the information from the master page table,
  60          * nothing more.
  61          */
  62         if (unlikely((addr >= VMALLOC_START) && (addr <= VMALLOC_END)))
  63                 goto vmalloc_fault;
  64
  65         /* Enable interrupts if they were enabled in the parent context. */
  66         if (likely(regs->sstatus & SR_SPIE))
  67                 local_irq_enable();
  68
  69         /*
  70          * If we're in an interrupt, have no user context, or are running
  71          * in an atomic region, then we must not take the fault.
  72          */
  73         if (unlikely(faulthandler_disabled() || !mm))
  74                 goto no_context;
  75
  76         if (user_mode(regs))
  77                 flags |= FAULT_FLAG_USER;
  78
  79         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
  80
  81 retry:
  82         down_read(&mm->mmap_sem);
  83         vma = find_vma(mm, addr);
  84         if (unlikely(!vma))
  85                 goto bad_area;
  86         if (likely(vma->vm_start <= addr))
  87                 goto good_area;
  88         if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)))
  89                 goto bad_area;
  90         if (unlikely(expand_stack(vma, addr)))
  91                 goto bad_area;
  92
  93         /*
  94          * Ok, we have a good vm_area for this memory access, so
  95          * we can handle it.
  96          */
  97 good_area:
  98         code = SEGV_ACCERR;
  99
 100         switch (cause) {
 101         case EXC_INST_PAGE_FAULT:
 102                 if (!(vma->vm_flags & VM_EXEC))
 103                         goto bad_area;
 104                 break;
 105         case EXC_LOAD_PAGE_FAULT:
 106                 if (!(vma->vm_flags & VM_READ))
 107                         goto bad_area;
 108                 break;
 109         case EXC_STORE_PAGE_FAULT:
 110                 if (!(vma->vm_flags & VM_WRITE))
 111                         goto bad_area;
 112                 flags |= FAULT_FLAG_WRITE;
 113                 break;
 114         default:
 115                 panic("%s: unhandled cause %lu", __func__, cause);
 116         }
 117
 118         /*
 119          * If for any reason at all we could not handle the fault,
 120          * make sure we exit gracefully rather than endlessly redo
 121          * the fault.
 122          */
 123         fault = handle_mm_fault(vma, addr, flags);
 124
 125         /*
 126          * If we need to retry but a fatal signal is pending, handle the
 127          * signal first. We do not need to release the mmap_sem because it
 128          * would already be released in __lock_page_or_retry in mm/filemap.c.
 129          */
 130         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(tsk))
 131                 return;
 132
 133         if (unlikely(fault & VM_FAULT_ERROR)) {
 134                 if (fault & VM_FAULT_OOM)
 135                         goto out_of_memory;
 136                 else if (fault & VM_FAULT_SIGBUS)
 137                         goto do_sigbus;
 138                 BUG();
 139         }
 140
 141         /*
 142          * Major/minor page fault accounting is only done on the
 143          * initial attempt. If we go through a retry, it is extremely
 144          * likely that the page will be found in page cache at that point.
 145          */
 146         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 147                 if (fault & VM_FAULT_MAJOR) {
 148                         tsk->maj_flt++;
 149                         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ,
 150                                       1, regs, addr);
 151                 } else {
 152                         tsk->min_flt++;
 153                         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN,
 154                                       1, regs, addr);
 155                 }
 156                 if (fault & VM_FAULT_RETRY) {
 157                         /*
 158                          * Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
 159                          * of starvation.
 160                          */
 161                         flags &= ~(FAULT_FLAG_ALLOW_RETRY);
 162                         flags |= FAULT_FLAG_TRIED;
 163
 164                         /*
 165                          * No need to up_read(&mm->mmap_sem) as we would
 166                          * have already released it in __lock_page_or_retry
 167                          * in mm/filemap.c.
 168                          */
 169                         goto retry;
 170                 }
 171         }
 172
 173         up_read(&mm->mmap_sem);
 174         return;
 175
 176         /*
 177          * Something tried to access memory that isn't in our memory map.
 178          * Fix it, but check if it's kernel or user first.
 179          */
 180 bad_area:
 181         up_read(&mm->mmap_sem);
 182         /* User mode accesses just cause a SIGSEGV */
 183         if (user_mode(regs)) {
 184                 do_trap(regs, SIGSEGV, code, addr, tsk);
 185                 return;
 186         }
 187
 188 no_context:
 189         /* Are we prepared to handle this kernel fault? */
 190         if (fixup_exception(regs))
 191                 return;
 192
 193         /*
 194          * Oops. The kernel tried to access some bad page. We'll have to
 195          * terminate things with extreme prejudice.
 196          */
 197         bust_spinlocks(1);
 198         pr_alert("Unable to handle kernel %s at virtual address " REG_FMT "\n",
 199                 (addr < PAGE_SIZE) ? "NULL pointer dereference" :
 200                 "paging request", addr);
 201         die(regs, "Oops");
 202         do_exit(SIGKILL);
 203
 204         /*
 205          * We ran out of memory, call the OOM killer, and return the userspace
 206          * (which will retry the fault, or kill us if we got oom-killed).
 207          */
 208 out_of_memory:
 209         up_read(&mm->mmap_sem);
 210         if (!user_mode(regs))
 211                 goto no_context;
 212         pagefault_out_of_memory();
 213         return;
 214
 215 do_sigbus:
 216         up_read(&mm->mmap_sem);
 217         /* Kernel mode? Handle exceptions or die */
 218         if (!user_mode(regs))
 219                 goto no_context;
 220         do_trap(regs, SIGBUS, BUS_ADRERR, addr, tsk);
 221         return;
 222
 223 vmalloc_fault:
 224         {
 225                 pgd_t *pgd, *pgd_k;
 226                 pud_t *pud, *pud_k;
 227                 p4d_t *p4d, *p4d_k;
 228                 pmd_t *pmd, *pmd_k;
 229                 pte_t *pte_k;
 230                 int index;
 231
 232                 /* User mode accesses just cause a SIGSEGV */
 233                 if (user_mode(regs))
 234                         return do_trap(regs, SIGSEGV, code, addr, tsk);
 235
 236                 /*
 237                  * Synchronize this task's top level page-table
 238                  * with the 'reference' page table.
 239                  *
 240                  * Do _not_ use "tsk->active_mm->pgd" here.
 241                  * We might be inside an interrupt in the middle
 242                  * of a task switch.
 243                  */
 244                 index = pgd_index(addr);
 245                 pgd = (pgd_t *)pfn_to_virt(csr_read(CSR_SATP)) + index;
 246                 pgd_k = init_mm.pgd + index;
 247
 248                 if (!pgd_present(*pgd_k))
 249                         goto no_context;
 250                 set_pgd(pgd, *pgd_k);
 251
 252                 p4d = p4d_offset(pgd, addr);
 253                 p4d_k = p4d_offset(pgd_k, addr);
 254                 if (!p4d_present(*p4d_k))
 255                         goto no_context;
 256
 257                 pud = pud_offset(p4d, addr);
 258                 pud_k = pud_offset(p4d_k, addr);
 259                 if (!pud_present(*pud_k))
 260                         goto no_context;
 261
 262                 /*
 263                  * Since the vmalloc area is global, it is unnecessary
 264                  * to copy individual PTEs
 265                  */
 266                 pmd = pmd_offset(pud, addr);
 267                 pmd_k = pmd_offset(pud_k, addr);
 268                 if (!pmd_present(*pmd_k))
 269                         goto no_context;
 270                 set_pmd(pmd, *pmd_k);
 271
 272                 /*
 273                  * Make sure the actual PTE exists as well to
 274                  * catch kernel vmalloc-area accesses to non-mapped
 275                  * addresses. If we don't do this, this will just
 276                  * silently loop forever.
 277                  */
 278                 pte_k = pte_offset_kernel(pmd_k, addr);
 279                 if (!pte_present(*pte_k))
 280                         goto no_context;
 281                 return;
 282         }
 283 }