root/arch/csky/mm/fault.c

DEFINITIONS

1. fixup_exception
2. do_page_fault

   1 // SPDX-License-Identifier: GPL-2.0
   2 // Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
   3 
   4 #include <linux/signal.h>
   5 #include <linux/module.h>
   6 #include <linux/sched.h>
   7 #include <linux/interrupt.h>
   8 #include <linux/kernel.h>
   9 #include <linux/errno.h>
  10 #include <linux/string.h>
  11 #include <linux/types.h>
  12 #include <linux/ptrace.h>
  13 #include <linux/mman.h>
  14 #include <linux/mm.h>
  15 #include <linux/smp.h>
  16 #include <linux/version.h>
  17 #include <linux/vt_kern.h>
  18 #include <linux/extable.h>
  19 #include <linux/uaccess.h>
  20 #include <linux/perf_event.h>
  21 
  22 #include <asm/hardirq.h>
  23 #include <asm/mmu_context.h>
  24 #include <asm/traps.h>
  25 #include <asm/page.h>
  26 
  27 int fixup_exception(struct pt_regs *regs)
  28 {
  29         const struct exception_table_entry *fixup;
  30 
  31         fixup = search_exception_tables(instruction_pointer(regs));
  32         if (fixup) {
  33                 regs->pc = fixup->nextinsn;
  34 
  35                 return 1;
  36         }
  37 
  38         return 0;
  39 }
  40 
  41 /*
  42  * This routine handles page faults. It determines the address,
  43  * and the problem, and then passes it off to one of the appropriate
  44  * routines.
  45  */
  46 asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long write,
  47                               unsigned long mmu_meh)
  48 {
  49         struct vm_area_struct *vma = NULL;
  50         struct task_struct *tsk = current;
  51         struct mm_struct *mm = tsk->mm;
  52         int si_code;
  53         int fault;
  54         unsigned long address = mmu_meh & PAGE_MASK;
  55 
  56         si_code = SEGV_MAPERR;
  57 
  58 #ifndef CONFIG_CPU_HAS_TLBI
  59         /*
  60          * We fault-in kernel-space virtual memory on-demand. The
  61          * 'reference' page table is init_mm.pgd.
  62          *
  63          * NOTE! We MUST NOT take any locks for this case. We may
  64          * be in an interrupt or a critical region, and should
  65          * only copy the information from the master page table,
  66          * nothing more.
  67          */
  68         if (unlikely(address >= VMALLOC_START) &&
  69             unlikely(address <= VMALLOC_END)) {
  70                 /*
  71                  * Synchronize this task's top level page-table
  72                  * with the 'reference' page table.
  73                  *
  74                  * Do _not_ use "tsk" here. We might be inside
  75                  * an interrupt in the middle of a task switch..
  76                  */
  77                 int offset = __pgd_offset(address);
  78                 pgd_t *pgd, *pgd_k;
  79                 pud_t *pud, *pud_k;
  80                 pmd_t *pmd, *pmd_k;
  81                 pte_t *pte_k;
  82 
  83                 unsigned long pgd_base;
  84 
  85                 pgd_base = (unsigned long)__va(get_pgd());
  86                 pgd = (pgd_t *)pgd_base + offset;
  87                 pgd_k = init_mm.pgd + offset;
  88 
  89                 if (!pgd_present(*pgd_k))
  90                         goto no_context;
  91                 set_pgd(pgd, *pgd_k);
  92 
  93                 pud = (pud_t *)pgd;
  94                 pud_k = (pud_t *)pgd_k;
  95                 if (!pud_present(*pud_k))
  96                         goto no_context;
  97 
  98                 pmd = pmd_offset(pud, address);
  99                 pmd_k = pmd_offset(pud_k, address);
 100                 if (!pmd_present(*pmd_k))
 101                         goto no_context;
 102                 set_pmd(pmd, *pmd_k);
 103 
 104                 pte_k = pte_offset_kernel(pmd_k, address);
 105                 if (!pte_present(*pte_k))
 106                         goto no_context;
 107                 return;
 108         }
 109 #endif
 110 
 111         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 112         /*
 113          * If we're in an interrupt or have no user
 114          * context, we must not take the fault..
 115          */
 116         if (in_atomic() || !mm)
 117                 goto bad_area_nosemaphore;
 118 
 119         down_read(&mm->mmap_sem);
 120         vma = find_vma(mm, address);
 121         if (!vma)
 122                 goto bad_area;
 123         if (vma->vm_start <= address)
 124                 goto good_area;
 125         if (!(vma->vm_flags & VM_GROWSDOWN))
 126                 goto bad_area;
 127         if (expand_stack(vma, address))
 128                 goto bad_area;
 129         /*
 130          * Ok, we have a good vm_area for this memory access, so
 131          * we can handle it..
 132          */
 133 good_area:
 134         si_code = SEGV_ACCERR;
 135 
 136         if (write) {
 137                 if (!(vma->vm_flags & VM_WRITE))
 138                         goto bad_area;
 139         } else {
 140                 if (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)))
 141                         goto bad_area;
 142         }
 143 
 144         /*
 145          * If for any reason at all we couldn't handle the fault,
 146          * make sure we exit gracefully rather than endlessly redo
 147          * the fault.
 148          */
 149         fault = handle_mm_fault(vma, address, write ? FAULT_FLAG_WRITE : 0);
 150         if (unlikely(fault & VM_FAULT_ERROR)) {
 151                 if (fault & VM_FAULT_OOM)
 152                         goto out_of_memory;
 153                 else if (fault & VM_FAULT_SIGBUS)
 154                         goto do_sigbus;
 155                 else if (fault & VM_FAULT_SIGSEGV)
 156                         goto bad_area;
 157                 BUG();
 158         }
 159         if (fault & VM_FAULT_MAJOR) {
 160                 tsk->maj_flt++;
 161                 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs,
 162                               address);
 163         } else {
 164                 tsk->min_flt++;
 165                 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs,
 166                               address);
 167         }
 168 
 169         up_read(&mm->mmap_sem);
 170         return;
 171 
 172         /*
 173          * Something tried to access memory that isn't in our memory map..
 174          * Fix it, but check if it's kernel or user first..
 175          */
 176 bad_area:
 177         up_read(&mm->mmap_sem);
 178 
 179 bad_area_nosemaphore:
 180         /* User mode accesses just cause a SIGSEGV */
 181         if (user_mode(regs)) {
 182                 tsk->thread.trap_no = (regs->sr >> 16) & 0xff;
 183                 force_sig_fault(SIGSEGV, si_code, (void __user *)address);
 184                 return;
 185         }
 186 
 187 no_context:
 188         tsk->thread.trap_no = (regs->sr >> 16) & 0xff;
 189 
 190         /* Are we prepared to handle this kernel fault? */
 191         if (fixup_exception(regs))
 192                 return;
 193 
 194         /*
 195          * Oops. The kernel tried to access some bad page. We'll have to
 196          * terminate things with extreme prejudice.
 197          */
 198         bust_spinlocks(1);
 199         pr_alert("Unable to handle kernel paging request at virtual "
 200                  "address 0x%08lx, pc: 0x%08lx\n", address, regs->pc);
 201         die_if_kernel("Oops", regs, write);
 202 
 203 out_of_memory:
 204         tsk->thread.trap_no = (regs->sr >> 16) & 0xff;
 205 
 206         /*
 207          * We ran out of memory, call the OOM killer, and return the userspace
 208          * (which will retry the fault, or kill us if we got oom-killed).
 209          */
 210         pagefault_out_of_memory();
 211         return;
 212 
 213 do_sigbus:
 214         tsk->thread.trap_no = (regs->sr >> 16) & 0xff;
 215 
 216         up_read(&mm->mmap_sem);
 217 
 218         /* Kernel mode? Handle exceptions or die */
 219         if (!user_mode(regs))
 220                 goto no_context;
 221 
 222         force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
 223 }