arc/mm/fault.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /* Page Fault Handling for ARC (TLB Miss / ProtV)
0003  *
0004  * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
0005  */
0006
0007 #include <linux/signal.h>
0008 #include <linux/interrupt.h>
0009 #include <linux/sched/signal.h>
0010 #include <linux/errno.h>
0011 #include <linux/ptrace.h>
0012 #include <linux/uaccess.h>
0013 #include <linux/kdebug.h>
0014 #include <linux/perf_event.h>
0015 #include <linux/mm_types.h>
0016 #include <asm/mmu.h>
0017
0018 /*
0019  * kernel virtual address is required to implement vmalloc/pkmap/fixmap
0020  * Refer to asm/processor.h for System Memory Map
0021  *
0022  * It simply copies the PMD entry (pointer to 2nd level page table or hugepage)
0023  * from swapper pgdir to task pgdir. The 2nd level table/page is thus shared
0024  */
0025 noinline static int handle_kernel_vaddr_fault(unsigned long address)
0026 {
0027     /*
0028      * Synchronize this task's top level page-table
0029      * with the 'reference' page table.
0030      */
0031     pgd_t *pgd, *pgd_k;
0032     p4d_t *p4d, *p4d_k;
0033     pud_t *pud, *pud_k;
0034     pmd_t *pmd, *pmd_k;
0035
0036     pgd = pgd_offset(current->active_mm, address);
0037     pgd_k = pgd_offset_k(address);
0038
0039     if (pgd_none (*pgd_k))
0040         goto bad_area;
0041     if (!pgd_present(*pgd))
0042         set_pgd(pgd, *pgd_k);
0043
0044     p4d = p4d_offset(pgd, address);
0045     p4d_k = p4d_offset(pgd_k, address);
0046     if (p4d_none(*p4d_k))
0047         goto bad_area;
0048     if (!p4d_present(*p4d))
0049         set_p4d(p4d, *p4d_k);
0050
0051     pud = pud_offset(p4d, address);
0052     pud_k = pud_offset(p4d_k, address);
0053     if (pud_none(*pud_k))
0054         goto bad_area;
0055     if (!pud_present(*pud))
0056         set_pud(pud, *pud_k);
0057
0058     pmd = pmd_offset(pud, address);
0059     pmd_k = pmd_offset(pud_k, address);
0060     if (pmd_none(*pmd_k))
0061         goto bad_area;
0062     if (!pmd_present(*pmd))
0063         set_pmd(pmd, *pmd_k);
0064
0065     /* XXX: create the TLB entry here */
0066     return 0;
0067
0068 bad_area:
0069     return 1;
0070 }
0071
0072 void do_page_fault(unsigned long address, struct pt_regs *regs)
0073 {
0074     struct vm_area_struct *vma = NULL;
0075     struct task_struct *tsk = current;
0076     struct mm_struct *mm = tsk->mm;
0077     int sig, si_code = SEGV_MAPERR;
0078     unsigned int write = 0, exec = 0, mask;
0079     vm_fault_t fault = VM_FAULT_SIGSEGV;    /* handle_mm_fault() output */
0080     unsigned int flags;         /* handle_mm_fault() input */
0081
0082     /*
0083      * NOTE! We MUST NOT take any locks for this case. We may
0084      * be in an interrupt or a critical region, and should
0085      * only copy the information from the master page table,
0086      * nothing more.
0087      */
0088     if (address >= VMALLOC_START && !user_mode(regs)) {
0089         if (unlikely(handle_kernel_vaddr_fault(address)))
0090             goto no_context;
0091         else
0092             return;
0093     }
0094
0095     /*
0096      * If we're in an interrupt or have no user
0097      * context, we must not take the fault..
0098      */
0099     if (faulthandler_disabled() || !mm)
0100         goto no_context;
0101
0102     if (regs->ecr_cause & ECR_C_PROTV_STORE)    /* ST/EX */
0103         write = 1;
0104     else if ((regs->ecr_vec == ECR_V_PROTV) &&
0105              (regs->ecr_cause == ECR_C_PROTV_INST_FETCH))
0106         exec = 1;
0107
0108     flags = FAULT_FLAG_DEFAULT;
0109     if (user_mode(regs))
0110         flags |= FAULT_FLAG_USER;
0111     if (write)
0112         flags |= FAULT_FLAG_WRITE;
0113
0114     perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
0115 retry:
0116     mmap_read_lock(mm);
0117
0118     vma = find_vma(mm, address);
0119     if (!vma)
0120         goto bad_area;
0121     if (unlikely(address < vma->vm_start)) {
0122         if (!(vma->vm_flags & VM_GROWSDOWN) || expand_stack(vma, address))
0123             goto bad_area;
0124     }
0125
0126     /*
0127      * vm_area is good, now check permissions for this memory access
0128      */
0129     mask = VM_READ;
0130     if (write)
0131         mask = VM_WRITE;
0132     if (exec)
0133         mask = VM_EXEC;
0134
0135     if (!(vma->vm_flags & mask)) {
0136         si_code = SEGV_ACCERR;
0137         goto bad_area;
0138     }
0139
0140     fault = handle_mm_fault(vma, address, flags, regs);
0141
0142     /* Quick path to respond to signals */
0143     if (fault_signal_pending(fault, regs)) {
0144         if (!user_mode(regs))
0145             goto no_context;
0146         return;
0147     }
0148
0149     /* The fault is fully completed (including releasing mmap lock) */
0150     if (fault & VM_FAULT_COMPLETED)
0151         return;
0152
0153     /*
0154      * Fault retry nuances, mmap_lock already relinquished by core mm
0155      */
0156     if (unlikely(fault & VM_FAULT_RETRY)) {
0157         flags |= FAULT_FLAG_TRIED;
0158         goto retry;
0159     }
0160
0161 bad_area:
0162     mmap_read_unlock(mm);
0163
0164     /*
0165      * Major/minor page fault accounting
0166      * (in case of retry we only land here once)
0167      */
0168     if (likely(!(fault & VM_FAULT_ERROR)))
0169         /* Normal return path: fault Handled Gracefully */
0170         return;
0171
0172     if (!user_mode(regs))
0173         goto no_context;
0174
0175     if (fault & VM_FAULT_OOM) {
0176         pagefault_out_of_memory();
0177         return;
0178     }
0179
0180     if (fault & VM_FAULT_SIGBUS) {
0181         sig = SIGBUS;
0182         si_code = BUS_ADRERR;
0183     }
0184     else {
0185         sig = SIGSEGV;
0186     }
0187
0188     tsk->thread.fault_address = address;
0189     force_sig_fault(sig, si_code, (void __user *)address);
0190     return;
0191
0192 no_context:
0193     if (fixup_exception(regs))
0194         return;
0195
0196     die("Oops", regs, address);
0197 }