// SPDX-License-Identifier: GPL-2.0-or-later /* * Copyright (C) 2009 Sunplus Core Technology Co., Ltd. * Lennox Wu * Chen Liqin * Copyright (C) 2012 Regents of the University of California */ #include #include #include #include #include #include #include #include #include #include "../kernel/head.h" /* * This routine handles page faults. It determines the address and the * problem, and then passes it off to one of the appropriate routines. */ asmlinkage void do_page_fault(struct pt_regs *regs) { struct task_struct *tsk; struct vm_area_struct *vma; struct mm_struct *mm; unsigned long addr, cause; unsigned int flags = FAULT_FLAG_DEFAULT; int code = SEGV_MAPERR; vm_fault_t fault; cause = regs->cause; addr = regs->badaddr; tsk = current; mm = tsk->mm; /* * Fault-in kernel-space virtual memory on-demand. * The 'reference' page table is init_mm.pgd. * * NOTE! We MUST NOT take any locks for this case. We may * be in an interrupt or a critical region, and should * only copy the information from the master page table, * nothing more. */ if (unlikely((addr >= VMALLOC_START) && (addr <= VMALLOC_END))) goto vmalloc_fault; /* Enable interrupts if they were enabled in the parent context. */ if (likely(regs->status & SR_PIE)) local_irq_enable(); /* * If we're in an interrupt, have no user context, or are running * in an atomic region, then we must not take the fault. */ if (unlikely(faulthandler_disabled() || !mm)) goto no_context; if (user_mode(regs)) flags |= FAULT_FLAG_USER; perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr); retry: mmap_read_lock(mm); vma = find_vma(mm, addr); if (unlikely(!vma)) goto bad_area; if (likely(vma->vm_start <= addr)) goto good_area; if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) goto bad_area; if (unlikely(expand_stack(vma, addr))) goto bad_area; /* * Ok, we have a good vm_area for this memory access, so * we can handle it. */ good_area: code = SEGV_ACCERR; switch (cause) { case EXC_INST_PAGE_FAULT: if (!(vma->vm_flags & VM_EXEC)) goto bad_area; break; case EXC_LOAD_PAGE_FAULT: if (!(vma->vm_flags & VM_READ)) goto bad_area; break; case EXC_STORE_PAGE_FAULT: if (!(vma->vm_flags & VM_WRITE)) goto bad_area; flags |= FAULT_FLAG_WRITE; break; default: panic("%s: unhandled cause %lu", __func__, cause); } /* * If for any reason at all we could not handle the fault, * make sure we exit gracefully rather than endlessly redo * the fault. */ fault = handle_mm_fault(vma, addr, flags); /* * If we need to retry but a fatal signal is pending, handle the * signal first. We do not need to release the mmap_sem because it * would already be released in __lock_page_or_retry in mm/filemap.c. */ if (fault_signal_pending(fault, regs)) return; if (unlikely(fault & VM_FAULT_ERROR)) { if (fault & VM_FAULT_OOM) goto out_of_memory; else if (fault & VM_FAULT_SIGBUS) goto do_sigbus; BUG(); } /* * Major/minor page fault accounting is only done on the * initial attempt. If we go through a retry, it is extremely * likely that the page will be found in page cache at that point. */ if (flags & FAULT_FLAG_ALLOW_RETRY) { if (fault & VM_FAULT_MAJOR) { tsk->maj_flt++; perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, addr); } else { tsk->min_flt++; perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, addr); } if (fault & VM_FAULT_RETRY) { flags |= FAULT_FLAG_TRIED; /* * No need to mmap_read_unlock(mm) as we would * have already released it in __lock_page_or_retry * in mm/filemap.c. */ goto retry; } } mmap_read_unlock(mm); return; /* * Something tried to access memory that isn't in our memory map. * Fix it, but check if it's kernel or user first. */ bad_area: mmap_read_unlock(mm); /* User mode accesses just cause a SIGSEGV */ if (user_mode(regs)) { do_trap(regs, SIGSEGV, code, addr); return; } no_context: /* Are we prepared to handle this kernel fault? */ if (fixup_exception(regs)) return; /* * Oops. The kernel tried to access some bad page. We'll have to * terminate things with extreme prejudice. */ bust_spinlocks(1); pr_alert("Unable to handle kernel %s at virtual address " REG_FMT "\n", (addr < PAGE_SIZE) ? "NULL pointer dereference" : "paging request", addr); die(regs, "Oops"); do_exit(SIGKILL); /* * We ran out of memory, call the OOM killer, and return the userspace * (which will retry the fault, or kill us if we got oom-killed). */ out_of_memory: mmap_read_unlock(mm); if (!user_mode(regs)) goto no_context; pagefault_out_of_memory(); return; do_sigbus: mmap_read_unlock(mm); /* Kernel mode? Handle exceptions or die */ if (!user_mode(regs)) goto no_context; do_trap(regs, SIGBUS, BUS_ADRERR, addr); return; vmalloc_fault: { pgd_t *pgd, *pgd_k; pud_t *pud, *pud_k; p4d_t *p4d, *p4d_k; pmd_t *pmd, *pmd_k; pte_t *pte_k; int index; /* User mode accesses just cause a SIGSEGV */ if (user_mode(regs)) return do_trap(regs, SIGSEGV, code, addr); /* * Synchronize this task's top level page-table * with the 'reference' page table. * * Do _not_ use "tsk->active_mm->pgd" here. * We might be inside an interrupt in the middle * of a task switch. */ index = pgd_index(addr); pgd = (pgd_t *)pfn_to_virt(csr_read(CSR_SATP)) + index; pgd_k = init_mm.pgd + index; if (!pgd_present(*pgd_k)) goto no_context; set_pgd(pgd, *pgd_k); p4d = p4d_offset(pgd, addr); p4d_k = p4d_offset(pgd_k, addr); if (!p4d_present(*p4d_k)) goto no_context; pud = pud_offset(p4d, addr); pud_k = pud_offset(p4d_k, addr); if (!pud_present(*pud_k)) goto no_context; /* * Since the vmalloc area is global, it is unnecessary * to copy individual PTEs */ pmd = pmd_offset(pud, addr); pmd_k = pmd_offset(pud_k, addr); if (!pmd_present(*pmd_k)) goto no_context; set_pmd(pmd, *pmd_k); /* * Make sure the actual PTE exists as well to * catch kernel vmalloc-area accesses to non-mapped * addresses. If we don't do this, this will just * silently loop forever. */ pte_k = pte_offset_kernel(pmd_k, addr); if (!pte_present(*pte_k)) goto no_context; /* * The kernel assumes that TLBs don't cache invalid * entries, but in RISC-V, SFENCE.VMA specifies an * ordering constraint, not a cache flush; it is * necessary even after writing invalid entries. */ local_flush_tlb_page(addr); return; } }