| // SPDX-License-Identifier: GPL-2.0-or-later |
| /* |
| * Copyright (C) 2009 Sunplus Core Technology Co., Ltd. |
| * Lennox Wu <lennox.wu@sunplusct.com> |
| * Chen Liqin <liqin.chen@sunplusct.com> |
| * Copyright (C) 2012 Regents of the University of California |
| */ |
| |
| |
| #include <linux/mm.h> |
| #include <linux/kernel.h> |
| #include <linux/interrupt.h> |
| #include <linux/perf_event.h> |
| #include <linux/signal.h> |
| #include <linux/uaccess.h> |
| |
| #include <asm/pgalloc.h> |
| #include <asm/ptrace.h> |
| #include <asm/tlbflush.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_ALLOW_RETRY | FAULT_FLAG_KILLABLE; |
| int code = SEGV_MAPERR; |
| vm_fault_t fault; |
| |
| cause = regs->scause; |
| addr = regs->sbadaddr; |
| |
| 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->sstatus & SR_SPIE)) |
| 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: |
| down_read(&mm->mmap_sem); |
| 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 & VM_FAULT_RETRY) && fatal_signal_pending(tsk)) |
| 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) { |
| /* |
| * Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk |
| * of starvation. |
| */ |
| flags &= ~(FAULT_FLAG_ALLOW_RETRY); |
| flags |= FAULT_FLAG_TRIED; |
| |
| /* |
| * No need to up_read(&mm->mmap_sem) as we would |
| * have already released it in __lock_page_or_retry |
| * in mm/filemap.c. |
| */ |
| goto retry; |
| } |
| } |
| |
| up_read(&mm->mmap_sem); |
| 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: |
| up_read(&mm->mmap_sem); |
| /* 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: |
| up_read(&mm->mmap_sem); |
| if (!user_mode(regs)) |
| goto no_context; |
| pagefault_out_of_memory(); |
| return; |
| |
| do_sigbus: |
| up_read(&mm->mmap_sem); |
| /* 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; |
| } |
| } |