| // 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 <linux/kprobes.h> |
| #include <linux/kfence.h> |
| #include <linux/entry-common.h> |
| |
| #include <asm/ptrace.h> |
| #include <asm/tlbflush.h> |
| |
| #include "../kernel/head.h" |
| |
| static void die_kernel_fault(const char *msg, unsigned long addr, |
| struct pt_regs *regs) |
| { |
| bust_spinlocks(1); |
| |
| pr_alert("Unable to handle kernel %s at virtual address " REG_FMT "\n", msg, |
| addr); |
| |
| bust_spinlocks(0); |
| die(regs, "Oops"); |
| make_task_dead(SIGKILL); |
| } |
| |
| static inline void no_context(struct pt_regs *regs, unsigned long addr) |
| { |
| const char *msg; |
| |
| /* 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. |
| */ |
| if (addr < PAGE_SIZE) |
| msg = "NULL pointer dereference"; |
| else { |
| if (kfence_handle_page_fault(addr, regs->cause == EXC_STORE_PAGE_FAULT, regs)) |
| return; |
| |
| msg = "paging request"; |
| } |
| |
| die_kernel_fault(msg, addr, regs); |
| } |
| |
| static inline void mm_fault_error(struct pt_regs *regs, unsigned long addr, vm_fault_t fault) |
| { |
| if (fault & VM_FAULT_OOM) { |
| /* |
| * 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). |
| */ |
| if (!user_mode(regs)) { |
| no_context(regs, addr); |
| return; |
| } |
| pagefault_out_of_memory(); |
| return; |
| } else if (fault & VM_FAULT_SIGBUS) { |
| /* Kernel mode? Handle exceptions or die */ |
| if (!user_mode(regs)) { |
| no_context(regs, addr); |
| return; |
| } |
| do_trap(regs, SIGBUS, BUS_ADRERR, addr); |
| return; |
| } |
| BUG(); |
| } |
| |
| static inline void |
| bad_area_nosemaphore(struct pt_regs *regs, int code, unsigned long addr) |
| { |
| /* |
| * Something tried to access memory that isn't in our memory map. |
| * Fix it, but check if it's kernel or user first. |
| */ |
| /* User mode accesses just cause a SIGSEGV */ |
| if (user_mode(regs)) { |
| do_trap(regs, SIGSEGV, code, addr); |
| return; |
| } |
| |
| no_context(regs, addr); |
| } |
| |
| static inline void |
| bad_area(struct pt_regs *regs, struct mm_struct *mm, int code, |
| unsigned long addr) |
| { |
| mmap_read_unlock(mm); |
| |
| bad_area_nosemaphore(regs, code, addr); |
| } |
| |
| static inline void vmalloc_fault(struct pt_regs *regs, int code, unsigned long addr) |
| { |
| pgd_t *pgd, *pgd_k; |
| pud_t *pud_k; |
| p4d_t *p4d_k; |
| pmd_t *pmd_k; |
| pte_t *pte_k; |
| int index; |
| unsigned long pfn; |
| |
| /* 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); |
| pfn = csr_read(CSR_SATP) & SATP_PPN; |
| pgd = (pgd_t *)pfn_to_virt(pfn) + index; |
| pgd_k = init_mm.pgd + index; |
| |
| if (!pgd_present(*pgd_k)) { |
| no_context(regs, addr); |
| return; |
| } |
| set_pgd(pgd, *pgd_k); |
| |
| p4d_k = p4d_offset(pgd_k, addr); |
| if (!p4d_present(*p4d_k)) { |
| no_context(regs, addr); |
| return; |
| } |
| |
| pud_k = pud_offset(p4d_k, addr); |
| if (!pud_present(*pud_k)) { |
| no_context(regs, addr); |
| return; |
| } |
| if (pud_leaf(*pud_k)) |
| goto flush_tlb; |
| |
| /* |
| * Since the vmalloc area is global, it is unnecessary |
| * to copy individual PTEs |
| */ |
| pmd_k = pmd_offset(pud_k, addr); |
| if (!pmd_present(*pmd_k)) { |
| no_context(regs, addr); |
| return; |
| } |
| if (pmd_leaf(*pmd_k)) |
| goto flush_tlb; |
| |
| /* |
| * 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)) { |
| no_context(regs, addr); |
| return; |
| } |
| |
| /* |
| * 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. |
| */ |
| flush_tlb: |
| local_flush_tlb_page(addr); |
| } |
| |
| static inline bool access_error(unsigned long cause, struct vm_area_struct *vma) |
| { |
| switch (cause) { |
| case EXC_INST_PAGE_FAULT: |
| if (!(vma->vm_flags & VM_EXEC)) { |
| return true; |
| } |
| break; |
| case EXC_LOAD_PAGE_FAULT: |
| /* Write implies read */ |
| if (!(vma->vm_flags & (VM_READ | VM_WRITE))) { |
| return true; |
| } |
| break; |
| case EXC_STORE_PAGE_FAULT: |
| if (!(vma->vm_flags & VM_WRITE)) { |
| return true; |
| } |
| break; |
| default: |
| panic("%s: unhandled cause %lu", __func__, cause); |
| } |
| return false; |
| } |
| |
| /* |
| * This routine handles page faults. It determines the address and the |
| * problem, and then passes it off to one of the appropriate routines. |
| */ |
| void handle_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; |
| |
| if (kprobe_page_fault(regs, cause)) |
| return; |
| |
| /* |
| * 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 ((!IS_ENABLED(CONFIG_MMU) || !IS_ENABLED(CONFIG_64BIT)) && |
| unlikely(addr >= VMALLOC_START && addr < VMALLOC_END)) { |
| vmalloc_fault(regs, code, addr); |
| return; |
| } |
| |
| /* Enable interrupts if they were enabled in the parent context. */ |
| if (!regs_irqs_disabled(regs)) |
| 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)) { |
| tsk->thread.bad_cause = cause; |
| no_context(regs, addr); |
| return; |
| } |
| |
| if (user_mode(regs)) |
| flags |= FAULT_FLAG_USER; |
| |
| if (!user_mode(regs) && addr < TASK_SIZE && unlikely(!(regs->status & SR_SUM))) { |
| if (fixup_exception(regs)) |
| return; |
| |
| die_kernel_fault("access to user memory without uaccess routines", addr, regs); |
| } |
| |
| perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr); |
| |
| if (cause == EXC_STORE_PAGE_FAULT) |
| flags |= FAULT_FLAG_WRITE; |
| else if (cause == EXC_INST_PAGE_FAULT) |
| flags |= FAULT_FLAG_INSTRUCTION; |
| if (!(flags & FAULT_FLAG_USER)) |
| goto lock_mmap; |
| |
| vma = lock_vma_under_rcu(mm, addr); |
| if (!vma) |
| goto lock_mmap; |
| |
| if (unlikely(access_error(cause, vma))) { |
| vma_end_read(vma); |
| goto lock_mmap; |
| } |
| |
| fault = handle_mm_fault(vma, addr, flags | FAULT_FLAG_VMA_LOCK, regs); |
| if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED))) |
| vma_end_read(vma); |
| |
| if (!(fault & VM_FAULT_RETRY)) { |
| count_vm_vma_lock_event(VMA_LOCK_SUCCESS); |
| goto done; |
| } |
| count_vm_vma_lock_event(VMA_LOCK_RETRY); |
| |
| if (fault_signal_pending(fault, regs)) { |
| if (!user_mode(regs)) |
| no_context(regs, addr); |
| return; |
| } |
| lock_mmap: |
| |
| retry: |
| vma = lock_mm_and_find_vma(mm, addr, regs); |
| if (unlikely(!vma)) { |
| tsk->thread.bad_cause = cause; |
| bad_area_nosemaphore(regs, code, addr); |
| return; |
| } |
| |
| /* |
| * Ok, we have a good vm_area for this memory access, so |
| * we can handle it. |
| */ |
| code = SEGV_ACCERR; |
| |
| if (unlikely(access_error(cause, vma))) { |
| tsk->thread.bad_cause = cause; |
| bad_area(regs, mm, code, addr); |
| return; |
| } |
| |
| /* |
| * 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, regs); |
| |
| /* |
| * If we need to retry but a fatal signal is pending, handle the |
| * signal first. We do not need to release the mmap_lock because it |
| * would already be released in __lock_page_or_retry in mm/filemap.c. |
| */ |
| if (fault_signal_pending(fault, regs)) { |
| if (!user_mode(regs)) |
| no_context(regs, addr); |
| return; |
| } |
| |
| /* The fault is fully completed (including releasing mmap lock) */ |
| if (fault & VM_FAULT_COMPLETED) |
| return; |
| |
| if (unlikely(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); |
| |
| done: |
| if (unlikely(fault & VM_FAULT_ERROR)) { |
| tsk->thread.bad_cause = cause; |
| mm_fault_error(regs, addr, fault); |
| return; |
| } |
| return; |
| } |