| // SPDX-License-Identifier: GPL-2.0 |
| /* |
| * arch/cris/mm/fault.c |
| * |
| * Copyright (C) 2000-2010 Axis Communications AB |
| */ |
| |
| #include <linux/mm.h> |
| #include <linux/interrupt.h> |
| #include <linux/extable.h> |
| #include <linux/wait.h> |
| #include <linux/sched/signal.h> |
| #include <linux/uaccess.h> |
| #include <arch/system.h> |
| |
| extern int find_fixup_code(struct pt_regs *); |
| extern void die_if_kernel(const char *, struct pt_regs *, long); |
| extern void show_registers(struct pt_regs *regs); |
| |
| /* debug of low-level TLB reload */ |
| #undef DEBUG |
| |
| #ifdef DEBUG |
| #define D(x) x |
| #else |
| #define D(x) |
| #endif |
| |
| /* debug of higher-level faults */ |
| #define DPG(x) |
| |
| /* current active page directory */ |
| |
| DEFINE_PER_CPU(pgd_t *, current_pgd); |
| unsigned long cris_signal_return_page; |
| |
| /* |
| * This routine handles page faults. It determines the address, |
| * and the problem, and then passes it off to one of the appropriate |
| * routines. |
| * |
| * Notice that the address we're given is aligned to the page the fault |
| * occurred in, since we only get the PFN in R_MMU_CAUSE not the complete |
| * address. |
| * |
| * error_code: |
| * bit 0 == 0 means no page found, 1 means protection fault |
| * bit 1 == 0 means read, 1 means write |
| * |
| * If this routine detects a bad access, it returns 1, otherwise it |
| * returns 0. |
| */ |
| |
| asmlinkage void |
| do_page_fault(unsigned long address, struct pt_regs *regs, |
| int protection, int writeaccess) |
| { |
| struct task_struct *tsk; |
| struct mm_struct *mm; |
| struct vm_area_struct * vma; |
| siginfo_t info; |
| int fault; |
| unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; |
| |
| D(printk(KERN_DEBUG |
| "Page fault for %lX on %X at %lX, prot %d write %d\n", |
| address, smp_processor_id(), instruction_pointer(regs), |
| protection, writeaccess)); |
| |
| tsk = current; |
| |
| /* |
| * We 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. |
| * |
| * NOTE2: This is done so that, when updating the vmalloc |
| * mappings we don't have to walk all processes pgdirs and |
| * add the high mappings all at once. Instead we do it as they |
| * are used. However vmalloc'ed page entries have the PAGE_GLOBAL |
| * bit set so sometimes the TLB can use a lingering entry. |
| * |
| * This verifies that the fault happens in kernel space |
| * and that the fault was not a protection error (error_code & 1). |
| */ |
| |
| if (address >= VMALLOC_START && |
| !protection && |
| !user_mode(regs)) |
| goto vmalloc_fault; |
| |
| /* When stack execution is not allowed we store the signal |
| * trampolines in the reserved cris_signal_return_page. |
| * Handle this in the exact same way as vmalloc (we know |
| * that the mapping is there and is valid so no need to |
| * call handle_mm_fault). |
| */ |
| if (cris_signal_return_page && |
| address == cris_signal_return_page && |
| !protection && user_mode(regs)) |
| goto vmalloc_fault; |
| |
| /* we can and should enable interrupts at this point */ |
| local_irq_enable(); |
| |
| mm = tsk->mm; |
| info.si_code = SEGV_MAPERR; |
| |
| /* |
| * If we're in an interrupt, have pagefaults disabled or have no |
| * user context, we must not take the fault. |
| */ |
| |
| if (faulthandler_disabled() || !mm) |
| goto no_context; |
| |
| if (user_mode(regs)) |
| flags |= FAULT_FLAG_USER; |
| retry: |
| down_read(&mm->mmap_sem); |
| vma = find_vma(mm, address); |
| if (!vma) |
| goto bad_area; |
| if (vma->vm_start <= address) |
| goto good_area; |
| if (!(vma->vm_flags & VM_GROWSDOWN)) |
| goto bad_area; |
| if (user_mode(regs)) { |
| /* |
| * accessing the stack below usp is always a bug. |
| * we get page-aligned addresses so we can only check |
| * if we're within a page from usp, but that might be |
| * enough to catch brutal errors at least. |
| */ |
| if (address + PAGE_SIZE < rdusp()) |
| goto bad_area; |
| } |
| if (expand_stack(vma, address)) |
| goto bad_area; |
| |
| /* |
| * Ok, we have a good vm_area for this memory access, so |
| * we can handle it.. |
| */ |
| |
| good_area: |
| info.si_code = SEGV_ACCERR; |
| |
| /* first do some preliminary protection checks */ |
| |
| if (writeaccess == 2){ |
| if (!(vma->vm_flags & VM_EXEC)) |
| goto bad_area; |
| } else if (writeaccess == 1) { |
| if (!(vma->vm_flags & VM_WRITE)) |
| goto bad_area; |
| flags |= FAULT_FLAG_WRITE; |
| } else { |
| if (!(vma->vm_flags & (VM_READ | VM_EXEC))) |
| goto bad_area; |
| } |
| |
| /* |
| * If for any reason at all we couldn't handle the fault, |
| * make sure we exit gracefully rather than endlessly redo |
| * the fault. |
| */ |
| |
| fault = handle_mm_fault(vma, address, flags); |
| |
| if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) |
| return; |
| |
| if (unlikely(fault & VM_FAULT_ERROR)) { |
| if (fault & VM_FAULT_OOM) |
| goto out_of_memory; |
| else if (fault & VM_FAULT_SIGSEGV) |
| goto bad_area; |
| else if (fault & VM_FAULT_SIGBUS) |
| goto do_sigbus; |
| BUG(); |
| } |
| |
| if (flags & FAULT_FLAG_ALLOW_RETRY) { |
| if (fault & VM_FAULT_MAJOR) |
| tsk->maj_flt++; |
| else |
| tsk->min_flt++; |
| if (fault & VM_FAULT_RETRY) { |
| 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); |
| |
| bad_area_nosemaphore: |
| DPG(show_registers(regs)); |
| |
| /* User mode accesses just cause a SIGSEGV */ |
| |
| if (user_mode(regs)) { |
| #ifdef CONFIG_NO_SEGFAULT_TERMINATION |
| DECLARE_WAIT_QUEUE_HEAD(wq); |
| #endif |
| printk(KERN_NOTICE "%s (pid %d) segfaults for page " |
| "address %08lx at pc %08lx\n", |
| tsk->comm, tsk->pid, |
| address, instruction_pointer(regs)); |
| |
| /* With DPG on, we've already dumped registers above. */ |
| DPG(if (0)) |
| show_registers(regs); |
| |
| #ifdef CONFIG_NO_SEGFAULT_TERMINATION |
| wait_event_interruptible(wq, 0 == 1); |
| #else |
| info.si_signo = SIGSEGV; |
| info.si_errno = 0; |
| /* info.si_code has been set above */ |
| info.si_addr = (void *)address; |
| force_sig_info(SIGSEGV, &info, tsk); |
| #endif |
| return; |
| } |
| |
| no_context: |
| |
| /* Are we prepared to handle this kernel fault? |
| * |
| * (The kernel has valid exception-points in the source |
| * when it accesses user-memory. When it fails in one |
| * of those points, we find it in a table and do a jump |
| * to some fixup code that loads an appropriate error |
| * code) |
| */ |
| |
| if (find_fixup_code(regs)) |
| return; |
| |
| /* |
| * Oops. The kernel tried to access some bad page. We'll have to |
| * terminate things with extreme prejudice. |
| */ |
| |
| if (!oops_in_progress) { |
| oops_in_progress = 1; |
| if ((unsigned long) (address) < PAGE_SIZE) |
| printk(KERN_ALERT "Unable to handle kernel NULL " |
| "pointer dereference"); |
| else |
| printk(KERN_ALERT "Unable to handle kernel access" |
| " at virtual address %08lx\n", address); |
| |
| die_if_kernel("Oops", regs, (writeaccess << 1) | protection); |
| oops_in_progress = 0; |
| } |
| |
| do_exit(SIGKILL); |
| |
| /* |
| * We ran out of memory, or some other thing happened to us that made |
| * us unable to handle the page fault gracefully. |
| */ |
| |
| 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); |
| |
| /* |
| * Send a sigbus, regardless of whether we were in kernel |
| * or user mode. |
| */ |
| info.si_signo = SIGBUS; |
| info.si_errno = 0; |
| info.si_code = BUS_ADRERR; |
| info.si_addr = (void *)address; |
| force_sig_info(SIGBUS, &info, tsk); |
| |
| /* Kernel mode? Handle exceptions or die */ |
| if (!user_mode(regs)) |
| goto no_context; |
| return; |
| |
| vmalloc_fault: |
| { |
| /* |
| * Synchronize this task's top level page-table |
| * with the 'reference' page table. |
| * |
| * Use current_pgd instead of tsk->active_mm->pgd |
| * since the latter might be unavailable if this |
| * code is executed in a misfortunately run irq |
| * (like inside schedule() between switch_mm and |
| * switch_to...). |
| */ |
| |
| int offset = pgd_index(address); |
| pgd_t *pgd, *pgd_k; |
| pud_t *pud, *pud_k; |
| pmd_t *pmd, *pmd_k; |
| pte_t *pte_k; |
| |
| pgd = (pgd_t *)per_cpu(current_pgd, smp_processor_id()) + offset; |
| pgd_k = init_mm.pgd + offset; |
| |
| /* Since we're two-level, we don't need to do both |
| * set_pgd and set_pmd (they do the same thing). If |
| * we go three-level at some point, do the right thing |
| * with pgd_present and set_pgd here. |
| * |
| * Also, since the vmalloc area is global, we don't |
| * need to copy individual PTE's, it is enough to |
| * copy the pgd pointer into the pte page of the |
| * root task. If that is there, we'll find our pte if |
| * it exists. |
| */ |
| |
| pud = pud_offset(pgd, address); |
| pud_k = pud_offset(pgd_k, address); |
| if (!pud_present(*pud_k)) |
| goto no_context; |
| |
| pmd = pmd_offset(pud, address); |
| pmd_k = pmd_offset(pud_k, address); |
| |
| if (!pmd_present(*pmd_k)) |
| goto bad_area_nosemaphore; |
| |
| 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, address); |
| if (!pte_present(*pte_k)) |
| goto no_context; |
| |
| return; |
| } |
| } |
| |
| /* Find fixup code. */ |
| int |
| find_fixup_code(struct pt_regs *regs) |
| { |
| const struct exception_table_entry *fixup; |
| /* in case of delay slot fault (v32) */ |
| unsigned long ip = (instruction_pointer(regs) & ~0x1); |
| |
| fixup = search_exception_tables(ip); |
| if (fixup != 0) { |
| /* Adjust the instruction pointer in the stackframe. */ |
| instruction_pointer(regs) = fixup->fixup; |
| arch_fixup(regs); |
| return 1; |
| } |
| |
| return 0; |
| } |