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