360 lines
8.8 KiB
C
360 lines
8.8 KiB
C
/*
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* OpenRISC fault.c
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*
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* Linux architectural port borrowing liberally from similar works of
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* others. All original copyrights apply as per the original source
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* declaration.
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*
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* Modifications for the OpenRISC architecture:
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* Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com>
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* Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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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/module.h>
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#include <linux/sched.h>
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#include <asm/uaccess.h>
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#include <asm/siginfo.h>
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#include <asm/signal.h>
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#define NUM_TLB_ENTRIES 64
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#define TLB_OFFSET(add) (((add) >> PAGE_SHIFT) & (NUM_TLB_ENTRIES-1))
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unsigned long pte_misses; /* updated by do_page_fault() */
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unsigned long pte_errors; /* updated by do_page_fault() */
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/* __PHX__ :: - check the vmalloc_fault in do_page_fault()
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* - also look into include/asm-or32/mmu_context.h
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*/
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volatile pgd_t *current_pgd;
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extern void die(char *, struct pt_regs *, long);
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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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* 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 do_page_fault(struct pt_regs *regs, unsigned long address,
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unsigned long vector, int write_acc)
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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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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.
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*/
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if (address >= VMALLOC_START &&
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(vector != 0x300 && vector != 0x400) &&
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!user_mode(regs))
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goto vmalloc_fault;
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/* If exceptions were enabled, we can reenable them here */
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if (user_mode(regs)) {
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/* Exception was in userspace: reenable interrupts */
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local_irq_enable();
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} else {
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/* If exception was in a syscall, then IRQ's may have
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* been enabled or disabled. If they were enabled,
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* reenable them.
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*/
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if (regs->sr && (SPR_SR_IEE | SPR_SR_TEE))
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local_irq_enable();
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}
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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 or have no user
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* context, we must not take the fault..
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*/
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if (in_interrupt() || !mm)
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goto no_context;
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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 < regs->sp)
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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 (write_acc) {
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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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/* not present */
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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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/* are we trying to execute nonexecutable area */
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if ((vector == 0x400) && !(vma->vm_page_prot.pgprot & _PAGE_EXEC))
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goto bad_area;
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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(mm, 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_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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/*RGD modeled on Cris */
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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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/* 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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/* User mode accesses just cause a SIGSEGV */
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if (user_mode(regs)) {
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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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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 acesses 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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{
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const struct exception_table_entry *entry;
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__asm__ __volatile__("l.nop 42");
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if ((entry = search_exception_tables(regs->pc)) != NULL) {
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/* Adjust the instruction pointer in the stackframe */
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regs->pc = entry->fixup;
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return;
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}
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}
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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 ((unsigned long)(address) < PAGE_SIZE)
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printk(KERN_ALERT
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"Unable to handle kernel NULL pointer dereference");
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else
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printk(KERN_ALERT "Unable to handle kernel access");
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printk(" at virtual address 0x%08lx\n", address);
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die("Oops", regs, write_acc);
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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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__asm__ __volatile__("l.nop 42");
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__asm__ __volatile__("l.nop 1");
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up_read(&mm->mmap_sem);
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printk("VM: killing process %s\n", tsk->comm);
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if (user_mode(regs))
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do_exit(SIGKILL);
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goto no_context;
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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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/*
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phx_warn("do_page_fault(): vmalloc_fault will not work, "
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"since current_pgd assign a proper value somewhere\n"
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"anyhow we don't need this at the moment\n");
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phx_mmu("vmalloc_fault");
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*/
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pgd = (pgd_t *)current_pgd + 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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