278 lines
6.7 KiB
C
278 lines
6.7 KiB
C
/*
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* Copyright (C) 2009 Wind River Systems Inc
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* Implemented by fredrik.markstrom@gmail.com and ivarholmqvist@gmail.com
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*
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* based on arch/mips/mm/fault.c which is:
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*
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* Copyright (C) 1995-2000 Ralf Baechle
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*
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* This file is subject to the terms and conditions of the GNU General Public
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* License. See the file "COPYING" in the main directory of this archive
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* for more details.
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*/
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#include <linux/signal.h>
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#include <linux/sched.h>
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#include <linux/sched/debug.h>
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#include <linux/interrupt.h>
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#include <linux/kernel.h>
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#include <linux/errno.h>
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#include <linux/string.h>
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#include <linux/types.h>
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#include <linux/ptrace.h>
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#include <linux/mman.h>
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#include <linux/mm.h>
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#include <linux/extable.h>
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#include <linux/uaccess.h>
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#include <linux/ptrace.h>
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#include <asm/mmu_context.h>
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#include <asm/traps.h>
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#define EXC_SUPERV_INSN_ACCESS 9 /* Supervisor only instruction address */
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#define EXC_SUPERV_DATA_ACCESS 11 /* Supervisor only data address */
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#define EXC_X_PROTECTION_FAULT 13 /* TLB permission violation (x) */
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#define EXC_R_PROTECTION_FAULT 14 /* TLB permission violation (r) */
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#define EXC_W_PROTECTION_FAULT 15 /* TLB permission violation (w) */
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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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asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long cause,
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unsigned long address)
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{
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struct vm_area_struct *vma = NULL;
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struct task_struct *tsk = current;
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struct mm_struct *mm = tsk->mm;
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int code = SEGV_MAPERR;
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int fault;
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unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
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cause >>= 2;
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/* Restart the instruction */
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regs->ea -= 4;
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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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if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END)) {
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if (user_mode(regs))
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goto bad_area_nosemaphore;
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else
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goto vmalloc_fault;
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}
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if (unlikely(address >= TASK_SIZE))
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goto bad_area_nosemaphore;
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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 (faulthandler_disabled() || !mm)
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goto bad_area_nosemaphore;
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if (user_mode(regs))
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flags |= FAULT_FLAG_USER;
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if (!down_read_trylock(&mm->mmap_sem)) {
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if (!user_mode(regs) && !search_exception_tables(regs->ea))
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goto bad_area_nosemaphore;
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retry:
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down_read(&mm->mmap_sem);
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}
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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 (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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code = SEGV_ACCERR;
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switch (cause) {
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case EXC_SUPERV_INSN_ACCESS:
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goto bad_area;
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case EXC_SUPERV_DATA_ACCESS:
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goto bad_area;
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case EXC_X_PROTECTION_FAULT:
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if (!(vma->vm_flags & VM_EXEC))
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goto bad_area;
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break;
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case EXC_R_PROTECTION_FAULT:
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if (!(vma->vm_flags & VM_READ))
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goto bad_area;
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break;
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case EXC_W_PROTECTION_FAULT:
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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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break;
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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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/*
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* Major/minor page fault accounting is only done on the
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* initial attempt. If we go through a retry, it is extremely
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* likely that the page will be found in page cache at that point.
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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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current->maj_flt++;
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else
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current->min_flt++;
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if (fault & VM_FAULT_RETRY) {
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/* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
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* of starvation. */
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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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/* User mode accesses just cause a SIGSEGV */
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if (user_mode(regs)) {
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if (unhandled_signal(current, SIGSEGV) && printk_ratelimit()) {
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pr_info("%s: unhandled page fault (%d) at 0x%08lx, "
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"cause %ld\n", current->comm, SIGSEGV, address, cause);
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show_regs(regs);
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}
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_exception(SIGSEGV, regs, code, address);
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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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if (fixup_exception(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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bust_spinlocks(1);
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pr_alert("Unable to handle kernel %s at virtual address %08lx",
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address < PAGE_SIZE ? "NULL pointer dereference" :
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"paging request", address);
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pr_alert("ea = %08lx, ra = %08lx, cause = %ld\n", regs->ea, regs->ra,
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cause);
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panic("Oops");
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return;
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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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/* 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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_exception(SIGBUS, regs, BUS_ADRERR, address);
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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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* Do _not_ use "tsk" here. We might be inside
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* an interrupt in the middle of a task switch..
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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_current + offset;
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pgd_k = init_mm.pgd + offset;
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if (!pgd_present(*pgd_k))
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goto no_context;
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set_pgd(pgd, *pgd_k);
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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 no_context;
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set_pmd(pmd, *pmd_k);
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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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flush_tlb_one(address);
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return;
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}
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}
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