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[Xen-devel] Question about the repeated page fault

  • To: xen-devel@xxxxxxxxxxxxxxxxxxx
  • From: Kai Luo <kluo@xxxxxxxxxx>
  • Date: Sat, 21 Sep 2013 07:52:22 -0700 (PDT)
  • Delivery-date: Sat, 21 Sep 2013 14:53:15 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xen.org>
  • Thread-index: BkbqvFxXQPeIqHWSOV3tOHb6QYA1Fw==
  • Thread-topic: Question about the repeated page fault

Hello everyone:

    Recently,I am working on a feature of intercepting the giving function in windows SSDT table,I replace address of function in SSDT whith an invalid address.
    The question is when I trapped the page fault caused by accessing the invalid address and I recovered it to the correct function address,I can recive the same page fault again.That is to say:
          1.I trapped a page fault caused by an invalid address in sh_page_fault(struct vcpu *v,unsigned long va,struct cpu_user_regs *regs)
          2.I rescover the guest eip to the correct address using the following code(Missing something?):
                  regs->eip = <correct_addr>
                  __vmwrite(GUEST_RIP, <correct_addr>);
          3.Another page fault caused by the same address occured
    I dumped the vmcs when the page faults occured,contents in vmcs are almost the same except the 'Virtual processor ID',still confused.Could you help me to analyse the strange phenomenon?Thank you very much!


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