(2012/01/12 7:11), Takuya Yoshikawa wrote:
On Wed, 11 Jan 2012 18:53:30 +0200
Nadav Amit<namit@xxxxxxxxxxxxxxxxx> wrote:
An exception might occur during decode (e.g., #PF during fetch).
Currently, the exception is ignored and emulation is performed.
Note that the decode/emulation will not be continued in such a case.
insn_fetch() is a bit tricky macro and it contains "goto done" to outside.
So if an error happens during fetching the instruction, x86_decode_insn()
will handle the X86EMUL_* fault value and returns FAIL immediately.
Takuya
When I cleaned up insn_fetch(), I thought that fetching the instruction
which is being executed by the guest cannot cause #PF.
The possibility that a meaningless userspace might similtaneously unmap
the page, noted by Avi IIRC, was ignored intentionally, so we just fail
in such a case.
Did you see any real problem?
Takuya
Instead, emulation should be skipped and the fault should be injected.
Skipping instruction should report a failure in this case.
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