https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=219399
--- Comment #190 from rozhuk...@gmail.com ---
"On AMD, the tool discovered that some processors generate
a #UD (undefined opcode) exception prior to completing the
instruction fetch. Per AMD specifications, a #PF (page fault)
exception occurring during an instruction fetch should
supersede a #UD exception, but in the instruction search,
which places the last bytes of the instruction on a non
-
executable page, some processors generate the #UD before the
final bytes are moved off of the read/write page. It appears
that AMD discovered this at around the same time as this
research; the newest AMD Architecture Programmer’s
Manual (March 2017) was updated to allow this situation."
From:
https://github.com/xoreaxeaxeax/sandsifter/blob/master/references/domas_breaking_the_x86_isa_wp.pdf
Tool: https://github.com/xoreaxeaxeax/sandsifter
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