[dtrace-discuss] FBT implementation on x86

[Saravanan S]

Hi,

I was going through the implementation of FBT provider on x86. I figured out
that entry and the exit instructions in a function will be replaced by the
"lock" instruction on a probe enable which on execution causes a invalid
opcode exception. Is there any reason why lock was choosen as the
instruction to cause the invalid opcode trap? Is there any chance of a "ret"
instruction followed by ADD,CMPXCHG and other instructions which can be
prefixed by the "lock" instruction in memory. In that case, if we replace
ret by lock we might not trap in to the invoptrap routine?

Thanks in advance
Saravanan S
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