i#2350 rseq: Target start instead of handler #3791
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Changes the native execution of the rseq region to target the start of the sequence rather than the abort handler. This is done for two reasons: to support abort handlers which simply abort and do not restart, and to make it much easier in the future to run a copy of the sequence rather than rely on call-return semantics in the app code. Adds preservation of input registers, limited to general-purpose registers clearly read-before-written in the sequence. Documents the new restrictions. Tries to pick a better scratch register, though this should go away once we switch to using a local copy. Issue: #2350
We won't need a register we can't restore, though: i.e., we won't need a dead register. |
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I'm done. |
Changes the call* to go through TLS, avoiding the need for a dead register. Inserts register saving code at the very start, avoiding conflits with client (esp drreg) instrumentation. Adds attach handling. Inserts consistently before next_instr for end-of-rseq mangling.
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PTAL |
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LGTM! |
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Changes the native execution of the rseq region to target the start of
the sequence rather than the abort handler. This is done for two
reasons: to support abort handlers which simply abort and do not
restart, and to make it much easier in the future to run a copy of the
sequence rather than rely on call-return semantics in the app code.
Adds preservation of input registers, limited to general-purpose
registers clearly read-before-written in the sequence. Documents the
new restrictions. Tries to pick a better scratch register, though
this should go away once we switch to using a local copy.
Issue: #2350