By using bootstrap symbols to communicate these addresseses, rather than dlsym
lookups, we no longer need them to be exported from the main executable. On ELF,
where symbols aren't exported from the main executable by default, this
eliminates a common source of missing symbol errors and allows for smaller
executables (if exports from the main executable aren't otherwise needed and
can be removed).
Previously, EPCEHFrameRegistrar always used the
ExecutorProcessControl::loadDylib(nullptr) method to obtain a handle for the
process, but this doesn't work if the registration functions aren't visible in
a standard search of the process (e.g. if the JIT is in a plugin that is loaded
with RTLD_LOCAL).
This patch retains the old behavior by default, but allows clients to supply
their own handle for the library containing the registration functions if they
need to (e.g. to work around limitations like RDLD_LOCAL above, which aren't
expressible within the existing loadDylib / DynamicLibrary APIs).
This re-applies 133f86e95492b2a00b944e070878424cfa73f87c, which was reverted in
c5965a411c635106a47738b8d2e24db822b7416f while I investigated bot failures.
The original failure contained an arithmetic conversion think-o (on line 419 of
EHFrameSupport.cpp) that could cause failures on 32-bit platforms. The issue
should be fixed in this patch.
This re-applies e32b1eee6aab52e2b7b75ee15e506b3e7dd30e68, which was reverted in
20675d8f7dab293172266fdde426c2173b5b3997 due to broken unit tests. This patch
includes fixes for the tests.
SPSExecutorAddr will now be serializable to/from ExecutorAddr, rather than
uint64_t. This improves type safety when working with serialized addresses.
Also updates the SupportFunctionCall to use an ExecutorAddrRange (rather than
a separate ExecutorAddr addr and uint64_t size field), and updates the
tpctypes::*Write data structures to use ExecutorAddr rather than
JITTargetAddress.
Removing the 'ess' suffix improves the ergonomics without sacrificing clarity.
Since this class is likely to be used more frequently in the future it's worth
some short term pain to fix this now.
Wrapper function call and dispatch handler helpers are moved to
ExecutionSession, and existing EPC-based tools are re-written to take an
ExecutionSession argument instead.
Requiring an ExecutorProcessControl instance simplifies existing EPC based
utilities (which only need to take an ES now), and should encourage more
utilities to use the EPC interface. It also simplifies process termination,
since the session can automatically call ExecutorProcessControl::disconnect
(previously this had to be done manually, and carefully ordered with the
rest of JIT tear-down to work correctly).
This is a first step towards consistently using the term 'executor' for the
process that executes JIT'd code. I've opted for 'executor' as the preferred
term over 'target' as target is already heavily overloaded ("the target
machine for the executor" is much clearer than "the target machine for the
target").
