We were registering syscall handlers to the temporary working vectors for
both x86 and x86_64 regardless of which bitness we launched with.
We then only installed the syscall handlers depending on bitness.
This was burning a decent amount of time and some memory on
initialization. Instead just don't register syscall handlers on the
other bitness.
Also stop wasting memory, clear the syscall registration vector after
we've registered everything.
Saves about 28KB of memory per process.
In some cases we can generate more optimal code if we have more
information about a syscall which number gets const-propagated.
In particular optimizing through syscalls, not synchronizing state, and
never returning.
- Noreturn is used by a syscall that never returns, like exit.
This means that it never needs to try and synchronize state coming back
- Not synchronizing state and optimizing through syscalls
Useful for syscalls that don't read the state past arguments and only
returns a value.
Due to the way this syscall handles siginfo_t, we only need to shift
data through the padding.
This is due to the syscall not allowing you to send siginfo_t with
si_code being positive. Which is what the kernel uses to interpret the
data if it is reinterpreting it.
Syscalls on x86-64 have a gap in the range of [335, 424) where these are
defined as returning ENOSYS.
This was a decision that the Linux developers decided on so x86-64 can
realign its syscall numbers to a common infrastructure.
Turns out that Proton Experimental was using a 32-bit only syscall to
check if the feature existed and was listening for ENOSYS.
They did this unconditionally on both x86 and x86-64 and it hits this
gap section.
This was introduced in Proton Experimental with commit
563fb0fbe2a49734aede87bedccb20daefc553b0
Message: "ntdll: Use clock_gettime64 if supported."
This is technically valid since it falls within this gap section but
leaves a bad taste.
We can safely ignore this section so set it up with the
UnimplementedSyscallSafe handler and also assign it to Syscall MAX so it
can go down our fast handler.
Not that this is likely to be a performance critical path.
Fixes Proton Experimental crashing when run under FEX.
These maps are primarily used for debugging, so we don't need to
construct and allocate the data until GetSyscallName() is called.
Removes a bit of memory usage and a static constructor for release
builds.
Migrates lingering instances of the old logger over to fmt where
applicable. This allows removing some of the old defines and functions.
The only remaining usages of the printf-based variant of the logger is
in Tests/LinuxSyscalls/Syscalls.cpp for the strace handling.
This isn't quite a 100% clean sweep of IWYU.
There are some false positives where clang fails.
Additionally there are still a few missed in the frontend side of things
that I didn't get to
This is a very simple initial implementation.
io_uring allows some things that are hard to capture like setting personalities.
Assume sane usage for now
C++ no-op functions can't optimize out the predicate arguments in all cases.
This was causing a problem where zero cost assertions weren't actually zero cost.
The only way to resolve this is to actually use macros sadly enough.
This will give a fairly hefty performance uplift with anything operating on IR.
Sadly these things can't be split without breaking functionality so it
turns in to a bit of a mess.
SyscallHandler is very much something that is a Linux only construct and
shouldn't be in FEXCore itself. Lets the frontend register a
Syscallhandler with FEXCore. FEXCore itself is then aware of the current
syscall ABI and handles the ABI in an optimal fashion.
So it is not a 100% clean break otherwise we would lose performance.
The SignalDelegator then needs to move to the frontend since the
SyscallHandler requires it for signal based syscalls.
The CPU backend signal handling still needs to happen in FEXCore because
it is a very tight coupling with the CPU backend.
Once we need to support more Signal handling we can give the backends
cleaner support to select which specific OS handler to handle.
Ryan Houdek