When a fork occurs FEX needs to be incredibly careful as any thread
(that isn't forking) that holds a lock will vanish when the fork occurs.
At this point if the newly forked process tries to use these mutexes
then the process hangs indefinitely.
The three major mutexes that need to be held during a fork:
- Code Invalidation mutex
- This is the highest priority and causes us to hang frequently.
- This is highly likely to occur when one thread is loading shared
libraries and another thread is forking.
- Happens frequently with Wine and steam.
- VMA tracking mutex
- This one happens when one thread is allocating memory while a fork
occurs.
- This closely relates to the code invalidation mutex, just happens at
the syscall layer instead of the FEXCore layer.
- Happens as frequently as the code invalidation mutex.
- Allocation mutex
- This mutex is used for FEX's 64-bit Allocator, this happens when FEX
is allocating memory on one thread and a fork occurs.
- Fairly infrequent because jemalloc doesn't allocate VMA regions that
often.
While this likely doesn't hit all of the FEX mutexes, this hits the ones
that are burning fires and are happening frequently.
- FEXCore: Adds forkable mutex/locks
Necessary since we have a few locations in FEX that need to be locked
before and after a fork.
When a fork occurs the locks must be locked prior to the fork. Then
afterwards they either need to unlock or be set to default
initialization state.
- Parent
- Does an unlock
- Child
- Sets the lock to default initialization state
- This is because it pthreads does TID based ownership checking on
unique locks and refcount based waiting for shared locks.
- No way to "unlock" after fork in this case other than default
initializing.
We can handle this in the dispatcher itself, so that we don't need to pass along
the register size as a member of the opcode. This gets rid of some unnecessary duplication
of functionality in the backends and makes it so potential backends don't need to deal
with this.
Previously, the bits that we support in the MXCSR weren't being saved,
which means that some opcode patterns may fail to restore the rounding mode
properly.
e.g. FXSAVE, followed by FNINIT, followed by FXRSTOR wouldn't restore the
rounding mode properly
This fixes that.
FEX's current implementation of RIP reconstruction is limited to the
entrypoint that a single block has. This will cause the RIP to be
incorrect past the first instruction in that block.
While this is fine for a decent number of games, especially since fault
handling isn't super common. This doesn't work for all situations.
When testing Ultimate Chicken Horse, we found out that changing the
block size to 1 worked around an early crash in the game's startup.
This game is likely relying on Mono/Unity's AOT compilation step, which
does some more robust faulting that the runtime JIT. Needing the RIP to
be correct since they do some sort of checking for what the code came
from.
This fixes Ultimate Chicken Horse specifically, but will likely fix
other games that are built the same way.
When executing a 32-bit application we were failing to allocate a single
GPR pair. This meant we only have 7 pairs when we could have had 8.
This was because r30 was ending up in the middle of the allocation
arrays so we couldn't safely create a sequential pair of registers.
Organize the register allocation arrays to be unique for each bitness
being executed and then access them through spans instead.
Also works around bug where the RA validation doesn't understand when pair
indexes don't correlate directly to GPR indexes. So while the previous
PR fixed the RA pass, it didn't fix the RA validation pass.
Noticed this when pr57018 32-bit gcc test was run with the #2700 PR
which improved the RA allocation a bit.
When FEX was updated to reclaim 64-bit registers in #2494, I had
mistakenly messed up pair register class conflicts.
The problem is that FEX has r30 stuck in the middle of the RA which
causes the paired registers to need to offset their index half way.
This meant that the conflict index being incorrect was always broken on
32-bit applications ever since that PR.
Keep the intersection indexes in their own array so to can be correctly
indexed at runtime.
Thanks to @asahilina finding out that Osmos started crashing a few
months ago and I finally just got around to bisecting what the problem
was.
This now fixes Osmos from crashing, although the motes are still
invisible on the 32-bit application. Not sure what other havok this has
been causing.
So, uh, this was a little silly to track down. So, having the upper limit
as unsigned was a mistake, since this would cause negative valid lengths to
convert into an unsigned value within the first two flag comparison cases
A -1 valid length can occur if one of the strings starts with a null character
in a vector's first element. (It will be zero and we then subtract it to
make the length zero-based).
Fixes this edge-case up and expands a test to check for this in the future.
Regular LoadStoreTSO operations have gained support for LRCPC and LRCPC2
which changes the semantics of the operation by letting it support
immediate offsets.
The paranoid version of these operations didn't support the immediate
offsets yet which was causing incorrect memory loadstores.
Bring over the new semantics from the regular LoadStoreTSO but without
any nop padding.
`eor <reg>, <reg>, #-1` can't be encoded as an instruction. Instead use
mvn which does the same thing.
Removes a single instruction from each OF calculation for ADC and ADD.
Also no reason to use a switch statement for the source size, just use
_Bfe and calculate the offset based on operation size.
SBB caught in the crossfire to ensure it also isn't using a switch
statement.
These two extensions rely on AVX being supported to be used. Primarily
because they are VEX encoded.
GTA5 is using these flags to determine if it should enable its AVX
support.
Some code in FEX's Arm64 emitter was making an assumption that once
SpillStaticRegs was called that it was safe to still use the SRA
register state.
This wasn't actually true since FEX was using one SRA register to
optimize FPR stores. Assuming that the SRA registers were safe to use
since they were just saved and no longer necessary.
Correct this assumption hell by forcing users of the function to provide
the temporary register directly. In all cases the users have a temporary
available that it can use.
Probably fixes some very weird edge case bugs.
This returns the `XFEATURE_ENABLED_MASK` register which reports what
features are enabled on the CPU.
This behaves similarly to CPUID where it uses an index register in ecx.
This is a prerequisite to enabling XSAVE/XRSTOR and AVX since
applications will expect this to exist.
xsetbv is a privileged instruction and doesn't need to be implemented.
Currently WINE's longjump doesn't work, so instead set a flag that if
HLT is attempted, just exit the JIT.
This will get our unittests executing at least.
InferFromOS doesn't work under WINE.
InferFromIDRegisters doesn't work under Windows but it will under Wine.
Since we don't support Windows, just use InferFromIDRegisters.
Wine syscalls need to end the code block at the point of the syscall.
This is because syscalls may update RIP which means the JIT loop needs
to immediately restart.
Additionally since they can update CPU state, make wine syscalls not
return a result and instead refill the register state from the CPU
state. This will mean the syscall handler will need to update their
result register (RAX?) before returning.
Disabling SRA has been broken a quite a while. Disabling this was
instrumental in figuring out the VC redistributable crash.
Ensure it works by reintroducing non-SRA load/store register handlers,
and by supporting runtime selectable dispatch pointers for the JIT.
Side-bonus, moves the {LOAD,STORE}MEMTSO ops over to this dispatch as
well to make it consistent and probably slightly quicker.
From https://github.com/AsahiLinux/linux/commits/bits/220-tso
This fails gracefully in the case the upstream kernel doesn't support
this feature, so can go in early.
This feature allows FEX to use hardware's TSO emulation capability to
reduce emulation overhead from our atomic/lrcpc implementation.
In the case that the TSO emulation feature is enabled in FEX, we will
check if the hardware supports this feature and then enable it.
If the hardware feature is supported it will then use regular memory
accesses with the expectation that these are x86-TSO in strength.
The only hardware that anyone cares about that supports this is Apple's
M class SoCs. Theoretically NVIDIA Denver/Carmel supports sequentially
consistent, which isn't quite the same thing. I haven't cared to check
if multithreaded SC has as strong of guarantees. But also since
Carmel/Denver hardware is fairly rare, it's hard to care about for our
use case.
Mai