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| layout: post | ||
| title: FEX 2501 Tagged | ||
| author: FEX-Emu Maintainers | ||
| --- | ||
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| Welcome back to another new FEX-Emu release in the new year! While everyone was out celebrating the holidays, we still managed to get some work done. | ||
| So let's get in to what we did this last month! | ||
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| ## Official WINE WoW64 and Arm64ec package support | ||
| This month we have updated our Ubuntu ppa repository to now support a fex-emu-wine package. This package provides wow64 and arm64ec emulator DLL files | ||
| that can be applied directly to an AArch64 build of WINE, thus allowing you to do x86 and x86-64 emulation inside of WINE directly and removing a ton | ||
| of CPU overhead in the emulation! This is relatively fresh so there will be some teething issues around getting it setup, like the current upstream | ||
| WINE may not integrate directly in to these builds yet. Check out our [wiki](https://wiki.fex-emu.com/index.php/Development:ARM64EC) for more | ||
| information about getting this hooked up. | ||
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| ## Partial support for inline self-modifying code and trap flag | ||
| As we work towards supporting more edge-case behaviour of anti-tamper and anti-debugger software. We have spent some time this month implementing support for inline self-modifying code and the trap flag. | ||
| In particular Denuvo uses inline self-modifying code which is relatively annoying to support, but we can use the fact that it tends to generate | ||
| invalid instructions to determine that a block of code is invalid early, thus letting it work. There's some more work towards making this more robust | ||
| but this gets a decent number of games running. | ||
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| The trap flag on the other hand is interesting because this is an anti-debugger tactic that some badly behaving launchers use. This is because of how | ||
| debuggers treat the trap flag versus how it works when a debugger isn't running, this lets the application detect the debugger and throw an error. | ||
| FEX didn't quite handle this correctly which was causing these launchers to throw their hands up and stop running. | ||
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| A note is that some of this work is only wired up on the WINE side rather than the FEX-Emu Linux emulation side, so mileage may vary! | ||
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| ## JIT bug fixes and performance improvements | ||
| As usual, a lot of fixes landed for our JIT, ranging from incorrect backpatching of unaligned atomics, to incorrect instruction handling, to improving | ||
| performance of a couple of instructions. Let's break down what we fixed this month. | ||
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| ### Fixed backpatching of unaligned atomics with small immediates | ||
| ARM's FEAT_LRCPC2 extension added TSO instructions for small immediate offsets in the range of -256 to 255. These still have the regular atomic | ||
| limitation of ARM where the address needs to be naturally aligned (or within 16 byte granule!) of the access type. FEX needs to emulate unaligned | ||
| memory accesses from x86 by backpatching these instructions to be a DMB plus load or store. We were incorrectly patching these instructions with the | ||
| small offsets. This will improve stability of emulation on hardware that supports the new FEAT_LRCPC2 instructions | ||
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| ### Fix float to integer overflow behaviour | ||
| This is a very important change for how FEX handles when converting a float value to an integer and an overflow occurs. While we knew of the problem, | ||
| we didn't realize how wide reaching the problem was causing problems. In particular this fixes The Talos Principle's audio cuting out, Animal Well's | ||
| music having chirping artifacts, SOMA not allowing interactions with things in the world, Satisfactory's server crashing, and Metaphor Refantazio | ||
| infinite looping before getting in-game! | ||
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| There are sure to be a bunch of other little fixes that this also fixes because it's a pervasive problem that games rely upon! | ||
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| ### Fix ModRM decoding of 3DNow! instructions | ||
| While 3DNow! isn't used in any recent games, to the point that AMD has removed the instruction set from Zen CPU cores, older games still use this | ||
| extension if possible. Turns out we had a gap in our testing infrastructure for when a 3DNow! instruction used the SIB encoding form of the | ||
| instruction. This would result in crashes and misinterpreting of instructions. This will fix some older 32-bit games using 3DNow! and of course we | ||
| added new unittests to our testing infrastructure to make sure it keeps working. | ||
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| ### Fixes H0F3A table decoding | ||
| This fix doesn't affect any known applications, but because of how x86 compilers aggressively pad instruction sizes, this could crop up anywhere | ||
| without us noticing. When the H0F3A instruction table gets decoded, FEX was incorrectly applying the REX_W prefix to instructions that would ignore | ||
| the prefix. Out of all the instructions in the table, only three actually care about the prefix while the others always ignore it. If this padding | ||
| occured then FEX would think it is an unknown instruction and crash. This has now been resolved which should keep us from ever hitting the issue. | ||
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| ### Generate 80-bit SVE loadstores when necessary | ||
| For all the users that have SVE supporting hardware (There aren't a lot of you!), we have added a new optimization that converts two loads or stores | ||
| in to a single 80-bit masked loadstore instruction. While this isn't going to be a huge improvement because this only occurs with x87 code, it's | ||
| another little optimization in the list of things that SVE improves for x86 emulation. | ||
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| ## Increase minimum kernel requirement from 5.0 to 5.15 | ||
| We're moving in to the future with some changes that require increasing our minimum kernel version. Because we were allowing such an old version of | ||
| the Linux kernel, we were hitting some heartburn in some codepaths. In order to make this easier, we are moving up the minimum kernel requirement to | ||
| an LTS release of the kernel released back in 2021 already! We don't expect this to cause too many problems, since this is an kernel supported by | ||
| Ubuntu for 22.04 | ||
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| ## Drop official support for ArchLinux | ||
| Due to a clarification from the ArchLinux team this last month, they are no longer allowing packages in the AUR that don't support x86-64. Due to this | ||
| change and that FEX only supports running on an AArch64 host, they have removed our official packages from AUR. There's nothing that we can do about | ||
| this besides dropping support for ArchLinux. | ||
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| See the [2501 Release Notes](https://github.com/FEX-Emu/FEX/releases/tag/FEX-2501) or the [detailed change log](https://github.com/FEX-Emu/FEX/compare/FEX-2412...FEX-2501) in Github. |