Fixes#2136
This is a fairly tricky edge case to support with FEX.
If execveat is used with AT_EMPTY_PATH then the application can pass an
FD to execve instead of a filename. This includes FDs that have been
deleted from the disk so the child process can't open it by filename
anymore.
To work around this limitation, we need to pass the FD to the new FEX
process and open it directly, similar to how binfmt_misc works with FDs.
The FD will get passed through environment variables, which the new
process will check for and then remove the variable from the
environment.
Lots of prickly edge cases to support here.
Without binfmt_misc:
- Passes the FD to FEXLoader directly.
- Requires duplicating the FD if it has O_CLOEXEC on the FD.
With binfmt_misc:
- Shebang file, pass directly to FEXLoader, just like without binfmt.
- x86 ELF Files, rely on the kernel's binfmt_misc support here.
- Unsupported ELF files, let kernel handle it through binfmt_misc
Argument handling:
- The application can pass in no arguments.
- Means our application configurations were failing to find a config
- Also various checks in the frontend were failing.
- If opened through an FD, find the symlink for that FD for the
application configuration instead.
Side note:
Fixed a performance issue in execve where when we were checking for file
format support. Either ELF or Shebang files, we were reading the /whole/
file upfront. We only need to read a header worth of ELF files, and only
257 bytes if it is potentially a shebang file. Should dramatically
reduce some application's execve times.
`GetEmulatedPath` and `OpenAt` are called a /lot/ in applications.
std::filesystem::path handling here is quite heavy and costly for what
we are trying to achieve.
Remove this usage and instead use lstat, access, and readlink directly
which is a heck of a lot faster.
In particular this helps out pressure-vessel, shaving off launch times
by 1-2 seconds.
Going from ~22 seconds down to ~20 seconds.
This will be useful for keying specific executables to steamids.
This is sadly required because a bunch of games end up naming themselves
"game.exe" so we can't safely enable thunks for all things shipping a
generic name.
Segment registers are indexed significantly more than they are changed.
Pay the cost of indexing during the set and store rather than the per
register index.
Should be a fairly significant performance improvement for 32-bit
applications. At least on hardware that doesn't have a data dependent
prefetcher.
Breaks Steam atm and isn't clean.
Previously the config options could only have ever enabled thunks rather than
disable them.
Now sort the code so it can enable thunks, then following configs can
redisable them. Allowing testing with global thunks enabled and
disabling problematic applications.
Also sorts the "ThunkConfigFile" config as lower priority than the
application configs. I wasn't thinking about ordering that hard for
these five configuration paths, but application configs should be higher
priority in this case.
These should be using the real syscalls, not our provided allocators.
While not a problem currently since these redirect to host mmap and
munmap, it will become an issue once we have an allocator that lives
outside of x86-64 space.
Termux uses defines for these, so our token pasting fails, but we also
still want to use their define so we can fall down their emulation
library whenever possible.
Prefix an underscore to be able to use both our number definitions and
their defines in the same file.
Previously in order to enable thunks, we needed an independent
description file of which thunks to be enabled. This is nice for quickly
testing out new games by setting `FEX_THUNKCONFIG` environment variable.
For users that just want to enable thunks this is an unwieldy
indirection that doesn't make much sense at a glance.
Previously this meant you needed two files as an example:
```
ryanh@ubuntu-linux-20-04-desktop:~/.fex-emu$ cat thunks.json
{
"ThunksDB": {
"GL": 1,
"Vulkan": 1
}
}
ryanh@ubuntu-linux-20-04-desktop:~/.fex-emu$ cat AppConfig/EnderLiliesSteam-Linux-Shipping.json
{
"Config": {
"ThunkConfig":"~\/.fex-emu\/thunks.json"
}
}
```
Instead of this unwieldy redirection just support `ThunksDB` json
directly in the AppConfig.
```
ryanh@ubuntu-linux-20-04-desktop:~/.fex-emu$ cat AppConfig/EnderLiliesSteam-Linux-Shipping.json
{
"Config": {
<...>
},
"ThunksDB": {
"GL": 1,
"Vulkan": 1
}
}
```
As can be seen this makes this significantly easier for new users
getting in to thunks. Depending on which path to enable thunks the user
is more comfortable with, they can still enable them using the
`ThunkConfig` option or embedding directly in the application
configuration.
Additionally this removes the older non-ThunksDB path to loading thunks.
All users of it have moved on to using ThunksDB.
Arm64 doesn't have the classic getdents syscall, only getdents64.
Old glibc versions (like 2.17) don't support getdents64
This fixes 64-bit ls with a centos 7 rootfs. Likely also fixes some other very
old applications.
Packing differences between 32-bit and 64-bit getdents means we need to
template this between the two types, otherwise it's quite similar.
No known applications rely on the 32-bit getdents but worked with test
applications.
It's common for Linux applications that use close_range to pass in ~0 as
the last FD. This was causing FEX to spin from [2, ~0U] in this loop.
This would take /forever/ to run.
Change over to an ordered map and use the map's range searching and
ranged erase to more quickly remove these elements.
Fixes a hang that occurs with first time Steam setup in
steam-linux-runtime heavy application `steam-runtime-identify-library-abi`.
glibc lazily initializes the SETXID signal handler until first thread
creation.
Once we create our first pthread, steal it back from GLIBC after the
fact.
Fixes SOMA again.
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.
Even though this member isn't used on ARM, the member is still there.
Fixes crashing in optimized builds and also makes unity's garbage
collector significantly more stable
Currently thunk prefixes are mutally exclusive. No thunks database path
can currently have more than one prefix. If this is necessary then we
can add it in the future.
Most minor of optimizations here, we only scan the string once to find a
prefix, instead of searching for it on all four prefix replacements.
We weren't adjusting the guest stack size when using clone3.
If the clone comes from CLONE3 then we need to offset the RSP by the
provided stack size.
This also translates to fork/vfork through clone, so make sure to adjust
stack in that case as well.
Fixes Ender Lilies crashing with Ubuntu 22.04 rootfs
DRM ioctls are taking advantage of the fact that any ioctl structure
that is passed in to the kernel smaller than the expected value will
zero out the remaining members of the structure.
Some more ioctls coming down the pipe will also abuse this, so we might
as well as get started with the v3d ioctl that requires it.
Due to how this works, the kernel knows how big an ioctl structure
should be and if the userspace passes in a smaller struct, it will
memset the remaining size to zero.
std::filesystem::canonical is very heavyweight and walks the full path
to ensure that each folder in the path is not a symlink.
eg:
```
readlink("/proc", 0x7ffd5646e210, 1023) = -1 EINVAL (Invalid argument)
readlink("/proc/self", "880556", 1023) = 6
readlink("/proc/880556", 0x7ffd5646e210, 1023) = -1 EINVAL (Invalid argument)
readlink("/proc/880556/fd", 0x7ffd5646e210, 1023) = -1 EINVAL (Invalid argument)
readlink("/proc/880556/fd/5", "/home/ryanh/.fex-emu/RootFS/Ubuntu_22_04/usr/lib/x86_64-linux-gnu/ld-linux-x86-6"..., 1023) = 86
readlink("/home", 0x7ffd5646e210, 1023) = -1 EINVAL (Invalid argument)
readlink("/home/ryanh", 0x7ffd5646e210, 1023) = -1 EINVAL (Invalid argument)
readlink("/home/ryanh/.fex-emu", 0x7ffd5646e210, 1023) = -1 EINVAL (Invalid argument)
readlink("/home/ryanh/.fex-emu/RootFS", 0x7ffd5646e210, 1023) = -1 EINVAL (Invalid argument)
readlink("/home/ryanh/.fex-emu/RootFS/Ubuntu_22_04", 0x7ffd5646e210, 1023) = -1 EINVAL (Invalid argument)
readlink("/home/ryanh/.fex-emu/RootFS/Ubuntu_22_04/usr", 0x7ffd5646e210, 1023) = -1 EINVAL (Invalid argument)
readlink("/home/ryanh/.fex-emu/RootFS/Ubuntu_22_04/usr/lib", 0x7ffd5646e210, 1023) = -1 EINVAL (Invalid argument)
readlink("/home/ryanh/.fex-emu/RootFS/Ubuntu_22_04/usr/lib/x86_64-linux-gnu", 0x7ffd5646e210, 1023) = -1 EINVAL (Invalid argument)
readlink("/home/ryanh/.fex-emu/RootFS/Ubuntu_22_04/usr/lib/x86_64-linux-gnu/ld-linux-x86-64.so.2", 0x7ffd5646e210, 1023) = -1 EINVAL (Invalid argument)
```
This is what was occuring for every single mmap that occurs. /really/
adding to the time for the syscall to take.
This also happens on a couple of other syscalls which are using this new
path now.
The primary reason why this works is that we know that every entry in
`/proc/self/fd/` is a symlink. So instead of asking for canonical, we
can just read the symlink and this will redirect us to the canonical
path.
So this previous example goes from 14 syscalls down to 1.
eg:
```
readlinkat(AT_FDCWD, "/proc/self/fd/5", "/home/ryanh/.fex-emu/RootFS/Ubuntu_22_04/usr/lib/x86_64-linux-gnu/ld-linux-x86-6"..., 4096) = 86
```
While this is only a minor improvement in the "typical" operating environment,
this significantly improves performance of FEX under proot or if the
rootfs lives on a network share.
Instead of duplicating prefixes in the ThunksDB json file even more,
just do a prefix replacement when the thunks database is being parsed.
Changes the JSON overlay arrays over to @PREFIX@ and reduce the
duplication.
Adds support for the pressure-vessel prefix `/usr/lib/pressure-vessel/overrides/lib`
This gets thunks ready for running under pressure-vessel, once vulkan
thunking switches from device libraries to the vulkan loader it should
just work.
32-bit allocations were scanning for available pages by shifting by the
length of allocation. This is incorrect since large allocations would
then only scan through the region in very large chunks. Especially if
MAP_32BIT was present. Instead scan by page size to ensure better fit.
This fixes X-Plane 11.
Also ensure we don't try to munmap a range unless the result is
MAP_FAILED, noticed we were trying to munmap ~0ULL
Ryan Houdek