When a syscall from the *at series is provided an FD but the path is
absolute then dirfd should be ignored. We weren't correctly doing this.
Now if the path is absolute, but set the argument to the special
AT_FDCWD..
Fixes#3204
This is a new procfs symlink path that changes behaviour of binfmt_misc
when exposed. We need to check both procfs/exe and procfs/interpreter
and see if they exist AND also differ.
Once/if they do then we can disable a bunch of checking of paths once
they do. The fallback when none of this is supported has the same
behaviour has previously where it still does all the regular checking.
During binfmt_misc install cmake will check the kernel version for the
raw binfmt_misc writing. Which will never pass until we have a real
kernel version that it is upstreamed in.
For update-binfmts we add a new optional argument where the tool will
drop the flag if the host kernel version isn't new enough to handle the
option.
Instead of allocating a temporary copy of the string, return a view of
it instead. Should improve the performance of system calls that take
file paths. Since it was allocating a string for every single syscall
that uses them in this case.
Removes the @PREFIX_ARCH@ replacement string in the thunks path.
The library prefix paths now get generated upfront and everything gets
replaced to handle the differences between multiarch distros.
Fixes Thunks on Arch and Fedora.
Fixes a spurious `No such file or directory` error when `ls` is trying
to query a path's xattributes that come from the emulated rootfs.
These syscalls don't support the *at variants, so it can't use the optimized `GetEmulatedFDPath` implementation.
It must also return an error on a found file path, which makes their
implementation be slightly different than the other user of of
`GetEmulatedPath`. In the case of error, it must only return an error
from the emulated path if it is /not/ ENOENT.
Before:
```
$ FEXInterpreter /usr/bin/ls -alth /usr/bin/wine-stable
/usr/bin/ls: /usr/bin/wine-stable: No such file or directory
-rwxr-xr-x 1 ryanh ryanh 1.1K Sep 24 2022 /usr/bin/wine-stable
```
After:
```
$ FEXInterpreter /usr/bin/ls -alth /usr/bin/wine-stable
-rwxr-xr-x 1 ryanh ryanh 1.1K Sep 24 2022 /usr/bin/wine-stable
```
In the case that the symlink following would immediately fail (Due to
the first query not existing or not being a symlink), then FEX would
immediately return the first query. Then the resulting syscall using
this result would try to run the syscall on that file, immediately
error, and try again on the file outside of the rootfs. This gives us
three syscalls for the price of one.
This adds an additional syscall cost to every syscall that that takes
the `FollowSymlink` code path, which is quite a few.
Instead now, check to see if the filepath exists at all, and if the
filepath doesn't even exist for the first fstatat, return a `NoEntry`
immediately. This will cause the resulting syscall waiting for the
result to skip the EmulatedFDPath check and run regular syscall.
If the filepath is symlink it will still loop to track through the
entire symlink tree to find the one that is in the rootfs.
If the filepath is just a file, then the `IsLink` step will fail,
returning the filepath to the file inside of the rootfs. (Getting this
step wrong will make wine/proton immediately break).
With this resolved, this converts a lot of three syscall operations down
to two.
This lets all the path generation for the config to be in the frontend.
This then informs FEXCore where things should live.
This is for llvm-mingw. While paths aren't quite generated correctly,
this gets the code closer to compiling.
Ryan Houdek