When the alt-stack gets overflown then it is hard to see what went wrong
since the TLS variable is no longer accessible.
Protect the first page that contains the TLS variable.
Fixes#4320
For some reason steamwebhelper is setting a zero length environment
variable. This was causing an assert to be raised early as the web
helper was starting up.
Just stop trying to memcpy the zero length string, gets steamwebhelper
working in the steam beta client again
When running on a system with a 48-bit VA, if FEX does any allocations
between us reserving the upper 128TB and the application running, then
/technically/ we are intersecting with the application's memory region
in the lower 47-bits.
This didn't typically result in any problems due to how ASLR works, but
if we did any large allocations (like #4291 wants with 128MB VMA region)
then these typically get pushed higher in the VA space.
Again not usually a problem, but if you happen to be running an
application that is using MAP_FIXED with hardcoded addresses then this
can stomp over FEX-Emu memory causing problems.
This is what happens with Wine, it reserves the upper-32MB of its 47-bit
VA space, which is /highly/ likely to stomp on FEX memory. In-fact it
likely occurs all the time, we just got lucky with whatever it was
clobbering wasn't used at the time.
On 39-bit VA systems this isn't a problem because the mmap fails
outright with a warning message from WINE.
Because we are already reserving the upper 128TB of VA space, instead
just always enable our allocator and use the regions that were reserved.
We need to be a little bit careful to ensure we don't accidentally
allocate more memory post-reservation but that just requires a small
adjustment to our unique_ptr and constructor for the 64BitAllocator.
This means /all/ FEX-Emu allocations will be in the upper 128TB VA space
when running 64-bit applications on a 48-bit VA system. Which is kind of
nice.
Fixes WINE in #4291 when the allocator stats are bumped to 128MB per
process.
Just four new *at variants of the xattr syscalls.
This will also let us use the *at variants for the non-at versions but I
didn't implement that optimization because this is brand new.
The thread termination callback can be called for other threads in the
process, not just the current one, in which case we cannot call DeinitCRT.
Deinitializing the CRT of another thread would be awkward so just skip that
and accept the small leak for now.
Make sure to pass the clone3 arguments all the way to the fork handler
so it can check the flags. Currently nothing I know of uses fork plus
the new clone3 flags, but it would be hard to see without any logging.
Brought up in #4225 where it had issues with Openat2 which was added in
5.8.
The main driving force around minimum kernel version requirement is that
the lowest kernel version in our CI is 5.15. A benefit to this choice is
that this is an LTS release, which is also what Ubuntu 22.04 is
shipping.
Once the single CI machine is fixed to ship something newer then the
next logical choice would be kernel 6.1 which is also LTS, but until
then just lift it to 5.15. This version was released in October 2021,
and is supported by the kernel developers until 2026. Our previous
minimum of 5.0 was released in March 2019, so a two year leap here.
This removes the openat2 workaround that was necessary to pass our CI
since it is no longer necessary.
Some early FEXServer startup log failures weren't getting printed
correctly. They were going through the LogManager but before FEXServer
setup, or even stderr/stdout logman setup. So they were just getting
written to -1 and failing.
Fixes#4155
This avoids having to do the symlink chasing in GetEmulatedFDPath, since
the kernel does it for us. On top of that, with a merged RootFS
setup, this will correctly handle symlinks from user directories into
the RootFS, fixing wine on Fedora.
- Parse the shebang line properly (use FHU::ParseArgumentsFromString
which is the same code the loader uses)
- Make native-interpreter shebang files work by deferring to the kernel
in that case (previously, they'd get executed through the loader and
it would choke on the architecture of the interpreter)
- Do not use the RootFS-prepended path when executing shebang files. The
loader will prepend that anyway when looking it up, but it needs the
bare guest path so it can pass it as an argument to the interpreter,
which (since it's emulated) will do the lookup through the RootFS.
With a merged RootFS, all binaries are executed through the RootFS. When
executing a binary that is actually a native binary, we want to do so
outside the RootFS. Handle this by stripping the RootFS prefix in that
case.
If a RootFS symlink links to an absolute path within the RootFS, we need
to strip the RootFS prefix. This would not normally happen with a plain
RootFS, but it can happen if /proc is mounted within the RootFS.
If there's a symlink to / within the RootFS, don't attempt to follow it,
since that will end up trying to look up the empty string within the
RootFS (which is not legal). Just return the symlink.
To locate whether a path is in the emulated list, EmulatedFDManager::OpenAt()
attemps to resolve the path. realpath() ends up calling readlinkat() on
every path component, which is a lot of syscalls for every open()
variant syscall. It also makes interaction with the rootfs complex and
error-prone.
There's a much easier way to do this: We just open the file without
emulation and check its real path via get_fdpath(). This is just one
readlink() syscall per open, instead of one per path component. If the
file turns out to be emulated (uncommon case), we swap out the fds.
This also decouples EmulatedFDManager from guest path resolution
entirely, so it will never fall out of sync with the RootFS logic.
This is going to get used by gdbserver soon for ensuring memory accesses
are fault safe, because it tries to read outside of correct memory
bounds at times.
When an SMC trap happens: reconstruct the context before the SMC write
then compile the write as a single instruction block to reduce it to
regular SMC. SMC where the writing instruction is the instruction being
patched will hit the signal handler at most twice: the 1st will trigger
the write to be compiled as a single instuction block, the 2nd will
detect inline SMC of a single instruction block and then just take the
usual invalidate+reprotect+continue step, avoiding a potential infinite
loop of recompilation.
Ryan Houdek