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.
Fixes#2095
std::random_device can fail to find a random source and throw an assert
during initialization.
The constructor allows you to provide a token string to select an
explicit random source, but this is c++ library specific and will still
assert if the source isn't found. Also specific tokens are very much
target and library specific, so it is unsafe to use.
In the libstdc++ case, the default implementation will try to open
`/dev/urandom` which might not be available on all targets.
Instead of relying on this C++ object, use the `getrandom` syscall
directly to generate our RNG used in the ELFCodeLoader.
Resolves any sort of asserting case, blocks on RNG generation, and is
guaranteed to be available since this syscall has been available since a
very old kernel version.
`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 is the last remaining auxv value that we were missing.
This requires a little bit of setup to match what we are doing in
FEXCore's Dispatcher.
This only tracks how much space is required by the kernel to store its
required state.
When we are installed as a binfmt_misc handler the Linux kernel will
assign us AT_SECURE for setuid binaries.
Ensure we are passing this through for any application that will end up
needing it.
AT_SYSINFO points to the vsyscall location that the kernel provides.
This AUXV value isn't used on x86-64.
If we have VDSO installed then we can use the one provided from there,
otherwise we need to provide a code page.
It seems like some behaviour changed with glibc provided in Ubuntu 22.10
that it now requires AT_SYSINFO.
Fixes wine 7.0 execution inside the Ubuntu 22.10 rootfs.
This is a tricky situation that wine-preloader allocates the lower
32MB of stack space through fixed address mmap with MAP_FIXED.
They can't use mmap with an address hint nor MAP_FIXED_NOREPLACE because
it changes behaviour. mmap won't give you the allocation inside the
stack space even if you check `/proc/self/maps` that space isn't yet
allocated. The growable space of the stack blocks those allocations.
So the wine peeps might be SOL if they actually require this allocation
to exist.
To replicate this, allocate the application stack at the same location using an address hint.
This will give us the correct region on a 48-bit VA system, while also
letting it select a different region on a 36-bit VA system.
Implements AT_PLATFORM: Ends up being `i686` or `x86_64` depending on
ELF arch
Implements AT_HWCAP and AT_HWCAP2
AT_HWCAP is just CPUID function 01h EDX result
AT_HWCAP2 only has two defined bits in it, which we don't support
either.
Implements AT_RANDOM
Previously we were just sticking hardcoded values in to this.
Now we pass along the host's AT_RANDOM, or we generate our own if that
doesn't exist
Fixes#788
The kernel maps the primary ELF with a hint to some place *near* the
middle of the virtual address space. While the interpreter stays at the
top of the address space.
This also adds ASLR to the ELF loading, with a define for debugging and
testing purposes.
Requires both #2013 and #2014 merged first.
Specifically fixes /sbin/ldconfig.
Fixes 8df7c2d84f
Fixes Steam launching
I failed to test ELF files that are dynamic with no interpreter here, so
EntryPoint ended up being set to zero, which results in an instant
crash.
Ensure these values are set correctly after the primary ELF and
interpreter are loaded so starting RIP is correct.
Instead of mapping to find a range, unmapping, and then submapping
inside of it.
Map once, then mmap with MAP_FIXED to overwrite the mapping.
This fixes an issue where if you enabled ASAN then it would stick
additional mappings inbetween where we want to map. Thus breaking asan.
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.
This is just a memory leak waiting to happen.
Only the primary thread in an application really should have this set
since the kernel cleans it up.
We only ever allocate the primary thread of the guest application then
every host thread's stack on top of that. It's up to the guest when it
is cloning to set up new stack pointers, we don't manage that.
We are already allocating the first thread's size at the soft stack
limit with RLIMIT_STACK anyway.
Fixes#1556
Fixes executing musl applications with the dynamic linker.
It was using the main executable's p_offset instead of the
interpreter's.
Wasn't a problem with glibc since it uses a different symbol to find the
base (Don't ask me why it does this).
musl dynamic linker on the other hand just uses AT_BASE directly and
since it was calculated incorrectly it was crashing.
Testing application was `ls` which had a p_offset of 0x40, so it would
try and read some values from AT_BASE, starting at an offset below where
it was mapped.
If the user passes in an absolute path then check to see if it exists in
the rootfs before executing.
Useful for launching applications directly out of the rootfs with
FEXInterpreter.
In the case that the absolute path doesn't exist in the rootfs then
fallback to the host system as usual
Adds a header only include utility folder that can be included from
everywhere.
Contains syscall helpers for older glibc and defines for older Linux
uapi headers missing some defines.
Each section map invocation was clearing the sections pointer, meaning
we only ever had one section in the vector.
We want to keep all of the sections around from the ELFCodeLoader.
Fixes a bug where we were effectively never catching any code segments
from the executable passed in.
With a DYN ELF in most cases the first program header will be at offset
0.
This isn't always true though, in the case of `micro` the first program
header is at a 4MB offset.
This was causing us to miscalculate the size of ELF in memory, which was
causing BRK to intersect with the ELF on allocation.
This would cause ELF loading to fail and then us to close in some cases.
Also makes sure to pass -1 as FD in mmap with anonymous to match.
This lets us support the final two flags in binfmt_misc that we needed.
1) Support open_binary
2) Support preserve
1)
We already supported the credentials flag, which implied open_binary, but we weren't handling half of it.
With the open_binary flag, the Linux kernel passes us the executable in an FD instead of as a pathname.
This can be found inside of auxv on startup, inside of AT_EXECFD.
If AT_EXECFD is available then we prioritize using that instead of the pathname passed in.
This fixes a potential permissions issue where an executable is executed without read permissions.
2)
The preserve flag has the Linux kernel preserve the original argv[0] that was passed to the application.
Prior to supporting this flag, the kernel would provide us with a resolved program path.
This can happen in the instance where something like `blah` resolves to `/usr/loca/bin/blah` which
isn't what the user originally typed.
This works around this problem by handing the interpreter both the resolved path and the original typed path.
Alongside open_binary, we can just use the FD passed in instead of the resolved path, this means
we can just drop the argv[0] for the guest (which is the kernel resolved path) and pass through arguments
unmangled.
We do have to make a minor assumption here that if we are using EXECFD that we assume preserve.
It isn't until kernel v5.12 that we can actually check AT_FLAGS to see if that was true.
gzip ships a PT_LOAD program section without a file size and only a memory size.
In the case of a zero file size PT_LOAD then return success immediately in this section loader.
This fixes Steam using gzip to package up crash logs
Only the frontends need to deal with ELF files specifically.
The backend doesn't need to be aware of them at all.
Since the ELF handling is the frontend's responsibility, move all the code to the frontend.
Instead of forcing a fixed offset for the stack. Allow it to get placed automatically.
64-bit was already doing this; Now we can also do it in 32-bit.
This is possible because the mapper that is mapping the code will always map in the 32-bit space
for a 32-bit guest.
This class is partially allocated on either side of the allocator fence.
Moves `Sections` over to a unique_ptr so we can clear this variable prior to shutdown.
The rest of the class is allocated prior to switching to FEX allocator
Ryan Houdek