As a start, the port uses the simplest possible configuration (no jemalloc, abort on panic)
and makes use of existing Unix-specific code wherever possible.
It adds targets for x86_64 (current main HermitCore platform) and aarch64 (HermitCore platform
under development).
Together with the patches to "liblibc" and "llvm", this enables HermitCore applications to be
written in Rust.
Remove unnecessary stat64 pointer casts
In effect, these just casted `&mut stat64` to `*mut stat64`, twice.
That's harmless, but it masked a problem when this was copied to new
code calling `fstatat`, which takes a pointer to `struct stat`. That
will be fixed by #51785, but let's remove the unnecessary casts here
too.
Fix possibly endless loop in ReadDir iterator
Certain directories in `/proc` can cause the `ReadDir` iterator to loop indefinitely. We get an error code (22) when calling libc's `readdir_r` on these directories, but `entry_ptr` is `NULL` at the same time, signalling the end of the directory stream.
This change introduces an internal state to the iterator such that the `Some(Err(..))` value will only be returned once when calling `next`. Subsequent calls will return `None`.
fixes#50619
In effect, these just casted `&mut stat64` to `*mut stat64`, twice.
That's harmless, but it masked a problem when this was copied to new
code calling `fstatat`, which takes a pointer to `struct stat`. That
will be fixed by #51785, but let's remove the unnecessary casts here
too.
Certain directories in `/proc` can cause the `ReadDir`
iterator to loop indefinitely. We get an error code (22) when
calling libc's `readdir_r` on these directories, but `entry_ptr`
is `NULL` at the same time, signalling the end of the directory
stream.
This change introduces an internal state to the iterator such
that the `Some(Err(..))` value will only be returned once when
calling `next`. Subsequent calls will return `None`.
fixes#50619
fs: copy: Use File::set_permissions instead of fs::set_permissions
We already got the open file descriptor at this point.
Don't make the kernel resolve the path again.
fs: copy: use copy_file_range on Linux
Linux 4.5 introduced a new system call [copy_file_range](http://man7.org/linux/man-pages/man2/copy_file_range.2.html) to copy data from one file to another.
This PR uses the new system call (if available). This has several advantages:
1. No need to constantly copy data from userspace to kernel space, if the buffer is small or the file is large
2. On some filesystems, like BTRFS, the kernel can leverage internal fs mechanisms for huge performance gains
3. Filesystems on the network dont need to copy data between the host and the client machine (they have to in the current read/write implementation)
I have created a small library that also implements the new system call for some huge performance gains here: https://github.com/nicokoch/fastcopy
Benchmark results are in the README
Previously, every `open64` was accompanied by a `ioctl(…, FIOCLEX)`,
because some old Linux version would ignore the `O_CLOEXEC` flag we pass
to the `open64` function.
Now, we check whether the `CLOEXEC` flag is set on the first file we
open – if it is, we won't do extra syscalls for every opened file. If it
is not set, we fall back to the old behavior of unconditionally calling
`ioctl(…, FIOCLEX)` on newly opened files.
On old Linuxes, this amounts to one extra syscall per process, namely
the `fcntl(…, F_GETFD)` call to check the `CLOEXEC` flag.
On new Linuxes, this reduces the number of syscalls per opened file by
one, except for the first file, where it does the same number of
syscalls as before (`fcntl(…, F_GETFD)` to check the flag instead of
`ioctl(…, FIOCLEX)` to set it).
Most users would expect set_permissions(Metadata.permissions()) to be
non-destructive. While we can't guarantee this, we can at least pass
the needed info to chmod.
Also update the PermissionsExt documentation to disambiguate what it
contains, and to refer to the underlying value as `st_mode` rather than
its type `mode_t`.
Closes#44147
This commit adds the needed modifications to compile the std crate
for the L4 Runtime environment (L4Re).
A target for the L4Re was introduced in commit:
c151220a84
In many aspects implementations for linux also apply for the L4Re
microkernel.
Two uncommon characteristics had to be resolved:
* L4Re has no network funktionality
* L4Re has a maximum stacksize of 1Mb for threads
Co-authored-by: Sebastian Humenda <sebastian.humenda@tu-dresden.de>
The readdir_r function is deprecated on newer Posix systems because of
various problems, and not implemented at all for Fuchsia. There are
already implementations using both, and this patch switches Fuchsia
over to the readdir-based one.
Fixes#40021 for Fuchsia, but that issue also contains discussion of
what should happen for other Posix systems.
On unix like systems, the underlying file corresponding to any given path may
change at any time. This function makes it possible to set the permissions of
the a file corresponding to a `File` object even if its path changes.
The DirEntryExt::ino() implementation was omitted from the first
iteration of this patch, because a dependency needed to be
configured. The fix is straightforward enough.
It is good practice to implement Debug for public types, and
indicating what directory you're reading seems useful.
Signed-off-by: David Henningsson <diwic@ubuntu.com>
These functions allow to read from and write to a file in one atomic
action from multiple threads, avoiding the race between the seek and the
read.
The functions are named `{read,write}_at` on non-Windows (which don't
change the file cursor), and `seek_{read,write}` on Windows (which
change the file cursor).
std: fix `readdir` errors for solaris
A `NULL` from `readdir` could be the end of stream or an error. The only
way to know is to check `errno`, so it must be set to a known value first,
like a 0 that POSIX will never use.
This currently only matters for solaris targets, as the other unix platforms
are using `readdir_r` with a direct error return indication. However, this is
getting deprecated (#34668) so they should all eventually switch to `readdir`.
This PR adds `set_errno`, uses it to clear the value before calling `readdir`,
then checks it again after to see the reason for a `NULL`. A few other small
fixes are included just to get solaris compiling at all.
I couldn't get cross-compilation completely going, so I don't have a good way
to test this beyond a smoke-test cargo build of std. I'd appreciate input from
someone more familiar with solaris -- cc @nbaksalyar?
