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https://github.com/sunfishcode/eyra
Rust programs written entirely in Rust
https://github.com/sunfishcode/eyra
linux rust
Last synced: 27 days ago
JSON representation
Rust programs written entirely in Rust
- Host: GitHub
- URL: https://github.com/sunfishcode/eyra
- Owner: sunfishcode
- License: other
- Created: 2023-09-22T20:09:24.000Z (about 1 year ago)
- Default Branch: main
- Last Pushed: 2024-10-10T18:16:23.000Z (about 1 month ago)
- Last Synced: 2024-10-10T18:28:16.955Z (about 1 month ago)
- Topics: linux, rust
- Language: Rust
- Homepage:
- Size: 158 KB
- Stars: 755
- Watchers: 15
- Forks: 12
- Open Issues: 6
-
Metadata Files:
- Readme: README.md
- License: LICENSE-APACHE
- Code of conduct: CODE_OF_CONDUCT.md
Awesome Lists containing this project
README
Eyra
Rust programs written entirely in Rust
Eyra is a package that supports building Rust programs implemented entirely
in Rust.
It uses [Origin] for program and thread startup and shutdown, and [c-gull] for
ABI-compatible libc function implementations. It currently works on
Nightly Rust on Linux on x86-64, x86, aarch64, and riscv64.
[Origin]: https://github.com/sunfishcode/origin#readme
[c-gull]: https://github.com/sunfishcode/c-ward/tree/main/c-gull#readme
## Quick start
Running a Rust program under Eyra needs two steps. First, a Cargo.toml
dependency, which we can add with:
```console
cargo add eyra --rename=std
```
And, a build.rs file to add `-nostartfiles` to the link flags to disable the
host startup code, so that Eyra can provide its own. build.rs:
```rust,no_run
fn main() {
println!("cargo:rustc-link-arg=-nostartfiles");
}
```
With that, `cargo build`, `cargo run`, `cargo test` (with Nightly) and so on
will work normally with any `*-unknown-linux-gnu*` target.
Under the covers, it's using [Origin] to start and stop the program, [c-ward]
to handle libc calls from `std`, and [rustix] to do the printing, so it's
completely implemented in Rust.
## Examples
For an example of the above steps, check out [this hello world example].
Other examples include
- [enabling LTO],
- [using min-sized-rust technique to produce small binaries], and
- [adding Eyra as an optional dependency].
- [building a program completely from source].
[this hello world example]: https://github.com/sunfishcode/eyra/tree/main/example-crates/hello-world#readme
[enabling LTO]: https://github.com/sunfishcode/eyra/tree/main/example-crates/hello-world-lto#readme
[using min-sized-rust technique to produce small binaries]: https://github.com/sunfishcode/eyra/tree/main/example-crates/hello-world-small#readme
[adding Eyra as an optional dependency]: https://github.com/sunfishcode/eyra/tree/main/example-crates/eyra-optional-example#readme
[building a program completely from source]: https://github.com/sunfishcode/eyra/tree/main/example-crates/all-from-source#readme
## Why?
Why use Eyra?
- It fixes Rust's [`set_var` unsoundness issue]. The environment-variable
implementation leaks memory internally (it is optional, but enabled by
default), so `setenv` etc. are thread-safe.
- [Whole-program LTO], including the libc. This sometimes produces smaller
static binaries, and sometimes produces faster code (though on the other
hand, sometimes it doesn't, though on the first hand, there are still
low-hanging fruit, so consider trying it and filing issues).
For even more code-size reductions, see the techniques in
[the hello-world-small example].
- Support for compiling programs with alternate calling conventions, using
[Eyra and `-Zbuild-std`] to [build a program completely from source].
- [Fully static linking] that supports the platform NSS/DNS config. "Is such
a thing even possible?", "Yes it is."
- Or, bring your own reason! Be creative and do your own thing, and tell us
about it!
Why not use Eyra?
- It's not as mature as the major libc implementations.
- It's not as complete as the major libc implementations. It can run most Rust
code, and some popular C libraries, but still lacks a lot of things used by
typical C code.
- It currently depends on Rust Nightly and only runs on Linux, and currently
only on x86-64, x86, aarch64, and riscv64.
- It can't currently run under Miri because Miri doesn't currently recognize
syscalls made from assembly code. That said, Eyra does strive to adhere to
strict provenance and to avoid undefined behavior throughout, so if Miri
were to gain support for such syscalls, Eyra should be well-positioned.
- No support for dynamic linking.
It might seem like "memory safety" might be a reason to use Eyra, and Eyra does
have a lot of code written in safe Rust, so it does benefit some from Rust's
memory safety. However, Eyra also has a lot of `unsafe` code (it's unavoidable
for implementing a libc). Until this code has been more throughly proven, it's
not realistic to consider it more safe than mature C code.
[Whole-program LTO]: https://github.com/sunfishcode/eyra/tree/main/example-crates/hello-world-lto#readme
[`set_var` unsoundness issue]: https://github.com/rust-lang/rust/issues/27970
[Eyra and `-Zbuild-std`]: #compatibility-with--zbuild-std
[Fully static linking]: #fully-static-linking
## Fully static linking
Eyra executables don't depend on any dynamic libraries, however by default they
do still depend on a dynamic linker (eg. "/lib64/ld-linux-x86-64.so.2").
For fully static linking, there are currently two options:
- Build with
`RUSTFLAGS=-C target-feature=+crt-static -C relocation-model=static`. This
disables Position-Independent Executable (PIE) mode, which is
straightforward, however it loses the security benefits of
Address-Space Layout Randomization (ASLR).
- Build with `RUSTFLAGS=-C target-feature=+crt-static` and enable the
`experimental-relocate` feature. This allows PIE mode and ASLR to work,
however it does so by enabling an experimental implementation of
relocations. This code seems to be working in practice so far, however it
involves Rust code patching itself as it runs, which is outside of any Rust
semantics.
## Optional logging
Eyra has a `log` feature to enable Rust `log` tracing of program and thread
startup and shutdown, and an `env_logger` feature to install `env_logger`
as the logger, which can be enabled in Cargo.toml:
```toml
[dependencies]
std = { package = "eyra", version = "", features = ["log", "env_logger"] }
```
With this, and setting the `RUST_LOG` environment variable to "trace", the
hello world program output like this:
```console
[TRACE origin::program] Program started
[TRACE origin::thread] Main Thread[51383] initialized
[TRACE origin::program] Calling `.init_array`-registered function `0x55e86306bb80(1, 0x7ffd0f76aad8, 0x7ffd0f76aae8)`
[TRACE origin::program] Calling `origin_main(1, 0x7ffd0f76aad8, 0x7ffd0f76aae8)`
Hello, world!
[TRACE origin::program] `origin_main` returned `0`
[TRACE origin::thread] Thread[51383] calling `at_thread_exit`-registered function
[TRACE origin::thread] Thread[51383] calling `at_thread_exit`-registered function
[TRACE origin::program] Program exiting with status `0`
```
## Compatibility with `-Zbuild-std`
Eyra works with `-Zbuild-std`, however the `--rename=std` trick used above
doesn't work, so it's necessary to instead use this `cargo add` invocation:
```console
cargo add eyra
```
and to also add this line to the program's `main.rs` file:
```rust,no_run
extern crate eyra;
```
to ensure that the Eyra libraries are linked in.
## Reducing code size
Eyra can be used with the techniques in [min-sized-rust] to produce very
small statically-linked binaries. Check out [the hello-world-small example].
[min-sized-rust]: https://github.com/johnthagen/min-sized-rust
[the hello-world-small example]: https://github.com/sunfishcode/eyra/tree/main/example-crates/hello-world-small/#readme
## Relationship to Mustang
Eyra is similar to [Mustang] and uses the same underlying code, but instead
of using a custom target and -Z build-std, Eyra just needs users to add
`-nostartfiles` to their link line, such as via build.rs in the example.
Like Mustang, Eyra currently runs on Nightly Rust on Linux on x86-64, x86,
aarch64, and riscv64. It aims to support all Linux versions
[supported by Rust], though at this time it's only tested on relatively recent
versions. It's complete enough to run:
- [ripgrep](https://github.com/sunfishcode/ripgrep/tree/eyra)
- [coreutils](https://github.com/sunfishcode/coreutils/tree/eyra),
including the "unix" feature set
- [async-std](https://github.com/sunfishcode/tide/tree/eyra)
- [tokio](https://github.com/sunfishcode/tokio/tree/eyra)
- [bat](https://github.com/sunfishcode/bat/tree/eyra), including git
support with libgit2
- [cargo-watch](https://github.com/sunfishcode/cargo-watch/tree/eyra)
- [nushell](https://github.com/sunfishcode/nushell/tree/eyra), with a
few workarounds
## Compiling C programs
Eyra can also be compiled into a libc.a that can be used to compile C
programs; see the [eyra-c] repository.
[eyra-c]: https://github.com/sunfishcode/eyra-c
## Design philosophy
Eyra and the libraries it uses have some design goals.
### Normal Rust, all the way down
Sometimes in libc implementation code, there's a temptation to say "it's ok
if some things are technically Undefined Behavior, because this is Low Level
Code and We Know What We're Doing".
Origin, c-scape, c-gull, rustix, and the others strive to resist this
temptation, and follow the Rust rules, including strict provenance, I/O safety,
and all the rest, all the way down to the syscalls.
It's just normal Rust code, as far down as we can go in userspace, and when we
eventually do have to switch to inline asm, we do as little of it as we can.
Currently there is only one known place where this goal is not achieved. In a
"static PIE" executable (eg. built with
`RUSTFLAGS="-C target-feature=+crt-static"`), the dynamic linker isn't used,
so the executable has to handle all its relocations itself. However, that
means storing to memory locations that wouldn't otherwise be considered
mutable. Origin's code for doing this is currently disabled by default, and
can be enabled with the "experimental-relocate" cargo feature.
### C compatibility as a layer on top of Rust, not vice versa
Eyra is built on a collection of Rust crates with idiomatic Rust APIs, and two
crates, c-scape and c-gull, which are relatively thin layers on top that
implement the libc-compatible C ABI.
It's sometimes more work to write the code as separate layers like this, but
it has the advantage of clearly separating out the `unsafe` associated with
things like C pointers and strings in libc APIs from the essential `unsafe`
needed to implement things like system calls, thread primitives, and other
features. And it means that Rust programs that don't want to go through the C
compatibility layer can use the underlying crates directly.
[Mustang]: https://github.com/sunfishcode/mustang#readme
[Origin]: https://github.com/sunfishcode/origin#readme
[c-ward]: https://github.com/sunfishcode/c-ward#readme
[rustix]: https://github.com/bytecodealliance/rustix#readme
[supported by Rust]: https://doc.rust-lang.org/nightly/rustc/platform-support.html
[build a program completely from source]: https://github.com/sunfishcode/eyra/tree/main/example-crates/all-from-source#readme