rust/library/std/src/sys/mod.rs

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//! Platform-dependent platform abstraction.
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//!
//! The `std::sys` module is the abstracted interface through which
//! `std` talks to the underlying operating system. It has different
//! implementations for different operating system families, today
//! just Unix and Windows, and initial support for Redox.
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//!
//! The centralization of platform-specific code in this module is
//! enforced by the "platform abstraction layer" tidy script in
//! `tools/tidy/src/pal.rs`.
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//!
//! This module is closely related to the platform-independent system
//! integration code in `std::sys_common`. See that module's
//! documentation for details.
//!
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//! In the future it would be desirable for the independent
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//! implementations of this module to be extracted to their own crates
//! that `std` can link to, thus enabling their implementation
//! out-of-tree via crate replacement. Though due to the complex
//! inter-dependencies within `std` that will be a challenging goal to
//! achieve.
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#![allow(missing_debug_implementations)]
mod common;
cfg_if::cfg_if! {
if #[cfg(unix)] {
mod unix;
pub use self::unix::*;
} else if #[cfg(windows)] {
mod windows;
pub use self::windows::*;
Add SOLID targets SOLID[1] is an embedded development platform provided by Kyoto Microcomputer Co., Ltd. This commit introduces a basic Tier 3 support for SOLID. # New Targets The following targets are added: - `aarch64-kmc-solid_asp3` - `armv7a-kmc-solid_asp3-eabi` - `armv7a-kmc-solid_asp3-eabihf` SOLID's target software system can be divided into two parts: an RTOS kernel, which is responsible for threading and synchronization, and Core Services, which provides filesystems, networking, and other things. The RTOS kernel is a μITRON4.0[2][3]-derived kernel based on the open-source TOPPERS RTOS kernels[4]. For uniprocessor systems (more precisely, systems where only one processor core is allocated for SOLID), this will be the TOPPERS/ASP3 kernel. As μITRON is traditionally only specified at the source-code level, the ABI is unique to each implementation, which is why `asp3` is included in the target names. More targets could be added later, as we support other base kernels (there are at least three at the point of writing) and are interested in supporting other processor architectures in the future. # C Compiler Although SOLID provides its own supported C/C++ build toolchain, GNU Arm Embedded Toolchain seems to work for the purpose of building Rust. # Unresolved Questions A μITRON4 kernel can support `Thread::unpark` natively, but it's not used by this commit's implementation because the underlying kernel feature is also used to implement `Condvar`, and it's unclear whether `std` should guarantee that parking tokens are not clobbered by other synchronization primitives. # Unsupported or Unimplemented Features Most features are implemented. The following features are not implemented due to the lack of native support: - `fs::File::{file_attr, truncate, duplicate, set_permissions}` - `fs::{symlink, link, canonicalize}` - Process creation - Command-line arguments Backtrace generation is not really a good fit for embedded targets, so it's intentionally left unimplemented. Unwinding is functional, however. ## Dynamic Linking Dynamic linking is not supported. The target platform supports dynamic linking, but enabling this in Rust causes several problems. - The linker invocation used to build the shared object of `std` is too long for the platform-provided linker to handle. - A linker script with specific requirements is required for the compiled shared object to be actually loadable. As such, we decided to disable dynamic linking for now. Regardless, the users can try to create shared objects by manually invoking the linker. ## Executable Building an executable is not supported as the notion of "executable files" isn't well-defined for these targets. [1] https://solid.kmckk.com/SOLID/ [2] http://ertl.jp/ITRON/SPEC/mitron4-e.html [3] https://en.wikipedia.org/wiki/ITRON_project [4] https://toppers.jp/
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} else if #[cfg(target_os = "solid_asp3")] {
mod solid;
pub use self::solid::*;
} else if #[cfg(target_os = "hermit")] {
mod hermit;
pub use self::hermit::*;
} else if #[cfg(target_os = "wasi")] {
Add a new wasm32-unknown-wasi target This commit adds a new wasm32-based target distributed through rustup, supported in the standard library, and implemented in the compiler. The `wasm32-unknown-wasi` target is intended to be a WebAssembly target which matches the [WASI proposal recently announced.][LINK]. In summary the WASI target is an effort to define a standard set of syscalls for WebAssembly modules, allowing WebAssembly modules to not only be portable across architectures but also be portable across environments implementing this standard set of system calls. The wasi target in libstd is still somewhat bare bones. This PR does not fill out the filesystem, networking, threads, etc. Instead it only provides the most basic of integration with the wasi syscalls, enabling features like: * `Instant::now` and `SystemTime::now` work * `env::args` is hooked up * `env::vars` will look up environment variables * `println!` will print to standard out * `process::{exit, abort}` should be hooked up appropriately None of these APIs can work natively on the `wasm32-unknown-unknown` target, but with the assumption of the WASI set of syscalls we're able to provide implementations of these syscalls that engines can implement. Currently the primary engine implementing wasi is [wasmtime], but more will surely emerge! In terms of future development of libstd, I think this is something we'll probably want to discuss. The purpose of the WASI target is to provide a standardized set of syscalls, but it's *also* to provide a standard C sysroot for compiling C/C++ programs. This means it's intended that functions like `read` and `write` are implemented for this target with a relatively standard definition and implementation. It's unclear, therefore, how we want to expose file descriptors and how we'll want to implement system primitives. For example should `std::fs::File` have a libc-based file descriptor underneath it? The raw wasi file descriptor? We'll see! Currently these details are all intentionally hidden and things we can change over time. A `WasiFd` sample struct was added to the standard library as part of this commit, but it's not currently used. It shows how all the wasi syscalls could be ergonomically bound in Rust, and they offer a possible implementation of primitives like `std::fs::File` if we bind wasi file descriptors exactly. Apart from the standard library, there's also the matter of how this target is integrated with respect to its C standard library. The reference sysroot, for example, provides managment of standard unix file descriptors and also standard APIs like `open` (as opposed to the relative `openat` inspiration for the wasi ssycalls). Currently the standard library relies on the C sysroot symbols for operations such as environment management, process exit, and `read`/`write` of stdio fds. We want these operations in Rust to be interoperable with C if they're used in the same process. Put another way, if Rust and C are linked into the same WebAssembly binary they should work together, but that requires that the same C standard library is used. We also, however, want the `wasm32-unknown-wasi` target to be usable-by-default with the Rust compiler without requiring a separate toolchain to get downloaded and configured. With that in mind, there's two modes of operation for the `wasm32-unknown-wasi` target: 1. By default the C standard library is statically provided inside of `liblibc.rlib` distributed as part of the sysroot. This means that you can `rustc foo.wasm --target wasm32-unknown-unknown` and you're good to go, a fully workable wasi binary pops out. This is incompatible with linking in C code, however, which may be compiled against a different sysroot than the Rust code was previously compiled against. In this mode the default of `rust-lld` is used to link binaries. 2. For linking with C code, the `-C target-feature=-crt-static` flag needs to be passed. This takes inspiration from the musl target for this flag, but the idea is that you're no longer using the provided static C runtime, but rather one will be provided externally. This flag is intended to also get coupled with an external `clang` compiler configured with its own sysroot. Therefore you'll typically use this flag with `-C linker=/path/to/clang-script-wrapper`. Using this mode the Rust code will continue to reference standard C symbols, but the definition will be pulled in by the linker configured. Alright so that's all the current state of this PR. I suspect we'll definitely want to discuss this before landing of course! This PR is coupled with libc changes as well which I'll be posting shortly. [LINK]: [wasmtime]:
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mod wasi;
pub use self::wasi::*;
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} else if #[cfg(target_family = "wasm")] {
mod wasm;
pub use self::wasm::*;
} else if #[cfg(all(target_vendor = "fortanix", target_env = "sgx"))] {
mod sgx;
pub use self::sgx::*;
} else {
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mod unsupported;
pub use self::unsupported::*;
}
}
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// Import essential modules from platforms used in `std::os` when documenting.
//
// Note that on some platforms those modules don't compile
// (missing things in `libc` which is empty), so they are not included in `std::os` and can be
// omitted here as well.
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#[cfg(doc)]
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#[cfg(not(any(
all(target_arch = "wasm32", not(target_os = "wasi")),
all(target_vendor = "fortanix", target_env = "sgx")
)))]
cfg_if::cfg_if! {
if #[cfg(not(windows))] {
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// On non-Windows platforms (aka linux/osx/etc) pull in a "minimal"
// amount of windows goop which ends up compiling
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#[macro_use]
#[path = "windows/compat.rs"]
pub mod compat;
#[path = "windows/c.rs"]
pub mod c;
}
}