rust/library/std/build.rs

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use std::env;
fn main() {
println!("cargo:rerun-if-changed=build.rs");
let target = env::var("TARGET").expect("TARGET was not set");
if target.contains("freebsd") {
if env::var("RUST_STD_FREEBSD_12_ABI").is_ok() {
println!("cargo:rustc-cfg=freebsd12");
} else if env::var("RUST_STD_FREEBSD_13_ABI").is_ok() {
println!("cargo:rustc-cfg=freebsd12");
println!("cargo:rustc-cfg=freebsd13");
}
} else if target.contains("linux")
|| target.contains("netbsd")
|| target.contains("dragonfly")
|| target.contains("openbsd")
|| target.contains("solaris")
|| target.contains("illumos")
|| target.contains("apple-darwin")
|| target.contains("apple-ios")
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|| target.contains("apple-tvos")
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|| target.contains("apple-watchos")
|| target.contains("uwp")
|| target.contains("windows")
|| target.contains("fuchsia")
|| (target.contains("sgx") && target.contains("fortanix"))
|| target.contains("hermit")
|| target.contains("l4re")
|| target.contains("redox")
|| target.contains("haiku")
|| target.contains("vxworks")
|| target.contains("wasm32")
|| target.contains("wasm64")
|| target.contains("asmjs")
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|| target.contains("espidf")
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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|| target.contains("solid")
|| target.contains("nintendo-3ds")
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|| target.contains("vita")
|| target.contains("nto")
|| target.contains("xous")
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|| target.contains("hurd")
|| target.contains("uefi")
// See src/bootstrap/synthetic_targets.rs
|| env::var("RUSTC_BOOTSTRAP_SYNTHETIC_TARGET").is_ok()
{
// These platforms don't have any special requirements.
} else {
// This is for Cargo's build-std support, to mark std as unstable for
// typically no_std platforms.
// This covers:
// - os=none ("bare metal" targets)
// - mipsel-sony-psp
// - nvptx64-nvidia-cuda
// - arch=avr
// - JSON targets
// - Any new targets that have not been explicitly added above.
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println!("cargo:rustc-cfg=feature=\"restricted-std\"");
}
println!("cargo:rustc-env=STD_ENV_ARCH={}", env::var("CARGO_CFG_TARGET_ARCH").unwrap());
std: Switch from libbacktrace to gimli This commit is a proof-of-concept for switching the standard library's backtrace symbolication mechanism on most platforms from libbacktrace to gimli. The standard library's support for `RUST_BACKTRACE=1` requires in-process parsing of object files and DWARF debug information to interpret it and print the filename/line number of stack frames as part of a backtrace. Historically this support in the standard library has come from a library called "libbacktrace". The libbacktrace library seems to have been extracted from gcc at some point and is written in C. We've had a lot of issues with libbacktrace over time, unfortunately, though. The library does not appear to be actively maintained since we've had patches sit for months-to-years without comments. We have discovered a good number of soundness issues with the library itself, both when parsing valid DWARF as well as invalid DWARF. This is enough of an issue that the libs team has previously decided that we cannot feed untrusted inputs to libbacktrace. This also doesn't take into account the portability of libbacktrace which has been difficult to manage and maintain over time. While possible there are lots of exceptions and it's the main C dependency of the standard library right now. For years it's been the desire to switch over to a Rust-based solution for symbolicating backtraces. It's been assumed that we'll be using the Gimli family of crates for this purpose, which are targeted at safely and efficiently parsing DWARF debug information. I've been working recently to shore up the Gimli support in the `backtrace` crate. As of a few weeks ago the `backtrace` crate, by default, uses Gimli when loaded from crates.io. This transition has gone well enough that I figured it was time to start talking seriously about this change to the standard library. This commit is a preview of what's probably the best way to integrate the `backtrace` crate into the standard library with the Gimli feature turned on. While today it's used as a crates.io dependency, this commit switches the `backtrace` crate to a submodule of this repository which will need to be updated manually. This is not done lightly, but is thought to be the best solution. The primary reason for this is that the `backtrace` crate needs to do some pretty nontrivial filesystem interactions to locate debug information. Working without `std::fs` is not an option, and while it might be possible to do some sort of trait-based solution when prototyped it was found to be too unergonomic. Using a submodule allows the `backtrace` crate to build as a submodule of the `std` crate itself, enabling it to use `std::fs` and such. Otherwise this adds new dependencies to the standard library. This step requires extra attention because this means that these crates are now going to be included with all Rust programs by default. It's important to note, however, that we're already shipping libbacktrace with all Rust programs by default and it has a bunch of C code implementing all of this internally anyway, so we're basically already switching already-shipping functionality to Rust from C. * `object` - this crate is used to parse object file headers and contents. Very low-level support is used from this crate and almost all of it is disabled. Largely we're just using struct definitions as well as convenience methods internally to read bytes and such. * `addr2line` - this is the main meat of the implementation for symbolication. This crate depends on `gimli` for DWARF parsing and then provides interfaces needed by the `backtrace` crate to turn an address into a filename / line number. This crate is actually pretty small (fits in a single file almost!) and mirrors most of what `dwarf.c` does for libbacktrace. * `miniz_oxide` - the libbacktrace crate transparently handles compressed debug information which is compressed with zlib. This crate is used to decompress compressed debug sections. * `gimli` - not actually used directly, but a dependency of `addr2line`. * `adler32`- not used directly either, but a dependency of `miniz_oxide`. The goal of this change is to improve the safety of backtrace symbolication in the standard library, especially in the face of possibly malformed DWARF debug information. Even to this day we're still seeing segfaults in libbacktrace which could possibly become security vulnerabilities. This change should almost entirely eliminate this possibility whilc also paving the way forward to adding more features like split debug information. Some references for those interested are: * Original addition of libbacktrace - #12602 * OOM with libbacktrace - #24231 * Backtrace failure due to use of uninitialized value - #28447 * Possibility to feed untrusted data to libbacktrace - #21889 * Soundness fix for libbacktrace - #33729 * Crash in libbacktrace - #39468 * Support for macOS, never merged - ianlancetaylor/libbacktrace#2 * Performance issues with libbacktrace - #29293, #37477 * Update procedure is quite complicated due to how many patches we need to carry - #50955 * Libbacktrace doesn't work on MinGW with dynamic libs - #71060 * Segfault in libbacktrace on macOS - #71397 Switching to Rust will not make us immune to all of these issues. The crashes are expected to go away, but correctness and performance may still have bugs arise. The gimli and `backtrace` crates, however, are actively maintained unlike libbacktrace, so this should enable us to at least efficiently apply fixes as situations come up.
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println!("cargo:rustc-cfg=backtrace_in_libstd");
}