vasilito 4b683014c9 relibc: PthreadFlags::FINISHED + robust_list_head + mutex_owner_id_is_live + comprehensive semaphores
P5-pthread-sigmask-race introduced PthreadFlags::FINISHED
handling in pthread_kill(). Add the FINISHED bit to PthreadFlags
(0x2) and set it in exit_current_thread() so a thread that
exited but whose memory has not been reaped is correctly
identified as finished.

P5-robust-mutexes references thread.robust_list_head and
crate::pthread::mutex_owner_id_is_live(). Add:

  - Pthread.robust_list_head: UnsafeCell<*mut RobustMutexNode>
    in src/pthread/mod.rs and src/ld_so/tcb.rs (both Pthread
    construction sites)

  - pub fn mutex_owner_id_is_live(owner: u32) -> bool in
    src/pthread/mod.rs that probes the thread via the proc
    scheme (Redox) or the OS_TID_TO_PTHREAD map (Linux)

P3-semaphore-comprehensive was un-applied at the merge state
because the next patch in the chain (P3-semaphore-varargs-header)
used the c_variadic unstable feature which is not enabled in
this toolchain. Restore the comprehensive semaphore code with
its original raw-pointer varargs extraction (which works in
Redox's ABI). The raw-pointer approach is fragile per the
multi-threading plan Oracle assessment (C2 finding) but is
the only option without enabling c_variadic; document this in
the patch as a known fragility.

The 52 cargo check errors about 'next_arg' are pre-existing
relibc host-check issues (the Rust stdlib renamed the method
from 'next_arg' to 'arg' but the relibc fork predates the
rename). They do not block the cookbook build (which
cross-compiles to x86_64-unknown-redox).
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Redox C Library (relibc)

relibc is a portable C standard library written in Rust and is under heavy development, this library contain the following items:

  • C, Linux, BSD functions and extensions
  • POSIX compatibility layer
  • Interfaces for system components

The motivation for this project is twofold: Reduce issues that the Redox developers were having with newlib, and create a more stable and safe alternative to C standard libraries written in C. It is mainly designed to be used under Redox, as an alternative to newlib, but it also supports Linux via the sc crate.

Currently Redox and Linux are supported.

redox-rt

redox-rt is a runtime library that provides much of the code that enables POSIX on Redox, like fork, exec, signal handling, etc. Relibc uses it as backend in src/platform/redox, and it's intended to eventually be usable independently, without relibc.

Repository Layout

  • include - Header files (mostly macros and variadic functions cbindgen can't generate)
  • src - Source files
  • src/c - C code
  • src/crt0 - Runtime code
  • src/crti - Runtime code
  • src/crtn - Runtime code
  • src/header - Header files implementation
  • src/header/* - Each folder has a cbindgen.toml file, it generates a C-to-Rust interface and header files
  • src/ld_so - Dynamic loader code
  • src/platform - Platform-specific and common code
  • src/platform/redox - Redox-specific code
  • src/platform/linux - Linux-specific code
  • src/pthread - pthread implementation
  • src/sync - Synchronization primitives
  • tests - C tests (each MR needs to give success in all of them)

Download the sources

To download the relibc sources run the following command:

git clone --recursive https://gitlab.redox-os.org/redox-os/relibc

Build Instructions

To build relibc out of the Redox build system, do the following steps:

Dependencies

  • Install cbindgen
cargo install cbindgen

Install the expect tool

  • Debian, Ubuntu and PopOS:
sudo apt install expect
  • Fedora:
sudo dnf install expect
  • Arch Linux:
sudo pacman -S expect

Build Relibc

To build the relibc library objects, run the following command:

make all
  • Clean old library objects and tests
make clean

Build relibc inside the Redox build system

Inside of your Redox build system, run:

make prefix

If you need to rebuild relibc for testing a Cookbook recipe, run:

touch relibc
make prefix r.recipe-name

Touching (changing the "last modified time" of) the relibc folder is needed to trigger recompilation for make prefix. Replace recipe-name with your desired recipe name.

Note: Do not edit relibc inside prefix folder! Do your work on relibc folder directly inside your Redox build system instead.

Tests

Relibc has a test suite that also runs every time a new commit get pushed. You can see .gitlab-ci.yml to see how it's being executed. That being said, ./check.sh is the recommended way to run tests. Here's few examples:

  • ./check.sh - Run build, without running the test
  • ./check.sh --test - Run all tests in x86_64 Redox using Redoxer
  • ./check.sh --test --host - Run all tests in host (Linux)
  • ./check.sh --test --arch=aarch64 - Run all tests in specified arch
    • Arch can be x86_64, aarch64, i586, or riscv64gc
  • ./check.sh --test=stdio/printf - Run a single test
    • Can be combined with --host or --arch
    • Will run statically linked test in Linux, dynamically linked in Redox

Couple of notes:

  • Relibc and its tests will rebuild if files changed, however switching between arch or host requires you to run make clean
  • Redoxer is needed to run tests for Redox without --host. You can install it using cargo install redoxer
  • Tests can hangs, the test runner can anticipate this, assuming the kernel doesn't hang too.

Issues

I'm building for my own platform which I run, and am getting x86_64-linux-gnu-ar: command not found (or similar)

The Makefile expects GNU compiler tools prefixed with the platform specifier, as would be present when you installed a cross compiler. Since you are building for your own platform, some Linux distributions (like Manjaro) don't install/symlink the prefixed executables.

An easy fix would be to replace the corresponding lines in config.mk, e.g.

ifeq ($(TARGET),x86_64-unknown-linux-gnu)
-	export CC=x86_64-linux-gnu-gcc
-	export LD=x86_64-linux-gnu-ld
-	export AR=x86_64-linux-gnu-ar
-	export NM=x86_64-linux-gnu-nm
+       export CC=gcc
+       export LD=ld
+       export AR=ar
+       export NM=nm
	export OBJCOPY=objcopy
	export CPPFLAGS=
	LD_SO_PATH=lib/ld64.so.1
endif

Contributing

Before starting to contribute, read this document.

Supported OSes

  • Redox OS
  • Linux

Supported architectures

  • i586 (Intel/AMD)
  • x86_64 (Intel/AMD)
  • aarch64 (ARM64)
  • riscv64gc (RISC-V)

Funding - Unix-style Signals and Process Management

This project is funded through NGI Zero Core, a fund established by NLnet with financial support from the European Commission's Next Generation Internet program. Learn more at the NLnet project page.

NLnet foundation logo NGI Zero Logo

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