Add `riscv64gc-unknown-hermit` target
This PR adds the new `riscv64gc-unknown-hermit` target, initially created by `@simonschoening,` a 64-bit RISC-V target for the [Hermit] unikernel project.
Furthermore, this cleans up the existing Hermit targets and adds a platform support documentation page for _all_ Hermit targets and goes through the new tier 3 target policy process:
[Hermit]: https://github.com/hermitcore
## Tier 3 target policy
> - A tier 3 target must have a designated developer or developers (the "target
> maintainers") on record to be CCed when issues arise regarding the target.
> (The mechanism to track and CC such developers may evolve over time.)
`@stlankes` as the Hermit project lead and I will be the target maintainers.
> - Targets must use naming consistent with any existing targets; for instance, a
> target for the same CPU or OS as an existing Rust target should use the same
> name for that CPU or OS. Targets should normally use the same names and
> naming conventions as used elsewhere in the broader ecosystem beyond Rust
> (such as in other toolchains), unless they have a very good reason to
> diverge. Changing the name of a target can be highly disruptive, especially
> once the target reaches a higher tier, so getting the name right is important
> even for a tier 3 target.
> - Target names should not introduce undue confusion or ambiguity unless
> absolutely necessary to maintain ecosystem compatibility. For example, if
> the name of the target makes people extremely likely to form incorrect
> beliefs about what it targets, the name should be changed or augmented to
> disambiguate it.
> - If possible, use only letters, numbers, dashes and underscores for the name.
> Periods (`.`) are known to cause issues in Cargo.
The target name `riscv64gc-unknown-hermit` was derived from the existing `x86_64-unknown-hermit` and `aarch64-unknown-hermit` targets.
> - Tier 3 targets may have unusual requirements to build or use, but must not
> create legal issues or impose onerous legal terms for the Rust project or for
> Rust developers or users.
> - The target must not introduce license incompatibilities.
> - Anything added to the Rust repository must be under the standard Rust
> license (`MIT OR Apache-2.0`).
> - The target must not cause the Rust tools or libraries built for any other
> host (even when supporting cross-compilation to the target) to depend
> on any new dependency less permissive than the Rust licensing policy. This
> applies whether the dependency is a Rust crate that would require adding
> new license exceptions (as specified by the `tidy` tool in the
> rust-lang/rust repository), or whether the dependency is a native library
> or binary. In other words, the introduction of the target must not cause a
> user installing or running a version of Rust or the Rust tools to be
> subject to any new license requirements.
> - Compiling, linking, and emitting functional binaries, libraries, or other
> code for the target (whether hosted on the target itself or cross-compiling
> from another target) must not depend on proprietary (non-FOSS) libraries.
> Host tools built for the target itself may depend on the ordinary runtime
> libraries supplied by the platform and commonly used by other applications
> built for the target, but those libraries must not be required for code
> generation for the target; cross-compilation to the target must not require
> such libraries at all. For instance, `rustc` built for the target may
> depend on a common proprietary C runtime library or console output library,
> but must not depend on a proprietary code generation library or code
> optimization library. Rust's license permits such combinations, but the
> Rust project has no interest in maintaining such combinations within the
> scope of Rust itself, even at tier 3.
> - "onerous" here is an intentionally subjective term. At a minimum, "onerous"
> legal/licensing terms include but are *not* limited to: non-disclosure
> requirements, non-compete requirements, contributor license agreements
> (CLAs) or equivalent, "non-commercial"/"research-only"/etc terms,
> requirements conditional on the employer or employment of any particular
> Rust developers, revocable terms, any requirements that create liability
> for the Rust project or its developers or users, or any requirements that
> adversely affect the livelihood or prospects of the Rust project or its
> developers or users.
No dependencies were added to Rust.
> - Neither this policy nor any decisions made regarding targets shall create any
> binding agreement or estoppel by any party. If any member of an approving
> Rust team serves as one of the maintainers of a target, or has any legal or
> employment requirement (explicit or implicit) that might affect their
> decisions regarding a target, they must recuse themselves from any approval
> decisions regarding the target's tier status, though they may otherwise
> participate in discussions.
> - This requirement does not prevent part or all of this policy from being
> cited in an explicit contract or work agreement (e.g. to implement or
> maintain support for a target). This requirement exists to ensure that a
> developer or team responsible for reviewing and approving a target does not
> face any legal threats or obligations that would prevent them from freely
> exercising their judgment in such approval, even if such judgment involves
> subjective matters or goes beyond the letter of these requirements.
Understood.
I am not a member of a Rust team.
> - Tier 3 targets should attempt to implement as much of the standard libraries
> as possible and appropriate (`core` for most targets, `alloc` for targets
> that can support dynamic memory allocation, `std` for targets with an
> operating system or equivalent layer of system-provided functionality), but
> may leave some code unimplemented (either unavailable or stubbed out as
> appropriate), whether because the target makes it impossible to implement or
> challenging to implement. The authors of pull requests are not obligated to
> avoid calling any portions of the standard library on the basis of a tier 3
> target not implementing those portions.
Understood.
`std` is supported.
> - The target must provide documentation for the Rust community explaining how
> to build for the target, using cross-compilation if possible. If the target
> supports running binaries, or running tests (even if they do not pass), the
> documentation must explain how to run such binaries or tests for the target,
> using emulation if possible or dedicated hardware if necessary.
Building is described in the platform support doc.
> - Tier 3 targets must not impose burden on the authors of pull requests, or
> other developers in the community, to maintain the target. In particular,
> do not post comments (automated or manual) on a PR that derail or suggest a
> block on the PR based on a tier 3 target. Do not send automated messages or
> notifications (via any medium, including via ``@`)` to a PR author or others
> involved with a PR regarding a tier 3 target, unless they have opted into
> such messages.
> - Backlinks such as those generated by the issue/PR tracker when linking to
> an issue or PR are not considered a violation of this policy, within
> reason. However, such messages (even on a separate repository) must not
> generate notifications to anyone involved with a PR who has not requested
> such notifications.
Understood.
> - Patches adding or updating tier 3 targets must not break any existing tier 2
> or tier 1 target, and must not knowingly break another tier 3 target without
> approval of either the compiler team or the maintainers of the other tier 3
> target.
> - In particular, this may come up when working on closely related targets,
> such as variations of the same architecture with different features. Avoid
> introducing unconditional uses of features that another variation of the
> target may not have; use conditional compilation or runtime detection, as
> appropriate, to let each target run code supported by that target.
I don't think this PR breaks anything.
r? compiler-team
rust-installer: Use env(1) in the shebang.
This fixes the case (e.g. *BSD) where bash is installed on the host system, but not at the typical location of /bin.
make full field retagging the default
The 'scalar' field retagging mode is clearly a hack -- it mirrors details of the codegen backend and how various structs are represented in LLVM. This means whether code has UB or not depends on surprising aspects, such as whether a struct has 2 or 3 (non-zero-sized) fields. Now that both hashbrown and scopeguard have released fixes to be compatible with field retagging, I think it is time to enable full field retagging by default.
`@saethlin` do you have an idea of how much fallout enabling full field retagging by default will cause? Do you have objections to enabling it by default?
Fixes https://github.com/rust-lang/miri/issues/2528
Implement rust-lang/compiler-team#578.
When an ICE is encountered on nightly releases, the new rustc panic
handler will also write the contents of the backtrace to disk. If any
`delay_span_bug`s are encountered, their backtrace is also added to the
file. The platform and rustc version will also be collected.
add mips64r6 and mips32r6 as target_arch values
This PR introduces `"mips32r6"` and `"mips64r6"` as valid `target_arch` values, and would be the arch value used by Tier-3 targets `mipsisa32r6-unknown-linux-gnu`, `mipsisa32r6el-unknown-linux-gnu`, `mipsisa64r6-unknown-linux-gnuabi64` and `mipsisa64r6el-unknown-linux-gnuabi64`.
This PR was inspired by `rustix` attempting to link traditional mips64el objects with mips64r6el objects when building for mips64r6, even though `rustix` recently removed outline assembly support. This is because currently this target's `target_arch` is `"mips64"` and rustix has its respective assembly implementation as well as a pre-compiled little-endian static library prepared for mips64el, a tier-2 target with the same `target_arch`. After some [discussions on zulip](https://rust-lang.zulipchat.com/#narrow/stream/233931-t-compiler.2Fmajor-changes/topic/Add.20New.20Values.20To.20MIPS_ALLOWED_FEATURES.20compiler-team.23595), I decided to treat mips64r6 as an independent architecture from Rust's POV, since these two architectures are incompatible anyway.
This PR is now waiting for `libc` to release a new version with [support](https://github.com/rust-lang/libc/pull/3268) for these `target_arch` values. It is not expected to introduce changes to any other target, especially Tier-1 and Tier-2 targets.
This PR has its corresponding [MCP](https://github.com/rust-lang/compiler-team/issues/632) approved.
Fix compiletest windows path finding with spaces
With `(?x)` enabled spaces are ignored unless you escape them, so the space wasn't being added to the character class
I don't think this makes any difference to the current test suite, but it could save someone a headache in the future
Rename `arg_iter` to `iter_instantiated`
`arg_iter` doesn't make sense, and doesn't really indicate what it's doing (returning an iterator that ~~substitutes~~ instantiates its elements).
`iter_instantiated_copied` is kinda awkward but i don't really wanna bikeshed it.
r? `@oli-obk`
miri: fail when calling a function that requires an unavailable target feature
miri will report an UB when calling a function that has a `#[target_feature(enable = ...)]` attribute is called and the required feature is not available.
"Available features" are the same that `is_x86_feature_detected!` (or equivalent) reports to be available during miri execution (which can be enabled or disabled with the `-C target-feature` flag).
Add a sparc-unknown-none-elf target.
# `sparc-unknown-none-elf`
**Tier: 3**
Rust for bare-metal 32-bit SPARC V7 and V8 systems, e.g. the Gaisler LEON3.
## Target maintainers
- Jonathan Pallant, `jonathan.pallant@ferrous-systems.com`, https://ferrous-systems.com
## Requirements
> Does the target support host tools, or only cross-compilation?
Only cross-compilation.
> Does the target support std, or alloc (either with a default allocator, or if the user supplies an allocator)?
Only tested with `libcore` but I see no reason why you couldn't also support `liballoc`.
> Document the expectations of binaries built for the target. Do they assume
specific minimum features beyond the baseline of the CPU/environment/etc? What
version of the OS or environment do they expect?
Tested by linking with a standard SPARC bare-metal toolchain - specifically I used the [BCC2] toolchain from Gaisler (both GCC and clang variants, both pre-compiled for x64 Linux and compiling my own SPARC GCC from source to run on `aarch64-apple-darwin`).
The target is set to use the lowest-common-denominator `SPARC V7` architecture (yes, they started at V7 - see [Wikipedia](https://en.wikipedia.org/wiki/SPARC#History)).
[BCC2]: https://www.gaisler.com/index.php/downloads/compilers
> Are there notable `#[target_feature(...)]` or `-C target-feature=` values that
programs may wish to use?
`-Ctarget-cpu=v8` adds the instructions added in V8.
`-Ctarget-cpu=leon3` adds the V8 instructions and sets up scheduling to suit the Gaisler LEON3.
> What calling convention does `extern "C"` use on the target?
I believe this is defined by the SPARC architecture reference manuals and V7, V8 and V9 are all compatible.
> What format do binaries use by default? ELF, PE, something else?
ELF
## Building the target
> If Rust doesn't build the target by default, how can users build it? Can users
just add it to the `target` list in `config.toml`?
Yes. I did:
```toml
target = ["aarch64-apple-darwin", "sparc-unknown-none-elf"]
```
## Building Rust programs
> Rust does not yet ship pre-compiled artifacts for this target. To compile for
this target, you will either need to build Rust with the target enabled (see
"Building the target" above), or build your own copy of `core` by using
`build-std` or similar.
Correct.
## Testing
> Does the target support running binaries, or do binaries have varying
expectations that prevent having a standard way to run them?
No - it's a bare metal platform.
> If users can run binaries, can they do so in some common emulator, or do they need native
hardware?
But if you use [BCC2] as the linker, you get default memory map suitable for the LEON3, and a default BSP for the LEON3, and so you can run the binaries in the `tsim-leon3` simulator from Gaisler.
```console
$ cat .cargo/config.toml | grep runner
runner = "tsim-leon3 -c sim-commands.txt"
$ cat sim-commands.txt
run
quit
$ cargo +sparcrust run --targe=sparc-unknown-none-elf
Compiling sparc-demo-rust v0.1.0 (/work/sparc-demo-rust)
Finished dev [unoptimized + debuginfo] target(s) in 3.44s
Running `tsim-leon3 -c sim-commands.txt target/sparc-unknown-none-elf/debug/sparc-demo-rust`
TSIM3 LEON3 SPARC simulator, version 3.1.9 (evaluation version)
Copyright (C) 2023, Frontgrade Gaisler - all rights reserved.
This software may only be used with a valid license.
For latest updates, go to https://www.gaisler.com/
Comments or bug-reports to support@gaisler.com
This TSIM evaluation version will expire 2023-11-28
Number of CPUs: 2
system frequency: 50.000 MHz
icache: 1 * 4 KiB, 16 bytes/line (4 KiB total)
dcache: 1 * 4 KiB, 16 bytes/line (4 KiB total)
Allocated 8192 KiB SRAM memory, in 1 bank at 0x40000000
Allocated 32 MiB SDRAM memory, in 1 bank at 0x60000000
Allocated 8192 KiB ROM memory at 0x00000000
section: .text, addr: 0x40000000, size: 104400 bytes
section: .rodata, addr: 0x400197d0, size: 15616 bytes
section: .data, addr: 0x4001d4d0, size: 1176 bytes
read 1006 symbols
Initializing and starting from 0x40000000
Hello, this is Rust!
PANIC: PanicInfo { payload: Any { .. }, message: Some(I am a panic), location: Location { file: "src/main.rs", line: 33, col: 5 }, can_unwind: true }
Program exited normally on CPU 0.
```
> Does the target support running the Rust testsuite?
I don't think so, the testsuite requires `libstd` IIRC.
## Cross-compilation toolchains and C code
> Does the target support C code?
Yes.
> If so, what toolchain target should users use to build compatible C code? (This may match the target triple, or it may be a toolchain for a different target triple, potentially with specific options or caveats.)
I suggest [BCC2] from Gaisler. It comes in both GCC and Clang variants.
