SGX target: simplify usercall internals
This moves logic from assembly to Rust and removes the special case for exit/panic handling, merging it with regular usercall handling.
Also, this fixes a bug in the exit usercall introduced in a75ae00. The bug would make regular exits look like panics with high probability. It would also with some probability leak information through uncleared registers.
cc @VardhanThigle
r? @alexcrichton
Cosmetic improvements to doc comments
This has been factored out from https://github.com/rust-lang/rust/pull/58036 to only include changes to documentation comments (throughout the rustc codebase).
r? @steveklabnik
Once you're happy with this, maybe we could get it through with r=1, so it doesn't constantly get invalidated? (I'm not sure this will be an issue, but just in case...) Anyway, thanks for your advice so far!
Require a list of features in `#[allow_internal_unstable]`
The blanket-permission slip is not great and will likely give us trouble some point down the road.
Rollup of 16 pull requests
Successful merges:
- #57259 (Update reference of rlibc crate to compiler-builtins crate)
- #57740 (Use `to_ne_bytes` for converting IPv4Addr to octets)
- #57926 (Tiny expansion to docs for `core::convert`.)
- #58157 (Add Cargo.lock automatically adding message)
- #58203 (rustdoc: display sugared return types for async functions)
- #58243 (Add trait alias support in rustdoc)
- #58262 (Add #[must_use] message to Fn* traits)
- #58295 (std::sys::unix::stdio: explain why we do into_raw)
- #58297 (Cleanup JS a bit)
- #58317 (Some writing improvement, conciseness of intro)
- #58324 (miri: give non-generic functions a stable address)
- #58332 (operand-to-place copies should never be overlapping)
- #58345 (When there are multiple filenames, print what got interpreted as filenames)
- #58346 (rpath computation: explain why we pop())
- #58350 (Fix failing tidy (line endings on Windows))
- #58352 (miri value visitor: use `?` in macro)
Failed merges:
r? @ghost
Improve error message and docs for non-UTF-8 bytes in stdio on Windows
This should make debugging problems like abonander/multipart#106 significantly more straightforward in the future.
cc #23344, @retep998 @alexcrichton
Not sure who do r? so I'll let rust-highfive pick one.
This moves logic from assembly to Rust and removes the special
case for exit/panic handling, merging it with regular usercall
handling.
Also, this fixes a bug in the exit usercall introduced in a75ae00.
The bug would make regular exits look like panics with high
probability. It would also with some probability leak information
through uncleared registers.
Update visibility of intermediate use items.
Fixes#57410 and fixes#53925 and fixes#47816.
Currently, the target of a use statement will be updated with
the visibility of the use statement itself (if the use statement was
visible).
This PR ensures that if the path to the target item is via another
use statement then that intermediate use statement will also have the
visibility updated like the target. This silences incorrect
`unreachable_pub` lints with inactionable suggestions.
Fix `std::os::fortanix_sgx::usercalls::raw::UsercallNrs`
It was 0-indexed but should be 1-indexed. This PR just removes the duplicate code and re-exports the internal enum.
Fixes https://github.com/fortanix/rust-sgx/issues/88
r? @joshtriplett
Currently, the target of a use statement will be updated with
the visibility of the use statement itself (if the use statement was
visible).
This commit ensures that if the path to the target item is via another
use statement then that intermediate use statement will also have the
visibility updated like the target. This silences incorrect
`unreachable_pub` lints with inactionable suggestions.
SGX target: improve panic & exit handling
Implement this part of the spec:
> The enclave must not rely on userspace to terminate other threads still running. Similarly, the enclave must not trust that it will no longer be entered by userspace, and it must safeguard against that in the entrypoints.
Also use `UserRef` to access panic buffer
r? @alexcrichton
cc @VardhanThigle
Print a slightly clearer message when failing to launch a thread
As discussed in #46345, the `io::Error` you get when a thread fails to launch is of type `io::ErrorKind::WouldBlock`. This is super uninformative when an arbitrary `thread::spawn` fails somewhere in your code:
```
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Os { code: 11,
kind: WouldBlock, message: "operation would block" }', src/libcore/result.rs:997:5
```
This PR improves the situation a little bit by using `expect` instead of `unwrap`. I don't consider this a complete fix for #46345 though.
Fix Instant/Duration math precision & associativity on Windows
**tl;dr** Addition and subtraction on Duration/Instant are not associative on windows because we use the perfcounter frequency in every calculation instead of just when we measure time.
This is my first contrib (PR or Issue) to Rust, so please lmk if I've done this wrong. I followed CONTRIBUTING to the extent I could given my system doesn't seem to be able to build the compiler with changes in the source tree. I also asked about this issue in #rust-beginners a week or so ago, before digging through libstd -- I'm unsure if there's a good way to follow up on that, but I'd be happy to update the docs on the timing structs if this fixes the problem.
## Issue
The `Duration` type keeps seconds in the upper-64 and nanoseconds in the lower-32 bits. In theory doing math on these ought to be basically the same as doing math on any other 64 or 32 bit integral number.
On windows (and I think macos too), however, our math gets messy because the Instant type stores the current point in time in units of HPET Performance Counter counts, not nanoseconds, and does unit conversions on every math operation, rather than just when we measure the time from the system clock.
I tried this code:
```
use std::time::{Duration, Instant};
fn main() {
let now = Instant::now();
let offset = Duration::from_millis(5);
assert_eq!((now + offset) - now, (now - now) + offset);
}
```
On UNIX machines (linux and macos) it behaves as you'd expect -- [no crash](https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=cf2206c0b7e07d8ecc7767a512364094).
On Windows hosts, however, it blows up because of a precision problem in the Instant +/- Duration math:
```
C:\Users\aberg\work\timetest (master -> origin)
λ cargo run
Finished dev [unoptimized + debuginfo] target(s) in 0.02s
Running `target\debug\timetest.exe`
thread 'main' panicked at 'assertion failed: `(left == right)`
left: `4.999914ms`,
right: `5ms`', src\main.rs:6:5
note: Run with `RUST_BACKTRACE=1` for a backtrace.
error: process didn't exit successfully: `target\debug\timetest.exe` (exit code: 101)
C:\Users\aberg\work\timetest (master -> origin)
λ cat src\main.rs
use std::time::{Duration, Instant};
fn main() {
let now = Instant::now();
let offset = Duration::from_millis(5);
assert_eq!((now + offset) - now, (now - now) + offset);
}
```
On windows I think this is a consequence of doing the HPET-PerfCounter-Unit conversion on each math operation. I suspect the reason it works on macs is that (from what I could find online) most apple machines report timing in nanoseconds anyway. For anyone interested, the equivalent functions on macos, with a little work to fish out the numerator/denominator from a timebase struct:
* `QueryPerformanceCounter()` -> `mach_absolute_time()`
* `QueryPerformanceFrequency()` -> `mach_timebase_info()`
If this PR ends up working as I expect it to when CI runs the tests, I can make the same changes to the macos implementation.
## Potential Fix
We ought to be able to sort this out by storing nanoseconds, rather than PerfCounter units, that way intermediate math is done in the most precise units we support and we're only doing unit conversions when we actually measure the system clock (and it might even translate to a small perf gain for people doing tons of Instant/Duration math).
I believe this will address the underlying cause of #56034, and make the guessed epsilon constant from #56059 unnecessary. If it's of interest, I can write up how these timing types work on the tier 1 platforms to address #32626 as well, since I'm already in here figuring it out.
## This Patch
To that end, I've got this patch, which I think should fix it on windows, but I'm having trouble testing it -- any time I change anything in libstd I start getting this error, which no amount of clean building seems to resolve:
```
C:\Users\aberg\work\rust (master -> origin)
λ python x.py test --stage 0 --no-doc src/libstd
Updating only changed submodules
Submodules updated in 0.27 seconds
Finished dev [unoptimized] target(s) in 2.41s
Building stage0 std artifacts (x86_64-pc-windows-msvc -> x86_64-pc-windows-msvc)
Finished release [optimized] target(s) in 6.78s
Copying stage0 std from stage0 (x86_64-pc-windows-msvc -> x86_64-pc-windows-msvc / x86_64-pc-windows-msvc)
Building stage0 test artifacts (x86_64-pc-windows-msvc -> x86_64-pc-windows-msvc)
Compiling test v0.0.0 (C:\Users\aberg\work\rust\src\libtest)
error[E0460]: found possibly newer version of crate `std` which `getopts` depends on
--> src\libtest\lib.rs:36:1
|
36 | extern crate getopts;
| ^^^^^^^^^^^^^^^^^^^^^
|
= note: perhaps that crate needs to be recompiled?
= note: the following crate versions were found:
crate `std`: \\?\C:\Users\aberg\work\rust\build\x86_64-pc-windows-msvc\stage0-sysroot\lib\rustlib\x86_64-pc-windows-msvc\lib\libstd-d7a80ca2ae113c97.rlib
crate `std`: \\?\C:\Users\aberg\work\rust\build\x86_64-pc-windows-msvc\stage0-sysroot\lib\rustlib\x86_64-pc-windows-msvc\lib\std-d7a80ca2ae113c97.dll
crate `getopts`: \\?\C:\Users\aberg\work\rust\build\x86_64-pc-windows-msvc\stage0-test\x86_64-pc-windows-msvc\release\deps\libgetopts-ae40a96de5f5d144.rlib
error: aborting due to previous error
For more information about this error, try `rustc --explain E0460`.
error: Could not compile `test`.
To learn more, run the command again with --verbose.
command did not execute successfully: "C:\\Users\\aberg\\work\\rust\\build\\x86_64-pc-windows-msvc\\stage0\\bin\\cargo.exe" "build" "--target" "x86_64-pc-windows-msvc" "-j" "12" "--release" "--manifest-path" "C:\\Users\\aberg\\work\\rust\\src/libtest/Cargo.toml" "--message-format" "json"
expected success, got: exit code: 101
failed to run: C:\Users\aberg\work\rust\build\bootstrap\debug\bootstrap test --stage 0 --no-doc src/libstd
Build completed unsuccessfully in 0:00:20
```
---
Since you wrote the linked PRs and might remember looking at related problems:
r? @alexcrichton
Jethro Beekman