std: Start supporting WASIp2 natively

This commit is the start of an effort to support WASIp2 natively in the
standard library. Before this commit the `wasm32-wasip2` target behaved
exactly like `wasm32-wasip1` target by importing APIs from the core wasm
module `wasi_snapshot_preview1`. These APIs are satisfied by the
`wasm-component-ld` target by using an [adapter] which implements WASIp1
in terms of WASIp2. This adapter comes at a cost, however, in terms of
runtime indirection and instantiation cost, so ideally the adapter would
be removed entirely. The purpose of this adapter was to provide a
smoother on-ramp from WASIp1 to WASIp2 when it was originally created.

The `wasm32-wasip2` target has been around for long enough now that it's
much more established. Additionally the only thing historically blocking
using WASIp2 directly was implementation effort. Work is now underway to
migrate wasi-libc itself to using WASIp2 directly and now seems as good
a time as any to migrate the Rust standard library too.

Implementation-wise the milestones here are:

* The `wasm32-wasip2` target now also depends on the `wasi` crate at
  version 0.14.* in addition to the preexisting dependency of 0.11.*.
  The 0.14.* release series binds WASIp2 APIs instead of WASIp1 APIs.
* Some preexisting naming around `mod wasi` or `wasi.rs` was renamed to
  `wasip1` where appropriate. For example `std::sys::pal::wasi` is now
  called `std::sys::pal::wasip1`.
* More platform-specific WASI modules are now split between WASIp1 and
  WASIp2. For example getting the current time, randomness, and
  process arguments now use WASIp2 APIs directly instead of using WASIp1
  APIs that require an adapter.

It's worth pointing out that this PR does not migrate the entire
standard library away from using WASIp1 APIs on the `wasm32-wasip2`
target. Everything related to file descriptors and filesystem APIs is
still using WASIp1. Migrating that is left for a future PR. In the
meantime the goal of this change is to lay the groundwork necessary for
migrating in the future. Eventually the goal is to drop the `wasi`
0.11.* dependency on the `wasm32-wasip2` target (the `wasm32-wasip1`
target will continue to retain this dependency).

[adapter]: https://github.com/bytecodealliance/wasmtime/blob/main/crates/wasi-preview1-component-adapter/README.md

library/Cargo.lock

@@ -327,7 +327,8 @@ dependencies = [
  "rustc-demangle",
  "std_detect",
  "unwind",
- "wasi",
+ "wasi 0.11.1+wasi-snapshot-preview1",
+ "wasi 0.14.3+wasi-0.2.4",
  "windows-targets 0.0.0",
 ]
 
@@ -399,6 +400,17 @@ dependencies = [
  "rustc-std-workspace-core",
 ]
 
+[[package]]
+name = "wasi"
+version = "0.14.3+wasi-0.2.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6a51ae83037bdd272a9e28ce236db8c07016dd0d50c27038b3f407533c030c95"
+dependencies = [
+ "rustc-std-workspace-alloc",
+ "rustc-std-workspace-core",
+ "wit-bindgen",
+]
+
 [[package]]
 name = "windows-sys"
 version = "0.59.0"
@@ -475,3 +487,13 @@ name = "windows_x86_64_msvc"
 version = "0.52.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "589f6da84c646204747d1270a2a5661ea66ed1cced2631d546fdfb155959f9ec"
+
+[[package]]
+name = "wit-bindgen"
+version = "0.45.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "052283831dbae3d879dc7f51f3d92703a316ca49f91540417d38591826127814"
+dependencies = [
+ "rustc-std-workspace-alloc",
+ "rustc-std-workspace-core",
+]

library/std/Cargo.toml

@@ -80,6 +80,11 @@ wasi = { version = "0.11.0", features = [
     'rustc-dep-of-std',
 ], default-features = false }
 
+[target.'cfg(all(target_os = "wasi", target_env = "p2"))'.dependencies]
+wasip2 = { version = '0.14.3', features = [
+    'rustc-dep-of-std',
+], default-features = false, package = 'wasi' }
+
 [target.'cfg(target_os = "uefi")'.dependencies]
 r-efi = { version = "5.2.0", features = ['rustc-dep-of-std'] }
 r-efi-alloc = { version = "2.0.0", features = ['rustc-dep-of-std'] }

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

@@ -32,9 +32,13 @@
         mod uefi;
         pub use uefi::*;
     }
-    target_os = "wasi" => {
-        mod wasi;
-        pub use wasi::*;
+    all(target_os = "wasi", target_env = "p1") => {
+        mod wasip1;
+        pub use wasip1::*;
+    }
+    all(target_os = "wasi", target_env = "p2") => {
+        mod wasip2;
+        pub use wasip2::*;
     }
     target_os = "xous" => {
         mod xous;

library/std/src/sys/args/wasip2.rs

@@ -0,0 +1,6 @@
+pub use super::common::Args;
+
+/// Returns the command line arguments
+pub fn args() -> Args {
+    Args::new(wasip2::cli::environment::get_arguments().into_iter().map(|arg| arg.into()).collect())
+}

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

@@ -49,9 +49,9 @@
         mod wasip2;
         pub use self::wasip2::*;
     }
-    target_os = "wasi" => {
-        mod wasi;
-        pub use self::wasi::*;
+    all(target_os = "wasi", target_env = "p1") => {
+        mod wasip1;
+        pub use self::wasip1::*;
     }
     target_family = "wasm" => {
         mod wasm;

library/std/src/sys/pal/wasip2/mod.rs

@@ -10,13 +10,11 @@
 #[path = "../wasm/atomics/futex.rs"]
 pub mod futex;
 
-#[path = "../wasi/os.rs"]
+#[path = "../wasip1/os.rs"]
 pub mod os;
 #[path = "../unsupported/pipe.rs"]
 pub mod pipe;
-#[path = "../wasi/thread.rs"]
 pub mod thread;
-#[path = "../wasi/time.rs"]
 pub mod time;
 
 #[path = "../unsupported/common.rs"]
@@ -26,7 +24,7 @@
 
 pub use common::*;
 
-#[path = "../wasi/helpers.rs"]
+#[path = "../wasip1/helpers.rs"]
 mod helpers;
 
 // The following exports are listed individually to work around Rust's glob

library/std/src/sys/pal/wasip2/thread.rs

@@ -0,0 +1,73 @@
+use crate::ffi::CStr;
+use crate::io;
+use crate::num::NonZero;
+use crate::time::{Duration, Instant};
+
+pub struct Thread(!);
+
+pub const DEFAULT_MIN_STACK_SIZE: usize = 1024 * 1024;
+
+impl Thread {
+    pub unsafe fn new(
+        _stack: usize,
+        _name: Option<&str>,
+        _p: Box<dyn FnOnce()>,
+    ) -> io::Result<Thread> {
+        // Note that unlike WASIp1 even if the wasm `atomics` feature is enabled
+        // there is no support for threads, not even experimentally, not even in
+        // wasi-libc. Thus this is unconditionally unsupported.
+        crate::sys::unsupported()
+    }
+
+    pub fn yield_now() {
+        // no API for this in WASIp2, but there's also no threads, so that's
+        // sort of expected.
+    }
+
+    pub fn set_name(_name: &CStr) {
+        // nope
+    }
+
+    pub fn sleep(dur: Duration) {
+        // Sleep in increments of `u64::MAX` nanoseconds until the `dur` is
+        // entirely drained.
+        let mut remaining = dur.as_nanos();
+        while remaining > 0 {
+            let amt = u64::try_from(remaining).unwrap_or(u64::MAX);
+            wasip2::clocks::monotonic_clock::subscribe_duration(amt).block();
+            remaining -= u128::from(amt);
+        }
+    }
+
+    pub fn sleep_until(deadline: Instant) {
+        match u64::try_from(deadline.into_inner().as_duration().as_nanos()) {
+            // If the point in time we're sleeping to fits within a 64-bit
+            // number of nanoseconds then directly use `subscribe_instant`.
+            Ok(deadline) => {
+                wasip2::clocks::monotonic_clock::subscribe_instant(deadline).block();
+            }
+            // ... otherwise we're sleeping for 500+ years relative to the
+            // "start" of what the system is using as a clock so speed/accuracy
+            // is not so much of a concern. Use `sleep` instead.
+            Err(_) => {
+                let now = Instant::now();
+
+                if let Some(delay) = deadline.checked_duration_since(now) {
+                    Self::sleep(delay);
+                }
+            }
+        }
+    }
+
+    pub fn join(self) {
+        self.0
+    }
+}
+
+pub(crate) fn current_os_id() -> Option<u64> {
+    None
+}
+
+pub fn available_parallelism() -> io::Result<NonZero<usize>> {
+    crate::sys::unsupported()
+}

library/std/src/sys/pal/wasip2/time.rs

@@ -0,0 +1,69 @@
+use crate::time::Duration;
+
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)]
+pub struct Instant(Duration);
+
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)]
+pub struct SystemTime(Duration);
+
+pub const UNIX_EPOCH: SystemTime = SystemTime(Duration::from_secs(0));
+
+impl Instant {
+    pub fn now() -> Instant {
+        Instant(Duration::from_nanos(wasip2::clocks::monotonic_clock::now()))
+    }
+
+    pub fn checked_sub_instant(&self, other: &Instant) -> Option<Duration> {
+        self.0.checked_sub(other.0)
+    }
+
+    pub fn checked_add_duration(&self, other: &Duration) -> Option<Instant> {
+        Some(Instant(self.0.checked_add(*other)?))
+    }
+
+    pub fn checked_sub_duration(&self, other: &Duration) -> Option<Instant> {
+        Some(Instant(self.0.checked_sub(*other)?))
+    }
+
+    pub(super) fn as_duration(&self) -> &Duration {
+        &self.0
+    }
+}
+
+impl SystemTime {
+    pub fn now() -> SystemTime {
+        let now = wasip2::clocks::wall_clock::now();
+        SystemTime(Duration::new(now.seconds, now.nanoseconds))
+    }
+
+    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
+    pub const fn from_wasi_timestamp(ts: wasi::Timestamp) -> SystemTime {
+        SystemTime(Duration::from_nanos(ts))
+    }
+
+    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
+    pub const fn to_wasi_timestamp(&self) -> Option<wasi::Timestamp> {
+        // FIXME: const TryInto
+        let ns = self.0.as_nanos();
+        if ns <= u64::MAX as u128 { Some(ns as u64) } else { None }
+    }
+
+    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
+    pub const fn sub_time(&self, other: &SystemTime) -> Result<Duration, Duration> {
+        // FIXME: ok_or_else with const closures
+        match self.0.checked_sub(other.0) {
+            Some(duration) => Ok(duration),
+            None => Err(other.0 - self.0),
+        }
+    }
+
+    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
+    pub const fn checked_add_duration(&self, other: &Duration) -> Option<SystemTime> {
+        Some(SystemTime(self.0.checked_add(*other)?))
+    }
+
+    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
+    pub const fn checked_sub_duration(&self, other: &Duration) -> Option<SystemTime> {
+        Some(SystemTime(self.0.checked_sub(*other)?))
+    }
+}

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

@@ -86,9 +86,13 @@
         mod vxworks;
         pub use vxworks::fill_bytes;
     }
-    target_os = "wasi" => {
-        mod wasi;
-        pub use wasi::fill_bytes;
+    all(target_os = "wasi", target_env = "p1") => {
+        mod wasip1;
+        pub use wasip1::fill_bytes;
+    }
+    all(target_os = "wasi", target_env = "p2") => {
+        mod wasip2;
+        pub use wasip2::{fill_bytes, hashmap_random_keys};
     }
     target_os = "zkvm" => {
         mod zkvm;
@@ -110,6 +114,7 @@
     target_os = "linux",
     target_os = "android",
     all(target_family = "wasm", target_os = "unknown"),
+    all(target_os = "wasi", target_env = "p2"),
     target_os = "xous",
 )))]
 pub fn hashmap_random_keys() -> (u64, u64) {

library/std/src/sys/random/wasip2.rs

@@ -0,0 +1,9 @@
+pub fn fill_bytes(bytes: &mut [u8]) {
+    bytes.copy_from_slice(&wasip2::random::random::get_random_bytes(
+        u64::try_from(bytes.len()).unwrap(),
+    ));
+}
+
+pub fn hashmap_random_keys() -> (u64, u64) {
+    wasip2::random::insecure_seed::insecure_seed()
+}

src/tools/tidy/src/deps.rs

@@ -490,6 +490,7 @@
     "windows_x86_64_gnu",
     "windows_x86_64_gnullvm",
     "windows_x86_64_msvc",
+    "wit-bindgen",
     // tidy-alphabetical-end
 ];
 
@@ -798,7 +799,10 @@ fn check_runtime_no_duplicate_dependencies(metadata: &Metadata, bad: &mut bool)
             continue;
         }
 
-        if !seen_pkgs.insert(&*pkg.name) {
+        // Skip the `wasi` crate here which the standard library explicitly
+        // depends on two version of (one for the `wasm32-wasip1` target and
+        // another for the `wasm32-wasip2` target).
+        if pkg.name.to_string() != "wasi" && !seen_pkgs.insert(&*pkg.name) {
             tidy_error!(
                 bad,
                 "duplicate package `{}` is not allowed for the standard library",

triagebot.toml

@@ -450,7 +450,8 @@ trigger_files = [
 
 [autolabel."O-wasi"]
 trigger_files = [
-    "library/std/src/sys/pal/wasi",
+    "library/std/src/sys/pal/wasip1",
+    "library/std/src/sys/pal/wasip2",
     "library/std/src/os/wasi"
 ]