Consolidate platform-specific definitions in Wasmtime (#7626)

* Gate more functionality behind `debug-builtins`

This commit extends the gating behavior of the preexisting
`debug-builtins` Cargo feature to cover more GDB-related functionality
associated with debugging. This can additionally slim down the set of
exposed symbols from Wasmtime over the default with them included.

* Move timing in Cranelift behind a Cargo feature

This commit adds a `timing` feature to the `cranelift-codegen` crate
which is enabled by default. This feature gates the timing functionality
in Cranelift to enable turning it off if desired. The goal of this
commit is to remove a system dependency on `Instant` for possibly
esoteric environments.

* Consolidate platform-specific definitions in Wasmtime

Prior to this commit Wasmtime did not not have a style or system for
containing platform-specific logic in files. The goal of this commit is
to consolidate all platform-specific functionality into one location to
make it easier to port Wasmtime to new systems. This commit creates a
`sys` module within the `wasmtime-runtime` crate which conditionally
defines all of the platform support that Wasmtime requires, namely
things related to virtual memory management and trap handling. Many of
the previous `unix.rs` files interspersed throughout the tree are now
all located in a single `unix` directory. This additionally helps split
out `miri`-specific functionality by pretending `miri` is its own
platform.

This change additionally goes through `#[cfg]` directives throughout
`wasmtime-runtime`, `wasmtime-jit`, and `wasmtime` itself to place all
of this target-specific functionality within this `sys` directory. The
end state is that there are two new top-level modules in the
`wasmtime-runtime` crate:

* `arch` - this conditionally defines architecture-specific logic such
  as the state used by backtraces, libcalls, etc.
* `sys` - this conditionally defines OS or platform-specific logic such
  as virtual memory management.

One secondary goal of this commit is to enable the ability to easily
add new platforms to Wasmtime, even if it's in a fork of Wasmtime.
Previously patches might have to touch a good number of locations where
now they'd ideally only have to touch `sys/mod.rs` to declare a new
platform and `sys/$platform/*.rs` to define all the functionality.

* Fix build on Windows

prtest:full

* Fix some build warnings

* Fix miri build

* Include debug-builtins when testing

* Try to fix Windows tests

* Fix warnings on miri

* Fix miri build

* Fix debug-builtins feature

* More feature fixes

* Rename `fd` field

* Fix speeling

* Review comments

Cargo.toml

@@ -65,7 +65,7 @@ rustix = { workspace = true, features = ["mm", "param"] }
 
 [dev-dependencies]
 # depend again on wasmtime to activate its default features for tests
-wasmtime = { workspace = true, features = ['component-model', 'async', 'default', 'winch'] }
+wasmtime = { workspace = true, features = ['component-model', 'async', 'default', 'winch', 'debug-builtins'] }
 env_logger = { workspace = true }
 log = { workspace = true }
 filecheck = { workspace = true }

cranelift/Cargo.toml

@@ -23,7 +23,7 @@ harness = false
 
 [dependencies]
 cfg-if = { workspace = true }
-cranelift-codegen = { workspace = true, features = ["disas", "trace-log"] }
+cranelift-codegen = { workspace = true, features = ["disas", "trace-log", "timing"] }
 cranelift-entity = { workspace = true }
 cranelift-interpreter = { workspace = true }
 cranelift-reader = { workspace = true }

cranelift/codegen/Cargo.toml

@@ -48,7 +48,7 @@ cranelift-codegen-meta = { path = "meta", version = "0.103.0" }
 cranelift-isle = { path = "../isle/isle", version = "=0.103.0" }
 
 [features]
-default = ["std", "unwind", "host-arch"]
+default = ["std", "unwind", "host-arch", "timing"]
 
 # The "std" feature enables use of libstd. The "core" feature enables use
 # of some minimal std-like replacement libraries. At least one of these two
@@ -114,6 +114,11 @@ isle-errors = ["cranelift-isle/fancy-errors"]
 # inspection, rather than inside of target/.
 isle-in-source-tree = []
 
+# Enable tracking how long passes take in Cranelift.
+#
+# Enabled by default.
+timing = []
+
 [[bench]]
 name = "x64-evex-encoding"
 harness = false

cranelift/codegen/src/timing.rs

@@ -5,9 +5,9 @@
 use core::fmt;
 use std::any::Any;
 use std::boxed::Box;
-use std::cell::{Cell, RefCell};
+use std::cell::RefCell;
 use std::mem;
-use std::time::{Duration, Instant};
+use std::time::Duration;
 
 // Each pass that can be timed is predefined with the `define_passes!` macro. Each pass has a
 // snake_case name and a plain text description used when printing out the timing report.
@@ -130,22 +130,6 @@ fn start_pass(pass: Pass) -> Box<dyn Any> {
     PROFILER.with(|profiler| profiler.borrow().start_pass(pass))
 }
 
-/// A timing token is responsible for timing the currently running pass. Timing starts when it
-/// is created and ends when it is dropped.
-///
-/// Multiple passes can be active at the same time, but they must be started and stopped in a
-/// LIFO fashion.
-struct DefaultTimingToken {
-    /// Start time for this pass.
-    start: Instant,
-
-    // Pass being timed by this token.
-    pass: Pass,
-
-    // The previously active pass which will be restored when this token is dropped.
-    prev: Pass,
-}
-
 /// Accumulated timing information for a single pass.
 #[derive(Default, Copy, Clone)]
 struct PassTime {
@@ -215,49 +199,91 @@ impl fmt::Display for PassTimes {
 
 // Information about passes in a single thread.
 thread_local! {
-    static CURRENT_PASS: Cell<Pass> = const { Cell::new(Pass::None) };
     static PASS_TIME: RefCell<PassTimes> = RefCell::new(Default::default());
 }
 
 /// The default profiler. You can get the results using [`take_current`].
 pub struct DefaultProfiler;
 
-impl Profiler for DefaultProfiler {
-    fn start_pass(&self, pass: Pass) -> Box<dyn Any> {
-        let prev = CURRENT_PASS.with(|p| p.replace(pass));
-        log::debug!("timing: Starting {}, (during {})", pass, prev);
-        Box::new(DefaultTimingToken {
-            start: Instant::now(),
-            pass,
-            prev,
-        })
-    }
-}
-
-/// Dropping a timing token indicated the end of the pass.
-impl Drop for DefaultTimingToken {
-    fn drop(&mut self) {
-        let duration = self.start.elapsed();
-        log::debug!("timing: Ending {}: {}ms", self.pass, duration.as_millis());
-        let old_cur = CURRENT_PASS.with(|p| p.replace(self.prev));
-        debug_assert_eq!(self.pass, old_cur, "Timing tokens dropped out of order");
-        PASS_TIME.with(|rc| {
-            let mut table = rc.borrow_mut();
-            table.pass[self.pass.idx()].total += duration;
-            if let Some(parent) = table.pass.get_mut(self.prev.idx()) {
-                parent.child += duration;
-            }
-        })
-    }
-}
-
 /// Take the current accumulated pass timings and reset the timings for the current thread.
 ///
 /// Only applies when [`DefaultProfiler`] is used.
 pub fn take_current() -> PassTimes {
     PASS_TIME.with(|rc| mem::take(&mut *rc.borrow_mut()))
 }
 
+#[cfg(feature = "timing")]
+mod enabled {
+    use super::{DefaultProfiler, Pass, Profiler, PASS_TIME};
+    use std::any::Any;
+    use std::boxed::Box;
+    use std::cell::Cell;
+    use std::time::Instant;
+
+    // Information about passes in a single thread.
+    thread_local! {
+        static CURRENT_PASS: Cell<Pass> = const { Cell::new(Pass::None) };
+    }
+
+    impl Profiler for DefaultProfiler {
+        fn start_pass(&self, pass: Pass) -> Box<dyn Any> {
+            let prev = CURRENT_PASS.with(|p| p.replace(pass));
+            log::debug!("timing: Starting {}, (during {})", pass, prev);
+            Box::new(DefaultTimingToken {
+                start: Instant::now(),
+                pass,
+                prev,
+            })
+        }
+    }
+
+    /// A timing token is responsible for timing the currently running pass. Timing starts when it
+    /// is created and ends when it is dropped.
+    ///
+    /// Multiple passes can be active at the same time, but they must be started and stopped in a
+    /// LIFO fashion.
+    struct DefaultTimingToken {
+        /// Start time for this pass.
+        start: Instant,
+
+        // Pass being timed by this token.
+        pass: Pass,
+
+        // The previously active pass which will be restored when this token is dropped.
+        prev: Pass,
+    }
+
+    /// Dropping a timing token indicated the end of the pass.
+    impl Drop for DefaultTimingToken {
+        fn drop(&mut self) {
+            let duration = self.start.elapsed();
+            log::debug!("timing: Ending {}: {}ms", self.pass, duration.as_millis());
+            let old_cur = CURRENT_PASS.with(|p| p.replace(self.prev));
+            debug_assert_eq!(self.pass, old_cur, "Timing tokens dropped out of order");
+            PASS_TIME.with(|rc| {
+                let mut table = rc.borrow_mut();
+                table.pass[self.pass.idx()].total += duration;
+                if let Some(parent) = table.pass.get_mut(self.prev.idx()) {
+                    parent.child += duration;
+                }
+            })
+        }
+    }
+}
+
+#[cfg(not(feature = "timing"))]
+mod disabled {
+    use super::{DefaultProfiler, Pass, Profiler};
+    use std::any::Any;
+    use std::boxed::Box;
+
+    impl Profiler for DefaultProfiler {
+        fn start_pass(&self, _pass: Pass) -> Box<dyn Any> {
+            Box::new(())
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

crates/cranelift/Cargo.toml

@@ -18,7 +18,7 @@ anyhow = { workspace = true }
 log = { workspace = true }
 wasmtime-environ = { workspace = true }
 cranelift-wasm = { workspace = true }
-cranelift-codegen = { workspace = true, features = ["default"] }
+cranelift-codegen = { workspace = true, features = ["host-arch"] }
 cranelift-frontend = { workspace = true }
 cranelift-entity = { workspace = true }
 cranelift-native = { workspace = true }

crates/jit/Cargo.toml

@@ -15,9 +15,7 @@ workspace = true
 
 [dependencies]
 wasmtime-environ = { workspace = true }
-wasmtime-jit-debug = { workspace = true, features = [
-  "perf_jitdump",
-], optional = true }
+wasmtime-jit-debug = { workspace = true, features = ["perf_jitdump"], optional = true }
 wasmtime-runtime = { workspace = true }
 target-lexicon = { workspace = true }
 anyhow = { workspace = true }
@@ -44,5 +42,6 @@ features = ["Win32_System_Diagnostics_Debug"]
 ittapi = { version = "0.4.0", optional = true }
 
 [features]
-profiling = ['dep:wasmtime-jit-debug', 'dep:ittapi']
+profiling = ['dep:ittapi', 'dep:wasmtime-jit-debug']
 demangle = ['dep:rustc-demangle', 'dep:cpp_demangle']
+debug-builtins = ['wasmtime-runtime/debug-builtins']

crates/jit/src/code_memory.rs

@@ -1,16 +1,14 @@
 //! Memory management for executable code.
 
 use crate::subslice_range;
-use crate::unwind::UnwindRegistration;
 use anyhow::{anyhow, bail, Context, Result};
 use object::read::{File, Object, ObjectSection};
 use object::ObjectSymbol;
 use std::mem::ManuallyDrop;
 use std::ops::Range;
 use wasmtime_environ::obj;
 use wasmtime_jit_icache_coherence as icache_coherence;
-use wasmtime_runtime::libcalls;
-use wasmtime_runtime::MmapVec;
+use wasmtime_runtime::{libcalls, MmapVec, UnwindRegistration};
 
 /// Management of executable memory within a `MmapVec`
 ///

crates/jit/src/instantiate.rs

@@ -4,9 +4,8 @@
 //! steps.
 
 use crate::code_memory::CodeMemory;
-use crate::debug::create_gdbjit_image;
 use crate::profiling::ProfilingAgent;
-use anyhow::{bail, Context, Error, Result};
+use anyhow::{bail, Error, Result};
 use object::write::{Object, SectionId, StandardSegment, WritableBuffer};
 use object::SectionKind;
 use serde_derive::{Deserialize, Serialize};
@@ -19,9 +18,7 @@ use wasmtime_environ::{
     DefinedFuncIndex, FuncIndex, FunctionLoc, MemoryInitialization, Module, ModuleTranslation,
     PrimaryMap, SignatureIndex, StackMapInformation, Tunables, WasmFunctionInfo,
 };
-use wasmtime_runtime::{
-    CompiledModuleId, CompiledModuleIdAllocator, GdbJitImageRegistration, MmapVec,
-};
+use wasmtime_runtime::{CompiledModuleId, CompiledModuleIdAllocator, MmapVec};
 
 /// Secondary in-memory results of function compilation.
 #[derive(Serialize, Deserialize)]
@@ -426,7 +423,8 @@ pub struct CompiledModule {
     wasm_to_native_trampolines: Vec<(SignatureIndex, FunctionLoc)>,
     meta: Metadata,
     code_memory: Arc<CodeMemory>,
-    dbg_jit_registration: Option<GdbJitImageRegistration>,
+    #[cfg(feature = "debug-builtins")]
+    dbg_jit_registration: Option<wasmtime_runtime::GdbJitImageRegistration>,
     /// A unique ID used to register this module with the engine.
     unique_id: CompiledModuleId,
     func_names: Vec<FunctionName>,
@@ -459,6 +457,7 @@ impl CompiledModule {
             module: Arc::new(info.module),
             funcs: info.funcs,
             wasm_to_native_trampolines: info.wasm_to_native_trampolines,
+            #[cfg(feature = "debug-builtins")]
             dbg_jit_registration: None,
             code_memory,
             meta: info.meta,
@@ -471,11 +470,17 @@ impl CompiledModule {
     }
 
     fn register_debug_and_profiling(&mut self, profiler: &dyn ProfilingAgent) -> Result<()> {
+        #[cfg(feature = "debug-builtins")]
         if self.meta.native_debug_info_present {
+            use anyhow::Context;
+
             let text = self.text();
-            let bytes = create_gdbjit_image(self.mmap().to_vec(), (text.as_ptr(), text.len()))
-                .context("failed to create jit image for gdb")?;
-            let reg = GdbJitImageRegistration::register(bytes);
+            let bytes = crate::debug::create_gdbjit_image(
+                self.mmap().to_vec(),
+                (text.as_ptr(), text.len()),
+            )
+            .context("failed to create jit image for gdb")?;
+            let reg = wasmtime_runtime::GdbJitImageRegistration::register(bytes);
             self.dbg_jit_registration = Some(reg);
         }
         profiler.register_module(&self.code_memory, &|addr| {
@@ -669,6 +674,7 @@ impl CompiledModule {
     /// what filename and line number a wasm pc comes from.
     #[cfg(feature = "addr2line")]
     pub fn symbolize_context(&self) -> Result<Option<SymbolizeContext<'_>>> {
+        use anyhow::Context;
         use gimli::EndianSlice;
         if !self.meta.has_wasm_debuginfo {
             return Ok(None);

crates/jit/src/lib.rs

@@ -3,11 +3,11 @@
 #![deny(missing_docs)]
 
 mod code_memory;
+#[cfg(feature = "debug-builtins")]
 mod debug;
 mod demangling;
 mod instantiate;
 pub mod profiling;
-mod unwind;
 
 pub use crate::code_memory::CodeMemory;
 #[cfg(feature = "addr2line")]