refactor extern static handling

Author: RalfJung

src/tools/miri/ci/ci.sh

@@ -121,9 +121,8 @@ case $HOST_TARGET in
     MIRI_TEST_TARGET=aarch64-apple-darwin run_tests
     MIRI_TEST_TARGET=i686-pc-windows-gnu run_tests
     # Some targets are only partially supported.
-    # FIXME: freeBSD disabled due to https://github.com/rust-lang/miri/issues/3276
-    #MIRI_TEST_TARGET=x86_64-unknown-freebsd run_tests_minimal hello integer vec panic/panic concurrency/simple pthread-threadname libc-getentropy libc-getrandom libc-misc libc-fs atomic env align
-    #MIRI_TEST_TARGET=i686-unknown-freebsd run_tests_minimal hello integer vec panic/panic concurrency/simple pthread-threadname libc-getentropy libc-getrandom libc-misc libc-fs atomic env align
+    MIRI_TEST_TARGET=x86_64-unknown-freebsd run_tests_minimal hello integer vec panic/panic concurrency/simple pthread-threadname libc-getentropy libc-getrandom libc-misc libc-fs atomic env align
+    MIRI_TEST_TARGET=i686-unknown-freebsd run_tests_minimal hello integer vec panic/panic concurrency/simple pthread-threadname libc-getentropy libc-getrandom libc-misc libc-fs atomic env align
     MIRI_TEST_TARGET=aarch64-linux-android run_tests_minimal hello integer vec panic/panic
     MIRI_TEST_TARGET=wasm32-wasi run_tests_minimal no_std integer strings wasm
     MIRI_TEST_TARGET=wasm32-unknown-unknown run_tests_minimal no_std integer strings wasm

src/tools/miri/src/machine.rs

@@ -691,7 +691,7 @@ impl<'mir, 'tcx> MiriMachine<'mir, 'tcx> {
         Ok(())
     }
 
-    fn add_extern_static(
+    pub(crate) fn add_extern_static(
         this: &mut MiriInterpCx<'mir, 'tcx>,
         name: &str,
         ptr: Pointer<Option<Provenance>>,
@@ -701,75 +701,6 @@ impl<'mir, 'tcx> MiriMachine<'mir, 'tcx> {
         this.machine.extern_statics.try_insert(Symbol::intern(name), ptr).unwrap();
     }
 
-    fn alloc_extern_static(
-        this: &mut MiriInterpCx<'mir, 'tcx>,
-        name: &str,
-        val: ImmTy<'tcx, Provenance>,
-    ) -> InterpResult<'tcx> {
-        let place = this.allocate(val.layout, MiriMemoryKind::ExternStatic.into())?;
-        this.write_immediate(*val, &place)?;
-        Self::add_extern_static(this, name, place.ptr());
-        Ok(())
-    }
-
-    /// Sets up the "extern statics" for this machine.
-    fn init_extern_statics(this: &mut MiriInterpCx<'mir, 'tcx>) -> InterpResult<'tcx> {
-        // "__rust_no_alloc_shim_is_unstable"
-        let val = ImmTy::from_int(0, this.machine.layouts.u8);
-        Self::alloc_extern_static(this, "__rust_no_alloc_shim_is_unstable", val)?;
-
-        match this.tcx.sess.target.os.as_ref() {
-            "linux" => {
-                // "environ"
-                Self::add_extern_static(
-                    this,
-                    "environ",
-                    this.machine.env_vars.environ.as_ref().unwrap().ptr(),
-                );
-                // A couple zero-initialized pointer-sized extern statics.
-                // Most of them are for weak symbols, which we all set to null (indicating that the
-                // symbol is not supported, and triggering fallback code which ends up calling a
-                // syscall that we do support).
-                for name in &["__cxa_thread_atexit_impl", "getrandom", "statx", "__clock_gettime64"]
-                {
-                    let val = ImmTy::from_int(0, this.machine.layouts.usize);
-                    Self::alloc_extern_static(this, name, val)?;
-                }
-            }
-            "freebsd" => {
-                // "environ"
-                Self::add_extern_static(
-                    this,
-                    "environ",
-                    this.machine.env_vars.environ.as_ref().unwrap().ptr(),
-                );
-            }
-            "android" => {
-                // "signal" -- just needs a non-zero pointer value (function does not even get called),
-                // but we arrange for this to be callable anyway (it will then do nothing).
-                let layout = this.machine.layouts.const_raw_ptr;
-                let ptr = this.fn_ptr(FnVal::Other(DynSym::from_str("signal")));
-                let val = ImmTy::from_scalar(Scalar::from_pointer(ptr, this), layout);
-                Self::alloc_extern_static(this, "signal", val)?;
-                // A couple zero-initialized pointer-sized extern statics.
-                // Most of them are for weak symbols, which we all set to null (indicating that the
-                // symbol is not supported, and triggering fallback code.)
-                for name in &["bsd_signal"] {
-                    let val = ImmTy::from_int(0, this.machine.layouts.usize);
-                    Self::alloc_extern_static(this, name, val)?;
-                }
-            }
-            "windows" => {
-                // "_tls_used"
-                // This is some obscure hack that is part of the Windows TLS story. It's a `u8`.
-                let val = ImmTy::from_int(0, this.machine.layouts.u8);
-                Self::alloc_extern_static(this, "_tls_used", val)?;
-            }
-            _ => {} // No "extern statics" supported on this target
-        }
-        Ok(())
-    }
-
     pub(crate) fn communicate(&self) -> bool {
         self.isolated_op == IsolatedOp::Allow
     }

src/tools/miri/src/shims/extern_static.rs

@@ -0,0 +1,78 @@
+//! Provides the `extern static` that this platform expects.
+
+use crate::*;
+
+impl<'mir, 'tcx> MiriMachine<'mir, 'tcx> {
+    fn alloc_extern_static(
+        this: &mut MiriInterpCx<'mir, 'tcx>,
+        name: &str,
+        val: ImmTy<'tcx, Provenance>,
+    ) -> InterpResult<'tcx> {
+        let place = this.allocate(val.layout, MiriMemoryKind::ExternStatic.into())?;
+        this.write_immediate(*val, &place)?;
+        Self::add_extern_static(this, name, place.ptr());
+        Ok(())
+    }
+
+    /// Zero-initialized pointer-sized extern statics are pretty common.
+    /// Most of them are for weak symbols, which we all set to null (indicating that the
+    /// symbol is not supported, and triggering fallback code which ends up calling a
+    /// syscall that we do support).
+    fn null_ptr_extern_statics(
+        this: &mut MiriInterpCx<'mir, 'tcx>,
+        names: &[&str],
+    ) -> InterpResult<'tcx> {
+        for name in names {
+            let val = ImmTy::from_int(0, this.machine.layouts.usize);
+            Self::alloc_extern_static(this, name, val)?;
+        }
+        Ok(())
+    }
+
+    /// Sets up the "extern statics" for this machine.
+    pub fn init_extern_statics(this: &mut MiriInterpCx<'mir, 'tcx>) -> InterpResult<'tcx> {
+        // "__rust_no_alloc_shim_is_unstable"
+        let val = ImmTy::from_int(0, this.machine.layouts.u8);
+        Self::alloc_extern_static(this, "__rust_no_alloc_shim_is_unstable", val)?;
+
+        match this.tcx.sess.target.os.as_ref() {
+            "linux" => {
+                Self::null_ptr_extern_statics(
+                    this,
+                    &["__cxa_thread_atexit_impl", "getrandom", "statx", "__clock_gettime64"],
+                )?;
+                // "environ"
+                Self::add_extern_static(
+                    this,
+                    "environ",
+                    this.machine.env_vars.environ.as_ref().unwrap().ptr(),
+                );
+            }
+            "freebsd" => {
+                // "environ"
+                Self::add_extern_static(
+                    this,
+                    "environ",
+                    this.machine.env_vars.environ.as_ref().unwrap().ptr(),
+                );
+            }
+            "android" => {
+                Self::null_ptr_extern_statics(this, &["bsd_signal"])?;
+                // "signal" -- just needs a non-zero pointer value (function does not even get called),
+                // but we arrange for this to call the `signal` function anyway.
+                let layout = this.machine.layouts.const_raw_ptr;
+                let ptr = this.fn_ptr(FnVal::Other(DynSym::from_str("signal")));
+                let val = ImmTy::from_scalar(Scalar::from_pointer(ptr, this), layout);
+                Self::alloc_extern_static(this, "signal", val)?;
+            }
+            "windows" => {
+                // "_tls_used"
+                // This is some obscure hack that is part of the Windows TLS story. It's a `u8`.
+                let val = ImmTy::from_int(0, this.machine.layouts.u8);
+                Self::alloc_extern_static(this, "_tls_used", val)?;
+            }
+            _ => {} // No "extern statics" supported on this target
+        }
+        Ok(())
+    }
+}

src/tools/miri/src/shims/mod.rs

@@ -10,6 +10,7 @@ pub mod windows;
 mod x86;
 
 pub mod env;
+pub mod extern_static;
 pub mod os_str;
 pub mod panic;
 pub mod time;