add very basic Android support

Author: RalfJung

ci.sh

@@ -84,6 +84,7 @@ case $HOST_TARGET in
     MIRI_TEST_TARGET=aarch64-apple-darwin run_tests
     MIRI_TEST_TARGET=i686-pc-windows-msvc run_tests
     MIRI_TEST_TARGET=x86_64-unknown-freebsd run_tests_minimal hello integer vec data_race env/var
+    MIRI_TEST_TARGET=aarch64-linux-android run_tests_minimal hello integer vec
     MIRI_TEST_TARGET=thumbv7em-none-eabihf MIRI_NO_STD=1 run_tests_minimal no_std # no_std embedded architecture
     ;;
   x86_64-apple-darwin)

rust-version

@@ -1 +1 @@
-8556e6620e4866526b3cea767ad8c20ae877a569
+9c20b2a8cc7588decb6de25ac6a7912dcef24d65

src/helpers.rs

@@ -954,5 +954,5 @@ pub fn get_local_crates(tcx: TyCtxt<'_>) -> Vec<CrateNum> {
 /// Helper function used inside the shims of foreign functions to check that
 /// `target_os` is a supported UNIX OS.
 pub fn target_os_is_unix(target_os: &str) -> bool {
-    matches!(target_os, "linux" | "macos" | "freebsd")
+    matches!(target_os, "linux" | "macos" | "freebsd" | "android")
 }

src/machine.rs

@@ -232,13 +232,15 @@ pub struct PrimitiveLayouts<'tcx> {
     pub u32: TyAndLayout<'tcx>,
     pub usize: TyAndLayout<'tcx>,
     pub bool: TyAndLayout<'tcx>,
-    pub mut_raw_ptr: TyAndLayout<'tcx>,
+    pub mut_raw_ptr: TyAndLayout<'tcx>,   // *mut ()
+    pub const_raw_ptr: TyAndLayout<'tcx>, // *const ()
 }
 
 impl<'mir, 'tcx: 'mir> PrimitiveLayouts<'tcx> {
     fn new(layout_cx: LayoutCx<'tcx, TyCtxt<'tcx>>) -> Result<Self, LayoutError<'tcx>> {
         let tcx = layout_cx.tcx;
         let mut_raw_ptr = tcx.mk_ptr(TypeAndMut { ty: tcx.types.unit, mutbl: Mutability::Mut });
+        let const_raw_ptr = tcx.mk_ptr(TypeAndMut { ty: tcx.types.unit, mutbl: Mutability::Not });
         Ok(Self {
             unit: layout_cx.layout_of(tcx.mk_unit())?,
             i8: layout_cx.layout_of(tcx.types.i8)?,
@@ -251,6 +253,7 @@ impl<'mir, 'tcx: 'mir> PrimitiveLayouts<'tcx> {
             usize: layout_cx.layout_of(tcx.types.usize)?,
             bool: layout_cx.layout_of(tcx.types.bool)?,
             mut_raw_ptr: layout_cx.layout_of(mut_raw_ptr)?,
+            const_raw_ptr: layout_cx.layout_of(const_raw_ptr)?,
         })
     }
 }
@@ -431,6 +434,17 @@ impl<'mir, 'tcx> Evaluator<'mir, 'tcx> {
         this.machine.extern_statics.try_insert(Symbol::intern(name), ptr).unwrap();
     }
 
+    fn alloc_extern_static(
+        this: &mut MiriEvalContext<'mir, 'tcx>,
+        name: &str,
+        val: ImmTy<'tcx, Provenance>,
+    ) -> InterpResult<'tcx> {
+        let place = this.allocate(val.layout, MiriMemoryKind::ExternStatic.into())?;
+        this.write_immediate(*val, &place.into())?;
+        Self::add_extern_static(this, name, place.ptr);
+        Ok(())
+    }
+
     /// Sets up the "extern statics" for this machine.
     fn init_extern_statics(this: &mut MiriEvalContext<'mir, 'tcx>) -> InterpResult<'tcx> {
         match this.tcx.sess.target.os.as_ref() {
@@ -447,10 +461,8 @@ impl<'mir, 'tcx> Evaluator<'mir, 'tcx> {
                 // syscall that we do support).
                 for name in &["__cxa_thread_atexit_impl", "getrandom", "statx", "__clock_gettime64"]
                 {
-                    let layout = this.machine.layouts.usize;
-                    let place = this.allocate(layout, MiriMemoryKind::ExternStatic.into())?;
-                    this.write_scalar(Scalar::from_machine_usize(0, this), &place.into())?;
-                    Self::add_extern_static(this, name, place.ptr);
+                    let val = ImmTy::from_int(0, this.machine.layouts.usize);
+                    Self::alloc_extern_static(this, name, val)?;
                 }
             }
             "freebsd" => {
@@ -461,13 +473,27 @@ impl<'mir, 'tcx> Evaluator<'mir, 'tcx> {
                     this.machine.env_vars.environ.unwrap().ptr,
                 );
             }
+            "android" => {
+                // "signal"
+                let layout = this.machine.layouts.const_raw_ptr;
+                let dlsym = Dlsym::from_str("signal".as_bytes(), &this.tcx.sess.target.os)?
+                    .expect("`signal` must be an actual dlsym on android");
+                let ptr = this.create_fn_alloc_ptr(FnVal::Other(dlsym));
+                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 layout = this.machine.layouts.u8;
-                let place = this.allocate(layout, MiriMemoryKind::ExternStatic.into())?;
-                this.write_scalar(Scalar::from_u8(0), &place.into())?;
-                Self::add_extern_static(this, "_tls_used", place.ptr);
+                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
         }

src/shims/unix/android/dlsym.rs

@@ -0,0 +1,53 @@
+use rustc_middle::mir;
+
+use crate::helpers::check_arg_count;
+use crate::*;
+
+#[derive(Debug, Copy, Clone)]
+#[allow(non_camel_case_types)]
+pub enum Dlsym {
+    signal,
+}
+
+impl Dlsym {
+    // Returns an error for unsupported symbols, and None if this symbol
+    // should become a NULL pointer (pretend it does not exist).
+    pub fn from_str<'tcx>(name: &str) -> InterpResult<'tcx, Option<Dlsym>> {
+        Ok(match &*name {
+            "signal" => Some(Dlsym::signal),
+            _ => throw_unsup_format!("unsupported Android dlsym: {}", name),
+        })
+    }
+}
+
+impl<'mir, 'tcx: 'mir> EvalContextExt<'mir, 'tcx> for crate::MiriEvalContext<'mir, 'tcx> {}
+pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx> {
+    fn call_dlsym(
+        &mut self,
+        dlsym: Dlsym,
+        args: &[OpTy<'tcx, Provenance>],
+        dest: &PlaceTy<'tcx, Provenance>,
+        ret: Option<mir::BasicBlock>,
+    ) -> InterpResult<'tcx> {
+        let this = self.eval_context_mut();
+        let ret = ret.expect("we don't support any diverging dlsym");
+        assert!(this.tcx.sess.target.os == "android");
+
+        match dlsym {
+            Dlsym::signal => {
+                if !this.frame_in_std() {
+                    throw_unsup_format!(
+                        "`signal` support is crude and just enough for libstd to work"
+                    );
+                }
+
+                let &[ref _sig, ref _func] = check_arg_count(args)?;
+                this.write_null(dest)?;
+            }
+        }
+
+        log::trace!("{:?}", this.dump_place(**dest));
+        this.go_to_block(ret);
+        Ok(())
+    }
+}

src/shims/unix/android/foreign_items.rs

@@ -0,0 +1,23 @@
+use rustc_span::Symbol;
+use rustc_target::spec::abi::Abi;
+
+use crate::*;
+use shims::foreign_items::EmulateByNameResult;
+
+impl<'mir, 'tcx: 'mir> EvalContextExt<'mir, 'tcx> for crate::MiriEvalContext<'mir, 'tcx> {}
+
+pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx> {
+    fn emulate_foreign_item_by_name(
+        &mut self,
+        link_name: Symbol,
+        _abi: Abi,
+        _args: &[OpTy<'tcx, Provenance>],
+        _dest: &PlaceTy<'tcx, Provenance>,
+    ) -> InterpResult<'tcx, EmulateByNameResult<'mir, 'tcx>> {
+        let _this = self.eval_context_mut();
+        match link_name.as_str() {
+            _ => return Ok(EmulateByNameResult::NotSupported),
+        }
+        //Ok(EmulateByNameResult::NeedsJumping)
+    }
+}

src/shims/unix/android/mod.rs

@@ -0,0 +1,2 @@
+pub mod dlsym;
+pub mod foreign_items;

src/shims/unix/dlsym.rs

@@ -2,26 +2,29 @@ use rustc_middle::mir;
 use rustc_target::spec::abi::Abi;
 
 use crate::*;
+use shims::unix::android::dlsym as android;
 use shims::unix::freebsd::dlsym as freebsd;
 use shims::unix::linux::dlsym as linux;
 use shims::unix::macos::dlsym as macos;
 
 #[derive(Debug, Copy, Clone)]
 pub enum Dlsym {
+    Android(android::Dlsym),
+    FreeBsd(freebsd::Dlsym),
     Linux(linux::Dlsym),
     MacOs(macos::Dlsym),
-    FreeBsd(freebsd::Dlsym),
 }
 
 impl Dlsym {
     // Returns an error for unsupported symbols, and None if this symbol
     // should become a NULL pointer (pretend it does not exist).
     pub fn from_str<'tcx>(name: &str, target_os: &str) -> InterpResult<'tcx, Option<Dlsym>> {
         Ok(match target_os {
+            "android" => android::Dlsym::from_str(name)?.map(Dlsym::Android),
+            "freebsd" => freebsd::Dlsym::from_str(name)?.map(Dlsym::FreeBsd),
             "linux" => linux::Dlsym::from_str(name)?.map(Dlsym::Linux),
             "macos" => macos::Dlsym::from_str(name)?.map(Dlsym::MacOs),
-            "freebsd" => freebsd::Dlsym::from_str(name)?.map(Dlsym::FreeBsd),
-            _ => unreachable!(),
+            _ => panic!("unsupported Unix OS {target_os}"),
         })
     }
 }
@@ -41,10 +44,12 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         this.check_abi(abi, Abi::C { unwind: false })?;
 
         match dlsym {
-            Dlsym::Linux(dlsym) => linux::EvalContextExt::call_dlsym(this, dlsym, args, dest, ret),
-            Dlsym::MacOs(dlsym) => macos::EvalContextExt::call_dlsym(this, dlsym, args, dest, ret),
+            Dlsym::Android(dlsym) =>
+                android::EvalContextExt::call_dlsym(this, dlsym, args, dest, ret),
             Dlsym::FreeBsd(dlsym) =>
                 freebsd::EvalContextExt::call_dlsym(this, dlsym, args, dest, ret),
+            Dlsym::Linux(dlsym) => linux::EvalContextExt::call_dlsym(this, dlsym, args, dest, ret),
+            Dlsym::MacOs(dlsym) => macos::EvalContextExt::call_dlsym(this, dlsym, args, dest, ret),
         }
     }
 }

src/shims/unix/foreign_items.rs

@@ -24,6 +24,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
     ) -> InterpResult<'tcx, EmulateByNameResult<'mir, 'tcx>> {
         let this = self.eval_context_mut();
 
+        #[rustfmt::skip]
         match link_name.as_str() {
             // Environment related shims
             "getenv" => {
@@ -588,11 +589,13 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
 
             // Platform-specific shims
             _ => {
-                match this.tcx.sess.target.os.as_ref() {
+                let target_os = &*this.tcx.sess.target.os;
+                match target_os {
+                    "android" => return shims::unix::android::foreign_items::EvalContextExt::emulate_foreign_item_by_name(this, link_name, abi, args, dest),
+                    "freebsd" => return shims::unix::freebsd::foreign_items::EvalContextExt::emulate_foreign_item_by_name(this, link_name, abi, args, dest),
                     "linux" => return shims::unix::linux::foreign_items::EvalContextExt::emulate_foreign_item_by_name(this, link_name, abi, args, dest),
                     "macos" => return shims::unix::macos::foreign_items::EvalContextExt::emulate_foreign_item_by_name(this, link_name, abi, args, dest),
-                    "freebsd" => return shims::unix::freebsd::foreign_items::EvalContextExt::emulate_foreign_item_by_name(this, link_name, abi, args, dest),
-                    _ => unreachable!(),
+                    _ => panic!("unsupported Unix OS {target_os}"),
                 }
             }
         };

src/shims/unix/freebsd/dlsym.rs

@@ -28,5 +28,9 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         assert!(this.tcx.sess.target.os == "freebsd");
 
         match dlsym {}
+
+        //trace!("{:?}", this.dump_place(**dest));
+        //this.go_to_block(ret);
+        //Ok(())
     }
 }

src/shims/unix/linux/dlsym.rs

@@ -32,5 +32,9 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         assert!(this.tcx.sess.target.os == "linux");
 
         match dlsym {}
+
+        //trace!("{:?}", this.dump_place(**dest));
+        //this.go_to_block(ret);
+        //Ok(())
     }
 }

src/shims/unix/mod.rs

@@ -5,6 +5,7 @@ mod fs;
 mod sync;
 mod thread;
 
+mod android;
 mod freebsd;
 mod linux;
 mod macos;

src/shims/windows/dlsym.rs

@@ -45,7 +45,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
             Dlsym::NtWriteFile => {
                 if !this.frame_in_std() {
                     throw_unsup_format!(
-                        "NtWriteFile support is crude and just enough for stdout to work"
+                        "`NtWriteFile` support is crude and just enough for stdout to work"
                     );
                 }
 
@@ -68,7 +68,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
 
                 if byte_offset != 0 {
                     throw_unsup_format!(
-                        "NtWriteFile ByteOffset paremeter is non-null, which is unsupported"
+                        "`NtWriteFile` `ByteOffset` paremeter is non-null, which is unsupported"
                     );
                 }