update to FnVal changes; implement basic Dlsym support and use it for getentropy

Author: RalfJung

src/eval.rs

@@ -9,7 +9,7 @@ use rustc::mir;
 
 use crate::{
     InterpResult, InterpError, InterpretCx, StackPopCleanup, struct_error,
-    Scalar, Tag, Pointer,
+    Scalar, Tag, Pointer, FnVal,
     MemoryExtra, MiriMemoryKind, Evaluator, TlsEvalContextExt,
 };
 
@@ -84,7 +84,7 @@ pub fn create_ecx<'mir, 'tcx: 'mir>(
     let mut args = ecx.frame().body.args_iter();
 
     // First argument: pointer to `main()`.
-    let main_ptr = ecx.memory_mut().create_fn_alloc(main_instance);
+    let main_ptr = ecx.memory_mut().create_fn_alloc(FnVal::Instance(main_instance));
     let dest = ecx.eval_place(&mir::Place::Base(mir::PlaceBase::Local(args.next().unwrap())))?;
     ecx.write_scalar(Scalar::Ptr(main_ptr), dest)?;
 

src/lib.rs

@@ -30,6 +30,7 @@ pub use rustc_mir::interpret::{self, AllocMap, PlaceTy};
 
 pub use crate::shims::foreign_items::EvalContextExt as ForeignItemsEvalContextExt;
 pub use crate::shims::intrinsics::EvalContextExt as IntrinsicsEvalContextExt;
+pub use crate::shims::dlsym::{Dlsym, EvalContextExt as DlsymEvalContextExt};
 pub use crate::operator::EvalContextExt as OperatorEvalContextExt;
 pub use crate::tls::{EvalContextExt as TlsEvalContextExt, TlsData};
 pub use crate::range_map::RangeMap;

src/machine.rs

@@ -128,6 +128,7 @@ impl<'mir, 'tcx> Machine<'mir, 'tcx> for Evaluator<'tcx> {
     type MemoryExtra = MemoryExtra;
     type AllocExtra = AllocExtra;
     type PointerTag = Tag;
+    type ExtraFnVal = Dlsym;
 
     type MemoryMap = MonoHashMap<AllocId, (MemoryKind<MiriMemoryKind>, Allocation<Tag, Self::AllocExtra>)>;
 
@@ -138,7 +139,6 @@ impl<'mir, 'tcx> Machine<'mir, 'tcx> for Evaluator<'tcx> {
         ecx.machine.validate
     }
 
-    /// Returns `Ok()` when the function was handled; fail otherwise.
     #[inline(always)]
     fn find_fn(
         ecx: &mut InterpretCx<'mir, 'tcx, Self>,
@@ -150,6 +150,17 @@ impl<'mir, 'tcx> Machine<'mir, 'tcx> for Evaluator<'tcx> {
         ecx.find_fn(instance, args, dest, ret)
     }
 
+    #[inline(always)]
+    fn call_extra_fn(
+        ecx: &mut InterpretCx<'mir, 'tcx, Self>,
+        fn_val: Dlsym,
+        args: &[OpTy<'tcx, Tag>],
+        dest: Option<PlaceTy<'tcx, Tag>>,
+        ret: Option<mir::BasicBlock>,
+    ) -> InterpResult<'tcx> {
+        ecx.call_dlsym(fn_val, args, dest, ret)
+    }
+
     #[inline(always)]
     fn call_intrinsic(
         ecx: &mut rustc_mir::interpret::InterpretCx<'mir, 'tcx, Self>,

src/shims/dlsym.rs

@@ -0,0 +1,49 @@
+use rustc::mir;
+
+use crate::*;
+
+#[derive(Debug, Copy, Clone)]
+pub enum Dlsym {
+    GetEntropy,
+}
+
+impl Dlsym {
+    pub fn from_str(name: &str) -> Option<Dlsym> {
+        use self::Dlsym::*;
+        Some(match name {
+            "getentropy" => GetEntropy,
+            _ => return None,
+        })
+    }
+}
+
+impl<'mir, 'tcx> 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, Tag>],
+        dest: Option<PlaceTy<'tcx, Tag>>,
+        ret: Option<mir::BasicBlock>,
+    ) -> InterpResult<'tcx> {
+        use self::Dlsym::*;
+
+        let this = self.eval_context_mut();
+
+        let dest = dest.expect("we don't support any diverging dlsym");
+        let ret = ret.expect("dest is `Some` but ret is `None`");
+        
+        match dlsym {
+            GetEntropy => {
+                let ptr = this.read_scalar(args[0])?.not_undef()?;
+                let len = this.read_scalar(args[1])?.to_usize(this)?;
+                this.gen_random(len as usize, ptr)?;
+                this.write_null(dest)?;
+            }
+        }
+
+        this.goto_block(Some(ret))?;
+        this.dump_place(*dest);
+        Ok(())
+    }
+}

src/shims/foreign_items.rs

@@ -311,7 +311,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                         // neither of which have any effect on our current PRNG
                         let _flags = this.read_scalar(args[3])?.to_i32()?;
 
-                        gen_random(this, len as usize, ptr)?;
+                        this.gen_random(len as usize, ptr)?;
                         this.write_scalar(Scalar::from_uint(len, dest.layout.size), dest)?;
                     }
                     id => {
@@ -328,10 +328,14 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 let symbol_name = this.memory().get(symbol.alloc_id)?.read_c_str(tcx, symbol)?;
                 let err = format!("bad c unicode symbol: {:?}", symbol_name);
                 let symbol_name = ::std::str::from_utf8(symbol_name).unwrap_or(&err);
-                return err!(Unimplemented(format!(
-                    "miri does not support dynamically loading libraries (requested symbol: {})",
-                    symbol_name
-                )));
+                if let Some(dlsym) = Dlsym::from_str(symbol_name) {
+                    let ptr = this.memory_mut().create_fn_alloc(FnVal::Other(dlsym));
+                    this.write_scalar(Scalar::from(ptr), dest)?;
+                } else {
+                    return err!(Unimplemented(format!(
+                        "Unsupported dlsym: {}", symbol_name
+                    )));
+                }
             }
 
             "__rust_maybe_catch_panic" => {
@@ -344,7 +348,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 // We abort on panic, so not much is going on here, but we still have to call the closure.
                 let f = this.read_scalar(args[0])?.to_ptr()?;
                 let data = this.read_scalar(args[1])?.not_undef()?;
-                let f_instance = this.memory().get_fn(f)?;
+                let f_instance = this.memory().get_fn(f)?.as_instance()?;
                 this.write_null(dest)?;
                 trace!("__rust_maybe_catch_panic: {:?}", f_instance);
 
@@ -663,7 +667,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
 
                 // Extract the function type out of the signature (that seems easier than constructing it ourselves).
                 let dtor = match this.read_scalar(args[1])?.not_undef()? {
-                    Scalar::Ptr(dtor_ptr) => Some(this.memory().get_fn(dtor_ptr)?),
+                    Scalar::Ptr(dtor_ptr) => Some(this.memory().get_fn(dtor_ptr)?.as_instance()?),
                     Scalar::Raw { data: 0, size } => {
                         // NULL pointer
                         assert_eq!(size as u64, this.memory().pointer_size().bytes());
@@ -775,7 +779,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
             "SecRandomCopyBytes" => {
                 let len = this.read_scalar(args[1])?.to_usize(this)?;
                 let ptr = this.read_scalar(args[2])?.not_undef()?;
-                gen_random(this, len as usize, ptr)?;
+                this.gen_random(len as usize, ptr)?;
                 this.write_null(dest)?;
             }
 
@@ -936,7 +940,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
             "SystemFunction036" => {
                 let ptr = this.read_scalar(args[0])?.not_undef()?;
                 let len = this.read_scalar(args[1])?.to_u32()?;
-                gen_random(this, len as usize, ptr)?;
+                this.gen_random(len as usize, ptr)?;
                 this.write_scalar(Scalar::from_bool(true), dest)?;
             }
 
@@ -972,36 +976,37 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         }
         return Ok(None);
     }
-}
-
-fn gen_random<'mir, 'tcx>(
-    this: &mut MiriEvalContext<'mir, 'tcx>,
-    len: usize,
-    dest: Scalar<Tag>,
-) -> InterpResult<'tcx>  {
-    if len == 0 {
-        // Nothing to do
-        return Ok(());
-    }
-    let ptr = dest.to_ptr()?;
-
-    let data = match &mut this.memory_mut().extra.rng {
-        Some(rng) => {
-            let mut rng = rng.borrow_mut();
-            let mut data = vec![0; len];
-            rng.fill_bytes(&mut data);
-            data
-        }
-        None => {
-            return err!(Unimplemented(
-                "miri does not support gathering system entropy in deterministic mode!
-                Use '-Zmiri-seed=<seed>' to enable random number generation.
-                WARNING: Miri does *not* generate cryptographically secure entropy -
-                do not use Miri to run any program that needs secure random number generation".to_owned(),
-            ));
+
+    fn gen_random(
+        &mut self,
+        len: usize,
+        dest: Scalar<Tag>,
+    ) -> InterpResult<'tcx>  {
+        if len == 0 {
+            // Nothing to do
+            return Ok(());
         }
-    };
-    let tcx = &{this.tcx.tcx};
-    this.memory_mut().get_mut(ptr.alloc_id)?
-        .write_bytes(tcx, ptr, &data)
-}
+        let this = self.eval_context_mut();
+        let ptr = dest.to_ptr()?;
+
+        let data = match &mut this.memory_mut().extra.rng {
+            Some(rng) => {
+                let mut rng = rng.borrow_mut();
+                let mut data = vec![0; len];
+                rng.fill_bytes(&mut data);
+                data
+            }
+            None => {
+                return err!(Unimplemented(
+                    "miri does not support gathering system entropy in deterministic mode!
+                    Use '-Zmiri-seed=<seed>' to enable random number generation.
+                    WARNING: Miri does *not* generate cryptographically secure entropy -
+                    do not use Miri to run any program that needs secure random number generation".to_owned(),
+                ));
+            }
+        };
+        let tcx = &{this.tcx.tcx};
+        this.memory_mut().get_mut(ptr.alloc_id)?
+            .write_bytes(tcx, ptr, &data)
+    }
+}

src/shims/mod.rs

@@ -1,2 +1,3 @@
 pub mod foreign_items;
 pub mod intrinsics;
+pub mod dlsym;