Auto merge of #808 - RalfJung:extra-fn, r=RalfJung

use Dlsym support to implement getentropy (and better thread spawn error)

This is the Miri side of rust-lang/rust#62245.

Fixes #789

Author: bors

rust-version

@@ -1 +1 @@
-481068a707679257e2a738b40987246e0420e787
+b820c761744db080ff7a4ba3ac88d259065cb836

src/eval.rs

@@ -11,7 +11,7 @@ use rustc::mir;
 
 use crate::{
     InterpResult, InterpError, InterpCx, StackPopCleanup, struct_error,
-    Scalar, Tag, Pointer,
+    Scalar, Tag, Pointer, FnVal,
     MemoryExtra, MiriMemoryKind, Evaluator, TlsEvalContextExt,
 };
 
@@ -93,7 +93,7 @@ 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/helpers.rs

@@ -1,8 +1,10 @@
 use std::mem;
 
-use rustc::ty::{self, layout::{self, Size}};
+use rustc::ty::{self, layout::{self, Size, Align}};
 use rustc::hir::def_id::{DefId, CRATE_DEF_INDEX};
 
+use rand::RngCore;
+
 use crate::*;
 
 impl<'mir, 'tcx> EvalContextExt<'mir, 'tcx> for crate::MiriEvalContext<'mir, 'tcx> {}
@@ -65,6 +67,40 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         })
     }
 
+    /// Generate some random bytes, and write them to `dest`.
+    fn gen_random(
+        &mut self,
+        len: usize,
+        ptr: Scalar<Tag>,
+    ) -> InterpResult<'tcx>  {
+        let this = self.eval_context_mut();
+
+        let ptr = match this.memory().check_ptr_access(ptr, Size::from_bytes(len as u64), Align::from_bytes(1).unwrap())? {
+            Some(ptr) => ptr,
+            None => return Ok(()), // zero-sized access
+        };
+
+        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)
+    }
+
     /// Visits the memory covered by `place`, sensitive to freezing: the 3rd parameter
     /// will be true if this is frozen, false if this is in an `UnsafeCell`.
     fn visit_freeze_sensitive(

src/lib.rs

@@ -31,13 +31,14 @@ pub use crate::shims::{EvalContextExt as ShimsEvalContextExt};
 pub use crate::shims::foreign_items::EvalContextExt as ForeignItemsEvalContextExt;
 pub use crate::shims::intrinsics::EvalContextExt as IntrinsicsEvalContextExt;
 pub use crate::shims::tls::{EvalContextExt as TlsEvalContextExt, TlsData};
+pub use crate::shims::dlsym::{Dlsym, EvalContextExt as DlsymEvalContextExt};
 pub use crate::operator::EvalContextExt as OperatorEvalContextExt;
 pub use crate::range_map::RangeMap;
 pub use crate::helpers::{EvalContextExt as HelpersEvalContextExt};
 pub use crate::mono_hash_map::MonoHashMap;
 pub use crate::stacked_borrows::{EvalContextExt as StackedBorEvalContextExt, Tag, Permission, Stack, Stacks, Item};
 pub use crate::machine::{
-    PAGE_SIZE, STACK_ADDR, NUM_CPUS,
+    PAGE_SIZE, STACK_ADDR, STACK_SIZE, NUM_CPUS,
     MemoryExtra, AllocExtra, MiriMemoryKind, Evaluator, MiriEvalContext, MiriEvalContextExt,
 };
 pub use crate::eval::{eval_main, create_ecx, MiriConfig};

src/machine.rs

@@ -11,14 +11,15 @@ use rand::rngs::StdRng;
 use syntax::attr;
 use syntax::symbol::sym;
 use rustc::hir::def_id::DefId;
-use rustc::ty::{self, layout::{Size, LayoutOf}, query::TyCtxtAt};
+use rustc::ty::{self, layout::{Size, LayoutOf}, TyCtxt};
 use rustc::mir;
 
 use crate::*;
 
 // Some global facts about the emulated machine.
 pub const PAGE_SIZE: u64 = 4*1024; // FIXME: adjust to target architecture
-pub const STACK_ADDR: u64 = 16*PAGE_SIZE; // not really about the "stack", but where we start assigning integer addresses to allocations
+pub const STACK_ADDR: u64 = 32*PAGE_SIZE; // not really about the "stack", but where we start assigning integer addresses to allocations
+pub const STACK_SIZE: u64 = 16*PAGE_SIZE; // whatever
 pub const NUM_CPUS: u64 = 1;
 
 /// Extra memory kinds
@@ -135,6 +136,7 @@ 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>)>;
 
@@ -145,7 +147,6 @@ impl<'mir, 'tcx> Machine<'mir, 'tcx> for Evaluator<'tcx> {
         ecx.memory().extra.validate
     }
 
-    /// Returns `Ok()` when the function was handled; fail otherwise.
     #[inline(always)]
     fn find_fn(
         ecx: &mut InterpCx<'mir, 'tcx, Self>,
@@ -157,6 +158,17 @@ impl<'mir, 'tcx> Machine<'mir, 'tcx> for Evaluator<'tcx> {
         ecx.find_fn(instance, args, dest, ret)
     }
 
+    #[inline(always)]
+    fn call_extra_fn(
+        ecx: &mut InterpCx<'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::InterpCx<'mir, 'tcx, Self>,
@@ -220,8 +232,8 @@ impl<'mir, 'tcx> Machine<'mir, 'tcx> for Evaluator<'tcx> {
     }
 
     fn find_foreign_static(
+        tcx: TyCtxt<'tcx>,
         def_id: DefId,
-        tcx: TyCtxtAt<'tcx>,
     ) -> InterpResult<'tcx, Cow<'tcx, Allocation>> {
         let attrs = tcx.get_attrs(def_id);
         let link_name = match attr::first_attr_value_str_by_name(&attrs, sym::link_name) {
@@ -251,20 +263,20 @@ impl<'mir, 'tcx> Machine<'mir, 'tcx> for Evaluator<'tcx> {
     }
 
     fn tag_allocation<'b>(
+        memory_extra: &MemoryExtra,
         id: AllocId,
         alloc: Cow<'b, Allocation>,
         kind: Option<MemoryKind<Self::MemoryKinds>>,
-        memory: &Memory<'mir, 'tcx, Self>,
     ) -> (Cow<'b, Allocation<Self::PointerTag, Self::AllocExtra>>, Self::PointerTag) {
         let kind = kind.expect("we set our STATIC_KIND so this cannot be None");
         let alloc = alloc.into_owned();
-        let (stacks, base_tag) = if !memory.extra.validate {
+        let (stacks, base_tag) = if !memory_extra.validate {
             (None, Tag::Untagged)
         } else {
             let (stacks, base_tag) = Stacks::new_allocation(
                 id,
                 Size::from_bytes(alloc.bytes.len() as u64),
-                Rc::clone(&memory.extra.stacked_borrows),
+                Rc::clone(&memory_extra.stacked_borrows),
                 kind,
             );
             (Some(stacks), base_tag)
@@ -273,18 +285,18 @@ impl<'mir, 'tcx> Machine<'mir, 'tcx> for Evaluator<'tcx> {
             assert!(alloc.relocations.is_empty(), "Only statics can come initialized with inner pointers");
             // Now we can rely on the inner pointers being static, too.
         }
-        let mut memory_extra = memory.extra.stacked_borrows.borrow_mut();
+        let mut stacked_borrows = memory_extra.stacked_borrows.borrow_mut();
         let alloc: Allocation<Tag, Self::AllocExtra> = Allocation {
             bytes: alloc.bytes,
             relocations: Relocations::from_presorted(
                 alloc.relocations.iter()
                     // The allocations in the relocations (pointers stored *inside* this allocation)
                     // all get the base pointer tag.
                     .map(|&(offset, ((), alloc))| {
-                        let tag = if !memory.extra.validate {
+                        let tag = if !memory_extra.validate {
                             Tag::Untagged
                         } else {
-                            memory_extra.static_base_ptr(alloc)
+                            stacked_borrows.static_base_ptr(alloc)
                         };
                         (offset, (tag, alloc))
                     })
@@ -302,13 +314,13 @@ impl<'mir, 'tcx> Machine<'mir, 'tcx> for Evaluator<'tcx> {
 
     #[inline(always)]
     fn tag_static_base_pointer(
+        memory_extra: &MemoryExtra,
         id: AllocId,
-        memory: &Memory<'mir, 'tcx, Self>,
     ) -> Self::PointerTag {
-        if !memory.extra.validate {
+        if !memory_extra.validate {
             Tag::Untagged
         } else {
-            memory.extra.stacked_borrows.borrow_mut().static_base_ptr(id)
+            memory_extra.stacked_borrows.borrow_mut().static_base_ptr(id)
         }
     }
 
@@ -342,8 +354,8 @@ impl<'mir, 'tcx> Machine<'mir, 'tcx> for Evaluator<'tcx> {
     }
 
     fn int_to_ptr(
-        int: u64,
         memory: &Memory<'mir, 'tcx, Self>,
+        int: u64,
     ) -> InterpResult<'tcx, Pointer<Self::PointerTag>> {
         if int == 0 {
             err!(InvalidNullPointerUsage)
@@ -355,8 +367,8 @@ impl<'mir, 'tcx> Machine<'mir, 'tcx> for Evaluator<'tcx> {
     }
 
     fn ptr_to_int(
-        ptr: Pointer<Self::PointerTag>,
         memory: &Memory<'mir, 'tcx, Self>,
+        ptr: Pointer<Self::PointerTag>,
     ) -> InterpResult<'tcx, u64> {
         if memory.extra.rng.is_none() {
             err!(ReadPointerAsBytes)

src/shims/dlsym.rs

@@ -0,0 +1,55 @@
+use rustc::mir;
+
+use crate::*;
+
+#[derive(Debug, Copy, Clone)]
+pub enum Dlsym {
+    GetEntropy,
+}
+
+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(name: &str) -> InterpResult<'static, Option<Dlsym>> {
+        use self::Dlsym::*;
+        Ok(match name {
+            "getentropy" => Some(GetEntropy),
+            "__pthread_get_minstack" => None,
+            _ =>
+                return err!(Unimplemented(format!(
+                    "Unsupported dlsym: {}", name
+                ))),
+        })
+    }
+}
+
+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(())
+    }
+}