Implement non-deterministc mode

Cargo.toml

@@ -44,6 +44,8 @@ shell-escape = "0.1.4"
 # See the `src/tools/rustc-workspace-hack/README.md` file in `rust-lang/rust`
 # for more information.
 rustc-workspace-hack = "1.0.0"
+hex = "0.3.2"
+rand = "0.6.5"
 
 [build-dependencies]
 vergen = "3"

benches/helpers/miri_helper.rs

@@ -24,7 +24,7 @@ impl rustc_driver::Callbacks for MiriCompilerCalls<'_> {
             );
 
             self.bencher.iter(|| {
-                let config = miri::MiriConfig { validate: true, args: vec![] };
+                let config = miri::MiriConfig { validate: true, args: vec![], seed: None };
                 eval_main(tcx, entry_def_id, config);
             });
         });

src/bin/miri-rustc-tests.rs

@@ -48,7 +48,7 @@ impl rustc_driver::Callbacks for MiriCompilerCalls {
                     fn visit_item(&mut self, i: &'hir hir::Item) {
                         if let hir::ItemKind::Fn(.., body_id) = i.node {
                             if i.attrs.iter().any(|attr| attr.check_name("test")) {
-                                let config = MiriConfig { validate: true, args: vec![] };
+                                let config = MiriConfig { validate: true, args: vec![], seed: None };
                                 let did = self.0.hir().body_owner_def_id(body_id);
                                 println!("running test: {}", self.0.def_path_debug_str(did));
                                 miri::eval_main(self.0, did, config);
@@ -61,7 +61,7 @@ impl rustc_driver::Callbacks for MiriCompilerCalls {
                 }
                 tcx.hir().krate().visit_all_item_likes(&mut Visitor(tcx));
             } else if let Some((entry_def_id, _)) = tcx.entry_fn(LOCAL_CRATE) {
-                let config = MiriConfig { validate: true, args: vec![] };
+                let config = MiriConfig { validate: true, args: vec![], seed: None };
                 miri::eval_main(tcx, entry_def_id, config);
 
                 compiler.session().abort_if_errors();

src/bin/miri.rs

@@ -126,6 +126,7 @@ fn main() {
 
     // Parse our arguments and split them across `rustc` and `miri`.
     let mut validate = true;
+    let mut seed: Option<u64> = None;
     let mut rustc_args = vec![];
     let mut miri_args = vec![];
     let mut after_dashdash = false;
@@ -145,6 +146,20 @@ fn main() {
                 "--" => {
                     after_dashdash = true;
                 }
+                arg if arg.starts_with("-Zmiri-seed=") => {
+                    if seed.is_some() {
+                        panic!("Cannot specify -Zmiri-seed multiple times!");
+                    }
+                    let seed_raw = hex::decode(arg.trim_start_matches("-Zmiri-seed=")).unwrap();
+                    if seed_raw.len() > 8 {
+                        panic!(format!("-Zmiri-seed must be at most 8 bytes, was {}", seed_raw.len()));
+                    }
+
+                    let mut bytes = [0; 8];
+                    bytes[..seed_raw.len()].copy_from_slice(&seed_raw);
+                    seed = Some(u64::from_be_bytes(bytes));
+
+                },
                 _ => {
                     rustc_args.push(arg);
                 }
@@ -163,7 +178,7 @@ fn main() {
 
     debug!("rustc arguments: {:?}", rustc_args);
     debug!("miri arguments: {:?}", miri_args);
-    let miri_config = miri::MiriConfig { validate, args: miri_args };
+    let miri_config = miri::MiriConfig { validate, args: miri_args, seed };
     let result = rustc_driver::report_ices_to_stderr_if_any(move || {
         rustc_driver::run_compiler(&rustc_args, &mut MiriCompilerCalls { miri_config }, None, None)
     }).and_then(|result| result);

src/fn_call.rs

@@ -4,6 +4,8 @@ use rustc::hir::def_id::DefId;
 use rustc::mir;
 use syntax::attr;
 
+use rand::RngCore;
+
 use crate::*;
 
 impl<'a, 'mir, 'tcx> EvalContextExt<'a, 'mir, 'tcx> for crate::MiriEvalContext<'a, 'mir, 'tcx> {}
@@ -224,16 +226,26 @@ pub trait EvalContextExt<'a, 'mir, 'tcx: 'a + 'mir>: crate::MiriEvalContextExt<'
             }
 
             "syscall" => {
-                // TODO: read `syscall` IDs like `sysconf` IDs and
-                // figure out some way to actually process some of them.
-                //
+                let sys_getrandom = this.eval_path_scalar(&["libc", "SYS_getrandom"])?
+                    .expect("Failed to get libc::SYS_getrandom")
+                    .to_usize(this)?;
+
                 // `libc::syscall(NR_GETRANDOM, buf.as_mut_ptr(), buf.len(), GRND_NONBLOCK)`
-                // is called if a `HashMap` is created the regular way.
+                // is called if a `HashMap` is created the regular way (e.g. HashMap<K, V>).
                 match this.read_scalar(args[0])?.to_usize(this)? {
-                    318 | 511 => {
-                        return err!(Unimplemented(
-                            "miri does not support random number generators".to_owned(),
-                        ))
+                    id if id == sys_getrandom => {
+                        let ptr = this.read_scalar(args[1])?.to_ptr()?;
+                        let len = this.read_scalar(args[2])?.to_usize(this)?;
+
+                        // The only supported flags are GRND_RANDOM and GRND_NONBLOCK,
+                        // neither of which have any effect on our current PRNG
+                        let _flags = this.read_scalar(args[3])?.to_i32()?;
+
+                        let data = gen_random(this, len as usize)?;
+                        this.memory_mut().get_mut(ptr.alloc_id)?
+                                    .write_bytes(tcx, ptr, &data)?;
+
+                        this.write_scalar(Scalar::from_uint(len, dest.layout.size), dest)?;
                     }
                     id => {
                         return err!(Unimplemented(
@@ -499,18 +511,13 @@ pub trait EvalContextExt<'a, 'mir, 'tcx: 'a + 'mir>: crate::MiriEvalContextExt<'
                 ];
                 let mut result = None;
                 for &(path, path_value) in paths {
-                    if let Ok(instance) = this.resolve_path(path) {
-                        let cid = GlobalId {
-                            instance,
-                            promoted: None,
-                        };
-                        let const_val = this.const_eval_raw(cid)?;
-                        let const_val = this.read_scalar(const_val.into())?;
-                        let value = const_val.to_i32()?;
-                        if value == name {
+                    if let Some(val) = this.eval_path_scalar(path)? {
+                        let val = val.to_i32()?;
+                        if val == name {
                             result = Some(path_value);
                             break;
                         }
+
                     }
                 }
                 if let Some(result) = result {
@@ -757,6 +764,17 @@ pub trait EvalContextExt<'a, 'mir, 'tcx: 'a + 'mir>: crate::MiriEvalContextExt<'
             "GetCommandLineW" => {
                 this.write_scalar(Scalar::Ptr(this.machine.cmd_line.unwrap()), dest)?;
             }
+            // The actual name of 'RtlGenRandom'
+            "SystemFunction036" => {
+                let ptr = this.read_scalar(args[0])?.to_ptr()?;
+                let len = this.read_scalar(args[1])?.to_usize(this)?;
+
+                let data = gen_random(this, len as usize)?;
+                this.memory_mut().get_mut(ptr.alloc_id)?
+                    .write_bytes(tcx, ptr, &data)?;
+
+                this.write_scalar(Scalar::from_bool(true), dest)?;
+            }
 
             // We can't execute anything else.
             _ => {
@@ -774,4 +792,42 @@ pub trait EvalContextExt<'a, 'mir, 'tcx: 'a + 'mir>: crate::MiriEvalContextExt<'
     fn write_null(&mut self, dest: PlaceTy<'tcx, Borrow>) -> EvalResult<'tcx> {
         self.eval_context_mut().write_scalar(Scalar::from_int(0, dest.layout.size), dest)
     }
+
+    /// Evaluates the scalar at the specified path. Returns Some(val)
+    /// if the path could be resolved, and None otherwise
+    fn eval_path_scalar(&mut self, path: &[&str]) -> EvalResult<'tcx, Option<ScalarMaybeUndef<stacked_borrows::Borrow>>> {
+        let this = self.eval_context_mut();
+        if let Ok(instance) = this.resolve_path(path) {
+            let cid = GlobalId {
+                instance,
+                promoted: None,
+            };
+            let const_val = this.const_eval_raw(cid)?;
+            let const_val = this.read_scalar(const_val.into())?;
+            return Ok(Some(const_val));
+        }
+        return Ok(None);
+    }
+}
+
+fn gen_random<'a, 'mir, 'tcx>(
+    this: &mut MiriEvalContext<'a, 'mir, 'tcx>,
+    len: usize,
+) -> Result<Vec<u8>, EvalError<'tcx>>  {
+
+    match &mut this.machine.rng {
+        Some(rng) => {
+            let mut data = vec![0; len];
+            rng.fill_bytes(&mut data);
+            Ok(data)
+        }
+        None => {
+            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(),
+            ))
+        }
+    }
 }

src/lib.rs

@@ -24,6 +24,9 @@ mod stacked_borrows;
 use std::collections::HashMap;
 use std::borrow::Cow;
 
+use rand::rngs::StdRng;
+use rand::SeedableRng;
+
 use rustc::ty::{self, TyCtxt, query::TyCtxtAt};
 use rustc::ty::layout::{LayoutOf, Size, Align};
 use rustc::hir::{self, def_id::DefId};
@@ -60,6 +63,9 @@ pub fn miri_default_args() -> &'static [&'static str] {
 pub struct MiriConfig {
     pub validate: bool,
     pub args: Vec<String>,
+
+    // The seed to use when non-determinism is required (e.g. getrandom())
+    pub seed: Option<u64>
 }
 
 // Used by priroda.
@@ -71,7 +77,7 @@ pub fn create_ecx<'a, 'mir: 'a, 'tcx: 'mir>(
     let mut ecx = InterpretCx::new(
         tcx.at(syntax::source_map::DUMMY_SP),
         ty::ParamEnv::reveal_all(),
-        Evaluator::new(config.validate),
+        Evaluator::new(config.validate, config.seed),
     );
 
     let main_instance = ty::Instance::mono(ecx.tcx.tcx, main_id);
@@ -326,10 +332,14 @@ pub struct Evaluator<'tcx> {
 
     /// Stacked Borrows state.
     pub(crate) stacked_borrows: stacked_borrows::State,
+
+    /// The random number generator to use if Miri
+    /// is running in non-deterministic mode
+    pub(crate) rng: Option<StdRng>
 }
 
 impl<'tcx> Evaluator<'tcx> {
-    fn new(validate: bool) -> Self {
+    fn new(validate: bool, seed: Option<u64>) -> Self {
         Evaluator {
             env_vars: HashMap::default(),
             argc: None,
@@ -339,6 +349,7 @@ impl<'tcx> Evaluator<'tcx> {
             tls: TlsData::default(),
             validate,
             stacked_borrows: stacked_borrows::State::default(),
+            rng: seed.map(|s| StdRng::seed_from_u64(s))
         }
     }
 }

tests/compile-fail/getrandom.rs

@@ -0,0 +1,13 @@
+// ignore-macos
+// ignore-windows
+
+#![feature(rustc_private)]
+extern crate libc;
+
+fn main() {
+    let mut buf = [0u8; 5];
+    unsafe {
+        libc::syscall(libc::SYS_getrandom, buf.as_mut_ptr() as *mut libc::c_void, 5 as libc::size_t, 0 as libc::c_uint);
+        //~^ ERROR constant evaluation error: miri does not support gathering system entropy in deterministic mode!
+    }
+}

tests/run-pass/hashmap.rs

@@ -1,8 +1,9 @@
+// compile-flags: -Zmiri-seed=0000000000000000
+
 use std::collections::{self, HashMap};
-use std::hash::BuildHasherDefault;
+use std::hash::{BuildHasherDefault, BuildHasher};
 
-fn main() {
-    let mut map : HashMap<i32, i32, BuildHasherDefault<collections::hash_map::DefaultHasher>> = Default::default();
+fn test_map<S: BuildHasher>(mut map: HashMap<i32, i32, S>) {
     map.insert(0, 0);
     assert_eq!(map.values().fold(0, |x, y| x+y), 0);
 
@@ -22,4 +23,16 @@ fn main() {
     assert_eq!(map.values().fold(0, |x, y| x+y), num*(num-1)/2);
 
     // TODO: Test Entry API, Iterators, ...
+
+}
+
+fn main() {
+    // TODO: Implement random number generation on OS X
+    if cfg!(not(target_os = "macos")) {
+        let map_normal: HashMap<i32, i32> = HashMap::new();
+        test_map(map_normal);
+    } else {
+        let map : HashMap<i32, i32, BuildHasherDefault<collections::hash_map::DefaultHasher>> = Default::default();
+        test_map(map);
+    }
 }