Environ shim

src/machine.rs

@@ -78,15 +78,21 @@ pub struct MemoryExtra {
 
     /// Whether to enforce the validity invariant.
     pub(crate) validate: bool,
+    /// Contains the `environ` static.
+    pub(crate) environ: Option<Allocation<Tag, AllocExtra>>,
 }
 
 impl MemoryExtra {
-    pub fn new(rng: StdRng, validate: bool, tracked_pointer_tag: Option<PtrId>) -> Self {
+    pub fn new(
+        rng: StdRng, validate: bool,
+        tracked_pointer_tag: Option<PtrId>,
+    ) -> Self {
         MemoryExtra {
             stacked_borrows: Rc::new(RefCell::new(GlobalState::new(tracked_pointer_tag))),
             intptrcast: Default::default(),
             rng: RefCell::new(rng),
             validate,
+            environ: None,
         }
     }
 }
@@ -266,7 +272,9 @@ impl<'mir, 'tcx> Machine<'mir, 'tcx> for Evaluator<'tcx> {
     fn find_foreign_static(
         tcx: TyCtxt<'tcx>,
         def_id: DefId,
-    ) -> InterpResult<'tcx, Cow<'tcx, Allocation>> {
+        id: AllocId,
+        memory_extra: &MemoryExtra,
+    ) -> InterpResult<'tcx, Cow<'tcx, Allocation<Tag, AllocExtra>>> {
         let attrs = tcx.get_attrs(def_id);
         let link_name = match attr::first_attr_value_str_by_name(&attrs, sym::link_name) {
             Some(name) => name.as_str(),
@@ -278,11 +286,22 @@ impl<'mir, 'tcx> Machine<'mir, 'tcx> for Evaluator<'tcx> {
                 // This should be all-zero, pointer-sized.
                 let size = tcx.data_layout.pointer_size;
                 let data = vec![0; size.bytes() as usize];
-                Allocation::from_bytes(&data, tcx.data_layout.pointer_align.abi)
+                // We got tcx memory. Let the machine initialize its "extra" stuff.
+                let (alloc, tag) = Self::init_allocation_extra(
+                    memory_extra,
+                    id, // always use the ID we got as input, not the "hidden" one.
+                    Cow::Owned(Allocation::from_bytes(&data, tcx.data_layout.pointer_align.abi)),
+                    Self::STATIC_KIND.map(MemoryKind::Machine),
+                );
+                debug_assert_eq!(tag, Self::tag_static_base_pointer(memory_extra, id));
+                alloc
+            }
+            "environ" => {
+                Cow::Owned(memory_extra.environ.as_ref().cloned().unwrap())
             }
             _ => throw_unsup_format!("can't access foreign static: {}", link_name),
         };
-        Ok(Cow::Owned(alloc))
+        Ok(alloc)
     }
 
     #[inline(always)]

src/shims/env.rs

@@ -3,6 +3,7 @@ use std::ffi::{OsString, OsStr};
 use std::env;
 
 use crate::stacked_borrows::Tag;
+use crate::rustc_target::abi::LayoutOf;
 use crate::*;
 
 use rustc::ty::layout::Size;
@@ -20,15 +21,34 @@ impl EnvVars {
         ecx: &mut InterpCx<'mir, 'tcx, Evaluator<'tcx>>,
         excluded_env_vars: Vec<String>,
     ) {
+        let mut vars = Vec::new();
         if ecx.machine.communicate {
+                // Put each environment variable pointer in `EnvVars`, collect pointers.
             for (name, value) in env::vars() {
                 if !excluded_env_vars.contains(&name) {
                     let var_ptr =
                         alloc_env_var_as_c_str(name.as_ref(), value.as_ref(), ecx);
                     ecx.machine.env_vars.map.insert(OsString::from(name), var_ptr);
+                    vars.push(var_ptr.into());
                 }
             }
         }
+        // add trailing null pointer
+        vars.push(Scalar::from_int(0, ecx.pointer_size()));
+        // Make an array with all these pointers, in the Miri memory.
+        let tcx = ecx.tcx;
+        let environ_layout =
+            ecx.layout_of(tcx.mk_array(tcx.mk_imm_ptr(tcx.types.u8), vars.len() as u64)).unwrap();
+        let environ_place = ecx.allocate(environ_layout, MiriMemoryKind::Env.into());
+        for (idx, var) in vars.into_iter().enumerate() {
+            let place = ecx.mplace_field(environ_place, idx as u64).unwrap();
+            ecx.write_scalar(var, place.into()).unwrap();
+        }
+        ecx.memory.mark_immutable(environ_place.ptr.assert_ptr().alloc_id).unwrap();
+        // A pointer to that place corresponds to the `environ` static.
+        let environ_ptr = ecx.force_ptr(environ_place.ptr).unwrap();
+        let environ_alloc = ecx.memory.get_raw(environ_ptr.alloc_id).unwrap().clone();
+        ecx.memory.extra.environ = Some(environ_alloc);
     }
 }