diff --git a/bench-cargo-miri/mse/src/main.rs b/bench-cargo-miri/mse/src/main.rs
index 696de93442..b4ad157510 100644
--- a/bench-cargo-miri/mse/src/main.rs
+++ b/bench-cargo-miri/mse/src/main.rs
@@ -2,7 +2,7 @@ static EXPECTED: &[u8] = &[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
 static PCM: &[i16] = &[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, -2, 0, -2, 0, -2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 1, 0, 1, 0, 0, -2, 0, -2, 0, -2, 0, -2, -2, -2, -3, -3, -3, -3, -4, -2, -5, -2, -5, -2, -4, 0, -4, 0, -4, 0, -4, 1, -4, 1, -4, 2, -4, 2, -4, 2, -4, 2, -4, 2, -3, 1, -4, 0, -4, 0, -5, 0, -5, 0, -5, 0, -4, 2, -4, 3, -4, 4, -3, 5, -2, 5, -3, 6, -3, 6, -3, 5, -3, 5, -2, 4, -2, 3, -5, 0, -6, 0, -3, -2, -4, -4, -9, -5, -9, -4, -4, -2, -4, -2, -4, 0, -2, 1, 1, 1, 4, 2, 8, 2, 12, 1, 13, 0, 12, 0, 11, 0, 8, -2, 7, 0, 7, -3, 11, -8, 15, -9, 17, -6, 17, -5, 13, -3, 7, 0, 3, 0, -2, 0, -4, 0, -4, -2, -6, 0, -14, -2, -17, -4, -8, 0, -7, 5, -17, 7, -18, 10, -7, 18, -2, 25, -3, 27, 0, 31, 4, 34, 4, 34, 8, 36, 8, 37, 2, 36, 4, 34, 8, 28, 3, 15, 0, 11, 0, 12, -5, 8, -4, 10, 0, 23, -4, 31, -8, 30, -2, 30, 0, 26, -6, 22, -6, 20, -12, 15, -19, 10, -10, 13, -14, 6, -43, -13, -43, -16, -9, -12, -10, -29, -42, -40, -37, -28, -5, -21, 1, -24, -8, -20, 4, -18, 26, -24, 44, -26, 66, -30, 86, -37, 88, -41, 72, -46, 50, -31, 28, 23, 14, 64, 16, 51, 26, 32, 34, 39, 42, 48, 35, 58, 0, 72, -36, 69, -59, 58, -98, 54, -124, 36, -103, 12, -110, 5, -173, -19, -146, -59, -4, -42, 51, 1, -23, -6, -30, -6, 45, 46, 47, 70, 6, 55, 19, 60, 38, 62, 42, 47, 61, 46, 40, 42, -19, 22, -34, 6, -35, -50, -61, -141, -37, -171, 17, -163, 26, -180, 46, -154, 80, -63, 48, -4, 18, 20, 50, 47, 58, 53, 44, 61, 57, 85, 37, 80, 0, 86, -8, 106, -95, 49, -213, -8, -131, 47, 49, 63, 40, -39, -69, -74, -37, -20, 63, -12, 58, -14, -12, 25, -31, 41, 11, 45, 76, 47, 167, 5, 261, -37, 277, -83, 183, -172, 35, -122, -79, 138, -70, 266, 69, 124, 228, 0, 391, -29, 594, -84, 702, -78, 627, -8, 551, -13, 509, 13, 372, 120, 352, 125, 622, 127, 691, 223, 362, 126, 386, -33, 915, 198, 958, 457, 456, 298, 500, 233, 1027, 469, 1096, 426, 918, 160, 1067, 141, 1220, 189, 1245, 164, 1375, 297, 1378, 503, 1299, 702, 1550, 929, 1799, 855, 1752, 547, 1830, 602, 1928, 832, 1736, 796, 1735, 933, 1961, 1385, 1935, 1562, 2105, 1485, 2716, 1449, 2948, 1305, 2768, 1205, 2716, 1346, 2531, 1450, 2470, 1653, 3117, 2111, 3370, 2176, 2696, 1947, 2925, 2305, 3846, 2658, 2425, 2184, -877, 1981, -2261, 2623, -1645, 2908, -1876, 2732, -2704, 2953, -2484, 3116, -2120, 2954, -2442, 3216, -2466, 3499, -2192, 3234, -2392, 3361, -2497, 3869, -2078, 3772, -1858, 3915, -2066, 4438, -2285, 2934, -2294, -280, -2066, -1762, -1992, -1412, -2298, -1535, -2399, -1789, -2223, -1419, -2244, -1334, -2092, -1476, -1777, -1396, -2014, -1571, -2199, -1574, -1843, -1167, -1910, -1446, -2007, -1818];
 
 fn main() {
-    for i in 0..5 {
+    for _ in 0..2 {
         mse(PCM.len(), PCM, EXPECTED);
     }
 }
diff --git a/rust-version b/rust-version
index f28fce1af2..82d8da1d03 100644
--- a/rust-version
+++ b/rust-version
@@ -1 +1 @@
-d9051341a1c142542a3f7dab509266606c775382
+e86c9e6ef8be7ddec0360f20aae7d86c69c59a83
diff --git a/src/eval.rs b/src/eval.rs
index cc02100dd3..267b79d0eb 100644
--- a/src/eval.rs
+++ b/src/eval.rs
@@ -58,6 +58,7 @@ pub fn create_ecx<'mir, 'tcx: 'mir>(
         ),
     );
     // Complete initialization.
+    MemoryExtra::init_extern_statics(&mut ecx)?;
     EnvVars::init(&mut ecx, config.excluded_env_vars);
 
     // Setup first stack-frame
@@ -90,14 +91,14 @@ pub fn create_ecx<'mir, 'tcx: 'mir>(
             // Make space for `0` terminator.
             let size = arg.len() as u64 + 1;
             let arg_type = tcx.mk_array(tcx.types.u8, size);
-            let arg_place = ecx.allocate(ecx.layout_of(arg_type)?, MiriMemoryKind::Env.into());
+            let arg_place = ecx.allocate(ecx.layout_of(arg_type)?, MiriMemoryKind::Machine.into());
             ecx.write_os_str_to_c_str(OsStr::new(arg), arg_place.ptr, size)?;
             argvs.push(arg_place.ptr);
         }
         // Make an array with all these pointers, in the Miri memory.
         let argvs_layout =
             ecx.layout_of(tcx.mk_array(tcx.mk_imm_ptr(tcx.types.u8), argvs.len() as u64))?;
-        let argvs_place = ecx.allocate(argvs_layout, MiriMemoryKind::Env.into());
+        let argvs_place = ecx.allocate(argvs_layout, MiriMemoryKind::Machine.into());
         for (idx, arg) in argvs.into_iter().enumerate() {
             let place = ecx.mplace_field(argvs_place, idx as u64)?;
             ecx.write_scalar(arg, place.into())?;
@@ -108,13 +109,13 @@ pub fn create_ecx<'mir, 'tcx: 'mir>(
         // Store `argc` and `argv` for macOS `_NSGetArg{c,v}`.
         {
             let argc_place =
-                ecx.allocate(ecx.layout_of(tcx.types.isize)?, MiriMemoryKind::Env.into());
+                ecx.allocate(ecx.layout_of(tcx.types.isize)?, MiriMemoryKind::Machine.into());
             ecx.write_scalar(argc, argc_place.into())?;
             ecx.machine.argc = Some(argc_place.ptr);
 
             let argv_place = ecx.allocate(
                 ecx.layout_of(tcx.mk_imm_ptr(tcx.types.unit))?,
-                MiriMemoryKind::Env.into(),
+                MiriMemoryKind::Machine.into(),
             );
             ecx.write_scalar(argv, argv_place.into())?;
             ecx.machine.argv = Some(argv_place.ptr);
@@ -134,7 +135,7 @@ pub fn create_ecx<'mir, 'tcx: 'mir>(
 
             let cmd_utf16: Vec<u16> = cmd.encode_utf16().collect();
             let cmd_type = tcx.mk_array(tcx.types.u16, cmd_utf16.len() as u64);
-            let cmd_place = ecx.allocate(ecx.layout_of(cmd_type)?, MiriMemoryKind::Env.into());
+            let cmd_place = ecx.allocate(ecx.layout_of(cmd_type)?, MiriMemoryKind::Machine.into());
             ecx.machine.cmd_line = Some(cmd_place.ptr);
             // Store the UTF-16 string. We just allocated so we know the bounds are fine.
             let char_size = Size::from_bytes(2);
@@ -147,7 +148,7 @@ pub fn create_ecx<'mir, 'tcx: 'mir>(
     };
 
     // Return place (in static memory so that it does not count as leak).
-    let ret_place = ecx.allocate(ecx.layout_of(tcx.types.isize)?, MiriMemoryKind::Env.into());
+    let ret_place = ecx.allocate(ecx.layout_of(tcx.types.isize)?, MiriMemoryKind::Machine.into());
     // Call start function.
     ecx.call_function(
         start_instance,
@@ -158,7 +159,7 @@ pub fn create_ecx<'mir, 'tcx: 'mir>(
 
     // Set the last_error to 0
     let errno_layout = ecx.layout_of(tcx.types.u32)?;
-    let errno_place = ecx.allocate(errno_layout, MiriMemoryKind::Env.into());
+    let errno_place = ecx.allocate(errno_layout, MiriMemoryKind::Machine.into());
     ecx.write_scalar(Scalar::from_u32(0), errno_place.into())?;
     ecx.machine.last_error = Some(errno_place);
 
diff --git a/src/intptrcast.rs b/src/intptrcast.rs
index 059d8217fa..375ebf0996 100644
--- a/src/intptrcast.rs
+++ b/src/intptrcast.rs
@@ -5,7 +5,7 @@ use std::collections::{hash_map::Entry, HashMap};
 use rand::Rng;
 
 use rustc::ty::layout::HasDataLayout;
-use rustc_mir::interpret::{AllocCheck, AllocId, InterpResult, Memory, Pointer, PointerArithmetic};
+use rustc_mir::interpret::{AllocCheck, AllocId, InterpResult, Memory, Machine, Pointer, PointerArithmetic};
 use rustc_target::abi::Size;
 
 use crate::{Evaluator, Tag, STACK_ADDR};
@@ -80,12 +80,13 @@ impl<'mir, 'tcx> GlobalState {
     ) -> InterpResult<'tcx, u64> {
         let mut global_state = memory.extra.intptrcast.borrow_mut();
         let global_state = &mut *global_state;
+        let id = Evaluator::canonical_alloc_id(memory, ptr.alloc_id);
 
         // There is nothing wrong with a raw pointer being cast to an integer only after
         // it became dangling.  Hence `MaybeDead`.
-        let (size, align) = memory.get_size_and_align(ptr.alloc_id, AllocCheck::MaybeDead)?;
+        let (size, align) = memory.get_size_and_align(id, AllocCheck::MaybeDead)?;
 
-        let base_addr = match global_state.base_addr.entry(ptr.alloc_id) {
+        let base_addr = match global_state.base_addr.entry(id) {
             Entry::Occupied(entry) => *entry.get(),
             Entry::Vacant(entry) => {
                 // This allocation does not have a base address yet, pick one.
@@ -102,7 +103,7 @@ impl<'mir, 'tcx> GlobalState {
                 trace!(
                     "Assigning base address {:#x} to allocation {:?} (slack: {}, align: {})",
                     base_addr,
-                    ptr.alloc_id,
+                    id,
                     slack,
                     align.bytes(),
                 );
@@ -112,7 +113,7 @@ impl<'mir, 'tcx> GlobalState {
                 global_state.next_base_addr = base_addr.checked_add(max(size.bytes(), 1)).unwrap();
                 // Given that `next_base_addr` increases in each allocation, pushing the
                 // corresponding tuple keeps `int_to_ptr_map` sorted
-                global_state.int_to_ptr_map.push((base_addr, ptr.alloc_id));
+                global_state.int_to_ptr_map.push((base_addr, id));
 
                 base_addr
             }
diff --git a/src/machine.rs b/src/machine.rs
index b5c76070ae..331e75414a 100644
--- a/src/machine.rs
+++ b/src/machine.rs
@@ -3,6 +3,7 @@
 
 use std::borrow::Cow;
 use std::cell::RefCell;
+use std::collections::HashMap;
 use std::num::NonZeroU64;
 use std::rc::Rc;
 
@@ -12,10 +13,9 @@ use rustc::mir;
 use rustc::ty::{
     self,
     layout::{LayoutOf, Size},
-    Ty, TyCtxt,
+    Ty,
 };
 use rustc_ast::attr;
-use rustc_hir::def_id::DefId;
 use rustc_span::{source_map::Span, symbol::sym};
 
 use crate::*;
@@ -48,8 +48,8 @@ pub enum MiriMemoryKind {
     C,
     /// Windows `HeapAlloc` memory.
     WinHeap,
-    /// Memory for env vars and args, errno and other parts of the machine-managed environment.
-    Env,
+    /// Memory for env vars and args, errno, extern statics and other parts of the machine-managed environment.
+    Machine,
     /// Rust statics.
     Static,
 }
@@ -74,7 +74,11 @@ pub struct MemoryExtra {
     pub stacked_borrows: Option<stacked_borrows::MemoryExtra>,
     pub intptrcast: intptrcast::MemoryExtra,
 
+    /// Mapping extern static names to their canonical allocation.
+    pub(crate) extern_statics: HashMap<&'static str, AllocId>,
+
     /// The random number generator used for resolving non-determinism.
+    /// Needs to be queried by ptr_to_int, hence needs interior mutability.
     pub(crate) rng: RefCell<StdRng>,
 }
 
@@ -85,7 +89,34 @@ impl MemoryExtra {
         } else {
             None
         };
-        MemoryExtra { stacked_borrows, intptrcast: Default::default(), rng: RefCell::new(rng) }
+        MemoryExtra {
+            stacked_borrows,
+            intptrcast: Default::default(),
+            extern_statics: HashMap::default(),
+            rng: RefCell::new(rng),
+        }
+    }
+
+    /// Sets up the "extern statics" for this machine.
+    pub fn init_extern_statics<'mir, 'tcx>(
+        this: &mut MiriEvalContext<'mir, 'tcx>,
+    ) -> InterpResult<'tcx> {
+        match this.tcx.sess.target.target.target_os.as_str() {
+            "linux" => {
+                // "__cxa_thread_atexit_impl"
+                // This should be all-zero, pointer-sized.
+                let layout = this.layout_of(this.tcx.types.usize)?;
+                let place = this.allocate(layout, MiriMemoryKind::Machine.into());
+                this.write_scalar(Scalar::from_machine_usize(0, &*this.tcx), place.into())?;
+                this.memory
+                    .extra
+                    .extern_statics
+                    .insert("__cxa_thread_atexit_impl", place.ptr.assert_ptr().alloc_id)
+                    .unwrap_none();
+            }
+            _ => {} // No "extern statics" supported on this platform
+        }
+        Ok(())
     }
 }
 
@@ -267,32 +298,29 @@ impl<'mir, 'tcx> Machine<'mir, 'tcx> for Evaluator<'tcx> {
         Ok(())
     }
 
-    fn find_foreign_static(
-        tcx: TyCtxt<'tcx>,
-        def_id: DefId,
-    ) -> InterpResult<'tcx, Cow<'tcx, Allocation>> {
+    fn canonical_alloc_id(mem: &Memory<'mir, 'tcx, Self>, id: AllocId) -> AllocId {
+        let tcx = mem.tcx;
+        // Figure out if this is an extern static, and if yes, which one.
+        let def_id = match tcx.alloc_map.lock().get(id) {
+            Some(GlobalAlloc::Static(def_id)) if tcx.is_foreign_item(def_id) => def_id,
+            _ => {
+                // No need to canonicalize anything.
+                return id;
+            }
+        };
         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(),
             None => tcx.item_name(def_id).as_str(),
         };
-
-        let alloc = match &*link_name {
-            "__cxa_thread_atexit_impl" => {
-                // 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)
-            }
-            _ => throw_unsup_format!("can't access foreign static: {}", link_name),
-        };
-        Ok(Cow::Owned(alloc))
-    }
-
-    #[inline(always)]
-    fn before_terminator(_ecx: &mut InterpCx<'mir, 'tcx, Self>) -> InterpResult<'tcx> {
-        // We are not interested in detecting loops.
-        Ok(())
+        // Check if we know this one.
+        if let Some(canonical_id) = mem.extra.extern_statics.get(&*link_name) {
+            trace!("canonical_alloc_id: {:?} ({}) -> {:?}", id, link_name, canonical_id);
+            *canonical_id
+        } else {
+            // Return original id; `Memory::get_static_alloc` will throw an error.
+            id
+        }
     }
 
     fn init_allocation_extra<'b>(
@@ -433,7 +461,7 @@ impl MayLeak for MiriMemoryKind {
         use self::MiriMemoryKind::*;
         match self {
             Rust | C | WinHeap => false,
-            Env | Static => true,
+            Machine | Static => true,
         }
     }
 }
diff --git a/src/shims/env.rs b/src/shims/env.rs
index 3fd895576e..10f7492165 100644
--- a/src/shims/env.rs
+++ b/src/shims/env.rs
@@ -40,7 +40,7 @@ fn alloc_env_var_as_c_str<'mir, 'tcx>(
     let mut name_osstring = name.to_os_string();
     name_osstring.push("=");
     name_osstring.push(value);
-    ecx.alloc_os_str_as_c_str(name_osstring.as_os_str(), MiriMemoryKind::Env.into())
+    ecx.alloc_os_str_as_c_str(name_osstring.as_os_str(), MiriMemoryKind::Machine.into())
 }
 
 impl<'mir, 'tcx> EvalContextExt<'mir, 'tcx> for crate::MiriEvalContext<'mir, 'tcx> {}
@@ -80,7 +80,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
             let var_ptr = alloc_env_var_as_c_str(&name, &value, &mut this);
             if let Some(var) = this.machine.env_vars.map.insert(name.to_owned(), var_ptr) {
                 this.memory
-                    .deallocate(var, None, MiriMemoryKind::Env.into())?;
+                    .deallocate(var, None, MiriMemoryKind::Machine.into())?;
             }
             Ok(0)
         } else {
@@ -102,7 +102,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         if let Some(old) = success {
             if let Some(var) = old {
                 this.memory
-                    .deallocate(var, None, MiriMemoryKind::Env.into())?;
+                    .deallocate(var, None, MiriMemoryKind::Machine.into())?;
             }
             Ok(0)
         } else {
diff --git a/src/shims/panic.rs b/src/shims/panic.rs
index e930af7f46..11c5a882be 100644
--- a/src/shims/panic.rs
+++ b/src/shims/panic.rs
@@ -187,7 +187,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
 
                 // First arg: Message.
                 let msg = msg.description();
-                let msg = this.allocate_str(msg, MiriMemoryKind::Env.into());
+                let msg = this.allocate_str(msg, MiriMemoryKind::Machine.into());
 
                 // Call the lang item.
                 let panic = this.tcx.lang_items().panic_fn().unwrap();
diff --git a/src/stacked_borrows.rs b/src/stacked_borrows.rs
index a51f8c4571..9a511aaed5 100644
--- a/src/stacked_borrows.rs
+++ b/src/stacked_borrows.rs
@@ -453,7 +453,7 @@ impl Stacks {
             // Thus we call `static_base_ptr` such that the global pointers get the same tag
             // as what we use here.
             // The base pointer is not unique, so the base permission is `SharedReadWrite`.
-            MemoryKind::Machine(MiriMemoryKind::Static) =>
+            MemoryKind::Machine(MiriMemoryKind::Static) | MemoryKind::Machine(MiriMemoryKind::Machine) =>
                 (extra.borrow_mut().static_base_ptr(id), Permission::SharedReadWrite),
             // Everything else we handle entirely untagged for now.
             // FIXME: experiment with more precise tracking.