Add TerminationInfo::Deadlock, use in mutex shim

Author: divergentdave

src/diagnostics.rs

@@ -12,7 +12,8 @@ pub enum TerminationInfo {
     Exit(i64),
     Abort(Option<String>),
     UnsupportedInIsolation(String),
-    ExperimentalUb { msg: String, url: String }
+    ExperimentalUb { msg: String, url: String },
+    Deadlock,
 }
 
 impl fmt::Debug for TerminationInfo {
@@ -29,6 +30,8 @@ impl fmt::Debug for TerminationInfo {
                 write!(f, "{}", msg),
             ExperimentalUb { msg, .. } =>
                 write!(f, "{}", msg),
+            Deadlock =>
+                write!(f, "the evaluated program deadlocked"),
         }
     }
 }
@@ -60,6 +63,7 @@ pub fn report_error<'tcx, 'mir>(
                     "unsupported operation",
                 ExperimentalUb { .. } =>
                     "Undefined Behavior",
+                Deadlock => "deadlock",
             };
             let helps = match info {
                 UnsupportedInIsolation(_) =>

src/shims/sync.rs

@@ -1,7 +1,5 @@
-use std::sync::atomic::{AtomicU64, Ordering};
-
 use rustc_middle::ty::{TyKind, TypeAndMut};
-use rustc_target::abi::{FieldsShape, LayoutOf, Size};
+use rustc_target::abi::{LayoutOf, Size};
 
 use crate::stacked_borrows::Tag;
 use crate::*;
@@ -102,7 +100,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 mutex_set_locked_count(this, mutex_op, Scalar::from_u32(1))?;
                 Ok(0)
             } else {
-                throw_unsup_format!("Deadlock due to locking a PTHREAD_MUTEX_NORMAL mutex twice");
+                throw_machine_stop!(TerminationInfo::Deadlock);
             }
         } else if kind == this.eval_libc("PTHREAD_MUTEX_ERRORCHECK")? {
             if locked_count == 0 {
@@ -404,58 +402,6 @@ fn mutexattr_set_kind<'mir, 'tcx: 'mir>(
 // bytes 12-15 or 16-19 (depending on platform): mutex kind, as an i32
 // (the kind has to be at its offset for compatibility with static initializer macros)
 
-static LIBC_MUTEX_KIND_OFFSET_CACHE: AtomicU64 = AtomicU64::new(0);
-
-fn libc_mutex_kind_offset<'mir, 'tcx: 'mir>(
-    ecx: &mut MiriEvalContext<'mir, 'tcx>,
-) -> InterpResult<'tcx, u64> {
-    // Check if this offset has already been found and memoized
-    let cached_value = LIBC_MUTEX_KIND_OFFSET_CACHE.load(Ordering::Relaxed);
-    if cached_value != 0 {
-        return Ok(cached_value);
-    }
-
-    // This function infers the offset of the `kind` field of libc's pthread_mutex_t
-    // C struct by examining the array inside libc::PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP.
-    // At time of writing, it is always all zero bytes except for a one byte at one of
-    // four positions, depending on the target OS's C struct layout and the endianness of the
-    // target architecture. This offset will then be used in getters and setters below, so that
-    // mutexes created from static initializers can be emulated with the correct behavior.
-    let initializer_path = ["libc", "PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP"];
-    let initializer_instance = ecx.resolve_path(&initializer_path);
-    let initializer_cid = GlobalId { instance: initializer_instance, promoted: None };
-    let initializer_const_val = ecx.const_eval_raw(initializer_cid)?;
-    let array_mplacety = ecx.mplace_field(initializer_const_val, 0)?;
-    let array_length = match array_mplacety.layout.fields {
-        FieldsShape::Array { count, .. } => count,
-        _ => bug!("Couldn't get array length from type {:?}", array_mplacety.layout.ty),
-    };
-
-    let kind_offset = if array_length < 20 {
-        bug!("libc::PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP array was shorter than expected");
-    } else if ecx.read_scalar(ecx.mplace_field(array_mplacety, 16)?.into())?.to_u8()? != 0 {
-        // for little-endian architectures
-        16
-    } else if ecx.read_scalar(ecx.mplace_field(array_mplacety, 19)?.into())?.to_u8()? != 0 {
-        // for big-endian architectures
-        // (note that the i32 spans bytes 16 through 19, so the offset of the kind field is 16)
-        16
-    } else if ecx.read_scalar(ecx.mplace_field(array_mplacety, 12)?.into())?.to_u8()? != 0 {
-        // for little-endian architectures
-        12
-    } else if ecx.read_scalar(ecx.mplace_field(array_mplacety, 15)?.into())?.to_u8()? != 0 {
-        // for big-endian architectures
-        // (note that the i32 spans bytes 12 through 15, so the offset of the kind field is 12)
-        12
-    } else {
-        bug!("Couldn't determine offset of `kind` in pthread_mutex_t");
-    };
-
-    // Save offset to memoization cache for future calls
-    LIBC_MUTEX_KIND_OFFSET_CACHE.store(kind_offset, Ordering::Relaxed);
-    Ok(kind_offset)
-}
-
 fn mutex_get_locked_count<'mir, 'tcx: 'mir>(
     ecx: &MiriEvalContext<'mir, 'tcx>,
     mutex_op: OpTy<'tcx, Tag>,
@@ -491,12 +437,9 @@ fn mutex_get_kind<'mir, 'tcx: 'mir>(
     assert_ptr_target_min_size(ecx, mutex_op, 20)?;
     let mutex_place = ecx.deref_operand(mutex_op)?;
     let i32_layout = ecx.layout_of(ecx.tcx.types.i32)?;
-    let kind_place = mutex_place.offset(
-        Size::from_bytes(libc_mutex_kind_offset(ecx)?),
-        MemPlaceMeta::None,
-        i32_layout,
-        ecx,
-    )?;
+    let kind_offset = if ecx.pointer_size().bytes() == 8 { 16 } else { 12 };
+    let kind_place =
+        mutex_place.offset(Size::from_bytes(kind_offset), MemPlaceMeta::None, i32_layout, ecx)?;
     ecx.read_scalar(kind_place.into())
 }
 
@@ -509,12 +452,9 @@ fn mutex_set_kind<'mir, 'tcx: 'mir>(
     assert_ptr_target_min_size(ecx, mutex_op, 20)?;
     let mutex_place = ecx.deref_operand(mutex_op)?;
     let i32_layout = ecx.layout_of(ecx.tcx.types.i32)?;
-    let kind_place = mutex_place.offset(
-        Size::from_bytes(libc_mutex_kind_offset(ecx)?),
-        MemPlaceMeta::None,
-        i32_layout,
-        ecx,
-    )?;
+    let kind_offset = if ecx.pointer_size().bytes() == 8 { 16 } else { 12 };
+    let kind_place =
+        mutex_place.offset(Size::from_bytes(kind_offset), MemPlaceMeta::None, i32_layout, ecx)?;
     ecx.write_scalar(kind.into(), kind_place.into())
 }