cheri: add cheri feature, cheri_address_get and cheri_without_provenance intrinsics

Author: xdoardo

compiler/rustc_const_eval/src/const_eval/machine.rs

@@ -466,6 +466,11 @@ impl<'tcx> interpret::Machine<'tcx> for CompileTimeMachine<'tcx> {
             // not the optimization stage.)
             sym::is_val_statically_known => ecx.write_scalar(Scalar::from_bool(false), dest)?,
 
+            sym::cheri_without_provenance => {
+                let addr = ecx.read_scalar(&args[0])?.to_target_usize(ecx)?;
+                ecx.write_pointer(Pointer::without_provenance(addr), dest)?
+            }
+
             // We handle these here since Miri does not want to have them.
             sym::assert_inhabited
             | sym::assert_zero_valid

compiler/rustc_hir_analysis/src/check/intrinsic.rs

@@ -135,7 +135,9 @@ fn intrinsic_operation_unsafety(tcx: TyCtxt<'_>, intrinsic_id: LocalDefId) -> hi
         | sym::round_ties_even_f32
         | sym::round_ties_even_f64
         | sym::round_ties_even_f128
-        | sym::const_eval_select => hir::Safety::Safe,
+        | sym::const_eval_select
+        | sym::cheri_address_get
+        | sym::cheri_without_provenance => hir::Safety::Safe,
         _ => hir::Safety::Unsafe,
     };
 
@@ -664,6 +666,13 @@ pub(crate) fn check_intrinsic_type(
         | sym::atomic_umin => (1, 1, vec![Ty::new_mut_ptr(tcx, param(0)), param(0)], param(0)),
         sym::atomic_fence | sym::atomic_singlethreadfence => (0, 1, Vec::new(), tcx.types.unit),
 
+        // CHERI-specific intrinsics
+        sym::cheri_without_provenance => {
+            (1, 0, vec![tcx.types.usize], Ty::new_mut_ptr(tcx, param(0)))
+        }
+        sym::cheri_address_get => {
+            (0, 0, vec![Ty::new_imm_ptr(tcx, tcx.types.unit)], tcx.types.usize)
+        }
         other => {
             tcx.dcx().emit_err(UnrecognizedIntrinsicFunction { span, name: other });
             return;

compiler/rustc_span/src/symbol.rs

@@ -641,6 +641,9 @@ symbols! {
         char,
         char_is_ascii,
         char_to_digit,
+        cheri,
+        cheri_address_get,
+        cheri_without_provenance,
         child_id,
         child_kill,
         client,

library/core/src/intrinsics/cheri.rs

@@ -0,0 +1,14 @@
+//! Some intrinsics specific to CHERI systems.
+
+/// Create an pointer without provenance metadata from the given value.
+#[inline]
+#[rustc_intrinsic]
+#[rustc_nounwind]
+#[rustc_intrinsic_const_stable_indirect]
+pub const fn cheri_without_provenance<T>(value: usize) -> *mut T;
+
+/// Retrieve the address of the pointer.
+#[inline]
+#[rustc_intrinsic]
+#[rustc_nounwind]
+pub fn cheri_address_get(ptr: *const ()) -> usize;

library/core/src/intrinsics/mod.rs

@@ -63,6 +63,9 @@ pub mod fallback;
 pub mod mir;
 pub mod simd;
 
+#[cfg(target_family = "cheri")]
+pub mod cheri;
+
 // These imports are used for simplifying intra-doc links
 #[allow(unused_imports)]
 #[cfg(all(target_has_atomic = "8", target_has_atomic = "32", target_has_atomic = "ptr"))]

library/core/src/ptr/const_ptr.rs

@@ -1,7 +1,7 @@
 use super::*;
 use crate::cmp::Ordering::{Equal, Greater, Less};
 use crate::intrinsics::const_eval_select;
-use crate::mem::{self, SizedTypeProperties};
+use crate::mem::SizedTypeProperties;
 use crate::slice::{self, SliceIndex};
 
 impl<T: PointeeSized> *const T {
@@ -172,12 +172,21 @@ impl<T: PointeeSized> *const T {
     #[inline(always)]
     #[stable(feature = "strict_provenance", since = "1.84.0")]
     pub fn addr(self) -> usize {
-        // A pointer-to-integer transmute currently has exactly the right semantics: it returns the
-        // address without exposing the provenance. Note that this is *not* a stable guarantee about
-        // transmute semantics, it relies on sysroot crates having special status.
-        // SAFETY: Pointer-to-integer transmutes are valid (if you are okay with losing the
-        // provenance).
-        unsafe { mem::transmute(self.cast::<()>()) }
+
+            #[cfg(target_family = "cheri")]
+            {
+                crate::intrinsics::cheri::cheri_address_get(self.cast::<()>())
+            }
+
+            #[cfg(not(target_family = "cheri"))]
+            {
+                // A pointer-to-integer transmute currently has exactly the right semantics: it returns the
+                // address without exposing the provenance. Note that this is *not* a stable guarantee about
+                // transmute semantics, it relies on sysroot crates having special status.
+                // SAFETY: Pointer-to-integer transmutes are valid (if you are okay with losing the
+                // provenance).
+                unsafe { crate::mem::transmute(self.cast::<()>()) }
+            }
     }
 
     /// Exposes the ["provenance"][crate::ptr#provenance] part of the pointer for future use in

library/core/src/ptr/mod.rs

@@ -915,12 +915,20 @@ pub const fn dangling<T>() -> *const T {
 #[stable(feature = "strict_provenance", since = "1.84.0")]
 #[rustc_const_stable(feature = "strict_provenance", since = "1.84.0")]
 pub const fn without_provenance_mut<T>(addr: usize) -> *mut T {
-    // An int-to-pointer transmute currently has exactly the intended semantics: it creates a
-    // pointer without provenance. Note that this is *not* a stable guarantee about transmute
-    // semantics, it relies on sysroot crates having special status.
-    // SAFETY: every valid integer is also a valid pointer (as long as you don't dereference that
-    // pointer).
-    unsafe { mem::transmute(addr) }
+    #[cfg(target_family = "cheri")]
+    {
+        crate::intrinsics::cheri::cheri_without_provenance(addr)
+    }
+
+    #[cfg(not(target_family = "cheri"))]
+    {
+        // An int-to-pointer transmute currently has exactly the intended semantics: it creates a
+        // pointer without provenance. Note that this is *not* a stable guarantee about transmute
+        // semantics, it relies on sysroot crates having special status.
+        // SAFETY: every valid integer is also a valid pointer (as long as you don't dereference that
+        // pointer).
+        unsafe { mem::transmute(addr) }
+    }
 }
 
 /// Creates a new pointer that is dangling, but non-null and well-aligned.

library/core/src/ptr/mut_ptr.rs

@@ -2,7 +2,7 @@ use super::*;
 use crate::cmp::Ordering::{Equal, Greater, Less};
 use crate::intrinsics::const_eval_select;
 use crate::marker::PointeeSized;
-use crate::mem::{self, SizedTypeProperties};
+use crate::mem::SizedTypeProperties;
 use crate::slice::{self, SliceIndex};
 
 impl<T: PointeeSized> *mut T {
@@ -160,12 +160,20 @@ impl<T: PointeeSized> *mut T {
     #[inline(always)]
     #[stable(feature = "strict_provenance", since = "1.84.0")]
     pub fn addr(self) -> usize {
-        // A pointer-to-integer transmute currently has exactly the right semantics: it returns the
-        // address without exposing the provenance. Note that this is *not* a stable guarantee about
-        // transmute semantics, it relies on sysroot crates having special status.
-        // SAFETY: Pointer-to-integer transmutes are valid (if you are okay with losing the
-        // provenance).
-        unsafe { mem::transmute(self.cast::<()>()) }
+        #[cfg(target_family = "cheri")]
+        {
+            crate::intrinsics::cheri::cheri_address_get(self.cast::<()>())
+        }
+
+        #[cfg(not(target_family = "cheri"))]
+        {
+            // A pointer-to-integer transmute currently has exactly the right semantics: it returns the
+            // address without exposing the provenance. Note that this is *not* a stable guarantee about
+            // transmute semantics, it relies on sysroot crates having special status.
+            // SAFETY: Pointer-to-integer transmutes are valid (if you are okay with losing the
+            // provenance).
+            unsafe { crate::mem::transmute(self.cast::<()>()) }
+        }
     }
 
     /// Exposes the ["provenance"][crate::ptr#provenance] part of the pointer for future use in

src/tools/tidy/src/pal.rs

@@ -44,6 +44,10 @@ const EXCEPTION_PATHS: &[&str] = &[
     "library/unwind",
     "library/rtstartup", // Not sure what to do about this. magic stuff for mingw
     "library/test",      // Probably should defer to unstable `std::sys` APIs.
+    // With the addition of CHERI-like platforms, some CHERI-specific intrinsics must be added.
+    "library/core/src/intrinsics/mod.rs",
+    // With the addition of CHERI-specific intrinsics for CHERI-like platforms, `ptr` too must have platform specific code (to use those intrinsics).
+    "library/core/src/ptr",
     // The `VaList` implementation must have platform specific code.
     // The Windows implementation of a `va_list` is always a character
     // pointer regardless of the target architecture. As a result,