remove #[cmse_nonsecure_entry]

Author: folkertdev

compiler/rustc_codegen_llvm/src/attributes.rs

@@ -441,9 +441,6 @@ pub fn from_fn_attrs<'ll, 'tcx>(
         let allocated_pointer = AttributeKind::AllocatedPointer.create_attr(cx.llcx);
         attributes::apply_to_llfn(llfn, AttributePlace::Argument(0), &[allocated_pointer]);
     }
-    if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::CMSE_NONSECURE_ENTRY) {
-        to_add.push(llvm::CreateAttrString(cx.llcx, "cmse_nonsecure_entry"));
-    }
     if let Some(align) = codegen_fn_attrs.alignment {
         llvm::set_alignment(llfn, align);
     }

compiler/rustc_codegen_ssa/src/codegen_attrs.rs

@@ -192,24 +192,6 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
                     }
                 }
             }
-            sym::cmse_nonsecure_entry => {
-                if let Some(fn_sig) = fn_sig()
-                    && !matches!(fn_sig.skip_binder().abi(), abi::Abi::C { .. })
-                {
-                    struct_span_code_err!(
-                        tcx.dcx(),
-                        attr.span,
-                        E0776,
-                        "`#[cmse_nonsecure_entry]` requires C ABI"
-                    )
-                    .emit();
-                }
-                if !tcx.sess.target.llvm_target.contains("thumbv8m") {
-                    struct_span_code_err!(tcx.dcx(), attr.span, E0775, "`#[cmse_nonsecure_entry]` is only valid for targets with the TrustZone-M extension")
-                    .emit();
-                }
-                codegen_fn_attrs.flags |= CodegenFnAttrFlags::CMSE_NONSECURE_ENTRY
-            }
             sym::thread_local => codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL,
             sym::track_caller => {
                 let is_closure = tcx.is_closure_like(did.to_def_id());

compiler/rustc_error_codes/src/error_codes/E0776.md

@@ -1,3 +1,5 @@
+#### Note: this error code is no longer emitted by the compiler.
+
 `#[cmse_nonsecure_entry]` functions require a C ABI
 
 Erroneous code example:

compiler/rustc_error_codes/src/lib.rs

@@ -678,3 +678,4 @@ E0798: 0798,
 //  E0723, // unstable feature in `const` context
 //  E0738, // Removed; errored on `#[track_caller] fn`s in `extern "Rust" { ... }`.
 //  E0744, // merged into E0728
+//  E0776, // Removed; cmse_nonsecure_entry is now `C-cmse-nonsecure-entry`

compiler/rustc_feature/src/builtin_attrs.rs

@@ -550,10 +550,6 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
         EncodeCrossCrate::No, experimental!(register_tool),
     ),
 
-    gated!(
-        cmse_nonsecure_entry, Normal, template!(Word), WarnFollowing,
-        EncodeCrossCrate::No, experimental!(cmse_nonsecure_entry)
-    ),
     // RFC 2632
     gated!(
         const_trait, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No, const_trait_impl,

compiler/rustc_feature/src/unstable.rs

@@ -391,7 +391,7 @@ declare_features! (
     (unstable, closure_lifetime_binder, "1.64.0", Some(97362)),
     /// Allows `#[track_caller]` on closures and coroutines.
     (unstable, closure_track_caller, "1.57.0", Some(87417)),
-    /// Allows to use the `#[cmse_nonsecure_entry]` attribute.
+    /// Allows `extern "C-cmse-nonsecure-entry" fn()`.
     (unstable, cmse_nonsecure_entry, "1.48.0", Some(75835)),
     /// Allows `async {}` expressions in const contexts.
     (unstable, const_async_blocks, "1.53.0", Some(85368)),

compiler/rustc_middle/src/middle/codegen_fn_attrs.rs

@@ -110,9 +110,7 @@ bitflags::bitflags! {
         /// #[ffi_const]: applies clang's `const` attribute to a foreign function
         /// declaration.
         const FFI_CONST                 = 1 << 12;
-        /// #[cmse_nonsecure_entry]: with a TrustZone-M extension, declare a
-        /// function as an entry function from Non-Secure code.
-        const CMSE_NONSECURE_ENTRY      = 1 << 13;
+        // (Bit 13 was used for `#[cmse_nonsecure_entry]`, but is now unused.)
         // (Bit 14 was used for `#[coverage(off)]`, but is now unused.)
         /// `#[used(linker)]`:
         /// indicates that neither LLVM nor the linker will eliminate this function.

compiler/rustc_passes/src/check_attr.rs

@@ -180,9 +180,6 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                 | [sym::rustc_must_implement_one_of]
                 | [sym::rustc_deny_explicit_impl]
                 | [sym::const_trait] => self.check_must_be_applied_to_trait(attr, span, target),
-                [sym::cmse_nonsecure_entry] => {
-                    self.check_cmse_nonsecure_entry(hir_id, attr, span, target)
-                }
                 [sym::collapse_debuginfo] => self.check_collapse_debuginfo(attr, span, target),
                 [sym::must_not_suspend] => self.check_must_not_suspend(attr, span, target),
                 [sym::must_use] => self.check_must_use(hir_id, attr, target),
@@ -433,28 +430,6 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
         }
     }
 
-    /// Checks if `#[cmse_nonsecure_entry]` is applied to a function definition.
-    fn check_cmse_nonsecure_entry(
-        &self,
-        hir_id: HirId,
-        attr: &Attribute,
-        span: Span,
-        target: Target,
-    ) -> bool {
-        match target {
-            Target::Fn
-            | Target::Method(MethodKind::Trait { body: true } | MethodKind::Inherent) => true,
-            _ => {
-                self.dcx().emit_err(errors::AttrShouldBeAppliedToFn {
-                    attr_span: attr.span,
-                    defn_span: span,
-                    on_crate: hir_id == CRATE_HIR_ID,
-                });
-                false
-            }
-        }
-    }
-
     /// Debugging aid for `object_lifetime_default` query.
     fn check_object_lifetime_default(&self, hir_id: HirId) {
         let tcx = self.tcx;

compiler/rustc_target/src/spec/mod.rs

@@ -1251,9 +1251,9 @@ impl StackProbeType {
                     .and_then(|o| o.as_array())
                     .ok_or_else(|| "expected `min-llvm-version-for-inline` to be an array")?;
                 let mut iter = min_version.into_iter().map(|v| {
-                    let int = v.as_u64().ok_or_else(|| {
-                        "expected `min-llvm-version-for-inline` values to be integers"
-                    })?;
+                    let int = v.as_u64().ok_or_else(
+                        || "expected `min-llvm-version-for-inline` values to be integers",
+                    )?;
                     u32::try_from(int)
                         .map_err(|_| "`min-llvm-version-for-inline` values don't convert to u32")
                 });

src/doc/unstable-book/src/language-features/cmse-nonsecure-entry.md

@@ -15,10 +15,10 @@ LLVM, the Rust compiler and the linker are providing
 TrustZone-M feature.
 
 One of the things provided, with this unstable feature, is the
-`cmse_nonsecure_entry` attribute.  This attribute marks a Secure function as an
+`C-cmse-nonsecure-entry` ABI. This ABI marks a Secure function as an
 entry function (see [section
 5.4](https://developer.arm.com/documentation/ecm0359818/latest/) for details).
-With this attribute, the compiler will do the following:
+With this ABI, the compiler will do the following:
 * add a special symbol on the function which is the `__acle_se_` prefix and the
   standard function name
 * constrain the number of parameters to avoid using the Non-Secure stack
@@ -38,11 +38,11 @@ gateway veneer.
 <!-- NOTE(ignore) this example is specific to thumbv8m targets -->
 
 ``` rust,ignore
+#![no_std]
 #![feature(cmse_nonsecure_entry)]
 
 #[no_mangle]
-#[cmse_nonsecure_entry]
-pub extern "C" fn entry_function(input: u32) -> u32 {
+pub extern "C-cmse-nonsecure-entry" fn entry_function(input: u32) -> u32 {
     input + 6
 }
 ```