Add more tests and check for ABI

Signed-off-by: Hugues de Valon <hugues.devalon@arm.com>

compiler/rustc_error_codes/src/error_codes.rs

@@ -459,6 +459,7 @@
 E0773: include_str!("./error_codes/E0773.md"),
 E0774: include_str!("./error_codes/E0774.md"),
 E0775: include_str!("./error_codes/E0775.md"),
+E0776: include_str!("./error_codes/E0776.md"),
 ;
 //  E0006, // merged with E0005
 //  E0008, // cannot bind by-move into a pattern guard

compiler/rustc_error_codes/src/error_codes/E0775.md

@@ -7,7 +7,7 @@ Erroneous code example:
 #![feature(cmse_nonsecure_entry)]
 
 #[cmse_nonsecure_entry]
-fn toto() {}
+pub extern "C" fn entry_function() {}
 ```
 
 To fix this error, compile your code for a Rust target that supports the

compiler/rustc_error_codes/src/error_codes/E0776.md

@@ -0,0 +1,13 @@
+`#[cmse_nonsecure_entry]` functions require a C ABI
+
+Erroneous code example:
+
+```compile_fail,E0776
+#![feature(cmse_nonsecure_entry)]
+
+#[no_mangle]
+#[cmse_nonsecure_entry]
+pub fn entry_function(input: Vec<u32>) {}
+```
+
+To fix this error, declare your entry function with a C ABI, using `extern "C"`.

compiler/rustc_typeck/src/collect.rs

@@ -2544,6 +2544,15 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
         } else if tcx.sess.check_name(attr, sym::used) {
             codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
         } else if tcx.sess.check_name(attr, sym::cmse_nonsecure_entry) {
+            if tcx.fn_sig(id).abi() != abi::Abi::C {
+                struct_span_err!(
+                    tcx.sess,
+                    attr.span,
+                    E0776,
+                    "`#[cmse_nonsecure_entry]` requires C ABI"
+                )
+                .emit();
+            }
             if !tcx.sess.target.target.llvm_target.contains("thumbv8m") {
                 struct_span_err!(tcx.sess, attr.span, E0775, "`#[cmse_nonsecure_entry]` is only valid for targets with the TrustZone-M extension")
                     .emit();

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

@@ -26,6 +26,12 @@ With this attribute, the compiler will do the following:
   information
 * use the `BXNS` instruction to return
 
+Because the stack can not be used to pass parameters, there will be compilation
+errors if:
+* the total size of all parameters is too big (for example more than four 32
+  bits integers)
+* the entry function is not using a C ABI
+
 The special symbol `__acle_se_` will be used by the linker to generate a secure
 gateway veneer.
 

src/test/ui/cmse-nonsecure-entry/gate_test.rs

@@ -0,0 +1,11 @@
+// gate-test-cmse_nonsecure_entry
+
+#[no_mangle]
+#[cmse_nonsecure_entry]
+//~^ ERROR [E0775]
+//~| ERROR [E0658]
+pub extern "C" fn entry_function(input: u32) -> u32 {
+    input + 6
+}
+
+fn main() {}

src/test/ui/cmse-nonsecure-entry/gate_test.stderr

@@ -0,0 +1,19 @@
+error[E0658]: the `#[cmse_nonsecure_entry]` attribute is an experimental feature
+  --> $DIR/gate_test.rs:4:1
+   |
+LL | #[cmse_nonsecure_entry]
+   | ^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #75835 <https://github.com/rust-lang/rust/issues/75835> for more information
+   = help: add `#![feature(cmse_nonsecure_entry)]` to the crate attributes to enable
+
+error[E0775]: `#[cmse_nonsecure_entry]` is only valid for targets with the TrustZone-M extension
+  --> $DIR/gate_test.rs:4:1
+   |
+LL | #[cmse_nonsecure_entry]
+   | ^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0658, E0775.
+For more information about an error, try `rustc --explain E0658`.

src/test/ui/cmse-nonsecure-entry/params-on-registers.rs

@@ -0,0 +1,11 @@
+// build-pass
+// compile-flags: --target thumbv8m.main-none-eabi --crate-type lib
+// only-thumbv8m.main-none-eabi
+#![feature(cmse_nonsecure_entry)]
+#![no_std]
+
+#[no_mangle]
+#[cmse_nonsecure_entry]
+pub extern "C" fn entry_function(a: u32, b: u32, c: u32, d: u32) -> u32 {
+    a + b + c + d
+}

src/test/ui/cmse-nonsecure-entry/params-on-stack.rs

@@ -1,4 +1,3 @@
-// gate-test-cmse_nonsecure_entry
 // compile-flags: --target thumbv8m.main-none-eabi --crate-type lib
 // only-thumbv8m.main-none-eabi
 #![feature(cmse_nonsecure_entry)]
@@ -6,6 +5,6 @@
 
 #[no_mangle]
 #[cmse_nonsecure_entry]
-pub extern "C" fn entry_function(a: u32, b: u32, c: u32, d: u32, e: u32) -> u32 {
+pub extern "C" fn entry_function(a: u32, b: u32, c: u32, d: u32, e: u32) -> u32 { //~ ERROR
     a + b + c + d + e
 }

src/test/ui/cmse-nonsecure-entry/trustzone-only.rs

@@ -1,4 +1,3 @@
-// gate-test-cmse_nonsecure_entry
 // ignore-thumbv8m.main-none-eabi
 #![feature(cmse_nonsecure_entry)]
 

src/test/ui/cmse-nonsecure-entry/trustzone-only.stderr

@@ -1,5 +1,5 @@
 error[E0775]: `#[cmse_nonsecure_entry]` is only valid for targets with the TrustZone-M extension
-  --> $DIR/trustzone-only.rs:6:1
+  --> $DIR/trustzone-only.rs:5:1
    |
 LL | #[cmse_nonsecure_entry]
    | ^^^^^^^^^^^^^^^^^^^^^^^

src/test/ui/cmse-nonsecure-entry/wrong-abi.rs

@@ -0,0 +1,10 @@
+// compile-flags: --target thumbv8m.main-none-eabi --crate-type lib
+// only-thumbv8m.main-none-eabi
+#![feature(cmse_nonsecure_entry)]
+#![no_std]
+
+#[no_mangle]
+#[cmse_nonsecure_entry]
+pub fn entry_function(a: u32, b: u32, c: u32, d: u32) -> u32 { //~ ERROR [E0776]
+    a + b + c + d
+}

src/test/ui/cmse-nonsecure-entry/wrong-abi.stderr

@@ -0,0 +1,9 @@
+error[E0776]: `#[cmse_nonsecure_entry]` functions require C ABI
+  --> $DIR/wrong-abi.rs:7:1
+   |
+LL | #[cmse_nonsecure_entry]
+   | ^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0776`.