cortex-m-rt: Fix max_int_handlers on armv8m

Fixed interrupt count for Cortex-M23 (ARMv8-M Baseline, 240) and Cortex-M33 (ARMv8-M Mainline, 480) based on the technical reference manual. The original value of 496 referred to the entire vector table length, with exceptions length already included in the assert check.

Author: decaday

cortex-m-rt/build.rs

@@ -68,12 +68,12 @@ INCLUDE device.x"#
         println!("cargo:rustc-cfg=cortex_m");
         println!("cargo:rustc-cfg=armv8m");
         println!("cargo:rustc-cfg=armv8m_base");
-        496
+        240
     } else if target.starts_with("thumbv8m.main") {
         println!("cargo:rustc-cfg=cortex_m");
         println!("cargo:rustc-cfg=armv8m");
         println!("cargo:rustc-cfg=armv8m_main");
-        496
+        480
     } else {
         // Non ARM target. We assume you're just testing the syntax.
         // This value seems as good as any.

cortex-m-rt/src/lib.rs

@@ -1259,7 +1259,7 @@ pub static __EXCEPTIONS: [Vector; 14] = [
 
 // If we are not targeting a specific device we bind all the potential device specific interrupts
 // to the default handler
-#[cfg(all(any(not(feature = "device"), test), not(armv6m), not(armv8m)))]
+#[cfg(all(any(not(feature = "device"), test), not(armv6m), not(armv8m_main)))]
 #[doc(hidden)]
 #[cfg_attr(cortex_m, link_section = ".vector_table.interrupts")]
 #[no_mangle]
@@ -1272,11 +1272,11 @@ pub static __INTERRUPTS: [unsafe extern "C" fn(); 240] = [{
 }; 240];
 
 // ARMv8-M can have up to 496 device specific interrupts
-#[cfg(all(not(feature = "device"), armv8m))]
+#[cfg(all(not(feature = "device"), armv8m_main))]
 #[doc(hidden)]
 #[cfg_attr(cortex_m, link_section = ".vector_table.interrupts")]
 #[no_mangle]
-pub static __INTERRUPTS: [unsafe extern "C" fn(); 496] = [{
+pub static __INTERRUPTS: [unsafe extern "C" fn(); 480] = [{
     extern "C" {
         fn DefaultHandler();
     }