feat: configurable link section attribute for irqs

This change introduces a new config field that allows `svd2rust`
to target which linker sections get assigned to the `__INTERRUPTS`
static, with reasonable defaults.

Previously on RISC-V, the choice was always left up to the compiler, and
it seemed to always pick `.rodata`. Unfortunately, in my context, that
meant placing the LUT in a memory range that had a lot of highly
variable latency, which cost not just time but predictability in
servicing interrupts.

With this change in place, I'm able to target a particular section
(e.g. `.data`, or `.trap.rodata`) for the placement of the static, which
grants more granular control over the ultimate loaded memory address.

For the full details about the problem, please see: esp-rs/esp-hal@e29f3d5

Author: sethp

src/generate/interrupt.rs

@@ -118,6 +118,14 @@ pub fn render(
                 writeln!(device_x, "PROVIDE({name} = DefaultHandler);")?;
             }
 
+            let link_section_name = config
+                .interrupt_link_section
+                .as_deref()
+                .unwrap_or(".vector_table.interrupts");
+            let link_section_attr = quote! {
+                #[link_section = #link_section_name]
+            };
+
             root.extend(quote! {
                 #[cfg(feature = "rt")]
                 extern "C" {
@@ -132,7 +140,7 @@ pub fn render(
 
                 #[cfg(feature = "rt")]
                 #[doc(hidden)]
-                #[link_section = ".vector_table.interrupts"]
+                #link_section_attr
                 #[no_mangle]
                 pub static __INTERRUPTS: [Vector; #n] = [
                     #elements
@@ -144,6 +152,14 @@ pub fn render(
                 writeln!(device_x, "PROVIDE({name} = DefaultHandler);").unwrap();
             }
 
+            let link_section_name = config
+                .interrupt_link_section
+                .as_deref()
+                .unwrap_or(".vector_table.interrupts");
+            let link_section_attr = quote! {
+                #[link_section = #link_section_name]
+            };
+
             root.extend(quote! {
                 #[cfg(feature = "rt")]
                 extern "msp430-interrupt" {
@@ -158,7 +174,7 @@ pub fn render(
 
                 #[cfg(feature = "rt")]
                 #[doc(hidden)]
-                #[link_section = ".vector_table.interrupts"]
+                #link_section_attr
                 #[no_mangle]
                 #[used]
                 pub static __INTERRUPTS:
@@ -172,6 +188,14 @@ pub fn render(
                 writeln!(device_x, "PROVIDE({name} = DefaultHandler);")?;
             }
 
+            let link_section_attr = if let Some(section) = &config.interrupt_link_section {
+                quote! {
+                    #[link_section = #section]
+                }
+            } else {
+                quote! {}
+            };
+
             root.extend(quote! {
                 #[cfg(feature = "rt")]
                 extern "C" {
@@ -186,6 +210,7 @@ pub fn render(
 
                 #[cfg(feature = "rt")]
                 #[doc(hidden)]
+                #link_section_attr
                 #[no_mangle]
                 pub static __EXTERNAL_INTERRUPTS: [Vector; #n] = [
                     #elements
@@ -197,6 +222,14 @@ pub fn render(
                 writeln!(device_x, "PROVIDE({name} = DefaultHandler);")?;
             }
 
+            let link_section_attr = if let Some(section) = &config.interrupt_link_section {
+                quote! {
+                    #[link_section = #section]
+                }
+            } else {
+                quote! {}
+            };
+
             root.extend(quote! {
                 #[cfg(feature = "rt")]
                 extern "C" {
@@ -210,6 +243,7 @@ pub fn render(
                 }
 
                 #[cfg(feature = "rt")]
+                #link_section_attr
                 #[doc(hidden)]
                 pub static __INTERRUPTS: [Vector; #n] = [
                     #elements

src/util.rs

@@ -59,6 +59,8 @@ pub struct Config {
     pub source_type: SourceType,
     #[cfg_attr(feature = "serde", serde(default))]
     pub log_level: Option<String>,
+    #[cfg_attr(feature = "serde", serde(default))]
+    pub interrupt_link_section: Option<String>,
 }
 
 #[derive(Clone, Debug, PartialEq, Eq)]
@@ -120,6 +122,7 @@ impl Default for Config {
             input: None,
             source_type: SourceType::default(),
             log_level: None,
+            interrupt_link_section: None,
         }
     }
 }