Fix interrupt table lookup for chain-loaded apps (#17)

* Set mtvec based on linker script symbols instead of hard coding.

* add linker script asserts to ensure 1KB VT alignment

* make sure linker assert for v2 is only included when v2 feature flag is
set.

Author: aq1018

qingke-rt/assert-v2-align-highcode.x

@@ -0,0 +1 @@
+ASSERT(_highcode_vma_start % 1024 == 0, "vector table must be 1KB aligned for Qingke V2");

qingke-rt/assert-v2-align-no-highcode.x

@@ -0,0 +1 @@
+ASSERT(_start % 1024 == 0, "vector table must be 1KB aligned for Qingke V2");

qingke-rt/build.rs

@@ -67,10 +67,21 @@ fn main() {
         fs::write(out_dir.join("link.x"), include_bytes!("link-no-highcode.x")).unwrap();
     }
 
+    // V2 requires the vector table to be 1KB-aligned
+    let has_v2 = env::var("CARGO_FEATURE_V2").is_ok();
+    let asserts: &[u8] = match (has_v2, has_highcode_feature) {
+        (true, true) => include_bytes!("assert-v2-align-highcode.x"),
+        (true, false) => include_bytes!("assert-v2-align-no-highcode.x"),
+        _ => b"",
+    };
+    fs::write(out_dir.join("assert-align.x"), asserts).unwrap();
+
     println!("cargo:rustc-link-search={}", out_dir.display());
 
     println!("cargo:rerun-if-changed=link-highcode.x");
     println!("cargo:rerun-if-changed=link-no-highcode.x");
+    println!("cargo:rerun-if-changed=assert-v2-align-highcode.x");
+    println!("cargo:rerun-if-changed=assert-v2-align-no-highcode.x");
     println!("cargo:rerun-if-changed=build.rs");
 
     let target = env::var("TARGET").unwrap();

qingke-rt/link-highcode.x

@@ -49,12 +49,12 @@ SECTIONS
         . = ALIGN(4);
     } >FLASH AT>FLASH
 
-    /* highcode section will be copied to RAM offset 0x0 */
+    /* highcode section will be copied to RAM */
     .highcode : ALIGN(4)
     {
         _highcode_lma = LOADADDR(.highcode);
         PROVIDE(_highcode_vma_start = .);
-        LONG(0x00000000); /* Placeholder for the first vector */
+        LONG(_start); /* Placeholder for the first vector */
         KEEP(*(.vector_table.core_interrupts));
         KEEP(*(.vector_table.external_interrupts));
         KEEP(*(.vector_table.exceptions));
@@ -118,3 +118,5 @@ SECTIONS
     .eh_frame (INFO) : { KEEP(*(.eh_frame)) }
     .eh_frame_hdr (INFO) : { *(.eh_frame_hdr) }
 }
+
+INCLUDE assert-align.x

qingke-rt/link-no-highcode.x

@@ -103,3 +103,5 @@ SECTIONS
     .eh_frame (INFO) : { KEEP(*(.eh_frame)) }
     .eh_frame_hdr (INFO) : { *(.eh_frame_hdr) }
 }
+
+INCLUDE assert-align.x

qingke-rt/src/lib.rs

@@ -209,10 +209,22 @@ unsafe extern "C" fn qingke_setup_interrupts() {
     #[cfg(not(feature = "v3a"))]
     unsafe {
         #[cfg(feature = "highcode")]
-        mtvec::write(0x20000000, TrapMode::VectoredAddress);
-
+        {
+            unsafe extern "C" {
+                static _highcode_vma_start: u8;
+            }
+            mtvec::write(
+                &raw const _highcode_vma_start as usize,
+                TrapMode::VectoredAddress,
+            );
+        }
         #[cfg(not(feature = "highcode"))]
-        mtvec::write(0x00000000, TrapMode::VectoredAddress);
+        {
+            unsafe extern "C" {
+                static _start: u8;
+            }
+            mtvec::write(&raw const _start as usize, TrapMode::VectoredAddress);
+        }
     }
 
     unsafe {