Create an init system.

5 files changed, 82 insertions, 49 deletions

diff --git a/linker_script.ld b/linker_script.ld
index 37b90a4..8ae98d0 100644
--- a/linker_script.ld
+++ b/linker_script.ld
@@ -18,8 +18,16 @@ SECTIONS
     . = ORIGIN(flash) + 0x0dc;
   } >flash
 
+  /** Init routines */
+  _sinits = ADDR(.vectors) + SIZEOF(.vectors);
+  .inits _sinits : ALIGN(0x04) {
+    KEEP(*(SORT_BY_NAME(.inits .inits.*)));
+    _einits = .;
+    . = ALIGN(0x04);
+  } > flash
+
   /** Text data is stored after the vector table. */
-  PROVIDE(_stext = ADDR(.vectors) + SIZEOF(.vectors));
+  PROVIDE(_stext = ADDR(.inits) + SIZEOF(.inits));
   .text _stext : ALIGN(0x04) {
     *(.text .text.*);
     . = ALIGN(0x04);
diff --git a/src/init/core.rs b/src/init/core.rs
new file mode 100644
index 0000000..51f1e6a
--- /dev/null
+++ b/src/init/core.rs
@@ -0,0 +1,29 @@
+#[link_section = ".on_reset"]
+#[no_mangle]
+pub static __RESET_VECTOR: fn() -> ! = on_reset;
+
+/**
+ * The init sections are run. The order in which they are run is deterined by the name of the
+ * section the pointer to the function is located in. By convention the section name is 'inits.nnn'
+ * where 'nnn' is a number from 000-999.
+ */
+fn run_init_sections() -> () {
+    extern "C" {
+        static mut _sinits: extern "C" fn() -> ();
+        static mut _einits: extern "C" fn() -> ();
+    }
+    unsafe {
+        let mut cursor: *mut extern "C" fn() -> () = &mut _sinits;
+        let einits_end: *mut extern "C" fn() -> () = &mut _einits;
+
+        while cursor < einits_end {
+            cursor.read()();
+            cursor = cursor.offset(1);
+        }
+    }
+}
+
+fn on_reset() -> ! {
+    run_init_sections();
+    loop {}
+}
diff --git a/src/init/load.rs b/src/init/load.rs
new file mode 100644
index 0000000..ce7b681
--- /dev/null
+++ b/src/init/load.rs
@@ -0,0 +1,37 @@
+/** Load into the data segments */
+#[link_section = ".inits.005"]
+#[no_mangle]
+static __LOAD_DATA_SEGMENTS: fn() -> () = data_segments;
+
+/** Loads the .data segment data from flash to memory if required.  */
+fn data_segments() -> () {
+    extern "C" {
+        static mut __data_load: u32;
+        static mut __data_store_start: u32;
+        static mut __data_store_end: u32;
+        static mut __bss_start: u32;
+        static mut __bss_end: u32;
+    }
+
+    unsafe {
+        let mut data_load_addr: *mut u32 = &mut __data_load;
+        let mut store_cursor: *mut u32 = &mut __data_store_start;
+        let data_store_end_addr: *mut u32 = &mut __data_store_end;
+
+        while store_cursor < data_store_end_addr {
+            store_cursor.write_volatile(*data_load_addr);
+            data_load_addr = data_load_addr.offset(1);
+            store_cursor = store_cursor.offset(1);
+        }
+
+        let bss_end: *mut u32 = &mut __bss_end;
+        let mut bss_cursor: *mut u32 = &mut __bss_start;
+
+        while bss_cursor < bss_end {
+            bss_cursor.write_volatile(0);
+            bss_cursor = bss_cursor.offset(1);
+        }
+    }
+
+    return;
+}
diff --git a/src/init/mod.rs b/src/init/mod.rs
new file mode 100644
index 0000000..2e609f3
--- /dev/null
+++ b/src/init/mod.rs
@@ -0,0 +1,2 @@
+pub mod core;
+pub mod load;
diff --git a/src/main.rs b/src/main.rs
index a3e8071..146f601 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -3,56 +3,13 @@
 
 use core::panic::PanicInfo;
 
-#[link_section = ".on_reset"]
-#[no_mangle]
-pub static __RESET_VECTOR: fn() -> ! = on_reset;
+mod init;
 
+#[link_section = ".inits.999"]
 #[no_mangle]
-pub static mut DEADBEEF: u32 = 0xdeadbeef;
-pub static mut OTHER: u32 = 0;
-
-/** Load into the data segments */
-pub fn load_data_segments() -> () {
-    extern "C" {
-        static mut __data_load: u32;
-        static mut __data_store_start: u32;
-        static mut __data_store_end: u32;
-        static mut __bss_start: u32;
-        static mut __bss_end: u32;
-    }
-
-    unsafe {
-        let mut data_load_addr: *mut u32 = &mut __data_load;
-        let mut store_cursor: *mut u32 = &mut __data_store_start;
-        let data_store_end_addr: *mut u32 = &mut __data_store_end;
-
-        while store_cursor < data_store_end_addr {
-            store_cursor.write_volatile(*data_load_addr);
-            data_load_addr = data_load_addr.offset(1);
-            store_cursor = store_cursor.offset(1);
-        }
-
-        let bss_end: *mut u32 = &mut __bss_end;
-        let mut bss_cursor: *mut u32 = &mut __bss_start;
-
-        while bss_cursor < bss_end {
-            bss_cursor.write_volatile(0);
-            bss_cursor = bss_cursor.offset(1);
-        }
-    }
-
-    return;
-}
-
-pub fn on_reset() -> ! {
-    load_data_segments();
-
-    unsafe {
-        DEADBEEF += 100;
-        OTHER = DEADBEEF;
-    }
-
-    loop {}
+pub static __MAIN: fn() -> () = main;
+pub fn main() -> () {
+    loop {};
 }
 
 #[panic_handler]