alloc: support initializing from linker information

experiments/src/main.rs

@@ -77,7 +77,7 @@ pub fn main_core0() {
     let mut ddr = zynq::ddr::DdrRam::new();
     #[cfg(not(feature = "target_zc706"))]
     ddr.memtest();
-    ram::init_alloc(&mut ddr);
+    ram::init_alloc_ddr(&mut ddr);
 
     for i in 0..=1 {
         let mut flash_io = flash.manual_mode(i);

libsupport_zynq/src/ram.rs

@@ -27,13 +27,27 @@ unsafe impl GlobalAlloc for CortexA9Alloc {
     }
 }
 
-pub fn init_alloc(ddr: &mut DdrRam) {
+pub fn init_alloc_ddr(ddr: &mut DdrRam) {
     unsafe {
         ALLOCATOR.0.lock()
             .init(ddr.ptr::<u8>() as usize, ddr.size());
     }
 }
 
+extern "C" {
+    static __heap_start: usize;
+    static __heap_end: usize;
+}
+
+pub fn init_alloc_linker() {
+    unsafe {
+        let start = &__heap_start as *const usize as usize;
+        let end = &__heap_end as *const usize as usize;
+        ALLOCATOR.0.lock()
+            .init(start, end - start);
+    }
+}
+
 
 #[alloc_error_handler]
 fn alloc_error(_: core::alloc::Layout) -> ! {