extend linker script

.cargo/config

@@ -2,7 +2,7 @@
 runner = "./runner.sh"
 linker = "arm-none-eabihf-gcc"
 rustflags = [
-  "-C", "link-arg=-Wl,-Tlink.x",
+  "-C", "link-arg=-Wl,-Tlink.x,-N",
   "-C", "target-feature=a9,armv7-a,neon",
   "-C", "target-cpu=cortex-a9",
 ]

link.x

@@ -1,57 +1,49 @@
 ENTRY(_boot_cores);
 
-/* SECTIONS */
-/* { */
-/*     . = 0x8000; */
-
-/*     .text : */
-/*     { */
-/*         KEEP(*(.text.boot)) *(.text .text.*) */
-/*     } */
-
-/*     /DISCARD/ : { *(.comment) *(.gnu*) *(.note*) *(.eh_frame*) } */
-/* } */
+STACK_SIZE = 0x2000 - 0x10;
 
+MEMORY
+{
+  /* 256 kB On-Chip Memory */
+  OCM : ORIGIN = 0, LENGTH = 0x40000
+}
 
 SECTIONS
 {
-    /* Starts at LOADER_ADDR. */
-    . = 0x8000;
-    __start = .;
-    __text_start = .;
     .text :
     {
+        /* Starts at LOADER_ADDR. */
+        . = 0x8000;
         KEEP(*(.text.boot))
-        *(.text)
-    }
-    . = ALIGN(4096); /* align to page size */
-    __text_end = .;
+        *(.text .text.*)
+        . = ALIGN(4096); /* align to page size */
+    } > OCM
  
-    __rodata_start = .;
     .rodata :
     {
         *(.rodata)
-    }
-    . = ALIGN(4096); /* align to page size */
-    __rodata_end = .;
+        . = ALIGN(4096); /* align to page size */
+    } > OCM
  
-    __data_start = .;
     .data :
     {
         *(.data)
-    }
-    . = ALIGN(4096); /* align to page size */
-    __data_end = .;
+        . = ALIGN(4096); /* align to page size */
+    } > OCM
  
-    __bss_start = .;
-    .bss :
+    .bss (NOLOAD) :
     {
-        bss = .;
         *(.bss)
-    }
-    . = ALIGN(4096); /* align to page size */
-    __bss_end = .;
-    __end = .;
+        . = ALIGN(4096); /* align to page size */
+    } > OCM
+    __bss_start = ADDR(.bss);
+    __bss_end = ADDR(.bss) + SIZEOF(.bss);
+
+    .stack (NOLOAD) : {
+      . += STACK_SIZE;
+    } > OCM
+    __stack_end = ADDR(.stack);
+    __stack_start = ADDR(.stack) + SIZEOF(.stack);
 
   /DISCARD/ :
   {

src/cortex_a9/regs.rs

@@ -30,10 +30,16 @@ macro_rules! def_reg_set {
     }
 }
 
+/// Stack Pointer
 pub struct SP;
 def_reg_get!(SP, u32, "mov $0, sp");
 def_reg_set!(SP, u32, "mov sp, $0");
 
+/// Link register (function call return address)
+pub struct LR;
+def_reg_get!(LR, u32, "mov $0, lr");
+def_reg_set!(LR, u32, "mov lr, $0");
+
 pub struct MPIDR;
 def_reg_get!(MPIDR, u32, "mrc p15, 0, $0, c0, c0, 5");
 

src/main.rs

@@ -20,7 +20,7 @@ use crate::cortex_a9::{asm, regs::*};
 extern "C" {
     static mut __bss_start: u32;
     static mut __bss_end: u32;
-    static mut __end: u32;
+    static mut __stack_start: u32;
 }
 
 #[link_section = ".text.boot"]
@@ -28,11 +28,10 @@ extern "C" {
 #[naked]
 pub unsafe extern "C" fn _boot_cores() -> ! {
     const CORE_MASK: u32 = 0x3;
-    let stack_start = __end + 4096;
 
     match MPIDR.get() & CORE_MASK {
         0 => {
-            SP.set(stack_start);
+            SP.set(&mut __stack_start as *mut _ as u32);
             boot_core0();
         }
         _ => loop {