don't embed stage2 of bootloader as binary blob - use smart section naming

5 files changed, 32 insertions, 66 deletions

diff --git a/Makefile b/Makefile
index d1d66fa..35cc48c 100644
--- a/Makefile
+++ b/Makefile
@@ -30,17 +30,14 @@ PL_0_test.elf : PL0_test.o uart.o
 kernel.elf : boot.o kernel.o uart.o PL_0_test_embeddable.o demo_functionality.o paging.o libkernel_renamed.o interrupt_vector.o interrupts.o
 	arm-none-eabi-gcc -T linker.ld -o $@ $(ELFFLAGS) $^
 
-loader_stage2.elf : loader_stage2.o uart.o
-	arm-none-eabi-gcc -T loader_stage2.ld -o $@ $(ELFFLAGS) $^
+loader.elf : boot.o loader_stage1.o loader_stage2.o uart.o
+	arm-none-eabi-gcc -T loader_linker.ld -o $@ $(ELFFLAGS) $^
 
-loader_stage2.img : loader_stage2.elf
+loader.img : loader.elf
 	arm-none-eabi-objcopy $^ -O binary $@
+# check if the resulting image is not too big
 	test -n "$$(find $@ -size -16384c)" || exit -1
 
-loader.elf : boot.o loader_stage1.o loader_stage2_embeddable.o
-	arm-none-eabi-gcc -T loader_stage1.ld -o $@ $(ELFFLAGS) $^
-
-
 qemu-elf : kernel.elf
 	qemu-system-arm -m 256 -M raspi2 -serial stdio -kernel $^
 
diff --git a/loader_stage1.ld b/loader_linker.ld
index 18fe477..a8942f6 100644
--- a/loader_stage1.ld
+++ b/loader_linker.ld
@@ -18,15 +18,26 @@ SECTIONS
     /* For AArch64, use . = 0x80000; Unless this too is wrong */
     
     __start = .;
+    __text_stage1_start = .;
+    .text_stage1 :
+    {
+        KEEP(*(.text.boot))
+        *(.text.boot)
+        *(.text.stage1main)
+    }
+    . = ALIGN(4096); /* align to page size */
+    __text_stage1_end = .;
+
+    __stage2_start = .;
     __text_start = .;
     .text :
     {
-        KEEP(*(.text.boot))
-        *(.text)
+        KEEP(*(.text.stage2main))
+        *(.text.boot)
     }
     . = ALIGN(4096); /* align to page size */
     __text_end = .;
- 
+    
     __rodata_start = .;
     .rodata :
     {
@@ -52,5 +63,8 @@ SECTIONS
     . = ALIGN(4096); /* align to page size */
     __bss_end = .;
     __bss_size = __bss_end - __bss_start;
+
+    __stage2_end = .;
+    __stage2_size = __stage2_end - __stage2_start;
     __end = .;
 }
diff --git a/loader_stage1.c b/loader_stage1.c
index d209c15..aca439c 100644
--- a/loader_stage1.c
+++ b/loader_stage1.c
@@ -2,24 +2,25 @@
 #include <stdint.h>
 #include <global.h>
 
-char *const stage2_addr = ((void*) 0x4000);
+#define STAGE2_ADDR ((volatile char*) 0x4000)
 
-// there's one tricky thing about embedding file in executable;
-// mainly, symbols are visible to c code as extern chars, but the actual
+// There's one tricky thing about managing executable's own code.
+// Mainly, symbols are visible to c code as extern chars, but the actual
 // values are their adresses... see the code below
 extern char
-  _binary_loader_stage2_img_start,
-  _binary_loader_stage2_img_end,
-  _binary_loader_stage2_img_size;
+  __stage2_start,
+  __stage2_end,
+  __stage2_size;
 
+__attribute__((section(".text.stage1main")))
 void kernel_main(uint32_t r0, uint32_t r1, uint32_t atags)
 {
-  // stage2 of the bootloader is a blob embedded in executable;
+  // stage2 of the bootloader is part of executable;
   // copy it over to it's destination place
   // TODO implement a memcpy() somewhere and use it instead of loops
-  for (size_t i = 0; i < (size_t) &_binary_loader_stage2_img_size; i++)
-    stage2_addr[i] = (&_binary_loader_stage2_img_start)[i];
+  for (size_t i = 0; i < (size_t) &__stage2_size; i++)
+    STAGE2_ADDR[i] = (&__stage2_start)[i];
 
   // jump to stage2
-  ((void(*)(uint32_t, uint32_t, uint32_t))stage2_addr)(r0, r1, atags);
+  ((void(*)(uint32_t, uint32_t, uint32_t))STAGE2_ADDR)(r0, r1, atags);
 }
diff --git a/loader_stage2.c b/loader_stage2.c
index e221dda..7b5087a 100644
--- a/loader_stage2.c
+++ b/loader_stage2.c
@@ -36,5 +36,3 @@ stage2(uint32_t r0, uint32_t r1, uint32_t atags)
   asm volatile("bx %0" :: "r" (kernel_load_addr) : "memory");
 }
 
-void *const _start = ((void*) stage2); // for linker script
-
diff --git a/loader_stage2.ld b/loader_stage2.ld
deleted file mode 100644
index 8f215e9..0000000
--- a/loader_stage2.ld
+++ /dev/null
@@ -1,44 +0,0 @@
-ENTRY(_start)
- 
-SECTIONS
-{
-    /* stage2 bootloader gets loaded at 0x4000 */
-    . = 0x4000;
-    __start = .;
-    __text_start = .;
-    .text :
-    {
-        /* have entry point at the beginning */
-        KEEP(*(.text.stage2main))
-        *(.text)
-    }
-    . = ALIGN(4096); /* align to page size */
-    __text_end = .;
- 
-    __rodata_start = .;
-    .rodata :
-    {
-        *(.rodata)
-    }
-    . = ALIGN(4096); /* align to page size */
-    __rodata_end = .;
- 
-    __data_start = .;
-    .data :
-    {
-        *(.data)
-    }
-    . = ALIGN(4096); /* align to page size */
-    __data_end = .;
- 
-    __bss_start = .;
-    .bss :
-    {
-        bss = .;
-        *(.bss)
-    }
-    . = ALIGN(4096); /* align to page size */
-    __bss_end = .;
-    __bss_size = __bss_end - __bss_start;
-    __end = .;
-}