split kernel into 2 stages; second stage gets copied to 0x0 and runs from there

1 files changed, 27 insertions, 0 deletions

diff --git a/kernel_stage1.ld b/kernel_stage1.ld
new file mode 100644
index 0000000..3130634
--- /dev/null
+++ b/kernel_stage1.ld
@@ -0,0 +1,27 @@
+ENTRY(_boot) /* defined in boot.S; qemu needs it to run elf file */
+
+/* Code starts at  0x8000 - that's where RPis in 32-bit mode load
+ * kernel at. My experiments do, however, show, that qemu emulating
+ * RPi2 loads the kernel at 0x10000! (took some pain to find out).
+ * rpi-open-firmware, on the other hand, loads kernel at 0x2000000!
+ * This is not really a problem, since:
+ *   1. We can use our bootloader to load the kernel at 0x8000
+ *   2. We've rewritten stage 1 of both bootloader and kernel in
+ *      careful assembly, so that they should work regardless of
+ *      where they are loaded.
+ *   3. In qemu, we can load kernel.elf instead of raw binary
+ *      (qemu will do the right thing then)
+ */
+
+SECTIONS
+{
+
+	. = 0x8000;
+
+	__start = .;
+	.kernel_stage1 :
+	{
+		KEEP(kernel_stage1.o)
+	}
+	__end = .;
+}