[Patch 1/4] avoid entry.S functions from reordering

[Arjan van de Ven <arjan@linux.intel.com>]

This patch puts the code from head.S in a special .bootstrap.text
section.

I'm working on a patch to reorder the functions in the kernel (I'll post
that later), but for x86-64 at least the kernel bootstrap requires that the
head.S functions are on the very first page/pages of the kernel text. This
is understandable since the bootstrap is complex enough already and not a
problem at all, it just means they aren't allowed to be reordered. This
patch puts these special functions into a separate section to document this,
and to guarantee this in the light of possibly reordering the rest later.

(So this patch doesn't fix a bug per se, but makes things more robust by
making the order of these functions explicit)

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
---
 arch/x86_64/kernel/head.S        |    1 +
 arch/x86_64/kernel/vmlinux.lds.S |    1 +
 2 files changed, 2 insertions(+)

Index: linux-reorder2/arch/x86_64/kernel/head.S
===================================================================
--- linux-reorder2.orig/arch/x86_64/kernel/head.S
+++ linux-reorder2/arch/x86_64/kernel/head.S
@@ -26,6 +26,7 @@
  */
 
 	.text
+	.section .bootstrap.text
 	.code32
 	.globl startup_32
 /* %bx:	 1 if coming from smp trampoline on secondary cpu */ 
Index: linux-reorder2/arch/x86_64/kernel/vmlinux.lds.S
===================================================================
--- linux-reorder2.orig/arch/x86_64/kernel/vmlinux.lds.S
+++ linux-reorder2/arch/x86_64/kernel/vmlinux.lds.S
@@ -20,6 +20,7 @@ SECTIONS
   phys_startup_64 = startup_64 - LOAD_OFFSET;
   _text = .;			/* Text and read-only data */
   .text :  AT(ADDR(.text) - LOAD_OFFSET) {
+	*(.bootstrap.text)
 	*(.text)
 	SCHED_TEXT
 	LOCK_TEXT

-
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