[PATCH] x86_64: Patch to make the head.S-must-be-first-in-vmlinux order explicit

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>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/arch/x86_64/kernel/head.S b/arch/x86_64/kernel/head.S
index 0cddcc0..6df05e6 100644 (file)
--- a/arch/x86_64/kernel/head.S
+++ b/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 */ 

diff --git a/arch/x86_64/kernel/vmlinux.lds.S b/arch/x86_64/kernel/vmlinux.lds.S
index 74db006..029be20 100644 (file)
--- a/arch/x86_64/kernel/vmlinux.lds.S
+++ b/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