x86: fix spontaneous reboot with allyesconfig bzImage

recently the 64-bit allyesconfig bzImage kernel started spontaneously
rebooting during early bootup.

after a few fun hours spent with early init debugging, it turns out
that we've got this rather annoying limit on the size of the kernel
image:

      #define KERNEL_TEXT_SIZE  (40*1024*1024)

which limit my vmlinux just happened to pass:

       text           data       bss        dec       hex   filename
   29703744        4222751   8646224   42572719   2899baf   vmlinux

40 MB is 42572719 bytes, so my vmlinux was just 1.5% above this limit :-/

So it happily crashed right in head_64.S, which - as we all know - is
the most debuggable code in the whole architecture ;-)

So increase the limit to allow an up to 128MB kernel image to be mapped.
(should anyone be that crazy or lazy)

We have a full 4K of pagetable (level2_kernel_pgt) allocated for these
mappings already, so there's no RAM overhead and the limit was rather
pointless and arbitrary.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 6 insertions, 2 deletions

diff --git a/include/asm-x86/page_64.h b/include/asm-x86/page_64.h
index f7393bc..3e2e3ca 100644
--- a/include/asm-x86/page_64.h
+++ b/include/asm-x86/page_64.h
@@ -47,8 +47,12 @@
 #define __PHYSICAL_MASK_SHIFT	46
 #define __VIRTUAL_MASK_SHIFT	48
 
-#define KERNEL_TEXT_SIZE  (40*1024*1024)
-#define KERNEL_TEXT_START _AC(0xffffffff80000000, UL)
+/*
+ * Kernel image size is limited to 128 MB (see level2_kernel_pgt in
+ * arch/x86/kernel/head_64.S), and it is mapped here:
+ */
+#define KERNEL_TEXT_SIZE	(128*1024*1024)
+#define KERNEL_TEXT_START	_AC(0xffffffff80000000, UL)
 
 #ifndef __ASSEMBLY__
 void clear_page(void *page);