kdump/kexec: calculate note size at compile time

Currently the size of the per-cpu region reserved to save crash notes is
set by the per-architecture value MAX_NOTE_BYTES.  Which in turn is
currently set to 1024 on all supported architectures.

While testing ia64 I recently discovered that this value is in fact too
small.  The particular setup I was using actually needs 1172 bytes.  This
lead to very tedious failure mode where the tail of one elf note would
overwrite the head of another if they ended up being alocated sequentially
by kmalloc, which was often the case.

It seems to me that a far better approach is to caclculate the size that
the area needs to be.  This patch does just that.

If a simpler stop-gap patch for ia64 to be squeezed into 2.6.21(.X) is
needed then this should be as easy as making MAX_NOTE_BYTES larger in
arch/asm-ia64/kexec.h.  Perhaps 2048 would be a good choice.  However, I
think that the approach in this patch is a much more robust idea.

Acked-by:  Vivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 0 insertions, 2 deletions

diff --git a/include/asm-i386/kexec.h b/include/asm-i386/kexec.h
index bcb5b21de2d2..4b9dc9e6b701 100644
--- a/include/asm-i386/kexec.h
+++ b/include/asm-i386/kexec.h
@@ -45,8 +45,6 @@
 /* We can also handle crash dumps from 64 bit kernel. */
 #define vmcore_elf_check_arch_cross(x) ((x)->e_machine == EM_X86_64)
 
-#define MAX_NOTE_BYTES 1024
-
 /* CPU does not save ss and esp on stack if execution is already
  * running in kernel mode at the time of NMI occurrence. This code
  * fixes it.