lkml.org 
[lkml]   [2007]   [Mar]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH] kdump/kexec: calculate note size at compile time
    On Wed, Mar 28, 2007 at 03:18:58PM +0900, Simon Horman wrote:
    > 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.
    >

    Makes sense to me. Calculating the size based on elf_prstatus is better
    than hardcoding it to some value.

    A minor query is inlined below.

    [..]
    > ===================================================================
    > --- linux-2.6.orig/include/linux/kexec.h 2007-03-28 09:42:14.000000000 +0900
    > +++ linux-2.6/include/linux/kexec.h 2007-03-28 12:32:50.000000000 +0900
    > @@ -7,6 +7,8 @@
    > #include <linux/linkage.h>
    > #include <linux/compat.h>
    > #include <linux/ioport.h>
    > +#include <linux/elfcore.h>
    > +#include <linux/elf.h>
    > #include <asm/kexec.h>
    >
    > /* Verify architecture specific macros are defined */
    > @@ -31,6 +33,13 @@
    > #error KEXEC_ARCH not defined
    > #endif
    >
    > +#define KEXEC_NOTE_NAME "CORE"
    > +#define KEXEC_NOTE_HEAD_BYTES ALIGN(sizeof(struct elf_note), 4)
    > +#define KEXEC_NOTE_NAME_BYTES ALIGN(strlen(KEXEC_NOTE_NAME) + 1, 4)
    > +#define KEXEC_NOTE_BODY_BYTES ALIGN(sizeof(struct elf_prstatus), 4)
    > +#define KEXEC_NOTE_BYTES ( (KEXEC_NOTE_HEAD_BYTES * 2) + \

    Why are we multiplying KEXEC_NOTE_HEAD_BYTES with 2?

    Thanks
    Vivek
    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2007-03-28 08:47    [W:0.025 / U:2.508 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site