kexec fails to boot kernels where CONFIG_RANDOMIZE_BASE=y is set
vgoyal at redhat.com
Fri Aug 22 06:16:23 PDT 2014
On Fri, Aug 22, 2014 at 07:59:02PM +0800, Baoquan He wrote:
> So we have 2 choices for kexec/kdump:
> 1) kexec/kdump kernel need not randomize the kernel starting point.
> Since kexec/kdump kernel is only for testing or emergencey, its life is
> not too long.
> 2) makes slots around the kernel input addr. This is only useful for
> kexec. I can't imagine why kdump need it.
> Hi Thomas,
> Could you test below patch?
> This is patch is from Lu Yinghai.
> arch/x86/boot/compressed/misc.c | 14 +++++++++-----
> 1 file changed, 9 insertions(+), 5 deletions(-)
> Index: linux-2.6/arch/x86/boot/compressed/misc.c
> --- linux-2.6.orig/arch/x86/boot/compressed/misc.c
> +++ linux-2.6/arch/x86/boot/compressed/misc.c
> @@ -235,8 +235,9 @@ static void error(char *x)
> -#if CONFIG_X86_NEED_RELOCS
> -static void handle_relocations(void *output, unsigned long output_len)
> +#ifdef CONFIG_X86_NEED_RELOCS
> +static void handle_relocations(void *output_orig, void *output,
> + unsigned long output_len)
> int *reloc;
> unsigned long delta, map, ptr;
> @@ -247,7 +248,7 @@ static void handle_relocations(void *out
> * Calculate the delta between where vmlinux was linked to load
> * and where it was actually loaded.
> - delta = min_addr - LOAD_PHYSICAL_ADDR;
> + delta = min_addr - (unsigned long)output_orig;
So what does this patch actuall do? If I try to trace back output_orig,
it seems to be same as LOAD_PHYSICAL_ADDR. That means there should not
be any effect of this change? Or did I not understand it.
Look at head_64.S
movq $LOAD_PHYSICAL_ADDR, %rbp
movq %rbp, %r8 /* output target address */
call decompress_kernel /* returns kernel location in %rax */
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