On 08/22/14 at 09:16am, Vivek Goyal wrote:
> 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)
> > asm("hlt");
> > }
> >
> > -#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.
No, kexec kernel has to be relocatable kernel. so it shoule be the
value calculated by code block surrounded by the MACRO checking.
(startup_32 + %rip + BP_kernel_alignment -1 )& ~(BP_kernel_alignment-1)
#ifdef CONFIG_RELOCATABLE
leaq startup_32(%rip) /* - $startup_32 */, %rbp
movl BP_kernel_alignment(%rsi), %eax
decl %eax
addq %rax, %rbp
notq %rax
andq %rax, %rbp
cmpq $LOAD_PHYSICAL_ADDR, %rbp
jge 1f
#endif
movq $LOAD_PHYSICAL_ADDR, %rbp
1:
/* Target address to relocate to for decompression */
leaq z_extract_offset(%rbp), %rbx
>
> Look at head_64.S
>
> movq $LOAD_PHYSICAL_ADDR, %rbp
> ...
> ...
> movq %rbp, %r8 /* output target address */
> call decompress_kernel /* returns kernel location in %rax */
>
> Thanks
> Vivek
>
> _______________________________________________
> kexec mailing list
> kexec at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec
