[kexec-tools PATCH] x86: extend kernel text size up to 1GB

[Dave Young]

On 03/14/14 at 02:12pm, Dave Young wrote:
> On 03/12/14 at 11:13am, WANG Chao wrote:
> > Currently kexec hard code X86_64_KERNEL_TEXT_SIZE to 512M. With kASLR
> > enabled (CONFIG_RANDOMIZED_BASE=y), kernel image base offset could be
> > randomized from 0 to 1GB and kexec-tools fails to get kernel virtual
> > address from /proc/kcore when the offset is >512M.
> > 
> > Now extend X86_64_KERNEL_TEXT_SIZE to 1GB to adapt kASLR.
> > 
> > Signed-off-by: WANG Chao <chaowang at redhat.com>
> > ---
> >  kexec/arch/i386/crashdump-x86.h | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/kexec/arch/i386/crashdump-x86.h b/kexec/arch/i386/crashdump-x86.h
> > index e68b626..a5b2dfd 100644
> > --- a/kexec/arch/i386/crashdump-x86.h
> > +++ b/kexec/arch/i386/crashdump-x86.h
> > @@ -18,7 +18,7 @@ int load_crashdump_segments(struct kexec_info *info, char *mod_cmdline,
> >  #define X86_64_MAXMEM        		0x3fffffffffffUL
> >  
> >  /* Kernel text size */
> > -#define X86_64_KERNEL_TEXT_SIZE  (512UL*1024*1024)
> > +#define X86_64_KERNEL_TEXT_SIZE  (1UL*1024*1024*1024)
> 
> Should define a new macro such as: X86_KERNEL_TEXT_START_LIMIT (1UL*1024*1024*1024)
> and then check end addr with X86_64_KERNEL_TEXT_SIZE + X86_64_KERNEL_TEXT_SIZE

I means check ktext with range <1G - 1.5G>

> 
> Previously I did not find this problem probably because kernel text happen to randomized
> to a address < 512M..
> 
> BTW since we can get physical start and size from /proc/iomem, why not just get
> vaddr by phys_start + PAGE_OFFSET.

Ignore above question, /proc/iomem can not get right end addr which includes not only code
and data.

Current kaslr has a limit up value 0x40000000 in Kconfig so the biggest value is 1G, but
it could be change to other value in the future. It will be ideal that we can export the
end addr somewhere for example /proc/iomem. 

> 
> >  
> >  #define CRASH_MAX_MEMMAP_NR	CRASH_MAX_MEMORY_RANGES
> >  #define CRASH_MAX_MEMORY_RANGES	(MAX_MEMORY_RANGES + 2)
> > -- 
> > 1.8.5.3
> > 
> > 
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