On Tue, Jun 14, 2016 at 10:08:25AM -0400, Dave Anderson wrote:
>
> > Dave,
> >
> > On Mon, Jun 13, 2016 at 04:06:22PM -0400, Dave Anderson wrote:
> > >
> > >
> > > ----- Original Message -----
> > > > In my next version of kdump patch, the following VMCOREINFO will be
> > > > added:
> > > > NUMBER(VA_BITS)
> > > > NUMBER(kimage_voffset)
> > > > NUMBER(PHYS_OFFSET)
> > > > KERNELOFFSET
> >
> > Is "KERNELOFFSET" useful for arm64?
> > As you said, this value is used as a trigger of KASLR_CHECK,
> > but the current kernel doesn't have "randomize_modules".
>
> Right, so AIUI, this crash-7.0.7 update is not valid for Linux 4.1 and later
> kernels where "randomize_modules" was removed:
>
> - Linux 3.15 and later kernels configured with CONFIG_RANDOMIZE_BASE
> can be now be readily identified because of new kernel symbols that
> have been added. For those kernels, the new "--kaslr=<offset>"
> and/or "--kaslr=auto" options are not necessary for ELF or compressed
> kdump vmcores, or for live systems that have /proc/kallsyms showing
> the relocated symbol values. A new KASLR initialization function
> called kaslr_init() is now called by symtab_init() prior to the
> initial symbol-sorting operation. If kaslr_init() determines that
> KASLR may be in effect, it will trigger a search for the relevant
> vmlinux symbols during the sorting operation, which in turn will
> cause the relocation value to be automatically calculated.
> (anderson@xxxxxxxxxx)
>
> So for those kernels, --kaslr would be required.
>
> But it appears that I can just change crash to look for "module_load_offset",
> which went into the kernel at the same time as "randomize_modules":
>
> +#ifdef CONFIG_RANDOMIZE_BASE
> +static unsigned long module_load_offset;
> +static int randomize_modules = 1;
> +
>
> and still exists after it was removed from arch/x86/kernel/module.c:
>
> #ifdef CONFIG_RANDOMIZE_BASE
> static unsigned long module_load_offset;
> -static int randomize_modules = 1;
>
> For arm64 in the crash utility, I see that you would never use KASLR_CHECK because
> (RELOC_AUTO|KASLR) gets set by default if NEW_VMEMMAP is set.
>
> Would it be useful for makedumpfile?
Given that makedumpfile doesn't reply on vmlinux, "kaslr_offset" is
not useful.
-> Pratyush, any comments?
So I'd like to exclude KERNELOFFSET in my kexec/dkump patch, v19,
hopefully posted this weekend.
(This won't hurt crash utility anyway.)
Thanks,
-Takahiro AKASHI
> And while I understand you're dead set against
> adding anything that could be considered superfluous, but since it does exist for x86_64,
> it seems natural to include it for arm64.
>
> Dave
>
>
>
>
>
> > Thanks,
> > -Takahiro AKASHI
> >
>
> --
> Crash-utility mailing list
> Crash-utility@xxxxxxxxxx
> https://www.redhat.com/mailman/listinfo/crash-utility
--
Crash-utility mailing list
Crash-utility@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/crash-utility
