On Mon, Oct 23, 2017 at 06:24:12PM +0800, jeffy wrote:
> Hi Russell,
>
> Thanks for your reply.
>
> On 10/23/2017 04:50 PM, Russell King - ARM Linux wrote:
> >>>
> >>>hmm, right, didn't notice the data is already aligned...
> >>>so it's indeed caused by the ksym:
> >>>
> >>> [ 9] .data PROGBITS 006ce000 6d6000 000200 00 WA 0
> >>>0 4096
> >>> [10] ___ksymtab+sort PROGBITS 006ce200 6d6200 000008 00 WA 0
> >>>0 4
> >>> [11] .bss NOBITS 006ce208 6d6208 00001c 00 WA 0
> >>>0 4
> >It's earlier - look for __ksymtab_strings.
>
> the problem i meet is the appended dtb code found dtb invalid. i thought
> that is because of unaligned zImage size, but i was wrong...
Hmm, you really ought not to be using the appended dtb code for modern
systems - the appended dtb system is there for old boot loaders that
are incapable of dealing with a dtb. As is said in the option's help
text:
This is meant as a backward compatibility convenience for those
systems with a bootloader that can't be upgraded to accommodate
the documented boot protocol using a device tree.
Beware that there is very little in terms of protection against
this option being confused by leftover garbage in memory that might
look like a DTB header after a reboot if no actual DTB is appended
to zImage. Do not leave this option active in a production kernel
if you don't intend to always append a DTB. Proper passing of the
location into r2 of a bootloader provided DTB is always preferable
to this option.
If you rely on it, and you have something that looks like a dtb after
the image, then things will go wrong, so it's better _not_ to use it
and to keep it disabled.
That aside, thanks for doing a more in-depth analysis of what is going
on, which helps to understand /why/ Ard's fix works (whereas before
it was rather nebulous.)
I wonder whether we ought to tell the linker to discard any unknown
sections by adding at the bottom:
/DISCARD/ { *(*) }
but I do think we need to document this, specifically that _edata must
point to the first byte after the binary file, and that the only
sections after it are allowed to be the .bss and stack sections.
--
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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