Re: [Xen-devel] [PATCH v2 3/5] xen/livepatch/ARM32: Don't load and crash on livepatches loaded with wrong alignment.

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 12.09.17 at 02:22, <konrad@xxxxxxxxxx> wrote:
> On Mon, Sep 11, 2017 at 03:01:15AM -0600, Jan Beulich wrote:
>> Hmm, as long as the relocation isn't required to be against aligned
>> fields only (mandated by the processor ABI) I think the code doing
>> the relocations would instead need to split the access, rather than
>> calling the section misaligned or increasing alignment beyond what
>> the ELF section headers say.
> 
> Maybe the serial log would explain this better:
> 
> xend_config_format     : 4
> Executing: '(set -e;cd /root/test/livepatch;xen-livepatch load 
> xen_bye_world.livepatch)' ..(XEN) livepatch.c:413: livepatch: xen_bye_world: 
> Loaded .note.gnu.build-id at 00a08000
> (XEN) livepatch.c:413: livepatch: xen_bye_world: Loaded .text at 00a06000
> (XEN) livepatch.c:413: livepatch: xen_bye_world: Loaded .rodata at 00a08024
> (XEN) livepatch.c:413: livepatch: xen_bye_world: Loaded .rodata.str1.4 at 
> 00a08038
> (XEN) livepatch.c:413: livepatch: xen_bye_world: Loaded .livepatch.depends at 
> 00a08043
>[...]
> Keep in mind that this only happens if I cross-compile ARM32 under x86.

That would suggest a build environment / build tools issue then:
Cross builds aren't supposed to produce binaries different from
native builds.

> If I compile the test-case under ARM32 it works OK (as the
> .livepatch.depends ends up being aligned to four bytes).

So why is that? What entity is creating this section (or the
directive(s) to create it)?

Jan


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