From: "Jan Beulich" <JBeulich@suse.com>
To: Konrad Rzeszutek Wilk <konrad@kernel.org>
Cc: andrew.cooper3@citrix.com, julien.grall@arm.com,
sstabellini@kernel.org, xen-devel@lists.xenproject.org
Subject: Re: [PATCH v2 3/5] xen/livepatch/ARM32: Don't load and crash on livepatches loaded with wrong alignment.
Date: Wed, 20 Sep 2017 09:51:06 -0600 [thread overview]
Message-ID: <59C2AA8A020000780017D8BF@prv-mh.provo.novell.com> (raw)
In-Reply-To: <20170920151211.GA5508@localhost.localdomain>
>>> On 20.09.17 at 17:12, <konrad@kernel.org> wrote:
> On Tue, Sep 19, 2017 at 09:04:44AM -0600, Jan Beulich wrote:
>> >>> On 18.09.17 at 21:37, <konrad.wilk@oracle.com> wrote:
>> > On Tue, Sep 12, 2017 at 02:57:04AM -0600, Jan Beulich wrote:
>> >> >>> On 12.09.17 at 02:22, <konrad@kernel.org> wrote:
>> >> > 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)?
>> >
>> > gcc
>> >
>> > Looking at the xen_bye_world.o produced by cross-compiler:
>> >
>> > xen_bye_world.o: file format elf32-littlearm
>> >
>> > Contents of section .rodata:
>> > 0000 78656e5f 65787472 615f7665 7273696f xen_extra_versio
>> > 0010 6e00 n.
>> >
>> > And native:
>> >
>> > xen_bye_world.o: file format elf32-littlearm
>> >
>> > Contents of section .rodata:
>> > 0000 78656e5f 65787472 615f7665 7273696f xen_extra_versio
>> > 0010 6e000000 n...
>>
>> This may rather be a gas than a gcc behavioral difference. What's
>> the alignment of .rodata in both cases?
>
> Cross:
>
> * on the livepatch:
> ..snip..
> [ 4] .rodata PROGBITS 00000000 000074 000012 00 A 0 0 4
> [ 5] .rodata.str1.4 PROGBITS 00000000 000088 00000b 01 AMS 0 0 4
> [ 6] .livepatch.depend PROGBITS 00000000 000093 000024 00 A 0 0 1
>
> * on the .o file:
> Section Headers:
> [Nr] Name Type Addr Off Size ES Flg Lk Inf Al
> .. snip..
> [ 1] .text PROGBITS 00000000 000034 000000 00 AX 0 0 1
> [ 2] .data PROGBITS 00000000 000034 000000 00 WA 0 0 1
> [ 3] .bss NOBITS 00000000 000034 000000 00 WA 0 0 1
> [ 4] .rodata PROGBITS 00000000 000034 000014 00 A 0 0 4
> [ 5] .livepatch.funcs PROGBITS 00000000 000048 000034 00 WA 0 0 4
Hard to believe - a 0x14 bytes section gets shrunk to 0x12 bytes
by (presumably) ld -r?
> Native:
>
> * on the livepatch:
> ..snip..
> [ 4] .rodata PROGBITS 00000000 000074 000014 00 A 0 0 4
> [ 5] .rodata.str1.4 PROGBITS 00000000 000088 00000c 01 AMS 0 0 4
> [ 6] .livepatch.depend PROGBITS 00000000 000094 000024 00 A 0 0 1
>
> * on the .o file:
> ..snip..
> [ 1] .text PROGBITS 00000000 000034 000000 00 AX 0 0 1
> [ 2] .data PROGBITS 00000000 000034 000000 00 WA 0 0 1
> [ 3] .bss NOBITS 00000000 000034 000000 00 WA 0 0 1
> [ 4] .rodata PROGBITS 00000000 000034 000012 00 A 0 0 4
> [ 5] .livepatch.funcs PROGBITS 00000000 000048 000034 00 WA 0 0 4
With things being the other way around here - did you perhaps mix
up files?
Jan
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next prev parent reply other threads:[~2017-09-20 15:51 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-26 19:47 [PATCH v2] Livepatch fixes for v4.10 (v2) Konrad Rzeszutek Wilk
2017-07-26 19:47 ` [PATCH v2 1/5] livepatch: Tighten alignment checks Konrad Rzeszutek Wilk
2017-07-31 13:46 ` Jan Beulich
2017-07-26 19:47 ` [PATCH v2 2/5] livepatch: Include sizes when an mismatch occurs Konrad Rzeszutek Wilk
2017-07-31 13:51 ` Jan Beulich
2017-07-26 19:47 ` [PATCH v2 3/5] xen/livepatch/ARM32: Don't load and crash on livepatches loaded with wrong alignment Konrad Rzeszutek Wilk
2017-07-26 22:27 ` Andrew Cooper
2017-07-31 13:55 ` Jan Beulich
2017-07-31 16:04 ` Konrad Rzeszutek Wilk
2017-08-02 9:20 ` Jan Beulich
2017-09-07 17:36 ` Konrad Rzeszutek Wilk
2017-09-08 9:30 ` Jan Beulich
2017-09-09 12:05 ` Konrad Rzeszutek Wilk
2017-09-11 9:01 ` Jan Beulich
2017-09-12 0:22 ` Konrad Rzeszutek Wilk
2017-09-12 8:57 ` Jan Beulich
2017-09-18 19:37 ` Konrad Rzeszutek Wilk
2017-09-19 15:04 ` Jan Beulich
2017-09-20 15:12 ` Konrad Rzeszutek Wilk
2017-09-20 15:51 ` Jan Beulich [this message]
2017-07-26 19:47 ` [PATCH v2 4/5] alternative/x86/arm32: Align altinstructions (and altinstr_replacement) sections Konrad Rzeszutek Wilk
2017-07-31 14:01 ` Jan Beulich
2017-09-11 18:59 ` Konrad Rzeszutek Wilk
2017-07-26 19:47 ` [PATCH v2 5/5] livepatch: Declare live patching as a supported feature Konrad Rzeszutek Wilk
2017-07-31 14:03 ` Jan Beulich
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