From: "Jan Beulich" <JBeulich@suse.com>
To: Johannes Erdfelt <johannes@erdfelt.com>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: elena.ufimtseva@oracle.com, jeremy@goop.org,
hanweidong@huawei.com, john.liuqiming@huawei.com,
paul.voccio@rackspace.com,
Konrad Rzeszutek Wilk <konrad@kernel.org>,
daniel.kiper@oracle.com, major.hayden@rackspace.com,
liuyingdong@huawei.com, aliguori@amazon.com,
xiantao.zxt@alibaba-inc.com, steven.wilson@rackspace.com,
peter.huangpeng@huawei.com, msw@amazon.com,
xen-devel@lists.xenproject.org, rick.harris@rackspace.com,
josh.kearney@rackspace.com, jinsong.liu@alibaba-inc.com,
amesserl@rackspace.com, mpohlack@amazon.com, dslutz@verizon.com,
fanhenglong@huawei.com, Andrew.Cooper3@citrix.com
Subject: Re: [RFC PATCH v3.1 1/2] xsplice: rfc.v3.1
Date: Tue, 11 Aug 2015 08:17:12 -0600 [thread overview]
Message-ID: <55CA20080200007800099A18@prv-mh.provo.novell.com> (raw)
In-Reply-To: <20150731154626.GA30139@localhost.localdomain>
>>> On 31.07.15 at 17:46, <konrad.wilk@oracle.com> wrote:
> On Thu, Jul 30, 2015 at 09:47:40AM -0700, Johannes Erdfelt wrote:
>> On Mon, Jul 27, 2015, Konrad Rzeszutek Wilk <konrad@kernel.org> wrote:
>> > +struct xsplice_reloc_howto {
>> > + uint32_t howto; /* XSPLICE_HOWTO_* */
>> > + uint32_t flag; /* XSPLICE_HOWTO_FLAG_* */
>> > + uint32_t size; /* Size, in bytes, of the item to be relocated. */
>> > + uint32_t r_shift; /* The value the final relocation is shifted right by; used to drop unwanted data from the relocation. */
>> > + uint64_t mask; /* Bitmask for which parts of the instruction or data are replaced with the relocated value. */
>> > + uint8_t pad[8]; /* Must be zero. */
>> > +};
>>
>> I'm curious how r_shift and mask are used. I'm familiar with x86 and
>> x86_64 and I'm not sure how these fit in. Is this to support other
>> architectures?
>
> It is to patch up data. We can specify the exact mask for an unsigned
> int - so we only patch specific bits. Ditto if we want to remove certain
> values.
Still I don't see a practical use: What relocated item would (on x86)
be stored starting at other than bit 0 of a byte/word? Also, wouldn't
a shift count be redundant with the mask value anyway?
Jan
next prev parent reply other threads:[~2015-08-11 14:17 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-27 19:20 [RFC PATCH v3.1] xSplice design Konrad Rzeszutek Wilk
2015-07-27 19:20 ` [RFC PATCH v3.1 1/2] xsplice: rfc.v3.1 Konrad Rzeszutek Wilk
2015-07-30 16:47 ` Johannes Erdfelt
2015-07-31 15:46 ` Konrad Rzeszutek Wilk
2015-08-11 14:17 ` Jan Beulich [this message]
2015-07-27 19:20 ` [RFC PATCH v3.1 2/2] xsplice: Add hook for build_id Konrad Rzeszutek Wilk
2015-07-28 15:51 ` Andrew Cooper
2015-07-28 16:35 ` Konrad Rzeszutek Wilk
2015-08-05 8:50 ` Martin Pohlack
2015-08-05 8:58 ` Andrew Cooper
2015-08-05 13:27 ` Martin Pohlack
2015-08-05 14:06 ` (no subject) Martin Pohlack
2015-08-05 14:09 ` [PATCH] xsplice: Use ld-embedded build-ids Martin Pohlack
2015-08-11 14:12 ` Jan Beulich
2015-08-14 12:59 ` Martin Pohlack
2015-08-14 13:54 ` Jan Beulich
2015-08-14 13:57 ` Martin Pohlack
2015-09-15 18:38 ` Konrad Rzeszutek Wilk
2015-08-11 14:02 ` [RFC PATCH v3.1 2/2] xsplice: Add hook for build_id Jan Beulich
2015-08-05 8:55 ` Hotpatch construction and __LINE__ (was: [RFC PATCH v3.1] xSplice design.) Martin Pohlack
2015-08-05 13:25 ` Hotpatch construction and __LINE__ Andrew Cooper
2015-08-12 8:09 ` Jan Beulich
2015-08-12 9:55 ` Andrew Cooper
2015-11-03 18:21 ` Ross Lagerwall
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