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xen-devel
[Xen-devel] Re: [patch 17/26] Xen-paravirt_ops: Add nosegneg capability
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To: |
Roland McGrath <roland@xxxxxxxxxx> |
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Subject: |
[Xen-devel] Re: [patch 17/26] Xen-paravirt_ops: Add nosegneg capability to the vsyscall page notes |
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From: |
Jeremy Fitzhardinge <jeremy@xxxxxxxx> |
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Date: |
Fri, 16 Mar 2007 14:56:24 -0700 |
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Cc: |
Zachary Amsden <zach@xxxxxxxxxx>, Jakub Jelinek <jakub@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, Ian Pratt <ian.pratt@xxxxxxxxxxxxx>, Andi Kleen <ak@xxxxxx>, Rusty Russell <rusty@xxxxxxxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, Ulrich Drepper <drepper@xxxxxxxxxx>, Chris Wright <chrisw@xxxxxxxxxxxx>, virtualization@xxxxxxxxxxxxxx, Ingo Molnar <mingo@xxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Christian Limpach <Christian.Limpach@xxxxxxxxxxxx> |
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Fri, 16 Mar 2007 14:55:37 -0700 |
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Roland McGrath wrote:
> This should be:
>
> NOTE_KERNELCAP_BEGIN(1, 1)
> NOTE_KERNELCAP(0, "nosegneg")
> NOTE_KERNELCAP_END
>
> i.e. 1->0 in the "bit" member. (Note the ld.so.conf.d file must have the
> matching bit number for ldconfig-based lookups to do the right thing.)
> Or else:
>
> NOTE_KERNELCAP_BEGIN(1, 2)
> NOTE_KERNELCAP(0, "nosegneg")
> NOTE_KERNELCAP_END
>
> i.e. 1->2 in the "mask" member. (The mask value should be 1<<bit.)
>
Thanks Roland. I've never really understood this stuff, and I just
copied this cargo-cultishly.
I'm not quite sure what you're suggesting here though. Do you mean one of:
NOTE_KERNELCAP_BEGIN(1, 1)
NOTE_KERNELCAP(0, "nosegneg")
NOTE_KERNELCAP_END
or
NOTE_KERNELCAP_BEGIN(1, 2)
NOTE_KERNELCAP(1, "nosegneg")
NOTE_KERNELCAP_END
is the correct thing to use?
> Some pre-release glibc's (before 2.4) had a bug in the code that parses
> this, and would crash parsing the correct note. Using the wrong bit value
> with nonmatching mask worked around this. IIRC, no glibc release ever
> included the buggy version of the code. In nonbuggy glibc, the mismatched
> value causes the "nosegneg" to be omitted from the directory search (under
> LD_LIBRARY_PATH and default directories), though ldconfig-based lookups
> will work (the most common case).
>
Are you saying that one of the corrected forms might cause old glibcs to
crash, or just ignore nosegneg?
J
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