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Re: [PATCH] powerpc: New feature - HWCAP/HWCAP2 bits in the TCB
- From: "Carlos O'Donell" <carlos at redhat dot com>
- To: Rich Felker <dalias at libc dot org>, munroesj at linux dot vnet dot ibm dot com
- Cc: Alan Modra <amodra at gmail dot com>, libc-alpha at sourceware dot org
- Date: Wed, 08 Jul 2015 04:15:16 -0400
- Subject: Re: [PATCH] powerpc: New feature - HWCAP/HWCAP2 bits in the TCB
- Authentication-results: sourceware.org; auth=none
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On 07/06/2015 09:58 PM, Rich Felker wrote:
> I'll wait for Alan to respond since I feel like our conversation is
> getting nowhere and the concerns I'm trying to address (which I
> believe were raised originally by Carlos, not me) are not getting
> across to you clearly. Regardless of whose fault that is, maybe having
> a third party look at this can help resolve it.
Correct, I raised it originally when it came to light the requirement
was to support old versions of glibc.
My initial worry was around reused stacks and TCB getting garbage
from those stacks. I had not yet considered that the reserved
ABI space was not reserved in the layout macros for TLS.
Seeing Alan's response clarifies that though, the space is reserved
in the ABI document only, but in glibc we allow struct pthread to
move up into that reserved space to save on allocated pages.