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From: Peter Bergner <bergner@linux.ibm.com>
To: linux-api@vger.kernel.org, linux-arch@vger.kernel.org,
	"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc: Nicholas Piggin <npiggin@gmail.com>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Segher Boessenkool <segher@kernel.crashing.org>,
	GNU C Library <libc-alpha@sourceware.org>
Subject: [PING][PATCH] uapi/auxvec: Define AT_HWCAP3 and AT_HWCAP4 aux vector, entries
Date: Tue, 17 Oct 2023 18:14:53 -0500	[thread overview]
Message-ID: <4294d9ae-3f5e-4f81-b586-2c134d21896a@linux.ibm.com> (raw)
In-Reply-To: <fd879f60-3f0b-48d1-bfa1-6d337768207e@linux.ibm.com>

CCing linux-kernel for more exposure.

PING.  I'm waiting on a reply from anyone on the kernel side of things
to see whether they have an issue with reserving values for AT_HWCAP3
and AT_HWCAP4.  

I'll note reviews from the GLIBC camp did not have an issue with the below patch.

Thanks.

Peter


On 9/26/23 5:02 PM, Peter Bergner wrote:
> The powerpc toolchain keeps a copy of the HWCAP bit masks in our TCB for fast
> access by our __builtin_cpu_supports built-in function.  The TCB space for
> the HWCAP entries - which are created in pairs - is an ABI extension, so
> waiting to create the space for HWCAP3 and HWCAP4 until we need them is
> problematical, given distro unwillingness to apply ABI modifying patches
> to distro point releases.  Define AT_HWCAP3 and AT_HWCAP4 in the generic
> uapi header so they can be used in GLIBC to reserve space in the powerpc
> TCB for their future use.
> 
> I scanned both the Linux and GLIBC source codes looking for unused AT_*
> values and 29 and 30 did not seem to be used, so they are what I went
> with.  If anyone sees a problem with using those specific values, I'm
> amenable to using other values, just let me know what would be better.
> 
> Peter
> 
> 
> Signed-off-by: Peter Bergner <bergner@linux.ibm.com>
> ---
>  include/uapi/linux/auxvec.h | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/include/uapi/linux/auxvec.h b/include/uapi/linux/auxvec.h
> index 6991c4b8ab18..cc61cb9b3e9a 100644
> --- a/include/uapi/linux/auxvec.h
> +++ b/include/uapi/linux/auxvec.h
> @@ -32,6 +32,8 @@
>  #define AT_HWCAP2 26	/* extension of AT_HWCAP */
>  #define AT_RSEQ_FEATURE_SIZE	27	/* rseq supported feature size */
>  #define AT_RSEQ_ALIGN		28	/* rseq allocation alignment */
> +#define AT_HWCAP3 29	/* extension of AT_HWCAP */
> +#define AT_HWCAP4 30	/* extension of AT_HWCAP */
>  
>  #define AT_EXECFN  31	/* filename of program */
>  


  parent reply	other threads:[~2023-10-17 23:15 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-09-26 22:02 [PATCH] " Peter Bergner
2023-09-27 16:03 ` Adhemerval Zanella Netto
2023-10-02 21:19   ` Peter Bergner
2023-10-03 14:08     ` Adhemerval Zanella Netto
2023-10-03 22:12       ` Peter Bergner
2023-10-04 11:02         ` Adhemerval Zanella Netto
2023-10-17 23:14 ` Peter Bergner [this message]
2023-10-18 16:22   ` [PING][PATCH] " Szabolcs Nagy

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