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>
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: [PATCH] uapi/auxvec: Define AT_HWCAP3 and AT_HWCAP4 aux vector, entries
Date: Tue, 26 Sep 2023 17:02:25 -0500 [thread overview]
Message-ID: <fd879f60-3f0b-48d1-bfa1-6d337768207e@linux.ibm.com> (raw)
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 */
--
2.39.3
next reply other threads:[~2023-09-26 23:43 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-26 22:02 Peter Bergner [this message]
2023-09-27 16:03 ` [PATCH] uapi/auxvec: Define AT_HWCAP3 and AT_HWCAP4 aux vector, entries 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 ` [PING][PATCH] " Peter Bergner
2023-10-18 16:22 ` Szabolcs Nagy
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=fd879f60-3f0b-48d1-bfa1-6d337768207e@linux.ibm.com \
--to=bergner@linux.ibm.com \
--cc=libc-alpha@sourceware.org \
--cc=linux-api@vger.kernel.org \
--cc=linux-arch@vger.kernel.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=mpe@ellerman.id.au \
--cc=npiggin@gmail.com \
--cc=segher@kernel.crashing.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).