From: Ian Rogers <irogers@google.com>
To: Eric Biggers <ebiggers@google.com>,
Yuzhuo Jing <yuzhuo@google.com>,
Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
Arnaldo Carvalho de Melo <acme@redhat.com>,
Al Viro <viro@zeniv.linux.org.uk>,
Christophe Leroy <christophe.leroy@csgroup.eu>,
"Jason A. Donenfeld" <Jason@zx2c4.com>,
linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org
Cc: Ian Rogers <irogers@google.com>
Subject: [PATCH v2 0/3] Switch get/put unaligned to use memcpy
Date: Tue, 17 Jun 2025 13:53:17 -0700 [thread overview]
Message-ID: <20250617205320.1580946-1-irogers@google.com> (raw)
The existing type punning approach with packed structs requires
-fno-strict-aliasing to be passed to the compiler for
correctness. This is true in the kernel tree but not in the tools
directory resulting in this suggested patch from Eric Biggers
<ebiggers@google.com>:
https://lore.kernel.org/lkml/20250614044133.660848-2-ebiggers@kernel.org/
Requiring -fno-strict-aliasing seems unfortunate and so this patch
makes the unaligned code work via memcpy for type punning rather than
the packed attribute.
v2: switch memcpy to __builtin_memcpy to avoid potential/disallowed
memcpy calls in vdso caused by -fno-builtin. Reported by
Christophe Leroy <christophe.leroy@csgroup.eu>:
https://lore.kernel.org/lkml/c57de5bf-d55c-48c5-9dfa-e2fb844dafe9@csgroup.eu/
Ian Rogers (3):
vdso: Switch get/put unaligned from packed struct to memcpy
tools headers: Update the linux/unaligned.h copy with the kernel
sources
tools headers: Remove unneeded ignoring of warnings in unaligned.h
include/vdso/unaligned.h | 48 ++++++++++++++++++++++++++++-----
tools/include/linux/unaligned.h | 4 ---
tools/include/vdso/unaligned.h | 48 ++++++++++++++++++++++++++++-----
3 files changed, 84 insertions(+), 16 deletions(-)
--
2.50.0.rc2.701.gf1e915cc24-goog
next reply other threads:[~2025-06-17 20:54 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-06-17 20:53 Ian Rogers [this message]
2025-06-17 20:53 ` [PATCH v2 1/3] vdso: Switch get/put unaligned from packed struct to memcpy Ian Rogers
2025-06-18 11:40 ` Christophe Leroy
2025-06-18 13:14 ` kernel test robot
2025-06-20 13:34 ` David Laight
2025-06-17 20:53 ` [PATCH v2 2/3] tools headers: Update the linux/unaligned.h copy with the kernel sources Ian Rogers
2025-06-17 20:53 ` [PATCH v2 3/3] tools headers: Remove unneeded ignoring of warnings in unaligned.h Ian Rogers
2025-06-18 11:42 ` [PATCH v2 0/3] Switch get/put unaligned to use memcpy Christophe Leroy
2025-06-25 18:06 ` Ian Rogers
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