From: Roger Pau Monne <roger.pau@citrix.com>
To: xen-devel@lists.xenproject.org
Cc: Roger Pau Monne <roger.pau@citrix.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
George Dunlap <george.dunlap@citrix.com>,
Jan Beulich <jbeulich@suse.com>, Julien Grall <julien@xen.org>,
Stefano Stabellini <sstabellini@kernel.org>, Wei Liu <wl@xen.org>
Subject: [PATCH v6 2/3] xen: use explicit function alignment if supported by compiler
Date: Wed, 7 Feb 2024 15:55:46 +0100 [thread overview]
Message-ID: <20240207145547.89689-3-roger.pau@citrix.com> (raw)
In-Reply-To: <20240207145547.89689-1-roger.pau@citrix.com>
Introduce a new Kconfig check for whether the compiler supports
-falign-functions and if supported use it to align functions to the per-arch
selected value, just like it's done for assembly ENTRY() and FUNC() symbols.
Note that it's possible for the compiler to end up using a higher function
alignment regardless of the passed value. Different compilers handle the
option differently, as clang will ignore -falign-functions value if it's
smaller than the one that would be set by the optimization level, while gcc
seems to always honor the function alignment passed in -falign-functions.
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
---
Changes since v5:
- New in this version.
---
xen/Kconfig | 5 +++++
xen/Makefile | 1 +
2 files changed, 6 insertions(+)
diff --git a/xen/Kconfig b/xen/Kconfig
index 1e1b041fd52f..040cba1b4b73 100644
--- a/xen/Kconfig
+++ b/xen/Kconfig
@@ -41,6 +41,11 @@ config CC_SPLIT_SECTIONS
#
# Allow setting on a boolean basis, and then convert such selection to an
# integer for the build system and code to consume more easily.
+#
+# Requires clang >= 7.0.0
+config CC_HAS_FUNCTION_ALIGNMENT
+ def_bool $(cc-option,-falign-functions)
+
config FUNCTION_ALIGNMENT_4B
bool
config FUNCTION_ALIGNMENT_8B
diff --git a/xen/Makefile b/xen/Makefile
index 21832d640225..7c8249ab3a33 100644
--- a/xen/Makefile
+++ b/xen/Makefile
@@ -390,6 +390,7 @@ CFLAGS += -fomit-frame-pointer
endif
CFLAGS-$(CONFIG_CC_SPLIT_SECTIONS) += -ffunction-sections -fdata-sections
+CFLAGS-$(CONFIG_CC_HAS_FUNCTION_ALIGNMENT) += -falign-functions=$(CONFIG_FUNCTION_ALIGNMENT)
CFLAGS += -nostdinc -fno-builtin -fno-common
CFLAGS += -Werror -Wredundant-decls -Wwrite-strings -Wno-pointer-arith
--
2.43.0
next prev parent reply other threads:[~2024-02-07 14:56 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-07 14:55 [PATCH v6 0/3] xen: introduce Kconfig function alignment option Roger Pau Monne
2024-02-07 14:55 ` [PATCH v6 1/3] " Roger Pau Monne
2024-02-13 15:51 ` Jan Beulich
2024-02-26 11:33 ` Roger Pau Monné
2024-02-26 12:26 ` Jan Beulich
2024-02-14 8:20 ` Michal Orzel
2024-02-26 19:35 ` Shawn Anastasio
2024-02-07 14:55 ` Roger Pau Monne [this message]
2024-03-28 9:44 ` [PATCH v6 2/3] xen: use explicit function alignment if supported by compiler Roger Pau Monné
2024-02-07 14:55 ` [PATCH v6 3/3] xen/livepatch: align functions to ensure minimal distance between entry points Roger Pau Monne
2024-02-13 15:58 ` Jan Beulich
2024-02-26 11:32 ` Roger Pau Monné
2024-02-26 12:36 ` Jan Beulich
2024-02-27 8:15 ` Roger Pau Monné
2024-02-27 8:53 ` Jan Beulich
2024-02-27 9:25 ` Roger Pau Monné
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