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From: Martijn Coenen <maco@android.com>
To: linux-kernel@vger.kernel.org
Cc: Martijn Coenen <maco@android.com>,
	Masahiro Yamada <yamada.masahiro@socionext.com>,
	Michal Marek <michal.lkml@markovi.net>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	x86@kernel.org, Alan Stern <stern@rowland.harvard.edu>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Oliver Neukum <oneukum@suse.com>, Arnd Bergmann <arnd@arndb.de>,
	Jessica Yu <jeyu@kernel.org>, Stephen Boyd <sboyd@codeaurora.org>,
	Philippe Ombredanne <pombredanne@nexb.com>,
	Kate Stewart <kstewart@linuxfoundation.org>,
	Sam Ravnborg <sam@ravnborg.org>,
	linux-kbuild@vger.kernel.org, linux-m68k@lists.linux-m68k.org,
	linux-usb@vger.kernel.org, usb-storage@lists.one-eyed-alien.net,
	linux-scsi@vger.kernel.org, linux-arch@vger.kernel.org,
	maco@google.com, sspatil@google.com, malchev@google.com,
	joelaf@google.com
Subject: [PATCH 1/6] export: explicitly align struct kernel_symbol.
Date: Mon, 16 Jul 2018 14:21:20 +0200
Message-ID: <20180716122125.175792-2-maco@android.com> (raw)
In-Reply-To: <20180716122125.175792-1-maco@android.com>

This change allows growing struct kernel_symbol without wasting bytes to
alignment.

struct kernel_symbol was already implicitly being aligned to the word
size, except on x86_64 and m68k, where it is aligned to 16 and 2 bytes,
respectively.

As far as I can tell there is no requirement for aligning struct
kernel_symbol to 16 bytes on x86_64, but gcc aligns structs to their
size, and the linker aligns the custom __ksymtab sections to the largest
data type contained within, so setting KSYM_ALIGN to 16 was necessary to
stay consistent with the code generated for non-ASM EXPORT_SYMBOL(). Now
that non-ASM EXPORT_SYMBOL() explicitly aligns to word size (8),
KSYM_ALIGN is no longer necessary.

As for m68k, struct kernel_symbol is aligned to 2 bytes even though the
structure itself is 8 bytes; using a 4-byte alignment shouldn't hurt.

I manually verified the output of the __ksymtab sections didn't change
on x86, x86_64, arm, arm64 and m68k. As expected, the section contents
didn't change, and the ELF section alignment only changed on x86_64 and
m68k. Feedback from other archs more than welcome.

Signed-off-by: Martijn Coenen <maco@android.com>
---
 arch/m68k/include/asm/export.h | 1 -
 arch/x86/include/asm/Kbuild    | 1 +
 arch/x86/include/asm/export.h  | 5 -----
 include/linux/export.h         | 1 +
 4 files changed, 2 insertions(+), 6 deletions(-)
 delete mode 100644 arch/x86/include/asm/export.h

diff --git a/arch/m68k/include/asm/export.h b/arch/m68k/include/asm/export.h
index 0af20f48bd07..b53008b67ce1 100644
--- a/arch/m68k/include/asm/export.h
+++ b/arch/m68k/include/asm/export.h
@@ -1,3 +1,2 @@
-#define KSYM_ALIGN 2
 #define KCRC_ALIGN 2
 #include <asm-generic/export.h>
diff --git a/arch/x86/include/asm/Kbuild b/arch/x86/include/asm/Kbuild
index de690c2d2e33..a0ab9ab61c75 100644
--- a/arch/x86/include/asm/Kbuild
+++ b/arch/x86/include/asm/Kbuild
@@ -8,5 +8,6 @@ generated-y += xen-hypercalls.h
 
 generic-y += dma-contiguous.h
 generic-y += early_ioremap.h
+generic-y += export.h
 generic-y += mcs_spinlock.h
 generic-y += mm-arch-hooks.h
diff --git a/arch/x86/include/asm/export.h b/arch/x86/include/asm/export.h
deleted file mode 100644
index 2a51d66689c5..000000000000
--- a/arch/x86/include/asm/export.h
+++ /dev/null
@@ -1,5 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-#ifdef CONFIG_64BIT
-#define KSYM_ALIGN 16
-#endif
-#include <asm-generic/export.h>
diff --git a/include/linux/export.h b/include/linux/export.h
index b768d6dd3c90..ad6b8e697b27 100644
--- a/include/linux/export.h
+++ b/include/linux/export.h
@@ -64,6 +64,7 @@ extern struct module __this_module;
 	static const struct kernel_symbol __ksymtab_##sym		\
 	__used								\
 	__attribute__((section("___ksymtab" sec "+" #sym), used))	\
+	__attribute__((aligned(sizeof(void *))))                        \
 	= { (unsigned long)&sym, __kstrtab_##sym }
 
 #if defined(__KSYM_DEPS__)
-- 
2.18.0.203.gfac676dfb9-goog


  reply index

Thread overview: 134+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-16 12:21 [PATCH 0/6] Symbol namespaces Martijn Coenen
2018-07-16 12:21 ` Martijn Coenen [this message]
2018-07-16 12:21 ` [PATCH 2/6] module: add support for symbol namespaces Martijn Coenen
2018-07-19 16:32   ` Jessica Yu
2018-07-20  7:54     ` Martijn Coenen
2018-07-20 14:49       ` Jessica Yu
2018-07-20 15:42         ` Martijn Coenen
2018-07-23 11:12           ` Jessica Yu
2018-07-24  7:44             ` Martijn Coenen
2018-07-24  7:56   ` Martijn Coenen
2018-07-25 15:55     ` Jessica Yu
2018-07-25 16:48       ` Lucas De Marchi
2018-07-26  7:44         ` Martijn Coenen
2018-07-16 12:21 ` [PATCH 3/6] modpost: add support for checking " Martijn Coenen
2018-07-16 12:21 ` [PATCH 4/6] modpost: add support for generating namespace dependencies Martijn Coenen
2018-07-23  6:49   ` Jessica Yu
2018-07-16 12:21 ` [PATCH 5/6] scripts: Coccinelle script for " Martijn Coenen
2018-07-16 12:21 ` [PATCH 6/6] RFC: USB: storage: move symbols into USB_STORAGE namespace Martijn Coenen
2018-07-17 15:04   ` Alan Stern
2018-07-18 13:28     ` Martijn Coenen
2018-07-16 15:33 ` [PATCH 0/6] Symbol namespaces Greg Kroah-Hartman
2018-07-23 14:28 ` Arnd Bergmann
2018-07-24  8:09   ` Martijn Coenen
2018-07-24  9:08     ` Arnd Bergmann
2019-08-13 12:16 ` [PATCH v2 0/10] Symbol namespaces - RFC Matthias Maennich
2019-08-13 12:16   ` [PATCH v2 01/10] module: support reading multiple values per modinfo tag Matthias Maennich
2019-08-13 12:40     ` Greg KH
2019-08-13 12:16   ` [PATCH v2 02/10] export: explicitly align struct kernel_symbol Matthias Maennich
2019-08-13 12:41     ` Greg KH
2019-08-13 12:17   ` [PATCH v2 03/10] module: add support for symbol namespaces Matthias Maennich
2019-08-13 15:26     ` Greg KH
2019-08-13 12:17   ` [PATCH v2 04/10] modpost: " Matthias Maennich
2019-08-13 15:27     ` Greg KH
2019-08-13 12:17   ` [PATCH v2 05/10] module: add config option MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS Matthias Maennich
2019-08-13 18:17     ` Greg KH
2019-08-13 20:15     ` Saravana Kannan
2019-08-14 12:54       ` Matthias Maennich
2019-08-14 17:34         ` Saravana Kannan
2019-08-13 12:17   ` [PATCH v2 06/10] export: allow definition default namespaces in Makefiles or sources Matthias Maennich
2019-08-13 18:16     ` Greg KH
2019-08-13 18:16     ` Greg KH
2019-08-13 12:17   ` [PATCH v2 07/10] modpost: add support for generating namespace dependencies Matthias Maennich
2019-08-13 18:21     ` Greg KH
2019-08-13 12:17   ` [PATCH v2 08/10] scripts: Coccinelle script for " Matthias Maennich
2019-08-13 12:31     ` Julia Lawall
2019-08-13 12:44     ` Greg KH
2019-08-14  6:36     ` [Cocci] " Himanshu Jha
2019-08-14  8:03       ` Matthias Maennich
2019-08-15 13:50     ` [v2 " Markus Elfring
2019-08-22  9:18       ` Matthias Maennich
2019-08-22 11:00         ` Markus Elfring
2019-08-13 12:17   ` [PATCH v2 09/10] usb-storage: remove single-use define for debugging Matthias Maennich
2019-08-13 12:42     ` Greg KH
2019-08-13 13:12       ` Greg KH
2019-08-13 12:17   ` [PATCH v2 10/10] RFC: usb-storage: export symbols in USB_STORAGE namespace Matthias Maennich
2019-08-13 12:45     ` Greg KH
2019-08-13 12:47     ` Greg KH
2019-08-13 15:02       ` Matthias Maennich
     [not found]   ` <20190821114955.12788-1-maennich@google.com>
2019-08-21 11:49     ` [PATCH v3 01/11] module: support reading multiple values per modinfo tag Matthias Maennich
2019-08-21 11:49     ` [PATCH v3 02/11] export: explicitly align struct kernel_symbol Matthias Maennich
2019-08-21 11:49     ` [PATCH v3 03/11] module: add support for symbol namespaces Matthias Maennich
2019-08-27 15:37       ` Jessica Yu
2019-08-27 16:04         ` Matthias Maennich
2019-08-21 11:49     ` [PATCH v3 04/11] modpost: " Matthias Maennich
2019-08-26 16:21       ` Jessica Yu
2019-08-27 14:41         ` Matthias Maennich
2019-08-28  9:43           ` Jessica Yu
2019-08-28  9:55             ` Matthias Maennich
2019-08-28 10:16               ` Jessica Yu
2019-08-21 11:49     ` [PATCH v3 05/11] module: add config option MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS Matthias Maennich
2019-08-21 11:49     ` [PATCH v3 06/11] export: allow definition default namespaces in Makefiles or sources Matthias Maennich
2019-08-28 10:49       ` Jessica Yu
2019-08-28 10:56         ` Matthias Maennich
2019-08-21 11:49     ` [PATCH v3 07/11] modpost: add support for generating namespace dependencies Matthias Maennich
2019-08-21 11:49     ` [PATCH v3 08/11] scripts: Coccinelle script for " Matthias Maennich
2019-08-22  6:09       ` [v3 " Markus Elfring
2019-08-29 12:13       ` [PATCH v3 " Jessica Yu
2019-08-21 11:49     ` [PATCH v3 09/11] usb-storage: remove single-use define for debugging Matthias Maennich
2019-08-21 12:37       ` Greg KH
2019-08-21 13:21       ` Thomas Gleixner
2019-08-21 13:32         ` Greg KH
2019-08-21 11:49     ` [PATCH v3 10/11] RFC: usb-storage: export symbols in USB_STORAGE namespace Matthias Maennich
2019-08-21 12:38       ` Greg KH
2019-08-21 14:36         ` Jessica Yu
2019-08-21 23:13       ` Christoph Hellwig
2019-08-22  8:32         ` Matthias Maennich
2019-09-03 15:06 ` [PATCH v4 00/12] Symbol Namespaces Matthias Maennich
2019-09-03 15:06   ` [PATCH v4 01/12] module: support reading multiple values per modinfo tag Matthias Maennich
2019-09-03 15:06   ` [PATCH v4 02/12] export: explicitly align struct kernel_symbol Matthias Maennich
2019-09-03 15:06   ` [PATCH v4 03/12] module: add support for symbol namespaces Matthias Maennich
2019-09-03 15:06   ` [PATCH v4 04/12] modpost: " Matthias Maennich
2019-09-03 15:06   ` [PATCH v4 05/12] module: add config option MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS Matthias Maennich
2019-09-03 15:06   ` [PATCH v4 06/12] export: allow definition default namespaces in Makefiles or sources Matthias Maennich
2019-09-03 15:06   ` [PATCH v4 07/12] modpost: add support for generating namespace dependencies Matthias Maennich
2019-09-03 15:06   ` [PATCH v4 08/12] scripts: Coccinelle script for " Matthias Maennich
2019-09-04  9:53     ` Masahiro Yamada
2019-09-05 14:46       ` Matthias Maennich
2019-09-03 15:06   ` [PATCH v4 09/12] docs: Add documentation for Symbol Namespaces Matthias Maennich
2019-09-04  7:16     ` Greg KH
2019-09-03 15:06   ` [PATCH v4 10/12] usb-storage: remove single-use define for debugging Matthias Maennich
2019-09-03 15:06   ` [PATCH v4 11/12] RFC: usb-storage: export symbols in USB_STORAGE namespace Matthias Maennich
2019-09-03 15:06   ` [PATCH v4 12/12] RFC: watchdog: export core symbols in WATCHDOG_CORE namespace Matthias Maennich
2019-09-03 16:10     ` Guenter Roeck
2019-09-04  8:45       ` Masahiro Yamada
2019-09-04 12:12         ` Guenter Roeck
2019-09-04 16:16           ` [usb-storage] " Matthew Dharm
2019-09-05 10:41             ` Jessica Yu
2019-09-05 10:52               ` Arnd Bergmann
2019-09-05 11:16                 ` Jessica Yu
2019-09-05 11:25                   ` Masahiro Yamada
2019-09-05 12:00                     ` Greg Kroah-Hartman
2019-09-05 11:25               ` Matthias Maennich
2019-09-04  9:37   ` [PATCH v4 00/12] Symbol Namespaces Masahiro Yamada
2019-09-06 10:32 ` [PATCH v5 00/11] " Matthias Maennich
2019-09-06 10:32   ` [PATCH v5 01/11] module: support reading multiple values per modinfo tag Matthias Maennich
2019-09-06 10:32   ` [PATCH v5 02/11] export: explicitly align struct kernel_symbol Matthias Maennich
2019-09-06 10:32   ` [PATCH v5 03/11] module: add support for symbol namespaces Matthias Maennich
2019-09-06 10:32   ` [PATCH v5 04/11] modpost: " Matthias Maennich
2019-09-26 22:24     ` [PATCH] modpost: Copy namespace string into 'struct symbol' Shaun Ruffell
2019-09-27  5:31       ` Greg Kroah-Hartman
2019-09-27  8:03       ` Matthias Maennich
2019-09-30 21:20         ` Shaun Ruffell
2019-10-01 16:19           ` Matthias Maennich
2019-10-01 19:37             ` Shaun Ruffell
2019-09-06 10:32   ` [PATCH v5 05/11] module: add config option MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS Matthias Maennich
2019-09-06 10:32   ` [PATCH v5 06/11] export: allow definition default namespaces in Makefiles or sources Matthias Maennich
2019-09-06 10:32   ` [PATCH v5 07/11] modpost: add support for generating namespace dependencies Matthias Maennich
2019-09-06 10:32   ` [PATCH v5 08/11] scripts: Coccinelle script for " Matthias Maennich
2019-09-06 10:32   ` [PATCH v5 09/11] docs: Add documentation for Symbol Namespaces Matthias Maennich
2019-09-06 10:32   ` [PATCH v5 10/11] usb-storage: remove single-use define for debugging Matthias Maennich
2019-09-06 12:59     ` Jessica Yu
2019-09-06 13:22       ` Greg KH
2019-09-06 10:32   ` [PATCH v5 11/11] usb-storage: export symbols in USB_STORAGE namespace Matthias Maennich
2019-09-09  8:35   ` [PATCH v5 00/11] Symbol Namespaces Jessica Yu

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