Linux-Modules Archive on lore.kernel.org
 help / color / Atom feed
From: Matthias Maennich <maennich@google.com>
To: linux-kernel@vger.kernel.org
Cc: kernel-team@android.com, maennich@google.com,
	Jessica Yu <jeyu@kernel.org>,
	Masahiro Yamada <yamada.masahiro@socionext.com>,
	Martijn Coenen <maco@android.com>,
	Lucas De Marchi <lucas.de.marchi@gmail.com>,
	Shaun Ruffell <sruffell@sruffell.net>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Will Deacon <will@kernel.org>,
	linux-kbuild@vger.kernel.org, linux-modules@vger.kernel.org
Subject: [PATCH 4/4] export: avoid code duplication in include/linux/export.h
Date: Thu, 10 Oct 2019 16:14:43 +0100
Message-ID: <20191010151443.7399-5-maennich@google.com> (raw)
In-Reply-To: <20191010151443.7399-1-maennich@google.com>

Now that the namespace value is not part of the __ksymtab entry name
anymore, we can simplify the implementation of EXPORT_SYMBOL*. By
allowing the empty string "" to represent 'no namespace', we can unify
the implementation and drop a lot redundant code.  That increases
readability and maintainability.

As Masahiro pointed out earlier,
"The drawback of this change is, it grows the code size. When the symbol
has no namespace, sym->namespace was previously NULL, but it is now am
empty string "". So, it increases 1 byte for every no namespace
EXPORT_SYMBOL. A typical kernel configuration has 10K exported symbols,
so it increases 10KB in rough estimation."

Suggested-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Matthias Maennich <maennich@google.com>
---
 include/linux/export.h | 92 +++++++++++++-----------------------------
 kernel/module.c        |  2 +-
 2 files changed, 29 insertions(+), 65 deletions(-)

diff --git a/include/linux/export.h b/include/linux/export.h
index f24b86d7dd4d..201262793369 100644
--- a/include/linux/export.h
+++ b/include/linux/export.h
@@ -46,7 +46,7 @@ extern struct module __this_module;
  * absolute relocations that require runtime processing on relocatable
  * kernels.
  */
-#define __KSYMTAB_ENTRY_NS(sym, sec)					\
+#define __KSYMTAB_ENTRY(sym, sec)					\
 	__ADDRESSABLE(sym)						\
 	asm("	.section \"___ksymtab" sec "+" #sym "\", \"a\"	\n"	\
 	    "	.balign	4					\n"	\
@@ -56,34 +56,17 @@ extern struct module __this_module;
 	    "	.long	__kstrtabns_" #sym "- .			\n"	\
 	    "	.previous					\n")
 
-#define __KSYMTAB_ENTRY(sym, sec)					\
-	__ADDRESSABLE(sym)						\
-	asm("	.section \"___ksymtab" sec "+" #sym "\", \"a\"	\n"	\
-	    "	.balign 4					\n"	\
-	    "__ksymtab_" #sym ":				\n"	\
-	    "	.long	" #sym "- .				\n"	\
-	    "	.long	__kstrtab_" #sym "- .			\n"	\
-	    "	.long	0					\n"	\
-	    "	.previous					\n")
-
 struct kernel_symbol {
 	int value_offset;
 	int name_offset;
 	int namespace_offset;
 };
 #else
-#define __KSYMTAB_ENTRY_NS(sym, sec)					\
-	static const struct kernel_symbol __ksymtab_##sym		\
-	__attribute__((section("___ksymtab" sec "+" #sym), used))	\
-	__aligned(sizeof(void *))					\
-	= { (unsigned long)&sym, __kstrtab_##sym, __kstrtabns_##sym }
-
 #define __KSYMTAB_ENTRY(sym, sec)					\
 	static const struct kernel_symbol __ksymtab_##sym		\
-	asm("__ksymtab_" #sym)						\
 	__attribute__((section("___ksymtab" sec "+" #sym), used))	\
 	__aligned(sizeof(void *))					\
-	= { (unsigned long)&sym, __kstrtab_##sym, NULL }
+	= { (unsigned long)&sym, __kstrtab_##sym, __kstrtabns_##sym }
 
 struct kernel_symbol {
 	unsigned long value;
@@ -94,28 +77,20 @@ struct kernel_symbol {
 
 #ifdef __GENKSYMS__
 
-#define ___EXPORT_SYMBOL(sym,sec)	__GENKSYMS_EXPORT_SYMBOL(sym)
-#define ___EXPORT_SYMBOL_NS(sym,sec,ns)	__GENKSYMS_EXPORT_SYMBOL(sym)
+#define ___EXPORT_SYMBOL(sym, sec, ns)	__GENKSYMS_EXPORT_SYMBOL(sym)
 
 #else
 
-#define ___export_symbol_common(sym, sec)				\
+/* For every exported symbol, place a struct in the __ksymtab section */
+#define ___EXPORT_SYMBOL(sym, sec, ns)					\
 	extern typeof(sym) sym;						\
 	__CRC_SYMBOL(sym, sec);						\
 	static const char __kstrtab_##sym[]				\
 	__attribute__((section("__ksymtab_strings"), used, aligned(1)))	\
-	= #sym								\
-
-/* For every exported symbol, place a struct in the __ksymtab section */
-#define ___EXPORT_SYMBOL_NS(sym, sec, ns)				\
-	___export_symbol_common(sym, sec);				\
+	= #sym;								\
 	static const char __kstrtabns_##sym[]				\
 	__attribute__((section("__ksymtab_strings"), used, aligned(1)))	\
-	= #ns;								\
-	__KSYMTAB_ENTRY_NS(sym, sec)
-
-#define ___EXPORT_SYMBOL(sym, sec)					\
-	___export_symbol_common(sym, sec);				\
+	= ns;								\
 	__KSYMTAB_ENTRY(sym, sec)
 
 #endif
@@ -127,8 +102,7 @@ struct kernel_symbol {
  * be reused in other execution contexts such as the UEFI stub or the
  * decompressor.
  */
-#define __EXPORT_SYMBOL_NS(sym, sec, ns)
-#define __EXPORT_SYMBOL(sym, sec)
+#define __EXPORT_SYMBOL(sym, sec, ns)
 
 #elif defined(CONFIG_TRIM_UNUSED_KSYMS)
 
@@ -144,48 +118,38 @@ struct kernel_symbol {
 #define __ksym_marker(sym)	\
 	static int __ksym_marker_##sym[0] __section(".discard.ksym") __used
 
-#define __EXPORT_SYMBOL(sym, sec)				\
-	__ksym_marker(sym);					\
-	__cond_export_sym(sym, sec, __is_defined(__KSYM_##sym))
-#define __cond_export_sym(sym, sec, conf)			\
-	___cond_export_sym(sym, sec, conf)
-#define ___cond_export_sym(sym, sec, enabled)			\
-	__cond_export_sym_##enabled(sym, sec)
-#define __cond_export_sym_1(sym, sec) ___EXPORT_SYMBOL(sym, sec)
-#define __cond_export_sym_0(sym, sec) /* nothing */
-
-#define __EXPORT_SYMBOL_NS(sym, sec, ns)				\
+#define __EXPORT_SYMBOL(sym, sec, ns)					\
 	__ksym_marker(sym);						\
-	__cond_export_ns_sym(sym, sec, ns, __is_defined(__KSYM_##sym))
-#define __cond_export_ns_sym(sym, sec, ns, conf)			\
-	___cond_export_ns_sym(sym, sec, ns, conf)
-#define ___cond_export_ns_sym(sym, sec, ns, enabled)			\
-	__cond_export_ns_sym_##enabled(sym, sec, ns)
-#define __cond_export_ns_sym_1(sym, sec, ns) ___EXPORT_SYMBOL_NS(sym, sec, ns)
-#define __cond_export_ns_sym_0(sym, sec, ns) /* nothing */
+	__cond_export_sym(sym, sec, ns, __is_defined(__KSYM_##sym))
+#define __cond_export_sym(sym, sec, ns, conf)				\
+	___cond_export_sym(sym, sec, ns, conf)
+#define ___cond_export_sym(sym, sec, ns, enabled)			\
+	__cond_export_sym_##enabled(sym, sec, ns)
+#define __cond_export_sym_1(sym, sec, ns) ___EXPORT_SYMBOL(sym, sec, ns)
+#define __cond_export_sym_0(sym, sec, ns) /* nothing */
 
 #else
 
-#define __EXPORT_SYMBOL_NS(sym,sec,ns)	___EXPORT_SYMBOL_NS(sym,sec,ns)
-#define __EXPORT_SYMBOL(sym,sec)	___EXPORT_SYMBOL(sym,sec)
+#define __EXPORT_SYMBOL(sym, sec, ns)	___EXPORT_SYMBOL(sym, sec, ns)
 
 #endif /* CONFIG_MODULES */
 
 #ifdef DEFAULT_SYMBOL_NAMESPACE
-#undef __EXPORT_SYMBOL
-#define __EXPORT_SYMBOL(sym, sec)				\
-	__EXPORT_SYMBOL_NS(sym, sec, DEFAULT_SYMBOL_NAMESPACE)
+#include <linux/stringify.h>
+#define _EXPORT_SYMBOL(sym, sec)	__EXPORT_SYMBOL(sym, sec, __stringify(DEFAULT_SYMBOL_NAMESPACE))
+#else
+#define _EXPORT_SYMBOL(sym, sec)	__EXPORT_SYMBOL(sym, sec, "")
 #endif
 
-#define EXPORT_SYMBOL(sym)		__EXPORT_SYMBOL(sym, "")
-#define EXPORT_SYMBOL_GPL(sym)		__EXPORT_SYMBOL(sym, "_gpl")
-#define EXPORT_SYMBOL_GPL_FUTURE(sym)	__EXPORT_SYMBOL(sym, "_gpl_future")
-#define EXPORT_SYMBOL_NS(sym, ns)	__EXPORT_SYMBOL_NS(sym, "", ns)
-#define EXPORT_SYMBOL_NS_GPL(sym, ns)	__EXPORT_SYMBOL_NS(sym, "_gpl", ns)
+#define EXPORT_SYMBOL(sym)		_EXPORT_SYMBOL(sym, "")
+#define EXPORT_SYMBOL_GPL(sym)		_EXPORT_SYMBOL(sym, "_gpl")
+#define EXPORT_SYMBOL_GPL_FUTURE(sym)	_EXPORT_SYMBOL(sym, "_gpl_future")
+#define EXPORT_SYMBOL_NS(sym, ns)	__EXPORT_SYMBOL(sym, "", #ns)
+#define EXPORT_SYMBOL_NS_GPL(sym, ns)	__EXPORT_SYMBOL(sym, "_gpl", #ns)
 
 #ifdef CONFIG_UNUSED_SYMBOLS
-#define EXPORT_UNUSED_SYMBOL(sym)	__EXPORT_SYMBOL(sym, "_unused")
-#define EXPORT_UNUSED_SYMBOL_GPL(sym)	__EXPORT_SYMBOL(sym, "_unused_gpl")
+#define EXPORT_UNUSED_SYMBOL(sym)	_EXPORT_SYMBOL(sym, "_unused")
+#define EXPORT_UNUSED_SYMBOL_GPL(sym)	_EXPORT_SYMBOL(sym, "_unused_gpl")
 #else
 #define EXPORT_UNUSED_SYMBOL(sym)
 #define EXPORT_UNUSED_SYMBOL_GPL(sym)
diff --git a/kernel/module.c b/kernel/module.c
index ff2d7359a418..26c13173da3d 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -1400,7 +1400,7 @@ static int verify_namespace_is_imported(const struct load_info *info,
 	char *imported_namespace;
 
 	namespace = kernel_symbol_namespace(sym);
-	if (namespace) {
+	if (namespace && namespace[0]) {
 		imported_namespace = get_modinfo(info, "import_ns");
 		while (imported_namespace) {
 			if (strcmp(namespace, imported_namespace) == 0)
-- 
2.23.0.581.g78d2f28ef7-goog


  parent reply index

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-10 15:14 [PATCH 0/4] export/modpost: avoid renaming __ksymtab entries for symbol namespaces Matthias Maennich
2019-10-10 15:14 ` [PATCH 1/4] modpost: delegate updating namespaces to separate function Matthias Maennich
2019-10-11 14:24   ` Will Deacon
2019-10-11 15:32   ` Greg Kroah-Hartman
2019-10-12  3:19     ` Masahiro Yamada
2019-10-10 15:14 ` [PATCH 2/4] modpost: make updating the symbol namespace explict Matthias Maennich
2019-10-11 14:24   ` Will Deacon
2019-10-11 15:33   ` Greg Kroah-Hartman
2019-10-12  3:22   ` Masahiro Yamada
2019-10-10 15:14 ` [PATCH 3/4] symbol namespaces: revert to previous __ksymtab name scheme Matthias Maennich
2019-10-11 14:24   ` Will Deacon
2019-10-11 15:33   ` Greg Kroah-Hartman
2019-10-12  3:35   ` Masahiro Yamada
2019-10-10 15:14 ` Matthias Maennich [this message]
2019-10-11 15:31   ` [PATCH 4/4] export: avoid code duplication in include/linux/export.h Greg Kroah-Hartman
2019-10-11 15:43     ` Matthias Maennich
2019-10-12  4:25       ` Masahiro Yamada
2019-10-18  9:31 ` [PATCH v2 0/4] export/modpost: avoid renaming __ksymtab entries for symbol namespaces Matthias Maennich
2019-10-18  9:31   ` [PATCH v2 1/4] modpost: delegate updating namespaces to separate function Matthias Maennich
2019-10-18  9:31   ` [PATCH v2 2/4] modpost: make updating the symbol namespace explicit Matthias Maennich
2019-10-18  9:31   ` [PATCH v2 3/4] symbol namespaces: revert to previous __ksymtab name scheme Matthias Maennich
2019-10-18  9:31   ` [PATCH v2 4/4] export: avoid code duplication in include/linux/export.h Matthias Maennich
2019-10-21 13:31   ` [PATCH v2 0/4] export/modpost: avoid renaming __ksymtab entries for symbol namespaces Jessica Yu
2019-10-23 12:22   ` Luis Chamberlain
2019-10-24  9:35     ` Matthias Maennich
2019-10-24 10:24       ` Luis Chamberlain

Reply instructions:

You may reply publically 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=20191010151443.7399-5-maennich@google.com \
    --to=maennich@google.com \
    --cc=gregkh@linuxfoundation.org \
    --cc=jeyu@kernel.org \
    --cc=kernel-team@android.com \
    --cc=linux-kbuild@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-modules@vger.kernel.org \
    --cc=lucas.de.marchi@gmail.com \
    --cc=maco@android.com \
    --cc=sruffell@sruffell.net \
    --cc=will@kernel.org \
    --cc=yamada.masahiro@socionext.com \
    /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

Linux-Modules Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-modules/0 linux-modules/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-modules linux-modules/ https://lore.kernel.org/linux-modules \
		linux-modules@vger.kernel.org
	public-inbox-index linux-modules

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-modules


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git