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Date:   Thu, 22 Apr 2021 11:25:45 -0700
Message-Id: <20210422182545.726897-1-manojgupta@google.com>
Mime-Version: 1.0
Subject: [PATCH] iw: set retain atrribute on sections
From:   Manoj Gupta <manojgupta@google.com>
To:     Johannes Berg <johannes@sipsolutions.net>
Cc:     stable@vger.kernel.org, maskray@google.com, llozano@google.com,
        manojgupta@google.com, linux-wireless@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

LLD 13 and GNU ld 2.37 support -z start-stop-gc which allows garbage
collection of C identifier name sections despite the __start_/__stop_
references.  Simply set the retain attribute so that GCC 11 (if
configure-time binutils is 2.36 or newer)/Clang 13 will set the
SHF_GNU_RETAIN section attribute to prevent garbage collection.

Without the patch, there are linker errors like the following with -z
start-stop-gc:
ld.lld: error: undefined symbol: __stop___cmd
>>> referenced by iw.c:418
>>>               iw.o:(__handle_cmd)

Suggested-by: Fangrui Song <maskray@google.com>

Signed-off-by: Manoj Gupta <manojgupta@google.com>
---
 iw.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/iw.h b/iw.h
index 7f7f4fc..67aa00c 100644
--- a/iw.h
+++ b/iw.h
@@ -118,8 +118,9 @@ struct chandef {
 		.parent = _section,					\
 		.selector = (_sel),					\
 	};								\
+	_Pragma("GCC diagnostic ignored \"-Wattributes\"") 		\
 	static struct cmd *__cmd ## _ ## _symname ## _ ## _handler ## _ ## _nlcmd ## _ ## _idby ## _ ## _hidden ## _p \
-	__attribute__((used,section("__cmd"))) =			\
+	__attribute__((used,retain,section("__cmd"))) =			\
 	&__cmd ## _ ## _symname ## _ ## _handler ## _ ## _nlcmd ## _ ## _idby ## _ ## _hidden
 #define __ACMD(_section, _symname, _name, _args, _nlcmd, _flags, _hidden, _idby, _handler, _help, _sel, _alias)\
 	__COMMAND(_section, _symname, _name, _args, _nlcmd, _flags, _hidden, _idby, _handler, _help, _sel);\
-- 
2.31.1.498.g6c1eba8ee3d-goog