Re: [PATCH v2] iw: set retain atrribute on sections
From: Johannes Berg <johannes@sipsolutions.net>
Date: 2021-05-31 19:33:39
On Mon, 2021-04-26 at 09:30 -0700, Manoj Gupta wrote:
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___cmdquoted
quoted
quoted
referenced by iw.c:418 iw.o:(__handle_cmd)Suggested-by: Fangrui Song <redacted> Cc: stable@vger.kernel.org
This is *clearly* inappropriate.
quoted hunk ↗ jump to hunk
+++ 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);\@@ -141,16 +142,18 @@ struct chandef {.handler = (_handler), \ .help = (_help), \ }; \ + _Pragma("GCC diagnostic ignored \"-Wattributes\"") \ static struct cmd *__section ## _ ## _name ## _p \ - __attribute__((used,section("__cmd"))) = &__section ## _ ## _name + __attribute__((used,retain,section("__cmd"))) = &__section ## _ ## _name
All of these cases are in macros, it feels it would be more appropriate
to do _Pragma("GCC diagnostic push") and ...pop... around it?
johannes