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
Cc: stable@vger.kernel.org
Signed-off-by: Manoj Gupta manojgupta@google.com --- Changes v1 -> v2: Apply the retain attribute to all places with attribute used.
iw.h | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/iw.h b/iw.h index 7f7f4fc..8ca8e44 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);\ @@ -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
#define SECTION(_name) \ struct cmd __section ## _ ## _name = { \ .name = (#_name), \ .hidden = 1, \ }; \ + _Pragma("GCC diagnostic ignored "-Wattributes"") \ static struct cmd *__section ## _ ## _name ## _p \ - __attribute__((used,section("__cmd"))) = &__section ## _ ## _name + __attribute__((used,retain,section("__cmd"))) = &__section ## _ ## _name
#define DECLARE_SECTION(_name) \ extern struct cmd __section ## _ ## _name; @@ -162,13 +165,14 @@ struct vendor_event { };
#define VENDOR_EVENT(_id, _subcmd, _callback) \ + _Pragma("GCC diagnostic ignored "-Wattributes"") \ const struct vendor_event \ vendor_event_ ## _id ## _ ## _subcmd = { \ .vendor_id = _id, \ .subcmd = _subcmd, \ .callback = _callback, \ }, * const vendor_event_ ## _id ## _ ## _subcmd ## _p \ - __attribute__((used,section("vendor_event"))) = \ + __attribute__((used,retain,section("vendor_event"))) = \ &vendor_event_ ## _id ## _ ## _subcmd
extern const char iw_version[];