kbuild: Check for functions with ambiguous -ffunction-sections section names

 * .text.startup could be __attribute__((constructor)) code in a *non*

 * ffunction-sections object, which should be placed in .init.text; or it could

 * be an actual function named startup() in an ffunction-sections object, which

 * should be placed in .text.  Objtool will detect and complain about any such

 * should be placed in .text.  The build will detect and complain about any such

 * ambiguously named functions.

 */

#define TEXT_MAIN							\

	--start-group $(KBUILD_VMLINUX_LIBS) --end-group \

	$(cmd_objtool)

cmd_check_function_names = $(srctree)/scripts/check-function-names.sh $@

define rule_ld_vmlinux.o

	$(call cmd_and_savecmd,ld_vmlinux.o)

	$(call cmd,gen_objtooldep)

	$(call cmd,check_function_names)

endef

vmlinux.o: $(initcalls-lds) vmlinux.a $(KBUILD_VMLINUX_LIBS) FORCE

	$(call if_changed_rule,ld_vmlinux.o)

#!/bin/sh

# SPDX-License-Identifier: GPL-2.0

#

# Certain function names are disallowed due to section name ambiguities

# introduced by -ffunction-sections.

#

# See the comment above TEXT_MAIN in include/asm-generic/vmlinux.lds.h.

objfile="$1"

if [ ! -f "$objfile" ]; then

	echo "usage: $0 <file.o>" >&2

	exit 1

fi

bad_symbols=$(nm "$objfile" | awk '$2 ~ /^[TtWw]$/ {print $3}' | grep -E '^(startup|exit|split|unlikely|hot|unknown)(\.|$)')

if [ -n "$bad_symbols" ]; then

	echo "$bad_symbols" | while read -r sym; do

		echo "$objfile: error: $sym() function name creates ambiguity with -ffunction-sections" >&2

	done

	exit 1

fi

exit 0