kbuild: Add support for CONFIG_UNUSED_KSYMS_WHITELIST_ONLY

CONFIG_UNUSED_KSYMS_WHITELIST_ONLY extends the support for the
existing CONFIG_UNUSED_KSYMS_WHITELIST in a way that, if enabled,
it would allow the kbuild to export ONLY the symbols that are
supplied as a part of whitelist (and of course the ones exported
by modules). That is, the build would break for modules during
modpost with:
ERROR: "<symbol>" [<module>.ko] undefined!

When enabled, the option is quite useful in build integration
systems to detect if the whitelist file needs an update.

Change-Id: Ica0a270214d4d51f6e2269fdc591fb86acbc4f97
Signed-off-by: Raghavendra Rao Ananta <rananta@codeaurora.org>

Makefile

@@ -1362,6 +1362,8 @@ all: modules
 
 PHONY += modules
 modules: $(if $(KBUILD_BUILTIN),vmlinux) modules.order modules.builtin
+	$(Q)$(CONFIG_SHELL) $(srctree)/scripts/adjust_autoksyms.sh \
+	  "$(MAKE) -f $(srctree)/Makefile vmlinux"
 	$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modpost
 	$(Q)$(CONFIG_SHELL) $(srctree)/scripts/modules-check.sh
 

init/Kconfig

@@ -2250,6 +2250,17 @@ config UNUSED_KSYMS_WHITELIST
 	  one per line. The path can be absolute, or relative to the kernel
 	  source tree.
 
+config UNUSED_KSYMS_WHITELIST_ONLY
+	bool "Export ONLY the symbols that are a part of whitelist"
+	depends on UNUSED_KSYMS_WHITELIST != ""
+	help
+	  Keep ONLY the symbols that are defined in the whitelist. The
+	  CONFIG works on top of CONFIG_UNUSED_KSYMS_WHITELIST which takes
+	  whitelist file(s) as its settings, and would export only the
+	  symbols listed in these file(s).
+	  This is mainly used to detect if drivers are using the symbols
+	  outside of the whitelist.
+
 endif # MODULES
 
 config MODULES_TREE_LOOKUP

scripts/adjust_autoksyms.sh

@@ -40,6 +40,11 @@ esac
 # Generate a new symbol list file
 $CONFIG_SHELL $srctree/scripts/gen_autoksyms.sh "$new_ksyms_file"
 
+if [ -n "$CONFIG_UNUSED_KSYMS_WHITELIST_ONLY" ] && [ -f "vmlinux" ] ; then
+	info "WARNING" "CONFIG_UNUSED_KSYMS_WHITELIST_ONLY is enabled. "\
+"Non-whitelisted symbols will be undefined!"
+fi
+
 # Extract changes between old and new list and touch corresponding
 # dependency files.
 changed=$(

scripts/gen_autoksyms.sh

@@ -21,13 +21,18 @@ esac
 
 ksym_wl=/dev/null
 if [ -n "$CONFIG_UNUSED_KSYMS_WHITELIST" ]; then
-	# Use 'eval' to expand the whitelist path and check if it is relative
-	eval ksym_wl="$CONFIG_UNUSED_KSYMS_WHITELIST"
-	[ "${ksym_wl}" != "${ksym_wl#/}" ] || ksym_wl="$abs_srctree/$ksym_wl"
-	if [ ! -f "$ksym_wl" ]; then
-		echo "ERROR: '$ksym_wl' whitelist file not found" >&2
-		exit 1
-	fi
+	for UNUSED_KSYMS_WHITELIST_FILE in $CONFIG_UNUSED_KSYMS_WHITELIST; do
+		# Use 'eval' to expand the whitelist path and
+		# check if it is relative
+		eval ksym_wl="$UNUSED_KSYMS_WHITELIST_FILE"
+		[ "${ksym_wl}" != "${ksym_wl#/}" ] ||
+		ksym_wl="$abs_srctree/$ksym_wl"
+		if [ ! -f "$ksym_wl" ]; then
+			echo "ERROR: '$ksym_wl' whitelist file not found" >&2
+			exit 1
+		fi
+		ksym_wls="$ksym_wls $ksym_wl"
+	done
 fi
 
 # Generate a new ksym list file with symbols needed by the current
@@ -42,7 +47,8 @@ EOT
 [ -f modules.order ] && modlist=modules.order || modlist=/dev/null
 sed 's/ko$/mod/' $modlist |
 xargs -n1 sed -n -e '2{s/ /\n/g;/^$/!p;}' -- |
-cat - "$ksym_wl" |
+cat - $ksym_wls |
+sed 's/^#.*//;s/^ *//;/[[abi_whitelist]]/g' |
 sort -u |
 sed -e 's/\(.*\)/#define __KSYM_\1 1/' >> "$output_file"
 
@@ -50,3 +56,27 @@ sed -e 's/\(.*\)/#define __KSYM_\1 1/' >> "$output_file"
 if [ -n "$CONFIG_MODVERSIONS" ]; then
 	echo "#define __KSYM_module_layout 1" >> "$output_file"
 fi
+
+if [ -n "$CONFIG_UNUSED_KSYMS_WHITELIST_ONLY" ] && [ -f "vmlinux" ] ; then
+	syms_from_whitelist="$(mktemp)"
+	syms_from_vmlinux="$(mktemp)"
+
+	cat $ksym_wls |
+	sed 's/^#.*//;s/^ *//;/[[abi_whitelist]]/g' |
+	sort -u > "$syms_from_whitelist"
+
+	$NM --defined-only vmlinux |
+	grep "__ksymtab_" |
+	sed 's/^.*__ksymtab_//' |
+	sort -u > "$syms_from_vmlinux"
+
+	# Forcefully unexport the symbols that are not declared in the whitelist
+	syms_to_unexport=$(comm -13 "$syms_from_whitelist" "$syms_from_vmlinux")
+
+	for sym_to_unexport in $syms_to_unexport; do
+		sed -i "/^#define __KSYM_${sym_to_unexport} 1/d" \
+							"$output_file"
+	done
+
+	rm -f "$syms_from_whitelist" "$syms_from_vmlinux"
+fi