2 files changed, 28 insertions, 0 deletions

diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
index 80ca538bfba9..a09927e02713 100644
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -258,12 +258,39 @@ if_changed_dep = $(if $(strip $(any-prereq) $(arg-check) ),                  \
         @set -e;                                                             \
         $(cmd_and_fixdep), @:)
 
+ifndef CONFIG_TRIM_UNUSED_KSYMS
+
 cmd_and_fixdep =                                                             \
         $(echo-cmd) $(cmd_$(1));                                             \
         scripts/basic/fixdep $(depfile) $@ '$(make-cmd)' > $(dot-target).tmp;\
         rm -f $(depfile);                                                    \
         mv -f $(dot-target).tmp $(dot-target).cmd;
 
+else
+
+# Filter out exported kernel symbol names from the preprocessor output.
+# See also __KSYM_DEPS__ in include/linux/export.h.
+# We disable the depfile generation here, so as not to overwrite the existing
+# depfile while fixdep is parsing it.
+flags_nodeps = $(filter-out -Wp$(comma)-M%, $($(1)))
+ksym_dep_filter =                                                            \
+        case "$(1)" in                                                       \
+        cc_*_c) $(CPP) $(call flags_nodeps,c_flags) -D__KSYM_DEPS__ $< ;;    \
+        as_*_S) $(CPP) $(call flags_nodeps,a_flags) -D__KSYM_DEPS__ $< ;;    \
+        boot*|build*|*cpp_lds_S|dtc|host*|vdso*) : ;;                        \
+        *) echo "Don't know how to preprocess $(1)" >&2; false ;;            \
+        esac | sed -rn 's/^.*=== __KSYM_(.*) ===.*$$/KSYM_\1/p'
+
+cmd_and_fixdep =                                                             \
+        $(echo-cmd) $(cmd_$(1));                                             \
+        $(ksym_dep_filter) |                                                 \
+                scripts/basic/fixdep -e $(depfile) $@ '$(make-cmd)'          \
+                        > $(dot-target).tmp;                                 \
+        rm -f $(depfile);                                                    \
+        mv -f $(dot-target).tmp $(dot-target).cmd;
+
+endif
+
 # Usage: $(call if_changed_rule,foo)
 # Will check if $(cmd_foo) or any of the prerequisites changed,
 # and if so will execute $(rule_foo).
diff --git a/scripts/basic/fixdep.c b/scripts/basic/fixdep.c
index 7e90a1f7de0f..746ec1ece614 100644
--- a/scripts/basic/fixdep.c
+++ b/scripts/basic/fixdep.c
@@ -358,6 +358,7 @@ static void parse_dep_file(void *map, size_t len)
 
                         /* Ignore certain dependencies */
                         if (strrcmp(s, "include/generated/autoconf.h") &&
+                            strrcmp(s, "include/generated/autoksyms.h") &&
                             strrcmp(s, "arch/um/include/uml-config.h") &&
                             strrcmp(s, "include/linux/kconfig.h") &&
                             strrcmp(s, ".ver")) {