kbuild: generate autoksyms.h early

When doing a cold build, autoksyms.h starts empty, and is updated late
in the build process to have visibility over the symbols used by in-tree
drivers. But since the symbol whitelist is known upfront, it can be used
to pre-populate autoksyms.h and maximize the amount of code that can be
compiled to its final state in a single pass, hence reducing build time.

Do this by using gen_autoksyms.sh to initialize autoksyms.h instead of
creating an empty file.

Acked-by: Nicolas Pitre <nico@fluxnic.net>
Tested-by: Matthias Maennich <maennich@google.com>
Reviewed-by: Matthias Maennich <maennich@google.com>
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

diff --git a/Makefile b/Makefile
index 5435d11d82761b0ff6e04b868dbd61d15e3d51ad..f8b70cf80d796246e95f250c3c7abbaa8833b54c 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -1066,9 +1066,12 @@ endif
 
 autoksyms_h := $(if $(CONFIG_TRIM_UNUSED_KSYMS), include/generated/autoksyms.h)
 
+quiet_cmd_autoksyms_h = GEN     $@
+      cmd_autoksyms_h = mkdir -p $(dir $@); \
+                       $(CONFIG_SHELL) $(srctree)/scripts/gen_autoksyms.sh $@
+
 $(autoksyms_h):
-       $(Q)mkdir -p $(dir $@)
-       $(Q)touch $@
+       $(call cmd,autoksyms_h)
 
 ARCH_POSTLINK := $(wildcard $(srctree)/arch/$(SRCARCH)/Makefile.postlink)
 

diff --git a/scripts/gen_autoksyms.sh b/scripts/gen_autoksyms.sh
index ef46200c366b5964c676ff6e81740147114acab1..16c0b2ddaa4c9b9e952e031e9def3f9d8b790af5 100755 (executable)
--- a/scripts/gen_autoksyms.sh
+++ b/scripts/gen_autoksyms.sh
@@ -39,7 +39,8 @@ cat > "$output_file" << EOT
 
 EOT
 
-sed 's/ko$/mod/' modules.order |
+[ -f modules.order ] && modlist=modules.order || modlist=/dev/null
+sed 's/ko$/mod/' $modlist |
 xargs -n1 sed -n -e '2{s/ /\n/g;/^$/!p;}' -- |
 cat - "$ksym_wl" |
 sort -u |