backport build system: warn if kernel headers aren't there

When the kernel build system/configuration isn't present, warn
verbosely instead of later failing with crypting errors.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/backport/Makefile b/backport/Makefile
index fde14bf463f34e711cb337bc6d4b7847c4c1e910..5cb7016919798dbb3d91525a1c0bc4eb04598fa8 100644 (file)
--- a/backport/Makefile
+++ b/backport/Makefile
@@ -18,7 +18,7 @@ endif
 KLIB_BUILD ?= $(KLIB)/build/
 KERNEL_CONFIG := $(KLIB_BUILD)/.config
 KERNEL_MAKEFILE := $(KLIB_BUILD)/Makefile
-CONFIG_MD5 := $(shell md5sum $(KERNEL_CONFIG) | sed 's/\s.*//')
+CONFIG_MD5 := $(shell md5sum $(KERNEL_CONFIG) 2>/dev/null | sed 's/\s.*//')
 
 export KLIB KLIB_BUILD BACKPORT_PWD KMODDIR KMODPATH_ARG
 
@@ -30,6 +30,17 @@ default:
        @$(MAKE) modules
 
 .DEFAULT:
+       @set -e ; test -f $(KERNEL_CONFIG) || (                                         \
+       echo "/--------------"                                                          ;\
+       echo "| Your kernel headers are incomplete/not installed."                      ;\
+       echo "| Please install kernel headers, including a .config"                     ;\
+       echo "| file or use the KLIB/KLIB_BUILD make variables to"                      ;\
+       echo "| set the kernel to build against, e.g."                                  ;\
+       echo "|   make KLIB=/lib/modules/3.1.7/"                                        ;\
+       echo "| to compile/install for the installed kernel 3.1.7"                      ;\
+       echo "| (that isn't currently running.)"                                        ;\
+       echo "\\--"                                                                     ;\
+       false)
        @set -e ; if [ "$$(cat .kernel_config_md5 2>/dev/null)" != "$(CONFIG_MD5)" ]    ;\
        then                                                                            \
                echo -n "Generating local configuration database from kernel ..."       ;\