build: Allow kernel modules to set build ID debug symbol

This change adds support for specifying a build ID for kernel modules.
This is done by setting PKG_BUILD_ID to a hexadecimal string, which will
then be passed to the kernel linker. In addition, when this flag is set,
the build ID debug symbol (.note.gnu.build-id) will not be stripped from
the kernel module. This symbol is exported in sysfs by the kernel (if
the kernel is compiled with CONFIG_KALLSYMS) and so can be used to
uniquely identify a version of a kernel module in a running kernel. This
is useful for keeping track of different versions of a module when doing
experiments and development.

Modules that specify the build ID will be ~100 bytes larger (depending
on the length of the build ID specified). There is no size difference
for kernel modules that do not set this variable.

Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@47290 3c298f89-4303-0410-b956-a3cf2f4a3e73

diff --git a/include/kernel-defaults.mk b/include/kernel-defaults.mk
index 24d2630..d37787a 100644 (file)
--- a/include/kernel-defaults.mk
+++ b/include/kernel-defaults.mk
@@ -11,7 +11,8 @@ KERNEL_MAKEOPTS := -C $(LINUX_DIR) \
        ARCH="$(LINUX_KARCH)" \
        KBUILD_HAVE_NLS=no \
        CONFIG_SHELL="$(BASH)" \
-       $(if $(findstring c,$(OPENWRT_VERBOSE)),V=1,V='')
+       $(if $(findstring c,$(OPENWRT_VERBOSE)),V=1,V='') \
+       $(if $(PKG_BUILD_ID),LDFLAGS_MODULE=--build-id=0x$(PKG_BUILD_ID))
 
 ifdef CONFIG_STRIP_KERNEL_EXPORTS
   KERNEL_MAKEOPTS += \

diff --git a/rules.mk b/rules.mk
index 819bea5..7710fb4 100644 (file)
--- a/rules.mk
+++ b/rules.mk
@@ -273,8 +273,9 @@ else
       STRIP:=$(STAGING_DIR_HOST)/bin/sstrip
     endif
   endif
-  RSTRIP:= \
+  RSTRIP= \
     export CROSS="$(TARGET_CROSS)" \
+               $(if $(PKG_BUILD_ID),KEEP_BUILD_ID=1) \
                $(if $(CONFIG_KERNEL_KALLSYMS),NO_RENAME=1) \
                $(if $(CONFIG_KERNEL_PROFILING),KEEP_SYMBOLS=1); \
     NM="$(TARGET_CROSS)nm" \

diff --git a/scripts/strip-kmod.sh b/scripts/strip-kmod.sh
index 13e6b58..e3f13be 100755 (executable)
--- a/scripts/strip-kmod.sh
+++ b/scripts/strip-kmod.sh
@@ -18,11 +18,14 @@ else
        ARGS="-x -G __this_module --strip-unneeded"
 fi
 
+if [ -z "$KEEP_BUILD_ID" ]; then
+    ARGS="$ARGS -R .note.gnu.build-id"
+fi
+
 ${CROSS}objcopy \
        -R .comment \
        -R .pdr \
        -R .mdebug.abi32 \
-       -R .note.gnu.build-id \
        -R .gnu.attributes \
        -R .reginfo \
        $ARGS \