From 3bbb92772813c7a955d210f0e82ebdedd3183cec Mon Sep 17 00:00:00 2001 From: Felix Fietkau Date: Fri, 30 Oct 2015 15:20:12 +0000 Subject: [PATCH] build: Allow kernel modules to set build ID debug symbol MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 SVN-Revision: 47290 --- include/kernel-defaults.mk | 3 ++- rules.mk | 3 ++- scripts/strip-kmod.sh | 5 ++++- 3 files changed, 8 insertions(+), 3 deletions(-) diff --git a/include/kernel-defaults.mk b/include/kernel-defaults.mk index 24d26308b1..d37787a44b 100644 --- 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 819bea5f5a..7710fb4d9d 100644 --- 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 13e6b58007..e3f13bee47 100755 --- 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 \