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authorMasahiro Yamada <masahiroy@kernel.org>2020-04-29 06:45:13 +0300
committerMasahiro Yamada <masahiroy@kernel.org>2020-05-17 12:52:01 +0300
commit9371f86ecb60f6f1f120e3d93fe892bbb70d04c0 (patch)
tree3bf829d594785687c136b1d8295197f58b2038ef /net/bpfilter
parent59721d4eb7f66f27440ad74f875b97e64133ee3b (diff)
downloadlinux-9371f86ecb60f6f1f120e3d93fe892bbb70d04c0.tar.xz
bpfilter: match bit size of bpfilter_umh to that of the kernel
bpfilter_umh is built for the default machine bit of the compiler, which may not match to the bit size of the kernel. This happens in the scenario below: You can use biarch GCC that defaults to 64-bit for building the 32-bit kernel. In this case, Kbuild passes -m32 to teach the compiler to produce 32-bit kernel space objects. However, it is missing when building bpfilter_umh. It is built as a 64-bit ELF, and then embedded into the 32-bit kernel. The 32-bit kernel and 64-bit umh is a bad combination. In theory, we can have 32-bit umh running on 64-bit kernel, but we do not have a good reason to support such a usecase. The best is to match the bit size between them. Pass -m32 or -m64 to the umh build command if it is found in $(KBUILD_CFLAGS). Evaluate CC_CAN_LINK against the kernel bit-size. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Diffstat (limited to 'net/bpfilter')
-rw-r--r--net/bpfilter/Makefile5
1 files changed, 3 insertions, 2 deletions
diff --git a/net/bpfilter/Makefile b/net/bpfilter/Makefile
index 36580301da70..f6209e4827b9 100644
--- a/net/bpfilter/Makefile
+++ b/net/bpfilter/Makefile
@@ -5,14 +5,15 @@
hostprogs := bpfilter_umh
bpfilter_umh-objs := main.o
-KBUILD_HOSTCFLAGS += -I $(srctree)/tools/include/ -I $(srctree)/tools/include/uapi
+KBUILD_HOSTCFLAGS += -I $(srctree)/tools/include/ -I $(srctree)/tools/include/uapi \
+ $(filter -m32 -m64, $(KBUILD_CFLAGS))
HOSTCC := $(CC)
ifeq ($(CONFIG_BPFILTER_UMH), y)
# builtin bpfilter_umh should be compiled with -static
# since rootfs isn't mounted at the time of __init
# function is called and do_execv won't find elf interpreter
-KBUILD_HOSTLDFLAGS += -static
+KBUILD_HOSTLDFLAGS += -static $(filter -m32 -m64, $(KBUILD_CFLAGS))
endif
$(obj)/bpfilter_umh_blob.o: $(obj)/bpfilter_umh