5.4-stable review patch. If anyone has any objections, please let me know.
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From: Masahiro Yamada masahiroy@kernel.org
[ Upstream commit 9371f86ecb60f6f1f120e3d93fe892bbb70d04c0 ]
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 Stable-dep-of: 02e9a22ceef0 ("kbuild: hdrcheck: fix cross build with clang") Signed-off-by: Sasha Levin sashal@kernel.org --- init/Kconfig | 4 +++- net/bpfilter/Makefile | 5 +++-- usr/include/Makefile | 4 ++++ 3 files changed, 10 insertions(+), 3 deletions(-)
diff --git a/init/Kconfig b/init/Kconfig index 41e87e8a5c6c1..50adf085d08b7 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -28,7 +28,9 @@ config CLANG_VERSION default $(shell,$(srctree)/scripts/clang-version.sh $(CC))
config CC_CAN_LINK - def_bool $(success,$(srctree)/scripts/cc-can-link.sh $(CC)) + bool + default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(m64-flag)) if 64BIT + default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(m32-flag))
config CC_HAS_ASM_GOTO def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC)) diff --git a/net/bpfilter/Makefile b/net/bpfilter/Makefile index aa945ab5b6558..05930c2fafd52 100644 --- a/net/bpfilter/Makefile +++ b/net/bpfilter/Makefile @@ -5,14 +5,15 @@
hostprogs-y := 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 diff --git a/usr/include/Makefile b/usr/include/Makefile index 6c4b79d4558d6..3d9dc4a5c6fca 100644 --- a/usr/include/Makefile +++ b/usr/include/Makefile @@ -8,6 +8,10 @@ # We cannot go as far as adding -Wpedantic since it emits too many warnings. UAPI_CFLAGS := -std=c90 -Wall -Werror=implicit-function-declaration
+# In theory, we do not care -m32 or -m64 for header compile tests. +# It is here just because CONFIG_CC_CAN_LINK is tested with -m32 or -m64. +UAPI_CFLAGS += $(filter -m32 -m64, $(KBUILD_CFLAGS)) + override c_flags = $(UAPI_CFLAGS) -Wp,-MMD,$(depfile) -I$(objtree)/usr/include
# The following are excluded for now because they fail to build.