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| author | Masahiro Yamada <masahiroy@kernel.org> | 2020-04-29 05:45:13 +0200 |
|---|---|---|
| committer | Masahiro Yamada <masahiroy@kernel.org> | 2020-05-17 11:52:01 +0200 |
| commit | 9371f86ecb60f6f1f120e3d93fe892bbb70d04c0 (patch) | |
| tree | 3bf829d594785687c136b1d8295197f58b2038ef | |
| parent | kbuild: warn if always, hostprogs-y, or hostprogs-m is used (diff) | |
| download | linux-9371f86ecb60f6f1f120e3d93fe892bbb70d04c0.tar.xz linux-9371f86ecb60f6f1f120e3d93fe892bbb70d04c0.zip | |
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>
| -rw-r--r-- | init/Kconfig | 4 | ||||
| -rw-r--r-- | net/bpfilter/Makefile | 5 | ||||
| -rw-r--r-- | usr/include/Makefile | 4 |
3 files changed, 10 insertions, 3 deletions
diff --git a/init/Kconfig b/init/Kconfig index ed1d82c9f1df..b2ce83c2e84c 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -45,7 +45,9 @@ 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 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 diff --git a/usr/include/Makefile b/usr/include/Makefile index 5a7ee3e5ed86..55362f3ab393 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. |