On 2022-01-28, Elliot Berman wrote:
Allow additional arguments be passed to userprogs compilation. Reproducible clang builds need to provide a sysroot and gcc path to ensure same toolchain is used across hosts. KCFLAGS is not currently used for any user programs compilation, so add new USERCFLAGS and USERLDFLAGS which serves similar purpose as HOSTCFLAGS/HOSTLDFLAGS. Specifically, I'm trying to force CC_CAN_LINK to consistently fail in an environment where a user sysroot is not specifically available. Currently, Clang might automatically detect GCC installation on hosts which have it installed to a default location in /. With addition of these environment variables, you can specify flags such as: $ make USERCFLAGS=--sysroot=/dev/null USERLDFLAGS=-Wl,--sysroot=/dev/null to force sysroot detection to fail.
-Wl,--sysroot=/dev/null => --sysroot As I mentioned in https://lore.kernel.org/all/20220128031549.w5a4bilxbkppagfu@xxxxxxxxxx/ -Wl,--sysroot=/dev/null does not suppress search paths like -L/lib .
Signed-off-by: Elliot Berman <quic_eberman@xxxxxxxxxxx> Changes since v1: Addressed minor nits from Nick --- Documentation/kbuild/kbuild.rst | 9 +++++++++ Documentation/kbuild/makefiles.rst | 2 ++ Makefile | 9 ++++++--- init/Kconfig | 8 ++++---- usr/include/Makefile | 3 +++ 5 files changed, 24 insertions(+), 7 deletions(-) diff --git a/Documentation/kbuild/kbuild.rst b/Documentation/kbuild/kbuild.rst index 2d1fc03d346e..3e7467b19c8f 100644 --- a/Documentation/kbuild/kbuild.rst +++ b/Documentation/kbuild/kbuild.rst @@ -77,6 +77,15 @@ HOSTLDLIBS ---------- Additional libraries to link against when building host programs. +USERCFLAGS +---------- +Additional options used for $(CC) when compiling userprogs. + +USERLDFLAGS +---------- +Additional options used for $(LD) when linking userprogs. userprogs are linked +with CC, so $(USERLDFLAGS) should include "-Wl," prefix as applicable. + KBUILD_KCONFIG -------------- Set the top-level Kconfig file to the value of this environment diff --git a/Documentation/kbuild/makefiles.rst b/Documentation/kbuild/makefiles.rst index b008b90b92c9..39fb70f59429 100644 --- a/Documentation/kbuild/makefiles.rst +++ b/Documentation/kbuild/makefiles.rst @@ -982,6 +982,8 @@ The syntax is quite similar. The difference is to use "userprogs" instead of When linking bpfilter_umh, it will be passed the extra option -static. + From command line, USERCFLAGS and USERLDFLAGS will also be used (See kbuild.rst) + 5.4 When userspace programs are actually built ---------------------------------------------- diff --git a/Makefile b/Makefile index 45278d508d81..8a2324e6bda8 100644 --- a/Makefile +++ b/Makefile @@ -431,15 +431,17 @@ HOSTCC = gcc HOSTCXX = g++ endif -export KBUILD_USERCFLAGS := -Wall -Wmissing-prototypes -Wstrict-prototypes \ - -O2 -fomit-frame-pointer -std=gnu89 -export KBUILD_USERLDFLAGS := +KBUILD_USERCFLAGS := -Wall -Wmissing-prototypes -Wstrict-prototypes \ + -O2 -fomit-frame-pointer -std=gnu89 +KBUILD_USERLDFLAGS := $(USERLDFLAGS) KBUILD_HOSTCFLAGS := $(KBUILD_USERCFLAGS) $(HOST_LFS_CFLAGS) $(HOSTCFLAGS) KBUILD_HOSTCXXFLAGS := -Wall -O2 $(HOST_LFS_CFLAGS) $(HOSTCXXFLAGS) KBUILD_HOSTLDFLAGS := $(HOST_LFS_LDFLAGS) $(HOSTLDFLAGS) KBUILD_HOSTLDLIBS := $(HOST_LFS_LIBS) $(HOSTLDLIBS) +KBUILD_USERCFLAGS += $(USERCFLAGS) + # Make variables (CC, etc...) CPP = $(CC) -E ifneq ($(LLVM),) @@ -530,6 +532,7 @@ export CPP AR NM STRIP OBJCOPY OBJDUMP READELF PAHOLE RESOLVE_BTFIDS LEX YACC AW export PERL PYTHON3 CHECK CHECKFLAGS MAKE UTS_MACHINE HOSTCXX export KGZIP KBZIP2 KLZOP LZMA LZ4 XZ ZSTD export KBUILD_HOSTCXXFLAGS KBUILD_HOSTLDFLAGS KBUILD_HOSTLDLIBS LDFLAGS_MODULE +export KBUILD_USERCFLAGS KBUILD_USERLDFLAGS export KBUILD_CPPFLAGS NOSTDINC_FLAGS LINUXINCLUDE OBJCOPYFLAGS KBUILD_LDFLAGS export KBUILD_CFLAGS CFLAGS_KERNEL CFLAGS_MODULE diff --git a/init/Kconfig b/init/Kconfig index f2ae41e6717f..164706c38e8b 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -62,13 +62,13 @@ config LLD_VERSION config CC_CAN_LINK bool - default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag)) if 64BIT - default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m32-flag)) + default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag)) if 64BIT + default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag)) config CC_CAN_LINK_STATIC bool - default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag) -static) if 64BIT - default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m32-flag) -static) + default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag) -static) if 64BIT + default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag) -static) config CC_HAS_ASM_GOTO def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC)) diff --git a/usr/include/Makefile b/usr/include/Makefile index 1c2ae1368079..6a8c7dd9ccaf 100644 --- a/usr/include/Makefile +++ b/usr/include/Makefile @@ -12,6 +12,9 @@ UAPI_CFLAGS := -std=c90 -Wall -Werror=implicit-function-declaration # It is here just because CONFIG_CC_CAN_LINK is tested with -m32 or -m64. UAPI_CFLAGS += $(filter -m32 -m64, $(KBUILD_CFLAGS)) +# USERCFLAGS might contain sysroot location for CC +UAPI_CFLAGS += $(USERCFLAGS) + override c_flags = $(UAPI_CFLAGS) -Wp,-MMD,$(depfile) -I$(objtree)/usr/include # The following are excluded for now because they fail to build. -- 2.25.1
