FROMLIST: kbuild: Add environment variables for userprogs flags
Allow additional arguments be passed to userprogs compilation.
Reproducible clang builds need to provide a sysroot and gcc path to
ensure the 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.
Clang 13+ might 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=/path/to/sysroot
This can also be used to specify different sysroots such as musl or
bionic which may be installed on the host in paths that the compiler
may not search by default.
Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Bug: 214127735
Link: https://lore.kernel.org/linux-kbuild/20220201213542.2808035-1-quic_eberman@quicinc.com/
Change-Id: I035309a569130774a1212f294973eee2830a6588
(cherry picked from commit df704104322c6bd1b3d40cb7ad109cba7453f3be)
diff --git a/Documentation/kbuild/kbuild.rst b/Documentation/kbuild/kbuild.rst
index 2d1fc03..ef19b9c 100644
--- a/Documentation/kbuild/kbuild.rst
+++ b/Documentation/kbuild/kbuild.rst
@@ -77,6 +77,17 @@
----------
Additional libraries to link against when building host programs.
+.. _userkbuildflags:
+
+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 0d5dd54..1db205d 100644
--- a/Documentation/kbuild/makefiles.rst
+++ b/Documentation/kbuild/makefiles.rst
@@ -852,6 +852,8 @@
When linking bpfilter_umh, it will be passed the extra option -static.
+ From command line, :ref:`USERCFLAGS and USERLDFLAGS <userkbuildflags>` will also be used.
+
5.4 When userspace programs are actually built
----------------------------------------------
diff --git a/Makefile b/Makefile
index cfebae2..3f37437 100644
--- a/Makefile
+++ b/Makefile
@@ -429,11 +429,12 @@
HOSTCXX = g++
endif
-export KBUILD_USERCFLAGS := -Wall -Wmissing-prototypes -Wstrict-prototypes \
- -O2 -fomit-frame-pointer -std=gnu89
-export KBUILD_USERLDFLAGS :=
+KBUILD_USERHOSTCFLAGS := -Wall -Wmissing-prototypes -Wstrict-prototypes \
+ -O2 -fomit-frame-pointer -std=gnu89
+KBUILD_USERCFLAGS := $(KBUILD_USERHOSTCFLAGS) $(USERCFLAGS)
+KBUILD_USERLDFLAGS := $(USERLDFLAGS)
-KBUILD_HOSTCFLAGS := $(KBUILD_USERCFLAGS) $(HOST_LFS_CFLAGS) $(HOSTCFLAGS)
+KBUILD_HOSTCFLAGS := $(KBUILD_USERHOSTCFLAGS) $(HOST_LFS_CFLAGS) $(HOSTCFLAGS)
KBUILD_HOSTCXXFLAGS := -Wall -O2 $(HOST_LFS_CFLAGS) $(HOSTCXXFLAGS)
KBUILD_HOSTLDFLAGS := $(HOST_LFS_LDFLAGS) $(HOSTLDFLAGS)
KBUILD_HOSTLDLIBS := $(HOST_LFS_LIBS) $(HOSTLDLIBS)
@@ -526,6 +527,7 @@
export PERL PYTHON 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 c08acd2..ee9b239 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -53,13 +53,13 @@
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 703a255..a8ed689 100644
--- a/usr/include/Makefile
+++ b/usr/include/Makefile
@@ -12,6 +12,9 @@
# 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.