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authorElliot Berman <quic_eberman@quicinc.com>2022-02-02 00:35:42 +0300
committerMasahiro Yamada <masahiroy@kernel.org>2022-02-14 04:37:32 +0300
commitf67695c9962e5f444549b3437fb8d840ec6222c8 (patch)
tree96a786f023dd51a8037a55bfc846dacd6c24cb06 /Documentation/kbuild
parenta5575df58004e8444e5a2a307407c3f1a6ecf175 (diff)
downloadlinux-f67695c9962e5f444549b3437fb8d840ec6222c8.tar.xz
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 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> Reviewed-by: Fangrui Song <maskray@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Diffstat (limited to 'Documentation/kbuild')
-rw-r--r--Documentation/kbuild/kbuild.rst11
-rw-r--r--Documentation/kbuild/makefiles.rst2
2 files changed, 13 insertions, 0 deletions
diff --git a/Documentation/kbuild/kbuild.rst b/Documentation/kbuild/kbuild.rst
index 2d1fc03d346e..ef19b9c13523 100644
--- a/Documentation/kbuild/kbuild.rst
+++ b/Documentation/kbuild/kbuild.rst
@@ -77,6 +77,17 @@ HOSTLDLIBS
----------
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 b008b90b92c9..11a296e52d68 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, :ref:`USERCFLAGS and USERLDFLAGS <userkbuildflags>` will also be used.
+
5.4 When userspace programs are actually built
----------------------------------------------