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Message-Id: <20200429034527.590520-3-masahiroy@kernel.org>
Date: Wed, 29 Apr 2020 12:45:14 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: linux-kbuild@...r.kernel.org
Cc: bpf <bpf@...r.kernel.org>, Arnd Bergmann <arnd@...db.de>,
Sam Ravnborg <sam@...nborg.org>, linux-kernel@...r.kernel.org,
Masahiro Yamada <masahiroy@...nel.org>
Subject: [PATCH v2 02/15] kbuild: add infrastructure to build userspace programs
Kbuild supports the infrastructure to build host programs, but there
was no support to build userspace programs for the target architecture
(i.e. the same architecture as the kernel).
Sam Ravnborg worked on this in 2014 (https://lkml.org/lkml/2014/7/13/154),
but it was not merged. One problem at that time was, there was no good way
to know whether $(CC) can link standalone programs. In fact, pre-built
kernel.org toolchains [1] are often used for building the kernel, but they
do not provide libc.
Now, we can handle this cleanly because the compiler capability is
evaluated at the Kconfig time. If $(CC) cannot link standalone programs,
the relevant options are hidden by 'depends on CC_CAN_LINK'.
The implementation just mimics scripts/Makefile.host
The userspace programs are compiled with the same flags as the host
programs. In addition, it uses -m32 or -m64 if it is found in
$(KBUILD_CFLAGS).
This new syntax has two usecases.
- Sample programs
Several userspace programs under samples/ include UAPI headers
installed in usr/include. Most of them were previously built for
the host architecture just to use the 'hostprogs' syntax.
However, 'make headers' always works for the target architecture.
This caused the arch mismatch in cross-compiling. To fix this
distortion, sample code should be built for the target architecture.
- Bpfilter
net/bpfilter/Makefile compiles bpfilter_umh as the user mode helper,
and embeds it into the kernel. Currently, it overrides HOSTCC with
CC to use the 'hostprogs' syntax. This hack should go away.
[1]: https://mirrors.edge.kernel.org/pub/tools/crosstool/
Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
Acked-by: Sam Ravnborg <sam@...nborg.org>
---
Changes in v2:
- Rename 'user-ccflags' to 'userccflags'
We use '<base-filename>-ccflags' for the per-file flag.
'user-ccflags' would have a
Makefile | 13 ++++++++---
scripts/Makefile.build | 6 +++++
scripts/Makefile.clean | 2 +-
scripts/Makefile.userprogs | 45 ++++++++++++++++++++++++++++++++++++++
4 files changed, 62 insertions(+), 4 deletions(-)
create mode 100644 scripts/Makefile.userprogs
diff --git a/Makefile b/Makefile
index ee7773d5f4c9..9ff00bfe0575 100644
--- a/Makefile
+++ b/Makefile
@@ -406,9 +406,12 @@ else
HOSTCC = gcc
HOSTCXX = g++
endif
-KBUILD_HOSTCFLAGS := -Wall -Wmissing-prototypes -Wstrict-prototypes -O2 \
- -fomit-frame-pointer -std=gnu89 $(HOST_LFS_CFLAGS) \
- $(HOSTCFLAGS)
+
+export KBUILD_USERCFLAGS := -Wall -Wmissing-prototypes -Wstrict-prototypes \
+ -O2 -fomit-frame-pointer -std=gnu89
+export KBUILD_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) $(HOSTLDLIBS)
@@ -937,6 +940,10 @@ ifeq ($(CONFIG_RELR),y)
LDFLAGS_vmlinux += --pack-dyn-relocs=relr
endif
+# Align the bit size of userspace programs with the kernel
+KBUILD_USERCFLAGS += $(filter -m32 -m64, $(KBUILD_CFLAGS))
+KBUILD_USERLDFLAGS += $(filter -m32 -m64, $(KBUILD_CFLAGS))
+
# make the checker run with the right architecture
CHECKFLAGS += --arch=$(ARCH)
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 9fcbfac15d1d..3665b1a0bc8e 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -50,6 +50,12 @@ ifneq ($(hostprogs)$(hostcxxlibs-y)$(hostcxxlibs-m),)
include scripts/Makefile.host
endif
+# Do not include userprogs rules unless needed.
+userprogs := $(sort $(userprogs))
+ifneq ($(userprogs),)
+include scripts/Makefile.userprogs
+endif
+
ifndef obj
$(warning kbuild: Makefile.build is included improperly)
endif
diff --git a/scripts/Makefile.clean b/scripts/Makefile.clean
index 075f0cc2d8d7..e2c76122319d 100644
--- a/scripts/Makefile.clean
+++ b/scripts/Makefile.clean
@@ -29,7 +29,7 @@ subdir-ymn := $(addprefix $(obj)/,$(subdir-ymn))
__clean-files := $(extra-y) $(extra-m) $(extra-) \
$(always) $(always-y) $(always-m) $(always-) $(targets) $(clean-files) \
- $(hostprogs) $(hostprogs-y) $(hostprogs-m) $(hostprogs-) \
+ $(hostprogs) $(hostprogs-y) $(hostprogs-m) $(hostprogs-) $(userprogs) \
$(hostcxxlibs-y) $(hostcxxlibs-m)
__clean-files := $(filter-out $(no-clean-files), $(__clean-files))
diff --git a/scripts/Makefile.userprogs b/scripts/Makefile.userprogs
new file mode 100644
index 000000000000..ebde030e7dd0
--- /dev/null
+++ b/scripts/Makefile.userprogs
@@ -0,0 +1,45 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Build userspace programs for the target system
+#
+
+# Executables compiled from a single .c file
+user-csingle := $(foreach m, $(userprogs), $(if $($(m)-objs),,$(m)))
+
+# Executables linked based on several .o files
+user-cmulti := $(foreach m, $(userprogs), $(if $($(m)-objs),$(m)))
+
+# Objects compiled from .c files
+user-cobjs := $(sort $(foreach m, $(userprogs), $($(m)-objs)))
+
+user-csingle := $(addprefix $(obj)/, $(user-csingle))
+user-cmulti := $(addprefix $(obj)/, $(user-cmulti))
+user-cobjs := $(addprefix $(obj)/, $(user-cobjs))
+
+user_ccflags = -Wp,-MMD,$(depfile) $(KBUILD_USERCFLAGS) $(userccflags) \
+ $($(target-stem)-ccflags)
+user_ldflags = $(KBUILD_USERLDFLAGS) $(userldflags) $($(target-stem)-ldflags)
+
+# Create an executable from a single .c file
+quiet_cmd_user_cc_c = CC [U] $@
+ cmd_user_cc_c = $(CC) $(user_ccflags) $(user_ldflags) -o $@ $< \
+ $($(target-stem)-ldlibs)
+$(user-csingle): $(obj)/%: $(src)/%.c FORCE
+ $(call if_changed_dep,user_cc_c)
+
+# Link an executable based on list of .o files
+quiet_cmd_user_ld = LD [U] $@
+ cmd_user_ld = $(CC) $(user_ldflags) -o \
+ $@ $(addprefix $(obj)/, $($(target-stem)-objs)) \
+ $($(target-stem)-ldlibs)
+$(user-cmulti): FORCE
+ $(call if_changed,user_ld)
+$(call multi_depend, $(user-cmulti), , -objs)
+
+# Create .o file from a .c file
+quiet_cmd_user_cc_o_c = CC [U] $@
+ cmd_user_cc_o_c = $(CC) $(user_ccflags) -c -o $@ $<
+$(user-cobjs): $(obj)/%.o: $(src)/%.c FORCE
+ $(call if_changed_dep,user_cc_o_c)
+
+targets += $(user-csingle) $(user-cmulti) $(user-cobjs)
--
2.25.1
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