[PATCH v2 00/15] kbuild: support 'userprogs' syntax

[PATCH v2 00/15] kbuild: support 'userprogs' syntax

[Masahiro Yamada]

Several Makefiles use 'hostprogs' to build programs for the host
architecture where it is not appropriate to do so.
This is just because Kbuild lacks the support for building programs
for the target architecture.

This series introduce 'userprogs' syntax and use it from
sample and bpf Makefiles.

Sam worked on this in 2014.
https://lkml.org/lkml/2014/7/13/154

He used 'uapiprogs-y' but I just thought the meaning of
"UAPI programs" is unclear.

Naming the syntax is one of the most difficult parts.

I chose 'userprogs'. Anothor choice I had in my mind was 'targetprogs'.

You can test this series quickly by 'make allmodconfig samples/'

When building objects for userspace, [U] is displayed.

masahiro@oscar:~/workspace/linux$ make allmodconfig samples/
  [snip]
  AR      samples/vfio-mdev/built-in.a
  CC [M]  samples/vfio-mdev/mtty.o
  CC [M]  samples/vfio-mdev/mdpy.o
  CC [M]  samples/vfio-mdev/mdpy-fb.o
  CC [M]  samples/vfio-mdev/mbochs.o
  AR      samples/mei/built-in.a
  CC [U]  samples/mei/mei-amt-version
  CC [U]  samples/auxdisplay/cfag12864b-example
  CC [M]  samples/configfs/configfs_sample.o
  CC [M]  samples/connector/cn_test.o
  CC [U]  samples/connector/ucon
  CC [M]  samples/ftrace/ftrace-direct.o
  CC [M]  samples/ftrace/ftrace-direct-too.o
  CC [M]  samples/ftrace/ftrace-direct-modify.o
  CC [M]  samples/ftrace/sample-trace-array.o
  CC [U]  samples/hidraw/hid-example
  CC [M]  samples/hw_breakpoint/data_breakpoint.o
  CC [M]  samples/kdb/kdb_hello.o
  CC [M]  samples/kfifo/bytestream-example.o
  CC [M]  samples/kfifo/dma-example.o
  CC [M]  samples/kfifo/inttype-example.o
  CC [M]  samples/kfifo/record-example.o
  CC [M]  samples/kobject/kobject-example.o
  CC [M]  samples/kobject/kset-example.o
  CC [M]  samples/kprobes/kprobe_example.o
  CC [M]  samples/kprobes/kretprobe_example.o
  CC [M]  samples/livepatch/livepatch-sample.o
  CC [M]  samples/livepatch/livepatch-shadow-mod.o
  CC [M]  samples/livepatch/livepatch-shadow-fix1.o
  CC [M]  samples/livepatch/livepatch-shadow-fix2.o
  CC [M]  samples/livepatch/livepatch-callbacks-demo.o
  CC [M]  samples/livepatch/livepatch-callbacks-mod.o
  CC [M]  samples/livepatch/livepatch-callbacks-busymod.o
  CC [M]  samples/rpmsg/rpmsg_client_sample.o
  CC [U]  samples/seccomp/bpf-fancy.o
  CC [U]  samples/seccomp/bpf-helper.o
  LD [U]  samples/seccomp/bpf-fancy
  CC [U]  samples/seccomp/dropper
  CC [U]  samples/seccomp/bpf-direct
  CC [U]  samples/seccomp/user-trap
  CC [U]  samples/timers/hpet_example
  CC [M]  samples/trace_events/trace-events-sample.o
  CC [M]  samples/trace_printk/trace-printk.o
  CC [U]  samples/uhid/uhid-example
  CC [M]  samples/v4l/v4l2-pci-skeleton.o
  CC [U]  samples/vfs/test-fsmount
  CC [U]  samples/vfs/test-statx
samples/vfs/test-statx.c:24:15: warning: ‘struct foo’ declared inside parameter list will not be visible outside of this definition or declaration
   24 | #define statx foo
      |               ^~~
  CC [U]  samples/watchdog/watchdog-simple
  AR      samples/built-in.a

Changes for v2:
  - Fix ARCH=i386 build error for bpfilter_umh
  - Rename 'user-ccflags' to 'userccflags'
    because 'user-ccflags' would conflict if an object
    called 'user.o' exists in the directory.
  - Support 'userldflags'

Masahiro Yamada (14):
  bpfilter: match bit size of bpfilter_umh to that of the kernel
  kbuild: add infrastructure to build userspace programs
  bpfilter: use 'userprogs' syntax to build bpfilter_umh
  samples: seccomp: build sample programs for target architecture
  kbuild: doc: document the new syntax 'userprogs'
  samples: uhid: build sample program for target architecture
  samples: hidraw: build sample program for target architecture
  samples: connector: build sample program for target architecture
  samples: vfs: build sample programs for target architecture
  samples: pidfd: build sample program for target architecture
  samples: mei: build sample program for target architecture
  samples: auxdisplay: use 'userprogs' syntax
  samples: timers: use 'userprogs' syntax
  samples: watchdog: use 'userprogs' syntax

Sam Ravnborg (1):
  samples: uhid: fix warnings in uhid-example

 Documentation/kbuild/makefiles.rst | 183 +++++++++++++++++++++--------
 Makefile                           |  13 +-
 init/Kconfig                       |   4 +-
 net/bpfilter/Makefile              |  11 +-
 samples/Kconfig                    |  26 +++-
 samples/Makefile                   |   4 +
 samples/auxdisplay/Makefile        |  11 +-
 samples/connector/Makefile         |  12 +-
 samples/hidraw/Makefile            |   9 +-
 samples/mei/Makefile               |   9 +-
 samples/pidfd/Makefile             |   8 +-
 samples/seccomp/Makefile           |  42 +------
 samples/timers/Makefile            |  17 +--
 samples/uhid/.gitignore            |   2 +
 samples/uhid/Makefile              |   9 +-
 samples/uhid/uhid-example.c        |   4 +-
 samples/vfs/Makefile               |  11 +-
 samples/watchdog/Makefile          |  10 +-
 scripts/Makefile.build             |   6 +
 scripts/Makefile.clean             |   2 +-
 scripts/Makefile.userprogs         |  45 +++++++
 usr/include/Makefile               |   4 +
 22 files changed, 267 insertions(+), 175 deletions(-)
 create mode 100644 samples/uhid/.gitignore
 create mode 100644 scripts/Makefile.userprogs

-- 
2.25.1

[PATCH v2 01/15] bpfilter: match bit size of bpfilter_umh to that of the kernel

[Masahiro Yamada]

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>
---

Changes in v2:
  - New patch

 init/Kconfig          | 4 +++-
 net/bpfilter/Makefile | 5 +++--
 usr/include/Makefile  | 4 ++++
 3 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/init/Kconfig b/init/Kconfig
index a494212a3a79..57562a8e2761 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.
-- 
2.25.1

[PATCH v2 02/15] kbuild: add infrastructure to build userspace programs

[Masahiro Yamada]

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@kernel.org>
Acked-by: Sam Ravnborg <sam@ravnborg.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

[PATCH v2 03/15] bpfilter: use 'userprogs' syntax to build bpfilter_umh

[Masahiro Yamada]

The user mode helper should be compiled for the same architecture as
the kernel.

This Makefile reused the 'hostprogs' syntax by overriding HOSTCC with CC.
Use the new syntax 'userprogs' to fix the Makefile mess.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
---

Changes in v2: None

 net/bpfilter/Makefile | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/net/bpfilter/Makefile b/net/bpfilter/Makefile
index f6209e4827b9..f23b53294fba 100644
--- a/net/bpfilter/Makefile
+++ b/net/bpfilter/Makefile
@@ -3,18 +3,14 @@
 # Makefile for the Linux BPFILTER layer.
 #
 
-hostprogs := bpfilter_umh
+userprogs := bpfilter_umh
 bpfilter_umh-objs := main.o
-KBUILD_HOSTCFLAGS += -I $(srctree)/tools/include/ -I $(srctree)/tools/include/uapi \
-			$(filter -m32 -m64, $(KBUILD_CFLAGS))
-HOSTCC := $(CC)
+userccflags += -I $(srctree)/tools/include/ -I $(srctree)/tools/include/uapi
 
-ifeq ($(CONFIG_BPFILTER_UMH), y)
-# builtin bpfilter_umh should be compiled with -static
+# builtin bpfilter_umh should be linked 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 $(filter -m32 -m64, $(KBUILD_CFLAGS))
-endif
+userldflags += -static
 
 $(obj)/bpfilter_umh_blob.o: $(obj)/bpfilter_umh
 
-- 
2.25.1

[PATCH v2 04/15] samples: seccomp: build sample programs for target architecture

[Masahiro Yamada]

These userspace programs include UAPI headers exported to usr/include/.
'make headers' always works for the target architecture (i.e. the same
architecture as the kernel), so the sample programs should be built for
the target as well. Kbuild now supports 'userprogs' for that.

I also guarded the CONFIG option by 'depends on CC_CAN_LINK' because
$(CC) may not provide libc.

The 'ifndef CROSS_COMPILE' is no longer needed.

BTW, the -m31 for s390 is left-over code. Commit 5a79859ae0f3 ("s390:
remove 31 bit support") killed it.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
---

Changes in v2: None

 samples/Kconfig          |  2 +-
 samples/seccomp/Makefile | 42 +++-------------------------------------
 2 files changed, 4 insertions(+), 40 deletions(-)

diff --git a/samples/Kconfig b/samples/Kconfig
index 9d236c346de5..8949e9646125 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -126,7 +126,7 @@ config SAMPLE_PIDFD
 
 config SAMPLE_SECCOMP
 	bool "Build seccomp sample code"
-	depends on SECCOMP_FILTER && HEADERS_INSTALL
+	depends on SECCOMP_FILTER && CC_CAN_LINK && HEADERS_INSTALL
 	help
 	  Build samples of seccomp filters using various methods of
 	  BPF filter construction.
diff --git a/samples/seccomp/Makefile b/samples/seccomp/Makefile
index 89279e8b87df..75916c23e416 100644
--- a/samples/seccomp/Makefile
+++ b/samples/seccomp/Makefile
@@ -1,44 +1,8 @@
 # SPDX-License-Identifier: GPL-2.0
-ifndef CROSS_COMPILE
-hostprogs := bpf-fancy dropper bpf-direct user-trap
+userprogs := bpf-fancy dropper bpf-direct user-trap
 
-HOSTCFLAGS_bpf-fancy.o += -I$(objtree)/usr/include
-HOSTCFLAGS_bpf-fancy.o += -idirafter $(objtree)/include
-HOSTCFLAGS_bpf-helper.o += -I$(objtree)/usr/include
-HOSTCFLAGS_bpf-helper.o += -idirafter $(objtree)/include
 bpf-fancy-objs := bpf-fancy.o bpf-helper.o
 
-HOSTCFLAGS_dropper.o += -I$(objtree)/usr/include
-HOSTCFLAGS_dropper.o += -idirafter $(objtree)/include
-dropper-objs := dropper.o
+userccflags += -I usr/include
 
-HOSTCFLAGS_bpf-direct.o += -I$(objtree)/usr/include
-HOSTCFLAGS_bpf-direct.o += -idirafter $(objtree)/include
-bpf-direct-objs := bpf-direct.o
-
-HOSTCFLAGS_user-trap.o += -I$(objtree)/usr/include
-HOSTCFLAGS_user-trap.o += -idirafter $(objtree)/include
-user-trap-objs := user-trap.o
-
-# Try to match the kernel target.
-ifndef CONFIG_64BIT
-
-# s390 has -m31 flag to build 31 bit binaries
-ifndef CONFIG_S390
-MFLAG = -m32
-else
-MFLAG = -m31
-endif
-
-HOSTCFLAGS_bpf-direct.o += $(MFLAG)
-HOSTCFLAGS_dropper.o += $(MFLAG)
-HOSTCFLAGS_bpf-helper.o += $(MFLAG)
-HOSTCFLAGS_bpf-fancy.o += $(MFLAG)
-HOSTCFLAGS_user-trap.o += $(MFLAG)
-HOSTLDLIBS_bpf-direct += $(MFLAG)
-HOSTLDLIBS_bpf-fancy += $(MFLAG)
-HOSTLDLIBS_dropper += $(MFLAG)
-HOSTLDLIBS_user-trap += $(MFLAG)
-endif
-always-y := $(hostprogs)
-endif
+always-y := $(userprogs)
-- 
2.25.1

[PATCH v2 05/15] kbuild: doc: document the new syntax 'userprogs'

[Masahiro Yamada]

Kbuild now supports the syntax 'userprogs' to compile userspace
programs for the same architecture as the kernel.

Insert the section '5 Userspace Program support' to explain it.

I copy-pasted '4 Host Program support' and fixed it up.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
---

Changes in v2: None

 Documentation/kbuild/makefiles.rst | 183 +++++++++++++++++++++--------
 1 file changed, 135 insertions(+), 48 deletions(-)

diff --git a/Documentation/kbuild/makefiles.rst b/Documentation/kbuild/makefiles.rst
index b80257a03830..234492351031 100644
--- a/Documentation/kbuild/makefiles.rst
+++ b/Documentation/kbuild/makefiles.rst
@@ -29,31 +29,37 @@ This document describes the Linux kernel Makefiles.
 	   --- 4.4 Controlling compiler options for host programs
 	   --- 4.5 When host programs are actually built
 
-	=== 5 Kbuild clean infrastructure
-
-	=== 6 Architecture Makefiles
-	   --- 6.1 Set variables to tweak the build to the architecture
-	   --- 6.2 Add prerequisites to archheaders:
-	   --- 6.3 Add prerequisites to archprepare:
-	   --- 6.4 List directories to visit when descending
-	   --- 6.5 Architecture-specific boot images
-	   --- 6.6 Building non-kbuild targets
-	   --- 6.7 Commands useful for building a boot image
-	   --- 6.8 Custom kbuild commands
-	   --- 6.9 Preprocessing linker scripts
-	   --- 6.10 Generic header files
-	   --- 6.11 Post-link pass
-
-	=== 7 Kbuild syntax for exported headers
-		--- 7.1 no-export-headers
-		--- 7.2 generic-y
-		--- 7.3 generated-y
-		--- 7.4 mandatory-y
-
-	=== 8 Kbuild Variables
-	=== 9 Makefile language
-	=== 10 Credits
-	=== 11 TODO
+	=== 5 Userspace Program support
+	   --- 5.1 Simple Userspace Program
+	   --- 5.2 Composite Userspace Programs
+	   --- 5.3 Controlling compiler options for userspace programs
+	   --- 5.4 When userspace programs are actually built
+
+	=== 6 Kbuild clean infrastructure
+
+	=== 7 Architecture Makefiles
+	   --- 7.1 Set variables to tweak the build to the architecture
+	   --- 7.2 Add prerequisites to archheaders:
+	   --- 7.3 Add prerequisites to archprepare:
+	   --- 7.4 List directories to visit when descending
+	   --- 7.5 Architecture-specific boot images
+	   --- 7.6 Building non-kbuild targets
+	   --- 7.7 Commands useful for building a boot image
+	   --- 7.8 Custom kbuild commands
+	   --- 7.9 Preprocessing linker scripts
+	   --- 7.10 Generic header files
+	   --- 7.11 Post-link pass
+
+	=== 8 Kbuild syntax for exported headers
+		--- 8.1 no-export-headers
+		--- 8.2 generic-y
+		--- 8.3 generated-y
+		--- 8.4 mandatory-y
+
+	=== 9 Kbuild Variables
+	=== 10 Makefile language
+	=== 11 Credits
+	=== 12 TODO
 
 1 Overview
 ==========
@@ -732,7 +738,88 @@ Both possibilities are described in the following.
 	This will tell kbuild to build lxdialog even if not referenced in
 	any rule.
 
-5 Kbuild clean infrastructure
+5 Userspace Program support
+===========================
+
+Just like host programs, Kbuild also supports building userspace executables
+for the target architecture (i.e. the same architecture as you are building
+the kernel for).
+
+The syntax is quite similar. The difference is to use "userprogs" instead of
+"hostprogs".
+
+5.1 Simple Userspace Program
+----------------------------
+
+	The following line tells kbuild that the program bpf-direct shall be
+	built for the target architecture.
+
+	Example::
+
+		userprogs := bpf-direct
+
+	Kbuild assumes in the above example that bpf-direct is made from a
+	single C source file named bpf-direct.c located in the same directory
+	as the Makefile.
+
+5.2 Composite Userspace Programs
+--------------------------------
+
+	Userspace programs can be made up based on composite objects.
+	The syntax used to define composite objects for userspace programs is
+	similar to the syntax used for kernel objects.
+	$(<executable>-objs) lists all objects used to link the final
+	executable.
+
+	Example::
+
+		#samples/seccomp/Makefile
+		userprogs      := bpf-fancy
+		bpf-fancy-objs := bpf-fancy.o bpf-helper.o
+
+	Objects with extension .o are compiled from the corresponding .c
+	files. In the above example, bpf-fancy.c is compiled to bpf-fancy.o
+	and bpf-helper.c is compiled to bpf-helper.o.
+
+	Finally, the two .o files are linked to the executable, bpf-fancy.
+	Note: The syntax <executable>-y is not permitted for userspace programs.
+
+5.3 Controlling compiler options for userspace programs
+-------------------------------------------------------
+
+	When compiling userspace programs, it is possible to set specific flags.
+	The programs will always be compiled utilising $(CC) passed
+	the options specified in $(KBUILD_USERCFLAGS).
+	To set flags that will take effect for all userspace programs created
+	in that Makefile, use the variable userccflags.
+
+	Example::
+
+		# samples/seccomp/Makefile
+		userccflags += -I usr/include
+
+	To set specific flags for a single file the following construction
+	is used:
+
+	Example::
+
+		bpf-helper-ccflags += -I user/include
+
+	It is also possible to specify additional options to the linker.
+
+	Example::
+
+		# net/bpfilter/Makefile
+		bpfilter_umh-ldflags += -static
+
+	When linking bpfilter_umh, it will be passed the extra option -static.
+
+5.4 When userspace programs are actually built
+----------------------------------------------
+
+	Same as "When host programs are actually built".
+
+6 Kbuild clean infrastructure
 =============================
 
 "make clean" deletes most generated files in the obj tree where the kernel
@@ -790,7 +877,7 @@ is not operational at that point.
 Note 2: All directories listed in core-y, libs-y, drivers-y and net-y will
 be visited during "make clean".
 
-6 Architecture Makefiles
+7 Architecture Makefiles
 ========================
 
 The top level Makefile sets up the environment and does the preparation,
@@ -820,7 +907,7 @@ When kbuild executes, the following steps are followed (roughly):
    - Preparing initrd images and the like
 
 
-6.1 Set variables to tweak the build to the architecture
+7.1 Set variables to tweak the build to the architecture
 --------------------------------------------------------
 
     LDFLAGS
@@ -967,7 +1054,7 @@ When kbuild executes, the following steps are followed (roughly):
 	KBUILD_VMLINUX_LIBS together specify all the object files used to
 	link vmlinux.
 
-6.2 Add prerequisites to archheaders
+7.2 Add prerequisites to archheaders
 ------------------------------------
 
 	The archheaders: rule is used to generate header files that
@@ -977,7 +1064,7 @@ When kbuild executes, the following steps are followed (roughly):
 	architecture itself.
 
 
-6.3 Add prerequisites to archprepare
+7.3 Add prerequisites to archprepare
 ------------------------------------
 
 	The archprepare: rule is used to list prerequisites that need to be
@@ -995,7 +1082,7 @@ When kbuild executes, the following steps are followed (roughly):
 	generating offset header files.
 
 
-6.4 List directories to visit when descending
+7.4 List directories to visit when descending
 ---------------------------------------------
 
 	An arch Makefile cooperates with the top Makefile to define variables
@@ -1030,7 +1117,7 @@ When kbuild executes, the following steps are followed (roughly):
 		drivers-$(CONFIG_OPROFILE)  += arch/sparc64/oprofile/
 
 
-6.5 Architecture-specific boot images
+7.5 Architecture-specific boot images
 -------------------------------------
 
 	An arch Makefile specifies goals that take the vmlinux file, compress
@@ -1085,7 +1172,7 @@ When kbuild executes, the following steps are followed (roughly):
 
 	When "make" is executed without arguments, bzImage will be built.
 
-6.6 Building non-kbuild targets
+7.6 Building non-kbuild targets
 -------------------------------
 
     extra-y
@@ -1108,7 +1195,7 @@ When kbuild executes, the following steps are followed (roughly):
 	In this example, extra-y is used to list object files that
 	shall be built, but shall not be linked as part of built-in.a.
 
-6.7 Commands useful for building a boot image
+7.7 Commands useful for building a boot image
 ---------------------------------------------
 
     Kbuild provides a few macros that are useful when building a
@@ -1211,7 +1298,7 @@ When kbuild executes, the following steps are followed (roughly):
 		targets += $(dtb-y)
 		DTC_FLAGS ?= -p 1024
 
-6.8 Custom kbuild commands
+7.8 Custom kbuild commands
 --------------------------
 
 	When kbuild is executing with KBUILD_VERBOSE=0, then only a shorthand
@@ -1241,7 +1328,7 @@ When kbuild executes, the following steps are followed (roughly):
 	will be displayed with "make KBUILD_VERBOSE=0".
 
 
-6.9 Preprocessing linker scripts
+7.9 Preprocessing linker scripts
 --------------------------------
 
 	When the vmlinux image is built, the linker script
@@ -1274,7 +1361,7 @@ When kbuild executes, the following steps are followed (roughly):
 	The kbuild infrastructure for `*lds` files is used in several
 	architecture-specific files.
 
-6.10 Generic header files
+7.10 Generic header files
 -------------------------
 
 	The directory include/asm-generic contains the header files
@@ -1283,7 +1370,7 @@ When kbuild executes, the following steps are followed (roughly):
 	to list the file in the Kbuild file.
 	See "7.2 generic-y" for further info on syntax etc.
 
-6.11 Post-link pass
+7.11 Post-link pass
 -------------------
 
 	If the file arch/xxx/Makefile.postlink exists, this makefile
@@ -1299,7 +1386,7 @@ When kbuild executes, the following steps are followed (roughly):
 	For example, powerpc uses this to check relocation sanity of
 	the linked vmlinux file.
 
-7 Kbuild syntax for exported headers
+8 Kbuild syntax for exported headers
 ------------------------------------
 
 The kernel includes a set of headers that is exported to userspace.
@@ -1319,14 +1406,14 @@ A Kbuild file may be defined under arch/<arch>/include/uapi/asm/ and
 arch/<arch>/include/asm/ to list asm files coming from asm-generic.
 See subsequent chapter for the syntax of the Kbuild file.
 
-7.1 no-export-headers
+8.1 no-export-headers
 ---------------------
 
 	no-export-headers is essentially used by include/uapi/linux/Kbuild to
 	avoid exporting specific headers (e.g. kvm.h) on architectures that do
 	not support it. It should be avoided as much as possible.
 
-7.2 generic-y
+8.2 generic-y
 -------------
 
 	If an architecture uses a verbatim copy of a header from
@@ -1356,7 +1443,7 @@ See subsequent chapter for the syntax of the Kbuild file.
 
 			#include <asm-generic/termios.h>
 
-7.3 generated-y
+8.3 generated-y
 ---------------
 
 	If an architecture generates other header files alongside generic-y
@@ -1370,7 +1457,7 @@ See subsequent chapter for the syntax of the Kbuild file.
 			#arch/x86/include/asm/Kbuild
 			generated-y += syscalls_32.h
 
-7.4 mandatory-y
+8.4 mandatory-y
 ---------------
 
 	mandatory-y is essentially used by include/(uapi/)asm-generic/Kbuild
@@ -1380,7 +1467,7 @@ See subsequent chapter for the syntax of the Kbuild file.
 	in arch/$(ARCH)/include/(uapi/)/asm, Kbuild will automatically generate
 	a wrapper of the asm-generic one.
 
-8 Kbuild Variables
+9 Kbuild Variables
 ==================
 
 The top Makefile exports the following variables:
@@ -1438,8 +1525,8 @@ The top Makefile exports the following variables:
 	command.
 
 
-9 Makefile language
-===================
+10 Makefile language
+====================
 
 The kernel Makefiles are designed to be run with GNU Make.  The Makefiles
 use only the documented features of GNU Make, but they do use many
@@ -1458,7 +1545,7 @@ time the left-hand side is used.
 There are some cases where "=" is appropriate.  Usually, though, ":="
 is the right choice.
 
-10 Credits
+11 Credits
 ==========
 
 - Original version made by Michael Elizabeth Chastain, <mailto:mec@shout.net>
@@ -1466,7 +1553,7 @@ is the right choice.
 - Updates by Sam Ravnborg <sam@ravnborg.org>
 - Language QA by Jan Engelhardt <jengelh@gmx.de>
 
-11 TODO
+12 TODO
 =======
 
 - Describe how kbuild supports shipped files with _shipped.
-- 
2.25.1

[PATCH v2 06/15] samples: uhid: fix warnings in uhid-example

[Masahiro Yamada]

From: Sam Ravnborg <sam@ravnborg.org>

Fix warnings seen when building for 32-bit architecture.

Use "%xd" for arguments of type size_t to fix the warnings.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---

Changes in v2: None

 samples/uhid/uhid-example.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/samples/uhid/uhid-example.c b/samples/uhid/uhid-example.c
index b72d645ce828..015cb06a241e 100644
--- a/samples/uhid/uhid-example.c
+++ b/samples/uhid/uhid-example.c
@@ -165,7 +165,7 @@ static int uhid_write(int fd, const struct uhid_event *ev)
 		fprintf(stderr, "Cannot write to uhid: %m\n");
 		return -errno;
 	} else if (ret != sizeof(*ev)) {
-		fprintf(stderr, "Wrong size written to uhid: %ld != %lu\n",
+		fprintf(stderr, "Wrong size written to uhid: %zd != %zu\n",
 			ret, sizeof(ev));
 		return -EFAULT;
 	} else {
@@ -236,7 +236,7 @@ static int event(int fd)
 		fprintf(stderr, "Cannot read uhid-cdev: %m\n");
 		return -errno;
 	} else if (ret != sizeof(ev)) {
-		fprintf(stderr, "Invalid size read from uhid-dev: %ld != %lu\n",
+		fprintf(stderr, "Invalid size read from uhid-dev: %zd != %zu\n",
 			ret, sizeof(ev));
 		return -EFAULT;
 	}
-- 
2.25.1

[PATCH v2 07/15] samples: uhid: build sample program for target architecture

[Masahiro Yamada]

This userspace program includes UAPI headers exported to usr/include/.
'make headers' always works for the target architecture (i.e. the same
architecture as the kernel), so the sample program should be built for
the target as well. Kbuild now supports 'userprogs' for that.

Add the entry to samples/Makefile to put this into the build bot
coverage.

I also added the CONFIG option guarded by 'depends on CC_CAN_LINK'
because $(CC) may not provide libc.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
---

Changes in v2: None

 samples/Kconfig         | 6 ++++++
 samples/Makefile        | 1 +
 samples/uhid/.gitignore | 2 ++
 samples/uhid/Makefile   | 9 +++------
 4 files changed, 12 insertions(+), 6 deletions(-)
 create mode 100644 samples/uhid/.gitignore

diff --git a/samples/Kconfig b/samples/Kconfig
index 8949e9646125..2560e87c9cae 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -131,6 +131,12 @@ config SAMPLE_SECCOMP
 	  Build samples of seccomp filters using various methods of
 	  BPF filter construction.
 
+config SAMPLE_UHID
+	bool "UHID sample"
+	depends on CC_CAN_LINK && HEADERS_INSTALL
+	help
+	  Build UHID sample program.
+
 config SAMPLE_VFIO_MDEV_MTTY
 	tristate "Build VFIO mtty example mediated device sample code -- loadable modules only"
 	depends on VFIO_MDEV_DEVICE && m
diff --git a/samples/Makefile b/samples/Makefile
index 5ce50ef0f2b2..bdc168405452 100644
--- a/samples/Makefile
+++ b/samples/Makefile
@@ -19,6 +19,7 @@ obj-$(CONFIG_SAMPLE_TRACE_EVENTS)	+= trace_events/
 obj-$(CONFIG_SAMPLE_TRACE_PRINTK)	+= trace_printk/
 obj-$(CONFIG_SAMPLE_FTRACE_DIRECT)	+= ftrace/
 obj-$(CONFIG_SAMPLE_TRACE_ARRAY)	+= ftrace/
+subdir-$(CONFIG_SAMPLE_UHID)		+= uhid
 obj-$(CONFIG_VIDEO_PCI_SKELETON)	+= v4l/
 obj-y					+= vfio-mdev/
 subdir-$(CONFIG_SAMPLE_VFS)		+= vfs
diff --git a/samples/uhid/.gitignore b/samples/uhid/.gitignore
new file mode 100644
index 000000000000..0e0a5a929f5d
--- /dev/null
+++ b/samples/uhid/.gitignore
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+/uhid-example
diff --git a/samples/uhid/Makefile b/samples/uhid/Makefile
index 5f44ea40d6d5..9e652fc34103 100644
--- a/samples/uhid/Makefile
+++ b/samples/uhid/Makefile
@@ -1,8 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0-only
-# List of programs to build
-hostprogs := uhid-example
+userprogs := uhid-example
+always-y := $(userprogs)
 
-# Tell kbuild to always build the programs
-always-y := $(hostprogs)
-
-HOSTCFLAGS_uhid-example.o += -I$(objtree)/usr/include
+userccflags += -I usr/include
-- 
2.25.1

[PATCH v2 08/15] samples: hidraw: build sample program for target architecture

[Masahiro Yamada]

This userspace program includes UAPI headers exported to usr/include/.
'make headers' always works for the target architecture (i.e. the same
architecture as the kernel), so the sample program should be built for
the target as well. Kbuild now supports 'userprogs' for that.

I also guarded the CONFIG option by 'depends on CC_CAN_LINK' because
$(CC) may not provide libc.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
---

Changes in v2: None

 samples/Kconfig         | 2 +-
 samples/hidraw/Makefile | 9 +++------
 2 files changed, 4 insertions(+), 7 deletions(-)

diff --git a/samples/Kconfig b/samples/Kconfig
index 2560e87c9cae..08f2d025ca05 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -118,7 +118,7 @@ config SAMPLE_CONNECTOR
 
 config SAMPLE_HIDRAW
 	bool "hidraw sample"
-	depends on HEADERS_INSTALL
+	depends on CC_CAN_LINK && HEADERS_INSTALL
 
 config SAMPLE_PIDFD
 	bool "pidfd sample"
diff --git a/samples/hidraw/Makefile b/samples/hidraw/Makefile
index 8bd25f77671f..d2c77ed60b39 100644
--- a/samples/hidraw/Makefile
+++ b/samples/hidraw/Makefile
@@ -1,8 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0
-# List of programs to build
-hostprogs := hid-example
-always-y := $(hostprogs)
+userprogs := hid-example
+always-y := $(userprogs)
 
-HOSTCFLAGS_hid-example.o += -I$(objtree)/usr/include
-
-all: hid-example
+userccflags += -I usr/include
-- 
2.25.1

[PATCH v2 09/15] samples: connector: build sample program for target architecture

[Masahiro Yamada]

This userspace program includes UAPI headers exported to usr/include/.
'make headers' always works for the target architecture (i.e. the same
architecture as the kernel), so the sample program should be built for
the target as well. Kbuild now supports 'userprogs' for that.

$(CC) can always compile cn_text.o since it is the kenrel-space code,
but building ucon requires libc.

I guarded it by:

  always-$(CONFIG_CC_CAN_LINK) := $(userprogs)

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
---

Changes in v2: None

 samples/connector/Makefile | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/samples/connector/Makefile b/samples/connector/Makefile
index b785cbde5ffa..50cb40e09a7b 100644
--- a/samples/connector/Makefile
+++ b/samples/connector/Makefile
@@ -1,13 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 obj-$(CONFIG_SAMPLE_CONNECTOR) += cn_test.o
 
-# List of programs to build
-hostprogs := ucon
-always-y := $(hostprogs)
+userprogs := ucon
+always-$(CONFIG_CC_CAN_LINK) := $(userprogs)
 
-HOSTCFLAGS_ucon.o += -I$(objtree)/usr/include
-
-all: modules
-
-modules clean:
-	$(MAKE) -C ../.. M=$(CURDIR) $@
+userccflags += -I usr/include
-- 
2.25.1

[PATCH v2 10/15] samples: vfs: build sample programs for target architecture

[Masahiro Yamada]

These userspace programs include UAPI headers exported to usr/include/.
'make headers' always works for the target architecture (i.e. the same
architecture as the kernel), so the sample programs should be built for
the target as well. Kbuild now supports 'userprogs' for that.

I also guarded the CONFIG option by 'depends on CC_CAN_LINK' because
$(CC) may not provide libc.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
---

Changes in v2: None

 samples/Kconfig      |  2 +-
 samples/vfs/Makefile | 11 +++--------
 2 files changed, 4 insertions(+), 9 deletions(-)

diff --git a/samples/Kconfig b/samples/Kconfig
index 08f2d025ca05..831a7ecd3352 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -184,7 +184,7 @@ config SAMPLE_ANDROID_BINDERFS
 
 config SAMPLE_VFS
 	bool "Build example programs that use new VFS system calls"
-	depends on HEADERS_INSTALL
+	depends on CC_CAN_LINK && HEADERS_INSTALL
 	help
 	  Build example userspace programs that use new VFS system calls such
 	  as mount API and statx().  Note that this is restricted to the x86
diff --git a/samples/vfs/Makefile b/samples/vfs/Makefile
index 65acdde5c117..00b6824f9237 100644
--- a/samples/vfs/Makefile
+++ b/samples/vfs/Makefile
@@ -1,10 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0-only
-# List of programs to build
-hostprogs := \
-	test-fsmount \
-	test-statx
+userprogs := test-fsmount test-statx
+always-y := $(userprogs)
 
-always-y := $(hostprogs)
-
-HOSTCFLAGS_test-fsmount.o += -I$(objtree)/usr/include
-HOSTCFLAGS_test-statx.o += -I$(objtree)/usr/include
+userccflags += -I usr/include
-- 
2.25.1

[PATCH v2 11/15] samples: pidfd: build sample program for target architecture

[Masahiro Yamada]

This userspace program includes UAPI headers exported to usr/include/.
'make headers' always works for the target architecture (i.e. the same
architecture as the kernel), so the sample program should be built for
the target as well. Kbuild now supports 'userprogs' for that.

I also guarded the CONFIG option by 'depends on CC_CAN_LINK' because
$(CC) may not provide libc.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
---

Changes in v2: None

 samples/Kconfig        | 2 +-
 samples/pidfd/Makefile | 8 ++++----
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/samples/Kconfig b/samples/Kconfig
index 831a7ecd3352..c68d391c0602 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -122,7 +122,7 @@ config SAMPLE_HIDRAW
 
 config SAMPLE_PIDFD
 	bool "pidfd sample"
-	depends on HEADERS_INSTALL
+	depends on CC_CAN_LINK && HEADERS_INSTALL
 
 config SAMPLE_SECCOMP
 	bool "Build seccomp sample code"
diff --git a/samples/pidfd/Makefile b/samples/pidfd/Makefile
index ee2979849d92..6e5b67e648c2 100644
--- a/samples/pidfd/Makefile
+++ b/samples/pidfd/Makefile
@@ -1,6 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0
 
-hostprogs := pidfd-metadata
-always-y := $(hostprogs)
-HOSTCFLAGS_pidfd-metadata.o += -I$(objtree)/usr/include
-all: pidfd-metadata
+usertprogs := pidfd-metadata
+always-y := $(userprogs)
+
+userccflags += -I usr/include
-- 
2.25.1

[PATCH v2 12/15] samples: mei: build sample program for target architecture

[Masahiro Yamada]

This userspace program includes UAPI headers exported to usr/include/.
'make headers' always works for the target architecture (i.e. the same
architecture as the kernel), so the sample program should be built for
the target as well. Kbuild now supports 'userprogs' for that.

I also guarded the CONFIG option by 'depends on CC_CAN_LINK' because
$(CC) may not provide libc.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
---

Changes in v2: None

 samples/Kconfig      | 1 +
 samples/mei/Makefile | 9 +++------
 2 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/samples/Kconfig b/samples/Kconfig
index c68d391c0602..69699db49675 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -193,6 +193,7 @@ config SAMPLE_VFS
 config SAMPLE_INTEL_MEI
 	bool "Build example program working with intel mei driver"
 	depends on INTEL_MEI
+	depends on CC_CAN_LINK && HEADERS_INSTALL
 	help
 	  Build a sample program to work with mei device.
 
diff --git a/samples/mei/Makefile b/samples/mei/Makefile
index f5b9d02be2cd..329411f82369 100644
--- a/samples/mei/Makefile
+++ b/samples/mei/Makefile
@@ -1,10 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 # Copyright (c) 2012-2019, Intel Corporation. All rights reserved.
 
-hostprogs := mei-amt-version
+userprogs := mei-amt-version
+always-y := $(userprogs)
 
-HOSTCFLAGS_mei-amt-version.o += -I$(objtree)/usr/include
-
-always-y := $(hostprogs)
-
-all: mei-amt-version
+userccflags += -I usr/include
-- 
2.25.1

[PATCH v2 13/15] samples: auxdisplay: use 'userprogs' syntax

[Masahiro Yamada]

Kbuild now supports the 'userprogs' syntax to compile userspace
programs for the same architecture as the kernel.

Add the entry to samples/Makefile to put this into the build bot
coverage.

I also added the CONFIG option guarded by 'depends on CC_CAN_LINK'
because $(CC) may not provide libc.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
---

Changes in v2: None

 samples/Kconfig             |  4 ++++
 samples/Makefile            |  1 +
 samples/auxdisplay/Makefile | 11 ++---------
 3 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/samples/Kconfig b/samples/Kconfig
index 69699db49675..2322e11e8b80 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -6,6 +6,10 @@ menuconfig SAMPLES
 
 if SAMPLES
 
+config SAMPLE_AUXDISPLAY
+	bool "auxdisplay sample"
+	depends on CC_CAN_LINK
+
 config SAMPLE_TRACE_EVENTS
 	tristate "Build trace_events examples -- loadable modules only"
 	depends on EVENT_TRACING && m
diff --git a/samples/Makefile b/samples/Makefile
index bdc168405452..0c43b5d34b15 100644
--- a/samples/Makefile
+++ b/samples/Makefile
@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 # Makefile for Linux samples code
 
+subdir-$(CONFIG_SAMPLE_AUXDISPLAY)	+= auxdisplay
 obj-$(CONFIG_SAMPLE_ANDROID_BINDERFS)	+= binderfs/
 obj-$(CONFIG_SAMPLE_CONFIGFS)		+= configfs/
 obj-$(CONFIG_SAMPLE_CONNECTOR)		+= connector/
diff --git a/samples/auxdisplay/Makefile b/samples/auxdisplay/Makefile
index 0273bab27233..dbdf939af94a 100644
--- a/samples/auxdisplay/Makefile
+++ b/samples/auxdisplay/Makefile
@@ -1,10 +1,3 @@
 # SPDX-License-Identifier: GPL-2.0
-CC := $(CROSS_COMPILE)gcc
-CFLAGS := -I../../usr/include
-
-PROGS := cfag12864b-example
-
-all: $(PROGS)
-
-clean:
-	rm -fr $(PROGS)
+userprogs := cfag12864b-example
+always-y := $(userprogs)
-- 
2.25.1

[PATCH v2 14/15] samples: timers: use 'userprogs' syntax

[Masahiro Yamada]

Kbuild now supports the 'userprogs' syntax to compile userspace
programs for the same architecture as the kernel.

Add the entry to samples/Makefile to put this into the build bot
coverage.

I also added the CONFIG option guarded by 'depends on CC_CAN_LINK'
because $(CC) may not provide libc.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
---

Changes in v2: None

 samples/Kconfig         |  4 ++++
 samples/Makefile        |  1 +
 samples/timers/Makefile | 17 +++--------------
 3 files changed, 8 insertions(+), 14 deletions(-)

diff --git a/samples/Kconfig b/samples/Kconfig
index 2322e11e8b80..a8629a0d4f96 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -135,6 +135,10 @@ config SAMPLE_SECCOMP
 	  Build samples of seccomp filters using various methods of
 	  BPF filter construction.
 
+config SAMPLE_TIMER
+	bool "Timer sample"
+	depends on CC_CAN_LINK && HEADERS_INSTALL
+
 config SAMPLE_UHID
 	bool "UHID sample"
 	depends on CC_CAN_LINK && HEADERS_INSTALL
diff --git a/samples/Makefile b/samples/Makefile
index 0c43b5d34b15..042208326689 100644
--- a/samples/Makefile
+++ b/samples/Makefile
@@ -16,6 +16,7 @@ subdir-$(CONFIG_SAMPLE_PIDFD)		+= pidfd
 obj-$(CONFIG_SAMPLE_QMI_CLIENT)		+= qmi/
 obj-$(CONFIG_SAMPLE_RPMSG_CLIENT)	+= rpmsg/
 subdir-$(CONFIG_SAMPLE_SECCOMP)		+= seccomp
+subdir-$(CONFIG_SAMPLE_TIMER)		+= timers
 obj-$(CONFIG_SAMPLE_TRACE_EVENTS)	+= trace_events/
 obj-$(CONFIG_SAMPLE_TRACE_PRINTK)	+= trace_printk/
 obj-$(CONFIG_SAMPLE_FTRACE_DIRECT)	+= ftrace/
diff --git a/samples/timers/Makefile b/samples/timers/Makefile
index f9fa07460802..15c7ddbc8c51 100644
--- a/samples/timers/Makefile
+++ b/samples/timers/Makefile
@@ -1,16 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0
-ifndef CROSS_COMPILE
-uname_M := $(shell uname -m 2>/dev/null || echo not)
-ARCH ?= $(shell echo $(uname_M) | sed -e s/i.86/x86/ -e s/x86_64/x86/)
+userprogs := hpet_example
+always-y := $(userprogs)
 
-ifeq ($(ARCH),x86)
-CC := $(CROSS_COMPILE)gcc
-PROGS := hpet_example
-
-all: $(PROGS)
-
-clean:
-	rm -fr $(PROGS)
-
-endif
-endif
+userccflags += -I usr/include
-- 
2.25.1

[PATCH v2 15/15] samples: watchdog: use 'userprogs' syntax

[Masahiro Yamada]

Kbuild now supports the 'userprogs' syntax to compile userspace
programs for the same architecture as the kernel.

Add the entry to samples/Makefile to put this into the build bot
coverage.

I also added the CONFIG option guarded by 'depends on CC_CAN_LINK'
because $(CC) may not provide libc.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
---

Changes in v2: None

 samples/Kconfig           |  3 +++
 samples/Makefile          |  1 +
 samples/watchdog/Makefile | 10 ++--------
 3 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/samples/Kconfig b/samples/Kconfig
index a8629a0d4f96..5005f74ac0eb 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -205,5 +205,8 @@ config SAMPLE_INTEL_MEI
 	help
 	  Build a sample program to work with mei device.
 
+config SAMPLE_WATCHDOG
+	bool "watchdog sample"
+	depends on CC_CAN_LINK
 
 endif # SAMPLES
diff --git a/samples/Makefile b/samples/Makefile
index 042208326689..29c66aadd954 100644
--- a/samples/Makefile
+++ b/samples/Makefile
@@ -26,3 +26,4 @@ obj-$(CONFIG_VIDEO_PCI_SKELETON)	+= v4l/
 obj-y					+= vfio-mdev/
 subdir-$(CONFIG_SAMPLE_VFS)		+= vfs
 obj-$(CONFIG_SAMPLE_INTEL_MEI)		+= mei/
+subdir-$(CONFIG_SAMPLE_WATCHDOG)	+= watchdog
diff --git a/samples/watchdog/Makefile b/samples/watchdog/Makefile
index a9430fa60253..17384cfb387e 100644
--- a/samples/watchdog/Makefile
+++ b/samples/watchdog/Makefile
@@ -1,9 +1,3 @@
 # SPDX-License-Identifier: GPL-2.0
-CC := $(CROSS_COMPILE)gcc
-PROGS := watchdog-simple
-
-all: $(PROGS)
-
-clean:
-	rm -fr $(PROGS)
-
+userprogs := watchdog-simple
+always-y := $(userprogs)
-- 
2.25.1

Re: [PATCH v2 00/15] kbuild: support 'userprogs' syntax

[Masahiro Yamada]

On Wed, Apr 29, 2020 at 12:45 PM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
>
> Several Makefiles use 'hostprogs' to build programs for the host
> architecture where it is not appropriate to do so.
> This is just because Kbuild lacks the support for building programs
> for the target architecture.
>
> This series introduce 'userprogs' syntax and use it from
> sample and bpf Makefiles.
>
> Sam worked on this in 2014.
> https://lkml.org/lkml/2014/7/13/154
>
> He used 'uapiprogs-y' but I just thought the meaning of
> "UAPI programs" is unclear.
>
> Naming the syntax is one of the most difficult parts.
>
> I chose 'userprogs'. Anothor choice I had in my mind was 'targetprogs'.
>
> You can test this series quickly by 'make allmodconfig samples/'
>
> When building objects for userspace, [U] is displayed.
>
> masahiro@oscar:~/workspace/linux$ make allmodconfig samples/


All applied to linux-kbuild.


>   [snip]
>   AR      samples/vfio-mdev/built-in.a
>   CC [M]  samples/vfio-mdev/mtty.o
>   CC [M]  samples/vfio-mdev/mdpy.o
>   CC [M]  samples/vfio-mdev/mdpy-fb.o
>   CC [M]  samples/vfio-mdev/mbochs.o
>   AR      samples/mei/built-in.a
>   CC [U]  samples/mei/mei-amt-version
>   CC [U]  samples/auxdisplay/cfag12864b-example
>   CC [M]  samples/configfs/configfs_sample.o
>   CC [M]  samples/connector/cn_test.o
>   CC [U]  samples/connector/ucon
>   CC [M]  samples/ftrace/ftrace-direct.o
>   CC [M]  samples/ftrace/ftrace-direct-too.o
>   CC [M]  samples/ftrace/ftrace-direct-modify.o
>   CC [M]  samples/ftrace/sample-trace-array.o
>   CC [U]  samples/hidraw/hid-example
>   CC [M]  samples/hw_breakpoint/data_breakpoint.o
>   CC [M]  samples/kdb/kdb_hello.o
>   CC [M]  samples/kfifo/bytestream-example.o
>   CC [M]  samples/kfifo/dma-example.o
>   CC [M]  samples/kfifo/inttype-example.o
>   CC [M]  samples/kfifo/record-example.o
>   CC [M]  samples/kobject/kobject-example.o
>   CC [M]  samples/kobject/kset-example.o
>   CC [M]  samples/kprobes/kprobe_example.o
>   CC [M]  samples/kprobes/kretprobe_example.o
>   CC [M]  samples/livepatch/livepatch-sample.o
>   CC [M]  samples/livepatch/livepatch-shadow-mod.o
>   CC [M]  samples/livepatch/livepatch-shadow-fix1.o
>   CC [M]  samples/livepatch/livepatch-shadow-fix2.o
>   CC [M]  samples/livepatch/livepatch-callbacks-demo.o
>   CC [M]  samples/livepatch/livepatch-callbacks-mod.o
>   CC [M]  samples/livepatch/livepatch-callbacks-busymod.o
>   CC [M]  samples/rpmsg/rpmsg_client_sample.o
>   CC [U]  samples/seccomp/bpf-fancy.o
>   CC [U]  samples/seccomp/bpf-helper.o
>   LD [U]  samples/seccomp/bpf-fancy
>   CC [U]  samples/seccomp/dropper
>   CC [U]  samples/seccomp/bpf-direct
>   CC [U]  samples/seccomp/user-trap
>   CC [U]  samples/timers/hpet_example
>   CC [M]  samples/trace_events/trace-events-sample.o
>   CC [M]  samples/trace_printk/trace-printk.o
>   CC [U]  samples/uhid/uhid-example
>   CC [M]  samples/v4l/v4l2-pci-skeleton.o
>   CC [U]  samples/vfs/test-fsmount
>   CC [U]  samples/vfs/test-statx
> samples/vfs/test-statx.c:24:15: warning: ‘struct foo’ declared inside parameter list will not be visible outside of this definition or declaration
>    24 | #define statx foo
>       |               ^~~
>   CC [U]  samples/watchdog/watchdog-simple
>   AR      samples/built-in.a
>
> Changes for v2:
>   - Fix ARCH=i386 build error for bpfilter_umh
>   - Rename 'user-ccflags' to 'userccflags'
>     because 'user-ccflags' would conflict if an object
>     called 'user.o' exists in the directory.
>   - Support 'userldflags'
>
> Masahiro Yamada (14):
>   bpfilter: match bit size of bpfilter_umh to that of the kernel
>   kbuild: add infrastructure to build userspace programs
>   bpfilter: use 'userprogs' syntax to build bpfilter_umh
>   samples: seccomp: build sample programs for target architecture
>   kbuild: doc: document the new syntax 'userprogs'
>   samples: uhid: build sample program for target architecture
>   samples: hidraw: build sample program for target architecture
>   samples: connector: build sample program for target architecture
>   samples: vfs: build sample programs for target architecture
>   samples: pidfd: build sample program for target architecture
>   samples: mei: build sample program for target architecture
>   samples: auxdisplay: use 'userprogs' syntax
>   samples: timers: use 'userprogs' syntax
>   samples: watchdog: use 'userprogs' syntax
>
> Sam Ravnborg (1):
>   samples: uhid: fix warnings in uhid-example
>
>  Documentation/kbuild/makefiles.rst | 183 +++++++++++++++++++++--------
>  Makefile                           |  13 +-
>  init/Kconfig                       |   4 +-
>  net/bpfilter/Makefile              |  11 +-
>  samples/Kconfig                    |  26 +++-
>  samples/Makefile                   |   4 +
>  samples/auxdisplay/Makefile        |  11 +-
>  samples/connector/Makefile         |  12 +-
>  samples/hidraw/Makefile            |   9 +-
>  samples/mei/Makefile               |   9 +-
>  samples/pidfd/Makefile             |   8 +-
>  samples/seccomp/Makefile           |  42 +------
>  samples/timers/Makefile            |  17 +--
>  samples/uhid/.gitignore            |   2 +
>  samples/uhid/Makefile              |   9 +-
>  samples/uhid/uhid-example.c        |   4 +-
>  samples/vfs/Makefile               |  11 +-
>  samples/watchdog/Makefile          |  10 +-
>  scripts/Makefile.build             |   6 +
>  scripts/Makefile.clean             |   2 +-
>  scripts/Makefile.userprogs         |  45 +++++++
>  usr/include/Makefile               |   4 +
>  22 files changed, 267 insertions(+), 175 deletions(-)
>  create mode 100644 samples/uhid/.gitignore
>  create mode 100644 scripts/Makefile.userprogs
>
> --
> 2.25.1
>


-- 
Best Regards
Masahiro Yamada