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

[Masahiro Yamada <masahiroy@kernel.org>]

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