linux/tools: make it a real, separate package

The kernel source tree also contains the sources for various userland
tools, of which cpupower, perf or selftests.

Currently, we have support for building those tools as part of the
kernel build procedure. This looked the correct thing to do so far,
because, well, they *are* part of the kernel source tree and some
really have to be the same version as the kernel that will run.

However, this is causing quite a non-trivial-to-break circular
dependency in some configurations. For example, this defconfig fails to
build (similar to the one reported by Paul):

    BR2_arm=y
    BR2_cortex_a7=y
    BR2_ARM_FPU_NEON_VFPV4=y
    BR2_TOOLCHAIN_EXTERNAL=y
    BR2_INIT_SYSTEMD=y
    BR2_LINUX_KERNEL=y
    BR2_LINUX_KERNEL_CUSTOM_GIT=y
    BR2_LINUX_KERNEL_CUSTOM_REPO_URL="https://github.com/raspberrypi/linux.git"
    BR2_LINUX_KERNEL_CUSTOM_REPO_VERSION="26f3b72a9c049be10e6af196252283e1f6ab9d1f"
    BR2_LINUX_KERNEL_DEFCONFIG="bcm2709"
    BR2_PACKAGE_LINUX_TOOLS_CPUPOWER=y
    BR2_PACKAGE_CRYPTODEV=y
    BR2_PACKAGE_OPENSSL=y
    BR2_PACKAGE_LIBCURL=y

This causes a circular dependency, as explained by Thomas:

 - When libcurl is enabled, systemd depends on it

 - When OpenSSL is enabled, obviously, will use it for SSL support

 - When cryptodev-linux is enabled, OpenSSL will depend on it to use
   crypto accelerators supported in the kernel via cryptodev-linux.

 - cryptodev-linux being a kernel module, it depends on linux

 - linux by itself (the kernel) does not depend on pciutils, but the
   linux tool "cpupower" (managed in linux-tool-cpupower) depends on
   pciutils

 - pciutils depends on udev when available

 - udev is provided by systemd.

And indeed, during the build, we can see that make warns (it's only
reported as a *warning*, not as an actual error):

    [...]
    make[1]: Circular /home/ymorin/dev/buildroot/O/build/openssl-1.0.2h/.stamp_configured
    <- cryptodev-linux dependency dropped.
    >>> openssl 1.0.2h Downloading
    [...]

So the build fails later on, when openssl is actually built:

    eng_cryptodev.c:57:31: fatal error: crypto/cryptodev.h: No such file or directory
    compilation terminated.
    <builtin>: recipe for target 'eng_cryptodev.o' failed

Furthermore, graph-depends also detects the circular dependency, but
treats it as a hard-error:

    Recursion detected for  : cryptodev-linux
    which is a dependency of: openssl
    which is a dependency of: libcurl
    which is a dependency of: systemd
    which is a dependency of: udev
    which is a dependency of: pciutils
    which is a dependency of: linux
    which is a dependency of: cryptodev-linux
    Makefile:738: recipe for target 'graph-depends' failed

Of course, there is no way to break the loop without losing
functionality in either one of the involved packages *and* keep
our infrastructure and packages as-is.

The only solution is to break the loop at the linux-tools level, by
moving them away into their own package, so that the linux package will
no longer have the opportunity to depend on another package via a
dependency of one the tools.

All three linux tools are thus moved away to their own package.

The package infrastructure only knows of three types of packages: those
in package/ , in boot/ , in toolchain/ and the one in linux/ . So we
create that new linux-tools package in package/ so that we don't have to
fiddle with yet another special case in the infra. Still, we want its
configure options to appear in the kernel's sub-menu.

So, we make it a prompt-less package, with only the tools visible as
options of that package, but without the usual dependency on their
master symbol; they only depend on the Linux kernel.

Furthermore, because the kernel is such a huge pile of code, we would
not be very happy to extract it a second time just for the sake of a few
tools. We can't extract only the tools/ sub-directory from the kernel
source either, because some tools have hard-coded path to includes from
the kernel (arch and stuff).

Instead, we just use the linux source tree as our own build tree, and
ensure the linux tree is extracted and patched before linux-tools is
configured and built.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Paul Ashford <paul.ashford@zurria.co.uk>
[Thomas:
 - fix typo #(@D) -> $(@D)
 - fix the inclusion of the per-tool .mk files.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

1 files changed, 1 insertions, 23 deletions

diff --git a/linux/linux.mk b/linux/linux.mk
index 5cbb5e5f19..988427ca7c 100644
--- a/linux/linux.mk
+++ b/linux/linux.mk
@@ -400,7 +400,7 @@ define LINUX_INSTALL_TARGET_CMDS
 	$(LINUX_INSTALL_HOST_TOOLS)
 endef
 
-# Include all our extensions and tools definitions.
+# Include all our extensions.
 #
 # Note: our package infrastructure uses the full-path of the last-scanned
 # Makefile to determine what package we're currently defining, using the
@@ -411,7 +411,6 @@ endef
 # the current Makefile, we are OK. But this is a hard requirement: files
 # included here *must* be in the same directory!
 include $(sort $(wildcard linux/linux-ext-*.mk))
-include $(sort $(wildcard linux/linux-tool-*.mk))
 
 LINUX_PATCH_DEPENDENCIES += $(foreach ext,$(LINUX_EXTENSIONS),\
 	$(if $(BR2_LINUX_KERNEL_EXT_$(call UPPERCASE,$(ext))),$(ext)))
@@ -420,27 +419,6 @@ LINUX_PRE_PATCH_HOOKS += $(foreach ext,$(LINUX_EXTENSIONS),\
 	$(if $(BR2_LINUX_KERNEL_EXT_$(call UPPERCASE,$(ext))),\
 		$(call UPPERCASE,$(ext))_PREPARE_KERNEL))
 
-# Install Linux kernel tools in the staging directory since some tools
-# may install shared libraries and headers (e.g. cpupower). The kernel
-# image is NOT installed in the staging directory.
-LINUX_INSTALL_STAGING = YES
-
-LINUX_DEPENDENCIES += $(foreach tool,$(LINUX_TOOLS),\
-	$(if $(BR2_LINUX_KERNEL_TOOL_$(call UPPERCASE,$(tool))),\
-		$($(call UPPERCASE,$(tool))_DEPENDENCIES)))
-
-LINUX_POST_BUILD_HOOKS += $(foreach tool,$(LINUX_TOOLS),\
-	$(if $(BR2_LINUX_KERNEL_TOOL_$(call UPPERCASE,$(tool))),\
-		$(call UPPERCASE,$(tool))_BUILD_CMDS))
-
-LINUX_POST_INSTALL_STAGING_HOOKS += $(foreach tool,$(LINUX_TOOLS),\
-	$(if $(BR2_LINUX_KERNEL_TOOL_$(call UPPERCASE,$(tool))),\
-		$(call UPPERCASE,$(tool))_INSTALL_STAGING_CMDS))
-
-LINUX_POST_INSTALL_TARGET_HOOKS += $(foreach tool,$(LINUX_TOOLS),\
-	$(if $(BR2_LINUX_KERNEL_TOOL_$(call UPPERCASE,$(tool))),\
-		$(call UPPERCASE,$(tool))_INSTALL_TARGET_CMDS))
-
 # Checks to give errors that the user can understand
 ifeq ($(BR_BUILDING),y)