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diff --git a/docs/developer/corearchitecture/buildsystem/buildrootmakefile.rst b/docs/developer/corearchitecture/buildsystem/buildrootmakefile.rst new file mode 100644 index 00000000000..1eb4e6b5301 --- /dev/null +++ b/docs/developer/corearchitecture/buildsystem/buildrootmakefile.rst @@ -0,0 +1,353 @@ +Introduction to build-root/Makefile +=================================== + +The vpp build system consists of a top-level Makefile, a data-driven +build-root/Makefile, and a set of makefile fragments. The various parts +come together as the result of a set of well-thought-out conventions. + +This section describes build-root/Makefile in some detail. + +Repository Groups and Source Paths +---------------------------------- + +Current vpp workspaces comprise a single repository group. The file +.../build-root/build-config.mk defines a key variable called +SOURCE\_PATH. The SOURCE\_PATH variable names the set of repository +groups. At the moment, there is only one repository group. + +Single pass build system, dependencies and components +----------------------------------------------------- + +The vpp build system caters to components built with GNU autoconf / +automake. Adding such components is a simple process. Dealing with +components which use BSD-style raw Makefiles is a more difficult. +Dealing with toolchain components such as gcc, glibc, and binutils can +be considerably more complicated. + +The vpp build system is a **single-pass** build system. A partial order +must exist for any set of components: the set of (a before b) tuples +must resolve to an ordered list. If you create a circular dependency of +the form; (a,b) (b,c) (c,a), gmake will try to build the target list, +but there’s a 0.0% chance that the results will be pleasant. Cut-n-paste +mistakes in .../build-data/packages/.mk can produce confusing failures. + +In a single-pass build system, it’s best to separate libraries and +applications which instantiate them. For example, if vpp depends on +libfoo.a, and myapp depends on both vpp and libfoo.a, it's best to place +libfoo.a and myapp in separate components. The build system will build +libfoo.a, vpp, and then (as a separate component) myapp. If you try to +build libfoo.a and myapp from the same component, it won’t work. + +If you absolutely, positively insist on having myapp and libfoo.a in the +same source tree, you can create a pseudo-component in a separate .mk +file in the .../build-data/packages/ directory. Define the code +phoneycomponent\_source = realcomponent, and provide manual +configure/build/install targets. + +Separate components for myapp, libfoo.a, and vpp is the best and easiest +solution. However, the “mumble\_source = realsource” degree of freedom +exists to solve intractable circular dependencies, such as: to build +gcc-bootstrap, followed by glibc, followed by “real” gcc/g++ [which +depends on glibc too]. + +.../build-root +-------------- + +The .../build-root directory contains the repository group specification +build-config.mk, the main Makefile, and the system-wide set of +autoconf/automake variable overrides in config.site. We'll describe +these files in some detail. To be clear about expectations: the main +Makefile and config.site file are subtle and complex. It's unlikely that +you'll need or want to modify them. Poorly planned changes in either +place typically cause bugs that are difficult to solve. + +.../build-root/build-config.mk +------------------------------ + +As described above, the build-config.mk file is straightforward: it sets +the make variable SOURCE\_PATH to a list of repository group absolute +paths. + +The SOURCE\_PATH variable If you choose to move a workspace, make sure +to modify the paths defined by the SOURCE\_PATH variable. Those paths +need to match changes you make in the workspace paths. For example, if +you place the vpp directory in the workspace of a user named jsmith, you +might change the SOURCE\_PATH to: + +SOURCE\_PATH = /home/jsmithuser/workspace/vpp + +The "out of the box" setting should work 99.5% of the time: + +:: + + SOURCE_PATH = $(CURDIR)/.. + +.../vpp/build-root/Makefile +--------------------------- + +The main Makefile is complex in a number of dimensions. If you think you +need to modify it, it's a good idea to do some research, or ask for +advice before you change it. + +The main Makefile was organized and designed to provide the following +characteristics: excellent performance, accurate dependency processing, +cache enablement, timestamp optimizations, git integration, +extensibility, builds with cross-compilation tool chains, and builds +with embedded Linux distributions. + +If you really need to do so, you can build double-cross tools with it, +with a minimum amount of fuss. For example, you could: compile gdb on +x86\_64, to run on PowerPC, to debug the Xtensa instruction set. + +The PLATFORM variable +--------------------- + +The PLATFORM make/environment variable controls a number of important +characteristics, primarily: + +- CPU architecture +- The list of images to build. + +With respect to .../build-root/Makefile, the list of images to build is +specified by the target. For example: + +:: + + make PLATFORM=vpp TAG=vpp_debug install-deb + +builds vpp debug Debian packages. + +The main Makefile interprets $PLATFORM by attempting to "-include" the +file /build-data/platforms.mk: + +:: + + $(foreach d,$(FULL_SOURCE_PATH), \ + $(eval -include $(d)/platforms.mk)) + +By convention, we don't define **platforms** in the +...//build-data/platforms.mk file. + +In the vpp case, we search for platform definition makefile fragments in +.../vpp/build-data/platforms.mk, as follows: + +:: + + $(foreach d,$(SOURCE_PATH_BUILD_DATA_DIRS), \ + $(eval -include $(d)/platforms/*.mk)) + +With vpp, which uses the "vpp" platform as discussed above, we end up +"-include"-ing .../vpp/build-data/platforms/vpp.mk. + +The platform-specific .mk fragment +---------------------------------- + +Here are the contents of .../build-data/platforms/vpp.mk: + +:: + + MACHINE=$(shell uname -m) + + vpp_arch = native + ifeq ($(TARGET_PLATFORM),thunderx) + vpp_dpdk_target = arm64-thunderx-linuxapp-gcc + endif + vpp_native_tools = vppapigen + + vpp_uses_dpdk = yes + + # Uncomment to enable building unit tests + # vpp_enable_tests = yes + + vpp_root_packages = vpp + + # DPDK configuration parameters + # vpp_uses_dpdk_mlx4_pmd = yes + # vpp_uses_dpdk_mlx5_pmd = yes + # vpp_uses_external_dpdk = yes + # vpp_dpdk_inc_dir = /usr/include/dpdk + # vpp_dpdk_lib_dir = /usr/lib + # vpp_dpdk_shared_lib = yes + + # Use '--without-libnuma' for non-numa aware architecture + # Use '--enable-dlmalloc' to use dlmalloc instead of mheap + vpp_configure_args_vpp = --enable-dlmalloc + sample-plugin_configure_args_vpp = --enable-dlmalloc + + # load balancer plugin is not portable on 32 bit platform + ifeq ($(MACHINE),i686) + vpp_configure_args_vpp += --disable-lb-plugin + endif + + vpp_debug_TAG_CFLAGS = -g -O0 -DCLIB_DEBUG \ + -fstack-protector-all -fPIC -Werror + vpp_debug_TAG_CXXFLAGS = -g -O0 -DCLIB_DEBUG \ + -fstack-protector-all -fPIC -Werror + vpp_debug_TAG_LDFLAGS = -g -O0 -DCLIB_DEBUG \ + -fstack-protector-all -fPIC -Werror + + vpp_TAG_CFLAGS = -g -O2 -D_FORTIFY_SOURCE=2 -fstack-protector -fPIC -Werror + vpp_TAG_CXXFLAGS = -g -O2 -D_FORTIFY_SOURCE=2 -fstack-protector -fPIC -Werror + vpp_TAG_LDFLAGS = -g -O2 -D_FORTIFY_SOURCE=2 -fstack-protector -fPIC -Werror -pie -Wl,-z,now + + vpp_clang_TAG_CFLAGS = -g -O2 -D_FORTIFY_SOURCE=2 -fstack-protector -fPIC -Werror + vpp_clang_TAG_LDFLAGS = -g -O2 -D_FORTIFY_SOURCE=2 -fstack-protector -fPIC -Werror + + vpp_gcov_TAG_CFLAGS = -g -O0 -DCLIB_DEBUG -fPIC -Werror -fprofile-arcs -ftest-coverage + vpp_gcov_TAG_LDFLAGS = -g -O0 -DCLIB_DEBUG -fPIC -Werror -coverage + + vpp_coverity_TAG_CFLAGS = -g -O2 -fPIC -Werror -D__COVERITY__ + vpp_coverity_TAG_LDFLAGS = -g -O2 -fPIC -Werror -D__COVERITY__ + +Note the following variable settings: + +- The variable \_arch sets the CPU architecture used to build the + per-platform cross-compilation toolchain. With the exception of the + "native" architecture - used in our example - the vpp build system + produces cross-compiled binaries. + +- The variable \_native\_tools lists the required set of self-compiled + build tools. + +- The variable \_root\_packages lists the set of images to build when + specifying the target: make PLATFORM= TAG= [install-deb \| + install-rpm]. + +The TAG variable +---------------- + +The TAG variable indirectly sets CFLAGS and LDFLAGS, as well as the +build and install directory names in the .../vpp/build-root directory. +See definitions above. + +Important targets build-root/Makefile +------------------------------------- + +The main Makefile and the various makefile fragments implement the +following user-visible targets: + ++------------------+----------------------+--------------------------------------------------------------------------------------+ +| Target | ENV Variable Settings| Notes | +| | | | ++==================+======================+======================================================================================+ +| foo | bar | mumble | ++------------------+----------------------+--------------------------------------------------------------------------------------+ +| bootstrap-tools | none | Builds the set of native tools needed by the vpp build system to | +| | | build images. Example: vppapigen. In a full cross compilation case might include | +| | | include "make", "git", "find", and "tar | ++------------------+----------------------+--------------------------------------------------------------------------------------+ +| install-tools | PLATFORM | Builds the tool chain for the indicated <platform>. Not used in vpp builds | ++------------------+----------------------+--------------------------------------------------------------------------------------+ +| distclean | none | Roto-rooters everything in sight: toolchains, images, and so forth. | ++------------------+----------------------+--------------------------------------------------------------------------------------+ +| install-deb | PLATFORM and TAG | Build Debian packages comprising components listed in <platform>_root_packages, | +| | | using compile / link options defined by TAG. | ++------------------+----------------------+--------------------------------------------------------------------------------------+ +| install-rpm | PLATFORM and TAG | Build RPMs comprising components listed in <platform>_root_packages, | +| | | using compile / link options defined by TAG. | ++------------------+----------------------+--------------------------------------------------------------------------------------+ + +Additional build-root/Makefile environment variable settings +------------------------------------------------------------ + +These variable settings may be of use: + ++----------------------+------------------------------------------------------------------------------------------------------------+ +| ENV Variable | Notes | ++======================+======================+=====================================================================================+ +| BUILD_DEBUG=vx | Directs Makefile et al. to make a good-faith effort to show what's going on in excruciating detail. | +| | Use it as follows: "make ... BUILD_DEBUG=vx". Fairly effective in Makefile debug situations. | ++----------------------+------------------------------------------------------------------------------------------------------------+ +| V=1 | print detailed cc / ld command lines. Useful for discovering if -DFOO=11 is in the command line or not | ++----------------------+------------------------------------------------------------------------------------------------------------+ +| CC=mygcc | Override the configured C-compiler | ++----------------------+------------------------------------------------------------------------------------------------------------+ + +.../build-root/config.site +-------------------------- + +The contents of .../build-root/config.site override individual autoconf / +automake default variable settings. Here are a few sample settings related to +building a full toolchain: + +:: + + # glibc needs these setting for cross compiling + libc_cv_forced_unwind=yes + libc_cv_c_cleanup=yes + libc_cv_ssp=no + +Determining the set of variables which need to be overridden, and the +override values is a matter of trial and error. It should be +unnecessary to modify this file for use with fd.io vpp. + +.../build-data/platforms.mk +--------------------------- + +Each repo group includes the platforms.mk file, which is included by +the main Makefile. The vpp/build-data/platforms.mk file is not terribly +complex. As of this writing, .../build-data/platforms.mk file accomplishes two +tasks. + +First, it includes vpp/build-data/platforms/\*.mk: + +:: + + # Pick up per-platform makefile fragments + $(foreach d,$(SOURCE_PATH_BUILD_DATA_DIRS), \ + $(eval -include $(d)/platforms/*.mk)) + +This collects the set of platform definition makefile fragments, as discussed above. + +Second, platforms.mk implements the user-visible "install-deb" target. + +.../build-data/packages/\*.mk +----------------------------- + +Each component needs a makefile fragment in order for the build system +to recognize it. The per-component makefile fragments vary +considerably in complexity. For a component built with GNU autoconf / +automake which does not depend on other components, the make fragment +can be empty. See .../build-data/packages/vpp.mk for an uncomplicated +but fully realistic example. + +Here are some of the important variable settings in per-component makefile fragments: + ++----------------------+------------------------------------------------------------------------------------------------------------+ +| Variable | Notes | ++======================+======================+=====================================================================================+ +| xxx_configure_depend | Lists the set of component build dependencies for the xxx component. In plain English: don't try to | +| | configure this component until you've successfully built the indicated targets. Almost always, | +| | xxx_configure_depend will list a set of "yyy-install" targets. Note the pattern: | +| | "variable names contain underscores, make target names contain hyphens" | ++----------------------+------------------------------------------------------------------------------------------------------------+ +| xxx_configure_args | (optional) Lists any additional arguments to pass to the xxx component "configure" script. | +| | The main Makefile %-configure rule adds the required settings for --libdir, --prefix, and | +| | --host (when cross-compiling) | ++----------------------+------------------------------------------------------------------------------------------------------------+ +| xxx_CPPFLAGS | Adds -I stanzas to CPPFLAGS for components upon which xxx depends. | +| | Almost invariably "xxx_CPPFLAGS = $(call installed_includes_fn, dep1 dep2 dep3)", where dep1, dep2, and | +| | dep3 are listed in xxx_configure_depend. It is bad practice to set "-g -O3" here. Those settings | +| | belong in a TAG. | ++----------------------+------------------------------------------------------------------------------------------------------------+ +| xxx_LDFLAGS | Adds -Wl,-rpath -Wl,depN stanzas to LDFLAGS for components upon which xxx depends. | +| | Almost invariably "xxx_LDFLAGS = $(call installed_lib_fn, dep1 dep2 dep3)", where dep1, dep2, and | +| | dep3 are listed in xxx_configure_depend. It is bad manners to set "-liberty-or-death" here. | +| | Those settings belong in Makefile.am. | ++----------------------+------------------------------------------------------------------------------------------------------------+ + +When dealing with "irritating" components built with raw Makefiles +which only work when building in the source tree, we use a specific +strategy in the xxx.mk file. + +The strategy is simple for those components: We copy the source tree +into .../vpp/build-root/build-xxx. This works, but completely defeats +dependency processing. This strategy is acceptable only for 3rd party +software which won't need extensive (or preferably any) modifications. + +Take a look at .../vpp/build-data/packages/dpdk.mk. When invoked, the +dpdk_configure variable copies source code into $(PACKAGE_BUILD_DIR), +and performs the BSD equivalent of "autoreconf -i -f" to configure the +build area. The rest of the file is similar: a bunch of hand-rolled +glue code which manages to make the dpdk act like a good vpp build +citizen even though it is not. |