3ac58492b3
With this patch, it is now possible to generate coverage information for MINIX3 system services with LLVM. In particular, the system can be built with MKCOVERAGE=yes, either with a native "make build" or with crosscompilation. Either way, MKCOVERAGE=yes will build the MINIX3 system services with coverage profiling support, generating a .gcno file for each source module. After a reboot it is possible to obtain runtime coverage data (.gcda files) for individual system services using gcov-pull(8). The combination of the .gcno and .gcda files can then be inspected with llvm-cov(1). For reasons documented in minix.gcov.mk, only system service program modules are supported for now; system service libraries (libsys etc.) are not included. Userland programs are not affected by MKCOVERAGE. The heart of this patch is the libsys code that writes data generated by the LLVM coverage hooks into a serialized format using the routines we already had for GCC GCOV. Unfortunately, the new llvm_gcov.c code is LLVM ABI dependent, and may therefore have to be updated later when we upgrade LLVM. The current implementation should support all LLVM versions 3.x with x >= 4. The rest of this patch is mostly a light cleanup of our existing GCOV infrastructure, with as most visible change that gcov-pull(8) now takes a service label string rather than a PID number. Change-Id: I6de055359d3d2b3f53e426f3fffb17af7877261f
52 lines
2.6 KiB
Makefile
52 lines
2.6 KiB
Makefile
LCOV=lcov.$(PROG)
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CLEANFILES+= *.gcno *.gcda $(LCOV)
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# Right now we support obtaining coverage information for system services only,
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# and for their main program code (not including their libraries) only.
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#
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# Why not userland as well: because we do not care as much, and it should be
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# possible to produce coverage information for system services without
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# recompiling the entire system with coverage support. Moreover, as of writing
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# we do not have libprofile_rt, making it impossible to compile regular
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# programs with coverage support altogether.
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#
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# Why not system service libraries (eg libsys) as well: practical concerns..
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# 1) As of writing, even for such libraries we make a regular and a PIC
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# version, both producing a .gcno file for each object. The PIC version is
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# compiled last, while the regular version is used for the library archive.
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# The result is a potential mismatch between the compile-time coverage
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# metadata and the run-time coverage counts.
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# 2) The kernel has no coverage support, and with its self-relocation it would
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# be tricky to add support for it. As a result, libraries used by the
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# kernel would have to be excluded from being compiled with coverage support
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# so as not to create problems. One could argue that that is a good thing
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# because eg libminc and libsys create too many small result units (see also
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# the current hardcoded limit in libsys/llvm_gcov.c).
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# 3) gcov-pull(8) strips paths, which results in lots of manual work to figure
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# out what file belongs to which library, even ignoring object name
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# conflicts, for example between libraries.
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# 4) In order to produce practically useful results ("how much of libsockevent
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# is covered by the combination of LWIP and UDS" etc), gcov-pull(8) would
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# have to be extended with support for merging .gcda files. The standard
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# LLVM libprofile_rt implementation supports this, but we do not.
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# All of these issues are solvable, but for now anyone interested in coverage
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# for a particular system service library will have to mess with individual
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# makefiles themselves.
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.if ${MKCOVERAGE:Uno} == "yes"
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.if ${ACTIVE_CC} == "gcc"
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# Leftovers for GCC. It is not clear whether these still work at all.
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COVCPPFLAGS?= -fno-builtin -fprofile-arcs -ftest-coverage
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COVLDADD?= -lgcov
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.else # ${ACTIVE_CC} != "gcc"
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# We assume LLVM/clang here. For other compilers this will likely break the
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# MKCOVERAGE compilation, which is a good indication that support for them
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# should be added here.
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COVCPPFLAGS?= --coverage -g -O0
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COVLDADD?=
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.endif # ${ACTIVE_CC} != "gcc"
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.endif # ${MKCOVERAGE:Uno} == "yes"
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lcov:
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lcov -c -d . >$(LCOV)
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