tools build: Incorrect fixdep dependencies #7287
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Upstream branch: 03922e9 |
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At least one diff in series https://patchwork.kernel.org/project/netdevbpf/list/?series=867329 expired. Closing PR. |
All built targets need fixdep to be built first, before handling object dependencies [1]. We're missing one such dependency before the libsubcmd target. This resolves .cmd file generation issues such that the following sequence produces many fewer results: $ git clean -xfd tools/ $ make tools/objtool $ grep "cannot find fixdep" $(find tools/objtool -name '*.cmd') In particular, only a buggy tools/objtool/libsubcmd/.fixdep.o.cmd remains, due to circular dependencies of fixdep on itself. Such incomplete .cmd files don't usually cause a direct problem, since they're designed to fail "open", but they can cause some subtle problems that would otherwise be handled by proper fixdep'd dependency files. [1] This problem is better described in commit abb2621 ("perf tools: Force fixdep compilation at the start of the build"). I don't apply its solution here, because additional recursive make can be a bit of overkill. Link: https://lore.kernel.org/all/ZGVi9HbI43R5trN8@bhelgaas/ Link: https://lore.kernel.org/all/Zk-C5Eg84yt6_nml@google.com/ Signed-off-by: Brian Norris <briannorris@chromium.org>
The 'fixdep' tool is used to post-process dependency files for various reasons, and it runs after every object file generation command. This even includes 'fixdep' itself. In Kbuild, this isn't actually a problem, because it uses a single command to generate fixdep (a compile-and-link command on fixdep.c), and afterward runs the fixdep command on the accompanying .fixdep.cmd file. In tools/ builds (which notably is maintained separately from Kbuild), fixdep is generated in several phases: 1. fixdep.c -> fixdep-in.o 2. fixdep-in.o -> fixdep Thus, fixdep is not available in the post-processing for step 1, and instead, we generate .cmd files that look like: ## from tools/objtool/libsubcmd/.fixdep.o.cmd # cannot find fixdep (/path/to/linux/tools/objtool/libsubcmd//fixdep) [...] These invalid .cmd files are benign in some respects, but cause problems in others (such as the linked reports). Because the tools/ build system is rather complicated in its own right (and pointedly different than Kbuild), I choose to simply open-code the rule for building fixdep, and avoid the recursive-make indirection that produces the problem in the first place. Link: https://lore.kernel.org/all/Zk-C5Eg84yt6_nml@google.com/ Signed-off-by: Brian Norris <briannorris@chromium.org>
The dependencies in tools/lib/bpf/Makefile are incorrect. Before we recurse to build $(BPF_IN_STATIC), we need to build its 'fixdep' executable. I can't use the usual shortcut from Makefile.include: <target>: <sources> fixdep because its 'fixdep' target relies on $(OUTPUT), and $(OUTPUT) differs in the parent 'make' versus the child 'make' -- so I imitate it via open-coding. I tweak a few $(MAKE) invocations while I'm at it, because 1. I'm adding a new recursive make; and 2. these recursive 'make's print spurious lines about files that are "up to date" (which isn't normally a feature in Kbuild subtargets) or "jobserver not available" (see [1]) I also need to tweak the assignment of the OUTPUT variable, so that relative path builds work. For example, for 'make tools/lib/bpf', OUTPUT is unset, and is usually treated as "cwd" -- but recursive make will change cwd and so OUTPUT has a new meaning. For consistency, I ensure OUTPUT is always an absolute path. And $(Q) gets a backup definition in tools/build/Makefile.include, because Makefile.include is sometimes included without tools/build/Makefile, so the "quiet command" stuff doesn't actually work consistently without it. After this change, top-level builds result in an empty grep result from: $ grep 'cannot find fixdep' $(find tools/ -name '*.cmd') [1] https://www.gnu.org/software/make/manual/html_node/MAKE-Variable.html If we're not using $(MAKE) directly, then we need to use more '+'. Signed-off-by: Brian Norris <briannorris@chromium.org>
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At least one diff in series https://patchwork.kernel.org/project/netdevbpf/list/?series=867724 irrelevant now. Closing PR. |
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Pull request for series with
subject: tools build: Incorrect fixdep dependencies
version: 1
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=867329