| Message ID | 20210126161320.24561-1-quentin@isovalent.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 150a27328b681425c8cab239894a48f2aeb870e9 |
| Delegated to: | BPF |
| Headers | show |
| Series | [bpf,v2] bpf: fix build for BPF preload when $(O) points to a relative path | expand |
| Context | Check | Description |
|---|---|---|
| netdev/cover_letter | success | Link |
| netdev/fixes_present | fail | Series targets non-next tree, but doesn't contain any Fixes tags |
| netdev/patch_count | success | Link |
| netdev/tree_selection | success | Clearly marked for bpf |
| netdev/subject_prefix | success | Link |
| netdev/cc_maintainers | warning | 7 maintainers not CCed: toke@redhat.com songliubraving@fb.com andrii@kernel.org kpsingh@kernel.org john.fastabend@gmail.com kafai@fb.com yhs@fb.com |
| netdev/source_inline | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Link |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/build_32bit | success | Errors and warnings before: 0 this patch: 0 |
| netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| netdev/verify_fixes | success | Link |
| netdev/checkpatch | warning | WARNING: use relative pathname instead of absolute in changelog text |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 0 this patch: 0 |
| netdev/header_inline | success | Link |
| netdev/stable | success | Stable not CCed |
Hello: This patch was applied to bpf/bpf.git (refs/heads/master): On Tue, 26 Jan 2021 16:13:20 +0000 you wrote: > Building the kernel with CONFIG_BPF_PRELOAD, and by providing a relative > path for the output directory, may fail with the following error: > > $ make O=build bindeb-pkg > ... > /.../linux/tools/scripts/Makefile.include:5: *** O=build does not exist. Stop. > make[7]: *** [/.../linux/kernel/bpf/preload/Makefile:9: kernel/bpf/preload/libbpf.a] Error 2 > make[6]: *** [/.../linux/scripts/Makefile.build:500: kernel/bpf/preload] Error 2 > make[5]: *** [/.../linux/scripts/Makefile.build:500: kernel/bpf] Error 2 > make[4]: *** [/.../linux/Makefile:1799: kernel] Error 2 > make[4]: *** Waiting for unfinished jobs.... > > [...] Here is the summary with links: - [bpf,v2] bpf: fix build for BPF preload when $(O) points to a relative path https://git.kernel.org/bpf/bpf/c/150a27328b68 You are awesome, thank you! -- Deet-doot-dot, I am a bot. https://korg.docs.kernel.org/patchwork/pwbot.html
diff --git a/kernel/bpf/preload/Makefile b/kernel/bpf/preload/Makefile index 23ee310b6eb4..1951332dd15f 100644 --- a/kernel/bpf/preload/Makefile +++ b/kernel/bpf/preload/Makefile @@ -4,8 +4,11 @@ LIBBPF_SRCS = $(srctree)/tools/lib/bpf/ LIBBPF_A = $(obj)/libbpf.a LIBBPF_OUT = $(abspath $(obj)) +# Although not in use by libbpf's Makefile, set $(O) so that the "dummy" test +# in tools/scripts/Makefile.include always succeeds when building the kernel +# with $(O) pointing to a relative path, as in "make O=build bindeb-pkg". $(LIBBPF_A): - $(Q)$(MAKE) -C $(LIBBPF_SRCS) OUTPUT=$(LIBBPF_OUT)/ $(LIBBPF_OUT)/libbpf.a + $(Q)$(MAKE) -C $(LIBBPF_SRCS) O=$(LIBBPF_OUT)/ OUTPUT=$(LIBBPF_OUT)/ $(LIBBPF_OUT)/libbpf.a userccflags += -I $(srctree)/tools/include/ -I $(srctree)/tools/include/uapi \ -I $(srctree)/tools/lib/ -Wno-unused-result
Building the kernel with CONFIG_BPF_PRELOAD, and by providing a relative path for the output directory, may fail with the following error: $ make O=build bindeb-pkg ... /.../linux/tools/scripts/Makefile.include:5: *** O=build does not exist. Stop. make[7]: *** [/.../linux/kernel/bpf/preload/Makefile:9: kernel/bpf/preload/libbpf.a] Error 2 make[6]: *** [/.../linux/scripts/Makefile.build:500: kernel/bpf/preload] Error 2 make[5]: *** [/.../linux/scripts/Makefile.build:500: kernel/bpf] Error 2 make[4]: *** [/.../linux/Makefile:1799: kernel] Error 2 make[4]: *** Waiting for unfinished jobs.... In the case above, for the "bindeb-pkg" target, the error is produced by the "dummy" check in Makefile.include, called from libbpf's Makefile. This check changes directory to $(PWD) before checking for the existence of $(O). But at this step we have $(PWD) pointing to "/.../linux/build", and $(O) pointing to "build". So the Makefile.include tries in fact to assert the existence of a directory named "/.../linux/build/build", which does not exist. Note that the error does not occur for all make targets and architectures combinations. This was observed on x86 for "bindeb-pkg", or for a regular build for UML [0]. Here are some details. The root Makefile recursively calls itself once, after changing directory to $(O). The content for the variable $(PWD) is preserved across recursive calls to make, so it is unchanged at this step. For "bindeb-pkg", $(PWD) is eventually updated because the target writes a new Makefile (as debian/rules) and calls it indirectly through dpkg-buildpackage. This script does not preserve $(PWD), which is reset to the current working directory when the target in debian/rules is called. Although not investigated, it seems likely that something similar causes UML to change its value for $(PWD). Non-trivial fixes could be to remove the use of $(PWD) from the "dummy" check, or to make sure that $(PWD) and $(O) are preserved or updated to always play well and form a valid $(PWD)/$(O) path across the different targets and architectures. Instead, we take a simpler approach and just update $(O) when calling libbpf's Makefile, so it points to an absolute path which should always resolve for the "dummy" check run (through includes) by that Makefile. David Gow previously posted a slightly different version of this patch as a RFC [0], two months ago or so. [0] https://lore.kernel.org/bpf/20201119085022.3606135-1-davidgow@google.com/t/#u v2: Use $(LIBBPF_OUT) instead of $(abspath .), and improve commit log Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com> Cc: Brendan Higgins <brendanhiggins@google.com> Cc: David Gow <davidgow@google.com> Cc: Masahiro Yamada <masahiroy@kernel.org> Reported-by: David Gow <davidgow@google.com> Signed-off-by: Quentin Monnet <quentin@isovalent.com> --- kernel/bpf/preload/Makefile | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)