feat: use cache kernel build output #694
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Use cache for kernel build output and re-use in downstream steps. Signed-off-by: Noel Georgi <[email protected]>
| cp -v /pkg/certs/* certs/ | ||
| build: | ||
| - | | ||
| cd /src | ||
| python3 /toolchain/kconfig-hardened-check/bin/kconfig-hardened-check -c .config -m json | python3 /pkg/scripts/filter-hardened-check.py | ||
| python3 /toolchain/kconfig-hardened-check/bin/kconfig-hardened-check -c ${KBUILD_OUTPUT}/.config -m json | python3 /pkg/scripts/filter-hardened-check.py |
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my concern is how can we be sure that the cache gets properly invalidated? I guess in default make, it's all timestamp-based, so if we have two kernel builds from different branches, it may very well poison the cache?
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The src folder gets changed, but the kernel build objects can still be re-used. I don;t want this going in release-1.4 anyways, targetting for 1.5
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yes, I understand that, but my point is the following, the Makefile is something like:
/src/build/foo.o: /src/foo.c
cc -o /src/build/foo.o /src/foo.cSo what make does is that it compares the timestamps of .c and .o files: if .o is newer, it skips the build
But this is not reliable enough given that we have multiple branches/versions of the kernel, and timestamp for Linux 5.15.x and 6.1.x might be inverted.
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I think the kernel build is intelligent enough to detect that, based on the source. At least when building locally, but I'ven't tried changing versions 😅 . I'll test locally later
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if there's some smartness, let's find some proof on that :) it's definitely not in make itself
Use cache for kernel build output and re-use in downstream steps.