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authorRasmus Villemoes <linux@rasmusvillemoes.dk>2020-09-17 08:56:11 +0200
committerMasahiro Yamada <masahiroy@kernel.org>2020-09-25 02:28:12 +0900
commit548b8b5168c90c42e88f70fcf041b4ce0b8e7aa8 (patch)
tree34deb2b7b03c379bcdf9760a3cc3720c7f6cfad8 /scripts/link-vmlinux.sh
parent87de84c9140e1ccb221c68bb7e4939e880b3f2bb (diff)
scripts/setlocalversion: make git describe output more reliable
When building for an embedded target using Yocto, we're sometimes observing that the version string that gets built into vmlinux (and thus what uname -a reports) differs from the path under /lib/modules/ where modules get installed in the rootfs, but only in the length of the -gabc123def suffix. Hence modprobe always fails. The problem is that Yocto has the concept of "sstate" (shared state), which allows different developers/buildbots/etc. to share build artifacts, based on a hash of all the metadata that went into building that artifact - and that metadata includes all dependencies (e.g. the compiler used etc.). That normally works quite well; usually a clean build (without using any sstate cache) done by one developer ends up being binary identical to a build done on another host. However, one thing that can cause two developers to end up with different builds [and thus make one's vmlinux package incompatible with the other's kernel-dev package], which is not captured by the metadata hashing, is this `git describe`: The output of that can be affected by (1) git version: before 2.11 git defaulted to a minimum of 7, since 2.11 (git.git commit e6c587) the default is dynamic based on the number of objects in the repo (2) hence even if both run the same git version, the output can differ based on how many remotes are being tracked (or just lots of local development branches or plain old garbage) (3) and of course somebody could have a core.abbrev config setting in ~/.gitconfig So in order to avoid `uname -a` output relying on such random details of the build environment which are rather hard to ensure are consistent between developers and buildbots, make sure the abbreviated sha1 always consists of exactly 12 hex characters. That is consistent with the current rule for -stable patches, and is almost always enough to identify the head commit unambigously - in the few cases where it does not, the v5.4.3-00021- prefix would certainly nail it down. Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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