Andrii Nakryiko a67079b031 selftests/bpf: fix bpf_testmod.ko recompilation logic
bpf_testmod.ko build rule declared dependency on VMLINUX_BTF, but the variable
itself was initialized after the rule was declared, which often caused
bpf_testmod.ko to not be re-compiled. Fix by moving VMLINUX_BTF determination
sooner.

Also enforce bpf_testmod.ko recompilation when we detect that vmlinux image
changed by removing bpf_testmod/bpf_testmod.ko. This is necessary to generate
correct module's split BTF. Without it, Kbuild's module build logic might
determine that nothing changed on the kernel side and thus bpf_testmod.ko
shouldn't be rebuilt, so won't re-generate module BTF, which often leads to
module's BTF with wrong string offsets against vmlinux BTF. Removing .ko file
forces Kbuild to re-build the module.

Reported-by: Alexei Starovoitov <ast@kernel.org>
Fixes: 9f7fa22589 ("selftests/bpf: Add bpf_testmod kernel module for testing")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20201211015946.4062098-1-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2020-12-10 21:16:29 -08:00
2020-11-29 15:50:50 -08:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.
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