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Andrii Nakryiko says: ==================== Add support for using kernel module global variables (__ksym externs in BPF program). BPF verifier will now support ldimm64 with src_reg=BPF_PSEUDO_BTF_ID and non-zero insn[1].imm field, specifying module BTF's FD. In such case, module BTF object, similarly to BPF maps referenced from ldimm64 with src_reg=BPF_PSEUDO_MAP_FD, will be recorded in bpf_progran's auxiliary data and refcnt will be increased for both BTF object itself and its kernel module. This makes sure kernel module won't be unloaded from under active attached BPF program. These refcounts will be dropped when BPF program is unloaded. New selftest validates all this is working as intended. bpf_testmod.ko is extended with per-CPU variable. Selftests expects the latest pahole changes (soon to be released as v1.20) to generate per-CPU variable BTF info for kernel module. v2->v3: - added comments, addressed feedack (Yonghong, Hao); v1->v2: - fixed few compiler warnings, posted as separate pre-patches; rfc->v1: - use sys_membarrier(MEMBARRIER_CMD_GLOBAL) (Alexei). Cc: Hao Luo <haoluo@google.com> ==================== Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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.