mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2026-05-02 16:55:16 -04:00
f0cf642c56
Bpftool used to bump the memlock rlimit to make sure to be able to load BPF objects. After the kernel has switched to memcg-based memory accounting [0] in 5.11, bpftool has relied on libbpf to probe the system for memcg-based accounting support and for raising the rlimit if necessary [1]. But this was later reverted, because the probe would sometimes fail, resulting in bpftool not being able to load all required objects [2]. Here we add a more efficient probe, in bpftool itself. We first lower the rlimit to 0, then we attempt to load a BPF object (and finally reset the rlimit): if the load succeeds, then memcg-based memory accounting is supported. This approach was earlier proposed for the probe in libbpf itself [3], but given that the library may be used in multithreaded applications, the probe could have undesirable consequences if one thread attempts to lock kernel memory while memlock rlimit is at 0. Since bpftool is single-threaded and the rlimit is process-based, this is fine to do in bpftool itself. This probe was inspired by the similar one from the cilium/ebpf Go library [4]. [0] commit97306be45f("Merge branch 'switch to memcg-based memory accounting'") [1] commita777e18f1b("bpftool: Use libbpf 1.0 API mode instead of RLIMIT_MEMLOCK") [2] commit6b4384ff10("Revert "bpftool: Use libbpf 1.0 API mode instead of RLIMIT_MEMLOCK"") [3] https://lore.kernel.org/bpf/20220609143614.97837-1-quentin@isovalent.com/t/#u [4] https://github.com/cilium/ebpf/blob/v0.9.0/rlimit/rlimit.go#L39 Suggested-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Quentin Monnet <quentin@isovalent.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Reviewed-by: Stanislav Fomichev <sdf@google.com> Acked-by: Yafang Shao <laoar.shao@gmail.com> Link: https://lore.kernel.org/bpf/20220629111351.47699-1-quentin@isovalent.com
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.