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Quentin Monnet f0cf642c56 bpftool: Probe for memcg-based accounting before bumping rlimit
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] commit 97306be45f ("Merge branch 'switch to memcg-based memory accounting'")
  [1] commit a777e18f1b ("bpftool: Use libbpf 1.0 API mode instead of RLIMIT_MEMLOCK")
  [2] commit 6b4384ff10 ("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
2022-06-29 23:33:02 +02:00
arch bpf: per-cgroup lsm flavor 2022-06-29 13:21:51 -07:00
block block: remove bioset_init_from_src 2022-06-08 14:04:14 -04:00
certs certs: fix and refactor CONFIG_SYSTEM_BLACKLIST_HASH_LIST build 2022-06-15 21:52:32 +03:00
crypto This update includes the following changes: 2022-05-27 18:06:49 -07:00
Documentation bpf, docs: Fix the code formatting in instruction-set 2022-06-24 13:58:32 -07:00
drivers mlxsw: reg: Add support for VLAN RIF as part of RITR register 2022-06-20 10:03:34 +01:00
fs fs.fixes.v5.19-rc3 2022-06-15 09:04:55 -07:00
include bpf: expose bpf_{g,s}etsockopt to lsm cgroup 2022-06-29 13:21:52 -07:00
init gcc-12: disable '-Warray-bounds' universally for now 2022-06-09 10:11:12 -07:00
ipc These changes update the ipc sysctls so that they are fundamentally 2022-06-03 15:54:57 -07:00
kernel bpf: expose bpf_{g,s}etsockopt to lsm cgroup 2022-06-29 13:21:52 -07:00
lib test_bpf: fix incorrect netdev features 2022-06-22 19:20:20 -07:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm usercopy: Make usercopy resilient against ridiculously large copies 2022-06-13 09:54:52 -07:00
net bpf: expose bpf_{g,s}etsockopt to lsm cgroup 2022-06-29 13:21:52 -07:00
samples samples/bpf: fixup some tools to be able to support xdp multibuffer 2022-06-21 18:55:53 -07:00
scripts Merge https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next 2022-06-17 19:35:19 -07:00
security KEYS: trusted: tpm2: Fix migratable logic 2022-06-08 14:12:13 +03:00
sound sound fixes for 5.19-rc2 2022-06-10 10:20:57 -07:00
tools bpftool: Probe for memcg-based accounting before bumping rlimit 2022-06-29 23:33:02 +02:00
usr Not a lot of material this cycle. Many singleton patches against various 2022-05-27 11:22:03 -07:00
virt KVM: x86: disable preemption around the call to kvm_arch_vcpu_{un|}blocking 2022-06-09 10:52:20 -04:00
.clang-format clang-format: Fix space after for_each macros 2022-05-20 19:27:16 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore kbuild: split the second line of *.mod into *.usyms 2022-05-08 03:16:59 +09:00
.mailmap Hot fixes for 5.19-rc1. 2022-06-05 17:05:38 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: replace a Microchip AT91 maintainer 2022-02-09 11:30:01 +01:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2022-06-16 20:13:52 -07:00
Makefile Linux 5.19-rc2 2022-06-12 16:11:37 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.