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linux-next/kernel/bpf/Kconfig
Paul E. McKenney 835f14ed53 rcu: Make the TASKS_RCU Kconfig option be selected
Currently, any kernel built with CONFIG_PREEMPTION=y also gets
CONFIG_TASKS_RCU=y, which is not helpful to people trying to build
preemptible kernels of minimal size.

Because CONFIG_TASKS_RCU=y is needed only in kernels doing tracing of
one form or another, this commit moves from TASKS_RCU deciding when it
should be enabled to the tracing Kconfig options explicitly selecting it.
This allows building preemptible kernels without TASKS_RCU, if desired.

This commit also updates the SRCU-N and TREE09 rcutorture scenarios
in order to avoid Kconfig errors that would otherwise result from
CONFIG_TASKS_RCU being selected without its CONFIG_RCU_EXPERT dependency
being met.

[ paulmck: Apply BPF_SYSCALL feedback from Andrii Nakryiko. ]

Reported-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Tested-by: Zhouyi Zhou <zhouzhouyi@gmail.com>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2022-04-20 16:52:58 -07:00

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# SPDX-License-Identifier: GPL-2.0-only
# BPF interpreter that, for example, classic socket filters depend on.
config BPF
bool
# Used by archs to tell that they support BPF JIT compiler plus which
# flavour. Only one of the two can be selected for a specific arch since
# eBPF JIT supersedes the cBPF JIT.
# Classic BPF JIT (cBPF)
config HAVE_CBPF_JIT
bool
# Extended BPF JIT (eBPF)
config HAVE_EBPF_JIT
bool
# Used by archs to tell that they want the BPF JIT compiler enabled by
# default for kernels that were compiled with BPF JIT support.
config ARCH_WANT_DEFAULT_BPF_JIT
bool
menu "BPF subsystem"
config BPF_SYSCALL
bool "Enable bpf() system call"
select BPF
select IRQ_WORK
select TASKS_RCU if PREEMPTION
select TASKS_TRACE_RCU
select BINARY_PRINTF
select NET_SOCK_MSG if NET
select PAGE_POOL if NET
default n
help
Enable the bpf() system call that allows to manipulate BPF programs
and maps via file descriptors.
config BPF_JIT
bool "Enable BPF Just In Time compiler"
depends on BPF
depends on HAVE_CBPF_JIT || HAVE_EBPF_JIT
depends on MODULES
help
BPF programs are normally handled by a BPF interpreter. This option
allows the kernel to generate native code when a program is loaded
into the kernel. This will significantly speed-up processing of BPF
programs.
Note, an admin should enable this feature changing:
/proc/sys/net/core/bpf_jit_enable
/proc/sys/net/core/bpf_jit_harden (optional)
/proc/sys/net/core/bpf_jit_kallsyms (optional)
config BPF_JIT_ALWAYS_ON
bool "Permanently enable BPF JIT and remove BPF interpreter"
depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT
help
Enables BPF JIT and removes BPF interpreter to avoid speculative
execution of BPF instructions by the interpreter.
When CONFIG_BPF_JIT_ALWAYS_ON is enabled, /proc/sys/net/core/bpf_jit_enable
is permanently set to 1 and setting any other value than that will
return failure.
config BPF_JIT_DEFAULT_ON
def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON
depends on HAVE_EBPF_JIT && BPF_JIT
config BPF_UNPRIV_DEFAULT_OFF
bool "Disable unprivileged BPF by default"
default y
depends on BPF_SYSCALL
help
Disables unprivileged BPF by default by setting the corresponding
/proc/sys/kernel/unprivileged_bpf_disabled knob to 2. An admin can
still reenable it by setting it to 0 later on, or permanently
disable it by setting it to 1 (from which no other transition to
0 is possible anymore).
Unprivileged BPF could be used to exploit certain potential
speculative execution side-channel vulnerabilities on unmitigated
affected hardware.
If you are unsure how to answer this question, answer Y.
source "kernel/bpf/preload/Kconfig"
config BPF_LSM
bool "Enable BPF LSM Instrumentation"
depends on BPF_EVENTS
depends on BPF_SYSCALL
depends on SECURITY
depends on BPF_JIT
help
Enables instrumentation of the security hooks with BPF programs for
implementing dynamic MAC and Audit Policies.
If you are unsure how to answer this question, answer N.
endmenu # "BPF subsystem"