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Subject[PATCH bpf-next v2 2/2] bpf: Make BPF_JIT_DEFAULT_ON selectable in Kconfig
Date
Currently, only x86, arm64 and s390 select ARCH_WANT_DEFAULT_BPF_JIT,
the other archs do not select ARCH_WANT_DEFAULT_BPF_JIT. On the archs
without ARCH_WANT_DEFAULT_BPF_JIT, if we want to set bpf_jit_enable to
1 by default, the only way is to enable CONFIG_BPF_JIT_ALWAYS_ON, then
the users can not change it to 0 or 2, it seems bad for some users. We
can select ARCH_WANT_DEFAULT_BPF_JIT for those archs if it is proper,
but at least for now, make BPF_JIT_DEFAULT_ON selectable can give them
a chance.

Additionally, with this patch, under !BPF_JIT_ALWAYS_ON, we can disable
BPF_JIT_DEFAULT_ON on the archs with ARCH_WANT_DEFAULT_BPF_JIT when make
menuconfig, it seems flexible for some developers.

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---
kernel/bpf/Kconfig | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/Kconfig b/kernel/bpf/Kconfig
index cbf3f65..461ac60 100644
--- a/kernel/bpf/Kconfig
+++ b/kernel/bpf/Kconfig
@@ -54,6 +54,7 @@ config BPF_JIT
config BPF_JIT_ALWAYS_ON
bool "Permanently enable BPF JIT and remove BPF interpreter"
depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT
+ select BPF_JIT_DEFAULT_ON
help
Enables BPF JIT and removes BPF interpreter to avoid speculative
execution of BPF instructions by the interpreter.
@@ -63,8 +64,16 @@ config BPF_JIT_ALWAYS_ON
in failure.

config BPF_JIT_DEFAULT_ON
- def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON
- depends on HAVE_EBPF_JIT && BPF_JIT
+ bool "Defaultly enable BPF JIT and remove BPF interpreter"
+ default y if ARCH_WANT_DEFAULT_BPF_JIT
+ 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_DEFAULT_ON is enabled but CONFIG_BPF_JIT_ALWAYS_ON
+ is disabled, /proc/sys/net/core/bpf_jit_enable is set to 1 by default
+ and can be changed to 0 or 2.

config BPF_UNPRIV_DEFAULT_OFF
bool "Disable unprivileged BPF by default"
--
2.1.0
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