Re: [PATCH bpf-next v2 2/2] bpf: Make BPF_JIT_DEFAULT_ON selectable in Kconfig
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From: Song Liu <song@kernel.org>
Date: 2022-02-22 02:14:39
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bpf, lkml
On Fri, Feb 18, 2022 at 7:15 PM Tiezhu Yang [off-list ref] wrote:
quoted hunk ↗ jump to hunk
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"
I think "remove BPF interpreter" is not accurate. I guess we can just say "Enable BPF JIT by default". (also "defaultly" sounds weird to me).
+ 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