diff options
Diffstat (limited to 'Documentation/sysctl/net.txt')
| -rw-r--r-- | Documentation/sysctl/net.txt | 47 |
1 files changed, 36 insertions, 11 deletions
diff --git a/Documentation/sysctl/net.txt b/Documentation/sysctl/net.txt index 14db18c970b1..b67044a2575f 100644 --- a/Documentation/sysctl/net.txt +++ b/Documentation/sysctl/net.txt @@ -35,9 +35,34 @@ Table : Subdirectories in /proc/sys/net bpf_jit_enable -------------- -This enables Berkeley Packet Filter Just in Time compiler. -Currently supported on x86_64 architecture, bpf_jit provides a framework -to speed packet filtering, the one used by tcpdump/libpcap for example. +This enables the BPF Just in Time (JIT) compiler. BPF is a flexible +and efficient infrastructure allowing to execute bytecode at various +hook points. It is used in a number of Linux kernel subsystems such +as networking (e.g. XDP, tc), tracing (e.g. kprobes, uprobes, tracepoints) +and security (e.g. seccomp). LLVM has a BPF back end that can compile +restricted C into a sequence of BPF instructions. After program load +through bpf(2) and passing a verifier in the kernel, a JIT will then +translate these BPF proglets into native CPU instructions. There are +two flavors of JITs, the newer eBPF JIT currently supported on: + - x86_64 + - arm64 + - arm32 + - ppc64 + - sparc64 + - mips64 + - s390x + +And the older cBPF JIT supported on the following archs: + - mips + - ppc + - sparc + +eBPF JITs are a superset of cBPF JITs, meaning the kernel will +migrate cBPF instructions into eBPF instructions and then JIT +compile them transparently. Older cBPF JITs can only translate +tcpdump filters, seccomp rules, etc, but not mentioned eBPF +programs loaded through bpf(2). + Values : 0 - disable the JIT (default value) 1 - enable the JIT @@ -46,9 +71,9 @@ Values : bpf_jit_harden -------------- -This enables hardening for the Berkeley Packet Filter Just in Time compiler. -Supported are eBPF JIT backends. Enabling hardening trades off performance, -but can mitigate JIT spraying. +This enables hardening for the BPF JIT compiler. Supported are eBPF +JIT backends. Enabling hardening trades off performance, but can +mitigate JIT spraying. Values : 0 - disable JIT hardening (default value) 1 - enable JIT hardening for unprivileged users only @@ -57,11 +82,11 @@ Values : bpf_jit_kallsyms ---------------- -When Berkeley Packet Filter Just in Time compiler is enabled, then compiled -images are unknown addresses to the kernel, meaning they neither show up in -traces nor in /proc/kallsyms. This enables export of these addresses, which -can be used for debugging/tracing. If bpf_jit_harden is enabled, this feature -is disabled. +When BPF JIT compiler is enabled, then compiled images are unknown +addresses to the kernel, meaning they neither show up in traces nor +in /proc/kallsyms. This enables export of these addresses, which can +be used for debugging/tracing. If bpf_jit_harden is enabled, this +feature is disabled. Values : 0 - disable JIT kallsyms export (default value) 1 - enable JIT kallsyms export for privileged users only |