When CONFIG_BPF_JIT_ALWAYS_ON is enabled, kernel has limitation for bpf_jit_enable, so it has fixed value 1 and we cannot set it to 2 for JIT opcode dumping; this patch is to update the doc for it.
Suggested-by: Daniel Borkmann <dan...@iogearbox.net> Signed-off-by: Leo Yan <leo....@linaro.org> --- Documentation/networking/filter.txt | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/Documentation/networking/filter.txt b/Documentation/networking/filter.txt index fd55c7d..5032e12 100644 --- a/Documentation/networking/filter.txt +++ b/Documentation/networking/filter.txt @@ -483,6 +483,12 @@ Example output from dmesg: [ 3389.935851] JIT code: 00000030: 00 e8 28 94 ff e0 83 f8 01 75 07 b8 ff ff 00 00 [ 3389.935852] JIT code: 00000040: eb 02 31 c0 c9 c3 +When CONFIG_BPF_JIT_ALWAYS_ON is enabled, bpf_jit_enable is permanently set to 1 and +setting any other value than that will return in failure. This is even the case for +setting bpf_jit_enable to 2, since dumping the final JIT image into the kernel log +is discouraged and introspection through bpftool (under tools/bpf/bpftool/) is the +generally recommended approach instead. + In the kernel source tree under tools/bpf/, there's bpf_jit_disasm for generating disassembly out of the kernel log's hexdump: -- 1.9.1
