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. Signed-off-by: Leo Yan <leo.yan@xxxxxxxxxx> --- Documentation/networking/filter.txt | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/Documentation/networking/filter.txt b/Documentation/networking/filter.txt index fd55c7d..feddab9 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 set to 1 by default +and it returns failure if change to any other value from proc node; this is +for security consideration to avoid leaking info to unprivileged users. In this +case, we can't directly dump JIT opcode image from kernel log, alternatively we +need to use bpf tool for the dumping. + 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 -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
