Remove information about bpf_jit_enable=2 mode and added description for how to use the bpf_jit_disasm tool after get rid of =2 mode. Signed-off-by: Jianlin Lv <Jianlin.Lv@xxxxxxx> --- Documentation/admin-guide/sysctl/net.rst | 1 - Documentation/networking/filter.rst | 25 ++++++------------------ 2 files changed, 6 insertions(+), 20 deletions(-) diff --git a/Documentation/admin-guide/sysctl/net.rst b/Documentation/admin-guide/sysctl/net.rst index c941b214e0b7..a39f99deac38 100644 --- a/Documentation/admin-guide/sysctl/net.rst +++ b/Documentation/admin-guide/sysctl/net.rst @@ -86,7 +86,6 @@ Values: - 0 - disable the JIT (default value) - 1 - enable the JIT - - 2 - enable the JIT and ask the compiler to emit traces on kernel log. bpf_jit_harden -------------- diff --git a/Documentation/networking/filter.rst b/Documentation/networking/filter.rst index 251c6bd73d15..86954f922168 100644 --- a/Documentation/networking/filter.rst +++ b/Documentation/networking/filter.rst @@ -504,25 +504,12 @@ been previously enabled by root:: echo 1 > /proc/sys/net/core/bpf_jit_enable -For JIT developers, doing audits etc, each compile run can output the generated -opcode image into the kernel log via:: - - echo 2 > /proc/sys/net/core/bpf_jit_enable - -Example output from dmesg:: - - [ 3389.935842] flen=6 proglen=70 pass=3 image=ffffffffa0069c8f - [ 3389.935847] JIT code: 00000000: 55 48 89 e5 48 83 ec 60 48 89 5d f8 44 8b 4f 68 - [ 3389.935849] JIT code: 00000010: 44 2b 4f 6c 4c 8b 87 d8 00 00 00 be 0c 00 00 00 - [ 3389.935850] JIT code: 00000020: e8 1d 94 ff e0 3d 00 08 00 00 75 16 be 17 00 00 - [ 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. +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. +For debugging JITs, the introspection through bpftool (tools/bpf/bpftool/) +is the generally recommended approach instead. For JIT developers, doing +audits etc, you can insert bpf_jit_dump() and recompile the kernel to +output the generated opcode image into the kernel log. In the kernel source tree under tools/bpf/, there's bpf_jit_disasm for generating disassembly out of the kernel log's hexdump:: -- 2.25.1
