1#!/usr/bin/env bcc-lua 2--[[ 3Copyright 2016 Marek Vavrusa <mvavrusa@cloudflare.com> 4 5Licensed under the Apache License, Version 2.0 (the "License"); 6you may not use this file except in compliance with the License. 7You may obtain a copy of the License at 8 9http://www.apache.org/licenses/LICENSE-2.0 10 11Unless required by applicable law or agreed to in writing, software 12distributed under the License is distributed on an "AS IS" BASIS, 13WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14See the License for the specific language governing permissions and 15limitations under the License. 16]] 17-- Trace operations on keys matching given pattern in KyotoTycoon daemon. 18-- This can show you if certain keys were modified or read during the lifetime 19-- even if KT doesn't support this. It also shows how to attach to C++ mangled symbols. 20local ffi = require('ffi') 21local bpf = require('bpf') 22local S = require('syscall') 23local function help(err) 24 print(string.format('%s [get|set] [key]', arg[0])) 25 if err then print('error: '..err) end 26 os.exit(1) 27end 28-- Accept the same format as ktremotemgr for clarity: <get|set> <key> 29local writeable, watch_key, klen = 'any', arg[2] or '*', 80 30if arg[1] == 'get' then writeable = 0 31elseif arg[1] == 'set' then writeable = 1 32elseif arg[1] == '-h' or arg[1] == '--help' then help() 33elseif arg[1] and arg[1] ~= 'any' then 34 help(string.format('bad cmd: "%s"', arg[1])) 35end 36if watch_key ~= '*' then klen = #watch_key end 37 38-- Find a good entrypoint that has both key and differentiates read/write in KT 39-- That is going to serve as an attachment point for BPF program 40-- ABI: bool accept(void *this, const char* kbuf, size_t ksiz, Visitor* visitor, bool writable) 41local key_type = string.format('char [%d]', klen) 42local probe = bpf.uprobe('/usr/local/bin/ktserver:kyotocabinet::StashDB::accept', 43function (ptregs) 44 -- Watch either get/set or both 45 if writeable ~= 'any' then 46 if ptregs.parm5 ~= writeable then return end 47 end 48 local line = ffi.new(key_type) 49 ffi.copy(line, ffi.cast('char *', ptregs.parm2)) 50 -- Check if we're looking for specific key 51 if watch_key ~= '*' then 52 if ptregs.parm3 ~= klen then return false end 53 if line ~= watch_key then return false end 54 end 55 print('%s write:%d\n', line, ptregs.parm5) 56end, false, -1, 0) 57-- User-space part of the program 58local ok, err = pcall(function() 59 local log = bpf.tracelog() 60 print(' TASK-PID CPU# TIMESTAMP FUNCTION') 61 print(' | | | | |') 62 while true do 63 print(log:read()) 64 end 65end) 66