1 /* Copyright (c) 2013-2015 PLUMgrid, http://plumgrid.com 2 * Copyright (c) 2015 BMW Car IT GmbH 3 * 4 * This program is free software; you can redistribute it and/or 5 * modify it under the terms of version 2 of the GNU General Public 6 * License as published by the Free Software Foundation. 7 */ 8 #include <linux/version.h> 9 #include <linux/ptrace.h> 10 #include <uapi/linux/bpf.h> 11 #include <bpf/bpf_helpers.h> 12 13 #define MAX_ENTRIES 20 14 #define MAX_CPU 4 15 16 /* We need to stick to static allocated memory (an array instead of 17 * hash table) because managing dynamic memory from the 18 * trace_preempt_[on|off] tracepoints hooks is not supported. 19 */ 20 21 struct bpf_map_def SEC("maps") my_map = { 22 .type = BPF_MAP_TYPE_ARRAY, 23 .key_size = sizeof(int), 24 .value_size = sizeof(u64), 25 .max_entries = MAX_CPU, 26 }; 27 28 SEC("kprobe/trace_preempt_off") 29 int bpf_prog1(struct pt_regs *ctx) 30 { 31 int cpu = bpf_get_smp_processor_id(); 32 u64 *ts = bpf_map_lookup_elem(&my_map, &cpu); 33 34 if (ts) 35 *ts = bpf_ktime_get_ns(); 36 37 return 0; 38 } 39 40 static unsigned int log2(unsigned int v) 41 { 42 unsigned int r; 43 unsigned int shift; 44 45 r = (v > 0xFFFF) << 4; v >>= r; 46 shift = (v > 0xFF) << 3; v >>= shift; r |= shift; 47 shift = (v > 0xF) << 2; v >>= shift; r |= shift; 48 shift = (v > 0x3) << 1; v >>= shift; r |= shift; 49 r |= (v >> 1); 50 51 return r; 52 } 53 54 static unsigned int log2l(unsigned long v) 55 { 56 unsigned int hi = v >> 32; 57 58 if (hi) 59 return log2(hi) + 32; 60 else 61 return log2(v); 62 } 63 64 struct bpf_map_def SEC("maps") my_lat = { 65 .type = BPF_MAP_TYPE_ARRAY, 66 .key_size = sizeof(int), 67 .value_size = sizeof(long), 68 .max_entries = MAX_CPU * MAX_ENTRIES, 69 }; 70 71 SEC("kprobe/trace_preempt_on") 72 int bpf_prog2(struct pt_regs *ctx) 73 { 74 u64 *ts, cur_ts, delta; 75 int key, cpu; 76 long *val; 77 78 cpu = bpf_get_smp_processor_id(); 79 ts = bpf_map_lookup_elem(&my_map, &cpu); 80 if (!ts) 81 return 0; 82 83 cur_ts = bpf_ktime_get_ns(); 84 delta = log2l(cur_ts - *ts); 85 86 if (delta > MAX_ENTRIES - 1) 87 delta = MAX_ENTRIES - 1; 88 89 key = cpu * MAX_ENTRIES + delta; 90 val = bpf_map_lookup_elem(&my_lat, &key); 91 if (val) 92 __sync_fetch_and_add((long *)val, 1); 93 94 return 0; 95 96 } 97 98 char _license[] SEC("license") = "GPL"; 99 u32 _version SEC("version") = LINUX_VERSION_CODE; 100