samples/bpf/offwaketime_kern.c

   1 /* Copyright (c) 2016 Facebook
   2  *
   3  * This program is free software; you can redistribute it and/or
   4  * modify it under the terms of version 2 of the GNU General Public
   5  * License as published by the Free Software Foundation.
   6  */
   7 #include <uapi/linux/bpf.h>
   8 #include <uapi/linux/ptrace.h>
   9 #include <uapi/linux/perf_event.h>
  10 #include <linux/version.h>
  11 #include <linux/sched.h>
  12 #include <bpf/bpf_helpers.h>
  13 #include <bpf/bpf_tracing.h>
  14
  15 #define _(P)                                                                   \
  16         ({                                                                     \
  17                 typeof(P) val;                                                 \
  18                 bpf_probe_read_kernel(&val, sizeof(val), &(P));                \
  19                 val;                                                           \
  20         })
  21
  22 #define MINBLOCK_US     1
  23 #define MAX_ENTRIES     10000
  24
  25 struct key_t {
  26         char waker[TASK_COMM_LEN];
  27         char target[TASK_COMM_LEN];
  28         u32 wret;
  29         u32 tret;
  30 };
  31
  32 struct {
  33         __uint(type, BPF_MAP_TYPE_HASH);
  34         __type(key, struct key_t);
  35         __type(value, u64);
  36         __uint(max_entries, MAX_ENTRIES);
  37 } counts SEC(".maps");
  38
  39 struct {
  40         __uint(type, BPF_MAP_TYPE_HASH);
  41         __type(key, u32);
  42         __type(value, u64);
  43         __uint(max_entries, MAX_ENTRIES);
  44 } start SEC(".maps");
  45
  46 struct wokeby_t {
  47         char name[TASK_COMM_LEN];
  48         u32 ret;
  49 };
  50
  51 struct {
  52         __uint(type, BPF_MAP_TYPE_HASH);
  53         __type(key, u32);
  54         __type(value, struct wokeby_t);
  55         __uint(max_entries, MAX_ENTRIES);
  56 } wokeby SEC(".maps");
  57
  58 struct {
  59         __uint(type, BPF_MAP_TYPE_STACK_TRACE);
  60         __uint(key_size, sizeof(u32));
  61         __uint(value_size, PERF_MAX_STACK_DEPTH * sizeof(u64));
  62         __uint(max_entries, MAX_ENTRIES);
  63 } stackmap SEC(".maps");
  64
  65 #define STACKID_FLAGS (0 | BPF_F_FAST_STACK_CMP)
  66
  67 SEC("kprobe/try_to_wake_up")
  68 int waker(struct pt_regs *ctx)
  69 {
  70         struct task_struct *p = (void *) PT_REGS_PARM1(ctx);
  71         struct wokeby_t woke;
  72         u32 pid;
  73
  74         pid = _(p->pid);
  75
  76         bpf_get_current_comm(&woke.name, sizeof(woke.name));
  77         woke.ret = bpf_get_stackid(ctx, &stackmap, STACKID_FLAGS);
  78
  79         bpf_map_update_elem(&wokeby, &pid, &woke, BPF_ANY);
  80         return 0;
  81 }
  82
  83 static inline int update_counts(void *ctx, u32 pid, u64 delta)
  84 {
  85         struct wokeby_t *woke;
  86         u64 zero = 0, *val;
  87         struct key_t key;
  88
  89         __builtin_memset(&key.waker, 0, sizeof(key.waker));
  90         bpf_get_current_comm(&key.target, sizeof(key.target));
  91         key.tret = bpf_get_stackid(ctx, &stackmap, STACKID_FLAGS);
  92         key.wret = 0;
  93
  94         woke = bpf_map_lookup_elem(&wokeby, &pid);
  95         if (woke) {
  96                 key.wret = woke->ret;
  97                 __builtin_memcpy(&key.waker, woke->name, sizeof(key.waker));
  98                 bpf_map_delete_elem(&wokeby, &pid);
  99         }
 100
 101         val = bpf_map_lookup_elem(&counts, &key);
 102         if (!val) {
 103                 bpf_map_update_elem(&counts, &key, &zero, BPF_NOEXIST);
 104                 val = bpf_map_lookup_elem(&counts, &key);
 105                 if (!val)
 106                         return 0;
 107         }
 108         (*val) += delta;
 109         return 0;
 110 }
 111
 112 #if 1
 113 /* taken from /sys/kernel/debug/tracing/events/sched/sched_switch/format */
 114 struct sched_switch_args {
 115         unsigned long long pad;
 116         char prev_comm[16];
 117         int prev_pid;
 118         int prev_prio;
 119         long long prev_state;
 120         char next_comm[16];
 121         int next_pid;
 122         int next_prio;
 123 };
 124 SEC("tracepoint/sched/sched_switch")
 125 int oncpu(struct sched_switch_args *ctx)
 126 {
 127         /* record previous thread sleep time */
 128         u32 pid = ctx->prev_pid;
 129 #else
 130 SEC("kprobe/finish_task_switch")
 131 int oncpu(struct pt_regs *ctx)
 132 {
 133         struct task_struct *p = (void *) PT_REGS_PARM1(ctx);
 134         /* record previous thread sleep time */
 135         u32 pid = _(p->pid);
 136 #endif
 137         u64 delta, ts, *tsp;
 138
 139         ts = bpf_ktime_get_ns();
 140         bpf_map_update_elem(&start, &pid, &ts, BPF_ANY);
 141
 142         /* calculate current thread's delta time */
 143         pid = bpf_get_current_pid_tgid();
 144         tsp = bpf_map_lookup_elem(&start, &pid);
 145         if (!tsp)
 146                 /* missed start or filtered */
 147                 return 0;
 148
 149         delta = bpf_ktime_get_ns() - *tsp;
 150         bpf_map_delete_elem(&start, &pid);
 151         delta = delta / 1000;
 152         if (delta < MINBLOCK_US)
 153                 return 0;
 154
 155         return update_counts(ctx, pid, delta);
 156 }
 157 char _license[] SEC("license") = "GPL";
 158 u32 _version SEC("version") = LINUX_VERSION_CODE;