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