samples/bpf/offwaketime.bpf.c

Source file repositories/reference/linux-study-clean/samples/bpf/offwaketime.bpf.c

File Facts

System
Linux kernel
Corpus path
samples/bpf/offwaketime.bpf.c
Extension
.c
Size
3423 bytes
Lines
142
Domain
Support Tooling And Documentation
Bucket
samples
Inferred role
Support Tooling And Documentation: implementation source
Status
source implementation candidate

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Dependency Surface

Detected Declarations

Annotated Snippet

struct key_t {
	char waker[TASK_COMM_LEN];
	char target[TASK_COMM_LEN];
	u32 wret;
	u32 tret;
};

struct {
	__uint(type, BPF_MAP_TYPE_HASH);
	__type(key, struct key_t);
	__type(value, u64);
	__uint(max_entries, MAX_ENTRIES);
} counts SEC(".maps");

struct {
	__uint(type, BPF_MAP_TYPE_HASH);
	__type(key, u32);
	__type(value, u64);
	__uint(max_entries, MAX_ENTRIES);
} start SEC(".maps");

struct wokeby_t {
	char name[TASK_COMM_LEN];
	u32 ret;
};

struct {
	__uint(type, BPF_MAP_TYPE_HASH);
	__type(key, u32);
	__type(value, struct wokeby_t);
	__uint(max_entries, MAX_ENTRIES);
} wokeby SEC(".maps");

struct {
	__uint(type, BPF_MAP_TYPE_STACK_TRACE);
	__uint(key_size, sizeof(u32));
	__uint(value_size, PERF_MAX_STACK_DEPTH * sizeof(u64));
	__uint(max_entries, MAX_ENTRIES);
} stackmap SEC(".maps");

#define STACKID_FLAGS (0 | BPF_F_FAST_STACK_CMP)

SEC("kprobe/try_to_wake_up")
int waker(struct pt_regs *ctx)
{
	struct task_struct *p = (void *)PT_REGS_PARM1_CORE(ctx);
	u32 pid = BPF_CORE_READ(p, pid);
	struct wokeby_t woke;

	bpf_get_current_comm(&woke.name, sizeof(woke.name));
	woke.ret = bpf_get_stackid(ctx, &stackmap, STACKID_FLAGS);

	bpf_map_update_elem(&wokeby, &pid, &woke, BPF_ANY);
	return 0;
}

static inline int update_counts(void *ctx, u32 pid, u64 delta)
{
	struct wokeby_t *woke;
	u64 zero = 0, *val;
	struct key_t key;

	__builtin_memset(&key.waker, 0, sizeof(key.waker));
	bpf_get_current_comm(&key.target, sizeof(key.target));
	key.tret = bpf_get_stackid(ctx, &stackmap, STACKID_FLAGS);
	key.wret = 0;

	woke = bpf_map_lookup_elem(&wokeby, &pid);
	if (woke) {
		key.wret = woke->ret;
		__builtin_memcpy(&key.waker, woke->name, sizeof(key.waker));
		bpf_map_delete_elem(&wokeby, &pid);
	}

	val = bpf_map_lookup_elem(&counts, &key);
	if (!val) {
		bpf_map_update_elem(&counts, &key, &zero, BPF_NOEXIST);
		val = bpf_map_lookup_elem(&counts, &key);
		if (!val)
			return 0;
	}
	(*val) += delta;
	return 0;
}

#if 1
/* taken from /sys/kernel/tracing/events/sched/sched_switch/format */
SEC("tracepoint/sched/sched_switch")
int oncpu(struct trace_event_raw_sched_switch *ctx)
{

Annotation

Implementation Notes