eBPF 入门开发实践教程六：捕获进程发送信号的系统调用集合，使用 hash map 保存状态

#include <vmlinux.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>
 
#define MAX_ENTRIES 10240
#define TASK_COMM_LEN 16
 
struct event {
 unsigned int pid;
 unsigned int tpid;
 int sig;
 int ret;
 char comm[TASK_COMM_LEN];
};
 
struct {
 __uint(type, BPF_MAP_TYPE_HASH);
 __uint(max_entries, MAX_ENTRIES);
 __type(key, __u32);
 __type(value, struct event);
} values SEC(".maps");
 
 
static int probe_entry(pid_t tpid, int sig)
{
 struct event event = {};
 __u64 pid_tgid;
 __u32 tid;
 
 pid_tgid = bpf_get_current_pid_tgid();
 tid = (__u32)pid_tgid;
 event.pid = pid_tgid >> 32;
 event.tpid = tpid;
 event.sig = sig;
 bpf_get_current_comm(event.comm, sizeof(event.comm));
 bpf_map_update_elem(&values, &tid, &event, BPF_ANY);
 return 0;
}
 
static int probe_exit(void *ctx, int ret)
{
 __u64 pid_tgid = bpf_get_current_pid_tgid();
 __u32 tid = (__u32)pid_tgid;
 struct event *eventp;
 
 eventp = bpf_map_lookup_elem(&values, &tid);
 if (!eventp)
  return 0;
 
 eventp->ret = ret;
 bpf_printk("PID %d (%s) sent signal %d ",
           eventp->pid, eventp->comm, eventp->sig);
 bpf_printk("to PID %d, ret = %d",
           eventp->tpid, ret);
 
cleanup:
 bpf_map_delete_elem(&values, &tid);
 return 0;
}
 
SEC("tracepoint/syscalls/sys_enter_kill")
int kill_entry(struct trace_event_raw_sys_enter *ctx)
{
 pid_t tpid = (pid_t)ctx->args[0];
 int sig = (int)ctx->args[1];
 
 return probe_entry(tpid, sig);
}
 
SEC("tracepoint/syscalls/sys_exit_kill")
int kill_exit(struct trace_event_raw_sys_exit *ctx)
{
 return probe_exit(ctx, ctx->ret);
}
 
char LICENSE[] SEC("license") = "Dual BSD/GPL";

docker run -it -v `pwd`/:/src/ ghcr.io/eunomia-bpf/ecc-`uname -m`:latest

$ ecc sigsnoop.bpf.c
Compiling bpf object...
Generating export types...
Packing ebpf object and config into package.json...
$ sudo ecli run package.json
Runing eBPF program...

$ sudo cat /sys/kernel/debug/tracing/trace_pipe
    systemd-journal-363     [000] d...1   672.563868: bpf_trace_printk: PID 363 (systemd-journal) sent signal 0
     systemd-journal-363     [000] d...1   672.563869: bpf_trace_printk: to PID 1400, ret = 0
     systemd-journal-363     [000] d...1   672.563870: bpf_trace_printk: PID 363 (systemd-journal) sent signal 0
     systemd-journal-363     [000] d...1   672.563870: bpf_trace_printk: to PID 1527, ret = -3

struct {
 __uint(type, BPF_MAP_TYPE_HASH);
 __uint(max_entries, MAX_ENTRIES);
 __type(key, __u32);
 __type(value, struct event);
} values SEC(".maps");