Helper function `bpf_map_delete_elem`

The delete map element helper call is used to delete values from maps.

Note

This helper function is only callable from eBPF, but has the same name as the bpf_map_delete_elem userspace library function, which can only be used from userspace programs.

Definition

Copyright (c) 2015 The Libbpf Authors. All rights reserved.

Delete entry with key from map.

Returns

0 on success, or a negative error in case of failure.

static long (* const bpf_map_delete_elem)(void *map, const void *key) = (void *) 3;

Usage

The map argument must be a pointer to a map definition and key must be a pointer to the key you wish to delete.

The return value will be 0 on success or a negative valued error number indicating a failure.

Program types

This helper call can be used in the following program types:

Map types

This helper call can be used with the following map types:

Example

#include "vmlinux.sh"
#include <bpf/bpf_helpers.h>

struct {
    __uint(type, BPF_MAP_TYPE_HASH);
    __type(key, u32);
    __type(value, u32);
    __uint(max_entries, 10240);
} cnt_map SEC(".maps");

SEC("tracepoints/syscalls/sys_enter_openat")
int bpf_prog1(void *ctx)
{
    u32 pid = bpf_get_current_pid_tgid();
    u32 init_val=0;
    u32 *cnt = bpf_map_lookup_elem(&cnt_map, &pid);
    if(cnt){
        __sync_fetch_and_add(cnt, 1);
    }else{
        bpf_map_update_elem(&cnt_map, &pid, &init_val, BPF_ANY);
        return 0;
    }
    if(*cnt == 42)
        bpf_map_delete_elem(&cnt_map, &pid);
    return 0;
}

char LICENSE[] SEC("license") = "GPL"

Helper function bpf_map_delete_elem