1 // SPDX-License-Identifier: GPL-2.0 2 /* Copyright Leon Hwang */ 3 4 #include <linux/bpf.h> 5 #include <bpf/bpf_helpers.h> 6 7 #define ERRMSG_LEN 64 8 9 struct xdp_errmsg { 10 char msg[ERRMSG_LEN]; 11 }; 12 13 struct { 14 __uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY); 15 __type(key, int); 16 __type(value, int); 17 } xdp_errmsg_pb SEC(".maps"); 18 19 struct xdp_attach_error_ctx { 20 unsigned long unused; 21 22 /* 23 * bpf does not support tracepoint __data_loc directly. 24 * 25 * Actually, this field is a 32 bit integer whose value encodes 26 * information on where to find the actual data. The first 2 bytes is 27 * the size of the data. The last 2 bytes is the offset from the start 28 * of the tracepoint struct where the data begins. 29 * -- https://github.com/iovisor/bpftrace/pull/1542 30 */ 31 __u32 msg; // __data_loc char[] msg; 32 }; 33 34 /* 35 * Catch the error message at the tracepoint. 36 */ 37 38 SEC("tp/xdp/bpf_xdp_link_attach_failed") 39 int tp__xdp__bpf_xdp_link_attach_failed(struct xdp_attach_error_ctx *ctx) 40 { 41 char *msg = (void *)(__u64) ((void *) ctx + (__u16) ctx->msg); 42 struct xdp_errmsg errmsg = {}; 43 44 bpf_probe_read_kernel_str(&errmsg.msg, ERRMSG_LEN, msg); 45 bpf_perf_event_output(ctx, &xdp_errmsg_pb, BPF_F_CURRENT_CPU, &errmsg, 46 ERRMSG_LEN); 47 return 0; 48 } 49 50 /* 51 * Reuse the XDP program in xdp_dummy.c. 52 */ 53 54 char LICENSE[] SEC("license") = "GPL"; 55