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