cregit-Linux how code gets into the kernel

Release 4.14 samples/bpf/xdp_monitor_kern.c

Directory: samples/bpf
/* XDP monitor tool, based on tracepoints
 *
 *  Copyright(c) 2017 Jesper Dangaard Brouer, Red Hat Inc.
 */
#include <uapi/linux/bpf.h>
#include "bpf_helpers.h"

struct bpf_map_def SEC("maps") redirect_err_cnt = {
	.type = BPF_MAP_TYPE_PERCPU_ARRAY,
	.key_size = sizeof(u32),
	.value_size = sizeof(u64),
	.max_entries = 2,
	/* TODO: have entries for all possible errno's */
};

/* Tracepoint format: /sys/kernel/debug/tracing/events/xdp/xdp_redirect/format
 * Code in:                kernel/include/trace/events/xdp.h
 */

struct xdp_redirect_ctx {
	
unsigned short common_type;	//      offset:0;  size:2; signed:0;
	
unsigned char common_flags;	//      offset:2;  size:1; signed:0;
	
unsigned char common_preempt_count;//      offset:3;  size:1; signed:0;
	
int common_pid;			//      offset:4;  size:4; signed:1;

	
int prog_id;			//      offset:8;  size:4; signed:1;
	
u32 act;			//      offset:12  size:4; signed:0;
	
int ifindex;			//      offset:16  size:4; signed:1;
	
int err;			//      offset:20  size:4; signed:1;
	
int to_ifindex;			//      offset:24  size:4; signed:1;
	
u32 map_id;			//      offset:28  size:4; signed:0;
	
int map_index;			//      offset:32  size:4; signed:1;
};					//      offset:36

enum {
	
XDP_REDIRECT_SUCCESS = 0,
	
XDP_REDIRECT_ERROR = 1
};


static __always_inline int xdp_redirect_collect_stat(struct xdp_redirect_ctx *ctx) { u32 key = XDP_REDIRECT_ERROR; int err = ctx->err; u64 *cnt; if (!err) key = XDP_REDIRECT_SUCCESS; cnt = bpf_map_lookup_elem(&redirect_err_cnt, &key); if (!cnt) return 0; *cnt += 1; return 0; /* Indicate event was filtered (no further processing)*/ /* * Returning 1 here would allow e.g. a perf-record tracepoint * to see and record these events, but it doesn't work well * in-practice as stopping perf-record also unload this * bpf_prog. Plus, there is additional overhead of doing so. */ }

Contributors

PersonTokensPropCommitsCommitProp
Jesper Dangaard Brouer66100.00%1100.00%
Total66100.00%1100.00%

SEC("tracepoint/xdp/xdp_redirect_err")
int trace_xdp_redirect_err(struct xdp_redirect_ctx *ctx) { return xdp_redirect_collect_stat(ctx); }

Contributors

PersonTokensPropCommitsCommitProp
Jesper Dangaard Brouer16100.00%1100.00%
Total16100.00%1100.00%

SEC("tracepoint/xdp/xdp_redirect_map_err")
int trace_xdp_redirect_map_err(struct xdp_redirect_ctx *ctx) { return xdp_redirect_collect_stat(ctx); }

Contributors

PersonTokensPropCommitsCommitProp
Jesper Dangaard Brouer16100.00%1100.00%
Total16100.00%1100.00%

/* Likely unloaded when prog starts */ SEC("tracepoint/xdp/xdp_redirect")
int trace_xdp_redirect(struct xdp_redirect_ctx *ctx) { return xdp_redirect_collect_stat(ctx); }

Contributors

PersonTokensPropCommitsCommitProp
Jesper Dangaard Brouer16100.00%1100.00%
Total16100.00%1100.00%

/* Likely unloaded when prog starts */ SEC("tracepoint/xdp/xdp_redirect_map")
int trace_xdp_redirect_map(struct xdp_redirect_ctx *ctx) { return xdp_redirect_collect_stat(ctx); }

Contributors

PersonTokensPropCommitsCommitProp
Jesper Dangaard Brouer16100.00%1100.00%
Total16100.00%1100.00%


Overall Contributors

PersonTokensPropCommitsCommitProp
Jesper Dangaard Brouer258100.00%1100.00%
Total258100.00%1100.00%
Directory: samples/bpf
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