diff options
Diffstat (limited to 'samples/bpf/tracex1_kern.c')
| -rw-r--r-- | samples/bpf/tracex1_kern.c | 48 |
1 files changed, 48 insertions, 0 deletions
diff --git a/samples/bpf/tracex1_kern.c b/samples/bpf/tracex1_kern.c new file mode 100644 index 000000000..9c74b45c5 --- /dev/null +++ b/samples/bpf/tracex1_kern.c @@ -0,0 +1,48 @@ +/* Copyright (c) 2013-2015 PLUMgrid, http://plumgrid.com + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of version 2 of the GNU General Public + * License as published by the Free Software Foundation. + */ +#include <linux/skbuff.h> +#include <linux/netdevice.h> +#include <uapi/linux/bpf.h> +#include <linux/version.h> +#include "bpf_helpers.h" + +#define _(P) ({typeof(P) val = 0; bpf_probe_read(&val, sizeof(val), &P); val;}) + +/* kprobe is NOT a stable ABI + * kernel functions can be removed, renamed or completely change semantics. + * Number of arguments and their positions can change, etc. + * In such case this bpf+kprobe example will no longer be meaningful + */ +SEC("kprobe/__netif_receive_skb_core") +int bpf_prog1(struct pt_regs *ctx) +{ + /* attaches to kprobe __netif_receive_skb_core, + * looks for packets on loobpack device and prints them + */ + char devname[IFNAMSIZ]; + struct net_device *dev; + struct sk_buff *skb; + int len; + + /* non-portable! works for the given kernel only */ + bpf_probe_read_kernel(&skb, sizeof(skb), (void *)PT_REGS_PARM1(ctx)); + dev = _(skb->dev); + len = _(skb->len); + + bpf_probe_read(devname, sizeof(devname), dev->name); + + if (devname[0] == 'l' && devname[1] == 'o') { + char fmt[] = "skb %p len %d\n"; + /* using bpf_trace_printk() for DEBUG ONLY */ + bpf_trace_printk(fmt, sizeof(fmt), skb, len); + } + + return 0; +} + +char _license[] SEC("license") = "GPL"; +u32 _version SEC("version") = LINUX_VERSION_CODE; |