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ktrace-CO-RE: Add bpf_printk statement in code

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Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
This commit is contained in:
Jesper Dangaard Brouer
2021-06-11 18:20:44 +02:00
parent 566a14cb47
commit 599646aa64
1 changed files with 19 additions and 0 deletions
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19
ktrace-CO-RE/ktrace01_kern.c
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@@ -14,6 +14,23 @@
char _license[] SEC("license") = "GPL";
/* define our own struct definition if our vmlinux.h is outdated */
struct trace_event_raw_bpf_trace_printk___x {};
/* https://nakryiko.com/posts/bpf-tips-printk/ */
#undef bpf_printk // See /usr/include/bpf/bpf_helpers.h
#define bpf_printk(fmt, ...) \
({ \
static char ____fmt[] = fmt "\0"; \
if (0 /* bpf_core_type_exists( struct trace_event_raw_bpf_trace_printk___x)*/) { \
bpf_trace_printk(____fmt, sizeof(____fmt) - 1, ##__VA_ARGS__); \
} else { \
____fmt[sizeof(____fmt) - 2] = '\n'; \
bpf_trace_printk(____fmt, sizeof(____fmt), ##__VA_ARGS__); \
} \
})
/* Gotcha: bpf_core_type_exists() needs __builtin_preserve_type_info */
struct my_struct {
int v;
__u64 m2;
@@ -34,6 +51,8 @@ int BPF_KPROBE(udp_send_skb, struct sk_buff *skb)
a.v = bpf_get_prandom_u32() * x;
bpf_printk("skb->hash = 0x%x", x);
if (a.v == 43)
return 0;
return G.v;