Automatically compute sizeof in bpf_trace_printk

* Addresses issue iovisor#61 Signed-off-by: Brenden Blanco <[email protected]>
linux-kern · Jun 17, 2015 · 71c3638 · 71c3638
1 parent 7679a2e
commit 71c3638
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Showing 2 changed files with 4 additions and 3 deletions.
diff --git a/examples/hello_world.py b/examples/hello_world.py
@@ -10,8 +10,7 @@
 
 prog = """
 int hello(void *ctx) {
- char fmt[] = "Hello, World!\\n";
- bpf_trace_printk(fmt, sizeof(fmt));
+ bpf_trace_printk("Hello, World!\\n");
  return 0;
 };
 """

diff --git a/src/cc/export/helpers.h b/src/cc/export/helpers.h
@@ -67,8 +67,10 @@ static int (*bpf_probe_read)(void *dst, u64 size, void *unsafe_ptr) =
  (void *) BPF_FUNC_probe_read;
 static u64 (*bpf_ktime_get_ns)(void) =
  (void *) BPF_FUNC_ktime_get_ns;
-static int (*bpf_trace_printk)(const char *fmt, u64 fmt_size, ...) =
+static int (*bpf_trace_printk_)(const char *fmt, u64 fmt_size, ...) =
  (void *) BPF_FUNC_trace_printk;
+#define bpf_trace_printk(_fmt, ...) \
+ ({ char fmt[] = _fmt; bpf_trace_printk_(fmt, sizeof(fmt), ##__VA_ARGS__); })
 static u64 (*bpf_clone_redirect)(void *ctx, u64 ifindex, u64 flags) =
  (void *) BPF_FUNC_clone_redirect;
 static void bpf_tail_call_(u64 map_fd, void *ctx, int index) {