libbpf: Introduce a BPF_SNPRINTF helper macro

Similarly to BPF_SEQ_PRINTF, this macro turns variadic arguments into an
array of u64, making it more natural to call the bpf_snprintf helper.

Signed-off-by: Florent Revest <revest@chromium.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210419155243.1632274-6-revest@chromium.org

diff --git a/tools/lib/bpf/bpf_tracing.h b/tools/lib/bpf/bpf_tracing.h
index 1c2e91ee041d8db7103e623579ff6f1c67fbe8ca..8c954ebc0c7c8b4501280fd25573636ced2c4f28 100644 (file)
--- a/tools/lib/bpf/bpf_tracing.h
+++ b/tools/lib/bpf/bpf_tracing.h
@@ -447,4 +447,22 @@ static __always_inline typeof(name(0)) ____##name(struct pt_regs *ctx, ##args)
                       ___param, sizeof(___param));             \
 })
 
+/*
+ * BPF_SNPRINTF wraps the bpf_snprintf helper with variadic arguments instead of
+ * an array of u64.
+ */
+#define BPF_SNPRINTF(out, out_size, fmt, args...)              \
+({                                                             \
+       static const char ___fmt[] = fmt;                       \
+       unsigned long long ___param[___bpf_narg(args)];         \
+                                                               \
+       _Pragma("GCC diagnostic push")                          \
+       _Pragma("GCC diagnostic ignored \"-Wint-conversion\"")  \
+       ___bpf_fill(___param, args);                            \
+       _Pragma("GCC diagnostic pop")                           \
+                                                               \
+       bpf_snprintf(out, out_size, ___fmt,                     \
+                    ___param, sizeof(___param));               \
+})
+
 #endif