linux-kernel - [PATCH bpf-next v4 5/6] libbpf: Introduce a BPF

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Date:   Wed, 14 Apr 2021 20:54:05 +0200
From:   Florent Revest <revest@...omium.org>
To:     bpf@...r.kernel.org
Cc:     ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
        yhs@...com, kpsingh@...nel.org, jackmanb@...omium.org,
        linux-kernel@...r.kernel.org, Florent Revest <revest@...omium.org>
Subject: [PATCH bpf-next v4 5/6] 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@...omium.org>
Acked-by: Andrii Nakryiko <andrii@...nel.org>
---
 tools/lib/bpf/bpf_tracing.h | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/tools/lib/bpf/bpf_tracing.h b/tools/lib/bpf/bpf_tracing.h
index 1c2e91ee041d..8c954ebc0c7c 100644
--- 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
-- 
2.31.1.295.g9ea45b61b8-goog