linux-kernel - [PATCH bpf-next v2 5/6] libbpf: Introduce a BPF

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Date:   Wed, 24 Mar 2021 03:22:10 +0100
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 v2 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>
---
 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 d9a4c3f77ff4..e5c6ede6060b 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)
 		__ret;							    \
 	})
 
+/*
+ * BPF_SNPRINTF wraps the bpf_snprintf helper with variadic arguments instead of
+ * an array of u64.
+ */
+#define BPF_SNPRINTF(out, out_size, fmt, args...)			    \
+	({								    \
+		_Pragma("GCC diagnostic push")				    \
+		_Pragma("GCC diagnostic ignored \"-Wint-conversion\"")	    \
+		unsigned long long ___param[___bpf_narg(args)];		    \
+		static const char ___fmt[] = fmt;			    \
+		int __ret;						    \
+		___bpf_fill(___param, args);				    \
+		_Pragma("GCC diagnostic pop")				    \
+		__ret = bpf_snprintf(out, out_size, ___fmt,		    \
+				     ___param, sizeof(___param));	    \
+		__ret;							    \
+	})
+
 #endif
-- 
2.31.0.291.g576ba9dcdaf-goog