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From: Florent Revest <revest@chromium.org>
To: bpf@vger.kernel.org
Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org,
	yhs@fb.com, kpsingh@kernel.org, jackmanb@chromium.org,
	linux-kernel@vger.kernel.org,
	Florent Revest <revest@chromium.org>
Subject: [PATCH bpf-next v5 4/6] libbpf: Initialize the bpf_seq_printf parameters array field by field
Date: Mon, 19 Apr 2021 17:52:41 +0200	[thread overview]
Message-ID: <20210419155243.1632274-5-revest@chromium.org> (raw)
In-Reply-To: <20210419155243.1632274-1-revest@chromium.org>

When initializing the __param array with a one liner, if all args are
const, the initial array value will be placed in the rodata section but
because libbpf does not support relocation in the rodata section, any
pointer in this array will stay NULL.

Fixes: c09add2fbc5a ("tools/libbpf: Add bpf_iter support")
Signed-off-by: Florent Revest <revest@chromium.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
---
 tools/lib/bpf/bpf_tracing.h | 40 +++++++++++++++++++++++++++----------
 1 file changed, 29 insertions(+), 11 deletions(-)

diff --git a/tools/lib/bpf/bpf_tracing.h b/tools/lib/bpf/bpf_tracing.h
index f9ef37707888..1c2e91ee041d 100644
--- a/tools/lib/bpf/bpf_tracing.h
+++ b/tools/lib/bpf/bpf_tracing.h
@@ -413,20 +413,38 @@ typeof(name(0)) name(struct pt_regs *ctx)				    \
 }									    \
 static __always_inline typeof(name(0)) ____##name(struct pt_regs *ctx, ##args)
 
+#define ___bpf_fill0(arr, p, x) do {} while (0)
+#define ___bpf_fill1(arr, p, x) arr[p] = x
+#define ___bpf_fill2(arr, p, x, args...) arr[p] = x; ___bpf_fill1(arr, p + 1, args)
+#define ___bpf_fill3(arr, p, x, args...) arr[p] = x; ___bpf_fill2(arr, p + 1, args)
+#define ___bpf_fill4(arr, p, x, args...) arr[p] = x; ___bpf_fill3(arr, p + 1, args)
+#define ___bpf_fill5(arr, p, x, args...) arr[p] = x; ___bpf_fill4(arr, p + 1, args)
+#define ___bpf_fill6(arr, p, x, args...) arr[p] = x; ___bpf_fill5(arr, p + 1, args)
+#define ___bpf_fill7(arr, p, x, args...) arr[p] = x; ___bpf_fill6(arr, p + 1, args)
+#define ___bpf_fill8(arr, p, x, args...) arr[p] = x; ___bpf_fill7(arr, p + 1, args)
+#define ___bpf_fill9(arr, p, x, args...) arr[p] = x; ___bpf_fill8(arr, p + 1, args)
+#define ___bpf_fill10(arr, p, x, args...) arr[p] = x; ___bpf_fill9(arr, p + 1, args)
+#define ___bpf_fill11(arr, p, x, args...) arr[p] = x; ___bpf_fill10(arr, p + 1, args)
+#define ___bpf_fill12(arr, p, x, args...) arr[p] = x; ___bpf_fill11(arr, p + 1, args)
+#define ___bpf_fill(arr, args...) \
+	___bpf_apply(___bpf_fill, ___bpf_narg(args))(arr, 0, args)
+
 /*
  * BPF_SEQ_PRINTF to wrap bpf_seq_printf to-be-printed values
  * in a structure.
  */
-#define BPF_SEQ_PRINTF(seq, fmt, args...)				    \
-	({								    \
-		_Pragma("GCC diagnostic push")				    \
-		_Pragma("GCC diagnostic ignored \"-Wint-conversion\"")	    \
-		static const char ___fmt[] = fmt;			    \
-		unsigned long long ___param[] = { args };		    \
-		_Pragma("GCC diagnostic pop")				    \
-		int ___ret = bpf_seq_printf(seq, ___fmt, sizeof(___fmt),    \
-					    ___param, sizeof(___param));    \
-		___ret;							    \
-	})
+#define BPF_SEQ_PRINTF(seq, 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_seq_printf(seq, ___fmt, sizeof(___fmt),		\
+		       ___param, sizeof(___param));		\
+})
 
 #endif
-- 
2.31.1.368.gbe11c130af-goog


  parent reply	other threads:[~2021-04-19 15:52 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-19 15:52 [PATCH bpf-next v5 0/6] Add a snprintf eBPF helper Florent Revest
2021-04-19 15:52 ` [PATCH bpf-next v5 1/6] bpf: Factorize bpf_trace_printk and bpf_seq_printf Florent Revest
2021-04-19 15:52 ` [PATCH bpf-next v5 2/6] bpf: Add a ARG_PTR_TO_CONST_STR argument type Florent Revest
2021-04-19 22:54   ` Alexei Starovoitov
2021-04-20 12:35     ` Florent Revest
2021-04-20 15:23       ` Alexei Starovoitov
2021-04-22  8:41         ` Florent Revest
2021-04-19 15:52 ` [PATCH bpf-next v5 3/6] bpf: Add a bpf_snprintf helper Florent Revest
2021-04-19 15:52 ` Florent Revest [this message]
2021-04-19 15:52 ` [PATCH bpf-next v5 5/6] libbpf: Introduce a BPF_SNPRINTF helper macro Florent Revest
2021-04-19 15:52 ` [PATCH bpf-next v5 6/6] selftests/bpf: Add a series of tests for bpf_snprintf Florent Revest
2021-04-23 22:38   ` Andrii Nakryiko
2021-04-26 10:10     ` Florent Revest
2021-04-26 16:19       ` Andrii Nakryiko
2021-04-26 21:08         ` Florent Revest
2021-04-27  6:35           ` Rasmus Villemoes
2021-04-27  9:50             ` Florent Revest
2021-04-27 18:03               ` Andrii Nakryiko
2021-04-28 14:59                 ` Florent Revest
2021-05-05  6:55                   ` Rasmus Villemoes
2021-05-05 14:25                     ` Florent Revest
2021-04-19 19:33 ` [PATCH bpf-next v5 0/6] Add a snprintf eBPF helper Andrii Nakryiko
2021-04-20 12:02   ` Florent Revest

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