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From: Dave Marchevsky <davemarchevsky@fb.com>
To: <bpf@vger.kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andrii@kernel.org>, Yonghong Song <yhs@fb.com>,
	<netdev@vger.kernel.org>, Dave Marchevsky <davemarchevsky@fb.com>
Subject: [PATCH v4 bpf-next 5/9] libbpf: use static const fmt string in __bpf_printk
Date: Thu, 2 Sep 2021 10:19:25 -0700	[thread overview]
Message-ID: <20210902171929.3922667-6-davemarchevsky@fb.com> (raw)
In-Reply-To: <20210902171929.3922667-1-davemarchevsky@fb.com>

The __bpf_printk convenience macro was using a 'char' fmt string holder
as it predates support for globals in libbpf. Move to more efficient
'static const char', but provide a fallback to the old way via
BPF_NO_GLOBAL_DATA so users on old kernels can still use the macro.

Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
---
 tools/lib/bpf/bpf_helpers.h | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h
index a7e73be6dac4..7df7d9a23099 100644
--- a/tools/lib/bpf/bpf_helpers.h
+++ b/tools/lib/bpf/bpf_helpers.h
@@ -216,10 +216,16 @@ enum libbpf_tristate {
 		     ___param, sizeof(___param));		\
 })
 
+#ifdef BPF_NO_GLOBAL_DATA
+#define BPF_PRINTK_FMT_MOD
+#else
+#define BPF_PRINTK_FMT_MOD static const
+#endif
+
 /* Helper macro to print out debug messages */
 #define __bpf_printk(fmt, ...)				\
 ({							\
-	char ____fmt[] = fmt;				\
+	BPF_PRINTK_FMT_MOD char ____fmt[] = fmt;	\
 	bpf_trace_printk(____fmt, sizeof(____fmt),	\
 			 ##__VA_ARGS__);		\
 })
-- 
2.30.2


  parent reply	other threads:[~2021-09-02 17:23 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-02 17:19 [PATCH v4 bpf-next 0/9] bpf: implement variadic printk helper Dave Marchevsky
2021-09-02 17:19 ` [PATCH v4 bpf-next 1/9] bpf: merge printk and seq_printf VARARG max macros Dave Marchevsky
2021-09-02 17:19 ` [PATCH v4 bpf-next 2/9] selftests/bpf: stop using bpf_program__load Dave Marchevsky
2021-09-02 22:58   ` Andrii Nakryiko
2021-09-02 17:19 ` [PATCH v4 bpf-next 3/9] bpf: add bpf_trace_vprintk helper Dave Marchevsky
2021-09-02 17:19 ` [PATCH v4 bpf-next 4/9] libbpf: Modify bpf_printk to choose helper based on arg count Dave Marchevsky
2021-09-02 23:08   ` Andrii Nakryiko
2021-09-02 17:19 ` Dave Marchevsky [this message]
2021-09-02 23:09   ` [PATCH v4 bpf-next 5/9] libbpf: use static const fmt string in __bpf_printk Andrii Nakryiko
2021-09-02 17:19 ` [PATCH v4 bpf-next 6/9] bpftool: only probe trace_vprintk feature in 'full' mode Dave Marchevsky
2021-09-02 23:10   ` Andrii Nakryiko
2021-09-02 17:19 ` [PATCH v4 bpf-next 7/9] selftests/bpf: Migrate prog_tests/trace_printk CHECKs to ASSERTs Dave Marchevsky
2021-09-02 17:19 ` [PATCH v4 bpf-next 8/9] selftests/bpf: add trace_vprintk test prog Dave Marchevsky
2021-09-02 23:13   ` Andrii Nakryiko
2021-09-02 17:19 ` [PATCH v4 bpf-next 9/9] selftests/bpf: Add test for bpf_printk w/ 0 fmt args Dave Marchevsky
2021-09-02 23:14   ` Andrii Nakryiko

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