linux-kernel - [RFC bpf-next 08/11] selftests/bpf: Use 5-byte nop for x86 usdt probes

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Message-ID: <20241105133405.2703607-9-jolsa@kernel.org>
Date: Tue,  5 Nov 2024 14:34:02 +0100
From: Jiri Olsa <jolsa@...nel.org>
To: Oleg Nesterov <oleg@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrii Nakryiko <andrii@...nel.org>
Cc: bpf@...r.kernel.org,
	Song Liu <songliubraving@...com>,
	Yonghong Song <yhs@...com>,
	John Fastabend <john.fastabend@...il.com>,
	Hao Luo <haoluo@...gle.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Alan Maguire <alan.maguire@...cle.com>,
	linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org
Subject: [RFC bpf-next 08/11] selftests/bpf: Use 5-byte nop for x86 usdt probes

Using 5-byte nop for x86 usdt probes so we can switch
to optimized uprobe them.

Signed-off-by: Jiri Olsa <jolsa@...nel.org>
---
 tools/testing/selftests/bpf/sdt.h | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/sdt.h b/tools/testing/selftests/bpf/sdt.h
index ca0162b4dc57..7ac9291f45f1 100644
--- a/tools/testing/selftests/bpf/sdt.h
+++ b/tools/testing/selftests/bpf/sdt.h
@@ -234,6 +234,13 @@ __extension__ extern unsigned long long __sdt_unsp;
 #define _SDT_NOP	nop
 #endif
 
+/* Use 5 byte nop for x86_64 to allow optimizing uprobes. */
+#if defined(__x86_64__)
+# define _SDT_DEF_NOP _SDT_ASM_5(990:	.byte 0x0f, 0x1f, 0x44, 0x00, 0x00)
+#else
+# define _SDT_DEF_NOP _SDT_ASM_1(990:	_SDT_NOP)
+#endif
+
 #define _SDT_NOTE_NAME	"stapsdt"
 #define _SDT_NOTE_TYPE	3
 
@@ -286,7 +293,7 @@ __extension__ extern unsigned long long __sdt_unsp;
 
 #define _SDT_ASM_BODY(provider, name, pack_args, args, ...)		      \
   _SDT_DEF_MACROS							      \
-  _SDT_ASM_1(990:	_SDT_NOP)					      \
+  _SDT_DEF_NOP								      \
   _SDT_ASM_3(		.pushsection .note.stapsdt,_SDT_ASM_AUTOGROUP,"note") \
   _SDT_ASM_1(		.balign 4)					      \
   _SDT_ASM_3(		.4byte 992f-991f, 994f-993f, _SDT_NOTE_TYPE)	      \
-- 
2.47.0