[PATCH perf/core 11/22] selftests/bpf: Use 5-byte nop for x86 usdt probes

Jiri Olsa
2025-04-21T21:46:44Z

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

Signed-off-by: Jiri Olsa <jolsa@kernel.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 1fcfa5160231..1d62c06f5ddc 100644
--- a/tools/testing/selftests/bpf/sdt.h
+++ b/tools/testing/selftests/bpf/sdt.h
@@ -236,6 +236,13 @@ __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

@@ -288,7 +295,7 @@ __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) \
--
2.49.0