On Mon, Apr 21, 2025 at 2:46 PM Jiri Olsa <[email protected]> wrote: > > Using 5-byte nop for x86 usdt probes so we can switch > to optimized uprobe them. > > Signed-off-by: Jiri Olsa <[email protected]> > --- > tools/testing/selftests/bpf/sdt.h | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) >
So sdt.h is an exact copy/paste from systemtap-sdt sources. I'd prefer to not modify it unnecessarily. How about we copy/paste usdt.h ([0]) and use *that* for your benchmarks? I've already anticipated the need to change nop instruction, so you won't even need to modify the usdt.h file itself, just #define USDT_NOP .byte 0x0f, 0x1f, 0x44, 0x00, 0x00 before #include "usdt.h" [0] https://github.com/libbpf/usdt/blob/main/usdt.h > 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 >
