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Fri, 15 May 2026 04:12:31 -0700 (PDT) From: Jakub Sitnicki To: Jiri Olsa Cc: Oleg Nesterov , Peter Zijlstra , Ingo Molnar , Masami Hiramatsu , Andrii Nakryiko , bpf@vger.kernel.org, linux-trace-kernel@vger.kernel.org Subject: Re: [PATCH 2/7] libbpf: Change has_nop_combo to work on top of nop10 In-Reply-To: <20260514135342.22130-3-jolsa@kernel.org> (Jiri Olsa's message of "Thu, 14 May 2026 15:53:37 +0200") References: <20260514135342.22130-1-jolsa@kernel.org> <20260514135342.22130-3-jolsa@kernel.org> Date: Fri, 15 May 2026 13:12:29 +0200 Message-ID: <87fr3t7wpu.fsf@cloudflare.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain On Thu, May 14, 2026 at 03:53 PM +02, Jiri Olsa wrote: > We now expect nop combo with 10 bytes nop instead of 5 bytes nop, > fixing has_nop_combo to reflect that. > > Signed-off-by: Jiri Olsa > --- > tools/lib/bpf/usdt.c | 16 ++++++++-------- > 1 file changed, 8 insertions(+), 8 deletions(-) > > diff --git a/tools/lib/bpf/usdt.c b/tools/lib/bpf/usdt.c > index e3710933fd52..7e62e4d5bedd 100644 > --- a/tools/lib/bpf/usdt.c > +++ b/tools/lib/bpf/usdt.c > @@ -305,7 +305,7 @@ struct usdt_manager *usdt_manager_new(struct bpf_object *obj) > > /* > * Detect kernel support for uprobe() syscall, it's presence means we can > - * take advantage of faster nop5 uprobe handling. > + * take advantage of faster nop10 uprobe handling. > * Added in: 56101b69c919 ("uprobes/x86: Add uprobe syscall to speed up uprobe") > */ > man->has_uprobe_syscall = kernel_supports(obj, FEAT_UPROBE_SYSCALL); > @@ -596,14 +596,14 @@ static int parse_usdt_spec(struct usdt_spec *spec, const struct usdt_note *note, > #if defined(__x86_64__) > static bool has_nop_combo(int fd, long off) > { > - unsigned char nop_combo[6] = { > - 0x90, 0x0f, 0x1f, 0x44, 0x00, 0x00 /* nop,nop5 */ > + unsigned char nop_combo[11] = { > + 0x90, 0x66, 0x66, 0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00, > }; > - unsigned char buf[6]; > + unsigned char buf[11]; > > - if (pread(fd, buf, 6, off) != 6) > + if (pread(fd, buf, 11, off) != 11) > return false; > - return memcmp(buf, nop_combo, 6) == 0; > + return memcmp(buf, nop_combo, 11) == 0; > } > #else > static bool has_nop_combo(int fd, long off) Nit: Would use ARRAY_SIZE(buf) instead of repeating the scalar value in multiple places. Otherwise: Reviewed-by: Jakub Sitnicki