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Date: Thu, 4 Sep 2025 22:35:11 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Jiri Olsa <olsajiri@gmail.com>, Oleg Nesterov <oleg@redhat.com>,
	Andrii Nakryiko <andrii@kernel.org>, bpf <bpf@vger.kernel.org>,
	open list <linux-kernel@vger.kernel.org>,
	Linux trace kernel <linux-trace-kernel@vger.kernel.org>,
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	Thomas =?iso-8859-1?Q?Wei=DFschuh?= <thomas@t-8ch.de>,
	Ingo Molnar <mingo@kernel.org>
Subject: Re: nop5-optimized USDTs WAS: Re: [PATCHv6 perf/core 09/22]
 uprobes/x86: Add uprobe syscall to speed up uprobe
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On Thu, Sep 04, 2025 at 11:27:45AM -0700, Andrii Nakryiko wrote:

> > > So I've been thinking what's the simplest and most reliable way to
> > > feature-detect support for this sys_uprobe (e.g., for libbpf to know
> > > whether we should attach at nop5 vs nop1), and clearly that would be
> >
> > wrt nop5/nop1.. so the idea is to have USDT macro emit both nop1,nop5
> > and store some info about that in the usdt's elf note, right?

Wait, what? You're doing to emit 6 bytes and two nops? Why? Surely the
old kernel can INT3 on top of a NOP5?