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Wed, 01 Jul 2026 11:53:25 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Wed, 01 Jul 2026 11:53:25 -0700 Message-Id: Cc: "Masami Hiramatsu (Google)" , "Shuah Khan" , "Mathieu Desnoyers" , , , , Subject: Re: [RFC PATCH 2/4] tracing/probes: Compile all fetchargs into a single BPF program per event From: "Alexei Starovoitov" To: "Steven Rostedt" X-Mailer: aerc References: <178291352217.1566898.14481561093843379745.stgit@devnote2> <178291354144.1566898.14374948740441958770.stgit@devnote2> <20260701144726.0a5f2204@gandalf.local.home> In-Reply-To: <20260701144726.0a5f2204@gandalf.local.home> On Wed Jul 1, 2026 at 11:47 AM PDT, Steven Rostedt wrote: > On Wed, 01 Jul 2026 11:41:26 -0700 > "Alexei Starovoitov" wrote: > >> Nack. >> I really don't like it. > > So the nack is mostly your opinion and not technical? > >> There were days in the past when the kernel generating bpf directly was = appealing. >> These days are gone. Performance improvements for fetchargs is not a goo= d reason > > Why is performance *not* a good reason? > >> to add all this complexity and bypass verifier checks. > > The code lives in the kernel. What reason is there to add verification > checks? The point of verification is because we don't trust user space. W= hy > do we not trust the kernel? > >> bpf insns should come from user space. > > Why? because I see this patchset as pointless kernel bloat with the "help" of bp= f. Hence the nack to avoid dragging bpf into this. Call it philosophical disagreement if you like.