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([2620:10d:c090:500::7:e1e5]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-29034de54d2sm6278115ad.12.2025.10.08.13.30.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 08 Oct 2025 13:30:21 -0700 (PDT) Message-ID: <09bc63a92ba1c9042d57bf19258e28e3cd00be57.camel@gmail.com> Subject: Re: bpf_errno. Was: [PATCH RFC bpf-next 1/3] bpf: report probe fault to BPF stderr From: Eduard Zingerman To: Kumar Kartikeya Dwivedi Cc: Alexei Starovoitov , Leon Hwang , Andrii Nakryiko , Menglong Dong , Menglong Dong , Alexei Starovoitov , bpf , LKML , linux-trace-kernel , jiang.biao@linux.dev Date: Wed, 08 Oct 2025 13:30:19 -0700 In-Reply-To: References: <20250927061210.194502-1-menglong.dong@linux.dev> <20250927061210.194502-2-menglong.dong@linux.dev> <3571660.QJadu78ljV@7950hx> <7f28937c-121a-4ea8-b66a-9da3be8bccad@gmail.com> <0adc5d8a299483004f4796a418420fe1c69f24bc.camel@gmail.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2 (3.56.2-1.fc42) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Wed, 2025-10-08 at 22:08 +0200, Kumar Kartikeya Dwivedi wrote: [...] > Since we're piling on ideas, one of the other things that I think > could be useful in general (and maybe should be done orthogonally to > bpf_errno) > is making some empty nop function and making it not traceable reliably ^^^^^^^^^^^^^ You mean traceable, right? So that user attaches a bpf program to it, and debugs bpf programs using bpf programs? > across arches and invoke it in the bpf exception handler. > Then if we expose prog_stream_dump_stack() as a kfunc (should be > trivial), the user can write anything to stderr that is relevant to > get more information on the fault. >=20 > It is then up to the user to decide the rate of messages for such > faults etc. and get more information if needed.