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Mon, 26 Oct 2026 02:28:23 -0700 (PDT) Received: from krava ([2a02:8308:a00c:e200::25dc]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4a359ff2189sm215058535e9.1.2026.10.26.02.28.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 26 Oct 2026 02:28:22 -0700 (PDT) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Mon, 26 Oct 2026 10:28:20 +0100 To: Samuel Wu Cc: Jonathan Corbet , Shuah Khan , Randy Dunlap , Alexander Viro , Christian Brauner , Jan Kara , Andrii Nakryiko , Eduard Zingerman , Ihor Solodrai , Alexei Starovoitov , Daniel Borkmann , Kumar Kartikeya Dwivedi , Martin KaFai Lau , Song Liu , Yonghong Song , Emil Tsalapatis , Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt , kernel-team@android.com, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-doc@vger.kernel.org, bpf@vger.kernel.org, linux-kselftest@vger.kernel.org, llvm@lists.linux.dev Subject: Re: [PATCH bpf-next v2 4/6] libbpf: Resolve typeless ksyms via KALLSYMS_QUERY ioctl Message-ID: References: <20261023001603.560210-8-wusamuel@google.com> <20261023001603.560210-12-wusamuel@google.com> X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261023001603.560210-12-wusamuel@google.com> On Thu, Oct 22, 2026 at 05:16:05PM -0700, Samuel Wu wrote: SNIP > +static int bpf_object__query_ksyms(struct bpf_object *obj) > +{ > + struct kallsyms_query q; > + struct extern_desc *ext; > + int err = 0; > + int fd; > + int i; > + > + fd = open("/proc/kallsyms", O_RDONLY | O_CLOEXEC); > + if (fd < 0) > + return -errno; > + > + for (i = 0; i < obj->nr_extern; i++) { > + ext = &obj->externs[i]; > + if (ext->type != EXT_KSYM || ext->ksym.type_id) > + continue; > + > + q = (struct kallsyms_query){ > + .size = sizeof(q), > + .query_flags = KALLSYMS_QUERY_BY_SYMBOL, > + .sym_name_addr = ptr_to_u64(ext->name), > + }; > + > + err = -errno; > + if (err == -ENOENT) { > + err = 0; > + continue; > + } > + if (err == -EADDRNOTAVAIL) > + pr_warn("extern (ksym) '%s': resolution is ambiguous\n", > + ext->name); > + break; > + } > + ext->is_set = true; > + ext->ksym.addr = q.sym_addr; > + pr_debug("extern (ksym) '%s': resolved in kernel to 0x%llx\n", > + ext->name, ext->ksym.addr); > + } > + close(fd); > + return err; > +} > + > +static int bpf_object__resolve_typeless_ksyms(struct bpf_object *obj) > { > + int err; > + > + err = bpf_object__query_ksyms(obj); hi, we could also add similar support for libbpf_available_kallsyms_parse and probably in some other places like bpf_get_ksyms.. which makes me think it could be useful to have KALLSYMS_QUERY support for multiple symbols thanks, jirka > + /* > + * Fall back to parsing /proc/kallsyms only if the ioctl is not > + * accessible: not present (-ENOTTY on older kernels) or kallsyms > + * addresses hidden from this opener (-EPERM, e.g. kptr_restrict). > + */ > + if (err != -ENOTTY && err != -EPERM) > + return err; > + > + pr_debug("KALLSYMS_QUERY unavailable (%s), falling back to /proc/kallsyms\n", > + errstr(err)); > return libbpf_kallsyms_parse(kallsyms_cb, obj); > } > > @@ -9922,7 +9996,7 @@ static int bpf_object__resolve_externs(struct bpf_object *obj, > return -EINVAL; > } > if (need_kallsyms) { > - err = bpf_object__read_kallsyms_file(obj); > + err = bpf_object__resolve_typeless_ksyms(obj); > if (err) > return -EINVAL; > } > -- > 2.56.0.257.gf7497c7d27-goog >