From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DA896C433DB for ; Tue, 12 Jan 2021 03:34:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9E5A322B37 for ; Tue, 12 Jan 2021 03:34:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727466AbhALDeq (ORCPT ); Mon, 11 Jan 2021 22:34:46 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37290 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727321AbhALDeq (ORCPT ); Mon, 11 Jan 2021 22:34:46 -0500 Received: from mail-ej1-x62f.google.com (mail-ej1-x62f.google.com [IPv6:2a00:1450:4864:20::62f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 31B1AC061575 for ; Mon, 11 Jan 2021 19:34:05 -0800 (PST) Received: by mail-ej1-x62f.google.com with SMTP id g20so1490666ejb.1 for ; Mon, 11 Jan 2021 19:34:05 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=araalinetworks-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=kYJw9f5mPBroza7bDy8SuS1CoB6Tb/uu9epaV6vcQvg=; b=xQqZse4r3f1gauAi4g9uX4Jf9yL5p+tTkeBi/EELdbf/CtDvBFG+DMkZhRLOD2sSrn 0/S9loCOYzySCjh03vEgiSwFP8YuAgKnBkx9ubZfbBaRqEkyekLaPGTxjMHKelw5yfgA ATAd7b/bYw/Ltj0Nt/aPeX/hMiGYqUdzr6B1pqHfO3hT0GknqR7eRaTUkDltbqDOrY8J ZKTv1BmY6+RARjDyFL6vNBW91z445MQZCP4O1WgDMXjOyF3RUoeT2DwO+PTS2xzMoIkQ o4W1pfizLyxKxvrEf1Nk7/rptr+zqQCSbCfYdPPg5jneop0R5Z1/KCElHOE6eHKQLBS2 PoEw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=kYJw9f5mPBroza7bDy8SuS1CoB6Tb/uu9epaV6vcQvg=; b=r8oFrZUQSQoR9ZGOtLjNXCYuhZgyFdMD5zSaY7GuYezyGK80zvOdAJB5O6TCU/Tj48 DiCgrJQu6MuX1DZbxwGzuRTt0xh3oAUYjsVV+3wzdhR8FooA1uwCQ3CCzXDfX0ET9p5c SbQPNXVoIxKo9dSFcTLlzUSqVdOMKqnvUV1TspykX4RuuskCKit+sNGl1ZF1YFFewFC/ gz+MUg2f08jSKWHpOYVMnCnyBnUfy4lleKxnAFBcy5qIV3BNFrKbZ0uPqB3CzMmX0ovG dDxqKqcn0aVazCI8RhhtpHPbUB41SkGt5wKY5uGktMl+Y8845SEbzW1z8I0yYCYJYaOF xcMw== X-Gm-Message-State: AOAM533fV68sHWqK4KgJsqgHUm+17y1oRdcMgVTnw39QKfv9qgkzH+9Y x4H5rfyj3hsQZ0SzIaeS1oHAGJKgUvmxNu7B/lr2/Q== X-Google-Smtp-Source: ABdhPJy9+lxJ/q/ryne60Q73nfMhqFST9zf6rRHOH+I5iKKAGJKCjGTplX26iq+Ea4Ja6IO7nhWsmAJGWj6MRQNAbi4= X-Received: by 2002:a17:906:2ccb:: with SMTP id r11mr1757109ejr.39.1610422443804; Mon, 11 Jan 2021 19:34:03 -0800 (PST) MIME-Version: 1.0 References: In-Reply-To: From: Vamsi Kodavanty Date: Mon, 11 Jan 2021 19:33:52 -0800 Message-ID: Subject: Re: [PATCH bpf v1] Add `core_btf_path` to `bpf_object_open_opts` to pass BTF path from skeleton program To: Andrii Nakryiko Cc: bpf Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Andrii, Thank you for the detailed review. I will address them as well as the self tests. And will send out a new patch addressing them and conforming to style/expectations. Cheers Vamsi. On Mon, Jan 11, 2021 at 2:02 PM Andrii Nakryiko wrote: > > On Fri, Jan 8, 2021 at 6:36 PM Vamsi Kodavanty wrote: > > > > Andrii, > > I have made the following changes as discussed to add an option to the `open_opts` > > to take in the BTF. > > Please do take a look. Also, I am not sure what the procedure is for submitting patches/reviews. > > If anyone has any pointers to a webpage where this is described I can go through it. But, below are > > the proposed changes. > > > > Daniel already gave you pointers. Also make sure you add [PATCH > bpf-next] prefix to email subject to identify the patch is for > bpf-next kernel tree. > And with all changes like this we should also add selftests, > exercising new features. Please take a look at > tools/testing/selftests/bpf. I think updating > test_progs/test_core_reloc.c in there to use this instead of > bpf_object__load_xattr() might be enough of the testing. > > > Best Regards, > > Vamsi. > > > > --- > > src/libbpf.c | 56 +++++++++++++++++++++++++++++++++++++--------------- > > src/libbpf.h | 4 +++- > > 2 files changed, 43 insertions(+), 17 deletions(-) > > > > diff --git a/src/libbpf.c b/src/libbpf.c > > index 6ae748f..35d7254 100644 > > --- a/src/libbpf.c > > +++ b/src/libbpf.c > > @@ -2538,9 +2538,12 @@ static bool obj_needs_vmlinux_btf(const struct bpf_object *obj) > > struct bpf_program *prog; > > int i; > > > > - /* CO-RE relocations need kernel BTF */ > > + /* CO-RE relocations need kernel BTF or an override BTF. > > + * If override BTF present CO-RE can use it. > > nit: "CO-RE relocations need kernel BTF, unless custom BTF override is > specified" > > > + */ > > if (obj->btf_ext && obj->btf_ext->core_relo_info.len) > > - return true; > > + if (!obj->btf_vmlinux_override) > > please combine this into a single if > > > + return true; > > > > /* Support for typed ksyms needs kernel BTF */ > > for (i = 0; i < obj->nr_extern; i++) { > > @@ -2561,6 +2564,27 @@ static bool obj_needs_vmlinux_btf(const struct bpf_object *obj) > > return false; > > } > > > > +static int bpf_object__load_override_btf(struct bpf_object *obj, > > + const char *targ_btf_path) > > formatting is off? scripts/checkpatch.pl -f will report > issues like this > > > +{ > > + /* Could have been be set via `bpf_object_open_opts` */ > > + if (obj->btf_vmlinux_override) > > + return 0; > > see below, let's make sure we load btf_vmlinux_override in one place > (and cleanup somewhere close) > > > + > > + if (!targ_btf_path) > > + return 0; > > + > > + obj->btf_vmlinux_override = btf__parse(targ_btf_path, NULL); > > + if (IS_ERR_OR_NULL(obj->btf_vmlinux_override)) { > > + int err = PTR_ERR(obj->btf_vmlinux_override); > > + obj->btf_vmlinux_override = NULL; > > + pr_warn("failed to parse target BTF: %d\n", err); > > + return err; > > + } > > + > > + return 0; > > +} > > + > > static int bpf_object__load_vmlinux_btf(struct bpf_object *obj, bool force) > > { > > int err; > > @@ -6031,7 +6055,7 @@ patch_insn: > > } > > > > static int > > -bpf_object__relocate_core(struct bpf_object *obj, const char *targ_btf_path) > > +bpf_object__relocate_core(struct bpf_object *obj) > > { > > const struct btf_ext_info_sec *sec; > > const struct bpf_core_relo *rec; > > @@ -6045,15 +6069,6 @@ bpf_object__relocate_core(struct bpf_object *obj, const char *targ_btf_path) > > if (obj->btf_ext->core_relo_info.len == 0) > > return 0; > > > > - if (targ_btf_path) { > > - obj->btf_vmlinux_override = btf__parse(targ_btf_path, NULL); > > - if (IS_ERR_OR_NULL(obj->btf_vmlinux_override)) { > > - err = PTR_ERR(obj->btf_vmlinux_override); > > - pr_warn("failed to parse target BTF: %d\n", err); > > - return err; > > - } > > - } > > - > > given we are moving out btf_vmlinux_override loading from > bpf_object__relocate_core, we need to move out its destruction and > cleanup to the same function that does BTF parsing. That will keep the > logic simpler. > > > cand_cache = hashmap__new(bpf_core_hash_fn, bpf_core_equal_fn, NULL); > > if (IS_ERR(cand_cache)) { > > err = PTR_ERR(cand_cache); > > @@ -6556,14 +6571,14 @@ bpf_object__relocate_calls(struct bpf_object *obj, struct bpf_program *prog) > > } > > > > static int > > -bpf_object__relocate(struct bpf_object *obj, const char *targ_btf_path) > > +bpf_object__relocate(struct bpf_object *obj) > > { > > struct bpf_program *prog; > > size_t i; > > int err; > > > > if (obj->btf_ext) { > > - err = bpf_object__relocate_core(obj, targ_btf_path); > > + err = bpf_object__relocate_core(obj); > > if (err) { > > pr_warn("failed to perform CO-RE relocations: %d\n", > > err); > > @@ -7088,7 +7103,7 @@ static struct bpf_object * > > __bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz, > > const struct bpf_object_open_opts *opts) > > { > > - const char *obj_name, *kconfig; > > + const char *obj_name, *kconfig, *core_btf_path; > > struct bpf_program *prog; > > struct bpf_object *obj; > > char tmp_name[64]; > > @@ -7126,6 +7141,14 @@ __bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz, > > return ERR_PTR(-ENOMEM); > > } > > > > + core_btf_path = OPTS_GET(opts, core_btf_path, NULL); > > + if (core_btf_path) { > > + pr_debug("parse btf '%s' for CO-RE relocations\n", core_btf_path); > > Move this right after btf__parse(), so you can report success or > failure in one log statement; see how libbpf_find_kernel_btf() does > it. Please use similar wording (just "target BTF" instead of "kernel > BTF" to distinguish them). > > > + obj->btf_vmlinux_override = btf__parse(core_btf_path, NULL); > > This BTF is not needed until the load phase, so let's not attempt to > load it on open() unnecessarily. Just remember the path and defer till > bpf_object__load() time. > > > + if (IS_ERR_OR_NULL(obj->btf_vmlinux_override)) > > + pr_warn("can't parse btf at '%s'\n", core_btf_path); > > if BTF can't be loaded, load should fail > > > + } > > + > > err = bpf_object__elf_init(obj); > > err = err ? : bpf_object__check_endianness(obj); > > err = err ? : bpf_object__elf_collect(obj); > > @@ -7481,13 +7504,14 @@ int bpf_object__load_xattr(struct bpf_object_load_attr *attr) > > } > > > > err = bpf_object__probe_loading(obj); > > + err = err ? : bpf_object__load_override_btf(obj, attr->target_btf_path); > > err = err ? : bpf_object__load_vmlinux_btf(obj, false); > > err = err ? : bpf_object__resolve_externs(obj, obj->kconfig); > > err = err ? : bpf_object__sanitize_and_load_btf(obj); > > err = err ? : bpf_object__sanitize_maps(obj); > > err = err ? : bpf_object__init_kern_struct_ops_maps(obj); > > err = err ? : bpf_object__create_maps(obj); > > - err = err ? : bpf_object__relocate(obj, attr->target_btf_path); > > For backwards compatibility, we need to still respect > attr->target_btf_path. I'd say let attr->target_btf_path override > opts->core_btf_path, if specified. Later on we'll probably just > deprecate bpf_object__load_xattr() and target_btf_path will go away. > > > + err = err ? : bpf_object__relocate(obj); > > err = err ? : bpf_object__load_progs(obj, attr->log_level); > > > > /* clean up module BTFs */ > > diff --git a/src/libbpf.h b/src/libbpf.h > > index 3c35eb4..40c4ee9 100644 > > --- a/src/libbpf.h > > +++ b/src/libbpf.h > > @@ -93,8 +93,10 @@ struct bpf_object_open_opts { > > * system Kconfig for CONFIG_xxx externs. > > */ > > const char *kconfig; > > + /* Path to ELF file with BTF section to be used for relocations. */ > > Given you use btf__parse() when opening this BTF, it handles both ELF > and raw BTF data. So let's reword this comment to mention BTF in > general. > > > + const char *core_btf_path; > > }; > > -#define bpf_object_open_opts__last_field kconfig > > +#define bpf_object_open_opts__last_field core_btf_path > > > > LIBBPF_API struct bpf_object *bpf_object__open(const char *path); > > LIBBPF_API struct bpf_object * > > -- > > 2.23.3 > >