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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B7A95C433F5 for ; Tue, 12 Apr 2022 19:53:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231232AbiDLTzg (ORCPT ); Tue, 12 Apr 2022 15:55:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45008 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232475AbiDLTzU (ORCPT ); Tue, 12 Apr 2022 15:55:20 -0400 Received: from mail-pg1-x542.google.com (mail-pg1-x542.google.com [IPv6:2607:f8b0:4864:20::542]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C50326830D for ; Tue, 12 Apr 2022 12:48:11 -0700 (PDT) Received: by mail-pg1-x542.google.com with SMTP id s137so15483957pgs.5 for ; Tue, 12 Apr 2022 12:48:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=DT+bSrdLBlVwt4kyO/I8QPjgT0HTcOAun/NTUSpYZdw=; b=WE97K6/HhUwBAtZvOpX2gTVliAcr+BjcIGJTeyMBZKAVHymRvlVT/8eb/+hKC9Z95P 6f3pdI2uaudJ/CMN2jhidfWLvByxxawAKr8RgDPq2C5iuKCfBvkvZZgGeTQeu0xvS/ab Sf0vENfjMzS33Pt1rt90IBYncx+iLe1ZqrRgpSjnvMU7dC+0WYmQERURM+qNgcVkSG6Y /5D6vkD/L/omHHR5wGzprtR0kRbdV65dH5iysQShJFoRiGoPmp/+osJuk7f/v8mty3s/ QImNkREVHmoshm/Qkfujs0i1FplIf4AN9fTVv1P33wUaTuvgWIrgWDY9bpdHGfthuehZ 2+ZA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=DT+bSrdLBlVwt4kyO/I8QPjgT0HTcOAun/NTUSpYZdw=; b=PsBbpkn7lqPN1SrCGejd0UnFsQqp2z8PoXU9VFIOoeHPH1OhvGWUY7p+MRT4bJHDPD TqpuN2VJmFXbbaD3HNdRZgUh/2FSpRaMorenn1L+ksPE267qukDYFgDbbHGbKv5nj9Uy rmWG9fTEc90dvd/z56mCTy6Pxsm+6ZqvW3N9vXtgLyY4+iVYHEaKvts1Bzz1SuU4l9YR 1rUJEkCgK+TzWTkMIZ5ek0pTpnTOehVqTVmYX/323JhNM3RgNyQnH8QLz7OISPRg2fPo NHHAArVWI38XB1MWhTGtXafdDuUL8X4V6s2IDn+n2UUGZutNlYCPND2vZBrjeC+FSs2h x1WQ== X-Gm-Message-State: AOAM531lV+yVxOfImUXltCpGW7mxKmsak6zOqPw7AoX/NoMYwQdCQcOx CXS6x+1YHReku5onZNelBYN0rGBBjT/g5Q== X-Google-Smtp-Source: ABdhPJxH8dU0oIQhTgaLKTGHoCCnY6TggkQ65Lep4N126QH3jtmB8CJQOoBNw+veivqSPxSV7QFE6Q== X-Received: by 2002:a63:e5c:0:b0:39d:8460:4708 with SMTP id 28-20020a630e5c000000b0039d84604708mr5921071pgo.401.1649792890868; Tue, 12 Apr 2022 12:48:10 -0700 (PDT) Received: from localhost ([112.79.143.3]) by smtp.gmail.com with ESMTPSA id p64-20020a622943000000b004fdd5c07d0bsm37165092pfp.63.2022.04.12.12.48.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 12 Apr 2022 12:48:10 -0700 (PDT) Date: Wed, 13 Apr 2022 01:18:09 +0530 From: Kumar Kartikeya Dwivedi To: Joanne Koong Cc: bpf , Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= , Jesper Dangaard Brouer Subject: Re: [PATCH bpf-next v4 01/13] bpf: Make btf_find_field more generic Message-ID: <20220412194809.l5lfslbrzohrgnnc@apollo.legion> References: <20220409093303.499196-1-memxor@gmail.com> <20220409093303.499196-2-memxor@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Tue, Apr 12, 2022 at 01:50:28AM IST, Joanne Koong wrote: > On Sat, Apr 9, 2022 at 2:32 AM Kumar Kartikeya Dwivedi wrote: > > > > Next commit introduces field type 'kptr' whose kind will not be struct, > > but pointer, and it will not be limited to one offset, but multiple > > ones. Make existing btf_find_struct_field and btf_find_datasec_var > > functions amenable to use for finding kptrs in map value, by moving > > spin_lock and timer specific checks into their own function. > > > > The alignment, and name are checked before the function is called, so it > > is the last point where we can skip field or return an error before the > > next loop iteration happens. The name parameter is now optional, and > > only checked if it is not NULL. Size of the field and type is meant to > > be checked inside the function, and base type will need to be obtained > > by skipping modifiers. > > > > Signed-off-by: Kumar Kartikeya Dwivedi > > --- > > kernel/bpf/btf.c | 129 +++++++++++++++++++++++++++++++++++------------ > > 1 file changed, 96 insertions(+), 33 deletions(-) > > > > diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c > > index 0918a39279f6..db7bf05adfc5 100644 > > --- a/kernel/bpf/btf.c > > +++ b/kernel/bpf/btf.c > > @@ -3163,71 +3163,126 @@ static void btf_struct_log(struct btf_verifier_env *env, > > btf_verifier_log(env, "size=%u vlen=%u", t->size, btf_type_vlen(t)); > > } > > > > +enum { > > + BTF_FIELD_SPIN_LOCK, > > + BTF_FIELD_TIMER, > > +}; > > + > > +struct btf_field_info { > > + u32 off; > > +}; > > + > > +static int btf_find_field_struct(const struct btf *btf, const struct btf_type *t, > > + u32 off, int sz, struct btf_field_info *info) > > +{ > > + if (!__btf_type_is_struct(t)) > > + return 0; > > + if (t->size != sz) > > + return 0; > Do we need these two checks? I think in the original version we did > because we were checking this before doing the name comparison, but > now that the name comparison check is first, if the struct name is a > match, then won't these two things always be true (or if not, then it > seems like we should return -EINVAL)? But maybe I'm missing something > here - I'm still getting more familiar with BTF :) The name can be the same, but since this comes from map BTF, it could be a different struct with the same name string in the map BTF, with a different size as well. So checking both is still needed. Returning -EINVAL now would be backwards incompatible, code this is replacing continues when it doesn't find struct with the required size. > > Also, as a side-note: I personally find this function name > "btf_find_field_struct" confusing since there's also the > "btf_find_struct_field" function that exists. I wonder whether we > should just keep the logic inside btf_find_struct_field instead of > putting it in this separate function? I'm open to renaming, how about we just call it btf_find_struct? Then in the next patch I could rename btf_find_field_kptr to btf_find_kptr. > > > + if (info->off != -ENOENT) > > + /* only one such field is allowed */ > > + return -E2BIG; > In the future, do you plan to add support for multiple fields? I think > this would be useful for dynptrs as well, so just curious what your > plans for this are. In the next patch it is modified to deal with one info at once, so supporting multiple fields is a matter of passing different info_cnt. It won't do this info->off check to ensure it only saw one field from next patch, that will be handled outside in the loop. > > + info->off = off; > > + return 0; > > +} > > + > > static int btf_find_struct_field(const struct btf *btf, const struct btf_type *t, > > - const char *name, int sz, int align) > > + const char *name, int sz, int align, int field_type, > > What are your thoughts on just passing in field_type in place of name, > sz, and align? As in a function signature like: > > static int btf_find_struct_field(const struct btf *btf, const struct > btf_type *t, int field_type, struct btf_field_info *info); > > where inside btf_find_struct_field when we do the switch statement on > field_type, we can have the name, sz, and align for each of the > different field types there? That to me seems a bit cleaner where the > descriptors for the field types are all in one place (instead of also > in btf_find_spin_lock() and btf_find_timer() functions) and the > function definition for btf_find_struct_field is more straightforward. > At that point, I don't think we'd even need btf_find_spin_lock() and > btf_find_timer() as functions since it'd be just a straightforward > "btf_find_field(btf, t, BTF_FIELD_SPIN_LOCK/BTF_FIELD_TIMER)" call > instead. Curious to hear your thoughts. Isn't btf_find_field doing exactly this? btf_find_timer e.g. only passed BTF_FIELD_TIMER; name, sz, and alignment come from btf_find_field. Also, after btf_find_field, there needs to be handling for the info that was populated. In case of timer and spin_lock, we just return the offset, but in case of kptrs we populate the kptr_off_tab. If we move this inside btf_find_field, then it would be done based on field type inside the same function (either using if/else or switch cases), not sure that is cleaner than doing it in separate wrappers. > > nit: should field_type be a u32 since it's an enum? Or should we be > explicit and give the enum a name and define this as something like > "enum btf_field_type type"? > Ok, I'll do that (since I'm respinning anyway), though it doesn't really matter, the underlying type is still int in C. > > + struct btf_field_info *info) > > { > > const struct btf_member *member; > > - u32 i, off = -ENOENT; > > + u32 i, off; > > + int ret; > > > > for_each_member(i, t, member) { > > const struct btf_type *member_type = btf_type_by_id(btf, > > member->type); > > - if (!__btf_type_is_struct(member_type)) > > - continue; > > - if (member_type->size != sz) > > - continue; > > - if (strcmp(__btf_name_by_offset(btf, member_type->name_off), name)) > > - continue; > > - if (off != -ENOENT) > > - /* only one such field is allowed */ > > - return -E2BIG; > > + > > off = __btf_member_bit_offset(t, member); > nit: should this be moved to after the strcmp on the name? Since if > the name doesn't match, there's no point in doing this > __btf_member_bit_offset call Ack. > > + > > + if (name && strcmp(__btf_name_by_offset(btf, member_type->name_off), name)) > I'm confused by the if (name) part of the check. If name is NULL, then > won't this "btf_find_struct_field" function always return the offset > to the first struct? I don't think name will ever be NULL so maybe we > should just remove this? Or do something like if (name) return > -EINVAL; before doing the strcmp? > I'll move it to the next patch, since you noted there that you realised this is for kptr. > > + continue; > > if (off % 8) > > /* valid C code cannot generate such BTF */ > > return -EINVAL; > > off /= 8; > > if (off % align) > > return -EINVAL; > > + > > + switch (field_type) { > > + case BTF_FIELD_SPIN_LOCK: > > + case BTF_FIELD_TIMER: > > + ret = btf_find_field_struct(btf, member_type, off, sz, info); > nit: I think we can just do "return btf_find_field_struct(btf, > member_type, off, sz, info);" here and remove the "int ret;" > declaration a few lines above. > Ack. > > + if (ret < 0) > > + return ret; > > + break; > > + default: > > + return -EFAULT; > > + } > > } > > - return off; > > + return 0; > > } > > > > static int btf_find_datasec_var(const struct btf *btf, const struct btf_type *t, > > - const char *name, int sz, int align) > > + const char *name, int sz, int align, int field_type, > > + struct btf_field_info *info) > The same comments for the btf_find_struct_field function also apply to > this function > > { > > const struct btf_var_secinfo *vsi; > > - u32 i, off = -ENOENT; > > + u32 i, off; > > + int ret; > > > > for_each_vsi(i, t, vsi) { > > const struct btf_type *var = btf_type_by_id(btf, vsi->type); > > const struct btf_type *var_type = btf_type_by_id(btf, var->type); > > > > - if (!__btf_type_is_struct(var_type)) > > - continue; > > - if (var_type->size != sz) > > + off = vsi->offset; > > + > > + if (name && strcmp(__btf_name_by_offset(btf, var_type->name_off), name)) > > continue; > > if (vsi->size != sz) > > continue; > > - if (strcmp(__btf_name_by_offset(btf, var_type->name_off), name)) > > - continue; > > - if (off != -ENOENT) > > - /* only one such field is allowed */ > > - return -E2BIG; > > - off = vsi->offset; > > if (off % align) > > return -EINVAL; > > + > > + switch (field_type) { > > + case BTF_FIELD_SPIN_LOCK: > > + case BTF_FIELD_TIMER: > > + ret = btf_find_field_struct(btf, var_type, off, sz, info); > > + if (ret < 0) > > + return ret; > > + break; > > + default: > > + return -EFAULT; > > + } > > } > > - return off; > > + return 0; > > } > > > > static int btf_find_field(const struct btf *btf, const struct btf_type *t, > > - const char *name, int sz, int align) > > + int field_type, struct btf_field_info *info) > > { > > + const char *name; > > + int sz, align; > > + > > + switch (field_type) { > > + case BTF_FIELD_SPIN_LOCK: > > + name = "bpf_spin_lock"; > > + sz = sizeof(struct bpf_spin_lock); > > + align = __alignof__(struct bpf_spin_lock); > > + break; > > + case BTF_FIELD_TIMER: > > + name = "bpf_timer"; > > + sz = sizeof(struct bpf_timer); > > + align = __alignof__(struct bpf_timer); > > + break; > > + default: > > + return -EFAULT; > > + } > > > > if (__btf_type_is_struct(t)) > > - return btf_find_struct_field(btf, t, name, sz, align); > > + return btf_find_struct_field(btf, t, name, sz, align, field_type, info); > > else if (btf_type_is_datasec(t)) > > - return btf_find_datasec_var(btf, t, name, sz, align); > > + return btf_find_datasec_var(btf, t, name, sz, align, field_type, info); > > return -EINVAL; > > } > > > > @@ -3237,16 +3292,24 @@ static int btf_find_field(const struct btf *btf, const struct btf_type *t, > > */ > > int btf_find_spin_lock(const struct btf *btf, const struct btf_type *t) > > { > > - return btf_find_field(btf, t, "bpf_spin_lock", > > - sizeof(struct bpf_spin_lock), > > - __alignof__(struct bpf_spin_lock)); > > + struct btf_field_info info = { .off = -ENOENT }; > > + int ret; > > + > > + ret = btf_find_field(btf, t, BTF_FIELD_SPIN_LOCK, &info); > I'm confused about why we pass in "struct btf_field_info" as the out > parameter. Maybe I'm missing something here, but why can't > "btf_find_field" just return back the offset? > > + if (ret < 0) > > + return ret; > > + return info.off; > > } > > > > int btf_find_timer(const struct btf *btf, const struct btf_type *t) > > { > > - return btf_find_field(btf, t, "bpf_timer", > > - sizeof(struct bpf_timer), > > - __alignof__(struct bpf_timer)); > > + struct btf_field_info info = { .off = -ENOENT }; > > + int ret; > > + > > + ret = btf_find_field(btf, t, BTF_FIELD_TIMER, &info); > > + if (ret < 0) > > + return ret; > > + return info.off; > > } > > > > static void __btf_struct_show(const struct btf *btf, const struct btf_type *t, > > -- > > 2.35.1 > > -- Kartikeya