From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-177.mta0.migadu.com (out-177.mta0.migadu.com [91.218.175.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6BD1741D637 for ; Thu, 6 Aug 2026 21:14:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.177 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786050852; cv=none; b=GC+g641wV36SnCpo+g5Rb2BzgHWZzCed7ZWmtiyDucP06kTrmRO7qrA1jJ7KgDdeya+qfi1PYGOQMgXa/pBkmwhDH1v06szrmp4kUhyBjmUzK/CeBKwovYvJ0AGT73Kl8Keyt1uf+WpPAqje/q+y4kYBO+Es+BidQfykS2F33Y0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786050852; c=relaxed/simple; bh=Y7j+vHz5ifg+awfBMpMmqyogGa/aB+LwlKJSG3YrdLE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=cpbA6wHvC25Cqva1mLvViwgQ3pQjvk/8JCR3aYAn9YbjeI8fYq1bHJW5YUQpfFgyTS/NzgVuASmra531/tiuoYKD4LZMkKTm7MZA+Qjax1YQMB9j2SDozzrT/L+XP1iq+EI/o99kHyCVdlUssBmLL1dA0bMd03k7/Q+mLGVibRs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=RTzMxtY/; arc=none smtp.client-ip=91.218.175.177 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="RTzMxtY/" Message-ID: <33b6923a-51ed-4e6f-b41a-8780992fa262@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1786050844; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=6/6Jrn204tkhstHg8N9Afe3wZPFehkOUPkVqH18ofNo=; b=RTzMxtY/6D5I1qeAi55XFme58Bznp71UU7T1Rje/4Ts/SA0Ra/Cf+ckYFDFTVD2ixl/158 fK405RVaJgNVcDfvLDV+uFMQp9MJ3IUnRuLx7E7f9RAWYo0Ztg8MIWO1MVYzlZAaqh09wz mMzAcSg6DF0fk7iqsVEMAG6NaGpX2rs= Date: Thu, 6 Aug 2026 14:13:59 -0700 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH bpf-next v2 6/6] docs, resolve_btfids: Document kfunc BTF annotation emission To: bot+bpf-ci@kernel.org, ast@kernel.org, andrii@kernel.org, daniel@iogearbox.net, eddyz87@gmail.com, memxor@gmail.com Cc: alan.maguire@oracle.com, jolsa@kernel.org, emil@etsalapatis.com, bpf@vger.kernel.org, martin.lau@kernel.org, yonghong.song@linux.dev, clm@meta.com References: <20260805230648.2354989-7-ihor.solodrai@linux.dev> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Ihor Solodrai In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 8/5/26 5:01 PM, bot+bpf-ci@kernel.org wrote: >> diff --git a/Documentation/bpf/kfuncs.rst b/Documentation/bpf/kfuncs.rst >> index cbde86d082cce..c60fc574e8b06 100644 >> --- a/Documentation/bpf/kfuncs.rst >> +++ b/Documentation/bpf/kfuncs.rst >> @@ -472,6 +472,14 @@ type. An example is shown below:: >> } >> late_initcall(init_subsystem); >> >> +At kernel build time the ``resolve_btfids`` tool discovers all kfuncs from the >> +registered ``BTF_SET8_KFUNCS`` sets and emits their BTF annotations into the >> +kernel's BTF; these annotations were historically produced by pahole. For each >> +discovered kfunc ``resolve_btfids`` emits a ``bpf_kfunc`` BTF decl tag, a >> +``bpf_fastcall`` decl tag when the kfunc is flagged ``KF_FASTCALL``, and the >> +``address_space(1)`` type attribute on the return value and/or arguments flagged >> +``KF_ARENA_RET``, ``KF_ARENA_ARG1`` or ``KF_ARENA_ARG2`` (see section 2.8). > > Emil Tsalapatis suggested in v1 replacing "address_space(1)" with "arena" > throughout the documentation for better readability. This nit was not > addressed in v2. > > The term "address_space(1)" appears in four locations across this commit > (kfuncs.rst, changes.rst, Makefile.btf, and main.c). Would using "arena" > be clearer, especially since the code already defines TYPE_ATTR_ARENA? Nonsense feedback from the bot. Ignoring. > >> + >> 2.7 Specifying no-cast aliases with ___init >> -------------------------------------------- >> >> diff --git a/Documentation/process/changes.rst b/Documentation/process/changes.rst >> index 1ca8c5f73ad00..6d1dbe4abf0f0 100644 >> --- a/Documentation/process/changes.rst >> +++ b/Documentation/process/changes.rst >> @@ -147,10 +147,9 @@ Since Linux 5.2, if CONFIG_DEBUG_INFO_BTF is selected, the build system >> generates BTF (BPF Type Format) from DWARF in vmlinux, a bit later from kernel >> modules as well. This requires pahole v1.22 or later. >> >> -Since Linux 7.0, kfuncs annotated with KF_IMPLICIT_ARGS require pahole v1.26 >> -or later. Without it, such kfuncs will have incorrect BTF prototypes in >> -vmlinux, causing BPF programs to fail to load with a "func_proto incompatible >> -with vmlinux" error. Many sched_ext kfuncs are affected. >> +Kfunc BTF annotations (the bpf_kfunc and bpf_fastcall decl tags and the arena >> +address_space(1) type attribute) are emitted in-tree by resolve_btfids from the >> +BTF_KFUNCS sets, so they no longer depend on a specific pahole version. >> >> It is found in the 'dwarves' or 'pahole' distro packages or from >> https://fedorapeople.org/~acme/dwarves/. >> diff --git a/scripts/Makefile.btf b/scripts/Makefile.btf >> index a1812985a61aa..717e76ce96a71 100644 >> --- a/scripts/Makefile.btf >> +++ b/scripts/Makefile.btf >> @@ -14,6 +14,9 @@ pahole-flags-$(call test-ge, $(pahole-ver), 125) += --skip_encoding_btf_inconsis >> else >> >> # Switch to using --btf_features for v1.26 and later. >> +# >> +# kfunc BTF annotations (bpf_kfunc/bpf_fastcall decl tags and the arena >> +# address_space(1) type attribute) are emitted by resolve_btfids, not pahole. >> pahole-flags-$(call test-ge, $(pahole-ver), 126) = -j$(JOBS) --btf_features=encode_force,var,float,enum64,decl_tag,type_tag,optimized_func,consistent_func >> >> pahole-flags-$(call test-ge, $(pahole-ver), 131) += --btf_features=layout >> diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c >> index ea25ca34aa006..66f4014e6aa17 100644 >> --- a/tools/bpf/resolve_btfids/main.c >> +++ b/tools/bpf/resolve_btfids/main.c >> @@ -58,6 +58,17 @@ >> * __BTF_ID__func__vfs_fallocate__5: >> * .zero 4 >> * .word (1 << 3) | (1 << 1) | (1 << 2) >> + * >> + * In addition to resolving BTF IDs, resolve_btfids performs kernel-specific >> + * BTF-to-BTF transformations for kfuncs found in BTF_SET8_KFUNCS sets. For >> + * each such kfunc it: >> + * >> + * - emits a "bpf_kfunc" decl tag, and "bpf_fastcall" when KF_FASTCALL is set; >> + * - wraps the return value and/or arguments flagged KF_ARENA_RET, >> + * KF_ARENA_ARG1 or KF_ARENA_ARG2 with the "address_space(1)" type attribute; >> + * - rewrites the prototype of KF_IMPLICIT_ARGS kfuncs. >> + * >> + * These kfunc annotations were historically produced by pahole. >> */ >> >> #define _GNU_SOURCE > > > --- > AI reviewed your patch. Please fix the bug or email reply why it's not a bug. > See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md > > CI run summary: https://github.com/kernel-patches/bpf/actions/runs/31056256483