From nobody Sat Feb 7 21:30:43 2026 Received: from mail-wm1-f73.google.com (mail-wm1-f73.google.com [209.85.128.73]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D1E8F134CFE for ; Tue, 9 Apr 2024 15:01:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.73 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712674911; cv=none; b=F5hXfJfhztOgJvELVAT/GAWYK1I0H2Wey6CPlOUeYf0ogqxGCl8q8BQdGDPdHr8EIPSB4RrfR3EAtJautq0tL5psNg55rCH0HdcDPlFz22shYCzGyX+w+1Tc4Jilot9R2i72wkZB6UjhTA8GFE+W5jwrKcfU6y3vwpeSlX71vq0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712674911; c=relaxed/simple; bh=2XRLBMqkeM5HXNl5EWou8ZB0E0TV13o8LSI5x8BSvlY=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=qCos7Q8O8cP6KV5brnmLaSZWPjYwn8QZUK0+21X4GaIE+DIly6kc3XGwwjst8Zp1hqtWKLAhqliFeYd11XRlXV4RBCQwG27UZr+Jr3EDyutAJfzFUa/7++MrUcoFD7F2t2rhdxymiG47KQSozZYmlZ6rtaAzX0su3oOfDTTOpww= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--ardb.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=Xjvwx9k3; arc=none smtp.client-ip=209.85.128.73 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--ardb.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="Xjvwx9k3" Received: by mail-wm1-f73.google.com with SMTP id 5b1f17b1804b1-4166b96002dso10630765e9.0 for ; Tue, 09 Apr 2024 08:01:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1712674907; x=1713279707; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=+c7Nae7lWjUxFMlj/H2Ns6fhkmPqVh4ydm9u7CZiONI=; b=Xjvwx9k3qQCxCqCPdMfNuiDIs0K/ej3onc8KTfYn8pWkSS4Ix8PnySLBwYMt+aAEh1 SEM5HwkuUPwEC3ftN0Oy07gEsbmWLfeJiIgRlLOH7x0d4mtVAyzQJDLOU8i18LT7XCHY bkwFtdSFCB/IIwPMfeJ4sk8WJ9HJ5fW+PELHzkz2BCRvaOH05GVK+gLYDJTZYha9kHz1 NDCN5F64Q2PVakeKVNLpSLHssJ9xB+pegmXosI5DAgv7USVVBmaYNZAq4Q24DNrozqJi Qt5kkFfMs/CpNDW9/gUToAkQRRnTrbsPkQ2vR2kO+Br5wSUsxVruyIMZ8CVGMoK/0XKi 10NQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1712674907; x=1713279707; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=+c7Nae7lWjUxFMlj/H2Ns6fhkmPqVh4ydm9u7CZiONI=; b=GsfPADCgej8qA3IMmeDEgc7KY49xW1fKHNEJWwXBC14BziPrz00shE2gKyBttHT4fC aICffvTyac0s4cZjCZmoZANYCP7yF+5TBx52ugCazQrD+eMmyzcmqNR6fMOmD6Da3mQN HdV8c3JD34/ZXu643lyPDDjFZzhzoa8FZXPLeSzlvPiWF5kiGcmYe/F5MIke7nkMMdfu g+LXAES3a2bpKUEaZ9OmaiLfMx+fsHepZnubg920TvRsU5SM6iY824ASrZNkns1q72xw W+qyfftYhZUa8fYsQ7QSvkMzsAy8muSp3wCK1CyERDNKHQeXAAqqPexgbcayT9K4EBhR ywyQ== X-Gm-Message-State: AOJu0Yw9gUa7mAUK2yCBF2SOKqvQdti0r68YDcayX5nmiIf20DGl4PuK BGmuCY/tKz0fRWsYXaChN0SpT5iupBcIDrEjox1zBMaPITfeQR5KwlSKCCqJsCnn/wzNQj7cBDL MITbic3OUgI9uJkyqAbAAYIJvan2U0o6rFSRRUrflwTOAKfKa103tkn5i1Ym77A07YDMB4WSsww tyPUqFx+zC5EGWmQJkMCZqHoIsvENG2Q== X-Google-Smtp-Source: AGHT+IFXgzgigm6gF3ssRomZsMb2tDkm1/NBAMp7/v4nwt6/VHQkX6fUKALfUDlw7BZpcWQWvAe2T1rU X-Received: from palermo.c.googlers.com ([fda3:e722:ac3:cc00:28:9cb1:c0a8:118a]) (user=ardb job=sendgmr) by 2002:a05:600c:3b29:b0:414:a0c:a82c with SMTP id m41-20020a05600c3b2900b004140a0ca82cmr31439wms.4.1712674907499; Tue, 09 Apr 2024 08:01:47 -0700 (PDT) Date: Tue, 9 Apr 2024 17:01:36 +0200 In-Reply-To: <20240409150132.4097042-5-ardb+git@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240409150132.4097042-5-ardb+git@google.com> X-Developer-Key: i=ardb@kernel.org; a=openpgp; fpr=F43D03328115A198C90016883D200E9CA6329909 X-Developer-Signature: v=1; a=openpgp-sha256; l=3124; i=ardb@kernel.org; h=from:subject; bh=AkRYLBTm6VuFUE4hRnB+rntHpPOXzattnmr7pMUxTAQ=; b=owGbwMvMwCFmkMcZplerG8N4Wi2JIU00IkD3NPOKFTu0Hs7W2XPVxMPG4eyLtet0z14zVlho3 KFyPPBNRykLgxgHg6yYIovA7L/vdp6eKFXrPEsWZg4rE8gQBi5OAZgINw/D/5zHBY8Yjzz8ViLP eCfHpP8DU+J8q72OZiqLNCeGfRA3es/IMIf9kPTBh1IGWxLPFGtVLXWe99aYPWVPvPNpXZv3S38 6MgIA X-Mailer: git-send-email 2.44.0.478.gd926399ef9-goog Message-ID: <20240409150132.4097042-8-ardb+git@google.com> Subject: [PATCH v2 3/3] btf: Avoid weak external references From: Ard Biesheuvel To: linux-kernel@vger.kernel.org Cc: Ard Biesheuvel , Masahiro Yamada , Arnd Bergmann , Martin KaFai Lau , linux-arch@vger.kernel.org, linux-kbuild@vger.kernel.org, bpf@vger.kernel.org, Andrii Nakryiko Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Ard Biesheuvel If the BTF code is enabled in the build configuration, the start/stop BTF markers are guaranteed to exist in the final link but not during the first linker pass. Avoid GOT based relocations to these markers in the final executable by providing preliminary definitions that will be used by the first linker pass, and superseded by the actual definitions in the subsequent ones. Make the preliminary definitions dependent on CONFIG_DEBUG_INFO_BTF so that inadvertent references to this section will trigger a link failure if they occur in code that does not honour CONFIG_DEBUG_INFO_BTF. Note that Clang will notice that taking the address of__start_BTF cannot yield NULL any longer, so testing for that condition is no longer needed. Acked-by: Andrii Nakryiko Signed-off-by: Ard Biesheuvel Acked-by: Arnd Bergmann --- include/asm-generic/vmlinux.lds.h | 9 +++++++++ kernel/bpf/btf.c | 4 ++-- kernel/bpf/sysfs_btf.c | 6 +++--- 3 files changed, 14 insertions(+), 5 deletions(-) diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinu= x.lds.h index e8449be62058..4cb3d88449e5 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -456,6 +456,7 @@ * independent code. */ #define PRELIMINARY_SYMBOL_DEFINITIONS \ + PRELIMINARY_BTF_DEFINITIONS \ PROVIDE(kallsyms_addresses =3D .); \ PROVIDE(kallsyms_offsets =3D .); \ PROVIDE(kallsyms_names =3D .); \ @@ -466,6 +467,14 @@ PROVIDE(kallsyms_markers =3D .); \ PROVIDE(kallsyms_seqs_of_names =3D .); =20 +#ifdef CONFIG_DEBUG_INFO_BTF +#define PRELIMINARY_BTF_DEFINITIONS \ + PROVIDE(__start_BTF =3D .); \ + PROVIDE(__stop_BTF =3D .); +#else +#define PRELIMINARY_BTF_DEFINITIONS +#endif + /* * Read only Data */ diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 90c4a32d89ff..46a56bf067a8 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -5642,8 +5642,8 @@ static struct btf *btf_parse(const union bpf_attr *at= tr, bpfptr_t uattr, u32 uat return ERR_PTR(err); } =20 -extern char __weak __start_BTF[]; -extern char __weak __stop_BTF[]; +extern char __start_BTF[]; +extern char __stop_BTF[]; extern struct btf *btf_vmlinux; =20 #define BPF_MAP_TYPE(_id, _ops) diff --git a/kernel/bpf/sysfs_btf.c b/kernel/bpf/sysfs_btf.c index ef6911aee3bb..fedb54c94cdb 100644 --- a/kernel/bpf/sysfs_btf.c +++ b/kernel/bpf/sysfs_btf.c @@ -9,8 +9,8 @@ #include =20 /* See scripts/link-vmlinux.sh, gen_btf() func for details */ -extern char __weak __start_BTF[]; -extern char __weak __stop_BTF[]; +extern char __start_BTF[]; +extern char __stop_BTF[]; =20 static ssize_t btf_vmlinux_read(struct file *file, struct kobject *kobj, @@ -32,7 +32,7 @@ static int __init btf_vmlinux_init(void) { bin_attr_btf_vmlinux.size =3D __stop_BTF - __start_BTF; =20 - if (!__start_BTF || bin_attr_btf_vmlinux.size =3D=3D 0) + if (bin_attr_btf_vmlinux.size =3D=3D 0) return 0; =20 btf_kobj =3D kobject_create_and_add("btf", kernel_kobj); --=20 2.44.0.478.gd926399ef9-goog