From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from 69-171-232-180.mail-mxout.facebook.com (69-171-232-180.mail-mxout.facebook.com [69.171.232.180]) (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 6C2DF4FC346 for ; Mon, 21 Sep 2026 21:02:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=69.171.232.180 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790024532; cv=none; b=XvI3wAB7T6c2dzfaYD/UCgJ/LnsitkaciTCpCrrKCxyDafO7r8voQX7A1C8k0LN9pSu17Yrr8eRvbzz7kbt+/29VypmzWCP9bSamS4JRWYAgEPOnW56k9hTQ1+Z7algQP294plJom8CCAbwW5Nr5gG+X/FiqAbV4emVQBbkYNZE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790024532; c=relaxed/simple; bh=iarMN/JqHMbmZQyHNdWDjYVeerZxdk8Vj7LaP2cqgy8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=HEhbONrH/CJvuAoT6R5EmSSJyDye58F6280AKi25LlJEhNV4XN4U+Vx+e5759sf9s2kzsGLdaSbS0y/wdhg7JPD0tzXjU+E5wqOye7iYkzSETO2kImskRy/DQfnbr1zU8JUJE8eT3Ssz9QP5WwL0d93N2qxsLLGAbV+48Jw+5xw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.dev; spf=fail smtp.mailfrom=linux.dev; arc=none smtp.client-ip=69.171.232.180 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=linux.dev Received: by devvm16039.vll0.facebook.com (Postfix, from userid 128203) id 7A09C2C4497D7F; Mon, 21 Sep 2026 14:02:00 -0700 (PDT) From: Yonghong Song To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Eduard Zingerman , kernel-team@fb.com Subject: [PATCH bpf-next v4 17/20] libbpf: Let the static linker carry .bpf_cleanup relocations Date: Mon, 21 Sep 2026 14:02:00 -0700 Message-ID: <20260921210200.1723894-1-yonghong.song@linux.dev> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260921210033.1715000-1-yonghong.song@linux.dev> References: <20260921210033.1715000-1-yonghong.song@linux.dev> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable An object that carries a compiler-emitted exception cleanup table cannot = be linked today. The table's fields are byte offsets into a code section, materialised by a 32-bit relocation against that section's symbol with th= e offset itself as the implicit addend, and the linker rejects both halves = of that: the relocation type is not in the list it accepts, and a relocation against an STT_SECTION symbol from a non-executable section is an outrigh= t error. Both spellings of that relocation have to be taken. LLVM emits R_BPF_64_NODYLD32 for a .long against a section symbol; GNU as emits R_BPF_64_ABS32, which is what bpf_reloc_type_lookup() maps BFD_RELOC_32 t= o. They describe the same value, and the selftests are built with both compilers. Taking them is keyed on the relocation type rather than on the section name, so any non-executable section could reach the new arm, and what it replaces is an unconditional refusal. Check what the refusal used to make unnecessary: a relocated section may be SHT_NOBITS, which extend_sec() leaves with no raw_data, and r_offset is checked for alignment only where the section holds instructions. Refuse those rather than write through them. Signed-off-by: Yonghong Song --- tools/lib/bpf/linker.c | 36 +++++++++++++++++++++++++++++++++++- 1 file changed, 35 insertions(+), 1 deletion(-) diff --git a/tools/lib/bpf/linker.c b/tools/lib/bpf/linker.c index 78f92c39290a..1f512eff5895 100644 --- a/tools/lib/bpf/linker.c +++ b/tools/lib/bpf/linker.c @@ -1036,7 +1036,8 @@ static int linker_sanity_check_elf_relos(struct src= _obj *obj, struct src_sec *se size_t sym_type =3D ELF64_R_TYPE(relo->r_info); =20 if (sym_type !=3D R_BPF_64_64 && sym_type !=3D R_BPF_64_32 && - sym_type !=3D R_BPF_64_ABS64 && sym_type !=3D R_BPF_64_ABS32) { + sym_type !=3D R_BPF_64_ABS64 && sym_type !=3D R_BPF_64_ABS32 && + sym_type !=3D R_BPF_64_NODYLD32) { pr_warn("ELF relo #%d in section #%zu has unexpected type %zu in %s\n= ", i, sec->sec_idx, sym_type, obj->filename); return -EINVAL; @@ -2258,6 +2259,7 @@ static int linker_append_elf_relos(struct bpf_linke= r *linker, struct src_obj *ob if (ELF64_ST_TYPE(src_sym->st_info) =3D=3D STT_SECTION) { struct src_sec *sec =3D &obj->secs[src_sym->st_shndx]; struct bpf_insn *insn; + __u32 *val; =20 if (src_linked_sec->shdr->sh_flags & SHF_EXECINSTR) { /* calls to the very first static function inside @@ -2274,6 +2276,38 @@ static int linker_append_elf_relos(struct bpf_link= er *linker, struct src_obj *ob insn->imm +=3D sec->dst_off / sizeof(struct bpf_insn); else insn->imm +=3D sec->dst_off; + } else if (sym_type =3D=3D R_BPF_64_NODYLD32 || + sym_type =3D=3D R_BPF_64_ABS32) { + /* Two spellings of the one thing: LLVM + * emits NODYLD32 for a .long against a + * section symbol, GNU as emits ABS32 + * (bpf_reloc_type_lookup() maps + * BFD_RELOC_32 to it), and the value + * they describe is the same. + */ + + /* Only an executable section has its + * r_offset checked, and even there only + * for alignment; SHT_NOBITS has no + * raw_data at all. Bound it here, + * subtracting so it cannot wrap. + */ + if (!dst_linked_sec->raw_data || + dst_linked_sec->sec_sz < (int)sizeof(*val) || + dst_rel->r_offset % sizeof(*val) || + dst_rel->r_offset > + (size_t)dst_linked_sec->sec_sz - sizeof(*val)) { + pr_warn("ELF relo #%d in section #%zu points outside the data of s= ection '%s' in %s\n", + j, src_sec->sec_idx, + dst_linked_sec->sec_name, + obj->filename); + return -EINVAL; + } + val =3D dst_linked_sec->raw_data + dst_rel->r_offset; + if (linker->swapped_endian) + *val =3D bswap_32(bswap_32(*val) + sec->dst_off); + else + *val +=3D sec->dst_off; } else { pr_warn("relocation against STT_SECTION in non-exec section is not = supported!\n"); return -EINVAL; --=20 2.53.0-Meta