From patchwork Fri Aug 30 07:29:28 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tony Ambardar X-Patchwork-Id: 13784437 X-Patchwork-Delegate: bpf@iogearbox.net Received: from mail-pl1-f179.google.com (mail-pl1-f179.google.com [209.85.214.179]) (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 247651607BB; Fri, 30 Aug 2024 07:30:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.179 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725003014; cv=none; b=QzHDk0QX6kvPcdbYd8zsEyygnCcGFekiiD0TJzFlWCzqnMp7423e8tK30EdTQAnWIpvfPHhqmnM7qen9VdLrLhkMni7Y1PNdVripfqm2Jwxgknl3bAN9QLTPNQ4KCUy4f/yeK34nvHHuRH81MpZW99pKvf5LFO4f5uiV1dH+uF0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725003014; c=relaxed/simple; bh=bZFiVLxsPqJFp+7OFMaqX0ZvCLgCDYIYtrLGMsK2oz0=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=Qkm9QM13tyNacxL0nBshtGxOfJAdh9fXl/7cS0HSquXffu2tTxGCIm1ZIVZO3aBJARiZmmzpNd8ozNPFM1kyecaTiYjtdxYpKuseLc5/1eRVnt0FUtrPYCeinMHHfrUp4MTQx2cp/uJO2l3c9A4b7LnVJ2QMlBIK38ulgqJQJNg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=IwlWw4Ve; arc=none smtp.client-ip=209.85.214.179 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="IwlWw4Ve" Received: by mail-pl1-f179.google.com with SMTP id d9443c01a7336-20231aa8908so11557615ad.0; Fri, 30 Aug 2024 00:30:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1725003012; x=1725607812; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=lCLEqvYFcYfbFDmBpnULkP78s+23ipk0h/fW+02tbBM=; b=IwlWw4Ve6JZmBni/iiuimdFP+P/QCLGMTI5BbpcDp1KjznoN8uGuZjVw8BpIqTALIT VjuNYXwQPNqJOmz0MJSEarzQqd+wQqB4ZLGD9rs4fXBdSBGbENmB3RHV+ro/AAMossRU DLrOY4HITuDz+nnL68dKM+325sgrK9rKljxkdh2m2+YkrGQOEgZHuxoO0/f1GOqnHq4m l+KGnvp0sJzn9HzdE0f4xmPXAq02m9yxuHgQVCXV2+ZZT4UgrmzNv7pypiC/LGnqfA8l mpIfny7WVFxpETKu30ulrlvBBEhVnsmhKKe3opHyAJPfmZJf+feowCK1UWgCw/2N9hIU ULXA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1725003012; x=1725607812; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=lCLEqvYFcYfbFDmBpnULkP78s+23ipk0h/fW+02tbBM=; b=NjF4EYM/ADhcxWc5pO8caOMFypcyatsgJ21goZwAvYW6idQKbd0EIiLHUr9dn4UDcH b+YqAwAw9POP1oN5rOIKMT1cAitaEGq08ZosAP/AwRucLrWSF2YUFy7pAJ7aIhGaJ0QY iiM3+2pn5lV0+qjPmgFVWfNNEwaHaRKjWu+VdNveh/razKtVlSSXv6OiL3CLgDwnToUT oGZ8pBijK98AuJXmVul9slY+HGkLSVuP9gwULoLReDvJ/yqiR5ttlTixmn3r293h3Iy9 5JMTmSGhV2fZUX6BbUPDvfbwnTm96//PBbnYlRWb3u1vrxrl0ekFvoHzfBEFLtR/B9za 7GRQ== X-Forwarded-Encrypted: i=1; AJvYcCVnFPJLi3dhQuITYU7XW/Et8dDH5X4XZrLM0IpPyaCi/eIQr7q+/EkYiIirPvo+CjvosvKlp4BK40HMJQBAnIg=@vger.kernel.org X-Gm-Message-State: AOJu0YzMxlmsSMBTjkJzr4I9lfYOb6YEQn0k62hAU0yV8lO1+24aM8Fv RK/iGuzd5RAsf5NfSwxTfYz1nv+Qi0gEXApcfDJIVQbKVtQyVaNvocQ5eZsE X-Google-Smtp-Source: AGHT+IEs9SU9D0i7I40ChktQADK5+wH4dZhhKyxvKfHl0U8D/im4JnxT8BFD2i78X9laiER7tuLdYg== X-Received: by 2002:a17:903:22c6:b0:1fd:d3db:bd06 with SMTP id d9443c01a7336-2050c34f1fcmr61723295ad.2.1725003012258; Fri, 30 Aug 2024 00:30:12 -0700 (PDT) Received: from localhost.localdomain (69-172-146-21.cable.teksavvy.com. [69.172.146.21]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-205152b4dd0sm21698085ad.15.2024.08.30.00.30.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 30 Aug 2024 00:30:12 -0700 (PDT) From: Tony Ambardar To: bpf@vger.kernel.org Cc: Tony Ambardar , linux-kselftest@vger.kernel.org, Andrii Nakryiko , Eduard Zingerman , Alexei Starovoitov , Daniel Borkmann , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Mykola Lysenko , Shuah Khan , Ilya Leoshkevich , Quentin Monnet Subject: [PATCH bpf-next v4 6/8] libbpf: Support linking bpf objects of either endianness Date: Fri, 30 Aug 2024 00:29:28 -0700 Message-Id: <895753fe6de5a06dee8ac110f0c05571db73e70c.1724976539.git.tony.ambardar@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net Allow static linking object files of either endianness, checking that input files have consistent byte-order, and setting output endianness from input. Linking requires in-memory processing of programs, relocations, sections, etc. in native endianness, and output conversion to target byte-order. This is enabled by built-in ELF translation and recent BTF/BTF.ext endianness functions. Further add local functions for swapping byte-order of sections containing BPF insns. Signed-off-by: Tony Ambardar --- tools/lib/bpf/linker.c | 90 ++++++++++++++++++++++++++++++++++-------- 1 file changed, 74 insertions(+), 16 deletions(-) diff --git a/tools/lib/bpf/linker.c b/tools/lib/bpf/linker.c index 7489306cd6f7..bd97da68eed6 100644 --- a/tools/lib/bpf/linker.c +++ b/tools/lib/bpf/linker.c @@ -135,6 +135,7 @@ struct bpf_linker { int fd; Elf *elf; Elf64_Ehdr *elf_hdr; + bool swapped_endian; /* Output sections metadata */ struct dst_sec *secs; @@ -324,13 +325,8 @@ static int init_output_elf(struct bpf_linker *linker, const char *file) linker->elf_hdr->e_machine = EM_BPF; linker->elf_hdr->e_type = ET_REL; -#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ - linker->elf_hdr->e_ident[EI_DATA] = ELFDATA2LSB; -#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ - linker->elf_hdr->e_ident[EI_DATA] = ELFDATA2MSB; -#else -#error "Unknown __BYTE_ORDER__" -#endif + /* Set unknown ELF endianness, assign later from input files */ + linker->elf_hdr->e_ident[EI_DATA] = ELFDATANONE; /* STRTAB */ /* initialize strset with an empty string to conform to ELF */ @@ -541,19 +537,21 @@ static int linker_load_obj_file(struct bpf_linker *linker, const char *filename, const struct bpf_linker_file_opts *opts, struct src_obj *obj) { -#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ - const int host_endianness = ELFDATA2LSB; -#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ - const int host_endianness = ELFDATA2MSB; -#else -#error "Unknown __BYTE_ORDER__" -#endif int err = 0; Elf_Scn *scn; Elf_Data *data; Elf64_Ehdr *ehdr; Elf64_Shdr *shdr; struct src_sec *sec; + unsigned char obj_byteorder; + unsigned char link_byteorder = linker->elf_hdr->e_ident[EI_DATA]; +#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ + const unsigned char host_byteorder = ELFDATA2LSB; +#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ + const unsigned char host_byteorder = ELFDATA2MSB; +#else +#error "Unknown __BYTE_ORDER__" +#endif pr_debug("linker: adding object file '%s'...\n", filename); @@ -579,11 +577,25 @@ static int linker_load_obj_file(struct bpf_linker *linker, const char *filename, pr_warn_elf("failed to get ELF header for %s", filename); return err; } - if (ehdr->e_ident[EI_DATA] != host_endianness) { + + /* Linker output endianness set by first input object */ + obj_byteorder = ehdr->e_ident[EI_DATA]; + if (obj_byteorder != ELFDATA2LSB && obj_byteorder != ELFDATA2MSB) { + err = -EOPNOTSUPP; + pr_warn("unknown byte order of ELF file %s\n", filename); + return err; + } + if (link_byteorder == ELFDATANONE) { + linker->elf_hdr->e_ident[EI_DATA] = obj_byteorder; + linker->swapped_endian = obj_byteorder != host_byteorder; + pr_debug("linker: set %s-endian output byte order\n", + obj_byteorder == ELFDATA2MSB ? "big" : "little"); + } else if (link_byteorder != obj_byteorder) { err = -EOPNOTSUPP; - pr_warn_elf("unsupported byte order of ELF file %s", filename); + pr_warn("byte order mismatch with ELF file %s\n", filename); return err; } + if (ehdr->e_type != ET_REL || ehdr->e_machine != EM_BPF || ehdr->e_ident[EI_CLASS] != ELFCLASS64) { @@ -1111,6 +1123,27 @@ static bool sec_content_is_same(struct dst_sec *dst_sec, struct src_sec *src_sec return true; } +static bool is_exec_sec(struct dst_sec *sec) +{ + if (!sec || sec->ephemeral) + return false; + return (sec->shdr->sh_type == SHT_PROGBITS) && + (sec->shdr->sh_flags & SHF_EXECINSTR); +} + +static int exec_sec_bswap(void *raw_data, int size) +{ + const int insn_cnt = size / sizeof(struct bpf_insn); + struct bpf_insn *insn = raw_data; + int i; + + if (size % sizeof(struct bpf_insn)) + return -EINVAL; + for (i = 0; i < insn_cnt; i++, insn++) + bpf_insn_bswap(insn); + return 0; +} + static int extend_sec(struct bpf_linker *linker, struct dst_sec *dst, struct src_sec *src) { void *tmp; @@ -1170,6 +1203,10 @@ static int extend_sec(struct bpf_linker *linker, struct dst_sec *dst, struct src memset(dst->raw_data + dst->sec_sz, 0, dst_align_sz - dst->sec_sz); /* now copy src data at a properly aligned offset */ memcpy(dst->raw_data + dst_align_sz, src->data->d_buf, src->shdr->sh_size); + + /* convert added bpf insns to native byte-order */ + if (linker->swapped_endian && is_exec_sec(dst)) + exec_sec_bswap(dst->raw_data + dst_align_sz, src->shdr->sh_size); } dst->sec_sz = dst_final_sz; @@ -2630,6 +2667,10 @@ int bpf_linker__finalize(struct bpf_linker *linker) if (!sec->scn) continue; + /* restore sections with bpf insns to target byte-order */ + if (linker->swapped_endian && is_exec_sec(sec)) + exec_sec_bswap(sec->raw_data, sec->sec_sz); + sec->data->d_buf = sec->raw_data; } @@ -2698,6 +2739,7 @@ static int emit_elf_data_sec(struct bpf_linker *linker, const char *sec_name, static int finalize_btf(struct bpf_linker *linker) { + enum btf_endianness link_endianness; LIBBPF_OPTS(btf_dedup_opts, opts); struct btf *btf = linker->btf; const void *raw_data; @@ -2742,6 +2784,22 @@ static int finalize_btf(struct bpf_linker *linker) return err; } + /* Set .BTF and .BTF.ext output byte order */ + link_endianness = linker->elf_hdr->e_ident[EI_DATA] == ELFDATA2MSB ? + BTF_BIG_ENDIAN : BTF_LITTLE_ENDIAN; + err = btf__set_endianness(linker->btf, link_endianness); + if (err) { + pr_warn("failed to set .BTF output endianness: %d\n", err); + return err; + } + if (linker->btf_ext) { + err = btf_ext__set_endianness(linker->btf_ext, link_endianness); + if (err) { + pr_warn("failed to set .BTF.ext output endianness: %d\n", err); + return err; + } + } + /* Emit .BTF section */ raw_data = btf__raw_data(linker->btf, &raw_sz); if (!raw_data)