From patchwork Thu Jul 4 00:15:26 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrii Nakryiko X-Patchwork-Id: 13723084 X-Patchwork-Delegate: bpf@iogearbox.net Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 B2A0E632 for ; Thu, 4 Jul 2024 00:15:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720052138; cv=none; b=uK/7WGMUN3hE4fX51ByCLfevLwONovv6MERNWnzDmkBmCee4kBAIVjWtc1cd3QdJm4sb2NuhPzb2llEo6TKWXNl7LsGgBdwBp22M5xXcpIeoFq/01i8dnFGPxU9sV7i00rZwPJfChPWBx4xQcXg7+Pdm1nq2zjTU0ilFkULTDQ0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720052138; c=relaxed/simple; bh=rGJS1Gip8J3PXd2zZvyrPXYrmKtfnpq1nmbtNkpWzxE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=dN+y4eLumVJA3KWTVna6GOp5gfMugHCszraQBu4I9wb5AwolHLIWvLghUeJX1XFcxts5Pvvh4CksgyEPCB6EnNrlEc/2Q1XkQ5uYavOSY1gfaMlioOxwOYVBrPEOKCYYK1tR3Qgj8rg7EKyJJFZNlIY8zhRTOjKKPh/J0Gp0QZo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=fdoZdnCM; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="fdoZdnCM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2A5B8C2BD10; Thu, 4 Jul 2024 00:15:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1720052138; bh=rGJS1Gip8J3PXd2zZvyrPXYrmKtfnpq1nmbtNkpWzxE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=fdoZdnCMGSpcKGI3RvKbsZ2XlwOgULdiYXVDtQ0M9TF3PzvDHkcisz9UDDZSnf/cF NnB0WETzBQSJHWUq1hzzT3S1ovHJsltZ5+JPqmGm8iVgXD9J8SsTGvq+BQYwgLNCOY A6LKo742wbR2/ue3t3bd2uW/mpdx5fh5LgUeWswIQr725UGP5IGliiLX+nVvOr7Nbn ziJFtvNkJ4Y22txO4gyRvGJwQxkTQ9WomJ0/I/hhPivjsTGea88PHwsEGKC8Epry9X m4FzXUX/hVvGO6hKPTw+R3Y3LyVJUHjANpGNVm0LQ4SrwcSJdamBQPJ3Z0/9z07yv6 NC+m47LYr7p4Q== From: Andrii Nakryiko To: bpf@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net, martin.lau@kernel.org Cc: andrii@kernel.org, kernel-team@meta.com, Mykyta Yatsenko Subject: [PATCH bpf-next 1/2] bpftool: improve skeleton backwards compat with old buggy libbpfs Date: Wed, 3 Jul 2024 17:15:26 -0700 Message-ID: <20240704001527.754710-2-andrii@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240704001527.754710-1-andrii@kernel.org> References: <20240704001527.754710-1-andrii@kernel.org> 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 Old versions of libbpf don't handle varying sizes of bpf_map_skeleton struct correctly. As such, BPF skeleton generated by newest bpftool might not be compatible with older libbpf (though only when libbpf is used as a shared library), even though it, by design, should. Going forward libbpf will be fixed, plus we'll release bug fixed versions of relevant old libbpfs, but meanwhile try to mitigate from bpftool side by conservatively assuming older and smaller definition of bpf_map_skeleton, if possible. Meaning, if there are no struct_ops maps. If there are struct_ops, then presumably user would like to have auto-attaching logic and struct_ops map link placeholders, so use the full bpf_map_skeleton definition in that case. Co-developed-by: Mykyta Yatsenko Signed-off-by: Andrii Nakryiko Acked-by: Quentin Monnet --- tools/bpf/bpftool/gen.c | 46 ++++++++++++++++++++++++++++------------- 1 file changed, 32 insertions(+), 14 deletions(-) diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c index 51eaed76db97..70aaa32ddcc9 100644 --- a/tools/bpf/bpftool/gen.c +++ b/tools/bpf/bpftool/gen.c @@ -852,24 +852,41 @@ codegen_maps_skeleton(struct bpf_object *obj, size_t map_cnt, bool mmaped, bool { struct bpf_map *map; char ident[256]; - size_t i; + size_t i, map_sz; if (!map_cnt) return; + /* for backward compatibility with old libbpf versions that don't + * handle new BPF skeleton with new struct bpf_map_skeleton definition + * that includes link field, avoid specifying new increased size, + * unless we absolutely have to (i.e., if there are struct_ops maps + * present) + */ + map_sz = offsetof(struct bpf_map_skeleton, link); + if (populate_links) { + bpf_object__for_each_map(map, obj) { + if (bpf_map__type(map) == BPF_MAP_TYPE_STRUCT_OPS) { + map_sz = sizeof(struct bpf_map_skeleton); + break; + } + } + } + codegen("\ \n\ - \n\ + \n\ /* maps */ \n\ s->map_cnt = %zu; \n\ - s->map_skel_sz = sizeof(*s->maps); \n\ - s->maps = (struct bpf_map_skeleton *)calloc(s->map_cnt, s->map_skel_sz);\n\ + s->map_skel_sz = %zu; \n\ + s->maps = (struct bpf_map_skeleton *)calloc(s->map_cnt,\n\ + sizeof(*s->maps) > %zu ? sizeof(*s->maps) : %zu);\n\ if (!s->maps) { \n\ err = -ENOMEM; \n\ goto err; \n\ } \n\ ", - map_cnt + map_cnt, map_sz, map_sz, map_sz ); i = 0; bpf_object__for_each_map(map, obj) { @@ -878,23 +895,22 @@ codegen_maps_skeleton(struct bpf_object *obj, size_t map_cnt, bool mmaped, bool codegen("\ \n\ - \n\ - s->maps[%zu].name = \"%s\"; \n\ - s->maps[%zu].map = &obj->maps.%s; \n\ + \n\ + map = (struct bpf_map_skeleton *)((char *)s->maps + %zu * s->map_skel_sz);\n\ + map->name = \"%s\"; \n\ + map->map = &obj->maps.%s; \n\ ", - i, bpf_map__name(map), i, ident); + i, bpf_map__name(map), ident); /* memory-mapped internal maps */ if (mmaped && is_mmapable_map(map, ident, sizeof(ident))) { - printf("\ts->maps[%zu].mmaped = (void **)&obj->%s;\n", - i, ident); + printf("\tmap->mmaped = (void **)&obj->%s; \n", ident); } if (populate_links && bpf_map__type(map) == BPF_MAP_TYPE_STRUCT_OPS) { codegen("\ \n\ - s->maps[%zu].link = &obj->links.%s;\n\ - ", - i, ident); + map->link = &obj->links.%s; \n\ + ", ident); } i++; } @@ -1463,6 +1479,7 @@ static int do_skeleton(int argc, char **argv) %1$s__create_skeleton(struct %1$s *obj) \n\ { \n\ struct bpf_object_skeleton *s; \n\ + struct bpf_map_skeleton *map __attribute__((unused));\n\ int err; \n\ \n\ s = (struct bpf_object_skeleton *)calloc(1, sizeof(*s));\n\ @@ -1753,6 +1770,7 @@ static int do_subskeleton(int argc, char **argv) { \n\ struct %1$s *obj; \n\ struct bpf_object_subskeleton *s; \n\ + struct bpf_map_skeleton *map __attribute__((unused));\n\ int err; \n\ \n\ obj = (struct %1$s *)calloc(1, sizeof(*obj)); \n\