From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6F4F2C07E99 for ; Mon, 12 Jul 2021 12:55:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 46C9D610CB for ; Mon, 12 Jul 2021 12:55:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234132AbhGLM5x (ORCPT ); Mon, 12 Jul 2021 08:57:53 -0400 Received: from out3-smtp.messagingengine.com ([66.111.4.27]:40985 "EHLO out3-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234098AbhGLM5x (ORCPT ); Mon, 12 Jul 2021 08:57:53 -0400 Received: from compute6.internal (compute6.nyi.internal [10.202.2.46]) by mailout.nyi.internal (Postfix) with ESMTP id A53D15C01A8; Mon, 12 Jul 2021 08:55:03 -0400 (EDT) Received: from mailfrontend1 ([10.202.2.162]) by compute6.internal (MEProxy); Mon, 12 Jul 2021 08:55:03 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:content-transfer-encoding:date:from :message-id:mime-version:subject:to:x-me-proxy:x-me-proxy :x-me-sender:x-me-sender:x-sasl-enc; s=fm3; bh=Eaqf+mQPb0CqgNn2L 8o/sO7Y2ipNcfWsZn6yLFoG/dc=; b=npunvrrrpVqGisHITrAbWtCK4GGr1G4GY 6tPhpPIyxjnSRp1N4DIQE5TfC3lxiBVcjX2otGkt6qnrYaNSNKsR9EZWPMWufP4Q GhHptBq/1R31Wcbx50DoKOEflRq1fydQ0EtBU8kabz20jLclg9SXOymVt5uJkbXt Ti9im6Exlj9qptjSWBJ/fCQoJFq03SGXmAlouTTRegiL5z+qSjYchwNv2TQGsN5F ACzekPuCOuBmhClpFiO4qt5NopI9gUIAN1I1WwRZHQB6p0mKAi2lMh7VbnCCsbSX yABqajnx+UBX6JBW2bj2QKv8uTr1TOB0di+CAM73wBIbHSJcz6VEA== X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedvtddruddvgdehjecutefuodetggdotefrodftvf curfhrohhfihhlvgemucfhrghsthforghilhdpqfgfvfdpuffrtefokffrpgfnqfghnecu uegrihhlohhuthemuceftddtnecunecujfgurhephffvufffkffoggfgsedtkeertdertd dtnecuhfhrohhmpeforghrthihnhgrshcurfhumhhpuhhtihhsuceomheslhgrmhgsuggr rdhltheqnecuggftrfgrthhtvghrnhepuefhfedvheelieduhedvveeiffdtleehieduue ehjeejtdekuddvtdffheeuleejnecuvehluhhsthgvrhfuihiivgeptdenucfrrghrrghm pehmrghilhhfrhhomhepmheslhgrmhgsuggrrdhlth X-ME-Proxy: Received: by mail.messagingengine.com (Postfix) with ESMTPA; Mon, 12 Jul 2021 08:55:00 -0400 (EDT) From: Martynas Pumputis To: bpf@vger.kernel.org Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, m@lambda.lt Subject: [PATCH v2 bpf-next] libbpf: fix reuse of pinned map on older kernel Date: Mon, 12 Jul 2021 14:55:51 +0200 Message-Id: <20210712125552.58705-1-m@lambda.lt> X-Mailer: git-send-email 2.32.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org When loading a BPF program with a pinned map, the loader checks whether the pinned map can be reused, i.e. their properties match. To derive such of the pinned map, the loader invokes BPF_OBJ_GET_INFO_BY_FD and then does the comparison. Unfortunately, on < 4.12 kernels the BPF_OBJ_GET_INFO_BY_FD is not available, so loading the program fails with the following error: libbpf: failed to get map info for map FD 5: Invalid argument libbpf: couldn't reuse pinned map at '/sys/fs/bpf/tc/globals/cilium_call_policy': parameter mismatch" libbpf: map 'cilium_call_policy': error reusing pinned map libbpf: map 'cilium_call_policy': failed to create: Invalid argument(-22) libbpf: failed to load object 'bpf_overlay.o' To fix this, fallback to derivation of the map properties via /proc/$PID/fdinfo/$MAP_FD if BPF_OBJ_GET_INFO_BY_FD fails with EINVAL, which can be used as an indicator that the kernel doesn't support the latter. Signed-off-by: Martynas Pumputis --- tools/lib/bpf/libbpf.c | 48 +++++++++++++++++++++++++++++++++++++++--- 1 file changed, 45 insertions(+), 3 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 1e04ce724240..a952acd6cd77 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -3894,6 +3894,42 @@ static int bpf_map_find_btf_info(struct bpf_object *obj, struct bpf_map *map) return 0; } +static int bpf_get_map_info_from_fdinfo(int fd, struct bpf_map_info *info) +{ + char file[PATH_MAX], buff[4096]; + FILE *fp; + __u32 val; + int err; + + snprintf(file, sizeof(file), "/proc/%d/fdinfo/%d", getpid(), fd); + memset(info, 0, sizeof(*info)); + + fp = fopen(file, "r"); + if (!fp) { + err = -errno; + pr_warn("failed to open %s: %d. No procfs support?\n", file, + err); + return err; + } + + while (fgets(buff, sizeof(buff), fp)) { + if (sscanf(buff, "map_type:\t%u", &val) == 1) + info->type = val; + else if (sscanf(buff, "key_size:\t%u", &val) == 1) + info->key_size = val; + else if (sscanf(buff, "value_size:\t%u", &val) == 1) + info->value_size = val; + else if (sscanf(buff, "max_entries:\t%u", &val) == 1) + info->max_entries = val; + else if (sscanf(buff, "map_flags:\t%i", &val) == 1) + info->map_flags = val; + } + + fclose(fp); + + return 0; +} + int bpf_map__reuse_fd(struct bpf_map *map, int fd) { struct bpf_map_info info = {}; @@ -3902,6 +3938,8 @@ int bpf_map__reuse_fd(struct bpf_map *map, int fd) char *new_name; err = bpf_obj_get_info_by_fd(fd, &info, &len); + if (err && errno == EINVAL) + err = bpf_get_map_info_from_fdinfo(fd, &info); if (err) return libbpf_err(err); @@ -4381,12 +4419,16 @@ static bool map_is_reuse_compat(const struct bpf_map *map, int map_fd) struct bpf_map_info map_info = {}; char msg[STRERR_BUFSIZE]; __u32 map_info_len; + int err; map_info_len = sizeof(map_info); - if (bpf_obj_get_info_by_fd(map_fd, &map_info, &map_info_len)) { - pr_warn("failed to get map info for map FD %d: %s\n", - map_fd, libbpf_strerror_r(errno, msg, sizeof(msg))); + err = bpf_obj_get_info_by_fd(map_fd, &map_info, &map_info_len); + if (err && errno == EINVAL) + err = bpf_get_map_info_from_fdinfo(map_fd, &map_info); + if (err) { + pr_warn("failed to get map info for map FD %d: %s\n", map_fd, + libbpf_strerror_r(errno, msg, sizeof(msg))); return false; } -- 2.32.0