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=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 7D912C433F5 for ; Thu, 9 Sep 2021 11:42:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 67B91611C4 for ; Thu, 9 Sep 2021 11:42:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236222AbhIILng (ORCPT ); Thu, 9 Sep 2021 07:43:36 -0400 Received: from mail.kernel.org ([198.145.29.99]:46060 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236756AbhIILmj (ORCPT ); Thu, 9 Sep 2021 07:42:39 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id ABC5E61186; Thu, 9 Sep 2021 11:41:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1631187689; bh=RUAMjOZ4iyzFD+zmCq7vbst6aJVhbYT3JHlhgRH50ik=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gUyBgAyNnXNwBxnPfLm2fH7n5hL+jNEaAiQ7euv1+FLUrVF7ccuWN0FkN0dUdOmbe cwdldzp/sj89uqrrcKsuWzgINDc+t4ibrNLbiCGkAtuf8GpFb9zur21OAmto39TqsT rdgpl9ML1SE19EVIpI+8DZgDChQhvJb6V7jAE69ljl1RCzDtusjvwB+GmgG1MDJTKf EAVGN5JSUYzxRSXCpNENEfN3SPKmUXOEiFyFiGf2iFOIU8DPMnp544vbDQn9DEhb2c /YjWUsoTJNRRsjR2igHFTU6ouW6bQysL4FeOIWqmIN4s2WeEQgJgj07re6urONlrA2 jWL8Y351vX9Xg== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Martynas Pumputis , Andrii Nakryiko , John Fastabend , Sasha Levin , netdev@vger.kernel.org, bpf@vger.kernel.org Subject: [PATCH AUTOSEL 5.14 017/252] libbpf: Fix reuse of pinned map on older kernel Date: Thu, 9 Sep 2021 07:37:11 -0400 Message-Id: <20210909114106.141462-17-sashal@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210909114106.141462-1-sashal@kernel.org> References: <20210909114106.141462-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Martynas Pumputis [ Upstream commit 97eb31384af943d6b97eb5947262cee4ef25cb87 ] 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 Signed-off-by: Andrii Nakryiko Acked-by: John Fastabend Link: https://lore.kernel.org/bpf/20210712125552.58705-1-m@lambda.lt Signed-off-by: Sasha Levin --- 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 6f5e2757bb3c..4a30a788d7c8 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; } -- 2.30.2