From patchwork Mon Feb 17 15:43:16 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Leon Hwang X-Patchwork-Id: 13978086 X-Patchwork-Delegate: bpf@iogearbox.net Received: from out-173.mta1.migadu.com (out-173.mta1.migadu.com [95.215.58.173]) (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 C2EAD224882 for ; Mon, 17 Feb 2025 15:44:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.173 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739807049; cv=none; b=BAuYkT5k/GsNqSXj3gKDmJ/kFY+aVrizZRRaC/o1Oszm1dL6O3rJlYgoMjb+XEXXuH6phTFicLbvIHdYY28eGjfR7Vyjd1Va+vnBsgRuA5ReaAcWR+E080ZO6J9OR/SLDBH71Ft4l6ZbJSprbtGlj4elWq3gQXCKpBH6qgFH9E0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739807049; c=relaxed/simple; bh=ntT/F2HrTU7R+7urokz7jPX2+BPKjPr76Lya51jX3uw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=XjiH8ac9TSX0ywvp7RwWHJVFzU7VryR2Mwvjf4xZ9/dkGlhbrOde4Sh7OK+6HTXb1W2bVmqXUDd1MHjnmxzXxGQpMSuqw8O7osNLsoAUzBVDfSsvD9fc24+6F4amfmEtv/P1oB8UBC8AuoF5m06+9mBRos73HqQraaqwxohI7cw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=Fm+yWrnS; arc=none smtp.client-ip=95.215.58.173 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="Fm+yWrnS" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1739807046; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=8vz1s9Yz6Ba603QOaXuD0IG8RUHaHGm3l2KxEpKWn9c=; b=Fm+yWrnSc62bIdyop7y5RBmXBEs5WKXHaFSXOKQI49wJP7bZWYicUT/zuAQXdiyE8Oo5Wn 9sRAtAm+Wj9RCRU9u6lSCtN9Z33TEbzJudZP6JCgt2C0o6S01v/gzv3MNpe+yrwwG/0xE+ 4WbyBiw6OJC0g1n89799ehhJgnbYjEQ= From: Leon Hwang To: bpf@vger.kernel.org Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, yonghong.song@linux.dev, song@kernel.org, eddyz87@gmail.com, me@manjusaka.me, leon.hwang@linux.dev, kernel-patches-bot@fb.com Subject: [PATCH bpf-next v3 2/4] bpf: Improve error reporting for freplace attachment failure Date: Mon, 17 Feb 2025 23:43:16 +0800 Message-ID: <20250217154318.76145-3-leon.hwang@linux.dev> In-Reply-To: <20250217154318.76145-1-leon.hwang@linux.dev> References: <20250217154318.76145-1-leon.hwang@linux.dev> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Migadu-Flow: FLOW_OUT X-Patchwork-Delegate: bpf@iogearbox.net When a freplace program fails to attach to a target, the error message lacks details, making debugging difficult. This patch enhances error reporting by providing a log that explains why the attachment failed. For example, if a freplace program tries to attach to a static function, the log now includes: libbpf: prog 'new_test_pkt_access': failed to attach to freplace: -EINVAL libbpf: prog 'new_test_pkt_access': attach log: subprog_tail() is not a global function Changes: * Added verifier log to capture the log of freplace attachment failure. * Updated bpf_tracing_prog_attach() to accept verifier log. * Extended struct bpf_attr with a user-supplied log buffer for tracing programs. This improves debugging by giving clear feedback when a freplace attachment fails. Signed-off-by: Leon Hwang --- include/uapi/linux/bpf.h | 2 ++ kernel/bpf/syscall.c | 51 +++++++++++++++++++++++++++++++++------- 2 files changed, 45 insertions(+), 8 deletions(-) diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index fff6cdb8d11a2..bea4d802d4463 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -1759,6 +1759,8 @@ union bpf_attr { * accessible through bpf_get_attach_cookie() BPF helper */ __u64 cookie; + __aligned_u64 log_buf; /* user supplied buffer */ + __u32 log_size; /* size of user buffer */ } tracing; struct { __u32 pf; diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index c420edbfb7c87..f41d1eea102a4 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -3412,7 +3412,8 @@ static const struct bpf_link_ops bpf_tracing_link_lops = { static int bpf_tracing_prog_attach(struct bpf_prog *prog, int tgt_prog_fd, u32 btf_id, - u64 bpf_cookie) + u64 bpf_cookie, + struct bpf_verifier_log *log) { struct bpf_link_primer link_primer; struct bpf_prog *tgt_prog = NULL; @@ -3537,7 +3538,7 @@ static int bpf_tracing_prog_attach(struct bpf_prog *prog, */ struct bpf_attach_target_info tgt_info = {}; - err = bpf_check_attach_target(NULL, prog, tgt_prog, btf_id, + err = bpf_check_attach_target(log, prog, tgt_prog, btf_id, &tgt_info); if (err) goto out_unlock; @@ -3949,7 +3950,7 @@ static int bpf_raw_tp_link_attach(struct bpf_prog *prog, tp_name = prog->aux->attach_func_name; break; } - return bpf_tracing_prog_attach(prog, 0, 0, 0); + return bpf_tracing_prog_attach(prog, 0, 0, 0, NULL); case BPF_PROG_TYPE_RAW_TRACEPOINT: case BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE: if (strncpy_from_user(buf, user_tp_name, sizeof(buf) - 1) < 0) @@ -5311,9 +5312,13 @@ static int bpf_map_do_batch(const union bpf_attr *attr, } #define BPF_LINK_CREATE_LAST_FIELD link_create.uprobe_multi.pid -static int link_create(union bpf_attr *attr, bpfptr_t uattr) +static int link_create(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size) { + struct bpf_verifier_log *log; + u32 log_true_size, log_size; struct bpf_prog *prog; + __aligned_u64 log_buf; + bool use_log; int ret; if (CHECK_ATTR(BPF_LINK_CREATE)) @@ -5326,10 +5331,33 @@ static int link_create(union bpf_attr *attr, bpfptr_t uattr) if (IS_ERR(prog)) return PTR_ERR(prog); + switch (prog->type) { + case BPF_PROG_TYPE_EXT: + log_buf = attr->link_create.tracing.log_buf; + log_size = attr->link_create.tracing.log_size; + use_log = true; + break; + default: + use_log = false; + } + + if (use_log) { + log = kvzalloc(sizeof(*log), GFP_KERNEL); + if (!log) { + ret = -ENOMEM; + goto out; + } + ret = bpf_vlog_init(log, BPF_LOG_FIXED, + (char __user *) (unsigned long) log_buf, + log_size); + if (ret) + goto out_free_log; + } + ret = bpf_prog_attach_check_attach_type(prog, attr->link_create.attach_type); if (ret) - goto out; + goto out_free_log; switch (prog->type) { case BPF_PROG_TYPE_CGROUP_SKB: @@ -5345,7 +5373,8 @@ static int link_create(union bpf_attr *attr, bpfptr_t uattr) ret = bpf_tracing_prog_attach(prog, attr->link_create.target_fd, attr->link_create.target_btf_id, - attr->link_create.tracing.cookie); + attr->link_create.tracing.cookie, + log); break; case BPF_PROG_TYPE_LSM: case BPF_PROG_TYPE_TRACING: @@ -5363,7 +5392,8 @@ static int link_create(union bpf_attr *attr, bpfptr_t uattr) ret = bpf_tracing_prog_attach(prog, attr->link_create.target_fd, attr->link_create.target_btf_id, - attr->link_create.tracing.cookie); + attr->link_create.tracing.cookie, + NULL); break; case BPF_PROG_TYPE_FLOW_DISSECTOR: case BPF_PROG_TYPE_SK_LOOKUP: @@ -5406,6 +5436,11 @@ static int link_create(union bpf_attr *attr, bpfptr_t uattr) ret = -EINVAL; } + if (ret < 0 && use_log) + (void) bpf_vlog_finalize(log, &log_true_size); +out_free_log: + if (use_log) + kvfree(log); out: if (ret < 0) bpf_prog_put(prog); @@ -5861,7 +5896,7 @@ static int __sys_bpf(enum bpf_cmd cmd, bpfptr_t uattr, unsigned int size) err = bpf_map_do_batch(&attr, uattr.user, BPF_MAP_DELETE_BATCH); break; case BPF_LINK_CREATE: - err = link_create(&attr, uattr); + err = link_create(&attr, uattr, size); break; case BPF_LINK_UPDATE: err = link_update(&attr);