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[2604:1380:45d1:ec00::1]) by mx.google.com with ESMTPS id gw13-20020a0562140f0d00b00683699d4df8si5891119qvb.139.2024.02.14.09.53.27 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 14 Feb 2024 09:53:27 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel+bounces-65719-ouuuleilei=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) client-ip=2604:1380:45d1:ec00::1; Authentication-Results: mx.google.com; dkim=pass header.i=@linux.microsoft.com header.s=default header.b=PxLYqSpw; arc=pass (i=1 spf=pass spfdomain=linux.microsoft.com dkim=pass dkdomain=linux.microsoft.com dmarc=pass fromdomain=linux.microsoft.com); spf=pass (google.com: domain of linux-kernel+bounces-65719-ouuuleilei=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) smtp.mailfrom="linux-kernel+bounces-65719-ouuuleilei=gmail.com@vger.kernel.org"; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=linux.microsoft.com Received: from smtp.subspace.kernel.org (wormhole.subspace.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ny.mirrors.kernel.org (Postfix) with ESMTPS id 2C9D71C2705C for ; Wed, 14 Feb 2024 17:52:08 +0000 (UTC) Received: from localhost.localdomain (localhost.localdomain [127.0.0.1]) by smtp.subspace.kernel.org (Postfix) with ESMTP id D96A6129A74; Wed, 14 Feb 2024 17:51:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b="PxLYqSpw" Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 84AD284FCB; Wed, 14 Feb 2024 17:50:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=13.77.154.182 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707933058; cv=none; b=swJiM2wC3pFuB7lttPvPINuDWqWN+KRZJlzBc2NUr8LwZ05jMi1OUpDRUALpV3zgFpYXbmr9AH+BOEgj42eWWOaa5DkA5Pgyu5R5cJABHA3LPP2PwfLoXksssY46cHOLpNnCpWqGH8j2m+ssNq1QaP8jPCqR2zILP1Bjt5cFDn0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707933058; c=relaxed/simple; bh=eh7Znbuws0FpzTqXB/htjVXzfh7M7J0jPIJS1UmMUDU=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=N9RTAKSYU0evUQNdaKxlVXp3NtU0L/KnOu42YnJ+atV4rA8z4lWOV4RZYRsvmJxo7139p0p+ieHKCzFq8h7aY1XFrR4CA20PfGsHuuwh66hO9a530iqwzwTBnqUvDuyjwoz7tW24MvjiDoMWLRyU8vm8m7GF0a6BQV5SznSOhSg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.microsoft.com; spf=pass smtp.mailfrom=linux.microsoft.com; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b=PxLYqSpw; arc=none smtp.client-ip=13.77.154.182 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.microsoft.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.microsoft.com Received: from localhost.localdomain (unknown [4.155.48.117]) by linux.microsoft.com (Postfix) with ESMTPSA id 2703D20B2002; Wed, 14 Feb 2024 09:50:56 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 2703D20B2002 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1707933056; bh=rCUIa9r7RCQbT2ME+ULhEAx0/ULy4rYNOneRGyRu2VM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=PxLYqSpw5JdpvlocHypm61AscLQdzr7hR8SkFvoeFd8lSUrYXe4sknikoPsSdw0jy yi5IDnjbtW6SfSme1niNXYr0rcpO0WnPnND3/wB0LlV9RH0dak8LulychTMBc1vjS4 JNvmi6/SRZsaC431v2DaPocDKPH2XMxJtsHeE/Sg= From: Beau Belgrave To: rostedt@goodmis.org, mhiramat@kernel.org Cc: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, mathieu.desnoyers@efficios.com Subject: [PATCH v3 2/4] tracing/user_events: Introduce multi-format events Date: Wed, 14 Feb 2024 17:50:44 +0000 Message-Id: <20240214175046.240-3-beaub@linux.microsoft.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240214175046.240-1-beaub@linux.microsoft.com> References: <20240214175046.240-1-beaub@linux.microsoft.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1790897771248595227 X-GMAIL-MSGID: 1790897771248595227 Currently user_events supports 1 event with the same name and must have the exact same format when referenced by multiple programs. This opens an opportunity for malicous or poorly thought through programs to create events that others use with different formats. Another scenario is user programs wishing to use the same event name but add more fields later when the software updates. Various versions of a program may be running side-by-side, which is prevented by the current single format requirement. Add a new register flag (USER_EVENT_REG_MULTI_FORMAT) which indicates the user program wishes to use the same user_event name, but may have several different formats of the event in the future. When this flag is used, create the underlying tracepoint backing the user_event with a unique name per-version of the format. It's important that existing ABI users do not get this logic automatically, even if one of the multi format events matches the format. This ensures existing programs that create events and assume the tracepoint name will match exactly continue to work as expected. Add logic to only check multi-format events with other multi-format events and single-format events to only check single-format events during find. Change system name of the multi-format event tracepoint to ensure that multi-format events are isolated completely from single-format events. This prevents single-format names from conflicting with multi-format events if they end with the same suffix as the multi-format events. Add a register_name (reg_name) to the user_event struct which allows for split naming of events. We now have the name that was used to register within user_events as well as the unique name for the tracepoint. Upon registering events ensure matches based on first the reg_name, followed by the fields and format of the event. This allows for multiple events with the same registered name to have different formats. The underlying tracepoint will have a unique name in the format of {reg_name}.{unique_id}. For example, if both "test u32 value" and "test u64 value" are used with the USER_EVENT_REG_MULTI_FORMAT the system would have 2 unique tracepoints. The dynamic_events file would then show the following: u:test u64 count u:test u32 count The actual tracepoint names look like this: test.0 test.1 Both would be under the new user_events_multi system name to prevent the older ABI from being used to squat on multi-formatted events and block their use. Deleting events via "!u:test u64 count" would only delete the first tracepoint that matched that format. When the delete ABI is used all events with the same name will be attempted to be deleted. If per-version deletion is required, user programs should either not use persistent events or delete them via dynamic_events. Signed-off-by: Beau Belgrave --- include/uapi/linux/user_events.h | 6 +- kernel/trace/trace_events_user.c | 118 +++++++++++++++++++++++++++---- 2 files changed, 111 insertions(+), 13 deletions(-) diff --git a/include/uapi/linux/user_events.h b/include/uapi/linux/user_events.h index f74f3aedd49c..a03de03dccbc 100644 --- a/include/uapi/linux/user_events.h +++ b/include/uapi/linux/user_events.h @@ -12,6 +12,7 @@ #include #define USER_EVENTS_SYSTEM "user_events" +#define USER_EVENTS_MULTI_SYSTEM "user_events_multi" #define USER_EVENTS_PREFIX "u:" /* Create dynamic location entry within a 32-bit value */ @@ -22,8 +23,11 @@ enum user_reg_flag { /* Event will not delete upon last reference closing */ USER_EVENT_REG_PERSIST = 1U << 0, + /* Event will be allowed to have multiple formats */ + USER_EVENT_REG_MULTI_FORMAT = 1U << 1, + /* This value or above is currently non-ABI */ - USER_EVENT_REG_MAX = 1U << 1, + USER_EVENT_REG_MAX = 1U << 2, }; /* diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c index dda58681247e..53980982a575 100644 --- a/kernel/trace/trace_events_user.c +++ b/kernel/trace/trace_events_user.c @@ -34,7 +34,8 @@ /* Limit how long of an event name plus args within the subsystem. */ #define MAX_EVENT_DESC 512 -#define EVENT_NAME(user_event) ((user_event)->tracepoint.name) +#define EVENT_NAME(user_event) ((user_event)->reg_name) +#define EVENT_TP_NAME(user_event) ((user_event)->tracepoint.name) #define MAX_FIELD_ARRAY_SIZE 1024 /* @@ -54,10 +55,13 @@ * allows isolation for events by various means. */ struct user_event_group { - char *system_name; - struct hlist_node node; - struct mutex reg_mutex; + char *system_name; + char *system_multi_name; + struct hlist_node node; + struct mutex reg_mutex; DECLARE_HASHTABLE(register_table, 8); + /* ID that moves forward within the group for multi-event names */ + u64 multi_id; }; /* Group for init_user_ns mapping, top-most group */ @@ -78,6 +82,7 @@ static unsigned int current_user_events; */ struct user_event { struct user_event_group *group; + char *reg_name; struct tracepoint tracepoint; struct trace_event_call call; struct trace_event_class class; @@ -127,6 +132,8 @@ struct user_event_enabler { #define ENABLE_BIT(e) ((int)((e)->values & ENABLE_VAL_BIT_MASK)) +#define EVENT_MULTI_FORMAT(f) ((f) & USER_EVENT_REG_MULTI_FORMAT) + /* Used for asynchronous faulting in of pages */ struct user_event_enabler_fault { struct work_struct work; @@ -330,6 +337,7 @@ static void user_event_put(struct user_event *user, bool locked) static void user_event_group_destroy(struct user_event_group *group) { kfree(group->system_name); + kfree(group->system_multi_name); kfree(group); } @@ -348,6 +356,21 @@ static char *user_event_group_system_name(void) return system_name; } +static char *user_event_group_system_multi_name(void) +{ + char *system_name; + int len = sizeof(USER_EVENTS_MULTI_SYSTEM) + 1; + + system_name = kmalloc(len, GFP_KERNEL); + + if (!system_name) + return NULL; + + snprintf(system_name, len, "%s", USER_EVENTS_MULTI_SYSTEM); + + return system_name; +} + static struct user_event_group *current_user_event_group(void) { return init_group; @@ -367,6 +390,11 @@ static struct user_event_group *user_event_group_create(void) if (!group->system_name) goto error; + group->system_multi_name = user_event_group_system_multi_name(); + + if (!group->system_multi_name) + goto error; + mutex_init(&group->reg_mutex); hash_init(group->register_table); @@ -1482,6 +1510,11 @@ static int destroy_user_event(struct user_event *user) hash_del(&user->node); user_event_destroy_validators(user); + + /* If we have different names, both must be freed */ + if (EVENT_NAME(user) != EVENT_TP_NAME(user)) + kfree(EVENT_TP_NAME(user)); + kfree(user->call.print_fmt); kfree(EVENT_NAME(user)); kfree(user); @@ -1504,12 +1537,24 @@ static struct user_event *find_user_event(struct user_event_group *group, *outkey = key; hash_for_each_possible(group->register_table, user, node, key) { + /* + * Single-format events shouldn't return multi-format + * events. Callers expect the underlying tracepoint to match + * the name exactly in these cases. Only check like-formats. + */ + if (EVENT_MULTI_FORMAT(flags) != EVENT_MULTI_FORMAT(user->reg_flags)) + continue; + if (strcmp(EVENT_NAME(user), name)) continue; if (user_fields_match(user, argc, argv)) return user_event_get(user); + /* Scan others if this is a multi-format event */ + if (EVENT_MULTI_FORMAT(flags)) + continue; + return ERR_PTR(-EADDRINUSE); } @@ -1889,8 +1934,12 @@ static bool user_event_match(const char *system, const char *event, struct user_event *user = container_of(ev, struct user_event, devent); bool match; - match = strcmp(EVENT_NAME(user), event) == 0 && - (!system || strcmp(system, USER_EVENTS_SYSTEM) == 0); + match = strcmp(EVENT_NAME(user), event) == 0; + + if (match && system) { + match = strcmp(system, user->group->system_name) == 0 || + strcmp(system, user->group->system_multi_name) == 0; + } if (match) match = user_fields_match(user, argc, argv); @@ -1923,6 +1972,39 @@ static int user_event_trace_register(struct user_event *user) return ret; } +static int user_event_set_tp_name(struct user_event *user) +{ + lockdep_assert_held(&user->group->reg_mutex); + + if (EVENT_MULTI_FORMAT(user->reg_flags)) { + char *multi_name; + int len; + + len = snprintf(NULL, 0, "%s.%llx", user->reg_name, + user->group->multi_id) + 1; + + multi_name = kzalloc(len, GFP_KERNEL_ACCOUNT); + + if (!multi_name) + return -ENOMEM; + + snprintf(multi_name, len, "%s.%llx", user->reg_name, + user->group->multi_id); + + user->call.name = multi_name; + user->tracepoint.name = multi_name; + + /* Inc to ensure unique multi-event name next time */ + user->group->multi_id++; + } else { + /* Non Multi-format uses register name */ + user->call.name = user->reg_name; + user->tracepoint.name = user->reg_name; + } + + return 0; +} + /* * Parses the event name, arguments and flags then registers if successful. * The name buffer lifetime is owned by this method for success cases only. @@ -1985,7 +2067,13 @@ static int user_event_parse(struct user_event_group *group, char *name, INIT_LIST_HEAD(&user->validators); user->group = group; - user->tracepoint.name = name; + user->reg_name = name; + user->reg_flags = reg_flags; + + ret = user_event_set_tp_name(user); + + if (ret) + goto put_user; ret = user_event_parse_fields(user, args); @@ -1999,11 +2087,14 @@ static int user_event_parse(struct user_event_group *group, char *name, user->call.data = user; user->call.class = &user->class; - user->call.name = name; user->call.flags = TRACE_EVENT_FL_TRACEPOINT; user->call.tp = &user->tracepoint; user->call.event.funcs = &user_event_funcs; - user->class.system = group->system_name; + + if (EVENT_MULTI_FORMAT(user->reg_flags)) + user->class.system = group->system_multi_name; + else + user->class.system = group->system_name; user->class.fields_array = user_event_fields_array; user->class.get_fields = user_event_get_fields; @@ -2025,8 +2116,6 @@ static int user_event_parse(struct user_event_group *group, char *name, if (ret) goto put_user_lock; - user->reg_flags = reg_flags; - if (user->reg_flags & USER_EVENT_REG_PERSIST) { /* Ensure we track self ref and caller ref (2) */ refcount_set(&user->refcnt, 2); @@ -2050,6 +2139,11 @@ static int user_event_parse(struct user_event_group *group, char *name, user_event_destroy_fields(user); user_event_destroy_validators(user); kfree(user->call.print_fmt); + + /* Caller frees reg_name on error, but not multi-name */ + if (EVENT_NAME(user) != EVENT_TP_NAME(user)) + kfree(EVENT_TP_NAME(user)); + kfree(user); return ret; } @@ -2641,7 +2735,7 @@ static int user_seq_show(struct seq_file *m, void *p) hash_for_each(group->register_table, i, user, node) { status = user->status; - seq_printf(m, "%s", EVENT_NAME(user)); + seq_printf(m, "%s", EVENT_TP_NAME(user)); if (status != 0) seq_puts(m, " #");