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Peter Anvin" , Andy Lutomirski , Peter Zijlstra , "Rob Herring" , Steven Rostedt , "Andrew Morton" , Mark Rutland , "Tom Lendacky" , Ashish Kalra , James Gowans , Stanislav Kinsburskii , , , , Anthony Yznaga , Usama Arif , David Woodhouse , Benjamin Herrenschmidt Subject: [PATCH v2 15/17] tracing: Recover trace events from kexec handover Date: Fri, 22 Dec 2023 19:51:42 +0000 Message-ID: <20231222195144.24532-10-graf@amazon.com> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20231222195144.24532-1-graf@amazon.com> References: <20231222193607.15474-1-graf@amazon.com> <20231222195144.24532-1-graf@amazon.com> MIME-Version: 1.0 X-Originating-IP: [10.253.83.51] X-ClientProxiedBy: EX19D035UWB003.ant.amazon.com (10.13.138.85) To EX19D020UWC004.ant.amazon.com (10.13.138.149) X-Rspamd-Queue-Id: 467018001A X-Rspam-User: X-Stat-Signature: op4j4csaryh1ukhpxz9e7c37oqi8x5rt X-Rspamd-Server: rspam01 X-HE-Tag: 1703274823-451175 X-HE-Meta: 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 oZU68+00 4qQk5eX0/Z0T/shWdy1hwy9byV4UL0s03H2ZW9sSXCdE9B466nYbZrStLaTkb1cATP+V3uD5LTQludGDDCAUUbijcaPPbYDT8jClqOB8StRe19uCqbXNgxqWh8SFpS8mqmrNfJoBW5csJQNhyu+KhQp4WWKiu4IFSkumVb8CxvtjTTN8k2Kxs/GjVM2DzipGbMwbYy706l6+Ig6HigjrVEdE5PlHzBZxn4AzDQSccFCDj52PfyvbVYxlDyoTVbQ6zflM0vOHo3k/zroPj1F1RXelkR6ChSbFCQ4TP X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: This patch implements all logic necessary to match a new trace event that we add against preserved trace events from kho. If we find a match, we give the new trace event the old event's identifier. That way, trace read-outs are able to make sense of buffer contents again because the parsing code for events looks at the same identifiers. Signed-off-by: Alexander Graf --- v1 -> v2: - make kho_get_fdt() const - Get events as array from a property, use fingerprint instead of names to identify events - Remove ifdefs --- kernel/trace/trace_output.c | 158 +++++++++++++++++++++++++++++++++++- 1 file changed, 156 insertions(+), 2 deletions(-) diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c index 7d8815352e20..937002a204e1 100644 --- a/kernel/trace/trace_output.c +++ b/kernel/trace/trace_output.c @@ -24,6 +24,8 @@ DECLARE_RWSEM(trace_event_sem); static struct hlist_head event_hash[EVENT_HASHSIZE] __read_mostly; +static bool trace_is_kho_event(int type); + enum print_line_t trace_print_bputs_msg_only(struct trace_iterator *iter) { struct trace_seq *s = &iter->seq; @@ -784,7 +786,7 @@ static DEFINE_IDA(trace_event_ida); static void free_trace_event_type(int type) { - if (type >= __TRACE_LAST_TYPE) + if (type >= __TRACE_LAST_TYPE && !trace_is_kho_event(type)) ida_free(&trace_event_ida, type); } @@ -810,6 +812,156 @@ void trace_event_read_unlock(void) up_read(&trace_event_sem); } + +/** + * trace_kho_get_map - Return the KHO event map + * @pmap: Pointer to a trace map array. Will be filled on success. + * @plen: Pointer to the length of the map. Will be filled on success. + * @unallocated: True if the event does not have an ID yet + * + * Event types are semi-dynamically generated. To ensure that + * their identifiers match before and after kexec with KHO, + * we store an event map in the KHO DT. Whenever we need the + * map, this function provides it. + * + * The first time we request a map, it also walks through it and + * reserves all identifiers so later event registration has find their + * identifier already reserved. + */ +static int trace_kho_get_map(const struct trace_event_map **pmap, int *plen, + bool unallocated) +{ + static const struct trace_event_map *event_map; + static int event_map_len; + static bool event_map_reserved; + const struct trace_event_map *map = NULL; + const void *fdt = kho_get_fdt(); + const char *path = "/ftrace"; + int off, err, len = 0; + int i; + + if (!IS_ENABLED(CONFIG_FTRACE_KHO) || !fdt) + return -EINVAL; + + if (event_map) { + map = event_map; + len = event_map_len; + } + + if (!map) { + off = fdt_path_offset(fdt, path); + + if (off < 0) { + pr_debug("Could not find '%s' in DT", path); + return -EINVAL; + } + + err = fdt_node_check_compatible(fdt, off, "ftrace-v1"); + if (err) { + pr_warn("Node '%s' has invalid compatible", path); + return -EINVAL; + } + + map = fdt_getprop(fdt, off, "events", &len); + if (!map) + return -EINVAL; + + event_map = map; + event_map_len = len; + } + + if (unallocated && !event_map_reserved) { + /* + * Reserve all IDs in our IDA. We only have a working IDA later + * in boot, so restrict it to when we allocate a dynamic type id + * for an event. + */ + for (i = 0; i < len; i += sizeof(*map)) { + const struct trace_event_map *imap = (void *)map + i; + + if (imap->type < __TRACE_LAST_TYPE) + continue; + if (ida_alloc_range(&trace_event_ida, imap->type, imap->type, + GFP_KERNEL) != imap->type) { + pr_warn("Unable to reserve id %d", imap->type); + return -EINVAL; + } + } + + event_map_reserved = true; + } + + *pmap = map; + *plen = len; + + return 0; +} + +/** + * trace_is_kho_event - returns true if the event type is KHO reserved + * @event: the event type to enumerate + * + * With KHO, we reserve all previous kernel's trace event types in the + * KHO DT. Then, when we allocate a type, we just reuse the previous + * kernel's value. However, that means we have to keep these type identifiers + * reserved across the lifetime of the system, because we may get a new event + * that matches the old kernel's event fingerprint. This function is a small + * helper that allows us to check whether a type ID is in use by KHO. + */ +static bool trace_is_kho_event(int type) +{ + const struct trace_event_map *map = NULL; + int len, i; + + if (trace_kho_get_map(&map, &len, false)) + return false; + + if (!map) + return false; + + for (i = 0; i < len; i += sizeof(*map), map++) + if (map->type == type) + return true; + + return false; +} + +/** + * trace_kho_fill_event_type - restore event type info from KHO + * @event: the event to enumerate + * + * Event types are semi-dynamically generated. To ensure that + * their identifiers match before and after kexec with KHO, + * let's match up unique fingerprint - either their predetermined + * type or their crc32 value - and fill in the respective type + * information if we booted with KHO. + */ +static bool trace_kho_fill_event_type(struct trace_event *event) +{ + const struct trace_event_map *map = NULL; + int len = 0, i; + u32 crc32; + + if (trace_kho_get_map(&map, &len, !event->type)) + return false; + + crc32 = event2fp(event); + + for (i = 0; i < len; i += sizeof(*map), map++) { + if (map->crc32 == crc32) { + if (!map->type) + return false; + + event->type = map->type; + return true; + } + } + + pr_debug("Could not find event"); + + return false; +} + /** * register_trace_event - register output for an event type * @event: the event type to register @@ -838,7 +990,9 @@ int register_trace_event(struct trace_event *event) if (WARN_ON(!event->funcs)) goto out; - if (!event->type) { + if (trace_kho_fill_event_type(event)) { + pr_debug("Recovered id=%d", event->type); + } else if (!event->type) { event->type = alloc_trace_event_type(); if (!event->type) goto out;