Rename "userdata" to "extradata" since this structure will hold both user and system data in future patches. Keep "userdata" term only for data that comes from userspace (configfs), while "extradata" encompasses both userdata and future kerneldata.

These are the rules of the design

1. extradata_complete will hold userdata and sysdata (coming) 2. sysdata will come after userdata_length 3. extradata_complete[userdata_length] string will be replaced at every message 5. userdata is replaced when configfs changes (update_userdata()) 6. sysdata is replaced at every message

Example: extradata_complete = "userkey=uservalue cpu=42" userdata_length = 17 sysdata_length = 7 (space (" ") is part of sysdata)

Since sysdata is still not available, you will see the following in the send functions:

extradata_len = nt->userdata_length;

The upcoming patches will, which will add support for sysdata, will change it to:

extradata_len = nt->userdata_length + sysdata_len;

Signed-off-by: Breno Leitao leitao@debian.org Reviewed-by: Simon Horman horms@kernel.org --- drivers/net/netconsole.c | 87 ++++++++++++++++++++++++------------------------ 1 file changed, 44 insertions(+), 43 deletions(-)

diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c index 034caaa26563504357f859000678af2037003c25..7f05c7f74c31ce26a7329c784bd99305b7bea0e8 100644 --- a/drivers/net/netconsole.c +++ b/drivers/net/netconsole.c @@ -45,12 +45,12 @@ MODULE_DESCRIPTION("Console driver for network interfaces"); MODULE_LICENSE("GPL");

#define MAX_PARAM_LENGTH 256 -#define MAX_USERDATA_ENTRY_LENGTH 256 -#define MAX_USERDATA_VALUE_LENGTH 200 +#define MAX_EXTRADATA_ENTRY_LEN 256 +#define MAX_EXTRADATA_VALUE_LEN 200 /* The number 3 comes from userdata entry format characters (' ', '=', '\n') */ -#define MAX_USERDATA_NAME_LENGTH (MAX_USERDATA_ENTRY_LENGTH - \ - MAX_USERDATA_VALUE_LENGTH - 3) -#define MAX_USERDATA_ITEMS 16 +#define MAX_EXTRADATA_NAME_LEN (MAX_EXTRADATA_ENTRY_LEN - \ + MAX_EXTRADATA_VALUE_LEN - 3) +#define MAX_EXTRADATA_ITEMS 16 #define MAX_PRINT_CHUNK 1000

static char config[MAX_PARAM_LENGTH]; @@ -102,8 +102,8 @@ struct netconsole_target_stats { * @list: Links this target into the target_list. * @group: Links us into the configfs subsystem hierarchy. * @userdata_group: Links to the userdata configfs hierarchy - * @userdata_complete: Cached, formatted string of append - * @userdata_length: String length of userdata_complete + * @extradata_complete: Cached, formatted string of append + * @userdata_length: String length of usedata in extradata_complete. * @stats: Packet send stats for the target. Used for debugging. * @enabled: On / off knob to enable / disable target. * Visible from userspace (read-write). @@ -130,7 +130,7 @@ struct netconsole_target { #ifdef CONFIG_NETCONSOLE_DYNAMIC struct config_group group; struct config_group userdata_group; - char userdata_complete[MAX_USERDATA_ENTRY_LENGTH * MAX_USERDATA_ITEMS]; + char extradata_complete[MAX_EXTRADATA_ENTRY_LEN * MAX_EXTRADATA_ITEMS]; size_t userdata_length; #endif struct netconsole_target_stats stats; @@ -690,7 +690,7 @@ static ssize_t remote_mac_store(struct config_item *item, const char *buf,

struct userdatum { struct config_item item; - char value[MAX_USERDATA_VALUE_LENGTH]; + char value[MAX_EXTRADATA_VALUE_LEN]; };

static struct userdatum *to_userdatum(struct config_item *item) @@ -727,13 +727,13 @@ static void update_userdata(struct netconsole_target *nt)

/* Clear the current string in case the last userdatum was deleted */ nt->userdata_length = 0; - nt->userdata_complete[0] = 0; + nt->extradata_complete[0] = 0;

list_for_each(entry, &nt->userdata_group.cg_children) { struct userdatum *udm_item; struct config_item *item;

- if (WARN_ON_ONCE(child_count >= MAX_USERDATA_ITEMS)) + if (WARN_ON_ONCE(child_count >= MAX_EXTRADATA_ITEMS)) break; child_count++;

@@ -741,19 +741,19 @@ static void update_userdata(struct netconsole_target *nt) udm_item = to_userdatum(item);

/* Skip userdata with no value set */ - if (strnlen(udm_item->value, MAX_USERDATA_VALUE_LENGTH) == 0) + if (strnlen(udm_item->value, MAX_EXTRADATA_VALUE_LEN) == 0) continue;

- /* This doesn't overflow userdata_complete since it will write - * one entry length (1/MAX_USERDATA_ITEMS long), entry count is + /* This doesn't overflow extradata_complete since it will write + * one entry length (1/MAX_EXTRADATA_ITEMS long), entry count is * checked to not exceed MAX items with child_count above */ - complete_idx += scnprintf(&nt->userdata_complete[complete_idx], - MAX_USERDATA_ENTRY_LENGTH, " %s=%s\n", + complete_idx += scnprintf(&nt->extradata_complete[complete_idx], + MAX_EXTRADATA_ENTRY_LEN, " %s=%s\n", item->ci_name, udm_item->value); } - nt->userdata_length = strnlen(nt->userdata_complete, - sizeof(nt->userdata_complete)); + nt->userdata_length = strnlen(nt->extradata_complete, + sizeof(nt->extradata_complete)); }

static ssize_t userdatum_value_store(struct config_item *item, const char *buf, @@ -764,7 +764,7 @@ static ssize_t userdatum_value_store(struct config_item *item, const char *buf, struct userdata *ud; ssize_t ret;

- if (count > MAX_USERDATA_VALUE_LENGTH) + if (count > MAX_EXTRADATA_VALUE_LEN) return -EMSGSIZE;

mutex_lock(&dynamic_netconsole_mutex); @@ -813,13 +813,13 @@ static struct config_item *userdatum_make_item(struct config_group *group, struct userdata *ud; size_t child_count;

- if (strlen(name) > MAX_USERDATA_NAME_LENGTH) + if (strlen(name) > MAX_EXTRADATA_NAME_LEN) return ERR_PTR(-ENAMETOOLONG);

ud = to_userdata(&group->cg_item); nt = userdata_to_target(ud); child_count = list_count_nodes(&nt->userdata_group.cg_children); - if (child_count >= MAX_USERDATA_ITEMS) + if (child_count >= MAX_EXTRADATA_ITEMS) return ERR_PTR(-ENOSPC);

udm = kzalloc(sizeof(*udm), GFP_KERNEL); @@ -1120,11 +1120,11 @@ static void send_msg_no_fragmentation(struct netconsole_target *nt, int msg_len, int release_len) { - const char *userdata = NULL; + const char *extradata = NULL; const char *release;

#ifdef CONFIG_NETCONSOLE_DYNAMIC - userdata = nt->userdata_complete; + extradata = nt->extradata_complete; #endif

if (release_len) { @@ -1136,10 +1136,10 @@ static void send_msg_no_fragmentation(struct netconsole_target *nt, memcpy(nt->buf, msg, msg_len); }

- if (userdata) + if (extradata) msg_len += scnprintf(&nt->buf[msg_len], MAX_PRINT_CHUNK - msg_len, - "%s", userdata); + "%s", extradata);

send_udp(nt, nt->buf, msg_len); } @@ -1156,24 +1156,25 @@ static void send_fragmented_body(struct netconsole_target *nt, const char *msgbody, int header_len, int msgbody_len) { - const char *userdata = NULL; + int sent_extradata, preceding_bytes; + const char *extradata = NULL; int body_len, offset = 0; - int userdata_len = 0; + int extradata_len = 0;

#ifdef CONFIG_NETCONSOLE_DYNAMIC - userdata = nt->userdata_complete; - userdata_len = nt->userdata_length; + extradata = nt->extradata_complete; + extradata_len = nt->userdata_length; #endif

/* body_len represents the number of bytes that will be sent. This is * bigger than MAX_PRINT_CHUNK, thus, it will be split in multiple * packets */ - body_len = msgbody_len + userdata_len; + body_len = msgbody_len + extradata_len;

/* In each iteration of the while loop below, we send a packet * containing the header and a portion of the body. The body is - * composed of two parts: msgbody and userdata. We keep track of how + * composed of two parts: msgbody and extradata. We keep track of how * many bytes have been sent so far using the offset variable, which * ranges from 0 to the total length of the body. */ @@ -1201,36 +1202,36 @@ static void send_fragmented_body(struct netconsole_target *nt,

/* msgbody was finally written, either in the previous * messages and/or in the current buf. Time to write - * the userdata. + * the extradata. */ msgbody_written |= offset + this_offset >= msgbody_len;

- /* Msg body is fully written and there is pending userdata to - * write, append userdata in this chunk + /* Msg body is fully written and there is pending extradata to + * write, append extradata in this chunk */ if (msgbody_written && offset + this_offset < body_len) { /* Track how much user data was already sent. First * time here, sent_userdata is zero */ - int sent_userdata = (offset + this_offset) - msgbody_len; + sent_extradata = (offset + this_offset) - msgbody_len; /* offset of bytes used in current buf */ - int preceding_bytes = this_chunk + this_header; + preceding_bytes = this_chunk + this_header;

- if (WARN_ON_ONCE(sent_userdata < 0)) + if (WARN_ON_ONCE(sent_extradata < 0)) return;

- this_chunk = min(userdata_len - sent_userdata, + this_chunk = min(extradata_len - sent_extradata, MAX_PRINT_CHUNK - preceding_bytes); if (WARN_ON_ONCE(this_chunk < 0)) /* this_chunk could be zero if all the previous * message used all the buffer. This is not a - * problem, userdata will be sent in the next + * problem, extradata will be sent in the next * iteration */ return;

memcpy(nt->buf + this_header + this_offset, - userdata + sent_userdata, + extradata + sent_extradata, this_chunk); this_offset += this_chunk; } @@ -1287,17 +1288,17 @@ static void send_msg_fragmented(struct netconsole_target *nt, static void send_ext_msg_udp(struct netconsole_target *nt, const char *msg, int msg_len) { - int userdata_len = 0; + int extradata_len = 0; int release_len = 0;

#ifdef CONFIG_NETCONSOLE_DYNAMIC - userdata_len = nt->userdata_length; + extradata_len = nt->userdata_length; #endif

if (nt->release) release_len = strlen(init_utsname()->release) + 1;

- if (msg_len + release_len + userdata_len <= MAX_PRINT_CHUNK) + if (msg_len + release_len + extradata_len <= MAX_PRINT_CHUNK) return send_msg_no_fragmentation(nt, msg, msg_len, release_len);

return send_msg_fragmented(nt, msg, msg_len, release_len);

This patch introduces a bitfield to store sysdata features in the netconsole_target struct. It also adds configfs helpers to enable or disable the CPU_NR feature, which populates the CPU number in sysdata.

The patch provides the necessary infrastructure to set or unset the CPU_NR feature, but does not modify the message itself.

Signed-off-by: Breno Leitao leitao@debian.org Reviewed-by: Simon Horman horms@kernel.org --- drivers/net/netconsole.c | 81 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 81 insertions(+)

diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c index 15daaba65c8827bf399f0623cc42d310626cbf68..710330ae8ee462083dbb4aa889cb0ba0cb5a7475 100644 --- a/drivers/net/netconsole.c +++ b/drivers/net/netconsole.c @@ -97,6 +97,15 @@ struct netconsole_target_stats { struct u64_stats_sync syncp; };

+/* Features enabled in sysdata. Contrary to userdata, this data is populated by + * the kernel. The fields are designed as bitwise flags, allowing multiple + * features to be set in sysdata_fields. + */ +enum sysdata_feature { + /* Populate the CPU that sends the message */ + CPU_NR = BIT(0), +}; + /** * struct netconsole_target - Represents a configured netconsole target. * @list: Links this target into the target_list. @@ -104,6 +113,7 @@ struct netconsole_target_stats { * @userdata_group: Links to the userdata configfs hierarchy * @extradata_complete: Cached, formatted string of append * @userdata_length: String length of usedata in extradata_complete. + * @sysdata_fields: Sysdata features enabled. * @stats: Packet send stats for the target. Used for debugging. * @enabled: On / off knob to enable / disable target. * Visible from userspace (read-write). @@ -132,6 +142,8 @@ struct netconsole_target { struct config_group userdata_group; char extradata_complete[MAX_EXTRADATA_ENTRY_LEN * MAX_EXTRADATA_ITEMS]; size_t userdata_length; + /* bit-wise with sysdata_feature bits */ + u32 sysdata_fields; #endif struct netconsole_target_stats stats; bool enabled; @@ -399,6 +411,19 @@ static ssize_t transmit_errors_show(struct config_item *item, char *buf) return sysfs_emit(buf, "%llu\n", xmit_drop_count + enomem_count); }

+/* configfs helper to display if cpu_nr sysdata feature is enabled */ +static ssize_t sysdata_cpu_nr_enabled_show(struct config_item *item, char *buf) +{ + struct netconsole_target *nt = to_target(item->ci_parent); + bool cpu_nr_enabled; + + mutex_lock(&dynamic_netconsole_mutex); + cpu_nr_enabled = !!(nt->sysdata_fields & CPU_NR); + mutex_unlock(&dynamic_netconsole_mutex); + + return sysfs_emit(buf, "%d\n", cpu_nr_enabled); +} + /* * This one is special -- targets created through the configfs interface * are not enabled (and the corresponding netpoll activated) by default. @@ -793,7 +818,62 @@ static ssize_t userdatum_value_store(struct config_item *item, const char *buf, return ret; }

+/* disable_sysdata_feature - Disable sysdata feature and clean sysdata + * @nt: target that is disabling the feature + * @feature: feature being disabled + */ +static void disable_sysdata_feature(struct netconsole_target *nt, + enum sysdata_feature feature) +{ + nt->sysdata_fields &= ~feature; + nt->extradata_complete[nt->userdata_length] = 0; +} + +/* configfs helper to sysdata cpu_nr feature */ +static ssize_t sysdata_cpu_nr_enabled_store(struct config_item *item, + const char *buf, size_t count) +{ + struct netconsole_target *nt = to_target(item->ci_parent); + bool cpu_nr_enabled, curr; + ssize_t ret; + + ret = kstrtobool(buf, &cpu_nr_enabled); + if (ret) + return ret; + + mutex_lock(&dynamic_netconsole_mutex); + curr = nt->sysdata_fields & CPU_NR; + if (cpu_nr_enabled == curr) + /* no change requested */ + goto unlock_ok; + + if (cpu_nr_enabled && + count_extradata_entries(nt) >= MAX_EXTRADATA_ITEMS) { + /* user wants the new feature, but there is no space in the + * buffer. + */ + ret = -ENOSPC; + goto unlock; + } + + if (cpu_nr_enabled) + nt->sysdata_fields |= CPU_NR; + else + /* This is special because extradata_complete might have + * remaining data from previous sysdata, and it needs to be + * cleaned. + */ + disable_sysdata_feature(nt, CPU_NR); + +unlock_ok: + ret = strnlen(buf, count); +unlock: + mutex_unlock(&dynamic_netconsole_mutex); + return ret; +} + CONFIGFS_ATTR(userdatum_, value); +CONFIGFS_ATTR(sysdata_, cpu_nr_enabled);

static struct configfs_attribute *userdatum_attrs[] = { &userdatum_attr_value, @@ -853,6 +933,7 @@ static void userdatum_drop(struct config_group *group, struct config_item *item) }

static struct configfs_attribute *userdata_attrs[] = { + &sysdata_attr_cpu_nr_enabled, NULL, };

Add infrastructure to automatically append kernel-generated data (sysdata) to netconsole messages. As the first use case, implement CPU number population, which adds the CPU that sent the message.

This change introduces three distinct data types: - extradata: The complete set of appended data (sysdata + userdata) - userdata: User-provided key-value pairs from userspace - sysdata: Kernel-populated data (e.g. cpu=XX)

The implementation adds a new configfs attribute 'cpu_nr' to control CPU number population per target. When enabled, each message is tagged with its originating CPU. The sysdata is dynamically updated at message time and appended after any existing userdata.

The CPU number is formatted as "cpu=XX" and is added to the extradata buffer, respecting the existing size limits.

Signed-off-by: Breno Leitao leitao@debian.org Reviewed-by: Simon Horman horms@kernel.org --- drivers/net/netconsole.c | 53 +++++++++++++++++++++++++++++++++++++++--------- 1 file changed, 43 insertions(+), 10 deletions(-)

diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c index 50739c7dbfb6ad5b1a65ef33325cf4dd6ed02031..f77eddf221850fe2778cd479e49c91ad695aba3c 100644 --- a/drivers/net/netconsole.c +++ b/drivers/net/netconsole.c @@ -1117,6 +1117,40 @@ static void populate_configfs_item(struct netconsole_target *nt, init_target_config_group(nt, target_name); }

+/* + * prepare_extradata - append sysdata at extradata_complete in runtime + * @nt: target to send message to + */ +static int prepare_extradata(struct netconsole_target *nt) +{ + int sysdata_len, extradata_len; + + /* userdata was appended when configfs write helper was called + * by update_userdata(). + */ + extradata_len = nt->userdata_length; + + if (!(nt->sysdata_fields & CPU_NR)) + goto out; + + /* Append cpu=%d at extradata_complete after userdata str */ + sysdata_len = scnprintf(&nt->extradata_complete[nt->userdata_length], + MAX_EXTRADATA_ENTRY_LEN, " cpu=%u\n", + raw_smp_processor_id()); + + extradata_len += sysdata_len; + + WARN_ON_ONCE(extradata_len > + MAX_EXTRADATA_ENTRY_LEN * MAX_EXTRADATA_ITEMS); + +out: + return extradata_len; +} +#else /* CONFIG_NETCONSOLE_DYNAMIC not set */ +static int prepare_extradata(struct netconsole_target *nt) +{ + return 0; +} #endif /* CONFIG_NETCONSOLE_DYNAMIC */

/* Handle network interface device notifications */ @@ -1251,16 +1285,14 @@ static void append_release(char *buf)

static void send_fragmented_body(struct netconsole_target *nt, const char *msgbody, int header_len, - int msgbody_len) + int msgbody_len, int extradata_len) { int sent_extradata, preceding_bytes; const char *extradata = NULL; int body_len, offset = 0; - int extradata_len = 0;

#ifdef CONFIG_NETCONSOLE_DYNAMIC extradata = nt->extradata_complete; - extradata_len = nt->userdata_length; #endif

/* body_len represents the number of bytes that will be sent. This is @@ -1341,7 +1373,8 @@ static void send_fragmented_body(struct netconsole_target *nt, static void send_msg_fragmented(struct netconsole_target *nt, const char *msg, int msg_len, - int release_len) + int release_len, + int extradata_len) { int header_len, msgbody_len; const char *msgbody; @@ -1369,7 +1402,8 @@ static void send_msg_fragmented(struct netconsole_target *nt, /* for now on, the header will be persisted, and the msgbody * will be replaced */ - send_fragmented_body(nt, msgbody, header_len, msgbody_len); + send_fragmented_body(nt, msgbody, header_len, msgbody_len, + extradata_len); }

/** @@ -1385,12 +1419,10 @@ static void send_msg_fragmented(struct netconsole_target *nt, static void send_ext_msg_udp(struct netconsole_target *nt, const char *msg, int msg_len) { - int extradata_len = 0; int release_len = 0; + int extradata_len;

-#ifdef CONFIG_NETCONSOLE_DYNAMIC - extradata_len = nt->userdata_length; -#endif + extradata_len = prepare_extradata(nt);

if (nt->release) release_len = strlen(init_utsname()->release) + 1; @@ -1398,7 +1430,8 @@ static void send_ext_msg_udp(struct netconsole_target *nt, const char *msg, if (msg_len + release_len + extradata_len <= MAX_PRINT_CHUNK) return send_msg_no_fragmentation(nt, msg, msg_len, release_len);

- return send_msg_fragmented(nt, msg, msg_len, release_len); + return send_msg_fragmented(nt, msg, msg_len, release_len, + extradata_len); }

static void write_ext_msg(struct console *con, const char *msg,

Update the netconsole documentation to explain the new feature that allows automatic population of the CPU number.

The key changes include introducing a new section titled "CPU number auto population in userdata", explaining how to enable the CPU number auto-population feature by writing to the "populate_cpu_nr" file in the netconsole configfs hierarchy.

This documentation update ensures users are aware of the new CPU number auto-population functionality and how to leverage it for better demultiplexing and visibility of parallel netconsole output.

Signed-off-by: Breno Leitao leitao@debian.org Reviewed-by: Simon Horman horms@kernel.org --- Documentation/networking/netconsole.rst | 45 +++++++++++++++++++++++++++++++++ 1 file changed, 45 insertions(+)

diff --git a/Documentation/networking/netconsole.rst b/Documentation/networking/netconsole.rst index 94c4680fdf3e7e1a0020d11b44547acfd68072a5..84803c59968a3237012fab821f432eb531aba45c 100644 --- a/Documentation/networking/netconsole.rst +++ b/Documentation/networking/netconsole.rst @@ -17,6 +17,8 @@ Release prepend support by Breno Leitao leitao@debian.org, Jul 7 2023

Userdata append support by Matthew Wood thepacketgeek@gmail.com, Jan 22 2024

+Sysdata append support by Breno Leitao leitao@debian.org, Jan 15 2025 + Please send bug reports to Matt Mackall mpm@selenic.com Satyam Sharma satyam.sharma@gmail.com, and Cong Wang xiyou.wangcong@gmail.com

@@ -238,6 +240,49 @@ Delete `userdata` entries with `rmdir`::

It is recommended to not write user data values with newlines.

+CPU number auto population in userdata +-------------------------------------- + +Inside the netconsole configfs hierarchy, there is a file called +`cpu_nr` under the `userdata` directory. This file is used to enable or disable +the automatic CPU number population feature. This feature automatically +populates the CPU number that is sending the message. + +To enable the CPU number auto-population:: + + echo 1 > /sys/kernel/config/netconsole/target1/userdata/cpu_nr + +When this option is enabled, the netconsole messages will include an additional +line in the userdata field with the format `cpu=<cpu_number>`. This allows the +receiver of the netconsole messages to easily differentiate and demultiplex +messages originating from different CPUs, which is particularly useful when +dealing with parallel log output. + +Example:: + + echo "This is a message" > /dev/kmsg + 12,607,22085407756,-;This is a message + cpu=42 + +In this example, the message was sent by CPU 42. + +.. note:: + + If the user has set a conflicting `cpu` key in the userdata dictionary, + both keys will be reported, with the kernel-populated entry appearing after + the user one. For example:: + + # User-defined CPU entry + mkdir -p /sys/kernel/config/netconsole/target1/userdata/cpu + echo "1" > /sys/kernel/config/netconsole/target1/userdata/cpu/value + + Output might look like:: + + 12,607,22085407756,-;This is a message + cpu=1 + cpu=42 # kernel-populated value + + Extended console: =================