6 files changed, 96 insertions, 23 deletions

diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst
index a7fae4538946..c37ec7cd9c06 100644
--- a/Documentation/core-api/printk-formats.rst
+++ b/Documentation/core-api/printk-formats.rst
@@ -13,6 +13,10 @@ Integer types
 
         If variable is of Type,         use printk format specifier:
         ------------------------------------------------------------
+                char                    %hhd or %hhx
+                unsigned char           %hhu or %hhx
+                short int               %hd or %hx
+                unsigned short int      %hu or %hx
                 int                     %d or %x
                 unsigned int            %u or %x
                 long                    %ld or %lx
@@ -21,6 +25,10 @@ Integer types
                 unsigned long long      %llu or %llx
                 size_t                  %zu or %zx
                 ssize_t                 %zd or %zx
+                s8                      %hhd or %hhx
+                u8                      %hhu or %hhx
+                s16                     %hd or %hx
+                u16                     %hu or %hx
                 s32                     %d or %x
                 u32                     %u or %x
                 s64                     %lld or %llx
diff --git a/include/linux/kern_levels.h b/include/linux/kern_levels.h
index d237fe854ad9..bf2389c26ae3 100644
--- a/include/linux/kern_levels.h
+++ b/include/linux/kern_levels.h
@@ -14,7 +14,7 @@
 #define KERN_INFO       KERN_SOH "6"    /* informational */
 #define KERN_DEBUG      KERN_SOH "7"    /* debug-level messages */
 
-#define KERN_DEFAULT    KERN_SOH "d"    /* the default kernel loglevel */
+#define KERN_DEFAULT    ""              /* the default kernel loglevel */
 
 /*
  * Annotation for a "continued" line of log printout (only done after a
diff --git a/include/linux/printk.h b/include/linux/printk.h
index 02b5c115d89b..d7c77ed1a4cb 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -18,7 +18,6 @@ static inline int printk_get_level(const char *buffer)
         if (buffer[0] == KERN_SOH_ASCII && buffer[1]) {
                 switch (buffer[1]) {
                 case '0' ... '7':
-                case 'd':       /* KERN_DEFAULT */
                 case 'c':       /* KERN_CONT */
                         return buffer[1];
                 }
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index d3d170374ceb..8eee85bb2687 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -344,7 +344,6 @@ static int console_msg_format = MSG_FORMAT_DEFAULT;
 
 enum log_flags {
         LOG_NEWLINE     = 2,    /* text ended with a newline */
-        LOG_PREFIX      = 4,    /* text started with a prefix */
         LOG_CONT        = 8,    /* text is a fragment of a continuation line */
 };
 
@@ -356,6 +355,9 @@ struct printk_log {
         u8 facility;            /* syslog facility */
         u8 flags:5;             /* internal record flags */
         u8 level:3;             /* syslog level */
+#ifdef CONFIG_PRINTK_CALLER
+        u32 caller_id;            /* thread id or processor id */
+#endif
 }
 #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
 __packed __aligned(4)
@@ -422,7 +424,11 @@ static u64 exclusive_console_stop_seq;
 static u64 clear_seq;
 static u32 clear_idx;
 
+#ifdef CONFIG_PRINTK_CALLER
+#define PREFIX_MAX              48
+#else
 #define PREFIX_MAX              32
+#endif
 #define LOG_LINE_MAX            (1024 - PREFIX_MAX)
 
 #define LOG_LEVEL(v)            ((v) & 0x07)
@@ -577,7 +583,7 @@ static u32 truncate_msg(u16 *text_len, u16 *trunc_msg_len,
 }
 
 /* insert record into the buffer, discard old ones, update heads */
-static int log_store(int facility, int level,
+static int log_store(u32 caller_id, int facility, int level,
                      enum log_flags flags, u64 ts_nsec,
                      const char *dict, u16 dict_len,
                      const char *text, u16 text_len)
@@ -625,6 +631,9 @@ static int log_store(int facility, int level,
                 msg->ts_nsec = ts_nsec;
         else
                 msg->ts_nsec = local_clock();
+#ifdef CONFIG_PRINTK_CALLER
+        msg->caller_id = caller_id;
+#endif
         memset(log_dict(msg) + dict_len, 0, pad_len);
         msg->len = size;
 
@@ -688,12 +697,21 @@ static ssize_t msg_print_ext_header(char *buf, size_t size,
                                     struct printk_log *msg, u64 seq)
 {
         u64 ts_usec = msg->ts_nsec;
+        char caller[20];
+#ifdef CONFIG_PRINTK_CALLER
+        u32 id = msg->caller_id;
+
+        snprintf(caller, sizeof(caller), ",caller=%c%u",
+                 id & 0x80000000 ? 'C' : 'T', id & ~0x80000000);
+#else
+        caller[0] = '\0';
+#endif
 
         do_div(ts_usec, 1000);
 
-        return scnprintf(buf, size, "%u,%llu,%llu,%c;",
-                       (msg->facility << 3) | msg->level, seq, ts_usec,
-                       msg->flags & LOG_CONT ? 'c' : '-');
+        return scnprintf(buf, size, "%u,%llu,%llu,%c%s;",
+                         (msg->facility << 3) | msg->level, seq, ts_usec,
+                         msg->flags & LOG_CONT ? 'c' : '-', caller);
 }
 
 static ssize_t msg_print_ext_body(char *buf, size_t size,
@@ -1038,6 +1056,9 @@ void log_buf_vmcoreinfo_setup(void)
         VMCOREINFO_OFFSET(printk_log, len);
         VMCOREINFO_OFFSET(printk_log, text_len);
         VMCOREINFO_OFFSET(printk_log, dict_len);
+#ifdef CONFIG_PRINTK_CALLER
+        VMCOREINFO_OFFSET(printk_log, caller_id);
+#endif
 }
 #endif
 
@@ -1236,10 +1257,23 @@ static size_t print_time(u64 ts, char *buf)
 {
         unsigned long rem_nsec = do_div(ts, 1000000000);
 
-        return sprintf(buf, "[%5lu.%06lu] ",
+        return sprintf(buf, "[%5lu.%06lu]",
                        (unsigned long)ts, rem_nsec / 1000);
 }
 
+#ifdef CONFIG_PRINTK_CALLER
+static size_t print_caller(u32 id, char *buf)
+{
+        char caller[12];
+
+        snprintf(caller, sizeof(caller), "%c%u",
+                 id & 0x80000000 ? 'C' : 'T', id & ~0x80000000);
+        return sprintf(buf, "[%6s]", caller);
+}
+#else
+#define print_caller(id, buf) 0
+#endif
+
 static size_t print_prefix(const struct printk_log *msg, bool syslog,
                            bool time, char *buf)
 {
@@ -1247,8 +1281,17 @@ static size_t print_prefix(const struct printk_log *msg, bool syslog,
 
         if (syslog)
                 len = print_syslog((msg->facility << 3) | msg->level, buf);
+
         if (time)
                 len += print_time(msg->ts_nsec, buf + len);
+
+        len += print_caller(msg->caller_id, buf + len);
+
+        if (IS_ENABLED(CONFIG_PRINTK_CALLER) || time) {
+                buf[len++] = ' ';
+                buf[len] = '\0';
+        }
+
         return len;
 }
 
@@ -1752,6 +1795,12 @@ static inline void printk_delay(void)
         }
 }
 
+static inline u32 printk_caller_id(void)
+{
+        return in_task() ? task_pid_nr(current) :
+                0x80000000 + raw_smp_processor_id();
+}
+
 /*
  * Continuation lines are buffered, and not committed to the record buffer
  * until the line is complete, or a race forces it. The line fragments
@@ -1761,7 +1810,7 @@ static inline void printk_delay(void)
 static struct cont {
         char buf[LOG_LINE_MAX];
         size_t len;                     /* length == 0 means unused buffer */
-        struct task_struct *owner;      /* task of first print*/
+        u32 caller_id;                  /* printk_caller_id() of first print */
         u64 ts_nsec;                    /* time of first print */
         u8 level;                       /* log level of first message */
         u8 facility;                    /* log facility of first message */
@@ -1773,12 +1822,13 @@ static void cont_flush(void)
         if (cont.len == 0)
                 return;
 
-        log_store(cont.facility, cont.level, cont.flags, cont.ts_nsec,
-                  NULL, 0, cont.buf, cont.len);
+        log_store(cont.caller_id, cont.facility, cont.level, cont.flags,
+                  cont.ts_nsec, NULL, 0, cont.buf, cont.len);
         cont.len = 0;
 }
 
-static bool cont_add(int facility, int level, enum log_flags flags, const char *text, size_t len)
+static bool cont_add(u32 caller_id, int facility, int level,
+                     enum log_flags flags, const char *text, size_t len)
 {
         /* If the line gets too long, split it up in separate records. */
         if (cont.len + len > sizeof(cont.buf)) {
@@ -1789,7 +1839,7 @@ static bool cont_add(int facility, int level, enum log_flags flags, const char *
         if (!cont.len) {
                 cont.facility = facility;
                 cont.level = level;
-                cont.owner = current;
+                cont.caller_id = caller_id;
                 cont.ts_nsec = local_clock();
                 cont.flags = flags;
         }
@@ -1809,13 +1859,15 @@ static bool cont_add(int facility, int level, enum log_flags flags, const char *
 
 static size_t log_output(int facility, int level, enum log_flags lflags, const char *dict, size_t dictlen, char *text, size_t text_len)
 {
+        const u32 caller_id = printk_caller_id();
+
         /*
          * If an earlier line was buffered, and we're a continuation
-         * write from the same process, try to add it to the buffer.
+         * write from the same context, try to add it to the buffer.
          */
         if (cont.len) {
-                if (cont.owner == current && (lflags & LOG_CONT)) {
-                        if (cont_add(facility, level, lflags, text, text_len))
+                if (cont.caller_id == caller_id && (lflags & LOG_CONT)) {
+                        if (cont_add(caller_id, facility, level, lflags, text, text_len))
                                 return text_len;
                 }
                 /* Otherwise, make sure it's flushed */
@@ -1828,12 +1880,13 @@ static size_t log_output(int facility, int level, enum log_flags lflags, const c
 
         /* If it doesn't end in a newline, try to buffer the current line */
         if (!(lflags & LOG_NEWLINE)) {
-                if (cont_add(facility, level, lflags, text, text_len))
+                if (cont_add(caller_id, facility, level, lflags, text, text_len))
                         return text_len;
         }
 
         /* Store it in the record log */
-        return log_store(facility, level, lflags, 0, dict, dictlen, text, text_len);
+        return log_store(caller_id, facility, level, lflags, 0,
+                         dict, dictlen, text, text_len);
 }
 
 /* Must be called under logbuf_lock. */
@@ -1867,9 +1920,6 @@ int vprintk_store(int facility, int level,
                         case '0' ... '7':
                                 if (level == LOGLEVEL_DEFAULT)
                                         level = kern_level - '0';
-                                /* fallthrough */
-                        case 'd':       /* KERN_DEFAULT */
-                                lflags |= LOG_PREFIX;
                                 break;
                         case 'c':       /* KERN_CONT */
                                 lflags |= LOG_CONT;
@@ -1884,7 +1934,7 @@ int vprintk_store(int facility, int level,
                 level = default_message_loglevel;
 
         if (dict)
-                lflags |= LOG_PREFIX|LOG_NEWLINE;
+                lflags |= LOG_NEWLINE;
 
         return log_output(facility, level, lflags,
                           dict, dictlen, text, text_len);
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index e718487c97c3..91ed81250fb3 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -17,6 +17,23 @@ config PRINTK_TIME
           The behavior is also controlled by the kernel command line
           parameter printk.time=1. See Documentation/admin-guide/kernel-parameters.rst
 
+config PRINTK_CALLER
+        bool "Show caller information on printks"
+        depends on PRINTK
+        help
+          Selecting this option causes printk() to add a caller "thread id" (if
+          in task context) or a caller "processor id" (if not in task context)
+          to every message.
+
+          This option is intended for environments where multiple threads
+          concurrently call printk() for many times, for it is difficult to
+          interpret without knowing where these lines (or sometimes individual
+          line which was divided into multiple lines due to race) came from.
+
+          Since toggling after boot makes the code racy, currently there is
+          no option to enable/disable at the kernel command line parameter or
+          sysfs interface.
+
 config CONSOLE_LOGLEVEL_DEFAULT
         int "Default console loglevel (1-15)"
         range 1 15
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 30b00de4f321..791b6fa36905 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1931,7 +1931,6 @@ char *device_node_string(char *buf, char *end, struct device_node *dn,
  *       (legacy clock framework) of the clock
  * - 'Cn' For a clock, it prints the name (Common Clock Framework) or address
  *        (legacy clock framework) of the clock
- * - 'Cr' For a clock, it prints the current rate of the clock
  * - 'G' For flags to be printed as a collection of symbolic strings that would
  *       construct the specific value. Supported flags given by option:
  *       p page flags (see struct page) given as pointer to unsigned long