linux-kernel - [PATCH] printk: Move and rename maximum printk output line length defines

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Date:   Thu, 21 May 2020 11:40:35 -0700
From:   Joe Perches <joe@...ches.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Chenggang Wang <wangchenggang@...o.com>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH] printk: Move and rename maximum printk output line length
 defines

Make the printk output maximum line length globally available.

This can be used to emit logging messages lines that exceed
the single printk maximum length line.

e.g.: the kernel boot command on ARM can be up to 2048 chars

Miscellanea:

o Prefix the defines with PRINTK_

Signed-off-by: Joe Perches <joe@...ches.com>
Acked-by: Petr Mladek <pmladek@...e.com>
---
 include/linux/printk.h | 18 ++++++++++++++++++
 kernel/printk/printk.c | 28 ++++++++++------------------
 2 files changed, 28 insertions(+), 18 deletions(-)

diff --git a/include/linux/printk.h b/include/linux/printk.h
index 38beb97e7018..850dc4d4356f 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -43,6 +43,24 @@ static inline const char *printk_skip_headers(const char *buffer)
 
 #define CONSOLE_EXT_LOG_MAX	8192
 
+/* Maximum length of a single printk */
+
+#ifdef CONFIG_PRINTK
+
+#ifdef CONFIG_PRINTK_CALLER
+#define PRINTK_PREFIX_MAX	48
+#else
+#define PRINTK_PREFIX_MAX	32
+#endif
+#define PRINTK_LOG_LINE_MAX	(1024 - PRINTK_PREFIX_MAX)
+
+#else
+
+#define PRINTK_PREFIX_MAX	0
+#define PRINTK_LOG_LINE_MAX	0
+
+#endif
+
 /* printk's without a loglevel use this.. */
 #define MESSAGE_LOGLEVEL_DEFAULT CONFIG_MESSAGE_LOGLEVEL_DEFAULT
 
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 4f1cc4acef41..fc22a494ef0c 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -443,13 +443,6 @@ 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)
 #define LOG_FACILITY(v)		((v) >> 3 & 0xff)
 
@@ -825,7 +818,7 @@ static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from)
 	size_t len = iov_iter_count(from);
 	ssize_t ret = len;
 
-	if (!user || len > LOG_LINE_MAX)
+	if (!user || len > PRINTK_LOG_LINE_MAX)
 		return -EINVAL;
 
 	/* Ignore when user logging is disabled. */
@@ -1341,7 +1334,7 @@ static size_t msg_print_text(const struct printk_log *msg, bool syslog,
 	const char *text = log_text(msg);
 	size_t text_size = msg->text_len;
 	size_t len = 0;
-	char prefix[PREFIX_MAX];
+	char prefix[PRINTK_PREFIX_MAX];
 	const size_t prefix_len = print_prefix(msg, syslog, time, prefix);
 
 	do {
@@ -1382,7 +1375,7 @@ static int syslog_print(char __user *buf, int size)
 	struct printk_log *msg;
 	int len = 0;
 
-	text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
+	text = kmalloc(PRINTK_LOG_LINE_MAX + PRINTK_PREFIX_MAX, GFP_KERNEL);
 	if (!text)
 		return -ENOMEM;
 
@@ -1412,7 +1405,7 @@ static int syslog_print(char __user *buf, int size)
 		skip = syslog_partial;
 		msg = log_from_idx(syslog_idx);
 		n = msg_print_text(msg, true, syslog_time, text,
-				   LOG_LINE_MAX + PREFIX_MAX);
+				   PRINTK_LOG_LINE_MAX + PRINTK_PREFIX_MAX);
 		if (n - syslog_partial <= size) {
 			/* message fits into buffer, move forward */
 			syslog_idx = log_next(syslog_idx);
@@ -1454,7 +1447,7 @@ static int syslog_print_all(char __user *buf, int size, bool clear)
 	u32 idx;
 	bool time;
 
-	text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
+	text = kmalloc(PRINTK_LOG_LINE_MAX + PRINTK_PREFIX_MAX, GFP_KERNEL);
 	if (!text)
 		return -ENOMEM;
 
@@ -1492,7 +1485,8 @@ static int syslog_print_all(char __user *buf, int size, bool clear)
 	while (len >= 0 && seq < next_seq) {
 		struct printk_log *msg = log_from_idx(idx);
 		int textlen = msg_print_text(msg, true, time, text,
-					     LOG_LINE_MAX + PREFIX_MAX);
+					     PRINTK_LOG_LINE_MAX +
+					     PRINTK_PREFIX_MAX);
 
 		idx = log_next(idx);
 		seq++;
@@ -1845,7 +1839,7 @@ static inline u32 printk_caller_id(void)
  * reached the console in case of a kernel crash.
  */
 static struct cont {
-	char buf[LOG_LINE_MAX];
+	char buf[PRINTK_LOG_LINE_MAX];
 	size_t len;			/* length == 0 means unused buffer */
 	u32 caller_id;			/* printk_caller_id() of first print */
 	u64 ts_nsec;			/* time of first print */
@@ -1931,7 +1925,7 @@ int vprintk_store(int facility, int level,
 		  const char *dict, size_t dictlen,
 		  const char *fmt, va_list args)
 {
-	static char textbuf[LOG_LINE_MAX];
+	static char textbuf[PRINTK_LOG_LINE_MAX];
 	char *text = textbuf;
 	size_t text_len;
 	enum log_flags lflags = 0;
@@ -2088,8 +2082,6 @@ EXPORT_SYMBOL(printk);
 
 #else /* CONFIG_PRINTK */
 
-#define LOG_LINE_MAX		0
-#define PREFIX_MAX		0
 #define printk_time		false
 
 static u64 syslog_seq;
@@ -2396,7 +2388,7 @@ static inline int can_use_console(void)
 void console_unlock(void)
 {
 	static char ext_text[CONSOLE_EXT_LOG_MAX];
-	static char text[LOG_LINE_MAX + PREFIX_MAX];
+	static char text[PRINTK_LOG_LINE_MAX + PRINTK_PREFIX_MAX];
 	unsigned long flags;
 	bool do_cond_resched, retry;