From 430fa6578ba80657b2280bdff7ec0719c832cd85 Mon Sep 17 00:00:00 2001 From: John Ogness Date: Thu, 10 Dec 2020 12:48:01 +0106 Subject: [PATCH 086/323] printk: introduce CONSOLE_LOG_MAX for improved multi-line support Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.215-rt107.tar.xz Instead of using "LOG_LINE_MAX + PREFIX_MAX" for temporary buffer sizes, introduce CONSOLE_LOG_MAX. This represents the maximum size that is allowed to be printed to the console for a single record. Rather than setting CONSOLE_LOG_MAX to "LOG_LINE_MAX + PREFIX_MAX" (1024), increase it to 4096. With a larger buffer size, multi-line records that are nearly LOG_LINE_MAX in length will have a better chance of being fully printed. (When formatting a record for the console, each line of a multi-line record is prepended with a copy of the prefix.) Signed-off-by: John Ogness --- kernel/printk/printk.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 254d4cb73c7a9..6db3c574e4aa8 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -412,8 +412,13 @@ static u64 clear_seq; #else #define PREFIX_MAX 32 #endif + +/* the maximum size allowed to be reserved for a record */ #define LOG_LINE_MAX (1024 - PREFIX_MAX) +/* the maximum size of a formatted record (i.e. with prefix added per line) */ +#define CONSOLE_LOG_MAX 4096 + #define LOG_LEVEL(v) ((v) & 0x07) #define LOG_FACILITY(v) ((v) >> 3 & 0xff) @@ -1475,11 +1480,11 @@ static int syslog_print(char __user *buf, int size) char *text; int len = 0; - text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL); + text = kmalloc(CONSOLE_LOG_MAX, GFP_KERNEL); if (!text) return -ENOMEM; - prb_rec_init_rd(&r, &info, text, LOG_LINE_MAX + PREFIX_MAX); + prb_rec_init_rd(&r, &info, text, CONSOLE_LOG_MAX); while (size > 0) { size_t n; @@ -1545,7 +1550,7 @@ static int syslog_print_all(char __user *buf, int size, bool clear) u64 seq; bool time; - text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL); + text = kmalloc(CONSOLE_LOG_MAX, GFP_KERNEL); if (!text) return -ENOMEM; @@ -1557,7 +1562,7 @@ static int syslog_print_all(char __user *buf, int size, bool clear) */ seq = find_first_fitting_seq(clear_seq, -1, size, true, time); - prb_rec_init_rd(&r, &info, text, LOG_LINE_MAX + PREFIX_MAX); + prb_rec_init_rd(&r, &info, text, CONSOLE_LOG_MAX); len = 0; prb_for_each_record(seq, prb, seq, &r) { @@ -2196,8 +2201,7 @@ EXPORT_SYMBOL(printk); #else /* CONFIG_PRINTK */ -#define LOG_LINE_MAX 0 -#define PREFIX_MAX 0 +#define CONSOLE_LOG_MAX 0 #define printk_time false #define prb_read_valid(rb, seq, r) false @@ -2515,7 +2519,7 @@ 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[CONSOLE_LOG_MAX]; unsigned long flags; bool do_cond_resched, retry; struct printk_info info; -- 2.44.0