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Commit b4cb3527 authored by Patrick Daly's avatar Patrick Daly
Browse files

printk: Add LOG_BUF_MAGIC 



Enable post-mortem ramdump analysis to retrieve the valid portions of the
log buffer in the event that portions are corrupted.

Change-Id: Icc47bdb5c030d8548509d14c8016892cc393dafa
Signed-off-by: default avatarPatrick Daly <pdaly@codeaurora.org>
parent bba41e29

kernel/printk.c

+12 −0
Original line number Diff line number Diff line
@@ -212,6 +212,9 @@ struct log { 
	u8 facility;		/* syslog facility */

	u8 flags:5;		/* internal record flags */

	u8 level:3;		/* syslog level */

#if defined(CONFIG_LOG_BUF_MAGIC)

	u32 magic;		/* handle for ramdump analysis tools */

#endif

};



/*
@@ -276,6 +279,13 @@ static u32 syslog_oops_buf_idx; 
static const char log_oops_end[] = "---end of oops log buffer---";

#endif



#if defined(CONFIG_LOG_BUF_MAGIC)

static u32 __log_align __used = LOG_ALIGN;

#define LOG_MAGIC(msg) ((msg)->magic = 0x5d7aefca)

#else

#define LOG_MAGIC(msg)

#endif



/* cpu currently holding logbuf_lock */

static volatile unsigned int logbuf_cpu = UINT_MAX;
@@ -434,6 +444,7 @@ static void log_store(int facility, int level, 
		 * to signify a wrap around.

		 */

		memset(log_buf + log_next_idx, 0, sizeof(struct log));

		LOG_MAGIC((struct log *)(log_buf + log_next_idx));

		log_next_idx = 0;

	}
@@ -446,6 +457,7 @@ static void log_store(int facility, int level, 
	msg->facility = facility;

	msg->level = level & 7;

	msg->flags = flags & 0x1f;

	LOG_MAGIC(msg);

	if (ts_nsec > 0)

		msg->ts_nsec = ts_nsec;

	else

lib/Kconfig.debug

+9 −0
Original line number Diff line number Diff line
@@ -1509,6 +1509,15 @@ config OOPS_LOG_BUFFER 
	  allow wrap around but preserve the first oops and onward kernel

	  messages until buffer becomes full.



config LOG_BUF_MAGIC

	bool "Recovery of partially corrupted dmesg from ramdumps"

	depends on PRINTK

	help

	  Select this option to add a magic number to the log buf record. In the

	  event that a log buf record is corrupted, post-mortem crash analysis

	  tools may use this magic number to search for the next noncorrupted

	  log record.



config OOPS_LOG_BUF_SHIFT

	int "Oops log buffer size (16 => 64KB, 17 => 128KB)"

	depends on OOPS_LOG_BUFFER