[PATCH 22/23] printk: Add printk_syslog.c and .h

[Joe Perches]

Move syslog functions to a separate file.
Add compilation unit to Makefile.

Signed-off-by: Joe Perches <joe@xxxxxxxxxxx>
---
 kernel/printk/Makefile        |    1 +
 kernel/printk/printk.c        |  351 +---------------------------------------
 kernel/printk/printk_syslog.c |  354 +++++++++++++++++++++++++++++++++++++++++
 kernel/printk/printk_syslog.h |   12 ++
 4 files changed, 371 insertions(+), 347 deletions(-)
 create mode 100644 kernel/printk/printk_syslog.c
 create mode 100644 kernel/printk/printk_syslog.h

diff --git a/kernel/printk/Makefile b/kernel/printk/Makefile
index bda335f..7947661 100644
--- a/kernel/printk/Makefile
+++ b/kernel/printk/Makefile
@@ -1,4 +1,5 @@
 obj-y	= printk.o
 obj-y	+= printk_log.o
 obj-y	+= devkmsg.o
+obj-y	+= printk_syslog.o
 obj-$(CONFIG_A11Y_BRAILLE_CONSOLE)	+= braille.o
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 343b0ce..cba438e 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -30,12 +30,10 @@
 #include <linux/security.h>
 #include <linux/bootmem.h>
 #include <linux/memblock.h>
-#include <linux/syscalls.h>
 #include <linux/kexec.h>
 #include <linux/kdb.h>
 #include <linux/ratelimit.h>
 #include <linux/kmsg_dump.h>
-#include <linux/syslog.h>
 #include <linux/cpu.h>
 #include <linux/notifier.h>
 #include <linux/rculist.h>
@@ -49,6 +47,7 @@
 #include "console_cmdline.h"
 #include "braille.h"
 #include "printk_log.h"
+#include "printk_syslog.h"
 
 /*
  * Architectures can override it:
@@ -122,11 +121,6 @@ EXPORT_SYMBOL(console_set_on_cmdline);
 static int console_may_schedule;
 
 #ifdef CONFIG_PRINTK
-/* the next printk record to read by syslog(READ) or /proc/kmsg */
-static u64 syslog_seq;
-static u32 syslog_idx;
-static enum printk_log_flags syslog_prev;
-static size_t syslog_partial;
 
 /* the next printk record to write to the console */
 static u64 console_seq;
@@ -272,340 +266,6 @@ static inline void boot_delay_msec(void)
 }
 #endif
 
-#ifdef CONFIG_SECURITY_DMESG_RESTRICT
-int dmesg_restrict = 1;
-#else
-int dmesg_restrict;
-#endif
-
-static int syslog_action_restricted(int type)
-{
-	if (dmesg_restrict)
-		return 1;
-	/* Unless restricted, we allow "read all" and "get buffer size" for everybody */
-	return type != SYSLOG_ACTION_READ_ALL && type != SYSLOG_ACTION_SIZE_BUFFER;
-}
-
-static int check_syslog_permissions(int type, bool from_file)
-{
-	/*
-	 * If this is from /proc/kmsg and we've already opened it, then we've
-	 * already done the capabilities checks at open time.
-	 */
-	if (from_file && type != SYSLOG_ACTION_OPEN)
-		return 0;
-
-	if (syslog_action_restricted(type)) {
-		if (capable(CAP_SYSLOG))
-			return 0;
-		/* For historical reasons, accept CAP_SYS_ADMIN too, with a warning */
-		if (capable(CAP_SYS_ADMIN)) {
-			printk_once(KERN_WARNING "%s (%d): "
-				 "Attempt to access syslog with CAP_SYS_ADMIN "
-				 "but no CAP_SYSLOG (deprecated).\n",
-				 current->comm, task_pid_nr(current));
-			return 0;
-		}
-		return -EPERM;
-	}
-	return 0;
-}
-
-static int syslog_print(char __user *buf, int size)
-{
-	char *text;
-	struct printk_log *msg;
-	int len = 0;
-
-	text = kmalloc(PRINTK_LOG_LINE_MAX + PRINTK_PREFIX_MAX, GFP_KERNEL);
-	if (!text)
-		return -ENOMEM;
-
-	while (size > 0) {
-		size_t n;
-		size_t skip;
-
-		raw_spin_lock_irq(&printk_logbuf_lock);
-		if (syslog_seq < printk_log_first_seq) {
-			/* messages are gone, move to first one */
-			syslog_seq = printk_log_first_seq;
-			syslog_idx = printk_log_first_idx;
-			syslog_prev = 0;
-			syslog_partial = 0;
-		}
-		if (syslog_seq == printk_log_next_seq) {
-			raw_spin_unlock_irq(&printk_logbuf_lock);
-			break;
-		}
-
-		skip = syslog_partial;
-		msg = printk_log_from_idx(syslog_idx);
-		n = printk_msg_print_text(msg, syslog_prev, true, text,
-					  PRINTK_LOG_LINE_MAX + PRINTK_PREFIX_MAX);
-		if (n - syslog_partial <= size) {
-			/* message fits into buffer, move forward */
-			syslog_idx = printk_log_next(syslog_idx);
-			syslog_seq++;
-			syslog_prev = msg->flags;
-			n -= syslog_partial;
-			syslog_partial = 0;
-		} else if (!len){
-			/* partial read(), remember position */
-			n = size;
-			syslog_partial += n;
-		} else
-			n = 0;
-		raw_spin_unlock_irq(&printk_logbuf_lock);
-
-		if (!n)
-			break;
-
-		if (copy_to_user(buf, text + skip, n)) {
-			if (!len)
-				len = -EFAULT;
-			break;
-		}
-
-		len += n;
-		size -= n;
-		buf += n;
-	}
-
-	kfree(text);
-	return len;
-}
-
-static int syslog_print_all(char __user *buf, int size, bool clear)
-{
-	char *text;
-	int len = 0;
-
-	text = kmalloc(PRINTK_LOG_LINE_MAX + PRINTK_PREFIX_MAX, GFP_KERNEL);
-	if (!text)
-		return -ENOMEM;
-
-	raw_spin_lock_irq(&printk_logbuf_lock);
-	if (buf) {
-		u64 next_seq;
-		u64 seq;
-		u32 idx;
-		enum printk_log_flags prev;
-
-		if (printk_log_clear_seq < printk_log_first_seq) {
-			/* messages are gone, move to first available one */
-			printk_log_clear_seq = printk_log_first_seq;
-			printk_log_clear_idx = printk_log_first_idx;
-		}
-
-		/*
-		 * Find first record that fits, including all following records,
-		 * into the user-provided buffer for this dump.
-		 */
-		seq = printk_log_clear_seq;
-		idx = printk_log_clear_idx;
-		prev = 0;
-		while (seq < printk_log_next_seq) {
-			struct printk_log *msg = printk_log_from_idx(idx);
-
-			len += printk_msg_print_text(msg, prev, true, NULL, 0);
-			prev = msg->flags;
-			idx = printk_log_next(idx);
-			seq++;
-		}
-
-		/* move first record forward until length fits into the buffer */
-		seq = printk_log_clear_seq;
-		idx = printk_log_clear_idx;
-		prev = 0;
-		while (len > size && seq < printk_log_next_seq) {
-			struct printk_log *msg = printk_log_from_idx(idx);
-
-			len -= printk_msg_print_text(msg, prev, true, NULL, 0);
-			prev = msg->flags;
-			idx = printk_log_next(idx);
-			seq++;
-		}
-
-		/* last message fitting into this dump */
-		next_seq = printk_log_next_seq;
-
-		len = 0;
-		prev = 0;
-		while (len >= 0 && seq < next_seq) {
-			struct printk_log *msg = printk_log_from_idx(idx);
-			int textlen;
-
-			textlen = printk_msg_print_text(msg, prev, true, text,
-							PRINTK_LOG_LINE_MAX + PRINTK_PREFIX_MAX);
-			if (textlen < 0) {
-				len = textlen;
-				break;
-			}
-			idx = printk_log_next(idx);
-			seq++;
-			prev = msg->flags;
-
-			raw_spin_unlock_irq(&printk_logbuf_lock);
-			if (copy_to_user(buf + len, text, textlen))
-				len = -EFAULT;
-			else
-				len += textlen;
-			raw_spin_lock_irq(&printk_logbuf_lock);
-
-			if (seq < printk_log_first_seq) {
-				/* messages are gone, move to next one */
-				seq = printk_log_first_seq;
-				idx = printk_log_first_idx;
-				prev = 0;
-			}
-		}
-	}
-
-	if (clear) {
-		printk_log_clear_seq = printk_log_next_seq;
-		printk_log_clear_idx = printk_log_next_idx;
-	}
-	raw_spin_unlock_irq(&printk_logbuf_lock);
-
-	kfree(text);
-	return len;
-}
-
-int do_syslog(int type, char __user *buf, int len, bool from_file)
-{
-	bool clear = false;
-	static int saved_console_loglevel = -1;
-	int error;
-
-	error = check_syslog_permissions(type, from_file);
-	if (error)
-		goto out;
-
-	error = security_syslog(type);
-	if (error)
-		return error;
-
-	switch (type) {
-	case SYSLOG_ACTION_CLOSE:	/* Close log */
-		break;
-	case SYSLOG_ACTION_OPEN:	/* Open log */
-		break;
-	case SYSLOG_ACTION_READ:	/* Read from log */
-		error = -EINVAL;
-		if (!buf || len < 0)
-			goto out;
-		error = 0;
-		if (!len)
-			goto out;
-		if (!access_ok(VERIFY_WRITE, buf, len)) {
-			error = -EFAULT;
-			goto out;
-		}
-		error = wait_event_interruptible(printk_log_wait,
-						 syslog_seq != printk_log_next_seq);
-		if (error)
-			goto out;
-		error = syslog_print(buf, len);
-		break;
-	/* Read/clear last kernel messages */
-	case SYSLOG_ACTION_READ_CLEAR:
-		clear = true;
-		/* FALL THRU */
-	/* Read last kernel messages */
-	case SYSLOG_ACTION_READ_ALL:
-		error = -EINVAL;
-		if (!buf || len < 0)
-			goto out;
-		error = 0;
-		if (!len)
-			goto out;
-		if (!access_ok(VERIFY_WRITE, buf, len)) {
-			error = -EFAULT;
-			goto out;
-		}
-		error = syslog_print_all(buf, len, clear);
-		break;
-	/* Clear ring buffer */
-	case SYSLOG_ACTION_CLEAR:
-		syslog_print_all(NULL, 0, true);
-		break;
-	/* Disable logging to console */
-	case SYSLOG_ACTION_CONSOLE_OFF:
-		if (saved_console_loglevel == -1)
-			saved_console_loglevel = console_loglevel;
-		console_loglevel = minimum_console_loglevel;
-		break;
-	/* Enable logging to console */
-	case SYSLOG_ACTION_CONSOLE_ON:
-		if (saved_console_loglevel != -1) {
-			console_loglevel = saved_console_loglevel;
-			saved_console_loglevel = -1;
-		}
-		break;
-	/* Set level of messages printed to console */
-	case SYSLOG_ACTION_CONSOLE_LEVEL:
-		error = -EINVAL;
-		if (len < 1 || len > 8)
-			goto out;
-		if (len < minimum_console_loglevel)
-			len = minimum_console_loglevel;
-		console_loglevel = len;
-		/* Implicitly re-enable logging to console */
-		saved_console_loglevel = -1;
-		error = 0;
-		break;
-	/* Number of chars in the log buffer */
-	case SYSLOG_ACTION_SIZE_UNREAD:
-		raw_spin_lock_irq(&printk_logbuf_lock);
-		if (syslog_seq < printk_log_first_seq) {
-			/* messages are gone, move to first one */
-			syslog_seq = printk_log_first_seq;
-			syslog_idx = printk_log_first_idx;
-			syslog_prev = 0;
-			syslog_partial = 0;
-		}
-		if (from_file) {
-			/*
-			 * Short-cut for poll(/"proc/kmsg") which simply checks
-			 * for pending data, not the size; return the count of
-			 * records, not the length.
-			 */
-			error = printk_log_next_idx - syslog_idx;
-		} else {
-			u64 seq = syslog_seq;
-			u32 idx = syslog_idx;
-			enum printk_log_flags prev = syslog_prev;
-
-			error = 0;
-			while (seq < printk_log_next_seq) {
-				struct printk_log *msg = printk_log_from_idx(idx);
-
-				error += printk_msg_print_text(msg, prev, true, NULL, 0);
-				idx = printk_log_next(idx);
-				seq++;
-				prev = msg->flags;
-			}
-			error -= syslog_partial;
-		}
-		raw_spin_unlock_irq(&printk_logbuf_lock);
-		break;
-	/* Size of the log buffer */
-	case SYSLOG_ACTION_SIZE_BUFFER:
-		error = printk_log_buf_len;
-		break;
-	default:
-		error = -EINVAL;
-		break;
-	}
-out:
-	return error;
-}
-
-SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
-{
-	return do_syslog(type, buf, len, SYSLOG_FROM_CALL);
-}
-
 static bool __read_mostly ignore_loglevel;
 
 static int __init ignore_loglevel_setup(char *str)
@@ -1063,11 +723,8 @@ EXPORT_SYMBOL(printk);
 
 #define PRINTK_LOG_LINE_MAX	0
 #define PRINTK_PREFIX_MAX		0
-static u64 syslog_seq;
-static u32 syslog_idx;
 static u64 console_seq;
 static u32 console_idx;
-static enum printk_log_flags syslog_prev;
 u64 printk_log_first_seq;
 u32 printk_log_first_idx;
 u64 printk_log_next_seq;
@@ -1703,9 +1360,9 @@ void register_console(struct console *newcon)
 		 * for us.
 		 */
 		raw_spin_lock_irqsave(&printk_logbuf_lock, flags);
-		console_seq = syslog_seq;
-		console_idx = syslog_idx;
-		console_prev = syslog_prev;
+		console_seq = printk_syslog_seq;
+		console_idx = printk_syslog_idx;
+		console_prev = printk_syslog_prev;
 		raw_spin_unlock_irqrestore(&printk_logbuf_lock, flags);
 		/*
 		 * We're about to replay the log buffer.  Only do this to the
diff --git a/kernel/printk/printk_syslog.c b/kernel/printk/printk_syslog.c
new file mode 100644
index 0000000..65f288b
--- /dev/null
+++ b/kernel/printk/printk_syslog.c
@@ -0,0 +1,354 @@
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/security.h>
+#include <linux/syscalls.h>
+#include <linux/syslog.h>
+
+#include "printk_log.h"
+#include "printk_syslog.h"
+
+/* the next printk record to read by syslog(READ) or /proc/kmsg */
+u64 printk_syslog_seq;
+u32 printk_syslog_idx;
+enum printk_log_flags printk_syslog_prev;
+
+#ifdef CONFIG_PRINTK
+
+static size_t printk_syslog_partial;
+
+#ifdef CONFIG_SECURITY_DMESG_RESTRICT
+int dmesg_restrict = 1;
+#else
+int dmesg_restrict;
+#endif
+
+static int printk_syslog_action_restricted(int type)
+{
+	if (dmesg_restrict)
+		return 1;
+	/* Unless restricted, we allow "read all" and "get buffer size" for everybody */
+	return type != SYSLOG_ACTION_READ_ALL && type != SYSLOG_ACTION_SIZE_BUFFER;
+}
+
+static int check_syslog_permissions(int type, bool from_file)
+{
+	/*
+	 * If this is from /proc/kmsg and we've already opened it, then we've
+	 * already done the capabilities checks at open time.
+	 */
+	if (from_file && type != SYSLOG_ACTION_OPEN)
+		return 0;
+
+	if (printk_syslog_action_restricted(type)) {
+		if (capable(CAP_SYSLOG))
+			return 0;
+		/* For historical reasons, accept CAP_SYS_ADMIN too, with a warning */
+		if (capable(CAP_SYS_ADMIN)) {
+			printk_once(KERN_WARNING "%s (%d): "
+				 "Attempt to access syslog with CAP_SYS_ADMIN "
+				 "but no CAP_SYSLOG (deprecated).\n",
+				 current->comm, task_pid_nr(current));
+			return 0;
+		}
+		return -EPERM;
+	}
+	return 0;
+}
+
+static int printk_syslog_print(char __user *buf, int size)
+{
+	char *text;
+	struct printk_log *msg;
+	int len = 0;
+
+	text = kmalloc(PRINTK_LOG_LINE_MAX + PRINTK_PREFIX_MAX, GFP_KERNEL);
+	if (!text)
+		return -ENOMEM;
+
+	while (size > 0) {
+		size_t n;
+		size_t skip;
+
+		raw_spin_lock_irq(&printk_logbuf_lock);
+		if (printk_syslog_seq < printk_log_first_seq) {
+			/* messages are gone, move to first one */
+			printk_syslog_seq = printk_log_first_seq;
+			printk_syslog_idx = printk_log_first_idx;
+			printk_syslog_prev = 0;
+			printk_syslog_partial = 0;
+		}
+		if (printk_syslog_seq == printk_log_next_seq) {
+			raw_spin_unlock_irq(&printk_logbuf_lock);
+			break;
+		}
+
+		skip = printk_syslog_partial;
+		msg = printk_log_from_idx(printk_syslog_idx);
+		n = printk_msg_print_text(msg, printk_syslog_prev, true, text,
+					  PRINTK_LOG_LINE_MAX + PRINTK_PREFIX_MAX);
+		if (n - printk_syslog_partial <= size) {
+			/* message fits into buffer, move forward */
+			printk_syslog_idx = printk_log_next(printk_syslog_idx);
+			printk_syslog_seq++;
+			printk_syslog_prev = msg->flags;
+			n -= printk_syslog_partial;
+			printk_syslog_partial = 0;
+		} else if (!len){
+			/* partial read(), remember position */
+			n = size;
+			printk_syslog_partial += n;
+		} else
+			n = 0;
+		raw_spin_unlock_irq(&printk_logbuf_lock);
+
+		if (!n)
+			break;
+
+		if (copy_to_user(buf, text + skip, n)) {
+			if (!len)
+				len = -EFAULT;
+			break;
+		}
+
+		len += n;
+		size -= n;
+		buf += n;
+	}
+
+	kfree(text);
+	return len;
+}
+
+static int printk_syslog_print_all(char __user *buf, int size, bool clear)
+{
+	char *text;
+	int len = 0;
+
+	text = kmalloc(PRINTK_LOG_LINE_MAX + PRINTK_PREFIX_MAX, GFP_KERNEL);
+	if (!text)
+		return -ENOMEM;
+
+	raw_spin_lock_irq(&printk_logbuf_lock);
+	if (buf) {
+		u64 next_seq;
+		u64 seq;
+		u32 idx;
+		enum printk_log_flags prev;
+
+		if (printk_log_clear_seq < printk_log_first_seq) {
+			/* messages are gone, move to first available one */
+			printk_log_clear_seq = printk_log_first_seq;
+			printk_log_clear_idx = printk_log_first_idx;
+		}
+
+		/*
+		 * Find first record that fits, including all following records,
+		 * into the user-provided buffer for this dump.
+		 */
+		seq = printk_log_clear_seq;
+		idx = printk_log_clear_idx;
+		prev = 0;
+		while (seq < printk_log_next_seq) {
+			struct printk_log *msg = printk_log_from_idx(idx);
+
+			len += printk_msg_print_text(msg, prev, true, NULL, 0);
+			prev = msg->flags;
+			idx = printk_log_next(idx);
+			seq++;
+		}
+
+		/* move first record forward until length fits into the buffer */
+		seq = printk_log_clear_seq;
+		idx = printk_log_clear_idx;
+		prev = 0;
+		while (len > size && seq < printk_log_next_seq) {
+			struct printk_log *msg = printk_log_from_idx(idx);
+
+			len -= printk_msg_print_text(msg, prev, true, NULL, 0);
+			prev = msg->flags;
+			idx = printk_log_next(idx);
+			seq++;
+		}
+
+		/* last message fitting into this dump */
+		next_seq = printk_log_next_seq;
+
+		len = 0;
+		prev = 0;
+		while (len >= 0 && seq < next_seq) {
+			struct printk_log *msg = printk_log_from_idx(idx);
+			int textlen;
+
+			textlen = printk_msg_print_text(msg, prev, true, text,
+							PRINTK_LOG_LINE_MAX + PRINTK_PREFIX_MAX);
+			if (textlen < 0) {
+				len = textlen;
+				break;
+			}
+			idx = printk_log_next(idx);
+			seq++;
+			prev = msg->flags;
+
+			raw_spin_unlock_irq(&printk_logbuf_lock);
+			if (copy_to_user(buf + len, text, textlen))
+				len = -EFAULT;
+			else
+				len += textlen;
+			raw_spin_lock_irq(&printk_logbuf_lock);
+
+			if (seq < printk_log_first_seq) {
+				/* messages are gone, move to next one */
+				seq = printk_log_first_seq;
+				idx = printk_log_first_idx;
+				prev = 0;
+			}
+		}
+	}
+
+	if (clear) {
+		printk_log_clear_seq = printk_log_next_seq;
+		printk_log_clear_idx = printk_log_next_idx;
+	}
+	raw_spin_unlock_irq(&printk_logbuf_lock);
+
+	kfree(text);
+	return len;
+}
+
+int do_syslog(int type, char __user *buf, int len, bool from_file)
+{
+	bool clear = false;
+	static int saved_console_loglevel = -1;
+	int error;
+
+	error = check_syslog_permissions(type, from_file);
+	if (error)
+		goto out;
+
+	error = security_syslog(type);
+	if (error)
+		return error;
+
+	switch (type) {
+	case SYSLOG_ACTION_CLOSE:	/* Close log */
+		break;
+	case SYSLOG_ACTION_OPEN:	/* Open log */
+		break;
+	case SYSLOG_ACTION_READ:	/* Read from log */
+		error = -EINVAL;
+		if (!buf || len < 0)
+			goto out;
+		error = 0;
+		if (!len)
+			goto out;
+		if (!access_ok(VERIFY_WRITE, buf, len)) {
+			error = -EFAULT;
+			goto out;
+		}
+		error = wait_event_interruptible(printk_log_wait,
+						 printk_syslog_seq != printk_log_next_seq);
+		if (error)
+			goto out;
+		error = printk_syslog_print(buf, len);
+		break;
+	/* Read/clear last kernel messages */
+	case SYSLOG_ACTION_READ_CLEAR:
+		clear = true;
+		/* FALL THRU */
+	/* Read last kernel messages */
+	case SYSLOG_ACTION_READ_ALL:
+		error = -EINVAL;
+		if (!buf || len < 0)
+			goto out;
+		error = 0;
+		if (!len)
+			goto out;
+		if (!access_ok(VERIFY_WRITE, buf, len)) {
+			error = -EFAULT;
+			goto out;
+		}
+		error = printk_syslog_print_all(buf, len, clear);
+		break;
+	/* Clear ring buffer */
+	case SYSLOG_ACTION_CLEAR:
+		printk_syslog_print_all(NULL, 0, true);
+		break;
+	/* Disable logging to console */
+	case SYSLOG_ACTION_CONSOLE_OFF:
+		if (saved_console_loglevel == -1)
+			saved_console_loglevel = console_loglevel;
+		console_loglevel = minimum_console_loglevel;
+		break;
+	/* Enable logging to console */
+	case SYSLOG_ACTION_CONSOLE_ON:
+		if (saved_console_loglevel != -1) {
+			console_loglevel = saved_console_loglevel;
+			saved_console_loglevel = -1;
+		}
+		break;
+	/* Set level of messages printed to console */
+	case SYSLOG_ACTION_CONSOLE_LEVEL:
+		error = -EINVAL;
+		if (len < 1 || len > 8)
+			goto out;
+		if (len < minimum_console_loglevel)
+			len = minimum_console_loglevel;
+		console_loglevel = len;
+		/* Implicitly re-enable logging to console */
+		saved_console_loglevel = -1;
+		error = 0;
+		break;
+	/* Number of chars in the log buffer */
+	case SYSLOG_ACTION_SIZE_UNREAD:
+		raw_spin_lock_irq(&printk_logbuf_lock);
+		if (printk_syslog_seq < printk_log_first_seq) {
+			/* messages are gone, move to first one */
+			printk_syslog_seq = printk_log_first_seq;
+			printk_syslog_idx = printk_log_first_idx;
+			printk_syslog_prev = 0;
+			printk_syslog_partial = 0;
+		}
+		if (from_file) {
+			/*
+			 * Short-cut for poll(/"proc/kmsg") which simply checks
+			 * for pending data, not the size; return the count of
+			 * records, not the length.
+			 */
+			error = printk_log_next_idx - printk_syslog_idx;
+		} else {
+			u64 seq = printk_syslog_seq;
+			u32 idx = printk_syslog_idx;
+			enum printk_log_flags prev = printk_syslog_prev;
+
+			error = 0;
+			while (seq < printk_log_next_seq) {
+				struct printk_log *msg = printk_log_from_idx(idx);
+
+				error += printk_msg_print_text(msg, prev, true, NULL, 0);
+				idx = printk_log_next(idx);
+				seq++;
+				prev = msg->flags;
+			}
+			error -= printk_syslog_partial;
+		}
+		raw_spin_unlock_irq(&printk_logbuf_lock);
+		break;
+	/* Size of the log buffer */
+	case SYSLOG_ACTION_SIZE_BUFFER:
+		error = printk_log_buf_len;
+		break;
+	default:
+		error = -EINVAL;
+		break;
+	}
+out:
+	return error;
+}
+
+SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
+{
+	return do_syslog(type, buf, len, SYSLOG_FROM_CALL);
+}
+
+#endif
diff --git a/kernel/printk/printk_syslog.h b/kernel/printk/printk_syslog.h
new file mode 100644
index 0000000..dce93c0
--- /dev/null
+++ b/kernel/printk/printk_syslog.h
@@ -0,0 +1,12 @@
+#ifndef _PRINTK_SYSLOG_H
+#define _PRINTK_SYSLOG_H
+
+#include <linux/syscalls.h>
+#include <linux/syslog.h>
+
+/* the next printk record to read by syslog(READ) or /proc/kmsg */
+extern u64 printk_syslog_seq;
+extern u32 printk_syslog_idx;
+extern enum printk_log_flags printk_syslog_prev;
+
+#endif
-- 
1.7.10.4

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