[patch 1/4] Add <linux/klog.h>

[patch 1/4] Add <linux/klog.h>

[Vincent Legoll]

[-- Attachment #1: Type: text/plain, Size: 181 bytes --]

Hello,

what about something along the lines of the following,
on top of your patch ?

Or should the kernel-doc be put on another function
instead of that one ?

-- 
Vincent Legoll

[-- Attachment #2: do-syslog-kernel-doc --]
[-- Type: text/plain, Size: 1178 bytes --]

Add do_syslog() kernel-doc

---
commit 95b0721d8b4b46ddf83113fe49492810d7d92060
tree e2715a8cf7eb0d71b3bee2185a5cf98639d79d90
parent de794d2dfd6dd0c38dd552020ac00c46e1df5293
author Vincent Legoll <vincent.legoll@gmail.com> Wed, 20 Dec 2006 01:29:34 +0100
committer Vincent Legoll <vincent.legoll@gmail.com> Wed, 20 Dec 2006 01:29:34 +0100

 kernel/printk.c |   11 ++++++++++-
 1 files changed, 10 insertions(+), 1 deletions(-)

diff --git a/kernel/printk.c b/kernel/printk.c
index 232467e..5416d07 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -164,7 +164,16 @@ out:
 
 __setup("log_buf_len=", log_buf_len_setup);
 
-/* See linux/klog.h for the command numbers passed as the first argument.  */
+/**
+ * do_syslog - operate on kernel messages log
+ * @type: operation to perform
+ * @buf: user-space buffer to copy data into
+ * @len: length of data to copy from log into @buf
+ *
+ * See include/linux/klog.h for the command numbers passed as @type.
+ * Parameters @buf & @len are only used for operations of type %KLOG_READ,
+ * %KLOG_READ_HIST and %KLOG_READ_CLEAR_HIST.
+ */
 int do_syslog(int type, char __user *buf, int len)
 {
 	unsigned long i, j, limit, count;

[patch 0/4] /proc/kmsg permissions, take four

[Zack Weinberg]

Here's yet another revision of the /proc/kmsg permissions patch
series.  To recap, the point is to allow klogd to drop privileges
and continue reading from /proc/kmsg (currently, even if klogd has a
legitimately opened fd on /proc/kmsg, it cannot read from it unless
it has CAP_SYS_ADMIN asserted).  SELinux's pickier and finer-grained
privilege rules for /proc/kmsg are unchanged.

There are two significant changes from the previous revision.  First,
in keeping with the recommended style, I have eliminated the
security_syslog_or_fail() macro.  Instead there is a static array mapping
KLOG_* opcodes to LSM_KLOG_* privilege classes.  This requires slightly
different coding in the security hooks but I think it's clearer overall.
Second, I've incorporated Vincent Legoll's kerneldoc comment for sys_syslog
(nee do_syslog) with some wording improvements and expansion to cover the
klog_* functions introduced part-way through the patch.  I don't think
proc/kmsg.c needs kerneldoc, it's very simple after this patch series.

I've been through Documentation/CodingStyle and satisfied myself that
everything is now in the proper mode.  I don't suppose anyone has comments
on the *content* of the changes...?

zw

[patch 1/4] Add <linux/klog.h>

[Zack Weinberg]

[-- Attachment #1: add_klog_h.diff --]
[-- Type: text/plain, Size: 6322 bytes --]

This patch introduces <linux/klog.h> with symbolic constants for the
various sys_syslog() opcodes, and changes all in-kernel references to
those opcodes to use the constants.  The header is added to the set of
user/kernel interface headers.

zw

Index: linux-2.6/include/linux/Kbuild
===================================================================
--- linux-2.6.orig/include/linux/Kbuild	2006-12-23 08:56:15.000000000 -0800
+++ linux-2.6/include/linux/Kbuild	2006-12-24 11:43:14.000000000 -0800
@@ -100,6 +100,7 @@
 header-y += ixjuser.h
 header-y += jffs2.h
 header-y += keyctl.h
+header-y += klog.h
 header-y += limits.h
 header-y += lock_dlm_plock.h
 header-y += magic.h
Index: linux-2.6/include/linux/klog.h
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6/include/linux/klog.h	2006-12-24 11:43:14.000000000 -0800
@@ -0,0 +1,28 @@
+#ifndef _LINUX_KLOG_H
+#define _LINUX_KLOG_H
+
+/*
+ * Constants for the first argument to the syslog() system call
+ * (aka klogctl()).  These numbers are part of the user space ABI!
+ */
+enum {
+	KLOG_CLOSE           =  0, /* close log */
+	KLOG_OPEN            =  1, /* open log */
+	KLOG_READ            =  2, /* read from log (klogd) */
+
+	KLOG_READ_HIST       =  3, /* read history of log messages (dmesg) */
+	KLOG_READ_CLEAR_HIST =  4, /* read and clear history */
+	KLOG_CLEAR_HIST      =  5, /* just clear history */
+
+	KLOG_DISABLE_CONSOLE =  6, /* disable printk to console */
+	KLOG_ENABLE_CONSOLE  =  7, /* enable printk to console */
+	KLOG_SET_CONSOLE_LVL =  8, /* set minimum severity of messages to be
+				    * printed to console */
+
+	KLOG_GET_UNREAD      =  9, /* return number of unread characters */
+	KLOG_GET_SIZE        = 10, /* return size of log buffer */
+
+	KLOG_OPCODE_MAX
+};
+
+#endif /* klog.h */
Index: linux-2.6/kernel/printk.c
===================================================================
--- linux-2.6.orig/kernel/printk.c	2006-12-23 08:56:15.000000000 -0800
+++ linux-2.6/kernel/printk.c	2006-12-24 11:43:14.000000000 -0800
@@ -32,6 +32,7 @@
 #include <linux/bootmem.h>
 #include <linux/syscalls.h>
 #include <linux/jiffies.h>
+#include <linux/klog.h>
 
 #include <asm/uaccess.h>
 
@@ -163,20 +164,21 @@
 
 __setup("log_buf_len=", log_buf_len_setup);
 
-/*
- * Commands to do_syslog:
+/**
+ * do_syslog - operate on the log of kernel messages
+ * @type: operation to perform
+ * @buf: user-space buffer to copy data into
+ * @len: number of bytes of space available at @buf
+ *
+ * See include/linux/klog.h for the command numbers passed as @type.
+ * The @buf and @len parameters are used with the above meanings for
+ * @type values %KLOG_READ, %KLOG_READ_HIST and %KLOG_READ_CLEAR_HIST.
+ * @len is reused with a different meaning, and @buf ignored, for
+ * %KLOG_SET_CONSOLE_LVL.  Both @buf and @len are ignored for all
+ * other @type values.
  *
- * 	0 -- Close the log.  Currently a NOP.
- * 	1 -- Open the log. Currently a NOP.
- * 	2 -- Read from the log.
- * 	3 -- Read all messages remaining in the ring buffer.
- * 	4 -- Read and clear all messages remaining in the ring buffer
- * 	5 -- Clear ring buffer.
- * 	6 -- Disable printk's to console
- * 	7 -- Enable printk's to console
- *	8 -- Set level of messages printed to console
- *	9 -- Return number of unread characters in the log buffer
- *     10 -- Return size of the log buffer
+ * On failure, returns a negative errno code.  On success, returns a
+ * nonnegative integer whose meaning depends on @type.
  */
 int do_syslog(int type, char __user *buf, int len)
 {
@@ -190,11 +192,11 @@
 		return error;
 
 	switch (type) {
-	case 0:		/* Close log */
+	case KLOG_CLOSE:
 		break;
-	case 1:		/* Open log */
+	case KLOG_OPEN:
 		break;
-	case 2:		/* Read from log */
+	case KLOG_READ:
 		error = -EINVAL;
 		if (!buf || len < 0)
 			goto out;
@@ -225,10 +227,10 @@
 		if (!error)
 			error = i;
 		break;
-	case 4:		/* Read/clear last kernel messages */
+	case KLOG_READ_CLEAR_HIST:
 		do_clear = 1;
 		/* FALL THRU */
-	case 3:		/* Read last kernel messages */
+	case KLOG_READ_HIST:
 		error = -EINVAL;
 		if (!buf || len < 0)
 			goto out;
@@ -281,16 +283,16 @@
 			}
 		}
 		break;
-	case 5:		/* Clear ring buffer */
+	case KLOG_CLEAR_HIST:
 		logged_chars = 0;
 		break;
-	case 6:		/* Disable logging to console */
+	case KLOG_DISABLE_CONSOLE:
 		console_loglevel = minimum_console_loglevel;
 		break;
-	case 7:		/* Enable logging to console */
+	case KLOG_ENABLE_CONSOLE:
 		console_loglevel = default_console_loglevel;
 		break;
-	case 8:		/* Set level of messages printed to console */
+	case KLOG_SET_CONSOLE_LVL:
 		error = -EINVAL;
 		if (len < 1 || len > 8)
 			goto out;
@@ -299,10 +301,10 @@
 		console_loglevel = len;
 		error = 0;
 		break;
-	case 9:		/* Number of chars in the log buffer */
+	case KLOG_GET_UNREAD:
 		error = log_end - log_start;
 		break;
-	case 10:	/* Size of the log buffer */
+	case KLOG_GET_SIZE:
 		error = log_buf_len;
 		break;
 	default:
Index: linux-2.6/fs/proc/kmsg.c
===================================================================
--- linux-2.6.orig/fs/proc/kmsg.c	2006-12-23 08:55:17.000000000 -0800
+++ linux-2.6/fs/proc/kmsg.c	2006-12-24 11:43:14.000000000 -0800
@@ -11,6 +11,7 @@
 #include <linux/kernel.h>
 #include <linux/poll.h>
 #include <linux/fs.h>
+#include <linux/klog.h>
 
 #include <asm/uaccess.h>
 #include <asm/io.h>
@@ -21,27 +22,28 @@
 
 static int kmsg_open(struct inode * inode, struct file * file)
 {
-	return do_syslog(1,NULL,0);
+	return do_syslog(KLOG_OPEN, NULL, 0);
 }
 
 static int kmsg_release(struct inode * inode, struct file * file)
 {
-	(void) do_syslog(0,NULL,0);
+	(void) do_syslog(KLOG_CLOSE, NULL, 0);
 	return 0;
 }
 
 static ssize_t kmsg_read(struct file *file, char __user *buf,
 			 size_t count, loff_t *ppos)
 {
-	if ((file->f_flags & O_NONBLOCK) && !do_syslog(9, NULL, 0))
+	if ((file->f_flags & O_NONBLOCK)
+	    && !do_syslog(KLOG_GET_UNREAD, NULL, 0))
 		return -EAGAIN;
-	return do_syslog(2, buf, count);
+	return do_syslog(KLOG_READ, buf, count);
 }
 
 static unsigned int kmsg_poll(struct file *file, poll_table *wait)
 {
 	poll_wait(file, &log_wait, wait);
-	if (do_syslog(9, NULL, 0))
+	if (do_syslog(KLOG_GET_UNREAD, NULL, 0))
 		return POLLIN | POLLRDNORM;
 	return 0;
 }

--

Re: [patch 1/4] Add <linux/klog.h>

[Jan Engelhardt]

On Dec 24 2006 12:22, Zack Weinberg wrote:
>===================================================================
>--- linux-2.6.orig/fs/proc/kmsg.c	2006-12-23 08:55:17.000000000 -0800
>+++ linux-2.6/fs/proc/kmsg.c	2006-12-24 11:43:14.000000000 -0800
>@@ -11,6 +11,7 @@
> #include <linux/kernel.h>
> #include <linux/poll.h>
> #include <linux/fs.h>
>+#include <linux/klog.h>
> 
> #include <asm/uaccess.h>
> #include <asm/io.h>
>@@ -21,27 +22,28 @@
> 
> static int kmsg_open(struct inode * inode, struct file * file)
> {
>-	return do_syslog(1,NULL,0);
>+	return do_syslog(KLOG_OPEN, NULL, 0);
> }
> 
> static int kmsg_release(struct inode * inode, struct file * file)
> {
>-	(void) do_syslog(0,NULL,0);
>+	(void) do_syslog(KLOG_CLOSE, NULL, 0);
        ^^^^^^

I bet you can get rid of that in the process.


	-`J'
-- 

Re: [patch 1/4] Add <linux/klog.h>

[Vincent Legoll]

Zack Weinberg wrote:
> This patch introduces <linux/klog.h> with symbolic constants for the
> various sys_syslog() opcodes, and changes all in-kernel references to
> those opcodes to use the constants.  The header is added to the set of
> user/kernel interface headers.

[...]

> -/*
> - * Commands to do_syslog:
> +/**
> + * do_syslog - operate on the log of kernel messages
> + * @type: operation to perform
> + * @buf: user-space buffer to copy data into
> + * @len: number of bytes of space available at @buf
> + *
> + * See include/linux/klog.h for the command numbers passed as @type.
> + * The @buf and @len parameters are used with the above meanings for
> + * @type values %KLOG_READ, %KLOG_READ_HIST and %KLOG_READ_CLEAR_HIST.
> + * @len is reused with a different meaning, and @buf ignored, for
> + * %KLOG_SET_CONSOLE_LVL.  Both @buf and @len are ignored for all
> + * other @type values.
>   *
> - * 	0 -- Close the log.  Currently a NOP.
> - * 	1 -- Open the log. Currently a NOP.
> - * 	2 -- Read from the log.
> - * 	3 -- Read all messages remaining in the ring buffer.
> - * 	4 -- Read and clear all messages remaining in the ring buffer
> - * 	5 -- Clear ring buffer.
> - * 	6 -- Disable printk's to console
> - * 	7 -- Enable printk's to console
> - *	8 -- Set level of messages printed to console
> - *	9 -- Return number of unread characters in the log buffer
> - *     10 -- Return size of the log buffer
> + * On failure, returns a negative errno code.  On success, returns a
> + * nonnegative integer whose meaning depends on @type.
>   */
>  int do_syslog(int type, char __user *buf, int len)
>  {
> @@ -190,11 +192,11 @@

That part looks good to me, and the kernel-doc hunks from
"[patch 3/4] Refactor do_syslog interface"
too, are:

Acked-by: Vincent Legoll <vincent.legoll@gmail.com>

thanks for handling that.

-- 
Vincent Legoll

[patch 0/4] /proc/kmsg permissions, take three

[Zack Weinberg]

Here's a re-revised version of my patch set to allow klogd to drop
privileges and continue reading from /proc/kmsg (currently, even if klogd
has a legitimately opened fd on /proc/kmsg, it cannot read from it unless
it has CAP_SYS_ADMIN asserted).  SELinux's pickier and finer-grained
privilege rules for /proc/kmsg are unchanged.

The major change from the previous patchset
[q.v. http://comments.gmane.org/gmane.linux.kernel/466034 ] is that,
as Arjan van de Ven requested, the new header linux/klog.h contains only
userspace-visible definitions (the constants for sys_syslog()).  Thanks to
Alexey Dobriyan for telling me the proper place to put the KLOGSEC_*
constants (now renamed LSM_KLOG_* in keeping with other such constants).
They have also been rediffed versus yesterday's git.  They should be
applied in sequence; each step compiles, and the complete set has been
booted and tested to work as intended.

Any comments, as usual, appreciated.  I would very much like to see this
in 2.6.20.

zw

[patch 1/4] Add <linux/klog.h>

[Zack Weinberg]

[-- Attachment #1: add_klog_h.diff --]
[-- Type: text/plain, Size: 5835 bytes --]

This patch introduces <linux/klog.h> with symbolic constants for the
various sys_syslog() opcodes, and changes all in-kernel references to
those opcodes to use the constants.  The header is added to the set of
user/kernel interface headers.  (Unlike the previous revision of this
patch series, no kernel-private additions to this file are contemplated.)

zw

Index: linux-2.6/include/linux/Kbuild
===================================================================
--- linux-2.6.orig/include/linux/Kbuild	2006-12-13 15:58:13.000000000 -0800
+++ linux-2.6/include/linux/Kbuild	2006-12-13 16:06:57.000000000 -0800
@@ -100,6 +100,7 @@
 header-y += ixjuser.h
 header-y += jffs2.h
 header-y += keyctl.h
+header-y += klog.h
 header-y += limits.h
 header-y += lock_dlm_plock.h
 header-y += magic.h
Index: linux-2.6/include/linux/klog.h
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6/include/linux/klog.h	2006-12-13 16:06:22.000000000 -0800
@@ -0,0 +1,26 @@
+#ifndef _LINUX_KLOG_H
+#define _LINUX_KLOG_H
+
+/*
+ * Constants for the first argument to the syslog() system call
+ * (aka klogctl()).  These numbers are part of the user space ABI!
+ */
+enum {
+	KLOG_CLOSE           =  0, /* close log */
+	KLOG_OPEN            =  1, /* open log */
+	KLOG_READ            =  2, /* read from log (klogd) */
+
+	KLOG_READ_HIST       =  3, /* read history of log messages (dmesg) */
+	KLOG_READ_CLEAR_HIST =  4, /* read and clear history */
+	KLOG_CLEAR_HIST      =  5, /* just clear history */
+
+	KLOG_DISABLE_CONSOLE =  6, /* disable printk to console */
+	KLOG_ENABLE_CONSOLE  =  7, /* enable printk to console */
+	KLOG_SET_CONSOLE_LVL =  8, /* set minimum severity of messages to be
+				    * printed to console */
+
+	KLOG_GET_UNREAD      =  9, /* return number of unread characters */
+	KLOG_GET_SIZE        = 10  /* return size of log buffer */
+};
+
+#endif /* klog.h */
Index: linux-2.6/kernel/printk.c
===================================================================
--- linux-2.6.orig/kernel/printk.c	2006-12-13 15:58:16.000000000 -0800
+++ linux-2.6/kernel/printk.c	2006-12-13 16:06:22.000000000 -0800
@@ -32,6 +32,7 @@
 #include <linux/bootmem.h>
 #include <linux/syscalls.h>
 #include <linux/jiffies.h>
+#include <linux/klog.h>
 
 #include <asm/uaccess.h>
 
@@ -163,21 +164,7 @@
 
 __setup("log_buf_len=", log_buf_len_setup);
 
-/*
- * Commands to do_syslog:
- *
- * 	0 -- Close the log.  Currently a NOP.
- * 	1 -- Open the log. Currently a NOP.
- * 	2 -- Read from the log.
- * 	3 -- Read all messages remaining in the ring buffer.
- * 	4 -- Read and clear all messages remaining in the ring buffer
- * 	5 -- Clear ring buffer.
- * 	6 -- Disable printk's to console
- * 	7 -- Enable printk's to console
- *	8 -- Set level of messages printed to console
- *	9 -- Return number of unread characters in the log buffer
- *     10 -- Return size of the log buffer
- */
+/* See linux/klog.h for the command numbers passed as the first argument.  */
 int do_syslog(int type, char __user *buf, int len)
 {
 	unsigned long i, j, limit, count;
@@ -190,11 +177,11 @@
 		return error;
 
 	switch (type) {
-	case 0:		/* Close log */
+	case KLOG_CLOSE:
 		break;
-	case 1:		/* Open log */
+	case KLOG_OPEN:
 		break;
-	case 2:		/* Read from log */
+	case KLOG_READ:
 		error = -EINVAL;
 		if (!buf || len < 0)
 			goto out;
@@ -225,10 +212,10 @@
 		if (!error)
 			error = i;
 		break;
-	case 4:		/* Read/clear last kernel messages */
+	case KLOG_READ_CLEAR_HIST:
 		do_clear = 1;
 		/* FALL THRU */
-	case 3:		/* Read last kernel messages */
+	case KLOG_READ_HIST:
 		error = -EINVAL;
 		if (!buf || len < 0)
 			goto out;
@@ -281,16 +268,16 @@
 			}
 		}
 		break;
-	case 5:		/* Clear ring buffer */
+	case KLOG_CLEAR_HIST:
 		logged_chars = 0;
 		break;
-	case 6:		/* Disable logging to console */
+	case KLOG_DISABLE_CONSOLE:
 		console_loglevel = minimum_console_loglevel;
 		break;
-	case 7:		/* Enable logging to console */
+	case KLOG_ENABLE_CONSOLE:
 		console_loglevel = default_console_loglevel;
 		break;
-	case 8:		/* Set level of messages printed to console */
+	case KLOG_SET_CONSOLE_LVL:
 		error = -EINVAL;
 		if (len < 1 || len > 8)
 			goto out;
@@ -299,10 +286,10 @@
 		console_loglevel = len;
 		error = 0;
 		break;
-	case 9:		/* Number of chars in the log buffer */
+	case KLOG_GET_UNREAD:
 		error = log_end - log_start;
 		break;
-	case 10:	/* Size of the log buffer */
+	case KLOG_GET_SIZE:
 		error = log_buf_len;
 		break;
 	default:
Index: linux-2.6/fs/proc/kmsg.c
===================================================================
--- linux-2.6.orig/fs/proc/kmsg.c	2006-12-13 15:53:29.000000000 -0800
+++ linux-2.6/fs/proc/kmsg.c	2006-12-13 16:04:46.000000000 -0800
@@ -11,6 +11,7 @@
 #include <linux/kernel.h>
 #include <linux/poll.h>
 #include <linux/fs.h>
+#include <linux/klog.h>
 
 #include <asm/uaccess.h>
 #include <asm/io.h>
@@ -21,27 +22,28 @@
 
 static int kmsg_open(struct inode * inode, struct file * file)
 {
-	return do_syslog(1,NULL,0);
+	return do_syslog(KLOG_OPEN,NULL,0);
 }
 
 static int kmsg_release(struct inode * inode, struct file * file)
 {
-	(void) do_syslog(0,NULL,0);
+	(void) do_syslog(KLOG_CLOSE,NULL,0);
 	return 0;
 }
 
 static ssize_t kmsg_read(struct file *file, char __user *buf,
 			 size_t count, loff_t *ppos)
 {
-	if ((file->f_flags & O_NONBLOCK) && !do_syslog(9, NULL, 0))
+	if ((file->f_flags & O_NONBLOCK)
+	    && !do_syslog(KLOG_GET_UNREAD, NULL, 0))
 		return -EAGAIN;
-	return do_syslog(2, buf, count);
+	return do_syslog(KLOG_READ, buf, count);
 }
 
 static unsigned int kmsg_poll(struct file *file, poll_table *wait)
 {
 	poll_wait(file, &log_wait, wait);
-	if (do_syslog(9, NULL, 0))
+	if (do_syslog(KLOG_GET_UNREAD, NULL, 0))
 		return POLLIN | POLLRDNORM;
 	return 0;
 }

--

Re: [patch 1/4] Add <linux/klog.h>

[Randy Dunlap]

On Thu, 14 Dec 2006 16:16:40 -0800 Zack Weinberg wrote:

> This patch introduces <linux/klog.h> with symbolic constants for the
> various sys_syslog() opcodes, and changes all in-kernel references to
> those opcodes to use the constants.  The header is added to the set of
> user/kernel interface headers.  (Unlike the previous revision of this
> patch series, no kernel-private additions to this file are contemplated.)

Hi Zack,

This patch looks good except for one nit:

> --- linux-2.6.orig/fs/proc/kmsg.c	2006-12-13 15:53:29.000000000 -0800
> +++ linux-2.6/fs/proc/kmsg.c	2006-12-13 16:04:46.000000000 -0800
> @@ -21,27 +22,28 @@
>  
>  static int kmsg_open(struct inode * inode, struct file * file)
>  {
> -	return do_syslog(1,NULL,0);
> +	return do_syslog(KLOG_OPEN,NULL,0);
>  }
>  
>  static int kmsg_release(struct inode * inode, struct file * file)
>  {
> -	(void) do_syslog(0,NULL,0);
> +	(void) do_syslog(KLOG_CLOSE,NULL,0);
>  	return 0;
>  }

Please use a space after the commas (even though you just left it
as it already was).

---
~Randy

Re: [patch 1/4] Add <linux/klog.h>

[Zack Weinberg]

On 12/14/06, Randy Dunlap <randy.dunlap@oracle.com> wrote:
> > -     (void) do_syslog(0,NULL,0);
> > +     (void) do_syslog(KLOG_CLOSE,NULL,0);
>
> Please use a space after the commas (even though you just left it
> as it already was).

Will change for the next revision.

zw

[patch 0/4] Syslog permissions, revised

[Zack Weinberg]

This patchset revises my attempt from last week to allow running klogd
unprivileged without a root shim.  I believe I have addressed all
outstanding objections: in particular, the privilege model enforced by
SELinux is unchanged (you have to have system__syslog_mod to read
/proc/kmsg).  I have also included some nice refactorings (symbolic
constants for sys_syslog opcodes, that sort of thing) and a few
bugfixes (minor and unlikely to affect any live application, but
still).

I hope that this can be considered for 2.6.19; it is low risk in my
opinion and it would be nice to get this functionality into the hands
of the distributors sooner.

zw

[patch 1/4] Add <linux/klog.h>

[Zack Weinberg]

[-- Attachment #1: add_klog_h.diff --]
[-- Type: text/plain, Size: 5846 bytes --]

This patch introduces <linux/klog.h> with symbolic constants for the
various sys_syslog() opcodes, and changes all in-kernel references to
those opcodes to use the constants.  The header is added to the set of
user/kernel interface headers; there is no #ifdef __KERNEL__ block in
it yet, but there will be in subsequent patches, so I put it in as an
'unifdef' header.

zw

Index: linux-2.6/include/linux/Kbuild
===================================================================
--- linux-2.6.orig/include/linux/Kbuild	2006-11-10 13:36:58.000000000 -0800
+++ linux-2.6/include/linux/Kbuild	2006-11-10 13:37:13.000000000 -0800
@@ -253,6 +253,7 @@
 unifdef-y += kernelcapi.h
 unifdef-y += kernel.h
 unifdef-y += keyboard.h
+unifdef-y += klog.h
 unifdef-y += llc.h
 unifdef-y += loop.h
 unifdef-y += lp.h
Index: linux-2.6/include/linux/klog.h
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6/include/linux/klog.h	2006-11-10 14:16:35.000000000 -0800
@@ -0,0 +1,26 @@
+#ifndef _LINUX_KLOG_H
+#define _LINUX_KLOG_H
+
+/*
+ * Constants for the first argument to the syslog() system call
+ * (aka klogctl()).  These numbers are part of the user space ABI!
+ */
+enum {
+	KLOG_CLOSE           =  0, /* close log */
+	KLOG_OPEN            =  1, /* open log */
+	KLOG_READ            =  2, /* read from log (klogd) */
+
+	KLOG_READ_HIST       =  3, /* read history of log messages (dmesg) */
+	KLOG_READ_CLEAR_HIST =  4, /* read and clear history */
+	KLOG_CLEAR_HIST      =  5, /* just clear history */
+
+	KLOG_DISABLE_CONSOLE =  6, /* disable printk to console */
+	KLOG_ENABLE_CONSOLE  =  7, /* enable printk to console */
+	KLOG_SET_CONSOLE_LVL =  8, /* set minimum severity of messages to be
+				    * printed to console */
+
+	KLOG_GET_UNREAD      =  9, /* return number of unread characters */
+	KLOG_GET_SIZE        = 10  /* return size of log buffer */
+};
+
+#endif /* klog.h */
Index: linux-2.6/kernel/printk.c
===================================================================
--- linux-2.6.orig/kernel/printk.c	2006-11-10 13:16:47.000000000 -0800
+++ linux-2.6/kernel/printk.c	2006-11-10 14:16:34.000000000 -0800
@@ -32,6 +32,7 @@
 #include <linux/bootmem.h>
 #include <linux/syscalls.h>
 #include <linux/jiffies.h>
+#include <linux/klog.h>
 
 #include <asm/uaccess.h>
 
@@ -165,21 +166,7 @@
 
 __setup("log_buf_len=", log_buf_len_setup);
 
-/*
- * Commands to do_syslog:
- *
- * 	0 -- Close the log.  Currently a NOP.
- * 	1 -- Open the log. Currently a NOP.
- * 	2 -- Read from the log.
- * 	3 -- Read all messages remaining in the ring buffer.
- * 	4 -- Read and clear all messages remaining in the ring buffer
- * 	5 -- Clear ring buffer.
- * 	6 -- Disable printk's to console
- * 	7 -- Enable printk's to console
- *	8 -- Set level of messages printed to console
- *	9 -- Return number of unread characters in the log buffer
- *     10 -- Return size of the log buffer
- */
+/* See linux/klog.h for the command numbers passed as the first argument.  */
 int do_syslog(int type, char __user *buf, int len)
 {
 	unsigned long i, j, limit, count;
@@ -192,11 +179,11 @@
 		return error;
 
 	switch (type) {
-	case 0:		/* Close log */
+	case KLOG_CLOSE:
 		break;
-	case 1:		/* Open log */
+	case KLOG_OPEN:
 		break;
-	case 2:		/* Read from log */
+	case KLOG_READ:
 		error = -EINVAL;
 		if (!buf || len < 0)
 			goto out;
@@ -227,10 +214,10 @@
 		if (!error)
 			error = i;
 		break;
-	case 4:		/* Read/clear last kernel messages */
+	case KLOG_READ_CLEAR_HIST:
 		do_clear = 1;
 		/* FALL THRU */
-	case 3:		/* Read last kernel messages */
+	case KLOG_READ_HIST:
 		error = -EINVAL;
 		if (!buf || len < 0)
 			goto out;
@@ -283,16 +270,16 @@
 			}
 		}
 		break;
-	case 5:		/* Clear ring buffer */
+	case KLOG_CLEAR_HIST:
 		logged_chars = 0;
 		break;
-	case 6:		/* Disable logging to console */
+	case KLOG_DISABLE_CONSOLE:
 		console_loglevel = minimum_console_loglevel;
 		break;
-	case 7:		/* Enable logging to console */
+	case KLOG_ENABLE_CONSOLE:
 		console_loglevel = default_console_loglevel;
 		break;
-	case 8:		/* Set level of messages printed to console */
+	case KLOG_SET_CONSOLE_LVL:
 		error = -EINVAL;
 		if (len < 1 || len > 8)
 			goto out;
@@ -301,10 +288,10 @@
 		console_loglevel = len;
 		error = 0;
 		break;
-	case 9:		/* Number of chars in the log buffer */
+	case KLOG_GET_UNREAD:
 		error = log_end - log_start;
 		break;
-	case 10:	/* Size of the log buffer */
+	case KLOG_GET_SIZE:
 		error = log_buf_len;
 		break;
 	default:
Index: linux-2.6/fs/proc/kmsg.c
===================================================================
--- linux-2.6.orig/fs/proc/kmsg.c	2006-11-10 14:16:41.000000000 -0800
+++ linux-2.6/fs/proc/kmsg.c	2006-11-10 14:22:56.000000000 -0800
@@ -11,6 +11,7 @@
 #include <linux/kernel.h>
 #include <linux/poll.h>
 #include <linux/fs.h>
+#include <linux/klog.h>
 
 #include <asm/uaccess.h>
 #include <asm/io.h>
@@ -21,27 +22,28 @@
 
 static int kmsg_open(struct inode * inode, struct file * file)
 {
-	return do_syslog(1,NULL,0);
+	return do_syslog(KLOG_OPEN,NULL,0);
 }
 
 static int kmsg_release(struct inode * inode, struct file * file)
 {
-	(void) do_syslog(0,NULL,0);
+	(void) do_syslog(KLOG_CLOSE,NULL,0);
 	return 0;
 }
 
 static ssize_t kmsg_read(struct file *file, char __user *buf,
 			 size_t count, loff_t *ppos)
 {
-	if ((file->f_flags & O_NONBLOCK) && !do_syslog(9, NULL, 0))
+	if ((file->f_flags & O_NONBLOCK)
+	    && !do_syslog(KLOG_GET_UNREAD, NULL, 0))
 		return -EAGAIN;
-	return do_syslog(2, buf, count);
+	return do_syslog(KLOG_READ, buf, count);
 }
 
 static unsigned int kmsg_poll(struct file *file, poll_table *wait)
 {
 	poll_wait(file, &log_wait, wait);
-	if (do_syslog(9, NULL, 0))
+	if (do_syslog(KLOG_GET_UNREAD, NULL, 0))
 		return POLLIN | POLLRDNORM;
 	return 0;
 }

--