On Aug 23, 2007, at 9:14 AM, Jernej Azarija wrote:
Hello,
I've encountered this issue too. Specifically, when a lot of calls
to printf() have been made, the output looks messy. eg :
printf("foo\n");
printf("bar\n");
Ends up written in system.log as :
fobaro
(just a banal example).
Amazing.
One of the most common problems faced when programming in the kernel
is use of “standard” functions—things like printf or bcopy. Many
commonly used standard C library functions are implemented in the
kernel. In order to use them, however, you need to include the
appropriate prototypes, which may be different from the user space
prototypes for those functions, and which generally have different
names when included from kernel code.
In general, any non–I/O Kit header that you can safely include in the
kernel is located in xnu/bsd/sys or xnu/osfmk/mach, although there
are a few specialized headers in other places like libkern and libsa.
Normal headers (those in /usr/include) cannot be used in the kernel
(or rather, cannot be used 'properly').
If the standard C function you are trying to use is not in one of the
following files, chances are the function is not supported for use
within the kernel, and you need to implement your code in another way:
<sys/systm.h> (printf can be used with this)
<sys/buf.h> (buffer cache functions like bread)
<sys/dirent.h> (directory entries)
<sys/errno.h> (Error numbers)
<sys.kernel.h> (kernel special variables)
<sys/lock.h> (spinlocks)
<sys/malloc.h> (malloc)
<sys/queue.h> (queues)
<sys/rand.h> (random generation numbers)
<sys/systm.h> (bzero, bcopy.. etc)
<sys/system.h> (timeout, untimeout)
<sys/time.h> (time functions)
<sys/types.h> <mach/mach_types.h> (standard type declarations)
<sys/ucred.h> (user credentials)
<sys/utsname.h> (os and system information)
I checked printf() implementation and it seems that loocking *is*
handled correctly so I'm really wondering what's the problem behind
it.
-----Original Message-----
From: darwin-kernel-bounces+jernej.azarija=hermes-
email@hidden on behalf of Jeremy Pereira
Sent: Thu 8/23/2007 9:35 AM
To: JanakiRam
Cc: email@hidden
Subject: Re: printf logs are not getting printed properly on
system.log
On 23 Aug 2007, at 06:05, JanakiRam wrote:
> Hi ALL,
>
> I'm newbie to this kernel prorgamming. Please clarify my
> following query.
>
> I'm using printf for logging messages from my kext. One
> observation is all my logs are not getting printed when i start my
> kext using kextload. Its not consitent , how many logs are going
> to get printed every time i load the kext.
>
> Please help me to solve this. Thanks in Advance.
I've seen the same problem. I assumed it was because of overrunning
some buffer somewhere i.e. producing too much output for the kernel
logging system to cope with.
"I know that fewer people are won over by the written word than by
the spoken word and that every great movement on this earth owes its
growth to great speakers and not to great writers."
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