RE: Simple question about getting stack size

["Curran, Dominic" <dcurran@xxxxxx>]

Yes, this is just for debug purposes.

I added the code to my module, but it wouldn't compile:

# make
make -C /lib/modules/2.6.5-1.358/build SUBDIRS=/test/mydriver modules
make[1]: Entering directory `/lib/modules/2.6.5-1.358/build'
  CC [M]  /test/mydriver/igg.o
/test/mydriver/igg.c: In function `igg_ioctl':
/test/mydriver/igg.c:2106: warning: asm operand 1 probably doesn't match
constraints
/test/mydriver/igg.c:2106: error: impossible constraint in `asm'
/test/mydriver/igg.c:2104: warning: `esp' might be used uninitialized in
this function
make[2]: *** [/test/mydriver/igg.o] Error 1
make[1]: *** [/test/mydriver] Error 2
make[1]: Leaving directory `/lib/modules/2.6.5-1.358/build'
make: *** [default] Error 2
#

The 2106 lines is the __asm__ line.

I see that there are other lines of code like this is the kernel, so I'm
stumped as to why this won't compile ?

I'm using the kernels Kbuild system so I would have thought that it
would have all the right compile flags set. 

Any help appreciated.
Thanks
dom


-----Original Message-----
From: Arjan van de Ven [mailto:arjan@xxxxxxxxxxxxx] 
Sent: Sunday, February 27, 2005 5:12 AM
To: Curran, Dominic
Cc: kernelnewbies@xxxxxxxxxxxx
Subject: Re: Simple question about getting stack size


On Sat, 2005-02-26 at 20:28 -0600, Curran, Dominic wrote:
> Hi
> 
> Trying to do something very simple and failing miserably...
> 
> I want to dump out the amount of stack size I have left at different 
> points in my LKM driver.

as a debugging aid I assume


> In order to do this I believe I need to know the value of 'current' 
> and 'esp'.

Just copy the following code into yours (your module is gpl so that you
can copy such things I assume):


58 #ifdef CONFIG_DEBUG_STACKOVERFLOW
59         /* Debugging check for stack overflow: is there less than 1KB
free? */
60         {
61                 long esp;
62 
63                 __asm__ __volatile__("andl %%esp,%0" :
64                                         "=r" (esp) : "" (THREAD_SIZE
- 1));
65                 if (unlikely(esp < (sizeof(struct thread_info) +
STACK_WARN))) {
66                         printk("do_IRQ: stack overflow: %ld\n",
67                                 esp - sizeof(struct thread_info));
68                         dump_stack();
69                 }
70         }
71 #endif




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