function Named

function Named

[raja]

hi,
    Is there any way to get the function address by only knowing the 
function Name
thanking you,

Re: function Named

[Richard B. Johnson]

On Thu, 7 Jul 2005, raja wrote:

> hi,
>    Is there any way to get the function address by only knowing the
> function Name
> thanking you,
> -

 	printf("%p\n", function());   // User code
 	printk("%p\n", function());   // Kernel code

This gives you the offset in virtual address-space. Inside the
kernel, one can obtain the physical address. User-code code
can't find out the physical address in any direct way.


Cheers,
Dick Johnson
Penguin : Linux version 2.6.12 on an i686 machine (5537.79 BogoMips).
  Notice : All mail here is now cached for review by Dictator Bush.
                  98.36% of all statistics are fiction.

Re: function Named

[Jens Axboe]

On Thu, Jul 07 2005, Richard B. Johnson wrote:
> On Thu, 7 Jul 2005, raja wrote:
> 
> >hi,
> >   Is there any way to get the function address by only knowing the
> >function Name
> >thanking you,
> >-
> 
> 	printf("%p\n", function());   // User code
> 	printk("%p\n", function());   // Kernel code

Yup that'll work fine, provided 'function' takes no arguments and
returns its own address.

-- 
Jens Axboe

Re: function Named

[Richard B. Johnson]

On Thu, 7 Jul 2005, Jens Axboe wrote:

> On Thu, Jul 07 2005, Richard B. Johnson wrote:
>> On Thu, 7 Jul 2005, raja wrote:
>>
>>> hi,
>>>   Is there any way to get the function address by only knowing the
>>> function Name
>>> thanking you,
>>> -
>>
>> 	printf("%p\n", function());   // User code
>> 	printk("%p\n", function());   // Kernel code
>
> Yup that'll work fine, provided 'function' takes no arguments and
> returns its own address.

Sorry meant..........

 	printf("%p\n", function);   // User code
>

I wanted to show that 'function' was a `function()`.

> -- 
> Jens Axboe
>
>

Cheers,
Dick Johnson
Penguin : Linux version 2.6.12 on an i686 machine (5537.79 BogoMips).
  Notice : All mail here is now cached for review by Dictator Bush.
                  98.36% of all statistics are fiction.

Re: function Named

[Paulo Marques]

raja wrote:
> hi,
>    Is there any way to get the function address by only knowing the 
> function Name

See "kallsyms_lookup_name" in include/linux/kallsyms.h (implemented in 
kernel/kallsyms.c).

Beware:

  - CONFIG_KALLSYMS might be undefined. In that case it always returns 0

  - the function returns the address of *any* known symbol, not just 
functions (this can be easily improved to also return the symbol type)

  - the function is extremely inefficient, as it does a linear search 
over all the symbols. kallsyms is optimized to work the other way 
around: get the name from the address.

-- 
Paulo Marques - www.grupopie.com

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