targets of function pointer invocations

targets of function pointer invocations

[Firstname Lastname]

Hi all,

The lines 522-523 in function do_acct_process in file kernel/acct.c in version 2.6.26.3 are:

 file->f_op->write(file, (char *)&ac,sizeof(acct_t), &file->f_pos);

What are the full set of targets of this function pointer invocation and how can one be sure, by examining the code, that this is in fact the complete set?

Thanks.

SKB



      

Re: targets of function pointer invocations

[Randy Dunlap]

On Sat, 30 Aug 2008 00:12:12 -0700 (PDT) Firstname Lastname wrote:

> Hi all,
> 
> The lines 522-523 in function do_acct_process in file kernel/acct.c in version 2.6.26.3 are:
> 
>  file->f_op->write(file, (char *)&ac,sizeof(acct_t), &file->f_pos);
> 
> What are the full set of targets of this function pointer invocation and how can one be sure, by examining the code, that this is in fact the complete set?

If I understand your question, you want to know what are the ->write()
function parameters and how does one determine them?

'file' is struct file, found in include/linux/fs.h.
'f_op' is struct file_operations, in the same file.
'write' is defined in struct file_operations as:

	ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);

4 typed parameters, returning ssize_t.

Is that what you meant?

---
~Randy
Linux Plumbers Conference, 17-19 September 2008, Portland, Oregon USA
http://linuxplumbersconf.org/

Re: targets of function pointer invocations

[Jeremy Fitzhardinge]

Randy Dunlap wrote:
> On Sat, 30 Aug 2008 00:12:12 -0700 (PDT) Firstname Lastname wrote:
>
>   
>> Hi all,
>>
>> The lines 522-523 in function do_acct_process in file kernel/acct.c in version 2.6.26.3 are:
>>
>>  file->f_op->write(file, (char *)&ac,sizeof(acct_t), &file->f_pos);
>>
>> What are the full set of targets of this function pointer invocation and how can one be sure, by examining the code, that this is in fact the complete set?
>>     
>
> If I understand your question, you want to know what are the ->write()
> function parameters and how does one determine them?
>
> 'file' is struct file, found in include/linux/fs.h.
> 'f_op' is struct file_operations, in the same file.
> 'write' is defined in struct file_operations as:
>
> 	ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
>
> 4 typed parameters, returning ssize_t.
>
> Is that what you meant?
>   

Actually, I think OP is asking what's the complete set of functions
->write can point to.  You can look for all the in-tree assignments to
f_ops (or all the struct file_ops) to get the in-kernel estimate.  But
any out of tree module could also install file_ops.write, so you can't
be exhaustive.

    J