adding 32 bit compatibility layer in custom kernel module

[Anish Kumar]

> On Jan 3, 2017, at 10:03 PM, Pradeepa Kumar <cdpradeepa at gmail.com> wrote:
> 
> Please see inline below
> 
>> On Wed, Jan 4, 2017 at 11:07 AM, Anish Kumar <anish198519851985 at gmail.com> wrote:
>> 
>> 
>>> On Jan 3, 2017, at 8:04 PM, Pradeepa Kumar <cdpradeepa at gmail.com> wrote:
>>> 
>>> Hi experts
>>> 
>>> down vote
>>> favorite
>>> in my 64 bit kernel, I have a custom kernel module providing new protocol and providing socket system calls.
>>> 
>>> it works fine when 64 bit app runs.
>>> 
>>> i am seeing issues when 32 bit app runs (for exp recvmsg() call does not work if msg has cmsghdrs as struct size of cmsghdr is different in 32 bit and 64 bit).
>>> 
>>> This is because my custom kernel module does not have 32 bit compatibility layer ( but linux kernel has this in compat.c etc).
>>> 
>>> is it simple to add compatibility layer to my custom kernel module
>>> 
>>> All you have to do is add compat_ioctl call to your driver.
> my kernel module provides recvmsg() but i dont see any 'compat_recvmsg' in struct proto_ops.

Try to wrap your text in 80 characters.

Your application is crashing? Right?
Have you figured where it is crashing exactly?

I understood that your application is crashing as 
It not able to function with 64 bit kernel.

This happens because of the data being passed
to kernel is not in the right format. You need to
look at what you are passing to the driver and
if needed write the compat_ioctl callback in your
driver fops.
> had there been  'compat_recvmsg' it would have been possible for me to define recvmsg() for 32 bit apps.
> please let me know if i am missing anything
> 
>>> how do i do this (any links ?)
>>> 
>>> You can see many drivers supports compat call.
>>> Thanks
>>> 
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> 
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