RE: remove kernel_setsockopt and kernel_getsockopt v2

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



From: Christoph Hellwig
> Sent: 20 May 2020 20:55
> 
> this series removes the kernel_setsockopt and kernel_getsockopt
> functions, and instead switches their users to small functions that
> implement setting (or in one case getting) a sockopt directly using
> a normal kernel function call with type safety and all the other
> benefits of not having a function call.
> 
> In some cases these functions seem pretty heavy handed as they do
> a lock_sock even for just setting a single variable, but this mirrors
> the real setsockopt implementation unlike a few drivers that just set
> set the fields directly.

How much does this increase the kernel code by?

You are also replicating a lot of code making it more
difficult to maintain.

I don't think the performance of an socket option code
really matters - it is usually done once when a socket
is initialised and the other costs of establishing a
connection will dominate.

Pulling the user copies outside the [gs]etsocksopt switch
statement not only reduces the code size (source and object)
and trivially allows kernel_[sg]sockopt() to me added to
the list of socket calls.

It probably isn't possible to pull the usercopies right
out into the syscall wrapper because of some broken
requests.

I worried about whether getsockopt() should read the entire
user buffer first. SCTP needs the some of it often (including a
sockaddr_storage in one case), TCP needs it once.
However the cost of reading a few words is small, and a big
buffer probably needs setting to avoid leaking kernel
memory if the structure has holes or fields that don't get set.
Reading from userspace solves both issues.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)




[Index of Archives]     [Linux SCSI]     [Kernel Newbies]     [Linux SCSI Target Infrastructure]     [Share Photos]     [IDE]     [Security]     [Git]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Linux ATA RAID]     [Linux IIO]     [Device Mapper]

  Powered by Linux