[Bug libc/16919] recvmsg standard compliance

["sickmind at i2pmail dot org" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=16919

--- Comment #4 from Lana Black <sickmind at i2pmail dot org> ---
(In reply to joseph@codesourcery.com from comment #3)
> Padding should use __glibc_reserved* names.
> 
> To make part of an existing field into padding like this, the following 
> need to be true:
> 
> * If the kernel reads the field, all existing kernel versions supported by 
> glibc already treat that part of the field as padding, so they will not 
> misinterpret uninitialized data there.  If that's not the case, glibc 
> needs to initialize the padding appropriately before passing the structure 
> to the kernel.
> 
> * If the kernel writes the field, it gives an overflow error rather than 
> treating that part of the field as something to which a significant value 
> may be written.  If it treats it as significant, glibc needs to check in 
> userspace for overflow and set an error in that case (just as the 
> asm-generic implementations of 32-bit stat functions do).
> 
> * If user programs write the field, so that for old programs the high bits 
> are significant but for new programs the high bits are padding, symbol 
> versioning needs to be used to avoid misinterpreting values written there 
> by existing binaries.
> 
> * If user programs read the field, so that old programs may interpret high 
> bits written by glibc or the kernel as significant, those bits need 
> initializing appropriately for the existing programs.

Thanks for the tip. I should create appropriate __libc_{sendmsg,recvmsg}
functions for that, am I right?

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