Static vdso on other architectures

[Joseph Myers]

On Sun, 2 Dec 2018, Rafael Avila de Espindola wrote:

> I have enabled static vdso on every architecture I can test it. That is,
> on every architecture in the gcc farm that can build glibc.

Having such a series of patches for different architectures suggests to me 
that there is too much in architecture-specific code, and more of the vDSO 
handling should be in architecture-independent code in glibc - in general 
in recent years we've been trying to move more things to 
architecture-independent code, with a minimum of architecture-specific 
overrides where actually needed.

Could you describe what is common and what is different between 
architecture vDSO support in the Linux kernel.  For example:

* Do all architectures support a vDSO at all?

* Are there functions that are present in the vDSO for all architectures, 
or is the set of functions completely architecture-specific?

* For the syscall interface, we have the asm-generic interface that 
defines the preferred set of syscalls that all new architectures will use.  
Is there anything like that for the vDSO - a preferred vDSO interface we 
know all new Linux kernel architectures will use?  If there is, it would 
indicate what should be the default in architecture-independent code in 
glibc, and what should be considered a deviation needing an 
architecture-specific override.

-- 
Joseph S. Myers
joseph@codesourcery.com