Re: [PATCH] x86-64: Clean up vdso/kernel shared variables

["H. Peter Anvin" <hpa@kernel.org>]

On 03/29/2011 07:29 AM, Andy Lutomirski wrote:
> Variables that are shared between the vdso and the kernel are
> currently a bit of a mess.  They are each defined with their own
> magic, they are accessed differently in the kernel, the vsyscall page,
> and the vdso, and one of them (vsyscall_clock) doesn't even really
> exist.
> 
> This changes them all to use a common mechanism.  All of them are
> delcared in vvar.h with a fixed address (validated by the linker
> script).  In the kernel (as before), they look like ordinary
> read-write variables.  In the vsyscall page and the vdso, they are
> accessed through a new macro VVAR, which gives read-only access.
> 
> The vdso is now loaded verbatim into memory without any fixups.  As a
> side bonus, access from the vdso is faster because a level of
> indirection is removed.
> 
> Signed-off-by: Andy Lutomirski <luto@mit.edu>

How does this deal with variables which really should be shared with
multiple vdsos (in particular the 32-bit vdso and the 64-bit vdso)?
Part of me is wondering if it might not be simpler to put them all into
a structure?

	-hpa