On Fri, 8 Jul 2011, Dave Martin wrote:
On Fri, Jul 08, 2011 at 12:21:27AM +0100, David Gilbert wrote:
Nicolas just added; Richard's argument is that if it was actually a VDSO I'd just have linked against a symbol and if the symbol wasn't there then I would have got a fairly normal linker error - I wouldn't have needed any special code; and to be honest I think that would also solve the problem that accessing that wacky address is also a pain for things like qemu because we're going to have to intercept that read.
Note that pre-existing code already calls into the vectors page.
Right, qemu must be intercepting it already. The kernel helpers located at a fixed address in the vector page have been around for more than 6 years.
This doesn't necessarily mean that adding a VDSO interface is bad, but it does mean the existing interface can't easily be changed or removed.
Agreed. There is nothing preventing the addition of a VDSO, but I've yet to see a convincing argument for spending time adding it.
Nicolas