On Fri, Jul 08, 2011 at 12:21:27AM +0100, David Gilbert wrote:
On 5 July 2011 15:49, Dave Martin dave.martin@linaro.org wrote:
On Fri, Jul 1, 2011 at 6:10 PM, David Gilbert david.gilbert@linaro.org wrote:
[...]
My patch is having to test an arbitrary address in the commpage in init code to see if it's new enough to have the new helper that
Minor niggle: the address is in no way arbitrary. Although there's no corresponding C symbol, it's a well-known absolute address.
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. Introducing a VDSO interface will not automatically cause all software to stop using the binary interface.
How much of a problem that is in practice, I don't know.
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.
Cheers ---Dave