On 11/09/15 18:32, Julien Grall wrote: > On 11/09/15 18:00, Russell King - ARM Linux wrote: >> On Fri, Sep 11, 2015 at 05:25:59PM +0100, Julien Grall wrote: >>> + /* >>> + * Privcmd calls are issued by the userspace. We need to allow the >>> + * kernel to access the userspace memory before issuing the hypercall. >>> + */ >>> + uaccess_enable r4 >>> + >>> + /* r4 is loaded now as we use it as scratch register before */ >>> ldr r4, [sp, #4] >> >> As I mentioned in one of my previous mails, "ip" should be safe to use >> here - it's a caller-corrupted register, just like r0-r3 and lr. So, >> you could do: >> >> ldr r4, [sp, #4] >> + uaccess_enable ip > > The register ip (aka r12) is used to store the hypercall number. So we > can't reuse it as scratch register. > > The easiest one is r4. > >> >> which fractionally tightens the window. >> >> However, there's nothing actually wrong with your version - there's no >> way we could've got this far with sp pointing at userspace. >> >> I'm happy with either version, so: >> >> Acked-by: Russell King <rmk+ker...@arm.linux.org.uk> >> >> How do you want to handle the patch? I already have some other uaccess >> fixes queued up to send to Linus before the merge window closes.
Forgot to answer to this bits. I was thinking to ask Stefano carrying the patch in xentip. Although it won't go until rc1. I don't mind if it's going earlier in Linux/master. Regards, -- Julien Grall -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
