On Wed, Apr 09, 2014 at 12:33:58PM -0400, David Miller wrote: > From: Russell King - ARM Linux <[email protected]> > Date: Wed, 9 Apr 2014 17:15:55 +0100 > > > On Wed, Apr 09, 2014 at 12:09:26PM -0400, David Miller wrote: > >> From: Russell King - ARM Linux <[email protected]> > >> Date: Wed, 9 Apr 2014 11:01:50 +0100 > >> > >> > What has been proposed for uprobes is a uprobe specific function - > >> > flush_uprobe_xol_access() which is used after uprobes writes via the > >> > kmap_atomic() mapping of the page: > >> > > >> > + xol_page_kaddr = kmap_atomic(area->page); > >> > + > >> > + /* Initialize the slot */ > >> > + memcpy(xol_page_kaddr + (xol_vaddr & ~PAGE_MASK), > >> > + &uprobe->arch.ixol, > >> > + sizeof(uprobe->arch.ixol)); > >> > + > >> > + arch_uprobe_flush_xol_access(area->page, xol_vaddr, > >> > + xol_page_kaddr + (xol_vaddr & > >> > ~PAGE_MASK), > >> > + sizeof(uprobe->arch.ixol)); > >> > + > >> > + kunmap_atomic(xol_page_kaddr); > >> > > >> > Comments? > >> > >> ptrace() accesses (via __access_remote_vm()) already use an existing > >> helper function for these sorts of situations, in the form of > >> copy_{to,from}_user_page(). I would suggest that uprobes uses that > >> as well. > > > > Yes, I agree with you. > > > > I made that suggestion too (because it's really the same problem) > > but uprobes people are concerned that it's too much of an overhead: > > They should use it at first, then if there is a problem we can identify > exactly what can be optimized or needs to be, and expand the interface > as needed. > > Let's not optimize first.
I have forwarded your comments, thanks. -- FTTC broadband for 0.8mile line: now at 9.7Mbps down 460kbps up... slowly improving, and getting towards what was expected from it. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
