On Thu, Mar 19, 2015 at 06:17:46PM +0100, Denys Vlasenko wrote: > PER_CPU_VAR(kernel_stack) was set up in a way where it points > five stack slots below the top of stack. > > Presumably, it was done to avoid one "sub $5*8,%rsp" > in syscall/sysenter code paths, where iret frame needs to be > created by hand. > > Ironically, none of them benefits from this optimization, > since all of them need to allocate additional data on stack > (struct pt_regs), so they still have to perform subtraction. > > This patch eliminates KERNEL_STACK_OFFSET. > > PER_CPU_VAR(kernel_stack) now points directly to top of stack. > pt_regs allocations are adjusted to allocate iret frame as well. > Hopefully we can merge it later with 32-bit specific > PER_CPU_VAR(cpu_current_top_of_stack) variable... > > Net result in generated code is that constants in several insns > are changed. > > This change is necessary for changing struct pt_regs creation > in SYSCALL64 code path from MOV to PUSH instructions. > > Signed-off-by: Denys Vlasenko <[email protected]> > CC: Linus Torvalds <[email protected]> > CC: Steven Rostedt <[email protected]> > CC: Ingo Molnar <[email protected]> > CC: Borislav Petkov <[email protected]> > CC: "H. Peter Anvin" <[email protected]> > CC: Andy Lutomirski <[email protected]> > CC: Oleg Nesterov <[email protected]> > CC: Frederic Weisbecker <[email protected]> > CC: Alexei Starovoitov <[email protected]> > CC: Will Drewry <[email protected]> > CC: Kees Cook <[email protected]> > CC: [email protected] > CC: [email protected]
Acked-by: Borislav Petkov <[email protected]> -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. -- -- 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/
