On Fri, Nov 24, 2017 at 06:23:41PM +0100, Ingo Molnar wrote: > From: Andy Lutomirski <l...@kernel.org> > > Historically, IDT entries from usermode have always gone directly > to the running task's kernel stack. Rearrange it so that we enter on > a percpu trampoline stack and then manually switch to the task's stack. > This touches a couple of extra cachelines, but it gives us a chance > to run some code before we touch the kernel stack. > > The asm isn't exactly beautiful, but I think that fully refactoring > it can wait. > > Signed-off-by: Andy Lutomirski <l...@kernel.org> > Signed-off-by: Thomas Gleixner <t...@linutronix.de>
I think you mean Reviewed-by: here. The following patches have it too. > Cc: Borislav Petkov <bpet...@suse.de> > Cc: Brian Gerst <brge...@gmail.com> > Cc: Dave Hansen <dave.han...@intel.com> > Cc: Josh Poimboeuf <jpoim...@redhat.com> > Cc: Linus Torvalds <torva...@linux-foundation.org> > Cc: Peter Zijlstra <pet...@infradead.org> > Link: > https://lkml.kernel.org/r/fa3958723a1a85baeaf309c735b775841205800e.1511497875.git.l...@kernel.org > Signed-off-by: Ingo Molnar <mi...@kernel.org> > --- > arch/x86/entry/entry_64.S | 67 > ++++++++++++++++++++++++++++++---------- > arch/x86/entry/entry_64_compat.S | 5 ++- > arch/x86/include/asm/switch_to.h | 2 +- > arch/x86/include/asm/traps.h | 1 - > arch/x86/kernel/cpu/common.c | 6 ++-- > arch/x86/kernel/traps.c | 18 +++++------ > 6 files changed, 68 insertions(+), 31 deletions(-) ... > diff --git a/arch/x86/include/asm/switch_to.h > b/arch/x86/include/asm/switch_to.h > index 8c6bd6863db9..a6796ac8d311 100644 > --- a/arch/x86/include/asm/switch_to.h > +++ b/arch/x86/include/asm/switch_to.h > @@ -93,7 +93,7 @@ static inline void update_sp0(struct task_struct *task) > #ifdef CONFIG_X86_32 > load_sp0(task->thread.sp0); > #else > - load_sp0(task_top_of_stack(task)); > + /* On x86_64, sp0 always points to the entry trampoline stack. */ > #endif You can put this comment to the one ontop and remove the #else. ifdeffery is always ugly and the less, the better. ... > -asmlinkage __visible notrace struct pt_regs *sync_regs(struct pt_regs *eregs) > +asmlinkage __visible notrace > +struct pt_regs *sync_regs(struct pt_regs *eregs) > { > - struct pt_regs *regs = task_pt_regs(current); > + struct pt_regs *regs = (struct pt_regs > *)this_cpu_read(cpu_current_top_of_stack) - 1; > *regs = *eregs; > return regs; > } > @@ -630,13 +630,13 @@ struct bad_iret_stack *fixup_bad_iret(struct > bad_iret_stack *s) > /* > * This is called from entry_64.S early in handling a fault > * caused by a bad iret to user mode. To handle the fault > - * correctly, we want move our stack frame to task_pt_regs > - * and we want to pretend that the exception came from the > - * iret target. > + * correctly, we want move our stack frame to where it would " ... we want to move... " > + * be had we entered directly on the entry stack (rather than > + * just below the IRET frame) and we want to pretend that the > + * exception came from the iret target. s/iret/IRET/ > */ > struct bad_iret_stack *new_stack = > - container_of(task_pt_regs(current), > - struct bad_iret_stack, regs); > + (struct bad_iret_stack *)this_cpu_read(cpu_tss.x86_tss.sp0) - 1; > > /* Copy the IRET target to the new stack. */ > memmove(&new_stack->regs.ip, (void *)s->regs.sp, 5*8); > -- with that: Reviewed-by: Borislav Petkov <b...@suse.de> -- Regards/Gruss, Boris. Good mailing practices for 400: avoid top-posting and trim the reply.
