Messages in this thread | | | Date | Thu, 2 Jul 2015 14:09:32 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH v4 14/17] x86/asm/entry/64: Migrate error and interrupt exit work to C |
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On Mon, Jun 29, 2015 at 12:33:46PM -0700, Andy Lutomirski wrote: > Signed-off-by: Andy Lutomirski <luto@kernel.org> > --- > arch/x86/entry/entry_64.S | 63 +++++++++++----------------------------- > arch/x86/entry/entry_64_compat.S | 5 ++++ > 2 files changed, 22 insertions(+), 46 deletions(-) > > diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S > index ce2c9049abef..08a37ec049f0 100644 > --- a/arch/x86/entry/entry_64.S > +++ b/arch/x86/entry/entry_64.S > @@ -508,7 +508,16 @@ END(irq_entries_start) > > testb $3, CS(%rsp) > jz 1f > + > + /* > + * IRQ from user mode. Switch to kernel gsbase and inform context > + * tracking that we're in kernel mode. > + */ > SWAPGS > +#ifdef CONFIG_CONTEXT_TRACKING > + call enter_from_user_mode > +#endif
I think you can make this much cleaner by getting rid of the ifdeffery and pushing it into the enter_from_user_mode() function:
__visible void enter_from_user_mode(void) { #ifdef CONFIG_CONTEXT_TRACKING
...
#endif }
The disadvantage of all that cleanliness is that we get one dumb
call enter_from_user_mode
there to this abomination:
ffffffff810014f0 <enter_from_user_mode>: ffffffff810014f0: e8 db 97 67 00 callq ffffffff8167acd0 <__fentry__> ffffffff810014f5: 55 push %rbp ffffffff810014f6: 48 89 e5 mov %rsp,%rbp ffffffff810014f9: 5d pop %rbp ffffffff810014fa: c3 retq ffffffff810014fb: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1)
which sux.
We sure could use LTO here.
-- Regards/Gruss, Boris.
ECO tip #101: Trim your mails when you reply. --
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