On Mon, Mar 9, 2015 at 6:28 AM, Denys Vlasenko <[email protected]> wrote: > Before the patch, tss.stack field was not referenced anywhere. > It was used only by setting sysenter's stack to point after > last byte of tss, thus the trailing field, stack[64], was used. > But grep would not know it. You can comment it out, compile, > and kernel will even run until an unlucky NMI corrupts > iomap[] (which is also not easily detectable). > > This patch changes code so the purpose and usage of this field > is not mysterious anymore, and can be easily grepped for. > > This does change generated code, for a subtle reason: > since tss_struct is ____cacheline_aligned, there happen to be > 5 longs of padding at the end. Old code was using the padding too; > new code will strictly use only SYSENTER_stack[]. > > 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] > > --- > arch/x86/include/asm/processor.h | 5 +++-- > arch/x86/kernel/asm-offsets_32.c | 2 +- > arch/x86/kernel/cpu/common.c | 2 +- > 3 files changed, 5 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/include/asm/processor.h > b/arch/x86/include/asm/processor.h > index 48a61c1..4172241 100644 > --- a/arch/x86/include/asm/processor.h > +++ b/arch/x86/include/asm/processor.h > @@ -276,9 +276,10 @@ struct tss_struct { > unsigned long io_bitmap[IO_BITMAP_LONGS + 1]; > > /* > - * .. and then another 0x100 bytes for the emergency kernel stack: > + * and then space for temporary SYSENTER stack: > */ > - unsigned long stack[64]; > + unsigned long SYSENTER_stack[63]; > + unsigned long SYSENTER_stack_last_word; > > } ____cacheline_aligned; > > diff --git a/arch/x86/kernel/asm-offsets_32.c > b/arch/x86/kernel/asm-offsets_32.c > index 3b3b9d3..4a3cbd0 100644 > --- a/arch/x86/kernel/asm-offsets_32.c > +++ b/arch/x86/kernel/asm-offsets_32.c > @@ -68,7 +68,7 @@ void foo(void) > > /* Offset from the sysenter stack to tss.sp0 */ > DEFINE(TSS_sysenter_sp0, offsetof(struct tss_struct, x86_tss.sp0) - > - sizeof(struct tss_struct)); > + (offsetof(struct tss_struct, SYSENTER_stack_last_word) + 4));
Is there no way to do this using sizeof to avoid having a "last_word" member. --Andy -- 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/
