Commit 75182b16 authored Mar 05, 2015 by Andy Lutomirski Committed by Ingo Molnar Mar 06, 2015

x86/asm/entry: Switch all C consumers of kernel_stack to this_cpu_sp0()



This will make modifying the semantics of kernel_stack easier.

The change to ist_begin_non_atomic() is necessary because sp0 no
longer points to the same THREAD_SIZE-aligned region as RSP;
it's one byte too high for that.  At Denys' suggestion, rather
than offsetting it, just check explicitly that we're in the
correct range ending at sp0.  This has the added benefit that we
no longer assume that the thread stack is aligned to
THREAD_SIZE.

Suggested-by: Denys Vlasenko <dvlasenk@redhat.com>
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/ef8254ad414cbb8034c9a56396eeb24f5dd5b0de.1425611534.git.luto@amacapital.net


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 8ef46a67

arch/x86/include/asm/thread_info.h

+1 −2

Original line number	Diff line number	Diff line
		@@ -159,8 +159,7 @@ DECLARE_PER_CPU(unsigned long, kernel_stack);
		static inline struct thread_info *current_thread_info(void)
		{
		struct thread_info *ti;
		ti = (void *)(this_cpu_read_stable(kernel_stack) +
		KERNEL_STACK_OFFSET - THREAD_SIZE);
		ti = (void *)(this_cpu_sp0() - THREAD_SIZE);
		return ti;
		}

arch/x86/kernel/traps.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -174,8 +174,8 @@ void ist_begin_non_atomic(struct pt_regs *regs)
		* will catch asm bugs and any attempt to use ist_preempt_enable
		* from double_fault.
		*/
		BUG_ON(((current_stack_pointer() ^ this_cpu_read_stable(kernel_stack))
		& ~(THREAD_SIZE - 1)) != 0);
		BUG_ON((unsigned long)(this_cpu_sp0() - current_stack_pointer()) >=
		THREAD_SIZE);

		preempt_count_sub(HARDIRQ_OFFSET);
		}

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