From 75182b1632a89f12540baa1806a7c5c180db620c Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Thu, 5 Mar 2015 19:19:03 -0800 Subject: [PATCH] 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 Signed-off-by: Andy Lutomirski Cc: Borislav Petkov Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/ef8254ad414cbb8034c9a56396eeb24f5dd5b0de.1425611534.git.luto@amacapital.net Signed-off-by: Ingo Molnar --- arch/x86/include/asm/thread_info.h | 3 +-- arch/x86/kernel/traps.c | 4 ++-- 2 files changed, 3 insertions(+), 4 deletions(-) diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h index 1d4e4f2..a2fa189 100644 --- a/arch/x86/include/asm/thread_info.h +++ b/arch/x86/include/asm/thread_info.h @@ -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; } diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 9965bd1..fa29058 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -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); } -- 2.7.4