x86/entry/32: Fix cpu_current_top_of_stack initialization at boot

cpu_current_top_of_stack's initialization forgot about
TOP_OF_KERNEL_STACK_PADDING.  This bug didn't matter because the
idle threads never enter user mode.

Signed-off-by: Andy Lutomirski <[email protected]>
Reviewed-by: Borislav Petkov <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: http://lkml.kernel.org/r/e5e370a7e6e4fddd1c4e4cf619765d96bb874b21.1509609304.git.luto@kernel.org
Signed-off-by: Ingo Molnar <[email protected]>

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index ad59edd84de70cfb978b8c0bc2ac38b892418b71..06c18fe1c09e5ef6e13160e931654d6753366f52 100644 (file)
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -961,8 +961,7 @@ void common_cpu_up(unsigned int cpu, struct task_struct *idle)
 #ifdef CONFIG_X86_32
        /* Stack for startup_32 can be just as for start_secondary onwards */
        irq_ctx_init(cpu);
-       per_cpu(cpu_current_top_of_stack, cpu) =
-               (unsigned long)task_stack_page(idle) + THREAD_SIZE;
+       per_cpu(cpu_current_top_of_stack, cpu) = task_top_of_stack(idle);
 #else
        initial_gs = per_cpu_offset(cpu);
 #endif