linux-kernel - [PATCH 5/9] x86/smp: fix initial idle stack location on 32-bit

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Message-Id: <f28a9710944cd7f681eb6d9288ed1cc1c87caa9d.1474400222.git.jpoimboe@redhat.com>
Date:   Tue, 20 Sep 2016 15:02:47 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        "H . Peter Anvin" <hpa@...or.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Brian Gerst <brgerst@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Nilay Vaish <nilayvaish@...il.com>
Subject: [PATCH 5/9] x86/smp: fix initial idle stack location on 32-bit

On 32-bit, the initial idle stack calculation doesn't take into account
the TOP_OF_KERNEL_STACK_PADDING, making the stack end address
inconsistent with other tasks on 32-bit.

Reviewed-by: Andy Lutomirski <luto@...nel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
---
 arch/x86/kernel/smpboot.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 039790b..9345072 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -963,9 +963,7 @@ static int do_boot_cpu(int apicid, int cpu, struct task_struct *idle)
 	int cpu0_nmi_registered = 0;
 	unsigned long timeout;
 
-	idle->thread.sp = (unsigned long) (((struct pt_regs *)
-			  (THREAD_SIZE +  task_stack_page(idle))) - 1);
-
+	idle->thread.sp = (unsigned long)task_pt_regs(idle);
 	early_gdt_descr.address = (unsigned long)get_cpu_gdt_table(cpu);
 	initial_code = (unsigned long)start_secondary;
 	initial_stack  = idle->thread.sp;
-- 
2.7.4