From 66f93c5a02d5ba6ef17fef459143961382593212 Mon Sep 17 00:00:00 2001
From: Nicholas Piggin <npiggin@gmail.com>
Date: Thu, 15 Nov 2018 12:34:27 +1000
Subject: [PATCH] powerpc/64: Fix kernel stack 16-byte alignment
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

References: bsc#1196999 ltc#196609S git-fixes
Patch-mainline: v4.20-rc3
Git-commit: 66f93c5a02d5ba6ef17fef459143961382593212 (partial)

Commit 4c2de74cc869 ("powerpc/64: Interrupts save PPR on stack rather
than thread_struct") changed sizeof(struct pt_regs) % 16 from 0 to 8,
which causes the interrupt frame allocation on kernel entry to put the
kernel stack out of alignment.

Quadword (16-byte) alignment for the stack is required by both the
64-bit v1 ABI (v1.9 ยง 3.2.2) and the 64-bit v2 ABI (v1.1 ยง 2.2.2.1).

Add a pad field to fix alignment, and add a BUILD_BUG_ON to catch this
in future.

Fixes: 4c2de74cc869 ("powerpc/64: Interrupts save PPR on stack rather than thread_struct")
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
[only add the check, padding not needed on SLE kernel]
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
 arch/powerpc/include/asm/ptrace.h | 1 +
 arch/powerpc/kernel/setup_64.c    | 2 ++
 2 files changed, 3 insertions(+)

--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -599,6 +599,8 @@ void __init irqstack_early_init(void)
 	u64 limit = ppc64_bolted_size();
 	unsigned int i;
 
+	BUILD_BUG_ON(STACK_INT_FRAME_SIZE % 16);
+
 	/*
 	 * Interrupt stacks must be in the first segment since we
 	 * cannot afford to take SLB misses on them. They are not