powerpc/64: Fix kernel stack 16-byte alignment

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 § 3.2.2) and the 64-bit v2 ABI (v1.1 § 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>

diff --git a/arch/powerpc/include/asm/ptrace.h b/arch/powerpc/include/asm/ptrace.h
index f73886a1a7f51714da637c0f9c81a8dfd1107b7f..0b8a735b6d85f08512143b539c5ee5329598c48c 100644 (file)
--- a/arch/powerpc/include/asm/ptrace.h
+++ b/arch/powerpc/include/asm/ptrace.h
@@ -54,6 +54,7 @@ struct pt_regs
 
 #ifdef CONFIG_PPC64
        unsigned long ppr;
+       unsigned long __pad;    /* Maintain 16 byte interrupt stack alignment */
 #endif
 };
 #endif

diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index 2a51e4cc8246d35d18d8ddd54b258af02dda47c4..236c1151a3a77057013313ed5da588673f5f3419 100644 (file)
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -636,6 +636,8 @@ static void *__init alloc_stack(unsigned long limit, int cpu)
 {
        unsigned long pa;
 
+       BUILD_BUG_ON(STACK_INT_FRAME_SIZE % 16);
+
        pa = memblock_alloc_base_nid(THREAD_SIZE, THREAD_SIZE, limit,
                                        early_cpu_to_node(cpu), MEMBLOCK_NONE);
        if (!pa) {