powerpc/64: Fix kernel stack 16-byte alignment

Commit 4c2de74 ("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: 4c2de74 ("powerpc/64: Interrupts save PPR on stack rather than thread_struct") Signed-off-by: Nicholas Piggin <[email protected]> Signed-off-by: Michael Ellerman <[email protected]>
jb55 · Nov 15, 2018 · 66f93c5 · 66f93c5
1 parent 437ccdc
commit 66f93c5
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diff --git 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
@@ -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) {
-Original file line number
+Diff line change
@@ Expand Up / @@ -54,6 +54,7 @@ struct pt_regs @@
     #ifdef CONFIG_PPC64
     	unsigned long ppr;
+    	unsigned long __pad;	/* Maintain 16 byte interrupt stack alignment */
     #endif
     };
     #endif
@@ Expand Down @@