The ucontext is 16-byte aligned, which means that struct tcb is

16-byte aligned. Consequently, struct tcb is a multiple of 16
bytes in size. We need to make sure there's no padding after
struct ppc32_tp. We do this by explicitly adding the necessary
padding in front of it.

lib/libkse/arch/powerpc/include/pthread_md.h

@@ -70,6 +70,7 @@ struct tcb {
 	struct pthread		*tcb_thread;
 	struct kcb		*tcb_curkcb;
 	long			tcb_isfake;
+	long			tcb_spare[3];
 	struct ppc32_tp		tcb_tp;
 };
 

lib/libpthread/arch/powerpc/include/pthread_md.h

@@ -70,6 +70,7 @@ struct tcb {
 	struct pthread		*tcb_thread;
 	struct kcb		*tcb_curkcb;
 	long			tcb_isfake;
+	long			tcb_spare[3];
 	struct ppc32_tp		tcb_tp;
 };