+
+unsigned long get_tm_stackpointer(struct pt_regs *regs)
+{
+ /* When in an active transaction that takes a signal, we need to be
+ * careful with the stack. It's possible that the stack has moved back
+ * up after the tbegin. The obvious case here is when the tbegin is
+ * called inside a function that returns before a tend. In this case,
+ * the stack is part of the checkpointed transactional memory state.
+ * If we write over this non transactionally or in suspend, we are in
+ * trouble because if we get a tm abort, the program counter and stack
+ * pointer will be back at the tbegin but our in memory stack won't be
+ * valid anymore.
+ *
+ * To avoid this, when taking a signal in an active transaction, we
+ * need to use the stack pointer from the checkpointed state, rather
+ * than the speculated state. This ensures that the signal context
+ * (written tm suspended) will be written below the stack required for
+ * the rollback. The transaction is aborted becuase of the treclaim,
+ * so any memory written between the tbegin and the signal will be
+ * rolled back anyway.
+ *
+ * For signals taken in non-TM or suspended mode, we use the
+ * normal/non-checkpointed stack pointer.
+ */
+
+#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
+ if (MSR_TM_ACTIVE(regs->msr)) {
+ tm_enable();
+ tm_reclaim(¤t->thread, regs->msr, TM_CAUSE_SIGNAL);
+ if (MSR_TM_TRANSACTIONAL(regs->msr))
+ return current->thread.ckpt_regs.gpr[1];
+ }
+#endif
+ return regs->gpr[1];
+}