Merge pull request #40 from toradex/4.9-2.3.x-imx

4.9 2.3.x imx

1 files changed, 20 insertions, 0 deletions

diff --git a/arch/arc/kernel/process.c b/arch/arc/kernel/process.c
index 0e8c0151a390..3ce12137f94f 100644
--- a/arch/arc/kernel/process.c
+++ b/arch/arc/kernel/process.c
@@ -213,6 +213,26 @@ int copy_thread(unsigned long clone_flags,
 		task_thread_info(current)->thr_ptr;
 	}
 
+
+	/*
+	 * setup usermode thread pointer #1:
+	 * when child is picked by scheduler, __switch_to() uses @c_callee to
+	 * populate usermode callee regs: this works (despite being in a kernel
+	 * function) since special return path for child @ret_from_fork()
+	 * ensures those regs are not clobbered all the way to RTIE to usermode
+	 */
+	c_callee->r25 = task_thread_info(p)->thr_ptr;
+
+#ifdef CONFIG_ARC_CURR_IN_REG
+	/*
+	 * setup usermode thread pointer #2:
+	 * however for this special use of r25 in kernel, __switch_to() sets
+	 * r25 for kernel needs and only in the final return path is usermode
+	 * r25 setup, from pt_regs->user_r25. So set that up as well
+	 */
+	c_regs->user_r25 = c_callee->r25;
+#endif
+
 	return 0;
 }