1 files changed, 20 insertions, 0 deletions

diff --git a/arch/arc/kernel/process.c b/arch/arc/kernel/process.c
index 4674541eba3f..8ce6e7235915 100644
--- a/arch/arc/kernel/process.c
+++ b/arch/arc/kernel/process.c
@@ -241,6 +241,26 @@ 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;
 }