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-rw-r--r--arch/arc/kernel/process.c20
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;
}