2 files changed, 36 insertions, 1 deletions

diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c
index 0eae00b3e588..c7ea7f2a8945 100644
--- a/arch/um/kernel/process.c
+++ b/arch/um/kernel/process.c
@@ -459,3 +459,38 @@ unsigned long arch_align_stack(unsigned long sp)
         return sp & ~0xf;
 }
 #endif
+
+unsigned long get_wchan(struct task_struct *p)
+{
+        unsigned long stack_page, sp, ip;
+        bool seen_sched = 0;
+
+        if ((p == NULL) || (p == current) || (p->state == TASK_RUNNING))
+                return 0;
+
+        stack_page = (unsigned long) task_stack_page(p);
+        /* Bail if the process has no kernel stack for some reason */
+        if (stack_page == 0)
+                return 0;
+
+        sp = p->thread.switch_buf->JB_SP;
+        /*
+         * Bail if the stack pointer is below the bottom of the kernel
+         * stack for some reason
+         */
+        if (sp < stack_page)
+                return 0;
+
+        while (sp < stack_page + THREAD_SIZE) {
+                ip = *((unsigned long *) sp);
+                if (in_sched_functions(ip))
+                        /* Ignore everything until we're above the scheduler */
+                        seen_sched = 1;
+                else if (kernel_text_address(ip) && seen_sched)
+                        return ip;
+
+                sp += sizeof(unsigned long);
+        }
+
+        return 0;
+}
diff --git a/include/asm-um/processor-generic.h b/include/asm-um/processor-generic.h
index 78c0599cc80c..057a76d41569 100644
--- a/include/asm-um/processor-generic.h
+++ b/include/asm-um/processor-generic.h
@@ -128,6 +128,6 @@ extern struct cpuinfo_um cpu_data[];
 
 
 #define KSTK_REG(tsk, reg) get_thread_reg(reg, &tsk->thread.switch_buf)
-#define get_wchan(p) (0)
+extern unsigned long get_wchan(struct task_struct *p);
 
 #endif