libthread: context switching for arm, still not complete

src/libthread/Linux-arm-swapcontext.c

@@ -0,0 +1,26 @@
+#include "threadimpl.h"
+
+void
+makecontext(ucontext_t *uc, void (*fn)(void), int argc, ...)
+{
+        int i, *sp;
+        va_list arg;
+        
+        sp = (int*)uc->uc_stack.ss_sp+uc->uc_stack.ss_size/4;
+        va_start(arg, argc);
+        for(i=0; i<4 && i<argc; i++)
+                uc->uc_mcontext.gregs[i] = va_arg(arg, uint);
+        va_end(arg);
+        uc->uc_mcontext.gregs[13] = (uint)sp;
+        uc->uc_mcontext.gregs[14] = (uint)fn;
+}
+
+int
+swapcontext(ucontext_t *oucp, const ucontext_t *ucp)
+{
+        if(getcontext(oucp) == 0)
+                setcontext(ucp);
+        return 0;
+}
+
+