ARC port to uClibc

For this port, I would like to give due credit to:

- Folks from Codito technologies (Sameer, Amit, Kanika, Ramana,...)
   who did the very first port

- ARC UK from 2007-2009 (Joern, Irfan, Khurram, Phil...

- Late Brendan Kehoe (may he RIP)

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

1 files changed, 21 insertions, 0 deletions

diff --git a/libc/sysdeps/linux/arc/sigrestorer.S b/libc/sysdeps/linux/arc/sigrestorer.S
new file mode 100644
index 000000000..24531d89d
--- /dev/null
+++ b/libc/sysdeps/linux/arc/sigrestorer.S
@@ -0,0 +1,21 @@
+/*
+ * Copyright (C) 2013 Synopsys, Inc. (www.synopsys.com)
+ *
+ * Licensed under the LGPL v2.1 or later, see the file COPYING.LIB in this tarball.
+ */
+
+#include <sysdep.h>
+#include <sys/syscall.h>
+
+/*
+ * Provide a real sigreturn stub to avoid kernel synthesizing one
+ * on user stack at runtime, which needs PTE permissions update
+ * (hence TLB entry update) and costly cache line flushes for
+ * code modification
+ */
+
+ENTRY(__default_rt_sa_restorer)
+    mov r8, __NR_rt_sigreturn
+    ARC_TRAP_INSN
+END(__default_rt_sa_restorer)
+libc_hidden_def(__default_rt_sa_restorer)