Blackfin arch: defines and provides entry points for certain user space functions at fixed addresses

This patch defines (and provides) entry points for certain user space functions
at fixed addresses.  The Blackfin has no usable atomic instructions, but we can
ensure that these code sequences appear atomic from a user space point of view
by detecting when we're in the process of executing them during the interrupt
handler return path.  This allows much more efficient pthread lock
implementations than the bfin_spinlock syscall we're currently using.

Also provided is a small sys_rt_sigreturn stub which can be used by the signal
handler setup code.  The signal.c part will be committed separately.

Signed-off-by: Bernd Schmidt <bernd.schmidt@analog.com>
Signed-off-by: Bryan Wu <bryan.wu@analog.com>

1 files changed, 20 insertions, 0 deletions

diff --git a/include/asm-blackfin/fixed_code.h b/include/asm-blackfin/fixed_code.h
new file mode 100644
index 000000000000..e6df84ee1557
--- /dev/null
+++ b/include/asm-blackfin/fixed_code.h
@@ -0,0 +1,20 @@
+/* This file defines the fixed addresses where userspace programs can find
+   atomic code sequences.  */
+
+#define FIXED_CODE_START	0x400
+
+#define SIGRETURN_STUB		0x400
+
+#define ATOMIC_SEQS_START	0x410
+
+#define ATOMIC_XCHG32		0x410
+#define ATOMIC_CAS32		0x420
+#define ATOMIC_ADD32		0x430
+#define ATOMIC_SUB32		0x440
+#define ATOMIC_IOR32		0x450
+#define ATOMIC_AND32		0x460
+#define ATOMIC_XOR32		0x470
+
+#define ATOMIC_SEQS_END		0x480
+
+#define FIXED_CODE_END		0x480