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>
diff --git a/include/asm-blackfin/fixed_code.h b/include/asm-blackfin/fixed_code.h
new file mode 100644
index 0000000..e6df84e
--- /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