alpha: add asm/extable.h

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 55 insertions, 0 deletions

diff --git a/arch/alpha/include/asm/extable.h b/arch/alpha/include/asm/extable.h
new file mode 100644
index 000000000000..048e209e524c
--- /dev/null
+++ b/arch/alpha/include/asm/extable.h
@@ -0,0 +1,55 @@
+#ifndef _ASM_EXTABLE_H
+#define _ASM_EXTABLE_H
+
+/*
+ * About the exception table:
+ *
+ * - insn is a 32-bit pc-relative offset from the faulting insn.
+ * - nextinsn is a 16-bit offset off of the faulting instruction
+ *   (not off of the *next* instruction as branches are).
+ * - errreg is the register in which to place -EFAULT.
+ * - valreg is the final target register for the load sequence
+ *   and will be zeroed.
+ *
+ * Either errreg or valreg may be $31, in which case nothing happens.
+ *
+ * The exception fixup information "just so happens" to be arranged
+ * as in a MEM format instruction.  This lets us emit our three
+ * values like so:
+ *
+ *      lda valreg, nextinsn(errreg)
+ *
+ */
+
+struct exception_table_entry
+{
+	signed int insn;
+	union exception_fixup {
+		unsigned unit;
+		struct {
+			signed int nextinsn : 16;
+			unsigned int errreg : 5;
+			unsigned int valreg : 5;
+		} bits;
+	} fixup;
+};
+
+/* Returns the new pc */
+#define fixup_exception(map_reg, _fixup, pc)			\
+({								\
+	if ((_fixup)->fixup.bits.valreg != 31)			\
+		map_reg((_fixup)->fixup.bits.valreg) = 0;	\
+	if ((_fixup)->fixup.bits.errreg != 31)			\
+		map_reg((_fixup)->fixup.bits.errreg) = -EFAULT;	\
+	(pc) + (_fixup)->fixup.bits.nextinsn;			\
+})
+
+#define ARCH_HAS_RELATIVE_EXTABLE
+
+#define swap_ex_entry_fixup(a, b, tmp, delta)			\
+	do {							\
+		(a)->fixup.unit = (b)->fixup.unit;		\
+		(b)->fixup.unit = (tmp).fixup.unit;		\
+	} while (0)
+
+#endif