sh: Support for SH-2A 32-bit opcodes.

SH-2A supports both 16 and 32-bit instructions, add a simple helper
for figuring out the instruction size in the places where there are
hardcoded 16-bit assumptions.
Signed-off-by: NPaul Mundt <lethal@linux-sh.org>

arch/sh/kernel/cpu/sh2a/Makefile

@@ -2,9 +2,8 @@
 # Makefile for the Linux/SuperH SH-2A backends.
 #
 
-obj-y	:= common.o probe.o
+obj-y	:= common.o probe.o opcode_helper.o
 
-common-y	+= $(addprefix ../sh2/, ex.o)
-common-y	+= $(addprefix ../sh2/, entry.o)
+common-y	+= $(addprefix ../sh2/, ex.o entry.o)
 
 obj-$(CONFIG_CPU_SUBTYPE_SH7206) += setup-sh7206.o clock-sh7206.o

arch/sh/kernel/cpu/sh2a/opcode_helper.c

+/*
+ * arch/sh/kernel/cpu/sh2a/opcode_helper.c
+ *
+ * Helper for the SH-2A 32-bit opcodes.
+ *
+ *  Copyright (C) 2007  Paul Mundt
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+#include <linux/kernel.h>
+#include <asm/system.h>
+
+/*
+ * Instructions on SH are generally fixed at 16-bits, however, SH-2A
+ * introduces some 32-bit instructions. Since there are no real
+ * constraints on their use (and they can be mixed and matched), we need
+ * to check the instruction encoding to work out if it's a true 32-bit
+ * instruction or not.
+ *
+ * Presently, 32-bit opcodes have only slight variations in what the
+ * actual encoding looks like in the first-half of the instruction, which
+ * makes it fairly straightforward to differentiate from the 16-bit ones.
+ *
+ * First 16-bits of encoding		Used by
+ *
+ *	0011nnnnmmmm0001	mov.b, mov.w, mov.l, fmov.d,
+ *				fmov.s, movu.b, movu.w
+ *
+ *	0011nnnn0iii1001        bclr.b, bld.b, bset.b, bst.b, band.b,
+ *				bandnot.b, bldnot.b, bor.b, bornot.b,
+ *				bxor.b
+ *
+ *	0000nnnniiii0000        movi20
+ *	0000nnnniiii0001        movi20s
+ */
+unsigned int instruction_size(unsigned int insn)
+{
+	/* Look for the common cases */
+	switch ((insn & 0xf00f)) {
+	case 0x0000:	/* movi20 */
+	case 0x0001:	/* movi20s */
+	case 0x3001:	/* 32-bit mov/fmov/movu variants */
+		return 4;
+	}
+
+	/* And the special cases.. */
+	switch ((insn & 0xf08f)) {
+	case 0x3009:	/* 32-bit b*.b bit operations */
+		return 4;
+	}
+
+	return 2;
+}

arch/sh/kernel/kgdb_stub.c

@@ -867,7 +867,7 @@ static void kgdb_command_loop(const int excep_code, const int trapa_value)
 	   trap 0xff, since that indicates a compiled-in breakpoint which
 	   will not be replaced (and we would retake the trap forever) */
 	if ((excep_code == TRAP_VEC) && (trapa_value != (0x3c << 2)))
-		trap_registers.pc -= 2;
+		trap_registers.pc -= instruction_size(trap_registers.pc);
 
 	/* Undo any stepping we may have done */
 	undo_single_step();

arch/sh/kernel/process.c

@@ -19,6 +19,7 @@
 #include <asm/uaccess.h>
 #include <asm/mmu_context.h>
 #include <asm/pgalloc.h>
+#include <asm/system.h>
 #include <asm/ubc.h>
 
 static int hlt_counter;
@@ -497,7 +498,7 @@ asmlinkage void debug_trap_handler(unsigned long r4, unsigned long r5,
 	struct pt_regs *regs = RELOC_HIDE(&__regs, 0);
 
 	/* Rewind */
-	regs->pc -= 2;
+	regs->pc -= instruction_size(regs->pc);
 
 	if (notify_die(DIE_TRAP, regs, regs->tra & 0xff,
 		       SIGTRAP) == NOTIFY_STOP)
@@ -516,7 +517,7 @@ asmlinkage void bug_trap_handler(unsigned long r4, unsigned long r5,
 	struct pt_regs *regs = RELOC_HIDE(&__regs, 0);
 
 	/* Rewind */
-	regs->pc -= 2;
+	regs->pc -= instruction_size(regs->pc);
 
 	if (notify_die(DIE_TRAP, regs, TRAPA_BUG_OPCODE & 0xff,
 		       SIGTRAP) == NOTIFY_STOP)

arch/sh/kernel/signal.c

@@ -23,7 +23,7 @@
 #include <linux/personality.h>
 #include <linux/binfmts.h>
 #include <linux/freezer.h>
-
+#include <asm/system.h>
 #include <asm/ucontext.h>
 #include <asm/uaccess.h>
 #include <asm/pgtable.h>
@@ -500,7 +500,7 @@ handle_signal(unsigned long sig, struct k_sigaction *ka, siginfo_t *info,
 				}
 			/* fallthrough */
 			case -ERESTARTNOINTR:
-				regs->pc -= 2;
+				regs->pc -= instruction_size(regs->pc);
 		}
 	} else {
 		/* gUSA handling */
@@ -600,9 +600,9 @@ static void do_signal(struct pt_regs *regs, unsigned int save_r0)
 		    regs->regs[0] == -ERESTARTSYS ||
 		    regs->regs[0] == -ERESTARTNOINTR) {
 			regs->regs[0] = save_r0;
-			regs->pc -= 2;
+			regs->pc -= instruction_size(regs->pc);
 		} else if (regs->regs[0] == -ERESTART_RESTARTBLOCK) {
-			regs->pc -= 2;
+			regs->pc -= instruction_size(regs->pc);
 			regs->regs[3] = __NR_restart_syscall;
 		}
 	}

include/asm-sh/system.h

@@ -255,6 +255,15 @@ static inline void *set_exception_table_evt(unsigned int evt, void *handler)
 	return set_exception_table_vec(evt >> 5, handler);
 }
 
+/*
+ * SH-2A has both 16 and 32-bit opcodes, do lame encoding checks.
+ */
+#ifdef CONFIG_CPU_SH2A
+extern unsigned int instruction_size(unsigned int insn);
+#else
+#define instruction_size(insn)	(2)
+#endif
+
 /* XXX
  * disable hlt during certain critical i/o operations
  */