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: Paul Mundt <lethal@linux-sh.org>

6 files changed, 74 insertions, 10 deletions

diff --git a/arch/sh/kernel/cpu/sh2a/Makefile b/arch/sh/kernel/cpu/sh2a/Makefile
index 350972ae9410..965fa2572b23 100644
--- a/arch/sh/kernel/cpu/sh2a/Makefile
+++ b/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
diff --git a/arch/sh/kernel/cpu/sh2a/opcode_helper.c b/arch/sh/kernel/cpu/sh2a/opcode_helper.c
new file mode 100644
index 000000000000..9704b7926d8b
--- /dev/null
+++ b/arch/sh/kernel/cpu/sh2a/opcode_helper.c
@@ -0,0 +1,55 @@
+/*
+ * 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;
+}
diff --git a/arch/sh/kernel/kgdb_stub.c b/arch/sh/kernel/kgdb_stub.c
index a5323364cbca..ffe3e3ee580d 100644
--- a/arch/sh/kernel/kgdb_stub.c
+++ b/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();
diff --git a/arch/sh/kernel/process.c b/arch/sh/kernel/process.c
index 4688b890aef8..209cc9b42186 100644
--- a/arch/sh/kernel/process.c
+++ b/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)
diff --git a/arch/sh/kernel/signal.c b/arch/sh/kernel/signal.c
index eb0191c374b6..d7d98d691c64 100644
--- a/arch/sh/kernel/signal.c
+++ b/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;
                 }
         }
diff --git a/include/asm-sh/system.h b/include/asm-sh/system.h
index e7e96ee0c8a5..82f3e229e621 100644
--- a/include/asm-sh/system.h
+++ b/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
  */