sh: math-emu support

This implements initial math-emu support, aimed primarily at SH-3.

Signed-off-by: Takashi YOSHII <[email protected]>
Signed-off-by: Paul Mundt <[email protected]>

Author: Takashi YOSHII

arch/sh/Kconfig

@@ -339,6 +339,15 @@ config SH_FPU
 
 	  This option must be set in order to enable the FPU.
 
+config SH_FPU_EMU
+	bool "FPU emulation support"
+	depends on !SH_FPU && EXPERIMENTAL
+	default n
+	help
+	  Selecting this option will enable support for software FPU emulation.
+	  Most SH-3 users will want to say Y here, whereas most SH-4 users will
+	  want to say N.
+
 config SH_DSP
 	bool "DSP support"
 	depends on !CPU_SH4

arch/sh/Makefile

@@ -79,6 +79,7 @@ head-y := arch/sh/kernel/head.o arch/sh/kernel/init_task.o
 LIBGCC := $(shell $(CC) $(CFLAGS) -print-libgcc-file-name)
 
 core-y				+= arch/sh/kernel/ arch/sh/mm/
+core-$(CONFIG_SH_FPU_EMU)	+= arch/sh/math-emu/
 
 # Boards
 machdir-$(CONFIG_SH_SOLUTION_ENGINE)		:= se/770x

arch/sh/kernel/traps.c

@@ -36,40 +36,15 @@
 
 #ifdef CONFIG_SH_KGDB
 #include <asm/kgdb.h>
-#define CHK_REMOTE_DEBUG(regs)                                               \
-{                                                                            \
-  if ((kgdb_debug_hook != (kgdb_debug_hook_t *) NULL) && (!user_mode(regs))) \
-  {                                                                          \
-    (*kgdb_debug_hook)(regs);                                                \
-  }                                                                          \
+#define CHK_REMOTE_DEBUG(regs)                 	\
+{       					\
+	if (kgdb_debug_hook && !user_mode(regs))\
+		(*kgdb_debug_hook)(regs);       \
 }
 #else
 #define CHK_REMOTE_DEBUG(regs)
 #endif
 
-#define DO_ERROR(trapnr, signr, str, name, tsk)				\
-asmlinkage void do_##name(unsigned long r4, unsigned long r5,		\
-			  unsigned long r6, unsigned long r7,		\
-			  struct pt_regs regs)				\
-{									\
-	unsigned long error_code;					\
- 									\
-	/* Check if it's a DSP instruction */				\
- 	if (is_dsp_inst(&regs)) {					\
-		/* Enable DSP mode, and restart instruction. */		\
-		regs.sr |= SR_DSP;					\
-		return;							\
-	}								\
-									\
-	asm volatile("stc	r2_bank, %0": "=r" (error_code));	\
-	local_irq_enable();						\
-	tsk->thread.error_code = error_code;				\
-	tsk->thread.trap_no = trapnr;					\
-        CHK_REMOTE_DEBUG(&regs);					\
-	force_sig(signr, tsk);						\
-	die_if_no_fixup(str,&regs,error_code);				\
-}
-
 #ifdef CONFIG_CPU_SH2
 #define TRAP_RESERVED_INST	4
 #define TRAP_ILLEGAL_SLOT_INST	6
@@ -575,8 +550,117 @@ int is_dsp_inst(struct pt_regs *regs)
 #define is_dsp_inst(regs)	(0)
 #endif /* CONFIG_SH_DSP */
 
-DO_ERROR(TRAP_RESERVED_INST, SIGILL, "reserved instruction", reserved_inst, current)
-DO_ERROR(TRAP_ILLEGAL_SLOT_INST, SIGILL, "illegal slot instruction", illegal_slot_inst, current)
+extern int do_fpu_inst(unsigned short, struct pt_regs*);
+
+asmlinkage void do_reserved_inst(unsigned long r4, unsigned long r5,
+				unsigned long r6, unsigned long r7,
+				struct pt_regs regs)
+{
+	unsigned long error_code;
+	struct task_struct *tsk = current;
+
+#ifdef CONFIG_SH_FPU_EMU
+	unsigned short inst;
+	int err;
+
+	get_user(inst, (unsigned short*)regs.pc);
+
+	err = do_fpu_inst(inst, &regs);
+	if (!err) {
+		regs.pc += 2;
+		return;
+	}
+	/* not a FPU inst. */
+#endif
+
+#ifdef CONFIG_SH_DSP
+	/* Check if it's a DSP instruction */
+ 	if (is_dsp_inst(&regs)) {
+		/* Enable DSP mode, and restart instruction. */
+		regs.sr |= SR_DSP;
+		return;
+	}
+#endif
+
+	asm volatile("stc	r2_bank, %0": "=r" (error_code));
+	local_irq_enable();
+	tsk->thread.error_code = error_code;
+	tsk->thread.trap_no = TRAP_RESERVED_INST;
+	CHK_REMOTE_DEBUG(&regs);
+	force_sig(SIGILL, tsk);
+	die_if_no_fixup("reserved instruction", &regs, error_code);
+}
+
+#ifdef CONFIG_SH_FPU_EMU
+static int emulate_branch(unsigned short inst, struct pt_regs* regs)
+{
+	/*
+	 * bfs: 8fxx: PC+=d*2+4;
+	 * bts: 8dxx: PC+=d*2+4;
+	 * bra: axxx: PC+=D*2+4;
+	 * bsr: bxxx: PC+=D*2+4  after PR=PC+4;
+	 * braf:0x23: PC+=Rn*2+4;
+	 * bsrf:0x03: PC+=Rn*2+4 after PR=PC+4;
+	 * jmp: 4x2b: PC=Rn;
+	 * jsr: 4x0b: PC=Rn      after PR=PC+4;
+	 * rts: 000b: PC=PR;
+	 */
+	if ((inst & 0xfd00) == 0x8d00) {
+		regs->pc += SH_PC_8BIT_OFFSET(inst);
+		return 0;
+	}
+
+	if ((inst & 0xe000) == 0xa000) {
+		regs->pc += SH_PC_12BIT_OFFSET(inst);
+		return 0;
+	}
+
+	if ((inst & 0xf0df) == 0x0003) {
+		regs->pc += regs->regs[(inst & 0x0f00) >> 8] + 4;
+		return 0;
+	}
+
+	if ((inst & 0xf0df) == 0x400b) {
+		regs->pc = regs->regs[(inst & 0x0f00) >> 8];
+		return 0;
+	}
+
+	if ((inst & 0xffff) == 0x000b) {
+		regs->pc = regs->pr;
+		return 0;
+	}
+
+	return 1;
+}
+#endif
+
+asmlinkage void do_illegal_slot_inst(unsigned long r4, unsigned long r5,
+				unsigned long r6, unsigned long r7,
+				struct pt_regs regs)
+{
+	unsigned long error_code;
+	struct task_struct *tsk = current;
+#ifdef CONFIG_SH_FPU_EMU
+	unsigned short inst;
+
+	get_user(inst, (unsigned short *)regs.pc + 1);
+	if (!do_fpu_inst(inst, &regs)) {
+		get_user(inst, (unsigned short *)regs.pc);
+		if (!emulate_branch(inst, &regs))
+			return;
+		/* fault in branch.*/
+	}
+	/* not a FPU inst. */
+#endif
+
+	asm volatile("stc	r2_bank, %0": "=r" (error_code));
+	local_irq_enable();
+	tsk->thread.error_code = error_code;
+	tsk->thread.trap_no = TRAP_RESERVED_INST;
+	CHK_REMOTE_DEBUG(&regs);
+	force_sig(SIGILL, tsk);
+	die_if_no_fixup("illegal slot instruction", &regs, error_code);
+}
 
 asmlinkage void do_exception_error(unsigned long r4, unsigned long r5,
 				   unsigned long r6, unsigned long r7,
@@ -634,14 +718,16 @@ void __init trap_init(void)
 	exception_handling_table[TRAP_ILLEGAL_SLOT_INST]
 		= (void *)do_illegal_slot_inst;
 
-#ifdef CONFIG_CPU_SH4
-	if (!(cpu_data->flags & CPU_HAS_FPU)) {
-		/* For SH-4 lacking an FPU, treat floating point instructions
-		   as reserved. */
-		/* entry 64 corresponds to EXPEVT=0x800 */
-		exception_handling_table[64] = (void *)do_reserved_inst;
-		exception_handling_table[65] = (void *)do_illegal_slot_inst;
-	}
+#if defined(CONFIG_CPU_SH4) && !defined(CONFIG_SH_FPU) || \
+    defined(CONFIG_SH_FPU_EMU)
+	/*
+	 * For SH-4 lacking an FPU, treat floating point instructions as
+	 * reserved. They'll be handled in the math-emu case, or faulted on
+	 * otherwise.
+	 */
+	/* entry 64 corresponds to EXPEVT=0x800 */
+	exception_handling_table[64] = (void *)do_reserved_inst;
+	exception_handling_table[65] = (void *)do_illegal_slot_inst;
 #endif
 
 	/* Setup VBR for boot cpu */

arch/sh/math-emu/Makefile

@@ -0,0 +1 @@
+obj-y	:= math.o