MIPS: microMIPS: Floating point support.

Add logic needed to do floating point emulation in microMIPS mode.
Signed-off-by: Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Signed-off-by: Steven J. Hill <Steven. Hill@imgtec.com>

arch/mips/include/asm/fpu_emulator.h

@@ -54,6 +54,12 @@ do {									\
 extern int mips_dsemul(struct pt_regs *regs, mips_instruction ir,
 	unsigned long cpc);
 extern int do_dsemulret(struct pt_regs *xcp);
+extern int fpu_emulator_cop1Handler(struct pt_regs *xcp,
+				    struct mips_fpu_struct *ctx, int has_fpu,
+				    void *__user *fault_addr);
+int process_fpemu_return(int sig, void __user *fault_addr);
+int mm_isBranchInstr(struct pt_regs *regs, struct mm_decoded_insn dec_insn,
+		     unsigned long *contpc);
 
 /*
  * Instruction inserted following the badinst to further tag the sequence

arch/mips/include/asm/inst.h

@@ -73,4 +73,13 @@
 
 typedef unsigned int mips_instruction;
 
+/* microMIPS instruction decode structure. Do NOT export!!! */
+struct mm_decoded_insn {
+	mips_instruction insn;
+	mips_instruction next_insn;
+	int pc_inc;
+	int next_pc_inc;
+	int micro_mips_mode;
+};
+
 #endif /* _ASM_INST_H */

arch/mips/include/uapi/asm/inst.h

@@ -423,6 +423,11 @@ enum mm_16d_minor_op {
 	mm_addiusp_func,
 };
 
+/*
+ * (microMIPS & MIPS16e) NOP instruction.
+ */
+#define MM_NOP16	0x0c00
+
 /*
  * Damn ...  bitfields depend from byteorder :-(
  */

arch/mips/kernel/traps.c

@@ -675,7 +675,7 @@ asmlinkage void do_ov(struct pt_regs *regs)
 	force_sig_info(SIGFPE, &info, current);
 }
 
-static int process_fpemu_return(int sig, void __user *fault_addr)
+int process_fpemu_return(int sig, void __user *fault_addr)
 {
 	if (sig == SIGSEGV || sig == SIGBUS) {
 		struct siginfo si = {0};

arch/mips/kernel/unaligned.c

@@ -83,6 +83,8 @@
 #include <asm/branch.h>
 #include <asm/byteorder.h>
 #include <asm/cop2.h>
+#include <asm/fpu.h>
+#include <asm/fpu_emulator.h>
 #include <asm/inst.h>
 #include <asm/uaccess.h>
 
@@ -108,6 +110,7 @@ static void emulate_load_store_insn(struct pt_regs *regs,
 	union mips_instruction insn;
 	unsigned long value;
 	unsigned int res;
+	void __user *fault_addr = NULL;
 
 	perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, 0);
 
@@ -447,10 +450,21 @@ static void emulate_load_store_insn(struct pt_regs *regs,
 	case ldc1_op:
 	case swc1_op:
 	case sdc1_op:
-		/*
-		 * I herewith declare: this does not happen.  So send SIGBUS.
-		 */
-		goto sigbus;
+		die_if_kernel("Unaligned FP access in kernel code", regs);
+		BUG_ON(!used_math());
+		BUG_ON(!is_fpu_owner());
+
+		lose_fpu(1);	/* Save FPU state for the emulator. */
+		res = fpu_emulator_cop1Handler(regs, &current->thread.fpu, 1,
+					       &fault_addr);
+		own_fpu(1);	/* Restore FPU state. */
+
+		/* Signal if something went wrong. */
+		process_fpemu_return(res, fault_addr);
+
+		if (res == 0)
+			break;
+		return;
 
 	/*
 	 * COP2 is available to implementor for application specific use.

arch/mips/math-emu/dsemul.c

@@ -55,7 +55,9 @@ int mips_dsemul(struct pt_regs *regs, mips_instruction ir, unsigned long cpc)
 	struct emuframe __user *fr;
 	int err;
 
-	if (ir == 0) {		/* a nop is easy */
+	if ((get_isa16_mode(regs->cp0_epc) && ((ir >> 16) == MM_NOP16)) ||
+		(ir == 0)) {
+		/* NOP is easy */
 		regs->cp0_epc = cpc;
 		regs->cp0_cause &= ~CAUSEF_BD;
 		return 0;
@@ -91,8 +93,16 @@ int mips_dsemul(struct pt_regs *regs, mips_instruction ir, unsigned long cpc)
 	if (unlikely(!access_ok(VERIFY_WRITE, fr, sizeof(struct emuframe))))
 		return SIGBUS;
 
-	err = __put_user(ir, &fr->emul);
-	err |= __put_user((mips_instruction)BREAK_MATH, &fr->badinst);
+	if (get_isa16_mode(regs->cp0_epc)) {
+		err = __put_user(ir >> 16, (u16 __user *)(&fr->emul));
+		err |= __put_user(ir & 0xffff, (u16 __user *)((long)(&fr->emul) + 2));
+		err |= __put_user(BREAK_MATH >> 16, (u16 __user *)(&fr->badinst));
+		err |= __put_user(BREAK_MATH & 0xffff, (u16 __user *)((long)(&fr->badinst) + 2));
+	} else {
+		err = __put_user(ir, &fr->emul);
+		err |= __put_user((mips_instruction)BREAK_MATH, &fr->badinst);
+	}
+
 	err |= __put_user((mips_instruction)BD_COOKIE, &fr->cookie);
 	err |= __put_user(cpc, &fr->epc);
 
@@ -101,7 +111,8 @@ int mips_dsemul(struct pt_regs *regs, mips_instruction ir, unsigned long cpc)
 		return SIGBUS;
 	}
 
-	regs->cp0_epc = (unsigned long) &fr->emul;
+	regs->cp0_epc = ((unsigned long) &fr->emul) |
+		get_isa16_mode(regs->cp0_epc);
 
 	flush_cache_sigtramp((unsigned long)&fr->badinst);
 
@@ -114,9 +125,10 @@ int do_dsemulret(struct pt_regs *xcp)
 	unsigned long epc;
 	u32 insn, cookie;
 	int err = 0;
+	u16 instr[2];
 
 	fr = (struct emuframe __user *)
-		(xcp->cp0_epc - sizeof(mips_instruction));
+		(msk_isa16_mode(xcp->cp0_epc) - sizeof(mips_instruction));
 
 	/*
 	 * If we can't even access the area, something is very wrong, but we'll
@@ -131,7 +143,13 @@ int do_dsemulret(struct pt_regs *xcp)
 	 *  - Is the instruction pointed to by the EPC an BREAK_MATH?
 	 *  - Is the following memory word the BD_COOKIE?
 	 */
-	err = __get_user(insn, &fr->badinst);
+	if (get_isa16_mode(xcp->cp0_epc)) {
+		err = __get_user(instr[0], (u16 __user *)(&fr->badinst));
+		err |= __get_user(instr[1], (u16 __user *)((long)(&fr->badinst) + 2));
+		insn = (instr[0] << 16) | instr[1];
+	} else {
+		err = __get_user(insn, &fr->badinst);
+	}
 	err |= __get_user(cookie, &fr->cookie);
 
 	if (unlikely(err || (insn != BREAK_MATH) || (cookie != BD_COOKIE))) {