unaligned.c

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	 * To update f32-f127, there are three choices:
	 *
	 *	(1) save f32-f127 to thread.fph and update the values there
	 *	(2) use a gigantic switch statement to directly access the registers
	 *	(3) generate code on the fly to update the desired register
	 *
	 * For now, we are using approach (1).
	 */
	if (regnum >= IA64_FIRST_ROTATING_FR) {
		ia64_sync_fph(current);
		current->thread.fph[IA64_FPH_OFFS(regnum)] = *fpval;
	} else {
		/*
		 * pt_regs or switch_stack ?
		 */
		if (FR_IN_SW(regnum)) {
			addr = (unsigned long)sw;
		} else {
			addr = (unsigned long)regs;
		}

		DPRINT("tmp_base=%lx offset=%d\n", addr, FR_OFFS(regnum));

		addr += FR_OFFS(regnum);
		*(struct ia64_fpreg *)addr = *fpval;

		/*
		 * mark the low partition as being used now
		 *
		 * It is highly unlikely that this bit is not already set, but
		 * let's do it for safety.
		 */
		regs->cr_ipsr |= IA64_PSR_MFL;
	}
}

/*
 * Those 2 inline functions generate the spilled versions of the constant floating point
 * registers which can be used with stfX
 */
static inline void
float_spill_f0 (struct ia64_fpreg *final)
{
	__asm__ __volatile__ ("stf.spill [%0]=f0" :: "r"(final) : "memory");
}

static inline void
float_spill_f1 (struct ia64_fpreg *final)
{
	__asm__ __volatile__ ("stf.spill [%0]=f1" :: "r"(final) : "memory");
}

static void
getfpreg (unsigned long regnum, struct ia64_fpreg *fpval, struct pt_regs *regs)
{
	struct switch_stack *sw = (struct switch_stack *) regs - 1;
	unsigned long addr;

	/*
	 * From EAS-2.5: FPDisableFault has higher priority than
	 * Unaligned Fault. Thus, when we get here, we know the partition is
	 * enabled.
	 *
	 * When regnum > 31, the register is still live and we need to force a save
	 * to current->thread.fph to get access to it.  See discussion in setfpreg()
	 * for reasons and other ways of doing this.
	 */
	if (regnum >= IA64_FIRST_ROTATING_FR) {
		ia64_flush_fph(current);
		*fpval = current->thread.fph[IA64_FPH_OFFS(regnum)];
	} else {
		/*
		 * f0 = 0.0, f1= 1.0. Those registers are constant and are thus
		 * not saved, we must generate their spilled form on the fly
		 */
		switch(regnum) {
		case 0:
			float_spill_f0(fpval);
			break;
		case 1:
			float_spill_f1(fpval);
			break;
		default:
			/*
			 * pt_regs or switch_stack ?
			 */
			addr =  FR_IN_SW(regnum) ? (unsigned long)sw
						 : (unsigned long)regs;

			DPRINT("is_sw=%d tmp_base=%lx offset=0x%x\n",
			       FR_IN_SW(regnum), addr, FR_OFFS(regnum));

			addr  += FR_OFFS(regnum);
			*fpval = *(struct ia64_fpreg *)addr;
		}
	}
}


static void
getreg (unsigned long regnum, unsigned long *val, int *nat, struct pt_regs *regs)
{
	struct switch_stack *sw = (struct switch_stack *) regs - 1;
	unsigned long addr, *unat;

	if (regnum >= IA64_FIRST_STACKED_GR) {
		get_rse_reg(regs, regnum, val, nat);
		return;
	}

	/*
	 * take care of r0 (read-only always evaluate to 0)
	 */
	if (regnum == 0) {
		*val = 0;
		if (nat)
			*nat = 0;
		return;
	}

	/*
	 * Now look at registers in [0-31] range and init correct UNAT
	 */
	if (GR_IN_SW(regnum)) {
		addr = (unsigned long)sw;
		unat = &sw->ar_unat;
	} else {
		addr = (unsigned long)regs;
		unat = &sw->caller_unat;
	}

	DPRINT("addr_base=%lx offset=0x%x\n", addr,  GR_OFFS(regnum));

	addr += GR_OFFS(regnum);

	*val  = *(unsigned long *)addr;

	/*
	 * do it only when requested
	 */
	if (nat)
		*nat  = (*unat >> (addr >> 3 & 0x3f)) & 0x1UL;
}

static void
emulate_load_updates (update_t type, load_store_t ld, struct pt_regs *regs, unsigned long ifa)
{
	/*
	 * IMPORTANT:
	 * Given the way we handle unaligned speculative loads, we should
	 * not get to this point in the code but we keep this sanity check,
	 * just in case.
	 */
	if (ld.x6_op == 1 || ld.x6_op == 3) {
		printk(KERN_ERR __FUNCTION__": register update on speculative load, error\n");
		die_if_kernel("unaligned reference on specualtive load with register update\n",
			      regs, 30);
	}


	/*
	 * at this point, we know that the base register to update is valid i.e.,
	 * it's not r0
	 */
	if (type == UPD_IMMEDIATE) {
		unsigned long imm;

		/*
		 * Load +Imm: ldXZ r1=[r3],imm(9)
		 *
		 *
		 * form imm9: [13:19] contain the first 7 bits
		 */
		imm = ld.x << 7 | ld.imm;

		/*
		 * sign extend (1+8bits) if m set
		 */
		if (ld.m) imm |= SIGN_EXT9;

		/*
		 * ifa == r3 and we know that the NaT bit on r3 was clear so
		 * we can directly use ifa.
		 */
		ifa += imm;

		setreg(ld.r3, ifa, 0, regs);

		DPRINT("ld.x=%d ld.m=%d imm=%ld r3=0x%lx\n", ld.x, ld.m, imm, ifa);

	} else if (ld.m) {
		unsigned long r2;
		int nat_r2;

		/*
		 * Load +Reg Opcode: ldXZ r1=[r3],r2
		 *
		 * Note: that we update r3 even in the case of ldfX.a
		 * (where the load does not happen)
		 *
		 * The way the load algorithm works, we know that r3 does not
		 * have its NaT bit set (would have gotten NaT consumption
		 * before getting the unaligned fault). So we can use ifa
		 * which equals r3 at this point.
		 *
		 * IMPORTANT:
		 * The above statement holds ONLY because we know that we
		 * never reach this code when trying to do a ldX.s.
		 * If we ever make it to here on an ldfX.s then
		 */
		getreg(ld.imm, &r2, &nat_r2, regs);

		ifa += r2;

		/*
		 * propagate Nat r2 -> r3
		 */
		setreg(ld.r3, ifa, nat_r2, regs);

		DPRINT("imm=%d r2=%ld r3=0x%lx nat_r2=%d\n",ld.imm, r2, ifa, nat_r2);
	}
}


static int
emulate_load_int (unsigned long ifa, load_store_t ld, struct pt_regs *regs)
{
	unsigned int len = 1 << ld.x6_sz;

	/*
	 * r0, as target, doesn't need to be checked because Illegal Instruction
	 * faults have higher priority than unaligned faults.
	 *
	 * r0 cannot be found as the base as it would never generate an
	 * unaligned reference.
	 */

	/*
	 * ldX.a we don't try to emulate anything but we must invalidate the ALAT entry.
	 * See comment below for explanation on how we handle ldX.a
	 */
	if (ld.x6_op != 0x2) {
		unsigned long val = 0;

		if (len != 2 && len != 4 && len != 8) {
			DPRINT("unknown size: x6=%d\n", ld.x6_sz);
			return -1;
		}
		/* this assumes little-endian byte-order: */
		if (copy_from_user(&val, (void *) ifa, len))
		    return -1;
		setreg(ld.r1, val, 0, regs);
	}

	/*
	 * check for updates on any kind of loads
	 */
	if (ld.op == 0x5 || ld.m)
		emulate_load_updates(ld.op == 0x5 ? UPD_IMMEDIATE: UPD_REG, ld, regs, ifa);

	/*
	 * handling of various loads (based on EAS2.4):
	 *
	 * ldX.acq (ordered load):
	 *	- acquire semantics would have been used, so force fence instead.
	 *
	 * ldX.c.clr (check load and clear):
	 *	- if we get to this handler, it's because the entry was not in the ALAT.
	 *	  Therefore the operation reverts to a normal load
	 *
	 * ldX.c.nc (check load no clear):
	 *	- same as previous one
	 *
	 * ldX.c.clr.acq (ordered check load and clear):
	 *	- same as above for c.clr part. The load needs to have acquire semantics. So
	 *	  we use the fence semantics which is stronger and thus ensures correctness.
	 *
	 * ldX.a (advanced load):
	 *	- suppose ldX.a r1=[r3]. If we get to the unaligned trap it's because the
	 *	  address doesn't match requested size alignement. This means that we would
	 *	  possibly need more than one load to get the result.
	 *
	 *	  The load part can be handled just like a normal load, however the difficult
	 *	  part is to get the right thing into the ALAT. The critical piece of information
	 *	  in the base address of the load & size. To do that, a ld.a must be executed,
	 *	  clearly any address can be pushed into the table by using ld1.a r1=[r3]. Now
	 *	  if we use the same target register, we will be okay for the check.a instruction.
	 *	  If we look at the store, basically a stX [r3]=r1 checks the ALAT  for any entry
	 *	  which would overlap within [r3,r3+X] (the size of the load was store in the
	 *	  ALAT). If such an entry is found the entry is invalidated. But this is not good
	 *	  enough, take the following example:
	 *		r3=3
	 *		ld4.a r1=[r3]
	 *
	 *	  Could be emulated by doing:
	 *		ld1.a r1=[r3],1
	 *		store to temporary;
	 *		ld1.a r1=[r3],1
	 *		store & shift to temporary;
	 *		ld1.a r1=[r3],1
	 *		store & shift to temporary;
	 *		ld1.a r1=[r3]
	 *		store & shift to temporary;
	 *		r1=temporary
	 *
	 *	  So int this case, you would get the right value is r1 but the wrong info in
	 *	  the ALAT.  Notice that you could do it in reverse to finish with address 3
	 *	  but you would still get the size wrong.  To get the size right, one needs to
	 *	  execute exactly the same kind of load. You could do it from a aligned
	 *	  temporary location, but you would get the address wrong.
	 *
	 *	  So no matter what, it is not possible to emulate an advanced load
	 *	  correctly. But is that really critical ?
	 *
	 *
	 *	  Now one has to look at how ld.a is used, one must either do a ld.c.* or
	 *	  chck.a.* to reuse the value stored in the ALAT. Both can "fail" (meaning no
	 *	  entry found in ALAT), and that's perfectly ok because:
	 *
	 *		- ld.c.*, if the entry is not present a  normal load is executed
	 *		- chk.a.*, if the entry is not present, execution jumps to recovery code
	 *
	 *	  In either case, the load can be potentially retried in another form.
	 *
	 *	  So it's okay NOT to do any actual load on an unaligned ld.a. However the ALAT
	 *	  must be invalidated for the register (so that's chck.a.*,ld.c.* don't pick up
	 *	  a stale entry later) The register base update MUST also be performed.
	 *
	 *	  Now what is the content of the register and its NaT bit in the case we don't
	 *	  do the load ?  EAS2.4, says (in case an actual load is needed)
	 *
	 *		- r1 = [r3], Nat = 0 if succeeds
	 *		- r1 = 0 Nat = 0 if trying to access non-speculative memory
	 *
	 *	  For us, there is nothing to do, because both ld.c.* and chk.a.* are going to
	 *	  retry and thus eventually reload the register thereby changing Nat and
	 *	  register content.
	 */

	/*
	 * when the load has the .acq completer then
	 * use ordering fence.
	 */
	if (ld.x6_op == 0x5 || ld.x6_op == 0xa)
		mb();

	/*
	 * invalidate ALAT entry in case of advanced load
	 */
	if (ld.x6_op == 0x2)
		invala_gr(ld.r1);

	return 0;
}

static int
emulate_store_int (unsigned long ifa, load_store_t ld, struct pt_regs *regs)
{
	unsigned long r2;
	unsigned int len = 1 << ld.x6_sz;

	/*
	 * if we get to this handler, Nat bits on both r3 and r2 have already
	 * been checked. so we don't need to do it
	 *
	 * extract the value to be stored
	 */
	getreg(ld.imm, &r2, 0, regs);

	/*
	 * we rely on the macros in unaligned.h for now i.e.,
	 * we let the compiler figure out how to read memory gracefully.
	 *
	 * We need this switch/case because the way the inline function
	 * works. The code is optimized by the compiler and looks like
	 * a single switch/case.
	 */
	DPRINT("st%d [%lx]=%lx\n", len, ifa, r2);

	if (len != 2 && len != 4 && len != 8) {
		DPRINT("unknown size: x6=%d\n", ld.x6_sz);
		return -1;
	}

	/* this assumes little-endian byte-order: */
	if (copy_to_user((void *) ifa, &r2, len))
		return -1;

	/*
	 * stX [r3]=r2,imm(9)
	 *
	 * NOTE:
	 * ld.r3 can never be r0, because r0 would not generate an
	 * unaligned access.
	 */
	if (ld.op == 0x5) {
		unsigned long imm;

		/*
		 * form imm9: [12:6] contain first 7bits
		 */
		imm = ld.x << 7 | ld.r1;
		/*
		 * sign extend (8bits) if m set
		 */
		if (ld.m) imm |= SIGN_EXT9;
		/*
		 * ifa == r3 (NaT is necessarily cleared)
		 */
		ifa += imm;

		DPRINT("imm=%lx r3=%lx\n", imm, ifa);

		setreg(ld.r3, ifa, 0, regs);
	}
	/*
	 * we don't have alat_invalidate_multiple() so we need
	 * to do the complete flush :-<<
	 */
	ia64_invala();

	/*
	 * stX.rel: use fence instead of release
	 */
	if (ld.x6_op == 0xd)
		mb();

	return 0;
}

/*
 * floating point operations sizes in bytes
 */
static const unsigned char float_fsz[4]={
	10, /* extended precision (e) */
	8,  /* integer (8)            */
	4,  /* single precision (s)   */
	8   /* double precision (d)   */
};

static inline void
mem2float_extended (struct ia64_fpreg *init, struct ia64_fpreg *final)
{
	__asm__ __volatile__ ("ldfe f6=[%0];; stf.spill [%1]=f6"
			      :: "r"(init), "r"(final) : "f6","memory");
}

static inline void
mem2float_integer (struct ia64_fpreg *init, struct ia64_fpreg *final)
{
	__asm__ __volatile__ ("ldf8 f6=[%0];; stf.spill [%1]=f6"
			      :: "r"(init), "r"(final) : "f6","memory");
}

static inline void
mem2float_single (struct ia64_fpreg *init, struct ia64_fpreg *final)
{
	__asm__ __volatile__ ("ldfs f6=[%0];; stf.spill [%1]=f6"
			      :: "r"(init), "r"(final) : "f6","memory");
}

static inline void
mem2float_double (struct ia64_fpreg *init, struct ia64_fpreg *final)
{
	__asm__ __volatile__ ("ldfd f6=[%0];; stf.spill [%1]=f6"
			      :: "r"(init), "r"(final) : "f6","memory");
}

static inline void
float2mem_extended (struct ia64_fpreg *init, struct ia64_fpreg *final)
{
	__asm__ __volatile__ ("ldf.fill f6=[%0];; stfe [%1]=f6"
			      :: "r"(init), "r"(final) : "f6","memory");
}

static inline void
float2mem_integer (struct ia64_fpreg *init, struct ia64_fpreg *final)
{
	__asm__ __volatile__ ("ldf.fill f6=[%0];; stf8 [%1]=f6"
			      :: "r"(init), "r"(final) : "f6","memory");
}

static inline void
float2mem_single (struct ia64_fpreg *init, struct ia64_fpreg *final)
{
	__asm__ __volatile__ ("ldf.fill f6=[%0];; stfs [%1]=f6"
			      :: "r"(init), "r"(final) : "f6","memory");
}

static inline void
float2mem_double (struct ia64_fpreg *init, struct ia64_fpreg *final)
{
	__asm__ __volatile__ ("ldf.fill f6=[%0];; stfd [%1]=f6"
			      :: "r"(init), "r"(final) : "f6","memory");
}

static int
emulate_load_floatpair (unsigned long ifa, load_store_t ld, struct pt_regs *regs)