unaligned.c

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{
	struct ia64_fpreg fpr_init[2];
	struct ia64_fpreg fpr_final[2];
	unsigned long len = float_fsz[ld.x6_sz];

	/*
	 * fr0 & fr1 don'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.
	 */

	/*
	 * make sure we get clean buffers
	 */
	memset(&fpr_init, 0, sizeof(fpr_init));
	memset(&fpr_final, 0, sizeof(fpr_final));

	/*
	 * ldfpX.a: we don't try to emulate anything but we must
	 * invalidate the ALAT entry and execute updates, if any.
	 */
	if (ld.x6_op != 0x2) {
		/*
		 * This assumes little-endian byte-order.  Note that there is no "ldfpe"
		 * instruction:
		 */
		if (copy_from_user(&fpr_init[0], (void *) ifa, len)
		    || copy_from_user(&fpr_init[1], (void *) (ifa + len), len))
			return -1;

		DPRINT("ld.r1=%d ld.imm=%d x6_sz=%d\n", ld.r1, ld.imm, ld.x6_sz);
		DDUMP("frp_init =", &fpr_init, 2*len);
		/*
		 * XXX fixme
		 * Could optimize inlines by using ldfpX & 2 spills
		 */
		switch( ld.x6_sz ) {
			case 0:
				mem2float_extended(&fpr_init[0], &fpr_final[0]);
				mem2float_extended(&fpr_init[1], &fpr_final[1]);
				break;
			case 1:
				mem2float_integer(&fpr_init[0], &fpr_final[0]);
				mem2float_integer(&fpr_init[1], &fpr_final[1]);
				break;
			case 2:
				mem2float_single(&fpr_init[0], &fpr_final[0]);
				mem2float_single(&fpr_init[1], &fpr_final[1]);
				break;
			case 3:
				mem2float_double(&fpr_init[0], &fpr_final[0]);
				mem2float_double(&fpr_init[1], &fpr_final[1]);
				break;
		}
		DDUMP("fpr_final =", &fpr_final, 2*len);
		/*
		 * XXX fixme
		 *
		 * A possible optimization would be to drop fpr_final and directly
		 * use the storage from the saved context i.e., the actual final
		 * destination (pt_regs, switch_stack or thread structure).
		 */
		setfpreg(ld.r1, &fpr_final[0], regs);
		setfpreg(ld.imm, &fpr_final[1], regs);
	}

	/*
	 * Check for updates: only immediate updates are available for this
	 * instruction.
	 */
	if (ld.m) {
		/*
		 * the immediate is implicit given the ldsz of the operation:
		 * single: 8 (2x4) and for  all others it's 16 (2x8)
		 */
		ifa += len<<1;

		/*
		 * IMPORTANT:
		 * the fact that we force the NaT of r3 to zero is ONLY valid
		 * as long as we don't come here with a ldfpX.s.
		 * For this reason we keep this sanity check
		 */
		if (ld.x6_op == 1 || ld.x6_op == 3)
			printk(KERN_ERR __FUNCTION__": register update on speculative load pair, "
			       "error\n");

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

	/*
	 * Invalidate ALAT entries, if any, for both registers.
	 */
	if (ld.x6_op == 0x2) {
		invala_fr(ld.r1);
		invala_fr(ld.imm);
	}
	return 0;
}


static int
emulate_load_float (unsigned long ifa, load_store_t ld, struct pt_regs *regs)
{
	struct ia64_fpreg fpr_init;
	struct ia64_fpreg fpr_final;
	unsigned long len = float_fsz[ld.x6_sz];

	/*
	 * fr0 & fr1 don'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.
	 */

	/*
	 * make sure we get clean buffers
	 */
	memset(&fpr_init,0, sizeof(fpr_init));
	memset(&fpr_final,0, sizeof(fpr_final));

	/*
	 * ldfX.a we don't try to emulate anything but we must
	 * invalidate the ALAT entry.
	 * See comments in ldX for descriptions on how the various loads are handled.
	 */
	if (ld.x6_op != 0x2) {
		if (copy_from_user(&fpr_init, (void *) ifa, len))
			return -1;

		DPRINT("ld.r1=%d x6_sz=%d\n", ld.r1, ld.x6_sz);
		DDUMP("fpr_init =", &fpr_init, len);
		/*
		 * we only do something for x6_op={0,8,9}
		 */
		switch( ld.x6_sz ) {
			case 0:
				mem2float_extended(&fpr_init, &fpr_final);
				break;
			case 1:
				mem2float_integer(&fpr_init, &fpr_final);
				break;
			case 2:
				mem2float_single(&fpr_init, &fpr_final);
				break;
			case 3:
				mem2float_double(&fpr_init, &fpr_final);
				break;
		}
		DDUMP("fpr_final =", &fpr_final, len);
		/*
		 * XXX fixme
		 *
		 * A possible optimization would be to drop fpr_final and directly
		 * use the storage from the saved context i.e., the actual final
		 * destination (pt_regs, switch_stack or thread structure).
		 */
		setfpreg(ld.r1, &fpr_final, regs);
	}

	/*
	 * check for updates on any loads
	 */
	if (ld.op == 0x7 || ld.m)
		emulate_load_updates(ld.op == 0x7 ? UPD_IMMEDIATE: UPD_REG, ld, regs, ifa);

	/*
	 * invalidate ALAT entry in case of advanced floating point loads
	 */
	if (ld.x6_op == 0x2)
		invala_fr(ld.r1);

	return 0;
}


static int
emulate_store_float (unsigned long ifa, load_store_t ld, struct pt_regs *regs)
{
	struct ia64_fpreg fpr_init;
	struct ia64_fpreg fpr_final;
	unsigned long len = float_fsz[ld.x6_sz];

	/*
	 * make sure we get clean buffers
	 */
	memset(&fpr_init,0, sizeof(fpr_init));
	memset(&fpr_final,0, sizeof(fpr_final));

	/*
	 * 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
	 */
	getfpreg(ld.imm, &fpr_init, regs);
	/*
	 * during this step, we extract the spilled registers from the saved
	 * context i.e., we refill. Then we store (no spill) to temporary
	 * aligned location
	 */
	switch( ld.x6_sz ) {
		case 0:
			float2mem_extended(&fpr_init, &fpr_final);
			break;
		case 1:
			float2mem_integer(&fpr_init, &fpr_final);
			break;
		case 2:
			float2mem_single(&fpr_init, &fpr_final);
			break;
		case 3:
			float2mem_double(&fpr_init, &fpr_final);
			break;
	}
	DPRINT("ld.r1=%d x6_sz=%d\n", ld.r1, ld.x6_sz);
	DDUMP("fpr_init =", &fpr_init, len);
	DDUMP("fpr_final =", &fpr_final, len);

	if (copy_to_user((void *) ifa, &fpr_final, len))
		return -1;

	/*
	 * stfX [r3]=r2,imm(9)
	 *
	 * NOTE:
	 * ld.r3 can never be r0, because r0 would not generate an
	 * unaligned access.
	 */
	if (ld.op == 0x7) {
		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();

	return 0;
}

/*
 * Make sure we log the unaligned access, so that user/sysadmin can notice it and
 * eventually fix the program.  However, we don't want to do that for every access so we
 * pace it with jiffies.  This isn't really MP-safe, but it doesn't really have to be
 * either...
 */
static int
within_logging_rate_limit (void)
{
	static unsigned long count, last_time;

	if (jiffies - last_time > 5*HZ)
		count = 0;
	if (++count < 5) {
		last_time = jiffies;
		return 1;
	}
	return 0;

}

void
ia64_handle_unaligned (unsigned long ifa, struct pt_regs *regs)
{
	struct exception_fixup fix = { 0 };
	struct ia64_psr *ipsr = ia64_psr(regs);
	mm_segment_t old_fs = get_fs();
	unsigned long bundle[2];
	unsigned long opcode;
	struct siginfo si;
	union {
		unsigned long l;
		load_store_t insn;
	} u;
	int ret = -1;

	if (ia64_psr(regs)->be) {
		/* we don't support big-endian accesses */
		die_if_kernel("big-endian unaligned accesses are not supported", regs, 0);
		goto force_sigbus;
	}

	/*
	 * Treat kernel accesses for which there is an exception handler entry the same as
	 * user-level unaligned accesses.  Otherwise, a clever program could trick this
	 * handler into reading an arbitrary kernel addresses...
	 */
	if (!user_mode(regs)) {
#ifdef GAS_HAS_LOCAL_TAGS
		fix = search_exception_table(regs->cr_iip + ia64_psr(regs)->ri);
#else
		fix = search_exception_table(regs->cr_iip);
#endif
	}
	if (user_mode(regs) || fix.cont) {
		if ((current->thread.flags & IA64_THREAD_UAC_SIGBUS) != 0)
			goto force_sigbus;

		if (!(current->thread.flags & IA64_THREAD_UAC_NOPRINT)
		    && within_logging_rate_limit())
		{
			char buf[200];	/* comm[] is at most 16 bytes... */
			size_t len;

			len = sprintf(buf, "%s(%d): unaligned access to 0x%016lx, "
				      "ip=0x%016lx\n\r", current->comm, current->pid,
				      ifa, regs->cr_iip + ipsr->ri);
			/*
			 * Don't call tty_write_message() if we're in the kernel; we might
			 * be holding locks...
			 */
			if (user_mode(regs))
				tty_write_message(current->tty, buf);
			buf[len-1] = '\0';	/* drop '\r' */
			printk(KERN_WARNING "%s", buf);	/* watch for command names containing %s */
		}
	} else {
		if (within_logging_rate_limit())
			printk(KERN_WARNING "kernel unaligned access to 0x%016lx, ip=0x%016lx\n",
			       ifa, regs->cr_iip + ipsr->ri);
		set_fs(KERNEL_DS);
	}

	DPRINT("iip=%lx ifa=%lx isr=%lx (ei=%d, sp=%d)\n",
	       regs->cr_iip, ifa, regs->cr_ipsr, ipsr->ri, ipsr->it);

	if (__copy_from_user(bundle, (void *) regs->cr_iip, 16))
		goto failure;

	/*
	 * extract the instruction from the bundle given the slot number
	 */
	switch (ipsr->ri) {
	      case 0: u.l = (bundle[0] >>  5); break;
	      case 1: u.l = (bundle[0] >> 46) | (bundle[1] << 18); break;
	      case 2: u.l = (bundle[1] >> 23); break;
	}
	opcode = (u.l >> IA64_OPCODE_SHIFT) & IA64_OPCODE_MASK;

	DPRINT("opcode=%lx ld.qp=%d ld.r1=%d ld.imm=%d ld.r3=%d ld.x=%d ld.hint=%d "
	       "ld.x6=0x%x ld.m=%d ld.op=%d\n", opcode, u.insn.qp, u.insn.r1, u.insn.imm,
	       u.insn.r3, u.insn.x, u.insn.hint, u.insn.x6_sz, u.insn.m, u.insn.op);

	/*
	 * IMPORTANT:
	 * Notice that the switch statement DOES not cover all possible instructions
	 * that DO generate unaligned references. This is made on purpose because for some
	 * instructions it DOES NOT make sense to try and emulate the access. Sometimes it
	 * is WRONG to try and emulate. Here is a list of instruction we don't emulate i.e.,
	 * the program will get a signal and die:
	 *
	 *	load/store:
	 *		- ldX.spill
	 *		- stX.spill
	 *	Reason: RNATs are based on addresses
	 *
	 *	synchronization:
	 *		- cmpxchg
	 *		- fetchadd
	 *		- xchg
	 *	Reason: ATOMIC operations cannot be emulated properly using multiple
	 *	        instructions.
	 *
	 *	speculative loads:
	 *		- ldX.sZ
	 *	Reason: side effects, code must be ready to deal with failure so simpler
	 *		to let the load fail.
	 * ---------------------------------------------------------------------------------
	 * XXX fixme
	 *
	 * I would like to get rid of this switch case and do something
	 * more elegant.
	 */
	switch (opcode) {
	      case LDS_OP:
	      case LDSA_OP:
	      case LDS_IMM_OP:
	      case LDSA_IMM_OP:
	      case LDFS_OP:
	      case LDFSA_OP:
	      case LDFS_IMM_OP:
		/*
		 * The instruction will be retried with deferred exceptions turned on, and
		 * we should get Nat bit installed
		 *
		 * IMPORTANT: When PSR_ED is set, the register & immediate update forms
		 * are actually executed even though the operation failed. So we don't
		 * need to take care of this.
		 */
		DPRINT("forcing PSR_ED\n");
		regs->cr_ipsr |= IA64_PSR_ED;
		goto done;

	      case LD_OP:
	      case LDA_OP:
	      case LDBIAS_OP:
	      case LDACQ_OP:
	      case LDCCLR_OP:
	      case LDCNC_OP:
	      case LDCCLRACQ_OP:
	      case LD_IMM_OP:
	      case LDA_IMM_OP:
	      case LDBIAS_IMM_OP:
	      case LDACQ_IMM_OP:
	      case LDCCLR_IMM_OP:
	      case LDCNC_IMM_OP:
	      case LDCCLRACQ_IMM_OP:
		ret = emulate_load_int(ifa, u.insn, regs);
		break;

	      case ST_OP:
	      case STREL_OP:
	      case ST_IMM_OP:
	      case STREL_IMM_OP:
		ret = emulate_store_int(ifa, u.insn, regs);
		break;

	      case LDF_OP:
	      case LDFA_OP:
	      case LDFCCLR_OP:
	      case LDFCNC_OP:
	      case LDF_IMM_OP:
	      case LDFA_IMM_OP:
	      case LDFCCLR_IMM_OP:
	      case LDFCNC_IMM_OP:
		if (u.insn.x)
			ret = emulate_load_floatpair(ifa, u.insn, regs);
		else
			ret = emulate_load_float(ifa, u.insn, regs);
		break;

	      case STF_OP:
	      case STF_IMM_OP:
		ret = emulate_store_float(ifa, u.insn, regs);
		break;

	      default:
		goto failure;
	}
	DPRINT("ret=%d\n", ret);
	if (ret)
		goto failure;

	if (ipsr->ri == 2)
		/*
		 * given today's architecture this case is not likely to happen because a
		 * memory access instruction (M) can never be in the last slot of a
		 * bundle. But let's keep it for now.
		 */
		regs->cr_iip += 16;
	ipsr->ri = (ipsr->ri + 1) & 0x3;

	DPRINT("ipsr->ri=%d iip=%lx\n", ipsr->ri, regs->cr_iip);
  done:
	set_fs(old_fs);		/* restore original address limit */
	return;

  failure:
	/* something went wrong... */
	if (!user_mode(regs)) {
		if (fix.cont) {
			handle_exception(regs, fix);
			goto done;
		}
		die_if_kernel("error during unaligned kernel access\n", regs, ret);
		/* NOT_REACHED */
	}
  force_sigbus:
	si.si_signo = SIGBUS;
	si.si_errno = 0;
	si.si_code = BUS_ADRALN;
	si.si_addr = (void *) ifa;
	force_sig_info(SIGBUS, &si, current);
	goto done;
}