1 /*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21
22 /*
23 * Copyright 2008 Sun Microsystems, Inc. All rights reserved.
24 * Use is subject to license terms.
25 */
26
27 /*
28 * Copyright (c) 1990, 1991 UNIX System Laboratories, Inc.
29 * Copyright (c) 1988 AT&T
30 * All Rights Reserved
31 */
32
33 /*
34 * Copyright 2023 Oxide Computer Company
35 */
36
37 /*
38 * Establish the default settings for the floating-point state for a C language
39 * program:
40 * rounding mode -- round to nearest default by OS,
41 * exceptions enabled -- all masked
42 * sticky bits -- all clear by default by OS.
43 * precision control -- double extended
44 * Set _fp_hw according to what floating-point hardware is available.
45 * Set _sse_hw according to what SSE hardware is available.
46 * Set __flt_rounds according to the rounding mode.
47 */
48
49 #pragma weak _fpstart = __fpstart
50
51 #include "lint.h"
52 #include <sys/types.h>
53 #include <sys/sysi86.h> /* for SI86FPHW/SI86FPSTART definitions */
54 #include <sys/fp.h> /* for FPU_CW_INIT and SSE_MXCSR_INIT */
55 #include <upanic.h>
56
57 extern int __fltrounds();
58
59 int _fp_hw; /* default: bss: 0 == no hardware */
60 int _sse_hw; /* default: bss: 0 == no sse */
61 int __flt_rounds; /* ANSI rounding mode */
62
63 #define UPANIC_MSG "32-bit FPU init failed!"
64
65 void
__fpstart()66 __fpstart()
67 {
68 /*
69 * query OS for HW status and ensure the x87 and (optional)
70 * SSE control words are (will be) set correctly.
71 */
72 if ((_sse_hw = sysi86(SI86FPSTART,
73 &_fp_hw, FPU_CW_INIT, SSE_MXCSR_INIT)) == -1) {
74 /*
75 * Because the system only supports a 64-bit kernel, the above
76 * should always work (we assume it does in 64-bit libc). If it
77 * should fail, we upanic. Note, because the FPU state is
78 * unknown, we use a static message below and don't rely upon
79 * strlen(), but rather compile time lengths.
80 */
81 upanic(UPANIC_MSG, sizeof (UPANIC_MSG));
82 }
83
84 /*
85 * At this point the x87 fp environment that has been (or more
86 * hopefully, will be) established by the kernel is:
87 *
88 * affine infinity 0x1000
89 * round to nearest 0x0000
90 * 64-bit doubles 0x0300
91 * precision, underflow, overflow, zero-divide, denorm, invalid masked
92 * 0x003f
93 *
94 * which conforms to the 4th edition i386 ABI definition.
95 *
96 * Additionally, if we have SSE hardware, we've also masked all
97 * the same traps, and have round to nearest.
98 */
99
100 __flt_rounds = 1; /* ANSI way of saying round-to-nearest */
101 }
102