25eed6867e
libi386's time(), caused by a qemu bug. The bug might
be present in other BIOSes, too.
qemu either does not simulate the AT RTC correctly or
has a broken BIOS 1A/02 implementation, and will return
an incorrect value if the RTC is read while it is being
updated.
The effect is worsened by the fact that qemu's INT 15/86
function ("wait" a.k.a. usleep) is non-implmeneted or
broken and returns immediately, causing beastie.4th to
spin in a tight loop calling the "read RTC" function
millions of times, triggering the problem quickly.
Therefore, we keep reading the BIOS value until we get
the same result twice. This change fixes beastie.4th's
countdown under qemu.
Approved by: des (mentor)
108 lines
3.0 KiB
C
108 lines
3.0 KiB
C
/*-
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* Copyright (c) 1998 Michael Smith <msmith@freebsd.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <stand.h>
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#include <btxv86.h>
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#include "bootstrap.h"
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#include "libi386.h"
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static int bios_seconds(void);
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/*
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* Return the BIOS time-of-day value.
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*
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* XXX uses undocumented BCD support from libstand.
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*/
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static int
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bios_seconds(void)
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{
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int hr, minute, sec;
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v86.ctl = 0;
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v86.addr = 0x1a; /* int 0x1a, function 2 */
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v86.eax = 0x0200;
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v86int();
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hr = bcd2bin((v86.ecx & 0xff00) >> 8); /* hour in %ch */
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minute = bcd2bin(v86.ecx & 0xff); /* minute in %cl */
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sec = bcd2bin((v86.edx & 0xff00) >> 8); /* second in %dh */
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return (hr * 3600 + minute * 60 + sec);
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}
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/*
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* Return the time in seconds since the beginning of the day.
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*
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* Some BIOSes (notably qemu) don't correctly read the RTC
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* registers in an atomic way, sometimes returning bogus values.
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* Therefore we "debounce" the reading by accepting it only when
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* we got two identical values in succession.
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*
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* If we pass midnight, don't wrap back to 0.
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*/
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time_t
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time(time_t *t)
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{
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static time_t lasttime;
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time_t now, check;
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int try;
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try = 0;
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check = bios_seconds();
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do {
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now = check;
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check = bios_seconds();
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} while (now != check && ++try < 1000);
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if (now < lasttime)
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now += 24 * 3600;
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lasttime = now;
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if (t != NULL)
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*t = now;
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return(now);
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}
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/*
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* Use the BIOS Wait function to pause for (period) microseconds.
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*
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* Resolution of this function is variable, but typically around
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* 1ms.
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*/
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void
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delay(int period)
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{
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v86.ctl = 0;
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v86.addr = 0x15; /* int 0x15, function 0x86 */
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v86.eax = 0x8600;
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v86.ecx = period >> 16;
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v86.edx = period & 0xffff;
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v86int();
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}
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