ffc722f4e8
by Michele Giacomone
Detailed description:
-Observed issues
Due to some limitations only dates between 1980 and 2038 can be
used in a reliable way.
Also, bochs incorrectly assumes a linear correspondence between
the data returned by the <time.h> functions localtime() and
mktime(), and isn't setting the latter properly.
Bochs keeps its internal time value dependent to these functions
after setup, assuming that their internal settings won't change
on the go - which is not the case.
In my OS, and in my timezone, this leads to incorrect startup values
for 5 months each year and unreliable values if the simulation is
kept going for a long time. (a feedback between localtime() and
mktime() is created which keeps shifting back the time)
Also, the RTC simulation is not realistic since the clock fixes
itself across DST changes, without updating any DST related flag,
a behavior that no guest OS expects.
-Proposed fix
This is implemented in such way that no bochs' previous behavior
is changed, a part from the broken ones, with legacy in mind
== the user can keep using bochs exactly as before knowing nothing
of this patch
+Make the internal s.timeval variable a Bit64s, so it can fit all
values that the cmos can correctly represent, reported below:
MIN setting -62167219200 => 0000/01/01 SAT 0:00:00
MAX BCD setting 253402300799 => 9999/12/31 FRI 23:59:59
MAX BIN setting 745690751999 => 25599/12/31 FRI 23:59:59
And then fix each reference to these so it can handle such values
And make bochs correctly wrap around for under/overflows, so that
only the most significant bits of the century are lost.
+Do the same thing to the bochs time0 parameter, so all the above
values can be chosen at startup (despite being now legal values,
1 and 2 will still be treated as "local" and "utc"). Note that
normally only BCD settings are valid since bochs' CMOS defaults
to such operating mode - the only way to use the binary range
is by loading a cmos memory map.
+Make the internal s.timeval variable independent from external
factors. This means providing a small set of time handling
functions, contained in "iodev/utctime.h", which must work in
any environment in which bochs compiles, accessing no external
resource. This also means that after startup, s.timeval will only
be changed internally, and no call to the OS time functions will
be made.
+Make the internal s.timeval variable timezone independent, to
have a linear correlation between its values and valid CMOS
settings. To make it easier, s.timeval is gonna be treated as
if the current timezone was UTC: so,
- if the user selects UTC as time0, s.timeval will become current
time(NULL)
- if the user selects localtime, s.timeval will be computed as
the value which will display the same broken down time as
localtime(&now)
- if the user inputs a time formatted string the proper s.timeval
to displayed will be easily calculated,
- if the user inputs a starting time value, s.timeval will be
computed as the value which will display the same broken down
time as localtime(&user_input) to ensure the same operation as
before.
A "tz=utc" is displayed when bochs prints out the current time
value, to warn users about the difference in meaning between the
internally kept time value and the value they can set through
the "time0=" parameter. This might be changed to communicate
instead the time value they can input to get the same setting,
but performing such calculation (except for the startup time)
suffers from all the mktime()/localtime() problems listed above
so I did not do it.
The range of "time0" is automatically adjusted so all users in
all time zones can set any legal value despite "time0=" having a
local meaning.
A thorough explanation of what I did and why can be found in the
"iodev/utctime.h" library header.
---------
Co-authored-by: Stanislav Shwartsman <sshwarts@users.sourceforge.net>
Co-authored-by: Volker Ruppert <Volker.Ruppert@t-online.de>
105 lines
3.1 KiB
C++
105 lines
3.1 KiB
C++
/////////////////////////////////////////////////////////////////////////
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// $Id$
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/////////////////////////////////////////////////////////////////////////
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//
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// Copyright (C) 2002-2023 The Bochs Project
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//
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// This library is free software; you can redistribute it and/or
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// modify it under the terms of the GNU Lesser General Public
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// License as published by the Free Software Foundation; either
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// version 2 of the License, or (at your option) any later version.
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//
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public
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// License along with this library; if not, write to the Free Software
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// Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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//
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#ifndef BX_IODEV_CMOS_H
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#define BX_IODEV_CMOS_H
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#if BX_USE_CMOS_SMF
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# define BX_CMOS_SMF static
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# define BX_CMOS_THIS theCmosDevice->
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#else
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# define BX_CMOS_SMF
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# define BX_CMOS_THIS this->
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#endif
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class bx_cmos_c : public bx_cmos_stub_c {
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public:
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bx_cmos_c();
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virtual ~bx_cmos_c();
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virtual void init(void);
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virtual void checksum_cmos(void);
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virtual void reset(unsigned type);
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virtual void save_image(void);
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virtual void register_state(void);
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virtual void after_restore_state(void);
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#if BX_DEBUGGER
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virtual void debug_dump(int argc, char **argv);
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#endif
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virtual Bit32u get_reg(Bit8u reg) {
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return s.reg[reg];
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}
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virtual void set_reg(Bit8u reg, Bit32u val) {
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s.reg[reg] = val;
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}
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virtual Bit64s get_timeval() {
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return s.timeval;
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}
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virtual void enable_irq(bool enabled) {
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s.irq_enabled = enabled;
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}
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struct {
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int periodic_timer_index;
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Bit32u periodic_interval_usec;
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int one_second_timer_index;
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int uip_timer_index;
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Bit64s timeval; //Changed this from time_t to Bit64s - this struct seems to not be referenced ouside of this class despite being public
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Bit8u cmos_mem_address;
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Bit8u cmos_ext_mem_addr;
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bool timeval_change;
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bool rtc_mode_12hour;
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bool rtc_mode_binary;
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bool rtc_sync;
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bool irq_enabled;
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Bit8u reg[256];
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Bit8u max_reg;
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bool use_image;
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} s; // state information
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private:
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static Bit32u read_handler(void *this_ptr, Bit32u address, unsigned io_len);
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static void write_handler(void *this_ptr, Bit32u address, Bit32u value, unsigned io_len);
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#if !BX_USE_CMOS_SMF
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Bit32u read(Bit32u address, unsigned io_len);
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void write(Bit32u address, Bit32u value, unsigned len);
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#endif
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public:
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static void periodic_timer_handler(void *);
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static void one_second_timer_handler(void *);
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static void uip_timer_handler(void *);
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BX_CMOS_SMF void periodic_timer(void);
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BX_CMOS_SMF void one_second_timer(void);
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BX_CMOS_SMF void uip_timer(void);
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private:
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BX_CMOS_SMF void update_clock(void);
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BX_CMOS_SMF void update_timeval(void);
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BX_CMOS_SMF void CRA_change(void);
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};
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#endif
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