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>
- MS-DOS 4.01 caused a stack overflow in the int15_function(). Now handle all
functions that simply return success in the ASM code. Fixes SF bug #1439.
- Added two delay loops in keyboard_init(). Fixes SF bug #1438.
- Now using the new VBE read and write apertures when setting the banks for
full scrolling support.
- Added TTY support flags for all 8-bpp VBE mode entries.
- Bochs VBE: enable 32k bank granularity mode.
- Fixed general 'scroll down' bug in graphics modes.
- Code optimizations: some VBE and VGA functions rewritten in assembler.
- Banshee: added 'write character' support for 8 bpp modes.
- Banshee / Cirrus: report TTY support for 8 bpp VBE modes.
- FIXME: Banshee scroll code works for 'scroll up' only.
- TODO: TTY support for the Bochs VBE adapter.
- Added initial version of the VGABIOS for Voodoo Banshee adapters.
- Several code optimizations to reduce binary size.
NOTE #1: Banshee version has no VBE support yet.
NOTE #2: Banshee binary uses PCI ID for Banshee PCI and Bochs temporarily
modifies the PCI data for Voodoo3 and AGP models.
- Disable i/o and memory access in PCI command register before probing and
setting up base addresses and re-enable it when complete for selected device.
- Legacy BIOS should not enable busmaster function in PCI init.
- Use 'iasl' for building ACPI table if present.
- Use the release date from README file for the BIOS_BUILD_DATE.
- Added Bochs VERSION string to the BIOS banner.
- Fixed the rombios32 delay loop for QEMU build.
- Improvement for rombios32.ld.
