[ #433759 ] virtual address checks can overflow
> Bochs has been crashing in some cases when you try to access data which
> overlaps the segment limit, when the segment limit is near the 32-bit
> boundary. The example that came up a few times is reading/writing 4 bytes
> starting at 0xffffffff when the segment limit was 0xffffffff. The
> condition used to compare offset+length-1 with the limit, but
> offset+length-1 was overflowing so the comparison went wrong. This patch
> changes the condition so that it supports all segment limits except for
> sizes 0,1,2,3 bytes. Dave and I figured that these sizes would not be
> needed, while size 0xffffffff is used quite a lot.
has run. This ensures that the prev_eip and prev_esp that is used
for tracing and breakpoint checks is correct even in the cycle after
an interrupt or trap.
> This patch fixes a number of debugger problems.
> - with trace-on, simulation time would pass 5x faster than usual, so
> interrupts and other timed events would happen at different times
> - with trace-on, breakpoints were ignored
> - with trace-on, control-C would not stop the processor and return to the
> debugger.
>
> This patch changes the execution quantum for the debugger to 1, which means
> that cpu_loop is asked to do one instruction at a time. This may cause
> bochs with the debugger to be slower than before.
>
> I haven't tested without the debugger yet, so I don't know if the timing
> of events matches or not.
in an output format similar to gdb (when you do info all-registers).
Also, if you do "info all" you get the CPU registers and the FPU
registers.
- added bx_cpu_c method called fpu_print_regs, which is implemented
in wmFPUemu_glue.cc
by thomas.petazzoni@meridon.com. Bryce introduced this bug in
revision 1.9 when split the code into separate #ifdefs for single
CPU and multiple CPU. Comments on the patch are:
> The following patch addresses a bug concerning the exception 1 (debug)
> which is being raised during HALT under certain conditions. It
> appears only on recent versions (1.2.1 or last CVS), and not on
> version 2000-0104.
BX_SUPPORT_APIC were used. To follow the pattern used by other
names like this, I changed them all to BX_SUPPORT_APIC.
Thanks to Tom Lindström for chasing this down!
BX_CPU_C bx_cpu;
BX_MEM_C bx_mem;
and when more than one processor, use
BX_CPU_C *bx_cpu_array[BX_SMP_PROCESSORS];
BX_MEM_C *bx_mem_array[BX_ADDRESS_SPACES];
The changeover is controlled by BX_SMP_PROCESSORS, but there are only
a few code changes since nearly all code uses the BX_CPU(n) and BX_MEM(n)
macros.
- This turns out to make a 10% speed difference! With this revision,
the CVS version now gets 95% of the performance of the 3/25/2000
snapshot, which I've been using as my baseline.
is the first attempt to regain the performance of pre-SMP bochs
(1.1.2). When simulating only one processor, stay in cpu_loop forever
as pre-SMP versions did. The overhead of returning from cpu_loop over
and over was slowing us down.
tries to fix it. The shortcuts to register names such as AX and DL are
#defines in cpu/cpu.h, and they are defined in terms of BX_CPU_THIS_PTR.
When BX_USE_CPU_SMF=1, this works fine. (This is what bochs used for
a long time, and nobody used the SMF=0 mode at all.) To make SMP bochs
work, I had to get SMF=0 mode working for the CPU so that there could
be an array of cpus.
When SMF=0 for the CPU, BX_CPU_THIS_PTR is defined to be "this->" which
only works within methods of BX_CPU_C. Code outside of BX_CPU_C must
reference BX_CPU(num) instead.
- to try to enforce the correct use of AL/AX/DL/etc. shortcuts, they are
now only #defined when "NEED_CPU_REG_SHORTCUTS" is #defined. This is
only done in the cpu/*.cc code.
in BRANCH-smp-bochs revisions.
- The general task was to make multiple CPU's which communicate
through their APICs. So instead of BX_CPU and BX_MEM, we now have
BX_CPU(x) and BX_MEM(y). For an SMP simulation you have several
processors in a shared memory space, so there might be processors
BX_CPU(0..3) but only one memory space BX_MEM(0). For cosimulation,
you could have BX_CPU(0) with BX_MEM(0), then BX_CPU(1) with
BX_MEM(1). WARNING: Cosimulation is almost certainly broken by the
SMP changes.
- to simulate multiple CPUs, you have to give each CPU time to execute
in turn. This is currently implemented using debugger guards. The
cpu loop steps one CPU for a few instructions, then steps the
next CPU for a few instructions, etc.
- there is some limited support in the debugger for two CPUs, for
example printing information from each CPU when single stepping.
sourceforge patch #423726. He writes:
> you'll find as attachment a little patch which make
> bochs support the double fault. currently, when 2 pages
> fault occur, bochs does not generate a double fault (as
> the Intel documentation says) but do
> generate a other page fault, which make a triple fault,
> and bochs will exit.
>
> this very little patch make bochs support this double
> fault, which is
> used in our OS in order to dynamically increse kernel
> level stacks.
To see the commit logs for this use either cvsweb or
cvs update -r BRANCH-io-cleanup and then 'cvs log' the various files.
In general this provides a generic interface for logging.
logfunctions:: is a class that is inherited by some classes, and also
. allocated as a standalone global called 'genlog'. All logging uses
. one of the ::info(), ::error(), ::ldebug(), ::panic() methods of this
. class through 'BX_INFO(), BX_ERROR(), BX_DEBUG(), BX_PANIC()' macros
. respectively.
.
. An example usage:
. BX_INFO(("Hello, World!\n"));
iofunctions:: is a class that is allocated once by default, and assigned
as the iofunction of each logfunctions instance. It is this class that
maintains the file descriptor and other output related code, at this
point using vfprintf(). At some future point, someone may choose to
write a gui 'console' for bochs to which messages would be redirected
simply by assigning a different iofunction class to the various logfunctions
objects.
More cleanup is coming, but this works for now. If you want to see alot
of debugging output, in main.cc, change onoff[LOGLEV_DEBUG]=0 to =1.
Comments, bugs, flames, to me: todd@fries.net
