3b1emu / changelog

More bus error fixes for FreeBee

• Mon, 14 Jan 2013 09:22:12 +0000
• by Philip Pemberton <philpem@philpem.me.uk> [Mon, 14 Jan 2013 09:22:12 +0000] rev 118
• More bus error fixes for FreeBee
  
  I have fixed two more bus error handling bugs in FreeBee. First, the CPU core was executing the instruction regardless of whether a bus error occurs when fetching the opcode (which caused it to execute a bogus instruction in such cases). The other one was related to one of my previous fixes - the jump to the bus error vector was at the beginning of the main loop, so it wouldn't be called immediately after the bus error occurred if the timeslot expired, causing the return address to be off.
  
  With these fixes, Unix now runs enough to get into userspace and run the install script (it is also possible to break out and get a shell prompt). However, many commands segfault semi-randomly (or more specifically, it seems that some child processes forked by the shell might be segfaulting before they can exec the command program), so installing the system isn't possible yet. I am not sure exactly what the bug is, but it seems to be related to some function in the shell returning null when the code calling it is assuming that it won't. What the function is, or why it is returning null, I'm not sure (the shell is built without the shared libc and is stripped, making identifying the function harder). I suspect that the function might be in libc, but that is hard to tell.
  
  Author: Andrew Warkentin <andreww591 gmail com>

show LED state change only if SHOW_LEDS is defined

• Tue, 20 Nov 2012 23:31:03 +0000
• by Philip Pemberton <philpem@philpem.me.uk> [Tue, 20 Nov 2012 23:31:03 +0000] rev 117
• show LED state change only if SHOW_LEDS is defined

Add support for MSR2, partial reads from GENSTAT

• Sat, 17 Nov 2012 22:26:53 +0000
• by Philip Pemberton <philpem@philpem.me.uk> [Sat, 17 Nov 2012 22:26:53 +0000] rev 116
• Add support for MSR2, partial reads from GENSTAT
  
  * GENSTAT is sometimes read in 8bit mode. Handle this properly.
  
  * Add support for the MSR2 register (additional HDD head select bit only at
  the moment)

wd2010: use LOGS when logging unformatted strings

• Sat, 17 Nov 2012 22:15:23 +0000
• by Philip Pemberton <philpem@philpem.me.uk> [Sat, 17 Nov 2012 22:15:23 +0000] rev 115
• wd2010: use LOGS when logging unformatted strings

Fix bit masking logic in 'dead bus' return

• Sat, 17 Nov 2012 22:14:09 +0000
• by Philip Pemberton <philpem@philpem.me.uk> [Sat, 17 Nov 2012 22:14:09 +0000] rev 114
• Fix bit masking logic in 'dead bus' return
  
  In some cases (e.g. 16bit reads) a bad 'idle bus' return may be provided.
  Promote the '1' to unsigned long prior to left-shifting it.

ACCESS_CHECK_RD should return the right number of bits!

• Sat, 17 Nov 2012 21:28:48 +0000
• by Philip Pemberton <philpem@philpem.me.uk> [Sat, 17 Nov 2012 21:28:48 +0000] rev 113
• ACCESS_CHECK_RD should return the right number of bits!
  
  If the ACCESS_CHECK_RD() macro detects a page fault, it always returns a
  32-bit error response ("all bus pins high"). Musashi really doesn't like it
  when we pass in a 32-bit value when it expects a 16-bit one!