Tue, 15 Nov 2011 10:12:37 +0000
[musashi] Fix handling of bus errors
Patch-Author: Andrew Warkentin <andreww591!gmail>
Patch-MessageID: <4EC200CE.2020304@gmail.com>
I have fixed the first page fault test failure in FreeBee (the page fault test now hangs rather than errors out, because it is trying to read from the hard drive to test DMA page faults).
There were actually two bugs (the first bug was masking the second one).
First, the ancient version of Musashi that you used is unable to properly resume from bus errors that happen in the middle of certain instructions (some instructions are fetched in stages, with the PC being advanced to each part of the instruction, so basically what happens is the CPU core attempts to read the memory location referenced by the first operand, the bus error occurs, causing the PC to jump to the exception vector, but the faulting instruction is still in the middle of being fetched, so the PC is then advanced past the beginning of the exception handler). I fixed this by delaying the jump to the bus error vector until after the faulting instruction finishes.
The second bug is simpler - you had the UDS and LDS bits in BSR0 inverted (they are supposed to be active low).
1 #ifndef SIM__HEADER
2 #define SIM__HEADER
4 unsigned int m68k_read_memory_8(unsigned int address);
5 unsigned int m68k_read_memory_16(unsigned int address);
6 unsigned int m68k_read_memory_32(unsigned int address);
7 void m68k_write_memory_8(unsigned int address, unsigned int value);
8 void m68k_write_memory_16(unsigned int address, unsigned int value);
9 void m68k_write_memory_32(unsigned int address, unsigned int value);
10 void cpu_pulse_reset(void);
11 void cpu_set_fc(unsigned int fc);
12 int cpu_irq_ack(int level);
14 #endif /* SIM__HEADER */