5i, ki, vi, qi – instruction simulators


vi [ textfile ]
vi pid
5i [ textfile ]
5i pid
ki [ textfile ]
ki pid
qi [ textfile ]
qi pid


Vi simulates the execution of a MIPS binary in a Plan 9 environment. It has two main uses: as a debugger and as a statistics gatherer. Programs running under vi execute about two hundred times slower than normalbut faster than single stepping under db. 5i, ki, and qi are similar to vi but interpret ARM, SPARC, and PowerPC binaries. The following discussion refers to vi but applies to the others as well.

Vi will simulate the execution of a named textfile. It will also make a copy of an existing process with process id pid and simulate its continuation.

As a debugger vi offers more complete information than db(1). Tracing can be performed at the level of instructions, system calls, or function calls. Vi allows breakpoints to be triggered when specified addresses in memory are accessed. A report of instruction counts, load delay fills and distribution is produced for each run. Vi simulates the CPU’s caches and MMU to assist the optimization of compilers and programs.

The command interface mirrors the interface to db; see db(1) for a detailed description. Data formats and addressing are compatible with db except for disassembly: vi offers only MIPS (db -mmipsco) mnemonics for machine instructions. Ki offers both Plan 9 and Sun SPARC formats.

Several extra commands allow extended tracing and printing of statistics:


The t command controls tracing. Zero cancels all tracing options.  


Enable instruction tracing  


Enable call tracing  


Enable system call tracing  


The i command prints statistics accumulated by all code run in this session.  


Print instruction counts and frequency.  


Print cycle profile.  


(Vi only) Print TLB and cache statistics.  


Print memory reference, working set and size statistics.  


Vi allows breakpoints to be set on any memory location. These breakpoints monitor when a location is accessed, read, written, or equals a certain value. For equality the compared value is the count (see db(1)) supplied to the command.  


/sys/src/cmd/vi etc.


nm(1), db(1)


The code generated by the compilers is well supported, but some unusual instructions are unimplemented. Some Plan 9 system calls such as rfork cause simulated traps. The floating point simulation makes assumptions about the interpreting machine’s floating point support. The floating point conversions performed by vi may cause a loss of precision.