Plan 9 - man page for vi (plan9 section 1)
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vi, ki, xi - instruction simulators
vi [ textfile ]
ki [ textfile ]
xi [ textfile ]
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 normal--but faster than single stepping under db. Ki and xi
are similar to vi but interpret SPARC and ATT3210 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 exist-
ing 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
Several extra commands allow extended tracing and printing of statistics:
The t command controls tracing. Zero cancels all tracing options.
i Enable instruction tracing
c Enable call tracing
s Enable system call tracing
The i command prints statistics accumulated by all code run in this session.
i Print instruction counts and frequency.
p Print cycle profile.
t (Vi only) Print TLB and cache statistics.
s 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 equal-
ity the compared value is the count (see db(1)) supplied to the command.
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 float-
ing 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.
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