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Monitors.md

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Wizard Engine Monitors

The Wizard engine offers a variety of instrumentation and dynamic analysis monitors that perform dynamic analysis of Wasm programs. These monitors utilize Wizard's efficient probe mechanism that allows extensible event handling at desired points of program execution.

Usage

Monitors are enabled using the --monitor flag, which accepts multiple monitors with options.

wizeng --monitors=<monitor>{<opts>}[,<monitor>{<opts>}] <wasm files>

Each monitor supports its own optional arguments and modifiers:

<monitor>{<opt>=<modifier>[,<opt>=<modifier>]}

Here's an example usage:

% bin/wizeng --monitors=loops test/monitors/loop_monitor0.wasm
func #1:
   +8 ... +39 loop:   133
  +14 ... +27 loop:   399
  +45 ... +58 loop:   123

Options

When no optional arguments are provided, most monitors display summary information. For several monitors, the code argument will print out instrumentation information alongside bytecode. The -csv global argument outputs the monitor data in a CSV format to standard out, which is useful for processing data with external scripts. The available monitors and their options are as follows:

Monitor Options Description
branches {c|code} Tracks branch instructions to analyze control flow, depicting inward or outward control flow edges.
calls {c|code[=<function pattern*>]} Captures function call information and call stack, optionally filtered by a function pattern.
control Counts branches and loops and displays an annotated control flow graph.
coverage {c|code[=i|instr]} Tracks code coverage, optionally at block or instruction level.
debug Provides ability to step through bytecode and pause execution using breakpoints.
fprofile {<function pattern*>} Function profiler that reports time spent in individual functions
globals Provides information on the usage of global variables.
hotness {c|code} Identifies hot code regions with high execution frequency.
icount Reports instruction count within functions.
loops {c|code} Analyzes loop blocks and their execution behaviour.
memory Monitors memory operations, such as reads and writes.
memstats Monitors memory accesses and reports statistics per page of memory.
opcodes Reports the static and dynamic count of instructions, broken down by opcode.
profile {depth=<num>|calls=<function pattern*>} Collects performance profiling data, with options for depth or function pattern.
timeout {<num>} Terminates program execution after a given number of instructions.
tracepoints {<func-filter>:min_pc..max_pc} Traces a function's value stack at given locations.

Debugger

The debugger can be enabled using the debug monitor. Here's a description of the supported commands:

Command Description
run / r Begins execution of the program.
continue / c Resumes execution from the current point.
step / s Executes a single instruction and pauses.
next / n Advances to the next instruction, skipping function calls.
breakpoint / b {} Sets a new breakpoint at the specified location.
info Provides information, such as locals or breakpoints.
enable {} Enables a specific breakpoint identified by index.
disable {} Disables a specific breakpoint identified by index.
backtrace / bt Prints a backtrace of function calls.
set {} {} {} Modifies the value of a local index with a different value.