whamm-dsl

whamm-dsl — The .mm Monitor Language

A .mm script is the instrumentation program whamm! injects into a WebAssembly binary (or compiles for engine-support). Each script contains global declarations followed by one or more probes. whamm! statically analyses match rules to decide which probes apply at each site, folding away constant guards before injection.

For installing whamm! and running instrumented modules, load the companion whamm skill in this plugin.

Script structure

A .mm file contains, in order:

1. use declarations — use lib; imports a named library.
2. Global variable declarations — report var, var, etc. declared at file scope.
3. Function definitions — name(args) -> ret { .. } (NOT YET IMPLEMENTED).
4. Probes — one or more match-rule blocks, each optionally gated by a predicate.

Match rules

provider:package:event:mode / predicate / { actions }

The predicate is optional. Without it: provider:package:event:mode { actions }.

Hierarchy: wasm (provider) → package → event → mode.

Package	Events	Modes
opcode	any opcode name or glob	before, after, alt
func	(any function)	entry, exit (unwind planned)
block	end	(none)
(none)	begin, end, report	(none — top-level probes)

Globbing examples:

wasm:opcode:*:before              # all opcodes, before
wasm::*if:before                  # if + br_if (empty package = wildcard)
wasm:opcode:*load*|*store*:before # all memory loads and stores
wasm:opcode:call|return_call:before

Type bounds narrow polymorphic args: wasm:opcode:call(arg0: i32):before matches only call sites where arg0 is i32.

Full event and bound-variable tables: see references/events.md.

Predicated probes & modes

wasm:opcode:call:before / pc == 25 && arg0 == 1 / {
    count++;
}

whamm! performs constant folding on static vars (pc, fid, imm0, …). At a site where pc != 25, the probe is not injected at all. At pc == 25 the dynamic guard arg0 == 1 is emitted inline.