AddMeta is invoked during package "init" functions by the compiler when compiling for coverage instrumentation; here 'p' is a meta-data blob of length 'dlen' for the package in question, 'hash' is a compiler-computed md5.sum for the blob, 'pkpath' is the package path, 'pkid' is the hard-coded ID that the compiler is using for the package (or -1 if the compiler doesn't think a hard-coded ID is needed), and 'cmode'/'cgran' are the coverage counter mode and granularity requested by the user.

Meta is the top-level container for bits of state related to code coverage meta-data in the runtime.

CovCounterBlob is a container for encapsulating a counter section (BSS variable) for an instrumented Go module.

CovMetaBlob is a container for holding the meta-data symbol (an RODATA variable) for an instrumented Go package.