class RemoteDecodedModule

ld::RemoteDecodedModule represents an ELF file and all the metadata

extracted from it. It's specifically meant only to hold a cache of

information distilled purely from the file's contents. So it doesn't

include a name, runtime load address, symbolizer module ID, or TLS module

ID. The tls_module_id() method returns 1 if the module has a PT_TLS at all.

The RemoteDecodedModule object owns a read-and-execute-only VMO handle for

the file's immutable contents and a mapping covering all its segments

(perhaps the whole file). The VMO is supplied at construction and is owned

for the lifetime of the RemoteDecodedModule. The Init method decodes the

ELF file's metadata and prepares the RemoteDecodedModule for use. All other

methods are const.

If Init encountered errors then the object may be in a partially-initialized

state where HasModule() returns false, or where it returns true but the

mapped_vmo() and/or module() and/or load_info() data is incomplete. How

much partial work might be done (and the return value of Init) depends on

when the Diagnostics object says to keep going. An incomplete object that

won't be used should be destroyed because it may use substantial resources

(like mapping the whole file VMO into the local address space).

It's a movable object, but moving it does not invalidate all the metadata

pointers. For the lifetime of the RemoteDecodedModule, other objects can

point into the mapped file's metadata such as by doing shallow copies of

`.module()`. The `.load_info()` object may own move-only zx::vmo handles to

VMOs in `.segments()` via elfldltl::SegmentWithVmo::Copy. (The distinction

between NoCopy and Copy doesn't really matter here, since the segments in

RemoteDecodedModule should never be passed to a VmarLoader. Using Copy just

expresses the abstract intent that RemoteDecodedModule be used in a const

fashion, including never modifying contents of VMOs it owns after Init.) As

no relocations are performed on these segments, such a VMO will only exist

when a DataWithZeroFillSegment with a partial page of bss is adjusted by

elfldltl::SegmentWithVmo::AlignSegments with a separate VMO. Any new VMO

becomes immutable (with no ZX_RIGHT_WRITE on the only handle) once its final

partial page has been zeroed.