template <class Elf = elfldltl::Elf<>, elfldltl::ElfMachine Machine = elfldltl::ElfMachine::kNative>

class RemoteAbiStub

Defined at line 57 of file ../../sdk/lib/ld/include/lib/ld/remote-abi-stub.h

In the remote dynamic linking case, the passive ABI is anchored by the "stub

dynamic linker" (ld-stub.so in the build). This shared library gets loaded

as an implicit dependency to stand in for the in-process startup dynamic

linker that's usually there at runtime. Aside from the normal metadata and

a tiny code segment containing TLSDESC runtime hook code, it consists of a

final ZeroFillSegment or DataWithZeroFillSegment that holds space for the

passive ABI symbols.

The RemoteAbiStub object collects data about the layout and symbols in the

stub dynamic linker as decoded into a RemoteDecodedModule. The Init()

method examines the module and records its layout, and stores the module

RefPtr for later use. The RemoteAbiStub object can be reused or copied as

long as the same stub dynamic linker ELF file (or verbatim copy) is being

used.

This object is used by the RemoteAbiHeap to modify a RemoteLoadModule for

the specific instantiation of the stub dynamic linker for a particular

remote dynamic linking domain (or zygote thereof). The decoded_module()

pointer can be used to create that RemoteLoadModule.

RemoteAbiStub also collects a set of TLSDESC runtime entry point addresses.

These are not encoded as symbols, but obscured inside the .eh_frame table.

They are self-identifying to this code by a private protocol with the

assembly code that defines them (see

<lib

/ld/tlsdesc.h>), but in a way that

will be harmlessly ignored by other consumers of the stub dynamic linker's

.eh_frame CFI encoding such as runtime unwinders or debuggers. Users of the

RemoteAbiStub::tlsdesc_runtime methods should stay tightly coupled to the

TLSDESC runtime assembly code that's described in

<lib

/ld/tlsdesc.h> so that

the stub dynamic linker used at runtime came from the same ld library source

tree as this class.

Public Members

static auto & kFilename

Public Methods

void RemoteAbiStub<Elf, Machine> ()

Defined at line 72 of file ../../sdk/lib/ld/include/lib/ld/remote-abi-stub.h

void RemoteAbiStub<Elf, Machine> (const RemoteAbiStub<Elf, Machine> & )

Defined at line 73 of file ../../sdk/lib/ld/include/lib/ld/remote-abi-stub.h

void RemoteAbiStub<Elf, Machine> (RemoteAbiStub<Elf, Machine> && )

Defined at line 74 of file ../../sdk/lib/ld/include/lib/ld/remote-abi-stub.h

const RemoteModulePtr & decoded_module ()

This is the ld::RemoteDecodedModule for the stub dynamic

linker, the same pointer that was given to Create().

Defined at line 84 of file ../../sdk/lib/ld/include/lib/ld/remote-abi-stub.h

size_type data_vaddr ()

Return the module-relative vaddr of the data segment.

Defined at line 87 of file ../../sdk/lib/ld/include/lib/ld/remote-abi-stub.h

size_type data_size ()

Exact size of the data segment. This includes whatever file data gives it

a page-aligned starting vaddr, but the total size is not page-aligned.

Space directly after this can be used to lengthen the segment.

Defined at line 102 of file ../../sdk/lib/ld/include/lib/ld/remote-abi-stub.h

size_type abi_offset ()

Offset into the segment where _ld_abi sits.

Defined at line 105 of file ../../sdk/lib/ld/include/lib/ld/remote-abi-stub.h

size_type rdebug_offset ()

Offset into the segment where _r_debug sits.

Defined at line 108 of file ../../sdk/lib/ld/include/lib/ld/remote-abi-stub.h

size_type abi_vaddr ()

Return the module-relative vaddr of _ld_abi.

Defined at line 111 of file ../../sdk/lib/ld/include/lib/ld/remote-abi-stub.h

size_type rdebug_vaddr ()

Return the module-relative vaddr of _r_debug.

Defined at line 114 of file ../../sdk/lib/ld/include/lib/ld/remote-abi-stub.h

const TlsdescRuntimeHooks & tlsdesc_runtime ()

Module-relative addresses of the TLSDESC runtime entry points.

Defined at line 117 of file ../../sdk/lib/ld/include/lib/ld/remote-abi-stub.h

Addr tlsdesc_runtime (TlsdescRuntime hook)

Fetch a particular TLSDESC runtime entry point.

Defined at line 120 of file ../../sdk/lib/ld/include/lib/ld/remote-abi-stub.h

TlsDescResolver tls_desc_resolver (size_type stub_load_bias)

Return a TLSDESC resolver callable object that can be passed to

elfldltl::MakeSymbolResolver for static TLS layouts. It will use entry

points in the stub dynamic linker acquired by Init, applying the given

load bias for where the stub dynamic linker is to be loaded.

Defined at line 128 of file ../../sdk/lib/ld/include/lib/ld/remote-abi-stub.h

template <class Diagnostics>

Ptr Create (Diagnostics & diag, RemoteModulePtr ld_stub)

Create() calculates and records all those values by examining the stub

dynamic linker previously decoded. The module pointer is saved for later

use via decoded_module(), below. Note that if the Diagnostics object says

to keep going, this may return with partial information both in the

RemoteAbiStub and in the decoded_module().

Defined at line 138 of file ../../sdk/lib/ld/include/lib/ld/remote-abi-stub.h

template <class Diagnostics>

Ptr Create (Diagnostics & diag, zx::vmo ld_stub_vmo, size_type page_size)

This just rolls in RemoteModule::Create with the Create above.

Defined at line 149 of file ../../sdk/lib/ld/include/lib/ld/remote-abi-stub.h