nimbus-eth1/nimbus/transaction/evmc_dynamic_loader.nim

120 lines
4.3 KiB
Nim

# Nimbus - Dynamic loader for EVM modules as shared libraries / DLLs
#
# Copyright (c) 2019-2021 Status Research & Development GmbH
# Licensed under either of
# * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
# * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
# at your option. This file may not be copied, modified, or distributed except according to those terms.
#{.push raises: [Defect].}
import
std/[dynlib, strformat, strutils, os],
chronicles,
evmc/evmc, ../config
# The built-in Nimbus EVM, via imported C function.
proc evmc_create_nimbus_evm(): ptr evmc_vm {.cdecl, importc.}
# Import this module to link in the definition of `evmc_create_nimbus_evm`.
# Nim thinks the module is unused because the function is only called via
# `.exportc` -> `.importc`.
{.warning[UnusedImport]: off.}:
import ./evmc_vm_glue
var evmcLibraryPath {.threadvar.}: string
## Library path set by `--evm` command line option.
## Like the loaded EVMs themselves, this is thread-local for Nim simplicity.
proc evmcSetLibraryPath*(path: string) =
evmcLibraryPath = path
proc evmcLoadVMGetCreateFn(): (evmc_create_vm_name_fn, string) =
var path = evmcLibraryPath
if path.len == 0:
path = getEnv("NIMBUS_EVM")
# Use built-in EVM if no other is specified.
if path.len == 0:
return (evmc_create_nimbus_evm, "built-in")
# The steps below match the EVMC Loader documentation, copied here:
#
# - The filename is used to guess the EVM name and the name of the create
# function. The create function name is constructed by the following
# rules. Consider example path: "/ethereum/libexample-interpreter.so.1.0".
# - The filename is taken from the path: "libexample-interpreter.so.1.0".
# - The "lib" prefix and all file extensions are stripped from the name:
# "example-interpreter".
# - All "-" are replaced with "_" to construct base name:
# "example_interpreter"
# - The function name "evmc_create_" + base name is searched in the library:
# "evmc_create_example_interpreter",
# - If the function is not found, the function name "evmc_create" is searched
# in the library.
# Load the library.
let lib = loadLib(path, false)
if lib.isNil:
warn "Error loading EVM library", path
return (nil, "")
# Find filename in the path.
var symbolName = os.extractFilename(path)
# Skip "lib" prefix if present. Note, `removePrefix` only removes at the
# start despite its documentation.
symbolName.removePrefix("lib")
# Trim all file extesnsions. (`os.splitFile` only removes the last.)
symbolName = symbolName.split('.', 1)[0]
# Replace all "-" with "_".
symbolName = symbolName.replace('-', '_')
# Search for the built function name.
symbolName = "evmc_create_" & symbolName
var sym = symAddr(lib, symbolName)
if sym.isNil:
const fallback = "evmc_create"
sym = symAddr(lib, fallback)
if sym.isNil:
warn "EVMC create function not found in library", path
warn "Tried this library symbol", symbol=symbolName
warn "Tried this library symbol", symbol=fallback
return (nil, "")
return (cast[evmc_create_vm_name_fn](sym), path)
proc evmcLoadVMShowDetail(): ptr evmc_vm =
let (vmCreate, vmDescription) = evmcLoadVMGetCreateFn()
if vmCreate.isNil:
return nil
{.gcsafe.}:
let vm: ptr evmc_vm = vmCreate()
if vm.isNil:
warn "The loaded EVM did not create a VM when requested",
`from`=vmDescription
return nil
if vm.abi_version != EVMC_ABI_VERSION:
warn "The loaded EVM is for an incompatible EVMC ABI",
requireABI=EVMC_ABI_VERSION, loadedABI=vm.abi_version,
`from`=vmDescription
warn "The loaded EVM will not be used", `from`=vmDescription
return nil
let name = if vm.name.isNil: "<nil>" else: $vm.name
let version = if vm.version.isNil: "<nil>" else: $vm.version
info "Using EVM", name=name, version=version, `from`=vmDescription
return vm
proc evmcLoadVMCached*(): ptr evmc_vm =
# TODO: Make this open the VM library once per process. Currently it does
# so once per thread, but at least this is thread-safe.
var vm {.threadvar.}: ptr evmc_vm
var triedLoading {.threadvar.}: bool
if not triedLoading:
triedLoading = true
vm = evmcLoadVMShowDetail()
return vm