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8feba8d584
This PR replaces our use of `__dso_handle` and (indirectly) `dladdr()` when figuring out the base address of loaded Swift images on ELF-based platforms. Instead, we use `__ehdr_start` which refers to the start of the image's ELF header (i.e. the start of the file) and is provided by the compiler/linker for this purpose. This pointer is consumed by `swift_addNewDSOImage()` and, later, by Swift Testing when running tests, but is otherwise unused, so the less work we do on it at runtime, the better. A fallback path is present that, for images that do not contain `__ehdr_start`, derives the address by calling `dladdr()` on the section structure's address. Resolves #84997.
131 lines
4.4 KiB
C++
131 lines
4.4 KiB
C++
//===--- SwiftRT-ELF-WASM.cpp ---------------------------------------------===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See https://swift.org/LICENSE.txt for license information
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// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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#include "ImageInspectionCommon.h"
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#include "swift/shims/MetadataSections.h"
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#include "swift/Runtime/Backtrace.h"
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#include "swift/Runtime/Config.h"
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#include <cstddef>
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#include <new>
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#if defined(__ELF__)
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extern "C" const char __ehdr_start[] __attribute__((__weak__));
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#endif
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#if SWIFT_ENABLE_BACKTRACING
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// Drag in a symbol from the backtracer, to force the static linker to include
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// the code.
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static const void *__backtraceRef __attribute__((used, retain))
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= (const void *)swift::runtime::backtrace::_swift_backtrace_isThunkFunction;
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#endif
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// Create empty sections to ensure that the start/stop symbols are synthesized
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// by the linker. Otherwise, we may end up with undefined symbol references as
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// the linker table section was never constructed.
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#if defined(__ELF__)
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# define DECLARE_EMPTY_METADATA_SECTION(name, attrs) __asm__("\t.section " #name ",\"" attrs "\"\n");
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#elif defined(__wasm__)
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# define DECLARE_EMPTY_METADATA_SECTION(name, attrs) __asm__("\t.section " #name ",\"R\",@\n");
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#endif
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#define BOUNDS_VISIBILITY __attribute__((__visibility__("hidden"), \
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__aligned__(1)))
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#define DECLARE_BOUNDS(name) \
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BOUNDS_VISIBILITY extern const char __start_##name; \
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BOUNDS_VISIBILITY extern const char __stop_##name;
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#define DECLARE_SWIFT_SECTION(name) \
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DECLARE_EMPTY_METADATA_SECTION(name, "aR") \
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DECLARE_BOUNDS(name)
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// These may or may not be present, depending on compiler switches; it's
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// worth calling them out as a result.
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#define DECLARE_SWIFT_REFLECTION_SECTION(name) \
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DECLARE_SWIFT_SECTION(name)
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extern "C" {
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DECLARE_SWIFT_SECTION(swift5_protocols)
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DECLARE_SWIFT_SECTION(swift5_protocol_conformances)
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DECLARE_SWIFT_SECTION(swift5_type_metadata)
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DECLARE_SWIFT_REFLECTION_SECTION(swift5_fieldmd)
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DECLARE_SWIFT_REFLECTION_SECTION(swift5_builtin)
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DECLARE_SWIFT_REFLECTION_SECTION(swift5_assocty)
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DECLARE_SWIFT_REFLECTION_SECTION(swift5_capture)
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DECLARE_SWIFT_REFLECTION_SECTION(swift5_reflstr)
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DECLARE_SWIFT_REFLECTION_SECTION(swift5_typeref)
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DECLARE_SWIFT_REFLECTION_SECTION(swift5_mpenum)
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DECLARE_SWIFT_SECTION(swift5_replace)
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DECLARE_SWIFT_SECTION(swift5_replac2)
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DECLARE_SWIFT_SECTION(swift5_accessible_functions)
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DECLARE_SWIFT_SECTION(swift5_runtime_attributes)
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DECLARE_SWIFT_SECTION(swift5_tests)
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}
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#undef DECLARE_SWIFT_SECTION
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namespace {
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static swift::MetadataSections sections{};
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}
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SWIFT_ALLOWED_RUNTIME_GLOBAL_CTOR_BEGIN
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__attribute__((__constructor__))
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static void swift_image_constructor() {
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#define SWIFT_SECTION_RANGE(name) \
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{ reinterpret_cast<uintptr_t>(&__start_##name), \
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static_cast<uintptr_t>(&__stop_##name - &__start_##name) }
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const void *baseAddress = nullptr;
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#if defined(__ELF__)
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if (&__ehdr_start != nullptr) {
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baseAddress = __ehdr_start;
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}
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#elif defined(__wasm__)
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// NOTE: Multi images in a single process is not yet stabilized in WebAssembly
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// toolchain outside of Emscripten.
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#endif
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::new (§ions) swift::MetadataSections {
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swift::CurrentSectionMetadataVersion,
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baseAddress,
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nullptr,
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nullptr,
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SWIFT_SECTION_RANGE(swift5_protocols),
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SWIFT_SECTION_RANGE(swift5_protocol_conformances),
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SWIFT_SECTION_RANGE(swift5_type_metadata),
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SWIFT_SECTION_RANGE(swift5_typeref),
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SWIFT_SECTION_RANGE(swift5_reflstr),
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SWIFT_SECTION_RANGE(swift5_fieldmd),
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SWIFT_SECTION_RANGE(swift5_assocty),
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SWIFT_SECTION_RANGE(swift5_replace),
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SWIFT_SECTION_RANGE(swift5_replac2),
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SWIFT_SECTION_RANGE(swift5_builtin),
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SWIFT_SECTION_RANGE(swift5_capture),
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SWIFT_SECTION_RANGE(swift5_mpenum),
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SWIFT_SECTION_RANGE(swift5_accessible_functions),
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SWIFT_SECTION_RANGE(swift5_runtime_attributes),
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SWIFT_SECTION_RANGE(swift5_tests),
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};
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#undef SWIFT_SECTION_RANGE
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swift_addNewDSOImage(§ions);
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}
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SWIFT_ALLOWED_RUNTIME_GLOBAL_CTOR_END
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