ELF: Overhaul metadata extraction #87285
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,34 @@ | ||
| //===--- MetadataSectionNames.def -----------------------------------------===// | ||
| // | ||
| // This source file is part of the Swift.org open source project | ||
| // | ||
| // Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors | ||
| // Licensed under Apache License v2.0 with Runtime Library Exception | ||
| // | ||
| // See https://swift.org/LICENSE.txt for license information | ||
| // See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors | ||
| // | ||
| //===----------------------------------------------------------------------===// | ||
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| #ifndef HANDLE_SWIFT_SECTION | ||
| #error "HANDLE_SWIFT_SECTION(elfname, coffname) not defined" | ||
| #endif | ||
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| // NOTE: This table is ABI. Don't rearrange it! | ||
| // NOTE: If adding fields, remember to add the field to ReflectionContext.h | ||
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| HANDLE_SWIFT_SECTION(swift5_protocols, sw5prt) | ||
| HANDLE_SWIFT_SECTION(swift5_protocol_conformances, sw5prtc) | ||
| HANDLE_SWIFT_SECTION(swift5_type_metadata, sw5tymd) | ||
| HANDLE_SWIFT_SECTION(swift5_typeref, sw5tyrf) | ||
| HANDLE_SWIFT_SECTION(swift5_reflstr, sw5rfst) | ||
| HANDLE_SWIFT_SECTION(swift5_fieldmd, sw5flmd) | ||
| HANDLE_SWIFT_SECTION(swift5_assocty, sw5asty) | ||
| HANDLE_SWIFT_SECTION(swift5_replace, sw5repl) | ||
| HANDLE_SWIFT_SECTION(swift5_replac2, sw5reps) | ||
| HANDLE_SWIFT_SECTION(swift5_builtin, sw5bltn) | ||
| HANDLE_SWIFT_SECTION(swift5_capture, sw5cptr) | ||
| HANDLE_SWIFT_SECTION(swift5_mpenum, sw5mpen) | ||
| HANDLE_SWIFT_SECTION(swift5_accessible_functions, sw5acfn) | ||
| HANDLE_SWIFT_SECTION(swift5_runtime_attributes, sw5ratt) | ||
| HANDLE_SWIFT_SECTION(swift5_tests, sw5test) |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,188 @@ | ||
| //===--- SwiftRT-ELF.cpp --------------------------------------------------===// | ||
| // | ||
| // This source file is part of the Swift.org open source project | ||
| // | ||
| // Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors | ||
| // Licensed under Apache License v2.0 with Runtime Library Exception | ||
| // | ||
| // See https://swift.org/LICENSE.txt for license information | ||
| // See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors | ||
| // | ||
| //===----------------------------------------------------------------------===// | ||
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| #include "ImageInspectionCommon.h" | ||
| #include "swift/Runtime/Backtrace.h" | ||
| #include "swift/Runtime/Config.h" | ||
| #include "swift/shims/MetadataSections.h" | ||
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| #include <cstddef> | ||
| #include <new> | ||
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| #define SWIFT_METADATA_SEGMENT_TYPE 0x73356d64 // s5md or dms5 on little-endian | ||
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| extern "C" const char __ehdr_start[] __attribute__((__weak__)); | ||
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| #if SWIFT_ENABLE_BACKTRACING | ||
| // Drag in a symbol from the backtracer, to force the static linker to include | ||
| // the code. | ||
| static const void *__backtraceRef __attribute__((used, retain)) = | ||
| (const void *)swift::runtime::backtrace::_swift_backtrace_isThunkFunction; | ||
| #endif | ||
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| // Create empty sections to ensure that the start/stop symbols are synthesized | ||
|
Contributor
There was a problem hiding this comment. I haven't tried, but if we declare the symbols we add as |
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| // by the linker. Otherwise, we may end up with undefined symbol references as | ||
| // the linker table section was never constructed. | ||
| #define DECLARE_EMPTY_METADATA_SECTION(name) \ | ||
| __asm__("\t.section " #name ",\"aR\"\n"); | ||
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| #define BOUNDS_VISIBILITY \ | ||
| __attribute__((__visibility__("hidden"), __aligned__(1))) | ||
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| #define DECLARE_BOUNDS(name) \ | ||
| BOUNDS_VISIBILITY extern const char __start_##name; \ | ||
| BOUNDS_VISIBILITY extern const char __stop_##name; | ||
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| #define DECLARE_SWIFT_SECTION(name) \ | ||
| DECLARE_EMPTY_METADATA_SECTION(name) \ | ||
| DECLARE_BOUNDS(name) | ||
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| // These may or may not be present, depending on compiler switches; it's | ||
| // worth calling them out as a result. | ||
| #define DECLARE_SWIFT_REFLECTION_SECTION(name) DECLARE_SWIFT_SECTION(name) | ||
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| extern "C" { | ||
| DECLARE_SWIFT_SECTION(swift5_protocols) | ||
| DECLARE_SWIFT_SECTION(swift5_protocol_conformances) | ||
| DECLARE_SWIFT_SECTION(swift5_type_metadata) | ||
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| DECLARE_SWIFT_REFLECTION_SECTION(swift5_fieldmd) | ||
| DECLARE_SWIFT_REFLECTION_SECTION(swift5_builtin) | ||
| DECLARE_SWIFT_REFLECTION_SECTION(swift5_assocty) | ||
| DECLARE_SWIFT_REFLECTION_SECTION(swift5_capture) | ||
| DECLARE_SWIFT_REFLECTION_SECTION(swift5_reflstr) | ||
| DECLARE_SWIFT_REFLECTION_SECTION(swift5_typeref) | ||
| DECLARE_SWIFT_REFLECTION_SECTION(swift5_mpenum) | ||
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| DECLARE_SWIFT_SECTION(swift5_replace) | ||
| DECLARE_SWIFT_SECTION(swift5_replac2) | ||
| DECLARE_SWIFT_SECTION(swift5_accessible_functions) | ||
| DECLARE_SWIFT_SECTION(swift5_runtime_attributes) | ||
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| DECLARE_SWIFT_SECTION(swift5_tests) | ||
|
Contributor
There was a problem hiding this comment. We can mark this section as "maybe not present" too. |
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| } | ||
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| #undef DECLARE_SWIFT_SECTION | ||
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| namespace { | ||
| struct ElfNoteHeader { | ||
| uint32_t namesz; | ||
| uint32_t descsz; | ||
| uint32_t type; | ||
| }; | ||
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| struct SectionRange { | ||
| uintptr_t start; | ||
| uintptr_t stop; | ||
| }; | ||
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| // If you update this table, remember to update the reader in | ||
| // ReflectionContext.h! | ||
| struct MetadataSections { | ||
|
Contributor
There was a problem hiding this comment. Moving this type out of SwiftShims will break Swift Testing.
Member
Author
There was a problem hiding this comment. Different metadata sections (open to a new name, did't like The
Contributor
There was a problem hiding this comment. Alrighty. We should synchronize our PRs so we can drop |
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| uintptr_t version; | ||
| uintptr_t base; | ||
| uintptr_t unused0; | ||
| uintptr_t unused1; | ||
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| #define HANDLE_SWIFT_SECTION(name, coff) SectionRange name; | ||
| #include "MetadataSectionNames.def" | ||
| #undef HANDLE_SWIFT_SECTION | ||
| }; | ||
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| struct __attribute__((__packed__)) SwiftMetadataNote { | ||
| ElfNoteHeader header; | ||
| char name[8]; // "swift6\0" + 1 byte(s) of padding | ||
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| MetadataSections sections; | ||
| }; | ||
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| /// .note.swift_metadata section stores the table of start/stop symbols for | ||
| /// ingestion into the runtime and for static tool access. | ||
| // TODO: We should replace addNewDSOImage with something that takes a pointer to | ||
| // the table directly, removing the need for the additional global constructor | ||
| // that converts the start/stop symbol pointer ranges to start/byte-count, | ||
| // before stabilizing any ELF platform ABIs. This will help reduce program | ||
| // launch times. | ||
| // This will require changes to Swift Testing and the runtime metadata | ||
| // registration. | ||
| __asm__(".section .note.swift_metadata, \"a\", @note"); | ||
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| SWIFT_ALLOWED_RUNTIME_GLOBAL_CTOR_BEGIN | ||
| __attribute__((section(".note.swift_metadata"), used, aligned(4))) | ||
| const static SwiftMetadataNote swiftMetadataNote = { | ||
| // header | ||
| .header = | ||
| { | ||
| .namesz = 7, // namesz: "swift6\0" | ||
|
Contributor
There was a problem hiding this comment. You might want to pick a slightly more specific name in case we decide we want to do more with notes in the future.
Member
Author
There was a problem hiding this comment. That is what the segment type is for. The type is namespaced to the name, so we can use any 4-byte number. I went with the bytes that spell out
Contributor
There was a problem hiding this comment. I'm suggesting we make the type |
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| .descsz = sizeof(MetadataSections), | ||
| .type = SWIFT_METADATA_SEGMENT_TYPE, | ||
| }, // 4 + 4 + 4 = 12, 0x0c | ||
| .name = | ||
| { | ||
| 's', 'w', 'i', 'f', 't', '6', '\0', | ||
| static_cast<char>(0xff), // padding | ||
| }, // 12 + 7 + 1 = 20, 0x14 | ||
| .sections = | ||
| { | ||
| .version = 5, | ||
| .base = reinterpret_cast<uintptr_t>(&__ehdr_start), | ||
| .unused0 = 0xa1a1a1a1, | ||
| .unused1 = 0xb2b2b2b2, | ||
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| #define HANDLE_SWIFT_SECTION(elfname, coffname) \ | ||
| .elfname = { \ | ||
| reinterpret_cast<uintptr_t>(&__start_##elfname), \ | ||
| reinterpret_cast<uintptr_t>(&__stop_##elfname), \ | ||
| }, | ||
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| #include "MetadataSectionNames.def" | ||
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| #undef HANDLE_SWIFT_SECTION | ||
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| }, | ||
| }; | ||
| SWIFT_ALLOWED_RUNTIME_GLOBAL_CTOR_END | ||
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| } // anonymous namespace | ||
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| namespace { | ||
| static swift::MetadataSections sections{}; | ||
| } | ||
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| SWIFT_ALLOWED_RUNTIME_GLOBAL_CTOR_BEGIN | ||
| __attribute__((__constructor__)) static void swift_image_constructor() { | ||
| #define SWIFT_SECTION_RANGE(name) \ | ||
| { \ | ||
| swiftMetadataNote.sections.name.start, \ | ||
| swiftMetadataNote.sections.name.stop - \ | ||
| swiftMetadataNote.sections.name.start, \ | ||
| } | ||
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| ::new (§ions) swift::MetadataSections{ | ||
| swiftMetadataNote.sections.version, | ||
| reinterpret_cast<const char *>(swiftMetadataNote.sections.base), | ||
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| reinterpret_cast<void *>(swiftMetadataNote.sections.unused0), | ||
| reinterpret_cast<void *>(swiftMetadataNote.sections.unused1), | ||
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| #define HANDLE_SWIFT_SECTION(elfname, coffname) SWIFT_SECTION_RANGE(elfname), | ||
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| #include "MetadataSectionNames.def" | ||
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| #undef HANDLE_SWIFT_SECTION | ||
| }; | ||
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| #undef SWIFT_SECTION_RANGE | ||
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| swift_addNewDSOImage(§ions); | ||
| } | ||
| SWIFT_ALLOWED_RUNTIME_GLOBAL_CTOR_END | ||
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Why not change the type of Segment's Contents from StringRef to
std::string? Doesn't look like you useRelocatedSegmentStorageoutside of this function. The StringRef to a reference to a mutable string makes me slightly worried that a code change in the future that mutates the string could cause a dangling pointer.