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Merge pull request #48 from ProjectSynchro/elf-dynamic-support
Add ELF dynamic linking table (SHT_DYNAMIC) support
2 parents 4a7830b + fa50da0 commit 0b89af9

13 files changed

Lines changed: 1245 additions & 14 deletions

‎readme.md‎

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@@ -49,6 +49,7 @@ elf.Write(outStream);
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- Symbol Table
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- Relocation Table: supported I386, X86_64, ARM and AARCH64 relocations (others can be exposed by adding some mappings)
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- Note Table
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- Dynamic Linking Table (`SHT_DYNAMIC`)
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- Other sections fallback to `ElfCustomSection`
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- Program headers with or without sections
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- Print with `readelf` similar output

‎src/LibObjectFile.Tests/Elf/ElfSimpleTests.cs‎

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@@ -438,6 +438,131 @@ public async Task SimpleProgramHeaderAndCodeSectionAndSymbolSectionAndRelocation
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}
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[TestMethod]
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public async Task SimpleDynamicSection()
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{
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var elf = new ElfFile(ElfArch.X86_64);
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var dynstr = new ElfStringTable() { Name = ".dynstr" };
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elf.Add(dynstr);
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var dynamic = new ElfDynamicLinkingTable() { Link = dynstr };
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dynamic.AddNeededLibrary("libc.so.6");
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dynamic.AddNeededLibrary("libm.so.6");
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dynamic.Entries.Add(new ElfDynamic { Tag = (long)ElfDynamicTag.Flags1, Value = 0x08000001 });
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dynamic.Entries.Add(new ElfDynamic { Tag = (long)ElfDynamicTag.Null });
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elf.Add(dynamic);
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elf.Add(new ElfSectionHeaderStringTable());
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elf.Add(new ElfSectionHeaderTable());
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// The read helpers resolve DT_NEEDED offsets through the linked .dynstr.
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CollectionAssert.AreEqual(new[] { "libc.so.6", "libm.so.6" }, dynamic.GetNeededLibraries().ToList());
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await AssertReadElf(elf, "test_dynamic.elf");
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// Round-trip the entries and confirm the resolved library names survive write -> read.
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var memoryStream = new MemoryStream();
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elf.Write(memoryStream);
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memoryStream.Position = 0;
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var roundTrip = ElfFile.Read(memoryStream);
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var roundTripDynamic = roundTrip.Sections.OfType<ElfDynamicLinkingTable>().Single();
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Assert.AreEqual(dynamic.Entries.Count, roundTripDynamic.Entries.Count);
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CollectionAssert.AreEqual(new[] { "libc.so.6", "libm.so.6" }, roundTripDynamic.GetNeededLibraries().ToList());
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}
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[TestMethod]
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public void DynamicSectionStreamRoundTrip()
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{
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var elf = new ElfFile(ElfArch.X86_64);
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var dynstr = new ElfStringTable() { Name = ".dynstr" };
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elf.Add(dynstr);
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var dynamic = new ElfDynamicLinkingTable() { Link = dynstr };
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dynamic.AddNeededLibrary("libc.so.6");
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dynamic.Entries.Add(new ElfDynamic { Tag = (long)ElfDynamicTag.Flags1, Value = 0x08000001 });
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dynamic.Entries.Add(new ElfDynamic { Tag = (long)ElfDynamicTag.Null });
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elf.Add(dynamic);
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// Serialize just the .dynamic entries to a standalone stream (64-bit -> 16 bytes each).
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var stream = new MemoryStream();
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dynamic.Write(stream);
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Assert.AreEqual(dynamic.Entries.Count * 16, stream.Length);
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// Read them back into a fresh table attached to another file and confirm value equality.
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var elf2 = new ElfFile(ElfArch.X86_64);
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var dynamic2 = new ElfDynamicLinkingTable();
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elf2.Add(dynamic2);
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stream.Position = 0;
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dynamic2.Read(stream);
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CollectionAssert.AreEqual(dynamic.Entries, dynamic2.Entries);
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}
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[TestMethod]
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public void DynamicSection32Bit()
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{
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var elf = new ElfFile(ElfArch.I386);
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var dynstr = new ElfStringTable() { Name = ".dynstr" };
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elf.Add(dynstr);
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var dynamic = new ElfDynamicLinkingTable() { Link = dynstr };
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dynamic.AddNeededLibrary("libc.so.6");
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dynamic.Entries.Add(new ElfDynamic { Tag = (long)ElfDynamicTag.Flags, Value = 0x8 }); // DF_BIND_NOW
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dynamic.Entries.Add(new ElfDynamic { Tag = (long)ElfDynamicTag.Null });
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elf.Add(dynamic);
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// The printer uses 8-digit tag hex for 32-bit files.
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var writer = new StringWriter();
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ElfPrinter.PrintDynamicSections(elf, writer);
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var text = writer.ToString();
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StringAssert.Contains(text, " 0x00000001 (NEEDED)");
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StringAssert.Contains(text, "Shared library: [libc.so.6]");
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StringAssert.Contains(text, " 0x0000001e (FLAGS)");
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StringAssert.Contains(text, "BIND_NOW");
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// The Read32/Write32 path uses 8-byte Elf32_Dyn records.
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var stream = new MemoryStream();
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dynamic.Write(stream);
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Assert.AreEqual(dynamic.Entries.Count * 8, stream.Length);
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var elf2 = new ElfFile(ElfArch.I386);
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var dynamic2 = new ElfDynamicLinkingTable();
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elf2.Add(dynamic2);
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stream.Position = 0;
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dynamic2.Read(stream);
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CollectionAssert.AreEqual(dynamic.Entries, dynamic2.Entries);
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}
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[TestMethod]
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public void SectionHeader64BitFieldsNotTruncated()
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{
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// Regression: the 64-bit section header writer cast sh_addr/sh_offset/sh_size/etc. to uint,
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// truncating any value >= 4 GiB. A NOBITS section declares a huge address/size with no file bytes.
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var elf = new ElfFile(ElfArch.X86_64);
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var bss = new ElfNoBitsSection
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{
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Name = ".hugebss",
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VirtualAddress = 0x1_0000_2000UL, // > 4 GiB
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Size = 0x2_0000_1000UL, // > 4 GiB
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VirtualAddressAlignment = 0x1000,
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};
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elf.Add(bss);
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elf.Add(new ElfSectionHeaderStringTable());
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elf.Add(new ElfSectionHeaderTable());
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var stream = new MemoryStream();
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elf.Write(stream);
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stream.Position = 0;
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var roundTrip = ElfFile.Read(stream);
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var bss2 = roundTrip.Sections.OfType<ElfNoBitsSection>().Single();
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Assert.AreEqual(0x1_0000_2000UL, bss2.VirtualAddress);
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Assert.AreEqual(0x2_0000_1000UL, bss2.Size);
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}
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[TestMethod]
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public async Task TestAlignedSection()
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{

‎src/LibObjectFile.Tests/Verified/ElfSimpleTests.SimpleDynamicSection.verified.txt‎

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ELF Header:
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Magic: 7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00
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Class: ELF64
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Data: 2's complement, little endian
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Version: 1 (current)
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OS/ABI: UNIX - System V
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ABI Version: 0
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Type: REL (Relocatable file)
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Machine: Advanced Micro Devices X86-64
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Version: 0x1
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Entry point address: 0x0
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Start of program headers: 0 (bytes into file)
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Start of section headers: 0 (bytes into file)
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Flags: 0x0
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Size of this header: 0 (bytes)
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Size of program headers: 0 (bytes)
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Number of program headers: 0
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Size of section headers: 0 (bytes)
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Number of section headers: 4
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Section header string table index: 3
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Section Headers:
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[Nr] Name Type Address Off Size ES Flg Lk Inf Al
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[ 0] NULL 0000000000000000 000000 000000 00 0 0 0
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[ 1] .dynstr STRTAB 0000000000000000 000000 000000 00 0 0 0
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[ 2] .dynamic DYNAMIC 0000000000000000 000000 000000 10 A 1 0 0
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[ 3] .shstrtab STRTAB 0000000000000000 000000 000000 00 0 0 0
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Key to Flags:
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W (write), A (alloc), X (execute), M (merge), S (strings), I (info),
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L (link order), O (extra OS processing required), G (group), T (TLS),
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C (compressed), x (unknown), o (OS specific), E (exclude),
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D (mbind), l (large), p (processor specific)
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There are no section groups in this file.
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There are no program headers in this file.
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Dynamic section at offset 0x0 contains 4 entries:
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Tag Type Name/Value
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0x0000000000000001 (NEEDED) Shared library: [libc.so.6]
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0x0000000000000001 (NEEDED) Shared library: [libm.so.6]
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0x000000006ffffffb (FLAGS_1) Flags: NOW PIE
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0x0000000000000000 (NULL) 0x0
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There are no relocations in this file.
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No processor specific unwind information to decode
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No version information found in this file.

‎src/LibObjectFile.Tests/Verified/ElfSimpleTests.TestElf_name=helloworld.verified.txt‎

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11
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12 .init_array .fini_array .dynamic .got
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There is no dynamic section in this file.
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Dynamic section at offset 0x2dc8 contains 27 entries:
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Tag Type Name/Value
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0x0000000000000001 (NEEDED) Shared library: [libc.so.6]
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0x000000000000000c (INIT) 0x1000
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0x000000000000000d (FINI) 0x1174
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0x0000000000000019 (INIT_ARRAY) 0x3db8
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0x000000000000001b (INIT_ARRAYSZ) 8 (bytes)
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0x000000000000001a (FINI_ARRAY) 0x3dc0
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0x000000000000001c (FINI_ARRAYSZ) 8 (bytes)
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0x000000006ffffef5 (GNU_HASH) 0x3b0
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0x0000000000000005 (STRTAB) 0x480
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0x0000000000000006 (SYMTAB) 0x3d8
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0x000000000000000a (STRSZ) 141 (bytes)
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0x000000000000000b (SYMENT) 24 (bytes)
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0x0000000000000015 (DEBUG) 0x0
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0x0000000000000003 (PLTGOT) 0x3fb8
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0x0000000000000002 (PLTRELSZ) 24 (bytes)
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0x0000000000000014 (PLTREL) RELA
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0x0000000000000017 (JMPREL) 0x610
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0x0000000000000007 (RELA) 0x550
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0x0000000000000008 (RELASZ) 192 (bytes)
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0x0000000000000009 (RELAENT) 24 (bytes)
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0x000000000000001e (FLAGS) BIND_NOW
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0x000000006ffffffb (FLAGS_1) Flags: NOW PIE
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0x000000006ffffffe (VERNEED) 0x520
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0x000000006fffffff (VERNEEDNUM) 1
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0x000000006ffffff0 (VERSYM) 0x50e
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0x000000006ffffff9 (RELACOUNT) 3
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0x0000000000000000 (NULL) 0x0
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Relocation section '.rela.dyn' at offset 0x550 contains 8 entries:
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Offset Info Type Symbol's Value Symbol's Name + Addend

‎src/LibObjectFile.Tests/Verified/ElfSimpleTests.TestElf_name=helloworld_debug.verified.txt‎

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11
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12 .init_array .fini_array .dynamic .got
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There is no dynamic section in this file.
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Dynamic section at offset 0x2dc8 contains 27 entries:
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Tag Type Name/Value
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0x0000000000000001 (NEEDED) Shared library: [libc.so.6]
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0x000000000000000c (INIT) 0x1000
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0x000000000000000d (FINI) 0x1174
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0x0000000000000019 (INIT_ARRAY) 0x3db8
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0x000000000000001b (INIT_ARRAYSZ) 8 (bytes)
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0x000000000000001a (FINI_ARRAY) 0x3dc0
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0x000000000000001c (FINI_ARRAYSZ) 8 (bytes)
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0x000000006ffffef5 (GNU_HASH) 0x3b0
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0x0000000000000005 (STRTAB) 0x480
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0x0000000000000006 (SYMTAB) 0x3d8
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0x000000000000000a (STRSZ) 141 (bytes)
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0x000000000000000b (SYMENT) 24 (bytes)
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0x0000000000000015 (DEBUG) 0x0
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0x0000000000000003 (PLTGOT) 0x3fb8
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0x0000000000000002 (PLTRELSZ) 24 (bytes)
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0x0000000000000014 (PLTREL) RELA
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0x0000000000000017 (JMPREL) 0x610
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0x0000000000000007 (RELA) 0x550
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0x0000000000000008 (RELASZ) 192 (bytes)
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0x0000000000000009 (RELAENT) 24 (bytes)
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0x000000000000001e (FLAGS) BIND_NOW
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0x000000006ffffffb (FLAGS_1) Flags: NOW PIE
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0x000000006ffffffe (VERNEED) 0x520
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0x000000006fffffff (VERNEEDNUM) 1
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0x000000006ffffff0 (VERSYM) 0x50e
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0x000000006ffffff9 (RELACOUNT) 3
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0x0000000000000000 (NULL) 0x0
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Relocation section '.rela.dyn' at offset 0x550 contains 8 entries:
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Offset Info Type Symbol's Value Symbol's Name + Addend

‎src/LibObjectFile.Tests/Verified/ElfSimpleTests.TestElf_name=lib_debug.so.verified.txt‎

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09
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10 .init_array .fini_array .dynamic .got
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90-
There is no dynamic section in this file.
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Dynamic section at offset 0x2e90 contains 17 entries:
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Tag Type Name/Value
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0x000000000000000c (INIT) 0x1000
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0x000000000000000d (FINI) 0x1130
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0x0000000000000019 (INIT_ARRAY) 0x3e80
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0x000000000000001b (INIT_ARRAYSZ) 8 (bytes)
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0x000000000000001a (FINI_ARRAY) 0x3e88
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0x000000000000001c (FINI_ARRAYSZ) 8 (bytes)
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0x000000006ffffef5 (GNU_HASH) 0x2f0
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0x0000000000000005 (STRTAB) 0x3c0
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0x0000000000000006 (SYMTAB) 0x318
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0x000000000000000a (STRSZ) 122 (bytes)
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0x000000000000000b (SYMENT) 24 (bytes)
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0x0000000000000003 (PLTGOT) 0x4000
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0x0000000000000007 (RELA) 0x440
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0x0000000000000008 (RELASZ) 168 (bytes)
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0x0000000000000009 (RELAENT) 24 (bytes)
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0x000000006ffffff9 (RELACOUNT) 3
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0x0000000000000000 (NULL) 0x0
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Relocation section '.rela.dyn' at offset 0x440 contains 7 entries:
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Offset Info Type Symbol's Value Symbol's Name + Addend

‎src/LibObjectFile.Tests/Verified/ElfSimpleTests.TestElf_name=libstdc++.so.verified.txt‎

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11 .init_array .fini_array .data.rel.ro .dynamic .got
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96-
There is no dynamic section in this file.
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Dynamic section at offset 0x223c90 contains 30 entries:
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Tag Type Name/Value
98+
0x0000000000000001 (NEEDED) Shared library: [libm.so.6]
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0x0000000000000001 (NEEDED) Shared library: [libc.so.6]
100+
0x0000000000000001 (NEEDED) Shared library: [ld-linux-x86-64.so.2]
101+
0x0000000000000001 (NEEDED) Shared library: [libgcc_s.so.1]
102+
0x000000000000000e (SONAME) Library soname: [libstdc++.so.6]
103+
0x000000000000000c (INIT) 0x9a000
104+
0x000000000000000d (FINI) 0x1aafc4
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0x0000000000000019 (INIT_ARRAY) 0x21b880
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0x000000000000001b (INIT_ARRAYSZ) 120 (bytes)
107+
0x000000000000001a (FINI_ARRAY) 0x21b8f8
108+
0x000000000000001c (FINI_ARRAYSZ) 8 (bytes)
109+
0x000000006ffffef5 (GNU_HASH) 0x328
110+
0x0000000000000005 (STRTAB) 0x2d310
111+
0x0000000000000006 (SYMTAB) 0x90a0
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0x000000000000000a (STRSZ) 302456 (bytes)
113+
0x000000000000000b (SYMENT) 24 (bytes)
114+
0x0000000000000003 (PLTGOT) 0x226000
115+
0x0000000000000002 (PLTRELSZ) 25032 (bytes)
116+
0x0000000000000014 (PLTREL) RELA
117+
0x0000000000000017 (JMPREL) 0x92f78
118+
0x0000000000000007 (RELA) 0x7a8e8
119+
0x0000000000000008 (RELASZ) 99984 (bytes)
120+
0x0000000000000009 (RELAENT) 24 (bytes)
121+
0x000000006ffffffc (VERDEF) 0x7a0c0
122+
0x000000006ffffffd (VERDEFNUM) 48
123+
0x000000006ffffffe (VERNEED) 0x7a758
124+
0x000000006fffffff (VERNEEDNUM) 4
125+
0x000000006ffffff0 (VERSYM) 0x77088
126+
0x000000006ffffff9 (RELACOUNT) 899
127+
0x0000000000000000 (NULL) 0x0
97128

98129
Relocation section '.rela.dyn' at offset 0x7a8e8 contains 4166 entries:
99130
Offset Info Type Symbol's Value Symbol's Name + Addend

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