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Automerge: [lld][macho] Fix segfault while processing malformed object file. (#167025)
Ran into a use case where we had a MachO object file with a section symbol which did not have a section associated with it segfaults during linking. This patch aims to handle such cases gracefully and avoid the linker from crashing. --------- Co-authored-by: Ellis Hoag <[email protected]>
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‎lld/MachO/InputFiles.cpp‎

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@@ -808,6 +808,17 @@ void ObjFile::parseSymbols(ArrayRef<typename LP::section> sectionHeaders,
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continue;
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if ((sym.n_type & N_TYPE) == N_SECT) {
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if (sym.n_sect == 0) {
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fatal("section symbol " + StringRef(strtab + sym.n_strx) + " in " +
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toString(this) + " has an invalid section index [0]");
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}
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if (sym.n_sect > sections.size()) {
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fatal("section symbol " + StringRef(strtab + sym.n_strx) + " in " +
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toString(this) + " has an invalid section index [" +
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Twine(static_cast<unsigned>(sym.n_sect)) +
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"] greater than the total number of sections [" +
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Twine(sections.size()) + "]");
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}
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Subsections &subsections = sections[sym.n_sect - 1]->subsections;
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// parseSections() may have chosen not to parse this section.
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if (subsections.empty())

‎lld/test/MachO/handle-invalid-section-reference-too-big.test‎

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# REQUIRES: aarch64
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## This is a regression test which makes sure that when there is an invalid section index
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## associated with a section symbol, the linker does not segfault.
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## Test YAML content was created using the following steps
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## 1. Create an object file from the following assembly
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## `llvm-mc -filetype=obj -triple=arm64-apple-darwin symbol.s -o symbol.o`
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##
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## .text
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## .section __TEST,__mystuff
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## .globl _mysec
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## _mysec:
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## .byte 0xC3
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##
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## 2. Use obj2yaml to convert object file to yaml
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## `obj2yaml symbol.o -o symbol.yaml`
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##
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## 3. Manually set n_sect value of ltmp1 symbol to 10 which is greater than the number of sections 2.
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##
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# RUN: yaml2obj %s -o %t
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# RUN: not %lld -platform_version macos 10.14 11.0 -arch arm64 %t 2>&1 | FileCheck %s --check-prefix=FATAL
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# FATAL: error: section symbol ltmp0 in {{.*}} has an invalid section index [10] greater than the total number of sections [2]
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--- !mach-o
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FileHeader:
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magic: 0xFEEDFACF
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cputype: 0x100000C
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cpusubtype: 0x0
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filetype: 0x1
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ncmds: 3
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sizeofcmds: 336
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flags: 0x0
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reserved: 0x0
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LoadCommands:
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- cmd: LC_SEGMENT_64
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cmdsize: 232
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segname: ''
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vmaddr: 0
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vmsize: 1
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fileoff: 368
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filesize: 1
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maxprot: 7
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initprot: 7
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nsects: 2
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flags: 0
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Sections:
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- sectname: __text
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segname: __TEXT
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addr: 0x0
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size: 0
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offset: 0x170
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align: 0
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reloff: 0x0
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nreloc: 0
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flags: 0x80000000
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reserved1: 0x0
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reserved2: 0x0
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reserved3: 0x0
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content: ''
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- sectname: __mystuff
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segname: __TEST
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addr: 0x0
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size: 1
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offset: 0x170
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align: 0
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reloff: 0x0
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nreloc: 0
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flags: 0x0
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reserved1: 0x0
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reserved2: 0x0
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reserved3: 0x0
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content: C3
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- cmd: LC_SYMTAB
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cmdsize: 24
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symoff: 376
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nsyms: 3
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stroff: 424
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strsize: 24
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- cmd: LC_DYSYMTAB
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cmdsize: 80
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ilocalsym: 0
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nlocalsym: 2
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iextdefsym: 2
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nextdefsym: 1
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iundefsym: 3
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nundefsym: 0
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tocoff: 0
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ntoc: 0
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modtaboff: 0
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nmodtab: 0
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extrefsymoff: 0
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nextrefsyms: 0
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indirectsymoff: 0
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nindirectsyms: 0
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extreloff: 0
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nextrel: 0
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locreloff: 0
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nlocrel: 0
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LinkEditData:
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NameList:
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- n_strx: 14
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n_type: 0xE
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n_sect: 10
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n_desc: 0
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n_value: 0
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- n_strx: 8
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n_type: 0xE
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n_sect: 2
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n_desc: 0
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n_value: 0
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- n_strx: 1
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n_type: 0xF
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n_sect: 2
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n_desc: 0
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n_value: 0
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StringTable:
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- ''
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- _mysec
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- ltmp1
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- ltmp0
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- ''
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- ''
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- ''
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- ''
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...

‎lld/test/MachO/handle-invalid-section-reference-zero.test‎

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# REQUIRES: aarch64
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## This is a regression test which makes sure that when there is an invalid section index
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## associated with a section symbol, the linker does not segfault.
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## Test YAML content was created using the following steps
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## 1. Create an object file from the following assembly
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## `llvm-mc -filetype=obj -triple=arm64-apple-darwin symbol.s -o symbol.o`
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##
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## .text
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## .section __TEST,__mystuff
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## .globl _mysec
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## _mysec:
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## .byte 0xC3
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##
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## 2. Use obj2yaml to convert object file to yaml
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## `obj2yaml symbol.o -o symbol.yaml`
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##
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## 3. Manually set n_sect value of ltmp1 symbol to 0 instead of 1.
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##
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# RUN: yaml2obj %s -o %t
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# RUN: not %lld -platform_version macos 10.14 11.0 -arch arm64 %t 2>&1 | FileCheck %s --check-prefix=FATAL
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# FATAL: error: section symbol ltmp0 in {{.*}} has an invalid section index [0]
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--- !mach-o
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FileHeader:
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magic: 0xFEEDFACF
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cputype: 0x100000C
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cpusubtype: 0x0
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filetype: 0x1
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ncmds: 3
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sizeofcmds: 336
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flags: 0x0
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reserved: 0x0
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LoadCommands:
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- cmd: LC_SEGMENT_64
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cmdsize: 232
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segname: ''
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vmaddr: 0
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vmsize: 1
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fileoff: 368
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filesize: 1
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maxprot: 7
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initprot: 7
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nsects: 2
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flags: 0
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Sections:
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- sectname: __text
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segname: __TEXT
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addr: 0x0
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size: 0
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offset: 0x170
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align: 0
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reloff: 0x0
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nreloc: 0
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flags: 0x80000000
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reserved1: 0x0
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reserved2: 0x0
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reserved3: 0x0
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content: ''
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- sectname: __mystuff
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segname: __TEST
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addr: 0x0
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size: 1
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offset: 0x170
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align: 0
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reloff: 0x0
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nreloc: 0
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flags: 0x0
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reserved1: 0x0
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reserved2: 0x0
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reserved3: 0x0
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content: C3
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- cmd: LC_SYMTAB
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cmdsize: 24
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symoff: 376
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nsyms: 3
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stroff: 424
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strsize: 24
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- cmd: LC_DYSYMTAB
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cmdsize: 80
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ilocalsym: 0
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nlocalsym: 2
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iextdefsym: 2
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nextdefsym: 1
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iundefsym: 3
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nundefsym: 0
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tocoff: 0
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ntoc: 0
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modtaboff: 0
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nmodtab: 0
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extrefsymoff: 0
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nextrefsyms: 0
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indirectsymoff: 0
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nindirectsyms: 0
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extreloff: 0
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nextrel: 0
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locreloff: 0
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nlocrel: 0
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LinkEditData:
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NameList:
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- n_strx: 14
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n_type: 0xE
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n_sect: 0
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n_desc: 0
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n_value: 0
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- n_strx: 8
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n_type: 0xE
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n_sect: 2
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n_desc: 0
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n_value: 0
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- n_strx: 1
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n_type: 0xF
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n_sect: 2
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n_desc: 0
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n_value: 0
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StringTable:
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- ''
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- _mysec
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- ltmp1
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- ltmp0
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- ''
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- ''
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- ''
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- ''
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...

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