[llvm][yaml2obj] Modify section header overriding timing (#130942)
yaml2obj should determine the program header offset (and other properties) based on the intended values rather than the final `sh_offset` of the section header. `setProgramHeaderLayout` uses section offsets for determining `p_offset`. Move section header overriding after `setProgramHeaderLayout` to prevent `ShOffset` from affecting program header `p_offset`. This change adjusts the timing of when the section header is overridden to ensure that the program headers are set correctly. More details [here](https://github.com/llvm/llvm-project/pull/126537#issuecomment-2700421989). --------- Signed-off-by: Ruoyu Qiu <cabbaken@outlook.com> Signed-off-by: Ruoyu Qiu <qiuruoyu@xiaomi.com> Co-authored-by: Ruoyu Qiu <qiuruoyu@xiaomi.com>
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Ruoyu Qiu
GitHub
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commit
c1fca0fa14
@ -206,6 +206,9 @@ template <class ELFT> class ELFState {
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NameToIdxMap DynSymN2I;
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ELFYAML::Object &Doc;
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std::vector<std::pair<Elf_Shdr *, ELFYAML::Section>>
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SectionHeadersOverrideHelper;
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StringSet<> ExcludedSectionHeaders;
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uint64_t LocationCounter = 0;
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@ -226,6 +229,7 @@ template <class ELFT> class ELFState {
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StringRef SecName, ELFYAML::Section *YAMLSec);
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void initSectionHeaders(std::vector<Elf_Shdr> &SHeaders,
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ContiguousBlobAccumulator &CBA);
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void overrideSectionHeaders(std::vector<Elf_Shdr> &SHeaders);
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void initSymtabSectionHeader(Elf_Shdr &SHeader, SymtabType STType,
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ContiguousBlobAccumulator &CBA,
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ELFYAML::Section *YAMLSec);
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@ -849,7 +853,7 @@ void ELFState<ELFT>::initSectionHeaders(std::vector<Elf_Shdr> &SHeaders,
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}
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LocationCounter += SHeader.sh_size;
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overrideFields<ELFT>(Sec, SHeader);
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SectionHeadersOverrideHelper.push_back({&SHeader, *Sec});
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continue;
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}
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@ -903,12 +907,17 @@ void ELFState<ELFT>::initSectionHeaders(std::vector<Elf_Shdr> &SHeaders,
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}
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LocationCounter += SHeader.sh_size;
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// Override section fields if requested.
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overrideFields<ELFT>(Sec, SHeader);
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SectionHeadersOverrideHelper.push_back({&SHeader, *Sec});
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}
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}
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template <class ELFT>
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void ELFState<ELFT>::overrideSectionHeaders(std::vector<Elf_Shdr> &SHeaders) {
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for (std::pair<Elf_Shdr *, ELFYAML::Section> &HeaderAndSec :
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SectionHeadersOverrideHelper)
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overrideFields<ELFT>(&HeaderAndSec.second, *HeaderAndSec.first);
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}
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template <class ELFT>
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void ELFState<ELFT>::assignSectionAddress(Elf_Shdr &SHeader,
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ELFYAML::Section *YAMLSec) {
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@ -2105,6 +2114,11 @@ bool ELFState<ELFT>::writeELF(raw_ostream &OS, ELFYAML::Object &Doc,
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// Now we can decide segment offsets.
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State.setProgramHeaderLayout(PHeaders, SHeaders);
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// Override section fields, if requested. This needs to happen after program
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// header layout happens, because otherwise the layout will use the new
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// values.
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State.overrideSectionHeaders(SHeaders);
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bool ReachedLimit = CBA.getOffset() > MaxSize;
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if (Error E = CBA.takeLimitError()) {
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// We report a custom error message instead below.
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@ -91,7 +91,7 @@
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## Case D: the same as "Case C", but for a 32-bit object.
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# RUN: yaml2obj %s -DBITS=32 -DOFFSET=0xffffffff -o %t5
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# RUN: yaml2obj %s -DBITS=32 -DFILESIZE=8 -DOFFSET=0xffffffff -o %t5
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# RUN: llvm-readobj %t5 --dynamic-table 2>&1 | FileCheck -DFILE=%t5 %s \
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# RUN: --check-prefix=WARN5 --implicit-check-not=warning:
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# RUN: llvm-readelf %t5 --dynamic-table 2>&1 | FileCheck -DFILE=%t5 %s \
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@ -101,7 +101,7 @@
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# WARN5: warning: '[[FILE]]': unable to read the dynamic table from SHT_DYNAMIC section with index 1: offset (0xffffffff) + size (0x8) is greater than the file size (0x10c8)
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# WARN5: warning: '[[FILE]]': no valid dynamic table was found
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# RUN: yaml2obj %s -DNOHEADERS=true -DBITS=32 -DOFFSET=0xffffffff -o %t5.noheaders
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# RUN: yaml2obj %s -DNOHEADERS=true -DBITS=32 -DFILESIZE=8 -DOFFSET=0xffffffff -o %t5.noheaders
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# RUN: llvm-readobj %t5.noheaders --dynamic-table 2>&1 | \
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# RUN: FileCheck -DFILE=%t5.noheaders %s --check-prefix=WARN5-NOHEADERS
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# RUN: llvm-readelf %t5.noheaders --dynamic-table 2>&1 | \
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@ -133,7 +133,7 @@ Sections:
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Type: SHT_DYNAMIC
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Address: 0x1000
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Offset: 0x1000
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ShOffset: [[OFFSET=<none>]]
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ShOffset: [[OFFSET=0x1000]]
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Entries:
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- Tag: DT_NULL
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Value: 0
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@ -141,6 +141,5 @@ Sections:
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NoHeaders: [[NOHEADERS=false]]
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ProgramHeaders:
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- Type: PT_DYNAMIC
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FileSize: [[FILESIZE=<none>]]
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FirstSec: .dynamic
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LastSec: .dynamic
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FileSize: [[FILESIZE=0x10]]
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Offset: [[OFFSET=0x1000]]
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@ -436,28 +436,38 @@ Sections:
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# NOBITS-NEXT: Flags: [ PF_W, PF_R ]
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# NOBITS-NEXT: FirstSec: .bss
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# NOBITS-NEXT: LastSec: .bss
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# NOBITS-NEXT: Offset: 0x159
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# NOBITS-NEXT: VAddr: 0x1001
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# NOBITS-NEXT: Offset: 0x191
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# NOBITS-NEXT: - Type: PT_LOAD
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# NOBITS-NEXT: Flags: [ PF_W, PF_R ]
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# NOBITS-NEXT: FirstSec: .data.1
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# NOBITS-NEXT: LastSec: .bss
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# NOBITS-NEXT: Offset: 0x158
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# NOBITS-NEXT: VAddr: 0x1000
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# NOBITS-NEXT: Offset: 0x190
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# NOBITS-NEXT: - Type: PT_LOAD
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# NOBITS-NEXT: Flags: [ PF_W, PF_R ]
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# NOBITS-NEXT: FirstSec: .data.1
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# NOBITS-NEXT: LastSec: .data.2
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# NOBITS-NEXT: Offset: 0x158
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# NOBITS-NEXT: VAddr: 0x1000
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# NOBITS-NEXT: Offset: 0x190
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# NOBITS-NEXT: - Type: PT_LOAD
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# NOBITS-NEXT: Flags: [ PF_W, PF_R ]
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# NOBITS-NEXT: FirstSec: .bss
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# NOBITS-NEXT: LastSec: .data.2
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# NOBITS-NEXT: Offset: 0x159
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# NOBITS-NEXT: VAddr: 0x1001
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# NOBITS-NEXT: Offset: 0x191
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# NOBITS-NEXT: - Type: PT_LOAD
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# NOBITS-NEXT: Flags: [ PF_W, PF_R ]
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# NOBITS-NEXT: FirstSec: .foo.bss
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# NOBITS-NEXT: LastSec: .bar.bss
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# NOBITS-NEXT: VAddr: 0x200000000
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# NOBITS-NEXT: Offset: 0x15A
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# NOBITS-NEXT: Offset: 0x193
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# NOBITS-NEXT: - Type: PT_LOAD
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# NOBITS-NEXT: Flags: [ PF_W, PF_R ]
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# NOBITS-NEXT: FirstSec: .data.3
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# NOBITS-NEXT: LastSec: .bss.large
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# NOBITS-NEXT: VAddr: 0x200000030
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# NOBITS-NEXT: Offset: 0x193
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# NOBITS-NEXT: Sections:
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--- !ELF
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@ -471,27 +481,37 @@ ProgramHeaders:
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Flags: [ PF_W, PF_R ]
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FirstSec: .bss
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LastSec: .bss
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VAddr: 0x1001
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## Case 2: the SHT_NOBITS section is the last section in the segment.
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- Type: PT_LOAD
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Flags: [ PF_W, PF_R ]
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FirstSec: .data.1
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LastSec: .bss
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VAddr: 0x1000
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## Case 3: the SHT_NOBITS section is in the middle of the segment.
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- Type: PT_LOAD
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Flags: [ PF_W, PF_R ]
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FirstSec: .data.1
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LastSec: .data.2
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VAddr: 0x1000
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## Case 4: the SHT_NOBITS section is the first section in the segment.
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- Type: PT_LOAD
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Flags: [ PF_W, PF_R ]
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FirstSec: .bss
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LastSec: .data.2
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VAddr: 0x1001
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## Case 5: another two SHT_NOBITS sections in a different segment.
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- Type: PT_LOAD
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Flags: [ PF_W, PF_R ]
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FirstSec: .foo.bss
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LastSec: .bar.bss
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VAddr: 0x200000000
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## Case 6: a SHT_NOBITS section following a normal section, where the SHT_NOBITS size points past the end of the program header.
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- Type: PT_LOAD
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Flags: [ PF_W, PF_R ]
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FirstSec: .data.3
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LastSec: .bss.large
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VAddr: 0x200000030
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Sections:
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- Name: .data.1
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Type: SHT_PROGBITS
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@ -502,13 +522,13 @@ Sections:
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- Name: .bss
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Type: SHT_NOBITS
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Flags: [ SHF_WRITE, SHF_ALLOC ]
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## Use a size that is larger than the file size.
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ShSize: 0x00000000FFFFFFFF
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- Name: .data.2
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Type: SHT_PROGBITS
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Flags: [ SHF_WRITE, SHF_ALLOC ]
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## Use an arbitrary non-zero size.
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Size: 0x1
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- Name: .data.2
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Type: SHT_PROGBITS
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Flags: [ SHF_WRITE, SHF_ALLOC ]
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## Use an arbitrary size.
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Size: 0x1
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Size: 0x1
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- Name: .foo.bss
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Type: SHT_NOBITS
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Flags: [ SHF_WRITE, SHF_ALLOC ]
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@ -523,6 +543,19 @@ Sections:
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## Use an arbitrary size that is different to the size of
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## the previous section.
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Size: 0x20
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- Name: .data.3
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Type: SHT_PROGBITS
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Flags: [ SHF_WRITE, SHF_ALLOC ]
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## Use an abitrary size. Also use an address that is larger than the previous
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## section, because the tools expect segment addresses to be in order.
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Size: 0x1
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Address: 0x200000030
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- Name: .bss.large
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Type: SHT_NOBITS
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Flags: [ SHF_WRITE, SHF_ALLOC ]
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## Use a size that is larger than the file size.
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Size: 0x00000000FFFFFFFF
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Address: 0x200000031
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## Check that we require sections in a program header
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## declaration to be sorted by their offsets.
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@ -530,7 +563,6 @@ Sections:
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# RUN: FileCheck %s --check-prefix=UNSORTED --implicit-check-not="error:"
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# UNSORTED: error: program header with index 0: the section index of .bar is greater than the index of .foo
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# UNSORTED-NEXT: error: sections in the program header with index 3 are not sorted by their file offset
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--- !ELF
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FileHeader:
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@ -552,15 +584,6 @@ ProgramHeaders:
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FirstSec: .foo
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LastSec: .bar
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VAddr: 0x1000
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## Case 2: the .bar section is placed before the .zed section in the file,
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## but the sh_offset of .zed is less than the sh_offset of
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## the .bar section because of the "ShOffset" property.
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## Document we report an error for such a case.
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- Type: PT_LOAD
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Flags: [ PF_R ]
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FirstSec: .bar
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LastSec: .zed
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VAddr: 0x1001
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Sections:
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- Name: .foo
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Type: SHT_PROGBITS
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@ -571,11 +594,6 @@ Sections:
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Type: SHT_PROGBITS
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Flags: [ SHF_ALLOC ]
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Size: 0x1
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- Name: .zed
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Type: SHT_PROGBITS
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Flags: [ SHF_ALLOC ]
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Size: 0x1
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ShOffset: 0x0
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## Check how we dump segments which contain empty sections.
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# RUN: yaml2obj --docnum=7 %s -o %t7
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@ -44,25 +44,25 @@ Sections:
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- Name: .text
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Type: SHT_PROGBITS
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Size: 4
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ShOffset: 0x1000
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Offset: 0x1000
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AddressAlign: 0x1000
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- Name: .rodata
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Type: SHT_PROGBITS
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Size: 4
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ShOffset: 0x2000
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Offset: 0x2000
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AddressAlign: 0x1000
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- Name: .data
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Type: SHT_PROGBITS
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ShOffset: 0x2004
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Offset: 0x2004
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Size: 4
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- Name: .nobits1
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Type: SHT_NOBITS
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ShOffset: 0x2008
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Offset: 0x2008
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Size: 1
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- Name: .nobits2
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Type: SHT_NOBITS
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# Intentionally set to 0x2009 though the previous section is SHT_NOBITS.
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ShOffset: 0x2009
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Offset: 0x2009
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Size: 1
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ProgramHeaders:
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# Program header with no sections.
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@ -180,7 +180,7 @@ ProgramHeaders:
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# INVALID-OFFSET: yaml2obj: error: 'Offset' for segment with index 1 must be less than or equal to the minimum file offset of all included sections (0x78)
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## Document that the "Offset" value is checked after the section offset is overriden using "ShOffset".
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## Check "Offset" is used before the section offset is overriden using "ShOffset".
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# RUN: yaml2obj --docnum=4 %s -o %t5
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# RUN: llvm-readelf %t5 --sections --program-headers | FileCheck %s --check-prefix=SHOFFSET
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@ -188,7 +188,7 @@ ProgramHeaders:
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# SHOFFSET: [ 1] .foo PROGBITS 0000000000000000 ffffffff
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# SHOFFSET: Type Offset
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# SHOFFSET-NEXT: LOAD 0xffffff00
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# SHOFFSET-NEXT: LOAD 0x000078
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--- !ELF
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FileHeader:
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@ -200,11 +200,9 @@ Sections:
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Type: SHT_PROGBITS
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Flags: [ SHF_ALLOC ]
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Size: 0x1
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## Note: the real .foo offset is much less than 0xFFFFFFFF or
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## 0xFFFFFF00, but no error is reported.
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ShOffset: 0xFFFFFFFF
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ProgramHeaders:
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- Type: PT_LOAD
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Offset: 0xFFFFFF00
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Offset: 0x78
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FirstSec: .foo
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LastSec: .foo
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