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[llvm][yaml2obj] Modify section header overriding timing #130942

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[llvm][yaml2obj] Modify section header overriding timing #130942

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701efbe
[llvm][yaml2obj] Modify section header overriding timing
cabbaken Mar 12, 2025
f079240
Distinguish ShOffset and Offset in program-header-size-offset.yaml, r…
cabbaken Mar 17, 2025
9260c30
Modify malformed-pt-dynamic.test to fix program header offset
cabbaken Mar 17, 2025
db32881
Optimize code style
cabbaken Mar 17, 2025
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22 changes: 18 additions & 4 deletions llvm/lib/ObjectYAML/ELFEmitter.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -206,6 +206,9 @@ template <class ELFT> class ELFState {
NameToIdxMap DynSymN2I;
ELFYAML::Object &Doc;

std::vector<std::pair<Elf_Shdr *, ELFYAML::Section>>
SectionHeadersOverrideHelper;

StringSet<> ExcludedSectionHeaders;

uint64_t LocationCounter = 0;
Expand All @@ -226,6 +229,7 @@ template <class ELFT> class ELFState {
StringRef SecName, ELFYAML::Section *YAMLSec);
void initSectionHeaders(std::vector<Elf_Shdr> &SHeaders,
ContiguousBlobAccumulator &CBA);
void overrideSectionHeaders(std::vector<Elf_Shdr> &SHeaders);
void initSymtabSectionHeader(Elf_Shdr &SHeader, SymtabType STType,
ContiguousBlobAccumulator &CBA,
ELFYAML::Section *YAMLSec);
Expand Down Expand Up @@ -845,7 +849,7 @@ void ELFState<ELFT>::initSectionHeaders(std::vector<Elf_Shdr> &SHeaders,
}

LocationCounter += SHeader.sh_size;
overrideFields<ELFT>(Sec, SHeader);
SectionHeadersOverrideHelper.push_back({&SHeader, *Sec});
continue;
}

Expand Down Expand Up @@ -899,12 +903,17 @@ void ELFState<ELFT>::initSectionHeaders(std::vector<Elf_Shdr> &SHeaders,
}

LocationCounter += SHeader.sh_size;

// Override section fields if requested.
overrideFields<ELFT>(Sec, SHeader);
SectionHeadersOverrideHelper.push_back({&SHeader, *Sec});
}
}

template <class ELFT>
void ELFState<ELFT>::overrideSectionHeaders(std::vector<Elf_Shdr> &SHeaders) {
for (std::pair<Elf_Shdr *, ELFYAML::Section> &HeaderAndSec :
SectionHeadersOverrideHelper)
overrideFields<ELFT>(&HeaderAndSec.second, *HeaderAndSec.first);
}

template <class ELFT>
void ELFState<ELFT>::assignSectionAddress(Elf_Shdr &SHeader,
ELFYAML::Section *YAMLSec) {
Expand Down Expand Up @@ -2090,6 +2099,11 @@ bool ELFState<ELFT>::writeELF(raw_ostream &OS, ELFYAML::Object &Doc,
// Now we can decide segment offsets.
State.setProgramHeaderLayout(PHeaders, SHeaders);

// Override section fields, if requested. This needs to happen after program
// header layout happens, because otherwise the layout will use the new
// values.
State.overrideSectionHeaders(SHeaders);

bool ReachedLimit = CBA.getOffset() > MaxSize;
if (Error E = CBA.takeLimitError()) {
// We report a custom error message instead below.
Expand Down
2 changes: 1 addition & 1 deletion llvm/test/tools/llvm-readobj/ELF/malformed-pt-dynamic.test
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Original file line number Diff line number Diff line change
Expand Up @@ -133,7 +133,6 @@ Sections:
Type: SHT_DYNAMIC
Address: 0x1000
Offset: 0x1000
ShOffset: [[OFFSET=<none>]]
Entries:
- Tag: DT_NULL
Value: 0
Expand All @@ -142,5 +141,6 @@ Sections:
ProgramHeaders:
- Type: PT_DYNAMIC
FileSize: [[FILESIZE=<none>]]
Offset: [[OFFSET=<none>]]
FirstSec: .dynamic
LastSec: .dynamic
39 changes: 5 additions & 34 deletions llvm/test/tools/yaml2obj/ELF/program-header-size-offset.yaml
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Original file line number Diff line number Diff line change
Expand Up @@ -44,25 +44,25 @@ Sections:
- Name: .text
Type: SHT_PROGBITS
Size: 4
ShOffset: 0x1000
Offset: 0x1000
AddressAlign: 0x1000
- Name: .rodata
Type: SHT_PROGBITS
Size: 4
ShOffset: 0x2000
Offset: 0x2000
AddressAlign: 0x1000
- Name: .data
Type: SHT_PROGBITS
ShOffset: 0x2004
Offset: 0x2004
Size: 4
- Name: .nobits1
Type: SHT_NOBITS
ShOffset: 0x2008
Offset: 0x2008
Size: 1
- Name: .nobits2
Type: SHT_NOBITS
# Intentionally set to 0x2009 though the previous section is SHT_NOBITS.
ShOffset: 0x2009
Offset: 0x2009
Size: 1
ProgramHeaders:
# Program header with no sections.
Expand Down Expand Up @@ -179,32 +179,3 @@ ProgramHeaders:
# RUN: FileCheck %s --check-prefix=INVALID-OFFSET

# 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)

## Document that the "Offset" value is checked after the section offset is overriden using "ShOffset".
# RUN: yaml2obj --docnum=4 %s -o %t5
# RUN: llvm-readelf %t5 --sections --program-headers | FileCheck %s --check-prefix=SHOFFSET

# SHOFFSET: [Nr] Name Type Address Off
# SHOFFSET: [ 1] .foo PROGBITS 0000000000000000 ffffffff

# SHOFFSET: Type Offset
# SHOFFSET-NEXT: LOAD 0xffffff00

--- !ELF
FileHeader:
Class: ELFCLASS64
Data: ELFDATA2LSB
Type: ET_EXEC
Sections:
- Name: .foo
Type: SHT_PROGBITS
Flags: [ SHF_ALLOC ]
Size: 0x1
## Note: the real .foo offset is much less than 0xFFFFFFFF or
## 0xFFFFFF00, but no error is reported.
ShOffset: 0xFFFFFFFF
ProgramHeaders:
- Type: PT_LOAD
Offset: 0xFFFFFF00
FirstSec: .foo
LastSec: .foo
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