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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
2b7f229
Add the check for the order of Offset and ShOffset
Jul 1, 2025
f943ab1
Fix tests about the change of `ShOffset` overriding timing
Jul 3, 2025
7908868
Fix comment format of program-header.yaml
Jul 11, 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
11 changes: 5 additions & 6 deletions 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 @@ -91,7 +91,7 @@

## Case D: the same as "Case C", but for a 32-bit object.

# RUN: yaml2obj %s -DBITS=32 -DOFFSET=0xffffffff -o %t5
# RUN: yaml2obj %s -DBITS=32 -DFILESIZE=8 -DOFFSET=0xffffffff -o %t5
# RUN: llvm-readobj %t5 --dynamic-table 2>&1 | FileCheck -DFILE=%t5 %s \
# RUN: --check-prefix=WARN5 --implicit-check-not=warning:
# RUN: llvm-readelf %t5 --dynamic-table 2>&1 | FileCheck -DFILE=%t5 %s \
Expand All @@ -101,7 +101,7 @@
# 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)
# WARN5: warning: '[[FILE]]': no valid dynamic table was found

# RUN: yaml2obj %s -DNOHEADERS=true -DBITS=32 -DOFFSET=0xffffffff -o %t5.noheaders
# RUN: yaml2obj %s -DNOHEADERS=true -DBITS=32 -DFILESIZE=8 -DOFFSET=0xffffffff -o %t5.noheaders
# RUN: llvm-readobj %t5.noheaders --dynamic-table 2>&1 | \
# RUN: FileCheck -DFILE=%t5.noheaders %s --check-prefix=WARN5-NOHEADERS
# RUN: llvm-readelf %t5.noheaders --dynamic-table 2>&1 | \
Expand Down Expand Up @@ -133,14 +133,13 @@ Sections:
Type: SHT_DYNAMIC
Address: 0x1000
Offset: 0x1000
ShOffset: [[OFFSET=<none>]]
ShOffset: [[OFFSET=0x1000]]
Entries:
- Tag: DT_NULL
Value: 0
- Type: SectionHeaderTable
NoHeaders: [[NOHEADERS=false]]
ProgramHeaders:
- Type: PT_DYNAMIC
FileSize: [[FILESIZE=<none>]]
FirstSec: .dynamic
LastSec: .dynamic
FileSize: [[FILESIZE=0x10]]
Offset: [[OFFSET=0x1000]]
70 changes: 44 additions & 26 deletions llvm/test/tools/obj2yaml/ELF/program-headers.yaml
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Original file line number Diff line number Diff line change
Expand Up @@ -436,28 +436,38 @@ Sections:
# NOBITS-NEXT: Flags: [ PF_W, PF_R ]
# NOBITS-NEXT: FirstSec: .bss
# NOBITS-NEXT: LastSec: .bss
# NOBITS-NEXT: Offset: 0x159
# NOBITS-NEXT: VAddr: 0x1001
# NOBITS-NEXT: Offset: 0x191
# NOBITS-NEXT: - Type: PT_LOAD
# NOBITS-NEXT: Flags: [ PF_W, PF_R ]
# NOBITS-NEXT: FirstSec: .data.1
# NOBITS-NEXT: LastSec: .bss
# NOBITS-NEXT: Offset: 0x158
# NOBITS-NEXT: VAddr: 0x1000
# NOBITS-NEXT: Offset: 0x190
# NOBITS-NEXT: - Type: PT_LOAD
# NOBITS-NEXT: Flags: [ PF_W, PF_R ]
# NOBITS-NEXT: FirstSec: .data.1
# NOBITS-NEXT: LastSec: .data.2
# NOBITS-NEXT: Offset: 0x158
# NOBITS-NEXT: VAddr: 0x1000
# NOBITS-NEXT: Offset: 0x190
# NOBITS-NEXT: - Type: PT_LOAD
# NOBITS-NEXT: Flags: [ PF_W, PF_R ]
# NOBITS-NEXT: FirstSec: .bss
# NOBITS-NEXT: LastSec: .data.2
# NOBITS-NEXT: Offset: 0x159
# NOBITS-NEXT: VAddr: 0x1001
# NOBITS-NEXT: Offset: 0x191
# NOBITS-NEXT: - Type: PT_LOAD
# NOBITS-NEXT: Flags: [ PF_W, PF_R ]
# NOBITS-NEXT: FirstSec: .foo.bss
# NOBITS-NEXT: LastSec: .bar.bss
# NOBITS-NEXT: VAddr: 0x200000000
# NOBITS-NEXT: Offset: 0x15A
# NOBITS-NEXT: Offset: 0x193
# NOBITS-NEXT: - Type: PT_LOAD
# NOBITS-NEXT: Flags: [ PF_W, PF_R ]
# NOBITS-NEXT: FirstSec: .data.3
# NOBITS-NEXT: LastSec: .bss.large
# NOBITS-NEXT: VAddr: 0x200000030
# NOBITS-NEXT: Offset: 0x193
# NOBITS-NEXT: Sections:

--- !ELF
Expand All @@ -471,27 +481,37 @@ ProgramHeaders:
Flags: [ PF_W, PF_R ]
FirstSec: .bss
LastSec: .bss
VAddr: 0x1001
## Case 2: the SHT_NOBITS section is the last section in the segment.
- Type: PT_LOAD
Flags: [ PF_W, PF_R ]
FirstSec: .data.1
LastSec: .bss
VAddr: 0x1000
## Case 3: the SHT_NOBITS section is in the middle of the segment.
- Type: PT_LOAD
Flags: [ PF_W, PF_R ]
FirstSec: .data.1
LastSec: .data.2
VAddr: 0x1000
## Case 4: the SHT_NOBITS section is the first section in the segment.
- Type: PT_LOAD
Flags: [ PF_W, PF_R ]
FirstSec: .bss
LastSec: .data.2
VAddr: 0x1001
## Case 5: another two SHT_NOBITS sections in a different segment.
- Type: PT_LOAD
Flags: [ PF_W, PF_R ]
FirstSec: .foo.bss
LastSec: .bar.bss
VAddr: 0x200000000
## Case 6: a SHT_NOBITS section following a normal section, where the SHT_NOBITS size points past the end of the program header.
- Type: PT_LOAD
Flags: [ PF_W, PF_R ]
FirstSec: .data.3
LastSec: .bss.large
VAddr: 0x200000030
Sections:
- Name: .data.1
Type: SHT_PROGBITS
Expand All @@ -502,13 +522,13 @@ Sections:
- Name: .bss
Type: SHT_NOBITS
Flags: [ SHF_WRITE, SHF_ALLOC ]
## Use a size that is larger than the file size.
ShSize: 0x00000000FFFFFFFF
- Name: .data.2
Type: SHT_PROGBITS
Flags: [ SHF_WRITE, SHF_ALLOC ]
## Use an arbitrary non-zero size.
Size: 0x1
- Name: .data.2
Type: SHT_PROGBITS
Flags: [ SHF_WRITE, SHF_ALLOC ]
## Use an arbitrary size.
Size: 0x1
Size: 0x1
- Name: .foo.bss
Type: SHT_NOBITS
Flags: [ SHF_WRITE, SHF_ALLOC ]
Expand All @@ -523,14 +543,26 @@ Sections:
## Use an arbitrary size that is different to the size of
## the previous section.
Size: 0x20
- Name: .data.3
Type: SHT_PROGBITS
Flags: [ SHF_WRITE, SHF_ALLOC ]
## Use an abitrary size. Also use an address that is larger than the previous
## section, because the tools expect segment addresses to be in order.
Size: 0x1
Address: 0x200000030
- Name: .bss.large
Type: SHT_NOBITS
Flags: [ SHF_WRITE, SHF_ALLOC ]
## Use a size that is larger than the file size.
Size: 0x00000000FFFFFFFF
Address: 0x200000031

## Check that we require sections in a program header
## declaration to be sorted by their offsets.
# RUN: not yaml2obj --docnum=6 %s -o %t6 2>&1 | \
# RUN: FileCheck %s --check-prefix=UNSORTED --implicit-check-not="error:"

# UNSORTED: error: program header with index 0: the section index of .bar is greater than the index of .foo
# UNSORTED-NEXT: error: sections in the program header with index 3 are not sorted by their file offset

--- !ELF
FileHeader:
Expand All @@ -552,15 +584,6 @@ ProgramHeaders:
FirstSec: .foo
LastSec: .bar
VAddr: 0x1000
## Case 2: the .bar section is placed before the .zed section in the file,
## but the sh_offset of .zed is less than the sh_offset of
## the .bar section because of the "ShOffset" property.
## Document we report an error for such a case.
- Type: PT_LOAD
Flags: [ PF_R ]
FirstSec: .bar
LastSec: .zed
VAddr: 0x1001
Sections:
- Name: .foo
Type: SHT_PROGBITS
Expand All @@ -571,11 +594,6 @@ Sections:
Type: SHT_PROGBITS
Flags: [ SHF_ALLOC ]
Size: 0x1
- Name: .zed
Type: SHT_PROGBITS
Flags: [ SHF_ALLOC ]
Size: 0x1
ShOffset: 0x0

## Check how we dump segments which contain empty sections.
# RUN: yaml2obj --docnum=7 %s -o %t7
Expand Down
16 changes: 8 additions & 8 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 @@ -180,15 +180,15 @@ ProgramHeaders:

# 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".
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Rather than outright delete this test case, we should update it to show that the opposite is true, i.e. that the offset check happens before ShOffset is applied.

## Check "Offset" is used before 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
# SHOFFSET-NEXT: LOAD 0x000078

--- !ELF
FileHeader:
Expand All @@ -205,6 +205,6 @@ Sections:
ShOffset: 0xFFFFFFFF
ProgramHeaders:
- Type: PT_LOAD
Offset: 0xFFFFFF00
Offset: 0x78
FirstSec: .foo
LastSec: .foo
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