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[llvm] Update call graph ELF section type. #164461

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Merged
merged 7 commits into from
Oct 22, 2025
Merged

[llvm] Update call graph ELF section type. #164461

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fd620a5
[llvm] Update call graph ELF section type.
Prabhuk Oct 21, 2025
81240cf
Rename type and add doc.
Prabhuk Oct 21, 2025
7c2b6e8
Remove unnecessary empty lines from doc.
Prabhuk Oct 22, 2025
121879a
Minor alignment fixes to doc code snippet.
Prabhuk Oct 22, 2025
346457d
Cover ELFYAML.cpp
Prabhuk Oct 22, 2025
4e2577a
Merge branch 'main' into cg_section_type
Prabhuk Oct 22, 2025
33c82c4
Add YAML test for call graph section type.
Prabhuk Oct 22, 2025
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31 changes: 31 additions & 0 deletions llvm/docs/Extensions.rst
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Expand Up @@ -601,6 +601,37 @@ sees fit (generally the section that would provide the best locality).

.. _CFI jump table: https://clang.llvm.org/docs/ControlFlowIntegrityDesign.html#forward-edge-cfi-for-indirect-function-calls

``SHT_LLVM_CALL_GRAPH`` Section (Call Graph)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

This section is used to store the call graph. It has a type of
``SHT_LLVM_CALL_GRAPH`` (0x6fff4c0f). Details of call graph section layout
are described in :doc:`CallGraphSection`.

For example:

.. code-block:: gas

.section ".llvm.callgraph","",@llvm_call_graph
.byte 0
.byte 7
.quad .Lball
.quad 0
.byte 3
.quad foo
.quad bar
.quad baz
.byte 3
.quad 4524972987496481828
.quad 3498816979441845844
.quad 8646233951371320954

This indicates that ``ball`` calls ``foo``, ``bar`` and ``baz`` directly;
``ball`` indirectly calls functions whose types are ``4524972987496481828``,
``3498816979441845844`` and ``8646233951371320954``.



CodeView-Dependent
------------------

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1 change: 1 addition & 0 deletions llvm/include/llvm/BinaryFormat/ELF.h
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Expand Up @@ -1185,6 +1185,7 @@ enum : unsigned {
SHT_LLVM_LTO = 0x6fff4c0c, // .llvm.lto for fat LTO.
SHT_LLVM_JT_SIZES = 0x6fff4c0d, // LLVM jump tables sizes.
SHT_LLVM_CFI_JUMP_TABLE = 0x6fff4c0e, // LLVM CFI jump table.
SHT_LLVM_CALL_GRAPH = 0x6fff4c0f, // LLVM Call Graph Section.
// Android's experimental support for SHT_RELR sections.
// https://android.googlesource.com/platform/bionic/+/b7feec74547f84559a1467aca02708ff61346d2a/libc/include/elf.h#512
SHT_ANDROID_RELR = 0x6fffff00, // Relocation entries; only offsets.
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2 changes: 2 additions & 0 deletions llvm/lib/MC/MCAsmInfoELF.cpp
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Expand Up @@ -197,6 +197,8 @@ void MCAsmInfoELF::printSwitchToSection(const MCSection &Section,
OS << "llvm_jt_sizes";
else if (Sec.Type == ELF::SHT_LLVM_CFI_JUMP_TABLE)
OS << "llvm_cfi_jump_table";
else if (Sec.Type == ELF::SHT_LLVM_CALL_GRAPH)
OS << "llvm_call_graph";
else
OS << "0x" << Twine::utohexstr(Sec.Type);

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4 changes: 2 additions & 2 deletions llvm/lib/MC/MCObjectFileInfo.cpp
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Expand Up @@ -554,7 +554,7 @@ void MCObjectFileInfo::initELFMCObjectFileInfo(const Triple &T, bool Large) {
Ctx->getELFSection(".sframe", ELF::SHT_GNU_SFRAME, ELF::SHF_ALLOC);

CallGraphSection =
Ctx->getELFSection(".llvm.callgraph", ELF::SHT_PROGBITS, 0);
Ctx->getELFSection(".llvm.callgraph", ELF::SHT_LLVM_CALL_GRAPH, 0);

StackSizesSection = Ctx->getELFSection(".stack_sizes", ELF::SHT_PROGBITS, 0);

Expand Down Expand Up @@ -1172,7 +1172,7 @@ MCObjectFileInfo::getCallGraphSection(const MCSection &TextSec) const {
}

return Ctx->getELFSection(
".llvm.callgraph", ELF::SHT_PROGBITS, Flags, 0, GroupName,
".llvm.callgraph", ELF::SHT_LLVM_CALL_GRAPH, Flags, 0, GroupName,
/*IsComdat=*/true, ElfSec.getUniqueID(),
static_cast<const MCSymbolELF *>(TextSec.getBeginSymbol()));
}
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2 changes: 2 additions & 0 deletions llvm/lib/MC/MCParser/ELFAsmParser.cpp
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Expand Up @@ -637,6 +637,8 @@ bool ELFAsmParser::parseSectionArguments(bool IsPush, SMLoc loc) {
Type = ELF::SHT_LLVM_JT_SIZES;
else if (TypeName == "llvm_cfi_jump_table")
Type = ELF::SHT_LLVM_CFI_JUMP_TABLE;
else if (TypeName == "llvm_call_graph")
Type = ELF::SHT_LLVM_CALL_GRAPH;
else if (TypeName.getAsInteger(0, Type))
return TokError("unknown section type");
}
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1 change: 1 addition & 0 deletions llvm/lib/Object/ELF.cpp
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Expand Up @@ -322,6 +322,7 @@ StringRef llvm::object::getELFSectionTypeName(uint32_t Machine, unsigned Type) {
STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_LTO);
STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_JT_SIZES)
STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_CFI_JUMP_TABLE)
STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_CALL_GRAPH);
STRINGIFY_ENUM_CASE(ELF, SHT_GNU_SFRAME);
STRINGIFY_ENUM_CASE(ELF, SHT_GNU_ATTRIBUTES);
STRINGIFY_ENUM_CASE(ELF, SHT_GNU_HASH);
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2 changes: 1 addition & 1 deletion llvm/test/CodeGen/ARM/call-graph-section-addrtaken.ll
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Expand Up @@ -27,7 +27,7 @@ entry:
!1 = !{i64 0, !"_ZTSFivE.generalized"}
!2 = !{i64 0, !"_ZTSFviE.generalized"}

; CHECK: .section .llvm.callgraph,"o",%progbits,.text
; CHECK: .section .llvm.callgraph,"o",%llvm_call_graph,.text
;; Version
; CHECK-NEXT: .byte 0
;; Flags -- Potential indirect target so LSB is set to 1. Other bits are 0.
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2 changes: 1 addition & 1 deletion llvm/test/CodeGen/ARM/call-graph-section-assembly.ll
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Expand Up @@ -36,7 +36,7 @@ entry:
!4 = !{!5}
!5 = !{i64 0, !"_ZTSFPvS_E.generalized"}

; CHECK: .section .llvm.callgraph,"o",%progbits,.text
; CHECK: .section .llvm.callgraph,"o",%llvm_call_graph,.text
;; Version
; CHECK-NEXT: .byte 0
;; Flags
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2 changes: 1 addition & 1 deletion llvm/test/CodeGen/X86/call-graph-section-addrtaken.ll
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Expand Up @@ -27,7 +27,7 @@ entry:
!1 = !{i64 0, !"_ZTSFivE.generalized"}
!2 = !{i64 0, !"_ZTSFviE.generalized"}

; CHECK: .section .llvm.callgraph,"o",@progbits,.text
; CHECK: .section .llvm.callgraph,"o",@llvm_call_graph,.text
;; Version
; CHECK-NEXT: .byte 0
;; Flags -- Potential indirect target so LSB is set to 1. Other bits are 0.
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2 changes: 1 addition & 1 deletion llvm/test/CodeGen/X86/call-graph-section-assembly.ll
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Expand Up @@ -36,7 +36,7 @@ entry:
!4 = !{!5}
!5 = !{i64 0, !"_ZTSFPvS_E.generalized"}

; CHECK: .section .llvm.callgraph,"o",@progbits,.text
; CHECK: .section .llvm.callgraph,"o",@llvm_call_graph,.text
;; Version
; CHECK-NEXT: .byte 0
;; Flags
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