LLVM 19.0.0git
BPFELFObjectWriter.cpp
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1//===-- BPFELFObjectWriter.cpp - BPF ELF Writer ---------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
12#include "llvm/MC/MCFixup.h"
14#include "llvm/MC/MCValue.h"
16#include <cstdint>
17
18using namespace llvm;
19
20namespace {
21
22class BPFELFObjectWriter : public MCELFObjectTargetWriter {
23public:
24 BPFELFObjectWriter(uint8_t OSABI);
25 ~BPFELFObjectWriter() override = default;
26
27protected:
28 unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
29 const MCFixup &Fixup, bool IsPCRel) const override;
30};
31
32} // end anonymous namespace
33
34BPFELFObjectWriter::BPFELFObjectWriter(uint8_t OSABI)
35 : MCELFObjectTargetWriter(/*Is64Bit*/ true, OSABI, ELF::EM_BPF,
36 /*HasRelocationAddend*/ false) {}
37
38unsigned BPFELFObjectWriter::getRelocType(MCContext &Ctx, const MCValue &Target,
39 const MCFixup &Fixup,
40 bool IsPCRel) const {
41 // determine the type of the relocation
42 switch (Fixup.getKind()) {
43 default:
44 llvm_unreachable("invalid fixup kind!");
45 case FK_SecRel_8:
46 // LD_imm64 instruction.
47 return ELF::R_BPF_64_64;
48 case FK_PCRel_4:
49 // CALL instruction.
50 return ELF::R_BPF_64_32;
51 case FK_Data_8:
52 return ELF::R_BPF_64_ABS64;
53 case FK_Data_4:
54 if (const MCSymbolRefExpr *A = Target.getSymA()) {
55 const MCSymbol &Sym = A->getSymbol();
56
57 if (Sym.isDefined()) {
58 MCSection &Section = Sym.getSection();
59 const MCSectionELF *SectionELF = dyn_cast<MCSectionELF>(&Section);
60 assert(SectionELF && "Null section for reloc symbol");
61
62 unsigned Flags = SectionELF->getFlags();
63
64 if (Sym.isTemporary()) {
65 // .BTF.ext generates FK_Data_4 relocations for
66 // insn offset by creating temporary labels.
67 // The reloc symbol should be in text section.
68 // Use a different relocation to instruct ExecutionEngine
69 // RuntimeDyld not to do relocation for it, yet still to
70 // allow lld to do proper adjustment when merging sections.
71 if ((Flags & ELF::SHF_ALLOC) && (Flags & ELF::SHF_EXECINSTR))
72 return ELF::R_BPF_64_NODYLD32;
73 } else {
74 // .BTF generates FK_Data_4 relocations for variable
75 // offset in DataSec kind.
76 // The reloc symbol should be in data section.
77 if ((Flags & ELF::SHF_ALLOC) && (Flags & ELF::SHF_WRITE))
78 return ELF::R_BPF_64_NODYLD32;
79 }
80 }
81 }
82 return ELF::R_BPF_64_ABS32;
83 }
84}
85
86std::unique_ptr<MCObjectTargetWriter>
88 return std::make_unique<BPFELFObjectWriter>(OSABI);
89}
basic Basic Alias true
static GCRegistry::Add< ErlangGC > A("erlang", "erlang-compatible garbage collector")
Symbol * Sym
Definition: ELF_riscv.cpp:479
PowerPC TLS Dynamic Call Fixup
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
Context object for machine code objects.
Definition: MCContext.h:81
virtual unsigned getRelocType(MCContext &Ctx, const MCValue &Target, const MCFixup &Fixup, bool IsPCRel) const =0
Encode information on a single operation to perform on a byte sequence (e.g., an encoded instruction)...
Definition: MCFixup.h:71
This represents a section on linux, lots of unix variants and some bare metal systems.
Definition: MCSectionELF.h:26
unsigned getFlags() const
Definition: MCSectionELF.h:73
Instances of this class represent a uniqued identifier for a section in the current translation unit.
Definition: MCSection.h:35
Represent a reference to a symbol from inside an expression.
Definition: MCExpr.h:192
MCSymbol - Instances of this class represent a symbol name in the MC file, and MCSymbols are created ...
Definition: MCSymbol.h:40
This represents an "assembler immediate".
Definition: MCValue.h:36
Target - Wrapper for Target specific information.
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
@ EM_BPF
Definition: ELF.h:319
@ SHF_ALLOC
Definition: ELF.h:1161
@ SHF_WRITE
Definition: ELF.h:1158
@ SHF_EXECINSTR
Definition: ELF.h:1164
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
@ FK_PCRel_4
A four-byte pc relative fixup.
Definition: MCFixup.h:30
@ FK_Data_8
A eight-byte fixup.
Definition: MCFixup.h:26
@ FK_Data_4
A four-byte fixup.
Definition: MCFixup.h:25
@ FK_SecRel_8
A eight-byte section relative fixup.
Definition: MCFixup.h:43
std::unique_ptr< MCObjectTargetWriter > createBPFELFObjectWriter(uint8_t OSABI)