[BPF] Remove relocation for patchable externs
Previously, patchable extern relocations are introduced to patch
external variables used for multi versioning in
compile once, run everywhere use case. The load instruction
will be converted into a move with an patchable immediate
which can be changed by bpf loader on the host.
The kernel verifier has evolved and is able to load
and propagate constant values, so compiler relocation
becomes unnecessary. This patch removed codes related to this.
Differential Revision: https://reviews.llvm.org/D68760
llvm-svn: 374367
diff --git a/llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp b/llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp
index 1b44281..400701c 100644
--- a/llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp
+++ b/llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp
@@ -93,8 +93,6 @@
namespace llvm {
const std::string BPFCoreSharedInfo::AmaAttr = "btf_ama";
-const std::string BPFCoreSharedInfo::PatchableExtSecName =
- ".BPF.patchable_externs";
} // namespace llvm
using namespace llvm;
diff --git a/llvm/lib/Target/BPF/BPFCORE.h b/llvm/lib/Target/BPF/BPFCORE.h
index a6cb3cf..ed47783 100644
--- a/llvm/lib/Target/BPF/BPFCORE.h
+++ b/llvm/lib/Target/BPF/BPFCORE.h
@@ -23,10 +23,8 @@
MAX_FIELD_RELOC_KIND,
};
- /// The attribute attached to globals representing a member offset
+ /// The attribute attached to globals representing a field access
static const std::string AmaAttr;
- /// The section name to identify a patchable external global
- static const std::string PatchableExtSecName;
};
} // namespace llvm
diff --git a/llvm/lib/Target/BPF/BPFMISimplifyPatchable.cpp b/llvm/lib/Target/BPF/BPFMISimplifyPatchable.cpp
index b363179..3321464 100644
--- a/llvm/lib/Target/BPF/BPFMISimplifyPatchable.cpp
+++ b/llvm/lib/Target/BPF/BPFMISimplifyPatchable.cpp
@@ -11,19 +11,15 @@
// ldd r2, r1, 0
// add r3, struct_base_reg, r2
//
-// Here @global should either present a AMA (abstruct member access) or
-// a patchable extern variable. And these two kinds of accesses
-// are subject to bpf load time patching. After this pass, the
+// Here @global should represent an AMA (abstruct member access).
+// Such an access is subject to bpf load time patching. After this pass, the
// code becomes
// ld_imm64 r1, @global
// add r3, struct_base_reg, r1
//
// Eventually, at BTF output stage, a relocation record will be generated
// for ld_imm64 which should be replaced later by bpf loader:
-// r1 = <calculated offset> or <to_be_patched_extern_val>
-// add r3, struct_base_reg, r1
-// or
-// ld_imm64 r1, <to_be_patched_extern_val>
+// r1 = <calculated field_info>
// add r3, struct_base_reg, r1
//
//===----------------------------------------------------------------------===//
@@ -120,15 +116,6 @@
if (GVar->hasAttribute(BPFCoreSharedInfo::AmaAttr)) {
assert(ImmVal == 0);
IsCandidate = true;
- } else if (!GVar->hasInitializer() && GVar->hasExternalLinkage() &&
- GVar->getSection() ==
- BPFCoreSharedInfo::PatchableExtSecName) {
- if (ImmVal == 0)
- IsCandidate = true;
- else
- errs() << "WARNING: unhandled patchable extern "
- << GVar->getName() << " with load offset " << ImmVal
- << "\n";
}
}
}
diff --git a/llvm/lib/Target/BPF/BTF.h b/llvm/lib/Target/BPF/BTF.h
index ef408da..a13c862 100644
--- a/llvm/lib/Target/BPF/BTF.h
+++ b/llvm/lib/Target/BPF/BTF.h
@@ -39,13 +39,6 @@
/// struct SecFieldReloc for ELF section #2
/// A number of struct BPFFieldReloc for ELF section #2
/// ...
-/// The ExternReloc subsection is defined as below:
-/// BPFExternReloc Size
-/// struct SecExternReloc for ELF section #1
-/// A number of struct BPFExternReloc for ELF section #1
-/// struct SecExternReloc for ELF section #2
-/// A number of struct BPFExternReloc for ELF section #2
-/// ...
///
/// The section formats are also defined at
/// https://github.com/torvalds/linux/blob/master/include/uapi/linux/btf.h
@@ -63,7 +56,7 @@
/// Sizes in bytes of various things in the BTF format.
enum {
HeaderSize = 24,
- ExtHeaderSize = 40,
+ ExtHeaderSize = 32,
CommonTypeSize = 12,
BTFArraySize = 12,
BTFEnumSize = 8,
@@ -73,11 +66,9 @@
SecFuncInfoSize = 8,
SecLineInfoSize = 8,
SecFieldRelocSize = 8,
- SecExternRelocSize = 8,
BPFFuncInfoSize = 8,
BPFLineInfoSize = 16,
BPFFieldRelocSize = 16,
- BPFExternRelocSize = 8,
};
/// The .BTF section header definition.
@@ -215,8 +206,6 @@
uint32_t LineInfoLen; ///< Length of line info section
uint32_t FieldRelocOff; ///< Offset of offset reloc section
uint32_t FieldRelocLen; ///< Length of offset reloc section
- uint32_t ExternRelocOff; ///< Offset of extern reloc section
- uint32_t ExternRelocLen; ///< Length of extern reloc section
};
/// Specifying one function info.
@@ -260,18 +249,6 @@
uint32_t NumFieldReloc; ///< Number of offset reloc's in this section
};
-/// Specifying one offset relocation.
-struct BPFExternReloc {
- uint32_t InsnOffset; ///< Byte offset in this section
- uint32_t ExternNameOff; ///< The string for external variable
-};
-
-/// Specifying extern relocation's in one section.
-struct SecExternReloc {
- uint32_t SecNameOff; ///< Section name index in the .BTF string table
- uint32_t NumExternReloc; ///< Number of extern reloc's in this section
-};
-
} // End namespace BTF.
} // End namespace llvm.
diff --git a/llvm/lib/Target/BPF/BTFDebug.cpp b/llvm/lib/Target/BPF/BTFDebug.cpp
index a8f8573..db551e7 100644
--- a/llvm/lib/Target/BPF/BTFDebug.cpp
+++ b/llvm/lib/Target/BPF/BTFDebug.cpp
@@ -752,9 +752,10 @@
}
void BTFDebug::emitBTFExtSection() {
- // Do not emit section if empty FuncInfoTable and LineInfoTable.
+ // Do not emit section if empty FuncInfoTable and LineInfoTable
+ // and FieldRelocTable.
if (!FuncInfoTable.size() && !LineInfoTable.size() &&
- !FieldRelocTable.size() && !ExternRelocTable.size())
+ !FieldRelocTable.size())
return;
MCContext &Ctx = OS.getContext();
@@ -766,8 +767,8 @@
// Account for FuncInfo/LineInfo record size as well.
uint32_t FuncLen = 4, LineLen = 4;
- // Do not account for optional FieldReloc/ExternReloc.
- uint32_t FieldRelocLen = 0, ExternRelocLen = 0;
+ // Do not account for optional FieldReloc.
+ uint32_t FieldRelocLen = 0;
for (const auto &FuncSec : FuncInfoTable) {
FuncLen += BTF::SecFuncInfoSize;
FuncLen += FuncSec.second.size() * BTF::BPFFuncInfoSize;
@@ -780,15 +781,9 @@
FieldRelocLen += BTF::SecFieldRelocSize;
FieldRelocLen += FieldRelocSec.second.size() * BTF::BPFFieldRelocSize;
}
- for (const auto &ExternRelocSec : ExternRelocTable) {
- ExternRelocLen += BTF::SecExternRelocSize;
- ExternRelocLen += ExternRelocSec.second.size() * BTF::BPFExternRelocSize;
- }
if (FieldRelocLen)
FieldRelocLen += 4;
- if (ExternRelocLen)
- ExternRelocLen += 4;
OS.EmitIntValue(0, 4);
OS.EmitIntValue(FuncLen, 4);
@@ -796,8 +791,6 @@
OS.EmitIntValue(LineLen, 4);
OS.EmitIntValue(FuncLen + LineLen, 4);
OS.EmitIntValue(FieldRelocLen, 4);
- OS.EmitIntValue(FuncLen + LineLen + FieldRelocLen, 4);
- OS.EmitIntValue(ExternRelocLen, 4);
// Emit func_info table.
OS.AddComment("FuncInfo");
@@ -848,22 +841,6 @@
}
}
}
-
- // Emit extern reloc table.
- if (ExternRelocLen) {
- OS.AddComment("ExternReloc");
- OS.EmitIntValue(BTF::BPFExternRelocSize, 4);
- for (const auto &ExternRelocSec : ExternRelocTable) {
- OS.AddComment("Extern reloc section string offset=" +
- std::to_string(ExternRelocSec.first));
- OS.EmitIntValue(ExternRelocSec.first, 4);
- OS.EmitIntValue(ExternRelocSec.second.size(), 4);
- for (const auto &ExternRelocInfo : ExternRelocSec.second) {
- Asm->EmitLabelReference(ExternRelocInfo.Label, 4);
- OS.EmitIntValue(ExternRelocInfo.ExternNameOff, 4);
- }
- }
- }
}
void BTFDebug::beginFunctionImpl(const MachineFunction *MF) {
@@ -1019,15 +996,6 @@
MDNode *MDN = GVar->getMetadata(LLVMContext::MD_preserve_access_index);
DIType *Ty = dyn_cast<DIType>(MDN);
generateFieldReloc(MI, ORSym, Ty, GVar->getName());
- } else if (GVar && !GVar->hasInitializer() && GVar->hasExternalLinkage() &&
- GVar->getSection() == BPFCoreSharedInfo::PatchableExtSecName) {
- MCSymbol *ORSym = OS.getContext().createTempSymbol();
- OS.EmitLabel(ORSym);
-
- BTFExternReloc ExternReloc;
- ExternReloc.Label = ORSym;
- ExternReloc.ExternNameOff = addString(GVar->getName());
- ExternRelocTable[SecNameOff].push_back(ExternReloc);
}
}
}
@@ -1165,20 +1133,6 @@
OutMI.addOperand(MCOperand::createReg(MI->getOperand(0).getReg()));
OutMI.addOperand(MCOperand::createImm(Imm));
return true;
- } else if (GVar && !GVar->hasInitializer() &&
- GVar->hasExternalLinkage() &&
- GVar->getSection() == BPFCoreSharedInfo::PatchableExtSecName) {
- const IntegerType *IntTy = dyn_cast<IntegerType>(GVar->getValueType());
- assert(IntTy);
- // For patchable externals, emit "LD_imm64, ri, 0" if the external
- // variable is 64bit width, emit "mov ri, 0" otherwise.
- if (IntTy->getBitWidth() == 64)
- OutMI.setOpcode(BPF::LD_imm64);
- else
- OutMI.setOpcode(BPF::MOV_ri);
- OutMI.addOperand(MCOperand::createReg(MI->getOperand(0).getReg()));
- OutMI.addOperand(MCOperand::createImm(0));
- return true;
}
}
}
diff --git a/llvm/lib/Target/BPF/BTFDebug.h b/llvm/lib/Target/BPF/BTFDebug.h
index eec8614..c01e0d1 100644
--- a/llvm/lib/Target/BPF/BTFDebug.h
+++ b/llvm/lib/Target/BPF/BTFDebug.h
@@ -231,12 +231,6 @@
uint32_t RelocKind; ///< What to patch the instruction
};
-/// Represent one extern relocation.
-struct BTFExternReloc {
- const MCSymbol *Label; ///< MCSymbol identifying insn for the reloc
- uint32_t ExternNameOff; ///< The extern variable name
-};
-
/// Collect and emit BTF information.
class BTFDebug : public DebugHandlerBase {
MCStreamer &OS;
@@ -251,7 +245,6 @@
std::map<uint32_t, std::vector<BTFFuncInfo>> FuncInfoTable;
std::map<uint32_t, std::vector<BTFLineInfo>> LineInfoTable;
std::map<uint32_t, std::vector<BTFFieldReloc>> FieldRelocTable;
- std::map<uint32_t, std::vector<BTFExternReloc>> ExternRelocTable;
StringMap<std::vector<std::string>> FileContent;
std::map<std::string, std::unique_ptr<BTFKindDataSec>> DataSecEntries;
std::vector<BTFTypeStruct *> StructTypes;