intel/llvm
1
0
Fork 0
mirror of https://github.com/intel/llvm.git synced 2026-01-20 10:58:11 +08:00
Code Issues Packages Projects Releases Wiki Activity

[WebAssembly] Add new relocation for location relative data

Browse Source 
This `R_WASM_MEMORY_ADDR_SELFREL_I32` relocation represents an offset
between its relocating address and the symbol address. It's very similar
to `R_X86_64_PC32` but restricted to be used for only data segments.

```
S + A - P
```

A: Represents the addend used to compute the value of the relocatable
field.
P: Represents the place of the storage unit being relocated.
S: Represents the value of the symbol whose index resides in the
relocation entry.

Proposal: https://github.com/WebAssembly/tool-conventions/issues/162

Differential Revision: https://reviews.llvm.org/D96659
This commit is contained in:
Yuta Saito
2021-03-08 11:23:33 -08:00
committed by Sam Clegg
parent d9a29a6752
commit aa0c571a5f
13 changed files with 226 additions and 28 deletions
Download Patch File Download Diff File Expand all files Collapse all files

89
lld/test/wasm/reloc-relative.s Normal file
View File

@@ -0,0 +1,89 @@
# RUN: llvm-mc -filetype=obj -triple=wasm32-unknown-unknown %p/Inputs/hello.s -o %t.hello32.o
# RUN: llvm-mc -filetype=obj -triple=wasm32-unknown-unknown %s -o %t.o
# RUN: wasm-ld --no-entry --no-gc-sections --allow-undefined -fatal-warnings -o %t.wasm %t.o %t.hello32.o
# RUN: obj2yaml %t.wasm | FileCheck %s
.section .x_sec,"",@
internal_x_seg_pad:
# padding for provisioning value assertion
.int32 0
.size internal_x_seg_pad, 4
internal_x_seg:
.int32 42
.size internal_x_seg, 4
# internal cross segment subtraction
.section .foo,"",@
.globl foo
foo:
.int32 internal_x_seg - foo
.size foo, 4
foo_addend:
.int32 internal_x_seg - foo
.size foo_addend, 4
# external cross segment subtraction
.section .bar,"",@
.globl bar
bar:
.int32 hello_str - bar
.size bar, 4
bar_addend:
.int32 hello_str - bar
.size bar_addend, 4
# positive calc result
.section .fizz,"",@
.globl fizz
fizz:
.int32 far - fizz
.size fizz, 4
fizz_addend:
.int32 far - fizz
.size fizz_addend, 4
.section .far,"",@
.globl far
far:
.int32 21
.size far, 4
# CHECK: - Type: DATA
# CHECK-NEXT: Segments:
# CHECK-NEXT: - SectionOffset: 7
# CHECK-NEXT: InitFlags: 0
# CHECK-NEXT: Offset:
# CHECK-NEXT: Opcode: I32_CONST
# CHECK-NEXT: Value: 1024
# CHECK-NEXT: Content: 68656C6C6F0A00
# CHECK-NEXT: - SectionOffset: 20
# CHECK-NEXT: InitFlags: 0
# CHECK-NEXT: Offset:
# CHECK-NEXT: Opcode: I32_CONST
# CHECK-NEXT: Value: 1031
# CHECK-NEXT: Content: 000000002A000000
# CHECK-NEXT: - SectionOffset: 34
# CHECK-NEXT: InitFlags: 0
# CHECK-NEXT: Offset:
# CHECK-NEXT: Opcode: I32_CONST
# CHECK-NEXT: Value: 1039
# CHECK-NEXT: Content: FCFFFFFFFCFFFFFF
# CHECK-NEXT: - SectionOffset: 48
# CHECK-NEXT: InitFlags: 0
# CHECK-NEXT: Offset:
# CHECK-NEXT: Opcode: I32_CONST
# CHECK-NEXT: Value: 1047
# CHECK-NEXT: Content: E9FFFFFFE9FFFFFF
# CHECK-NEXT: - SectionOffset: 62
# CHECK-NEXT: InitFlags: 0
# CHECK-NEXT: Offset:
# CHECK-NEXT: Opcode: I32_CONST
# CHECK-NEXT: Value: 1055
# CHECK-NEXT: Content: '0800000008000000'
# CHECK-NEXT: - SectionOffset: 76
# CHECK-NEXT: InitFlags: 0
# CHECK-NEXT: Offset:
# CHECK-NEXT: Opcode: I32_CONST
# CHECK-NEXT: Value: 1063
# CHECK-NEXT: Content: '15000000'

12
lld/wasm/InputChunks.cpp
View File

@@ -94,6 +94,7 @@ void InputChunk::verifyRelocTargets() const {
case R_WASM_FUNCTION_OFFSET_I32:
case R_WASM_SECTION_OFFSET_I32:
case R_WASM_GLOBAL_INDEX_I32:
case R_WASM_MEMORY_ADDR_LOCREL_I32:
existingValue = read32le(loc);
break;
case R_WASM_TABLE_INDEX_I64:
@@ -139,7 +140,7 @@ void InputChunk::writeTo(uint8_t *buf) const {
for (const WasmRelocation &rel : relocations) {
uint8_t *loc = buf + rel.Offset + off;
auto value = file->calcNewValue(rel, tombstone);
auto value = file->calcNewValue(rel, tombstone, this);
LLVM_DEBUG(dbgs() << "apply reloc: type=" << relocTypeToString(rel.Type));
if (rel.Type != R_WASM_TYPE_INDEX_LEB)
LLVM_DEBUG(dbgs() << " sym=" << file->getSymbols()[rel.Index]->getName());
@@ -176,6 +177,7 @@ void InputChunk::writeTo(uint8_t *buf) const {
case R_WASM_FUNCTION_OFFSET_I32:
case R_WASM_SECTION_OFFSET_I32:
case R_WASM_GLOBAL_INDEX_I32:
case R_WASM_MEMORY_ADDR_LOCREL_I32:
write32le(loc, value);
break;
case R_WASM_TABLE_INDEX_I64:
@@ -302,7 +304,8 @@ void InputFunction::calculateSize() {
for (const WasmRelocation &rel : relocations) {
LLVM_DEBUG(dbgs() << " region: " << (rel.Offset - lastRelocEnd) << "\n");
compressedFuncSize += rel.Offset - lastRelocEnd;
compressedFuncSize += getRelocWidth(rel, file->calcNewValue(rel, tombstone));
compressedFuncSize +=
getRelocWidth(rel, file->calcNewValue(rel, tombstone, this));
lastRelocEnd = rel.Offset + getRelocWidthPadded(rel);
}
LLVM_DEBUG(dbgs() << " final region: " << (end - lastRelocEnd) << "\n");
@@ -343,7 +346,8 @@ void InputFunction::writeTo(uint8_t *buf) const {
LLVM_DEBUG(dbgs() << " write chunk: " << chunkSize << "\n");
memcpy(buf, lastRelocEnd, chunkSize);
buf += chunkSize;
buf += writeCompressedReloc(buf, rel, file->calcNewValue(rel, tombstone));
buf += writeCompressedReloc(buf, rel,
file->calcNewValue(rel, tombstone, this));
lastRelocEnd = secStart + rel.Offset + getRelocWidthPadded(rel);
}
@@ -416,7 +420,7 @@ void InputSegment::generateRelocationCode(raw_ostream &os) const {
writeU8(os, WASM_OPCODE_GLOBAL_GET, "GLOBAL_GET");
writeUleb128(os, baseSymbol->getGlobalIndex(), "base");
writeU8(os, opcode_reloc_const, "CONST");
writeSleb128(os, file->calcNewValue(rel, tombstone), "offset");
writeSleb128(os, file->calcNewValue(rel, tombstone, this), "offset");
writeU8(os, opcode_reloc_add, "ADD");
}

20
lld/wasm/InputFiles.cpp
View File

@@ -126,6 +126,7 @@ uint64_t ObjFile::calcNewAddend(const WasmRelocation &reloc) const {
case R_WASM_MEMORY_ADDR_TLS_SLEB:
case R_WASM_FUNCTION_OFFSET_I32:
case R_WASM_FUNCTION_OFFSET_I64:
case R_WASM_MEMORY_ADDR_LOCREL_I32:
return reloc.Addend;
case R_WASM_SECTION_OFFSET_I32:
return getSectionSymbol(reloc.Index)->section->getOffset(reloc.Addend);
@@ -158,7 +159,8 @@ uint64_t ObjFile::calcExpectedValue(const WasmRelocation &reloc) const {
case R_WASM_MEMORY_ADDR_REL_SLEB64:
case R_WASM_MEMORY_ADDR_I32:
case R_WASM_MEMORY_ADDR_I64:
case R_WASM_MEMORY_ADDR_TLS_SLEB: {
case R_WASM_MEMORY_ADDR_TLS_SLEB:
case R_WASM_MEMORY_ADDR_LOCREL_I32: {
const WasmSymbol &sym = wasmObj->syms()[reloc.Index];
if (sym.isUndefined())
return 0;
@@ -199,7 +201,8 @@ uint64_t ObjFile::calcExpectedValue(const WasmRelocation &reloc) const {
}
// Translate from the relocation's index into the final linked output value.
uint64_t ObjFile::calcNewValue(const WasmRelocation &reloc, uint64_t tombstone) const {
uint64_t ObjFile::calcNewValue(const WasmRelocation &reloc, uint64_t tombstone,
const InputChunk *chunk) const {
const Symbol* sym = nullptr;
if (reloc.Type != R_WASM_TYPE_INDEX_LEB) {
sym = symbols[reloc.Index];
@@ -234,7 +237,8 @@ uint64_t ObjFile::calcNewValue(const WasmRelocation &reloc, uint64_t tombstone)
case R_WASM_MEMORY_ADDR_REL_SLEB:
case R_WASM_MEMORY_ADDR_REL_SLEB64:
case R_WASM_MEMORY_ADDR_I32:
case R_WASM_MEMORY_ADDR_I64: {
case R_WASM_MEMORY_ADDR_I64:
case R_WASM_MEMORY_ADDR_LOCREL_I32: {
if (isa<UndefinedData>(sym) || sym->isUndefWeak())
return 0;
auto D = cast<DefinedData>(sym);
@@ -245,7 +249,15 @@ uint64_t ObjFile::calcNewValue(const WasmRelocation &reloc, uint64_t tombstone)
// backward compat with old object files built with `-fPIC`.
if (D->segment && D->segment->outputSeg->name == ".tdata")
return D->getOutputSegmentOffset() + reloc.Addend;
return D->getVA(reloc.Addend);
uint64_t value = D->getVA(reloc.Addend);
if (reloc.Type == R_WASM_MEMORY_ADDR_LOCREL_I32) {
const auto *segment = cast<InputSegment>(chunk);
uint64_t p = segment->outputSeg->startVA + segment->outputSegmentOffset +
reloc.Offset - segment->getInputSectionOffset();
value -= p;
}
return value;
}
case R_WASM_MEMORY_ADDR_TLS_SLEB:
if (isa<UndefinedData>(sym) || sym->isUndefWeak())

3
lld/wasm/InputFiles.h
View File

@@ -119,7 +119,8 @@ public:
void dumpInfo() const;
uint32_t calcNewIndex(const WasmRelocation &reloc) const;
uint64_t calcNewValue(const WasmRelocation &reloc, uint64_t tombstone) const;
uint64_t calcNewValue(const WasmRelocation &reloc, uint64_t tombstone,
const InputChunk *chunk) const;
uint64_t calcNewAddend(const WasmRelocation &reloc) const;
uint64_t calcExpectedValue(const WasmRelocation &reloc) const;
Symbol *getSymbol(const WasmRelocation &reloc) const {

1
llvm/include/llvm/BinaryFormat/WasmRelocs.def
View File

@@ -25,3 +25,4 @@ WASM_RELOC(R_WASM_TABLE_INDEX_I64, 19)
WASM_RELOC(R_WASM_TABLE_NUMBER_LEB, 20)
WASM_RELOC(R_WASM_MEMORY_ADDR_TLS_SLEB, 21)
WASM_RELOC(R_WASM_FUNCTION_OFFSET_I64, 22)
WASM_RELOC(R_WASM_MEMORY_ADDR_LOCREL_I32, 23)

4
llvm/include/llvm/MC/MCWasmObjectWriter.h
View File

@@ -33,8 +33,8 @@ public:
return W->getFormat() == Triple::Wasm;
}
virtual unsigned getRelocType(const MCValue &Target,
const MCFixup &Fixup) const = 0;
virtual unsigned getRelocType(const MCValue &Target, const MCFixup &Fixup,
bool IsLocRel) const = 0;
/// \name Accessors
/// @{

1
llvm/lib/BinaryFormat/Wasm.cpp
View File

@@ -52,6 +52,7 @@ bool llvm::wasm::relocTypeHasAddend(uint32_t Type) {
case R_WASM_FUNCTION_OFFSET_I32:
case R_WASM_FUNCTION_OFFSET_I64:
case R_WASM_SECTION_OFFSET_I32:
case R_WASM_MEMORY_ADDR_LOCREL_I32:
return true;
default:
return false;

40
llvm/lib/MC/WasmObjectWriter.cpp
View File

@@ -445,17 +445,35 @@ void WasmObjectWriter::recordRelocation(MCAssembler &Asm,
uint64_t C = Target.getConstant();
uint64_t FixupOffset = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
MCContext &Ctx = Asm.getContext();
bool IsLocRel = false;
if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
// To get here the A - B expression must have failed evaluateAsRelocatable.
// This means either A or B must be undefined and in WebAssembly we can't
// support either of those cases.
const auto &SymB = cast<MCSymbolWasm>(RefB->getSymbol());
Ctx.reportError(
Fixup.getLoc(),
Twine("symbol '") + SymB.getName() +
"': unsupported subtraction expression used in relocation.");
return;
if (FixupSection.getKind().isText()) {
Ctx.reportError(Fixup.getLoc(),
Twine("symbol '") + SymB.getName() +
"' unsupported subtraction expression used in "
"relocation in code section.");
return;
}
if (SymB.isUndefined()) {
Ctx.reportError(Fixup.getLoc(),
Twine("symbol '") + SymB.getName() +
"' can not be undefined in a subtraction expression");
return;
}
const MCSection &SecB = SymB.getSection();
if (&SecB != &FixupSection) {
Ctx.reportError(Fixup.getLoc(),
Twine("symbol '") + SymB.getName() +
"' can not be placed in a different section");
return;
}
IsLocRel = true;
C += FixupOffset - Layout.getSymbolOffset(SymB);
}
// We either rejected the fixup or folded B into C at this point.
@@ -480,7 +498,7 @@ void WasmObjectWriter::recordRelocation(MCAssembler &Asm,
// be negative and don't wrap.
FixedValue = 0;
unsigned Type = TargetObjectWriter->getRelocType(Target, Fixup);
unsigned Type = TargetObjectWriter->getRelocType(Target, Fixup, IsLocRel);
// Absolute offset within a section or a function.
// Currently only supported for for metadata sections.
@@ -611,7 +629,8 @@ WasmObjectWriter::getProvisionalValue(const WasmRelocationEntry &RelEntry,
case wasm::R_WASM_MEMORY_ADDR_REL_SLEB64:
case wasm::R_WASM_MEMORY_ADDR_I32:
case wasm::R_WASM_MEMORY_ADDR_I64:
case wasm::R_WASM_MEMORY_ADDR_TLS_SLEB: {
case wasm::R_WASM_MEMORY_ADDR_TLS_SLEB:
case wasm::R_WASM_MEMORY_ADDR_LOCREL_I32: {
// Provisional value is address of the global plus the offset
// For undefined symbols, use zero
if (!RelEntry.Symbol->isDefined())
@@ -707,6 +726,7 @@ void WasmObjectWriter::applyRelocations(
case wasm::R_WASM_FUNCTION_OFFSET_I32:
case wasm::R_WASM_SECTION_OFFSET_I32:
case wasm::R_WASM_GLOBAL_INDEX_I32:
case wasm::R_WASM_MEMORY_ADDR_LOCREL_I32:
patchI32(Stream, Value, Offset);
break;
case wasm::R_WASM_TABLE_INDEX_I64:

2
llvm/lib/Object/RelocationResolver.cpp
View File

@@ -575,6 +575,7 @@ static bool supportsWasm32(uint64_t Type) {
case wasm::R_WASM_EVENT_INDEX_LEB:
case wasm::R_WASM_GLOBAL_INDEX_I32:
case wasm::R_WASM_TABLE_NUMBER_LEB:
case wasm::R_WASM_MEMORY_ADDR_LOCREL_I32:
return true;
default:
return false;
@@ -611,6 +612,7 @@ static uint64_t resolveWasm32(uint64_t Type, uint64_t Offset, uint64_t S,
case wasm::R_WASM_EVENT_INDEX_LEB:
case wasm::R_WASM_GLOBAL_INDEX_I32:
case wasm::R_WASM_TABLE_NUMBER_LEB:
case wasm::R_WASM_MEMORY_ADDR_LOCREL_I32:
// For wasm section, its offset at 0 -- ignoring Value
return LocData;
default:

2
llvm/lib/Object/WasmObjectFile.cpp
View File

@@ -905,6 +905,7 @@ Error WasmObjectFile::parseRelocSection(StringRef Name, ReadContext &Ctx) {
case wasm::R_WASM_MEMORY_ADDR_I32:
case wasm::R_WASM_MEMORY_ADDR_REL_SLEB:
case wasm::R_WASM_MEMORY_ADDR_TLS_SLEB:
case wasm::R_WASM_MEMORY_ADDR_LOCREL_I32:
if (!isValidDataSymbol(Reloc.Index))
return make_error<GenericBinaryError>("invalid relocation data index",
object_error::parse_failed);
@@ -953,6 +954,7 @@ Error WasmObjectFile::parseRelocSection(StringRef Name, ReadContext &Ctx) {
Size = 10;
if (Reloc.Type == wasm::R_WASM_TABLE_INDEX_I32 ||
Reloc.Type == wasm::R_WASM_MEMORY_ADDR_I32 ||
Reloc.Type == wasm::R_WASM_MEMORY_ADDR_LOCREL_I32 ||
Reloc.Type == wasm::R_WASM_SECTION_OFFSET_I32 ||
Reloc.Type == wasm::R_WASM_FUNCTION_OFFSET_I32 ||
Reloc.Type == wasm::R_WASM_GLOBAL_INDEX_I32)

10
llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyWasmObjectWriter.cpp
View File

@@ -34,8 +34,8 @@ public:
explicit WebAssemblyWasmObjectWriter(bool Is64Bit, bool IsEmscripten);
private:
unsigned getRelocType(const MCValue &Target,
const MCFixup &Fixup) const override;
unsigned getRelocType(const MCValue &Target, const MCFixup &Fixup,
bool IsLocRel) const override;
};
} // end anonymous namespace
@@ -63,7 +63,8 @@ static const MCSection *getFixupSection(const MCExpr *Expr) {
}
unsigned WebAssemblyWasmObjectWriter::getRelocType(const MCValue &Target,
const MCFixup &Fixup) const {
const MCFixup &Fixup,
bool IsLocRel) const {
const MCSymbolRefExpr *RefA = Target.getSymA();
assert(RefA);
auto& SymA = cast<MCSymbolWasm>(RefA->getSymbol());
@@ -122,7 +123,8 @@ unsigned WebAssemblyWasmObjectWriter::getRelocType(const MCValue &Target,
else if (!Section->isWasmData())
return wasm::R_WASM_SECTION_OFFSET_I32;
}
return wasm::R_WASM_MEMORY_ADDR_I32;
return IsLocRel ? wasm::R_WASM_MEMORY_ADDR_LOCREL_I32
: wasm::R_WASM_MEMORY_ADDR_I32;
case FK_Data_8:
if (SymA.isFunction())
return wasm::R_WASM_TABLE_INDEX_I64;

22
llvm/test/MC/WebAssembly/bad-fixup-expr.s
View File

@@ -13,6 +13,22 @@ bar:
.int8 1
.size bar, 1
.section .data.fizz,"",@
fizz:
.int8 1
.size fizz, 1
.section .data.segment1,"",@
segment1:
// CHECK: 'bar' can not be placed in a different section
.int32 fizz-bar
// CHECK: 'undef_baz' can not be undefined in a subtraction expression
.int32 fizz-undef_baz
// CHECK: 'fizz' can not be placed in a different section
.int32 undef_baz-fizz
.size segment1, 12
.text
.section .text.main,"",@
main:
@@ -23,10 +39,10 @@ main:
i32.const foo-foo_other+2
i32.const foo_other-foo-10
// CHECK: 'bar': unsupported subtraction expression used in relocation
// CHECK: 'bar' unsupported subtraction expression used in relocation in code section.
i32.const foo-bar
// CHECK: 'undef_baz': unsupported subtraction expression used in relocation
// CHECK: 'undef_baz' unsupported subtraction expression used in relocation in code section.
i32.const foo-undef_baz
// CHECK: 'foo': unsupported subtraction expression used in relocation
// CHECK: 'foo' unsupported subtraction expression used in relocation in code section.
i32.const undef_baz-foo
end_function

48
llvm/test/MC/WebAssembly/reloc-relative.ll Normal file
View File

@@ -0,0 +1,48 @@
; RUN: llc -O0 -filetype=obj %s -o - | llvm-readobj -r --expand-relocs - | FileCheck %s
; CHECK: Format: WASM
; CHECK: Relocations [
; CHECK-NEXT: Section (3) DATA {
; CHECK-NEXT: Relocation {
; CHECK-NEXT: Type: R_WASM_MEMORY_ADDR_LOCREL_I32 (23)
; CHECK-NEXT: Offset: 0x6
; CHECK-NEXT: Symbol: foo
; CHECK-NEXT: Addend: 0
; CHECK-NEXT: }
; CHECK-NEXT: Relocation {
; CHECK-NEXT: Type: R_WASM_MEMORY_ADDR_LOCREL_I32 (23)
; CHECK-NEXT: Offset: 0xA
; CHECK-NEXT: Symbol: fizz
; CHECK-NEXT: Addend: 0
; CHECK-NEXT: }
; CHECK-NEXT: Relocation {
; CHECK-NEXT: Type: R_WASM_MEMORY_ADDR_LOCREL_I32 (23)
; CHECK-NEXT: Offset: 0x17
; CHECK-NEXT: Symbol: foo
; CHECK-NEXT: Addend: 4
; CHECK-NEXT: }
; CHECK-NEXT: }
; CHECK-NEXT: ]
target triple = "wasm32-unknown-unknown"
; @foo - @bar
@foo = external global i32, align 4
@bar = constant i32 sub (
i32 ptrtoint (i32* @foo to i32),
i32 ptrtoint (i32* @bar to i32)
), section ".sec1"
; @foo - @addend + 4
@fizz = constant i32 42, align 4, section ".sec2"
@addend = constant i32 sub (
i32 ptrtoint (i32* @foo to i32),
i32 ptrtoint (i32* @fizz to i32)
), section ".sec2"
@x_sec = constant i32 sub (
i32 ptrtoint (i32* @fizz to i32),
i32 ptrtoint (i32* @x_sec to i32)
), section ".sec1"