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[MC] Add support for the .rva assembler directive for COFF targets
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Even though gas doesn't document it, it has been supported there for
a very long time.

This produces the 32 bit relative virtual address (aka image relative
address) for a given symbol. ".rva foo" is essentially equal to
".long foo@imgrel".

Differential Revision: https://reviews.llvm.org/D49821

llvm-svn: 338063
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@mstorsjo
mstorsjo committed Jul 26, 2018
1 parent e6e75bf commit 390bce4
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Showing 7 changed files with 103 additions and 2 deletions.
5 changes: 5 additions & 0 deletions llvm/include/llvm/MC/MCStreamer.h
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Expand Up @@ -522,6 +522,11 @@ class MCStreamer {
/// \param Symbol - Symbol the section relative relocation should point to.
virtual void EmitCOFFSecRel32(MCSymbol const *Symbol, uint64_t Offset);

/// Emits a COFF image relative relocation.
///
/// \param Symbol - Symbol the image relative relocation should point to.
virtual void EmitCOFFImgRel32(MCSymbol const *Symbol, int64_t Offset);

/// Emit an ELF .size directive.
///
/// This corresponds to an assembler statement such as:
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1 change: 1 addition & 0 deletions llvm/include/llvm/MC/MCWinCOFFStreamer.h
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Expand Up @@ -54,6 +54,7 @@ class MCWinCOFFStreamer : public MCObjectStreamer {
void EmitCOFFSymbolIndex(MCSymbol const *Symbol) override;
void EmitCOFFSectionIndex(MCSymbol const *Symbol) override;
void EmitCOFFSecRel32(MCSymbol const *Symbol, uint64_t Offset) override;
void EmitCOFFImgRel32(MCSymbol const *Symbol, int64_t Offset) override;
void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
unsigned ByteAlignment) override;
void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
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11 changes: 11 additions & 0 deletions llvm/lib/MC/MCAsmStreamer.cpp
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Expand Up @@ -165,6 +165,7 @@ class MCAsmStreamer final : public MCStreamer {
void EmitCOFFSymbolIndex(MCSymbol const *Symbol) override;
void EmitCOFFSectionIndex(MCSymbol const *Symbol) override;
void EmitCOFFSecRel32(MCSymbol const *Symbol, uint64_t Offset) override;
void EmitCOFFImgRel32(MCSymbol const *Symbol, int64_t Offset) override;
void emitELFSize(MCSymbol *Symbol, const MCExpr *Value) override;
void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
unsigned ByteAlignment) override;
Expand Down Expand Up @@ -706,6 +707,16 @@ void MCAsmStreamer::EmitCOFFSecRel32(MCSymbol const *Symbol, uint64_t Offset) {
EmitEOL();
}

void MCAsmStreamer::EmitCOFFImgRel32(MCSymbol const *Symbol, int64_t Offset) {
OS << "\t.rva\t";
Symbol->print(OS, MAI);
if (Offset > 0)
OS << '+' << Offset;
else if (Offset < 0)
OS << '-' << -Offset;
EmitEOL();
}

void MCAsmStreamer::emitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
assert(MAI->hasDotTypeDotSizeDirective());
OS << "\t.size\t";
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33 changes: 33 additions & 0 deletions llvm/lib/MC/MCParser/COFFAsmParser.cpp
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Expand Up @@ -69,6 +69,7 @@ class COFFAsmParser : public MCAsmParserExtension {
addDirectiveHandler<&COFFAsmParser::ParseDirectiveSafeSEH>(".safeseh");
addDirectiveHandler<&COFFAsmParser::ParseDirectiveSecIdx>(".secidx");
addDirectiveHandler<&COFFAsmParser::ParseDirectiveLinkOnce>(".linkonce");
addDirectiveHandler<&COFFAsmParser::ParseDirectiveRVA>(".rva");

// Win64 EH directives.
addDirectiveHandler<&COFFAsmParser::ParseSEHDirectiveStartProc>(
Expand Down Expand Up @@ -134,6 +135,7 @@ class COFFAsmParser : public MCAsmParserExtension {
bool ParseDirectiveSymIdx(StringRef, SMLoc);
bool parseCOMDATType(COFF::COMDATType &Type);
bool ParseDirectiveLinkOnce(StringRef, SMLoc);
bool ParseDirectiveRVA(StringRef, SMLoc);

// Win64 EH directives.
bool ParseSEHDirectiveStartProc(StringRef, SMLoc);
Expand Down Expand Up @@ -492,6 +494,37 @@ bool COFFAsmParser::ParseDirectiveSecRel32(StringRef, SMLoc) {
return false;
}

bool COFFAsmParser::ParseDirectiveRVA(StringRef, SMLoc) {
auto parseOp = [&]() -> bool {
StringRef SymbolID;
if (getParser().parseIdentifier(SymbolID))
return TokError("expected identifier in directive");

int64_t Offset = 0;
SMLoc OffsetLoc;
if (getLexer().is(AsmToken::Plus) || getLexer().is(AsmToken::Minus)) {
OffsetLoc = getLexer().getLoc();
if (getParser().parseAbsoluteExpression(Offset))
return true;
}

if (Offset < std::numeric_limits<int32_t>::min() ||
Offset > std::numeric_limits<int32_t>::max())
return Error(OffsetLoc, "invalid '.rva' directive offset, can't be less "
"than -2147483648 or greater than "
"2147483647");

MCSymbol *Symbol = getContext().getOrCreateSymbol(SymbolID);

getStreamer().EmitCOFFImgRel32(Symbol, Offset);
return false;
};

if (getParser().parseMany(parseOp))
return addErrorSuffix(" in directive");
return false;
}

bool COFFAsmParser::ParseDirectiveSafeSEH(StringRef, SMLoc) {
StringRef SymbolID;
if (getParser().parseIdentifier(SymbolID))
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2 changes: 2 additions & 0 deletions llvm/lib/MC/MCStreamer.cpp
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Expand Up @@ -830,6 +830,8 @@ void MCStreamer::EmitCOFFSectionIndex(MCSymbol const *Symbol) {

void MCStreamer::EmitCOFFSecRel32(MCSymbol const *Symbol, uint64_t Offset) {}

void MCStreamer::EmitCOFFImgRel32(MCSymbol const *Symbol, int64_t Offset) {}

/// EmitRawText - If this file is backed by an assembly streamer, this dumps
/// the specified string in the output .s file. This capability is
/// indicated by the hasRawTextSupport() predicate.
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19 changes: 19 additions & 0 deletions llvm/lib/MC/MCWinCOFFStreamer.cpp
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Expand Up @@ -232,6 +232,25 @@ void MCWinCOFFStreamer::EmitCOFFSecRel32(const MCSymbol *Symbol,
DF->getContents().resize(DF->getContents().size() + 4, 0);
}

void MCWinCOFFStreamer::EmitCOFFImgRel32(const MCSymbol *Symbol,
int64_t Offset) {
visitUsedSymbol(*Symbol);
MCDataFragment *DF = getOrCreateDataFragment();
// Create Symbol A for the relocation relative reference.
const MCExpr *MCE = MCSymbolRefExpr::create(
Symbol, MCSymbolRefExpr::VK_COFF_IMGREL32, getContext());
// Add the constant offset, if given.
if (Offset)
MCE = MCBinaryExpr::createAdd(
MCE, MCConstantExpr::create(Offset, getContext()), getContext());
// Build the imgrel relocation.
MCFixup Fixup = MCFixup::create(DF->getContents().size(), MCE, FK_Data_4);
// Record the relocation.
DF->getFixups().push_back(Fixup);
// Emit 4 bytes (zeros) to the object file.
DF->getContents().resize(DF->getContents().size() + 4, 0);
}

void MCWinCOFFStreamer::EmitCommonSymbol(MCSymbol *S, uint64_t Size,
unsigned ByteAlignment) {
auto *Symbol = cast<MCSymbolCOFF>(S);
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34 changes: 32 additions & 2 deletions llvm/test/MC/COFF/relocation-imgrel.s
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Expand Up @@ -3,27 +3,57 @@
// Test that we produce image-relative relocations (IMAGE_REL_I386_DIR32NB
// and IMAGE_REL_AMD64_ADDR32NB) when accessing foo@imgrel.

// RUN: llvm-mc -filetype=obj -triple i686-pc-win32 %s | llvm-readobj -r | FileCheck --check-prefix=W32 %s
// RUN: llvm-mc -filetype=obj -triple x86_64-pc-win32 %s | llvm-readobj -r | FileCheck --check-prefix=W64 %s
// RUN: llvm-mc -filetype=obj -triple i686-pc-win32 %s > %t.w32.obj
// RUN: llvm-readobj -r %t.w32.obj | FileCheck --check-prefix=W32 %s
// RUN: llvm-objdump -s %t.w32.obj | FileCheck --check-prefix=W32OBJ %s
// RUN: llvm-mc -filetype=obj -triple x86_64-pc-win32 %s > %t.w64.obj
// RUN: llvm-readobj -r %t.w64.obj | FileCheck --check-prefix=W64 %s
// RUN: llvm-objdump -s %t.w64.obj | FileCheck --check-prefix=W64OBJ %s

.data
foo:
.long 1
.long .Llabel@imgrel
.rva .Llabel, .Llabel + 16, foo, .Lother - 3

.text
.Llabel:
mov foo@IMGREL(%ebx, %ecx, 4), %eax
.Lother:
mov foo@imgrel(%ebx, %ecx, 4), %eax

// W32: Relocations [
// W32-NEXT: Section (1) .text {
// W32-NEXT: 0x3 IMAGE_REL_I386_DIR32NB foo
// W32-NEXT: 0xA IMAGE_REL_I386_DIR32NB foo
// W32-NEXT: }
// W32-NEXT: Section (2) .data {
// W32-NEXT: 0x4 IMAGE_REL_I386_DIR32NB .Llabel
// W32-NEXT: 0x8 IMAGE_REL_I386_DIR32NB .Llabel
// W32-NEXT: 0xC IMAGE_REL_I386_DIR32NB .Llabel
// W32-NEXT: 0x10 IMAGE_REL_I386_DIR32NB foo
// W32-NEXT: 0x14 IMAGE_REL_I386_DIR32NB .Lother
// W32-NEXT: }
// W32-NEXT: ]

// W32OBJ: Contents of section .data:
// W32OBJ-NEXT: 0000 01000000 00000000 00000000 10000000
// W32OBJ-NEXT: 0010 00000000 fdffffff

// W64: Relocations [
// W64-NEXT: Section (1) .text {
// W64-NEXT: 0x4 IMAGE_REL_AMD64_ADDR32NB foo
// W64-NEXT: 0xC IMAGE_REL_AMD64_ADDR32NB foo
// W64-NEXT: }
// W64-NEXT: Section (2) .data {
// W64-NEXT: 0x4 IMAGE_REL_AMD64_ADDR32NB .text
// W64-NEXT: 0x8 IMAGE_REL_AMD64_ADDR32NB .text
// W64-NEXT: 0xC IMAGE_REL_AMD64_ADDR32NB .text
// W64-NEXT: 0x10 IMAGE_REL_AMD64_ADDR32NB foo
// W64-NEXT: 0x14 IMAGE_REL_AMD64_ADDR32NB .text
// W64-NEXT: }
// W64-NEXT: ]

// W64OBJ: Contents of section .data:
// W64OBJ-NEXT: 0000 01000000 00000000 00000000 10000000
// W64OBJ-NEXT: 0010 00000000 05000000

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