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[AArch64][MachO] Add ptrauth ABI version to arm64e cpusubtype. (#104650)

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In a mach_header, the cpusubtype is a 32-bit field, but it's split in 2
subfields:
- the low 24 bits containing the cpu subtype proper, (e.g.,
CPU_SUBTYPE_ARM64E 2)
- the high 8 bits containing a capability field used for additional
feature flags.

Notably, it's only the subtype subfield that participates in fat file
slice discrimination: the caps are ignored.

arm64e uses the caps subfield to encode a ptrauth ABI version:
- 0x80 (CPU_SUBTYPE_PTRAUTH_ABI) denotes a versioned binary
- 0x40 denotes a kernel-ABI binary
- 0x00-0x0F holds the ptrauth ABI version

This teaches the basic obj tools to decode that (or ignore it when
unneeded).

It also teaches the MachO writer to default to emitting versioned
binaries, but with a version of 0 (and without the kernel ABI flag).

Modern arm64e requires versioned binaries: a binary with 0x00 caps in
cpusubtype is now rejected by the linker and everything after. We can
live without the sophistication of specifying the version and kernel ABI
for now.

Co-authored-by: Francis Visoiu Mistrih <francisvm@apple.com>
This commit is contained in:
Ahmed Bougacha
2024-08-20 11:37:12 -07:00
committed by GitHub
parent f73050e722
commit fd4f9520a6
13 changed files with 191 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files

33
llvm/include/llvm/BinaryFormat/MachO.h
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@@ -1641,8 +1641,39 @@ enum CPUSubTypeARM64 {
CPU_SUBTYPE_ARM64_ALL = 0,
CPU_SUBTYPE_ARM64_V8 = 1,
CPU_SUBTYPE_ARM64E = 2,
// arm64e uses the capability bits to encode ptrauth ABI information.
// Bit 63 marks the binary as Versioned.
CPU_SUBTYPE_ARM64E_VERSIONED_PTRAUTH_ABI_MASK = 0x80000000,
// Bit 62 marks the binary as using a kernel ABI.
CPU_SUBTYPE_ARM64E_KERNEL_PTRAUTH_ABI_MASK = 0x40000000,
// Bits [59:56] hold the 4-bit ptrauth ABI version.
CPU_SUBTYPE_ARM64E_PTRAUTH_MASK = 0x0f000000,
};
inline int CPU_SUBTYPE_ARM64E_PTRAUTH_VERSION(unsigned ST) {
return (ST & CPU_SUBTYPE_ARM64E_PTRAUTH_MASK) >> 24;
}
inline unsigned
CPU_SUBTYPE_ARM64E_WITH_PTRAUTH_VERSION(unsigned PtrAuthABIVersion,
bool PtrAuthKernelABIVersion) {
assert((PtrAuthABIVersion <= 0xF) &&
"ptrauth abi version must fit in 4 bits");
return CPU_SUBTYPE_ARM64E | CPU_SUBTYPE_ARM64E_VERSIONED_PTRAUTH_ABI_MASK |
(PtrAuthKernelABIVersion ? CPU_SUBTYPE_ARM64E_KERNEL_PTRAUTH_ABI_MASK
: 0) |
(PtrAuthABIVersion << 24);
}
inline unsigned CPU_SUBTYPE_ARM64E_IS_VERSIONED_PTRAUTH_ABI(unsigned ST) {
return ST & CPU_SUBTYPE_ARM64E_VERSIONED_PTRAUTH_ABI_MASK;
}
inline unsigned CPU_SUBTYPE_ARM64E_IS_KERNEL_PTRAUTH_ABI(unsigned ST) {
return ST & CPU_SUBTYPE_ARM64E_KERNEL_PTRAUTH_ABI_MASK;
}
enum CPUSubTypeARM64_32 { CPU_SUBTYPE_ARM64_32_V8 = 1 };
enum CPUSubTypeSPARC { CPU_SUBTYPE_SPARC_ALL = 0 };
@@ -1668,6 +1699,8 @@ enum CPUSubTypePowerPC {
Expected<uint32_t> getCPUType(const Triple &T);
Expected<uint32_t> getCPUSubType(const Triple &T);
Expected<uint32_t> getCPUSubType(const Triple &T, unsigned PtrAuthABIVersion,
bool PtrAuthKernelABIVersion);
struct x86_thread_state32_t {
uint32_t eax;

18
llvm/lib/BinaryFormat/MachO.cpp
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@@ -105,3 +105,21 @@ Expected<uint32_t> MachO::getCPUSubType(const Triple &T) {
return getPowerPCSubType(T);
return unsupported("subtype", T);
}
Expected<uint32_t> MachO::getCPUSubType(const Triple &T,
unsigned PtrAuthABIVersion,
bool PtrAuthKernelABIVersion) {
Expected<uint32_t> Result = MachO::getCPUSubType(T);
if (!Result)
return Result.takeError();
if (*Result != MachO::CPU_SUBTYPE_ARM64E)
return createStringError(
std::errc::invalid_argument,
"ptrauth ABI version is only supported on arm64e.");
if (PtrAuthABIVersion > 0xF)
return createStringError(
std::errc::invalid_argument,
"The ptrauth ABI version needs to fit within 4 bits.");
return CPU_SUBTYPE_ARM64E_WITH_PTRAUTH_VERSION(PtrAuthABIVersion,
PtrAuthKernelABIVersion);
}

13
llvm/lib/MC/MachObjectWriter.cpp
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@@ -191,7 +191,18 @@ void MachObjectWriter::writeHeader(MachO::HeaderFileType Type,
W.write<uint32_t>(is64Bit() ? MachO::MH_MAGIC_64 : MachO::MH_MAGIC);
W.write<uint32_t>(TargetObjectWriter->getCPUType());
W.write<uint32_t>(TargetObjectWriter->getCPUSubtype());
uint32_t Cpusubtype = TargetObjectWriter->getCPUSubtype();
// Promote arm64e subtypes to always be ptrauth-ABI-versioned, at version 0.
// We never need to emit unversioned binaries.
// And we don't support arbitrary ABI versions (or the kernel flag) yet.
if (TargetObjectWriter->getCPUType() == MachO::CPU_TYPE_ARM64 &&
Cpusubtype == MachO::CPU_SUBTYPE_ARM64E)
Cpusubtype = MachO::CPU_SUBTYPE_ARM64E_WITH_PTRAUTH_VERSION(
/*PtrAuthABIVersion=*/0, /*PtrAuthKernelABIVersion=*/false);
W.write<uint32_t>(Cpusubtype);
W.write<uint32_t>(Type);
W.write<uint32_t>(NumLoadCommands);

2
llvm/lib/Object/MachOObjectFile.cpp
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@@ -134,7 +134,7 @@ static unsigned getCPUType(const MachOObjectFile &O) {
}
static unsigned getCPUSubType(const MachOObjectFile &O) {
return O.getHeader().cpusubtype;
return O.getHeader().cpusubtype & ~MachO::CPU_SUBTYPE_MASK;
}
static uint32_t

4
llvm/test/MC/AArch64/arm64e-subtype.s
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@@ -4,8 +4,8 @@
; CHECK: 0: c0 03 5f d6 ret
; CHECK: Mach header
; CHECK: magic cputype cpusubtype caps filetype ncmds sizeofcmds flags
; CHECK: MH_MAGIC_64 ARM64 E 0x00 OBJECT 3 256 0x00000000
; CHECK: magic cputype cpusubtype caps filetype ncmds sizeofcmds flags
; CHECK: MH_MAGIC_64 ARM64 E PAC00 OBJECT 3 256 0x00000000
.globl _foo
_foo:

BIN
llvm/test/tools/llvm-objdump/AArch64/Inputs/fat.macho-arm64e-kernel-ptrauth-abi Normal file
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Binary file not shown.

BIN
llvm/test/tools/llvm-objdump/AArch64/Inputs/fat.macho-arm64e-ptrauth-abi Normal file
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Binary file not shown.

13
llvm/test/tools/llvm-objdump/AArch64/macho-universal-arm64e-kernel-ptrauth-abi.test Normal file
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@@ -0,0 +1,13 @@
RUN: llvm-objdump %p/Inputs/fat.macho-arm64e-kernel-ptrauth-abi -m -p --universal-headers | FileCheck %s
CHECK: Fat headers
CHECK: fat_magic FAT_MAGIC
CHECK: nfat_arch 1
CHECK: architecture arm64e
CHECK: cputype CPU_TYPE_ARM64
CHECK: cpusubtype CPU_SUBTYPE_ARM64E
CHECK: capabilities CPU_SUBTYPE_ARM64E_KERNEL_PTRAUTH_VERSION 5
CHECK: Mach header
CHECK: magic cputype cpusubtype caps filetype ncmds sizeofcmds flags
CHECK: MH_MAGIC_64 ARM64 E PAK05 OBJECT 0 0 0x00000000

13
llvm/test/tools/llvm-objdump/AArch64/macho-universal-arm64e-ptrauth-abi.test Normal file
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@@ -0,0 +1,13 @@
RUN: llvm-objdump %p/Inputs/fat.macho-arm64e-ptrauth-abi -m -p --universal-headers | FileCheck %s
CHECK: Fat headers
CHECK: fat_magic FAT_MAGIC
CHECK: nfat_arch 1
CHECK: architecture arm64e
CHECK: cputype CPU_TYPE_ARM64
CHECK: cpusubtype CPU_SUBTYPE_ARM64E
CHECK: capabilities CPU_SUBTYPE_ARM64E_PTRAUTH_VERSION 5
CHECK: Mach header
CHECK: magic cputype cpusubtype caps filetype ncmds sizeofcmds flags
CHECK: MH_MAGIC_64 ARM64 E PAC05 OBJECT 0 0 0x00000000

23
llvm/test/tools/llvm-objdump/macho-ptrauth-cpusubtype.test Normal file
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@@ -0,0 +1,23 @@
#RUN: sed -e "s,SRC_CPUSUBTYPE,0x80000002,g" %s | yaml2obj -o -| llvm-objdump --macho -p - 2>&1 | FileCheck %s --check-prefix=CHECK --check-prefix=V0
#RUN: sed -e "s,SRC_CPUSUBTYPE,0x81000002,g" %s | yaml2obj -o -| llvm-objdump --macho -p - 2>&1 | FileCheck %s --check-prefix=CHECK --check-prefix=V1
#RUN: sed -e "s,SRC_CPUSUBTYPE,0xc1000002,g" %s | yaml2obj -o -| llvm-objdump --macho -p - 2>&1 | FileCheck %s --check-prefix=CHECK --check-prefix=V1K
#RUN: sed -e "s,SRC_CPUSUBTYPE,0x00000002,g" %s | yaml2obj -o -| llvm-objdump --macho -p - 2>&1 | FileCheck %s --check-prefix=CHECK --check-prefix=VNONE
# CHECK: Mach header
# CHECK: magic cputype cpusubtype caps filetype ncmds sizeofcmds flags
# V0: MH_MAGIC_64 ARM64 E PAC00 OBJECT 0 0 0x00000000
# V1: MH_MAGIC_64 ARM64 E PAC01 OBJECT 0 0 0x00000000
# V1K: MH_MAGIC_64 ARM64 E PAK01 OBJECT 0 0 0x00000000
# VNONE: MH_MAGIC_64 ARM64 E 0x00 OBJECT 0 0 0x00000000
--- !mach-o
FileHeader:
magic: 0xFEEDFACF
cputype: 0x0100000C
cpusubtype: SRC_CPUSUBTYPE
filetype: 0x00000001
ncmds: 0
sizeofcmds: 0
flags: 0x00000000
reserved: 0x00000000
...

3
llvm/tools/dsymutil/MachOUtils.cpp
View File

@@ -523,7 +523,8 @@ bool generateDsymCompanion(
SymtabStart = alignTo(SymtabStart, 0x1000);
// We gathered all the information we need, start emitting the output file.
Writer.writeHeader(MachO::MH_DSYM, NumLoadCommands, LoadCommandSize, false);
Writer.writeHeader(MachO::MH_DSYM, NumLoadCommands, LoadCommandSize,
/*SubsectionsViaSymbols=*/false);
// Write the load commands.
assert(OutFile.tell() == HeaderSize);

24
llvm/tools/llvm-objdump/MachODump.cpp
View File

@@ -2394,8 +2394,16 @@ static void printMachOUniversalHeaders(const object::MachOUniversalBinary *UB,
outs() << " cpusubtype " << (cpusubtype & ~MachO::CPU_SUBTYPE_MASK)
<< "\n";
}
if (verbose &&
(cpusubtype & MachO::CPU_SUBTYPE_MASK) == MachO::CPU_SUBTYPE_LIB64)
if (verbose && cputype == MachO::CPU_TYPE_ARM64 &&
MachO::CPU_SUBTYPE_ARM64E_IS_VERSIONED_PTRAUTH_ABI(cpusubtype)) {
outs() << " capabilities CPU_SUBTYPE_ARM64E_";
if (MachO::CPU_SUBTYPE_ARM64E_IS_KERNEL_PTRAUTH_ABI(cpusubtype))
outs() << "KERNEL_";
outs() << format("PTRAUTH_VERSION %d",
MachO::CPU_SUBTYPE_ARM64E_PTRAUTH_VERSION(cpusubtype))
<< "\n";
} else if (verbose && (cpusubtype & MachO::CPU_SUBTYPE_MASK) ==
MachO::CPU_SUBTYPE_LIB64)
outs() << " capabilities CPU_SUBTYPE_LIB64\n";
else
outs() << " capabilities "
@@ -8368,7 +8376,17 @@ static void PrintMachHeader(uint32_t magic, uint32_t cputype,
outs() << format(" %10d", cpusubtype & ~MachO::CPU_SUBTYPE_MASK);
break;
}
if ((cpusubtype & MachO::CPU_SUBTYPE_MASK) == MachO::CPU_SUBTYPE_LIB64) {
if (cputype == MachO::CPU_TYPE_ARM64 &&
MachO::CPU_SUBTYPE_ARM64E_IS_VERSIONED_PTRAUTH_ABI(cpusubtype)) {
const char *Format =
MachO::CPU_SUBTYPE_ARM64E_IS_KERNEL_PTRAUTH_ABI(cpusubtype)
? " PAK%02d"
: " PAC%02d";
outs() << format(Format,
MachO::CPU_SUBTYPE_ARM64E_PTRAUTH_VERSION(cpusubtype));
} else if ((cpusubtype & MachO::CPU_SUBTYPE_MASK) ==
MachO::CPU_SUBTYPE_LIB64) {
outs() << " LIB64";
} else {
outs() << format(" 0x%02" PRIx32,

53
llvm/unittests/BinaryFormat/MachOTest.cpp
View File

@@ -125,3 +125,56 @@ TEST(MachOTest, CPUSubType) {
}
#undef CHECK_CPUSUBTYPE
}
TEST(MachOTest, CPUSubTypePtrAuthABI) {
{
Expected<uint32_t> Type = MachO::getCPUSubType(
Triple("x86_64-apple-darwin"), /*PtrAuthABIVersion=*/5,
/*PtrAuthKernelABIVersion=*/false);
ASSERT_EQ(toString(Type.takeError()),
"ptrauth ABI version is only supported on arm64e.");
}
{
Expected<uint32_t> Type = MachO::getCPUSubType(
Triple("arm64e-apple-darwin"), /*PtrAuthABIVersion=*/0x10,
/*PtrAuthKernelABIVersion=*/false);
ASSERT_EQ(toString(Type.takeError()),
"The ptrauth ABI version needs to fit within 4 bits.");
}
{
uint32_t Type = cantFail(MachO::getCPUSubType(
Triple("arm64e-apple-darwin"),
/*PtrAuthABIVersion=*/5, /*PtrAuthKernelABIVersion=*/false));
ASSERT_EQ(Type, 0x85000002U);
}
{
uint32_t Type = cantFail(MachO::getCPUSubType(
Triple("arm64e-apple-darwin"),
/*PtrAuthABIVersion=*/5, /*PtrAuthKernelABIVersion=*/true));
ASSERT_EQ(Type, 0xC5000002U);
}
{
uint32_t Type = cantFail(MachO::getCPUSubType(
Triple("arm64e-apple-darwin"),
/*PtrAuthABIVersion=*/0xF, /*PtrAuthKernelABIVersion=*/false));
ASSERT_EQ(Type, 0x8F000002U);
}
{
uint32_t Type = cantFail(MachO::getCPUSubType(
Triple("arm64e-apple-darwin"),
/*PtrAuthABIVersion=*/0xF, /*PtrAuthKernelABIVersion=*/true));
ASSERT_EQ(Type, 0xCF000002U);
}
{
uint32_t Type = cantFail(MachO::getCPUSubType(
Triple("arm64e-apple-darwin"),
/*PtrAuthABIVersion=*/0, /*PtrAuthKernelABIVersion=*/false));
ASSERT_EQ(Type, 0x80000002U);
}
{
uint32_t Type = cantFail(MachO::getCPUSubType(
Triple("arm64e-apple-darwin"),
/*PtrAuthABIVersion=*/0, /*PtrAuthKernelABIVersion=*/true));
ASSERT_EQ(Type, 0xC0000002U);
}
}