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[llvm-objdump][macho] Add support for ObjC relative method lists #85477

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Mar 16, 2024
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[llvm-objdump][macho] Add support for ObjC relative method lists #85477

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Binary file added llvm/test/tools/llvm-objdump/MachO/AArch64/Inputs/rel-method-lists-arm64.dylib
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Binary file added llvm/test/tools/llvm-objdump/MachO/AArch64/Inputs/rel-method-lists-arm64_32.dylib
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86 changes: 86 additions & 0 deletions llvm/test/tools/llvm-objdump/MachO/AArch64/macho-relative-method-lists.test
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Original file line number Diff line number Diff line change
@@ -0,0 +1,86 @@
RUN: llvm-objdump --macho --objc-meta-data %p/Inputs/rel-method-lists-arm64_32.dylib | FileCheck %s --check-prefix=CHK32
RUN: llvm-otool -ov %p/Inputs/rel-method-lists-arm64_32.dylib | FileCheck %s --check-prefix=CHK32

RUN: llvm-objdump --macho --objc-meta-data %p/Inputs/rel-method-lists-arm64.dylib | FileCheck %s --check-prefix=CHK64
RUN: llvm-otool -ov %p/Inputs/rel-method-lists-arm64.dylib | FileCheck %s --check-prefix=CHK64

CHK32: baseMethods 0x660 (struct method_list_t *)
CHK32-NEXT: entsize 12 (relative)
CHK32-NEXT: count 3
CHK32-NEXT: name 0x144 (0x{{[0-9a-f]*}}) instance_method_00
CHK32-NEXT: types 0x91 (0x{{[0-9a-f]*}}) v8@0:4
CHK32-NEXT: imp 0xffffff18 (0x{{[0-9a-f]*}}) -[MyClass instance_method_00]
CHK32-NEXT: name 0x13c (0x{{[0-9a-f]*}}) instance_method_01
CHK32-NEXT: types 0x85 (0x{{[0-9a-f]*}}) v8@0:4
CHK32-NEXT: imp 0xffffff28 (0x{{[0-9a-f]*}}) -[MyClass instance_method_01]
CHK32-NEXT: name 0x134 (0x{{[0-9a-f]*}}) instance_method_02
CHK32-NEXT: types 0x79 (0x{{[0-9a-f]*}}) v8@0:4
CHK32-NEXT: imp 0xffffff38 (0x{{[0-9a-f]*}}) -[MyClass instance_method_02]

CHK32: baseMethods 0x630 (struct method_list_t *)
CHK32-NEXT: entsize 12 (relative)
CHK32-NEXT: count 3
CHK32-NEXT: name 0x180 (0x{{[0-9a-f]*}}) class_method_00
CHK32-NEXT: types 0xc1 (0x{{[0-9a-f]*}}) v8@0:4
CHK32-NEXT: imp 0xffffff9c (0x{{[0-9a-f]*}}) +[MyClass class_method_00]
CHK32-NEXT: name 0x178 (0x{{[0-9a-f]*}}) class_method_01
CHK32-NEXT: types 0xb5 (0x{{[0-9a-f]*}}) v8@0:4
CHK32-NEXT: imp 0xffffffac (0x{{[0-9a-f]*}}) +[MyClass class_method_01]
CHK32-NEXT: name 0x170 (0x{{[0-9a-f]*}}) class_method_02
CHK32-NEXT: types 0xa9 (0x{{[0-9a-f]*}}) v8@0:4
CHK32-NEXT: imp 0xffffffbc (0x{{[0-9a-f]*}}) +[MyClass class_method_02]

CHK64: baseMethods 0x6e0 (struct method_list_t *)
CHK64-NEXT: entsize 12 (relative)
CHK64-NEXT: count 3
CHK64-NEXT: name 0x188 (0x{{[0-9a-f]*}}) instance_method_00
CHK64-NEXT: types 0x91 (0x{{[0-9a-f]*}}) v16@0:8
CHK64-NEXT: imp 0xffffffa8 (0x{{[0-9a-f]*}}) -[MyClass instance_method_00]
CHK64-NEXT: name 0x184 (0x{{[0-9a-f]*}}) instance_method_01
CHK64-NEXT: types 0x85 (0x{{[0-9a-f]*}}) v16@0:8
CHK64-NEXT: imp 0xffffffa0 (0x{{[0-9a-f]*}}) -[MyClass instance_method_01]
CHK64-NEXT: name 0x180 (0x{{[0-9a-f]*}}) instance_method_02
CHK64-NEXT: types 0x79 (0x{{[0-9a-f]*}}) v16@0:8
CHK64-NEXT: imp 0xffffff98 (0x{{[0-9a-f]*}}) -[MyClass instance_method_02]

CHK64: baseMethods 0x6b0 (struct method_list_t *)
CHK64-NEXT: entsize 12 (relative)
CHK64-NEXT: count 3
CHK64-NEXT: name 0x1d0 (0x{{[0-9a-f]*}}) class_method_00
CHK64-NEXT: types 0xc1 (0x{{[0-9a-f]*}}) v16@0:8
CHK64-NEXT: imp 0xffffffe4 (0x{{[0-9a-f]*}}) +[MyClass class_method_00]
CHK64-NEXT: name 0x1cc (0x{{[0-9a-f]*}}) class_method_01
CHK64-NEXT: types 0xb5 (0x{{[0-9a-f]*}}) v16@0:8
CHK64-NEXT: imp 0xffffffdc (0x{{[0-9a-f]*}}) +[MyClass class_method_01]
CHK64-NEXT: name 0x1c8 (0x{{[0-9a-f]*}}) class_method_02
CHK64-NEXT: types 0xa9 (0x{{[0-9a-f]*}}) v16@0:8
CHK64-NEXT: imp 0xffffffd4 (0x{{[0-9a-f]*}}) +[MyClass class_method_02]

######## Generate rel-method-lists-arm64.dylib ########
// clang -c main.mm -o main.o -target arm64-apple-macos -arch arm64
// ld64.ld64 -dylib -demangle -dynamic main.o -o rel-method-lists-arm64.dylib -syslibroot MacOSX14.2.sdk -segalign 0x10 -objc_relative_method_lists

######## Generate rel-method-lists-arm64_32.dylib ########
// clang -c main.mm -o main.o -target arm64_32-apple-watchos -arch arm64_32
// ld64.ld64 -dylib -demangle -dynamic main.o -o rel-method-lists-arm64_32.dylib -syslibroot WatchOS.sdk -segalign 0x10 -objc_relative_method_lists

// ~~~~~~~~~~~~~~~~~~~~~~~~~ main.mm ~~~~~~~~~~~~~~~~~~~~~~~~~
__attribute__((objc_root_class))
@interface MyClass
- (void)instance_method_00;
- (void)instance_method_01;
- (void)instance_method_02;
+ (void)class_method_00;
+ (void)class_method_01;
+ (void)class_method_02;
@end
@implementation MyClass
- (void)instance_method_00 {}
- (void)instance_method_01 {}
- (void)instance_method_02 {}
+ (void)class_method_00 {}
+ (void)class_method_01 {}
+ (void)class_method_02 {}
@end
void *_objc_empty_cache;
void *_objc_empty_vtable;
112 changes: 110 additions & 2 deletions llvm/tools/llvm-objdump/MachODump.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3661,6 +3661,10 @@ struct class_ro32_t {
#define RO_ROOT (1 << 1)
#define RO_HAS_CXX_STRUCTORS (1 << 2)

/* Values for method_list{64,32}_t->entsize */
#define ML_HAS_RELATIVE_PTRS (1 << 31)
#define ML_ENTSIZE_MASK 0xFFFF

struct method_list64_t {
uint32_t entsize;
uint32_t count;
Expand All @@ -3685,6 +3689,12 @@ struct method32_t {
uint32_t imp; /* IMP (32-bit pointer) */
};

struct method_relative_t {
int32_t name; /* SEL (32-bit relative) */
int32_t types; /* const char * (32-bit relative) */
int32_t imp; /* IMP (32-bit relative) */
};

struct protocol_list64_t {
uint64_t count; /* uintptr_t (a 64-bit value) */
/* struct protocol64_t * list[0]; These pointers follow inline */
Expand Down Expand Up @@ -3986,6 +3996,12 @@ inline void swapStruct(struct method32_t &m) {
sys::swapByteOrder(m.imp);
}

inline void swapStruct(struct method_relative_t &m) {
sys::swapByteOrder(m.name);
sys::swapByteOrder(m.types);
sys::swapByteOrder(m.imp);
}

inline void swapStruct(struct protocol_list64_t &pl) {
sys::swapByteOrder(pl.count);
}
Expand Down Expand Up @@ -4440,6 +4456,84 @@ static void print_layout_map32(uint32_t p, struct DisassembleInfo *info) {
print_layout_map(layout_map, left);
}

static void print_relative_method_list(uint32_t structSizeAndFlags,
uint32_t structCount, uint64_t p,
struct DisassembleInfo *info,
const char *indent,
uint32_t pointerBits) {
struct method_relative_t m;
const char *r, *name;
uint32_t offset, xoffset, left, i;
SectionRef S, xS;

assert(((structSizeAndFlags & ML_HAS_RELATIVE_PTRS) != 0) &&
"expected structSizeAndFlags to have ML_HAS_RELATIVE_PTRS flag");

outs() << indent << "\t\t entsize "
<< (structSizeAndFlags & ML_ENTSIZE_MASK) << " (relative) \n";
outs() << indent << "\t\t count " << structCount << "\n";

for (i = 0; i < structCount; i++) {
r = get_pointer_64(p, offset, left, S, info);
memset(&m, '\0', sizeof(struct method_relative_t));
if (left < sizeof(struct method_relative_t)) {
memcpy(&m, r, left);
outs() << indent << " (method_t extends past the end of the section)\n";
} else
memcpy(&m, r, sizeof(struct method_relative_t));
if (info->O->isLittleEndian() != sys::IsLittleEndianHost)
swapStruct(m);

outs() << indent << "\t\t name " << format("0x%" PRIx32, m.name);
uint64_t relNameRefVA = p + offsetof(struct method_relative_t, name);
uint64_t absNameRefVA = relNameRefVA + m.name;
outs() << " (" << format("0x%" PRIx32, absNameRefVA) << ")";

// since this is a relative list, absNameRefVA is the address of the
// __objc_selrefs entry, so a pointer, not the actual name
const char *nameRefPtr =
get_pointer_64(absNameRefVA, xoffset, left, xS, info);
if (nameRefPtr) {
uint32_t pointerSize = pointerBits / CHAR_BIT;
if (left < pointerSize)
outs() << indent << " (nameRefPtr extends past the end of the section)";
else {
if (pointerSize == 64) {
name = get_pointer_64(*reinterpret_cast<const uint64_t *>(nameRefPtr),
xoffset, left, xS, info);
} else {
name = get_pointer_32(*reinterpret_cast<const uint32_t *>(nameRefPtr),
xoffset, left, xS, info);
}
if (name != nullptr)
outs() << format(" %.*s", left, name);
}
}
outs() << "\n";

outs() << indent << "\t\t types " << format("0x%" PRIx32, m.types);
uint64_t relTypesVA = p + offsetof(struct method_relative_t, types);
uint64_t absTypesVA = relTypesVA + m.types;
outs() << " (" << format("0x%" PRIx32, absTypesVA) << ")";
name = get_pointer_32(absTypesVA, xoffset, left, xS, info);
if (name != nullptr)
outs() << format(" %.*s", left, name);
outs() << "\n";

outs() << indent << "\t\t imp " << format("0x%" PRIx32, m.imp);
uint64_t relImpVA = p + offsetof(struct method_relative_t, imp);
uint64_t absImpVA = relImpVA + m.imp;
outs() << " (" << format("0x%" PRIx32, absImpVA) << ")";
name = GuessSymbolName(absImpVA, info->AddrMap);
if (name != nullptr)
outs() << " " << name;
outs() << "\n";

p += sizeof(struct method_relative_t);
offset += sizeof(struct method_relative_t);
}
}

static void print_method_list64_t(uint64_t p, struct DisassembleInfo *info,
const char *indent) {
struct method_list64_t ml;
Expand All @@ -4461,10 +4555,17 @@ static void print_method_list64_t(uint64_t p, struct DisassembleInfo *info,
memcpy(&ml, r, sizeof(struct method_list64_t));
if (info->O->isLittleEndian() != sys::IsLittleEndianHost)
swapStruct(ml);
p += sizeof(struct method_list64_t);

if ((ml.entsize & ML_HAS_RELATIVE_PTRS) != 0) {
print_relative_method_list(ml.entsize, ml.count, p, info, indent,
/*pointerBits=*/64);
return;
}

outs() << indent << "\t\t entsize " << ml.entsize << "\n";
outs() << indent << "\t\t count " << ml.count << "\n";

p += sizeof(struct method_list64_t);
offset += sizeof(struct method_list64_t);
for (i = 0; i < ml.count; i++) {
r = get_pointer_64(p, offset, left, S, info);
Expand Down Expand Up @@ -4552,10 +4653,17 @@ static void print_method_list32_t(uint64_t p, struct DisassembleInfo *info,
memcpy(&ml, r, sizeof(struct method_list32_t));
if (info->O->isLittleEndian() != sys::IsLittleEndianHost)
swapStruct(ml);
p += sizeof(struct method_list32_t);

if ((ml.entsize & ML_HAS_RELATIVE_PTRS) != 0) {
print_relative_method_list(ml.entsize, ml.count, p, info, indent,
/*pointerBits=*/32);
return;
}

outs() << indent << "\t\t entsize " << ml.entsize << "\n";
outs() << indent << "\t\t count " << ml.count << "\n";

p += sizeof(struct method_list32_t);
offset += sizeof(struct method_list32_t);
for (i = 0; i < ml.count; i++) {
r = get_pointer_32(p, offset, left, S, info);
Expand Down