1//===- ARM64.cpp ----------------------------------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#include "Arch/ARM64Common.h"
10#include "InputFiles.h"
11#include "Symbols.h"
12#include "SyntheticSections.h"
13#include "Target.h"
14
15#include "lld/Common/ErrorHandler.h"
16#include "mach-o/compact_unwind_encoding.h"
17#include "llvm/BinaryFormat/MachO.h"
18
19using namespace llvm;
20using namespace llvm::MachO;
21using namespace lld;
22using namespace lld::macho;
23
24namespace {
25
26struct ARM64 : ARM64Common {
27 ARM64();
28 void writeStub(uint8_t *buf, const Symbol &, uint64_t) const override;
29 void writeStubHelperHeader(uint8_t *buf) const override;
30 void writeStubHelperEntry(uint8_t *buf, const Symbol &,
31 uint64_t entryAddr) const override;
32
33 void writeObjCMsgSendStub(uint8_t *buf, Symbol *sym, uint64_t stubsAddr,
34 uint64_t &stubOffset, uint64_t selrefVA,
35 Symbol *objcMsgSend) const override;
36 void populateThunk(InputSection *thunk, Symbol *funcSym) override;
37
38 void initICFSafeThunkBody(InputSection *thunk,
39 Symbol *targetSym) const override;
40 Symbol *getThunkBranchTarget(InputSection *thunk) const override;
41 uint32_t getICFSafeThunkSize() const override;
42};
43
44} // namespace
45
46// Random notes on reloc types:
47// ADDEND always pairs with BRANCH26, PAGE21, or PAGEOFF12
48// POINTER_TO_GOT: ld64 supports a 4-byte pc-relative form as well as an 8-byte
49// absolute version of this relocation. The semantics of the absolute relocation
50// are weird -- it results in the value of the GOT slot being written, instead
51// of the address. Let's not support it unless we find a real-world use case.
52static constexpr std::array<RelocAttrs, 11> relocAttrsArray{._M_elems: {
53#define B(x) RelocAttrBits::x
54 {.name: "UNSIGNED",
55 B(UNSIGNED) | B(ABSOLUTE) | B(EXTERN) | B(LOCAL) | B(BYTE4) | B(BYTE8)},
56 {.name: "SUBTRACTOR", B(SUBTRAHEND) | B(EXTERN) | B(BYTE4) | B(BYTE8)},
57 {.name: "BRANCH26", B(PCREL) | B(EXTERN) | B(BRANCH) | B(BYTE4)},
58 {.name: "PAGE21", B(PCREL) | B(EXTERN) | B(BYTE4)},
59 {.name: "PAGEOFF12", B(ABSOLUTE) | B(EXTERN) | B(BYTE4)},
60 {.name: "GOT_LOAD_PAGE21", B(PCREL) | B(EXTERN) | B(GOT) | B(BYTE4)},
61 {.name: "GOT_LOAD_PAGEOFF12",
62 B(ABSOLUTE) | B(EXTERN) | B(GOT) | B(LOAD) | B(BYTE4)},
63 {.name: "POINTER_TO_GOT", B(PCREL) | B(EXTERN) | B(GOT) | B(POINTER) | B(BYTE4)},
64 {.name: "TLVP_LOAD_PAGE21", B(PCREL) | B(EXTERN) | B(TLV) | B(BYTE4)},
65 {.name: "TLVP_LOAD_PAGEOFF12",
66 B(ABSOLUTE) | B(EXTERN) | B(TLV) | B(LOAD) | B(BYTE4)},
67 {.name: "ADDEND", B(ADDEND)},
68#undef B
69}};
70
71static constexpr uint32_t stubCode[] = {
72 0x90000010, // 00: adrp x16, __la_symbol_ptr@page
73 0xf9400210, // 04: ldr x16, [x16, __la_symbol_ptr@pageoff]
74 0xd61f0200, // 08: br x16
75};
76
77void ARM64::writeStub(uint8_t *buf8, const Symbol &sym,
78 uint64_t pointerVA) const {
79 ::writeStub(buf8, stubCode, sym, pointerVA);
80}
81
82static constexpr uint32_t stubHelperHeaderCode[] = {
83 0x90000011, // 00: adrp x17, _dyld_private@page
84 0x91000231, // 04: add x17, x17, _dyld_private@pageoff
85 0xa9bf47f0, // 08: stp x16/x17, [sp, #-16]!
86 0x90000010, // 0c: adrp x16, dyld_stub_binder@page
87 0xf9400210, // 10: ldr x16, [x16, dyld_stub_binder@pageoff]
88 0xd61f0200, // 14: br x16
89};
90
91void ARM64::writeStubHelperHeader(uint8_t *buf8) const {
92 ::writeStubHelperHeader<LP64>(buf8, stubHelperHeaderCode);
93}
94
95static constexpr uint32_t stubHelperEntryCode[] = {
96 0x18000050, // 00: ldr w16, l0
97 0x14000000, // 04: b stubHelperHeader
98 0x00000000, // 08: l0: .long 0
99};
100
101void ARM64::writeStubHelperEntry(uint8_t *buf8, const Symbol &sym,
102 uint64_t entryVA) const {
103 ::writeStubHelperEntry(buf8, stubHelperEntryCode, sym, entryVA);
104}
105
106static constexpr uint32_t objcStubsFastCode[] = {
107 0x90000001, // adrp x1, __objc_selrefs@page
108 0xf9400021, // ldr x1, [x1, @selector("foo")@pageoff]
109 0x90000010, // adrp x16, _got@page
110 0xf9400210, // ldr x16, [x16, _objc_msgSend@pageoff]
111 0xd61f0200, // br x16
112 0xd4200020, // brk #0x1
113 0xd4200020, // brk #0x1
114 0xd4200020, // brk #0x1
115};
116
117static constexpr uint32_t objcStubsSmallCode[] = {
118 0x90000001, // adrp x1, __objc_selrefs@page
119 0xf9400021, // ldr x1, [x1, @selector("foo")@pageoff]
120 0x14000000, // b _objc_msgSend
121};
122
123void ARM64::writeObjCMsgSendStub(uint8_t *buf, Symbol *sym, uint64_t stubsAddr,
124 uint64_t &stubOffset, uint64_t selrefVA,
125 Symbol *objcMsgSend) const {
126 uint64_t objcMsgSendAddr;
127 uint64_t objcStubSize;
128 uint64_t objcMsgSendIndex;
129
130 if (config->objcStubsMode == ObjCStubsMode::fast) {
131 objcStubSize = target->objcStubsFastSize;
132 objcMsgSendAddr = in.got->addr;
133 objcMsgSendIndex = objcMsgSend->gotIndex;
134 ::writeObjCMsgSendFastStub<LP64>(buf, objcStubsFastCode, sym, stubsAddr,
135 stubOffset, selrefVA, gotAddr: objcMsgSendAddr,
136 msgSendIndex: objcMsgSendIndex);
137 } else {
138 assert(config->objcStubsMode == ObjCStubsMode::small);
139 objcStubSize = target->objcStubsSmallSize;
140 if (auto *d = dyn_cast<Defined>(Val: objcMsgSend)) {
141 objcMsgSendAddr = d->getVA();
142 objcMsgSendIndex = 0;
143 } else {
144 objcMsgSendAddr = in.stubs->addr;
145 objcMsgSendIndex = objcMsgSend->stubsIndex;
146 }
147 ::writeObjCMsgSendSmallStub<LP64>(buf, objcStubsSmallCode, sym, stubsAddr,
148 stubOffset, selrefVA, msgSendAddr: objcMsgSendAddr,
149 msgSendIndex: objcMsgSendIndex);
150 }
151 stubOffset += objcStubSize;
152}
153
154// A thunk is the relaxed variation of stubCode. We don't need the
155// extra indirection through a lazy pointer because the target address
156// is known at link time.
157static constexpr uint32_t thunkCode[] = {
158 0x90000010, // 00: adrp x16, <thunk.ptr>@page
159 0x91000210, // 04: add x16, [x16,<thunk.ptr>@pageoff]
160 0xd61f0200, // 08: br x16
161};
162
163void ARM64::populateThunk(InputSection *thunk, Symbol *funcSym) {
164 thunk->align = 4;
165 thunk->data = {reinterpret_cast<const uint8_t *>(thunkCode),
166 sizeof(thunkCode)};
167 thunk->relocs.emplace_back(/*type=*/args: ARM64_RELOC_PAGEOFF12,
168 /*pcrel=*/args: false, /*length=*/args: 2,
169 /*offset=*/args: 4, /*addend=*/args: 0,
170 /*referent=*/args&: funcSym);
171 thunk->relocs.emplace_back(/*type=*/args: ARM64_RELOC_PAGE21,
172 /*pcrel=*/args: true, /*length=*/args: 2,
173 /*offset=*/args: 0, /*addend=*/args: 0,
174 /*referent=*/args&: funcSym);
175}
176// Just a single direct branch to the target function.
177static constexpr uint32_t icfSafeThunkCode[] = {
178 0x14000000, // 08: b target
179};
180
181void ARM64::initICFSafeThunkBody(InputSection *thunk, Symbol *targetSym) const {
182 // The base data here will not be itself modified, we'll just be adding a
183 // reloc below. So we can directly use the constexpr above as the data.
184 thunk->data = {reinterpret_cast<const uint8_t *>(icfSafeThunkCode),
185 sizeof(icfSafeThunkCode)};
186
187 thunk->relocs.emplace_back(/*type=*/args: ARM64_RELOC_BRANCH26,
188 /*pcrel=*/args: true, /*length=*/args: 2,
189 /*offset=*/args: 0, /*addend=*/args: 0,
190 /*referent=*/args&: targetSym);
191}
192
193Symbol *ARM64::getThunkBranchTarget(InputSection *thunk) const {
194 assert(thunk->relocs.size() == 1 &&
195 "expected a single reloc on ARM64 ICF thunk");
196 auto &reloc = thunk->relocs[0];
197 assert(isa<Symbol *>(reloc.referent) &&
198 "ARM64 thunk reloc is expected to point to a Symbol");
199
200 return cast<Symbol *>(Val&: reloc.referent);
201}
202
203uint32_t ARM64::getICFSafeThunkSize() const { return sizeof(icfSafeThunkCode); }
204
205ARM64::ARM64() : ARM64Common(LP64()) {
206 cpuType = CPU_TYPE_ARM64;
207 cpuSubtype = CPU_SUBTYPE_ARM64_ALL;
208
209 stubSize = sizeof(stubCode);
210 thunkSize = sizeof(thunkCode);
211
212 objcStubsFastSize = sizeof(objcStubsFastCode);
213 objcStubsFastAlignment = 32;
214 objcStubsSmallSize = sizeof(objcStubsSmallCode);
215 objcStubsSmallAlignment = 4;
216
217 // Branch immediate is two's complement 26 bits, which is implicitly
218 // multiplied by 4 (since all functions are 4-aligned: The branch range
219 // is -4*(2**(26-1))..4*(2**(26-1) - 1).
220 backwardBranchRange = 128 * 1024 * 1024;
221 forwardBranchRange = backwardBranchRange - 4;
222
223 modeDwarfEncoding = UNWIND_ARM64_MODE_DWARF;
224 subtractorRelocType = ARM64_RELOC_SUBTRACTOR;
225 unsignedRelocType = ARM64_RELOC_UNSIGNED;
226
227 stubHelperHeaderSize = sizeof(stubHelperHeaderCode);
228 stubHelperEntrySize = sizeof(stubHelperEntryCode);
229
230 relocAttrs = {relocAttrsArray.data(), relocAttrsArray.size()};
231}
232
233TargetInfo *macho::createARM64TargetInfo() {
234 static ARM64 t;
235 return &t;
236}
237