Bug Summary

File:build/llvm-toolchain-snapshot-16~++20221003111214+1fa2019828ca/lldb/source/Plugins/UnwindAssembly/x86/x86AssemblyInspectionEngine.cpp
Warning:line 1000, column 7
Value stored to 'fa_value_ptr' is never read

Annotated Source Code

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clang -cc1 -cc1 -triple x86_64-pc-linux-gnu -analyze -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name x86AssemblyInspectionEngine.cpp -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=cplusplus -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -setup-static-analyzer -analyzer-config-compatibility-mode=true -mrelocation-model pic -pic-level 2 -mframe-pointer=none -fmath-errno -ffp-contract=on -fno-rounding-math -mconstructor-aliases -funwind-tables=2 -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb -ffunction-sections -fdata-sections -fcoverage-compilation-dir=/build/llvm-toolchain-snapshot-16~++20221003111214+1fa2019828ca/build-llvm/tools/clang/stage2-bins -resource-dir /usr/lib/llvm-16/lib/clang/16.0.0 -isystem /usr/include/libxml2 -D HAVE_ROUND -D _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I tools/lldb/source/Plugins/UnwindAssembly/x86 -I /build/llvm-toolchain-snapshot-16~++20221003111214+1fa2019828ca/lldb/source/Plugins/UnwindAssembly/x86 -I /build/llvm-toolchain-snapshot-16~++20221003111214+1fa2019828ca/lldb/include -I tools/lldb/include -I include -I /build/llvm-toolchain-snapshot-16~++20221003111214+1fa2019828ca/llvm/include -I /usr/include/python3.9 -I /build/llvm-toolchain-snapshot-16~++20221003111214+1fa2019828ca/clang/include -I tools/lldb/../clang/include -I /build/llvm-toolchain-snapshot-16~++20221003111214+1fa2019828ca/lldb/source -I tools/lldb/source -D _FORTIFY_SOURCE=2 -D NDEBUG -U NDEBUG -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/x86_64-linux-gnu/c++/10 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/backward -internal-isystem /usr/lib/llvm-16/lib/clang/16.0.0/include -internal-isystem /usr/local/include -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../x86_64-linux-gnu/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -fmacro-prefix-map=/build/llvm-toolchain-snapshot-16~++20221003111214+1fa2019828ca/build-llvm/tools/clang/stage2-bins=build-llvm/tools/clang/stage2-bins -fmacro-prefix-map=/build/llvm-toolchain-snapshot-16~++20221003111214+1fa2019828ca/= -fcoverage-prefix-map=/build/llvm-toolchain-snapshot-16~++20221003111214+1fa2019828ca/build-llvm/tools/clang/stage2-bins=build-llvm/tools/clang/stage2-bins -fcoverage-prefix-map=/build/llvm-toolchain-snapshot-16~++20221003111214+1fa2019828ca/= -O2 -Wno-unused-command-line-argument -Wno-unused-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-maybe-uninitialized -Wno-class-memaccess -Wno-redundant-move -Wno-pessimizing-move -Wno-noexcept-type -Wno-comment -Wno-misleading-indentation -Wno-deprecated-declarations -Wno-unknown-pragmas -Wno-strict-aliasing -Wno-stringop-truncation -std=c++17 -fdeprecated-macro -fdebug-compilation-dir=/build/llvm-toolchain-snapshot-16~++20221003111214+1fa2019828ca/build-llvm/tools/clang/stage2-bins -fdebug-prefix-map=/build/llvm-toolchain-snapshot-16~++20221003111214+1fa2019828ca/build-llvm/tools/clang/stage2-bins=build-llvm/tools/clang/stage2-bins -fdebug-prefix-map=/build/llvm-toolchain-snapshot-16~++20221003111214+1fa2019828ca/= -ferror-limit 19 -fvisibility-inlines-hidden -stack-protector 2 -fgnuc-version=4.2.1 -fcolor-diagnostics -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /tmp/scan-build-2022-10-03-140002-15933-1 -x c++ /build/llvm-toolchain-snapshot-16~++20221003111214+1fa2019828ca/lldb/source/Plugins/UnwindAssembly/x86/x86AssemblyInspectionEngine.cpp
1//===-- x86AssemblyInspectionEngine.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 "x86AssemblyInspectionEngine.h"
10
11#include <memory>
12
13#include "llvm-c/Disassembler.h"
14
15#include "lldb/Core/Address.h"
16#include "lldb/Symbol/UnwindPlan.h"
17#include "lldb/Target/RegisterContext.h"
18#include "lldb/Target/UnwindAssembly.h"
19
20using namespace lldb_private;
21using namespace lldb;
22
23x86AssemblyInspectionEngine::x86AssemblyInspectionEngine(const ArchSpec &arch)
24 : m_cur_insn(nullptr), m_machine_ip_regnum(LLDB_INVALID_REGNUM(4294967295U)),
25 m_machine_sp_regnum(LLDB_INVALID_REGNUM(4294967295U)),
26 m_machine_fp_regnum(LLDB_INVALID_REGNUM(4294967295U)),
27 m_machine_alt_fp_regnum(LLDB_INVALID_REGNUM(4294967295U)),
28 m_lldb_ip_regnum(LLDB_INVALID_REGNUM(4294967295U)),
29 m_lldb_sp_regnum(LLDB_INVALID_REGNUM(4294967295U)),
30 m_lldb_fp_regnum(LLDB_INVALID_REGNUM(4294967295U)),
31 m_lldb_alt_fp_regnum(LLDB_INVALID_REGNUM(4294967295U)), m_reg_map(), m_arch(arch),
32 m_cpu(k_cpu_unspecified), m_wordsize(-1),
33 m_register_map_initialized(false), m_disasm_context() {
34 m_disasm_context =
35 ::LLVMCreateDisasm(arch.GetTriple().getTriple().c_str(), nullptr,
36 /*TagType=*/1, nullptr, nullptr);
37}
38
39x86AssemblyInspectionEngine::~x86AssemblyInspectionEngine() {
40 ::LLVMDisasmDispose(m_disasm_context);
41}
42
43void x86AssemblyInspectionEngine::Initialize(RegisterContextSP &reg_ctx) {
44 m_cpu = k_cpu_unspecified;
45 m_wordsize = -1;
46 m_register_map_initialized = false;
47
48 const llvm::Triple::ArchType cpu = m_arch.GetMachine();
49 if (cpu == llvm::Triple::x86)
50 m_cpu = k_i386;
51 else if (cpu == llvm::Triple::x86_64)
52 m_cpu = k_x86_64;
53
54 if (m_cpu == k_cpu_unspecified)
55 return;
56
57 if (reg_ctx.get() == nullptr)
58 return;
59
60 if (m_cpu == k_i386) {
61 m_machine_ip_regnum = k_machine_eip;
62 m_machine_sp_regnum = k_machine_esp;
63 m_machine_fp_regnum = k_machine_ebp;
64 m_machine_alt_fp_regnum = k_machine_ebx;
65 m_wordsize = 4;
66
67 struct lldb_reg_info reginfo;
68 reginfo.name = "eax";
69 m_reg_map[k_machine_eax] = reginfo;
70 reginfo.name = "edx";
71 m_reg_map[k_machine_edx] = reginfo;
72 reginfo.name = "esp";
73 m_reg_map[k_machine_esp] = reginfo;
74 reginfo.name = "esi";
75 m_reg_map[k_machine_esi] = reginfo;
76 reginfo.name = "eip";
77 m_reg_map[k_machine_eip] = reginfo;
78 reginfo.name = "ecx";
79 m_reg_map[k_machine_ecx] = reginfo;
80 reginfo.name = "ebx";
81 m_reg_map[k_machine_ebx] = reginfo;
82 reginfo.name = "ebp";
83 m_reg_map[k_machine_ebp] = reginfo;
84 reginfo.name = "edi";
85 m_reg_map[k_machine_edi] = reginfo;
86 } else {
87 m_machine_ip_regnum = k_machine_rip;
88 m_machine_sp_regnum = k_machine_rsp;
89 m_machine_fp_regnum = k_machine_rbp;
90 m_machine_alt_fp_regnum = k_machine_rbx;
91 m_wordsize = 8;
92
93 struct lldb_reg_info reginfo;
94 reginfo.name = "rax";
95 m_reg_map[k_machine_rax] = reginfo;
96 reginfo.name = "rdx";
97 m_reg_map[k_machine_rdx] = reginfo;
98 reginfo.name = "rsp";
99 m_reg_map[k_machine_rsp] = reginfo;
100 reginfo.name = "rsi";
101 m_reg_map[k_machine_rsi] = reginfo;
102 reginfo.name = "r8";
103 m_reg_map[k_machine_r8] = reginfo;
104 reginfo.name = "r10";
105 m_reg_map[k_machine_r10] = reginfo;
106 reginfo.name = "r12";
107 m_reg_map[k_machine_r12] = reginfo;
108 reginfo.name = "r14";
109 m_reg_map[k_machine_r14] = reginfo;
110 reginfo.name = "rip";
111 m_reg_map[k_machine_rip] = reginfo;
112 reginfo.name = "rcx";
113 m_reg_map[k_machine_rcx] = reginfo;
114 reginfo.name = "rbx";
115 m_reg_map[k_machine_rbx] = reginfo;
116 reginfo.name = "rbp";
117 m_reg_map[k_machine_rbp] = reginfo;
118 reginfo.name = "rdi";
119 m_reg_map[k_machine_rdi] = reginfo;
120 reginfo.name = "r9";
121 m_reg_map[k_machine_r9] = reginfo;
122 reginfo.name = "r11";
123 m_reg_map[k_machine_r11] = reginfo;
124 reginfo.name = "r13";
125 m_reg_map[k_machine_r13] = reginfo;
126 reginfo.name = "r15";
127 m_reg_map[k_machine_r15] = reginfo;
128 }
129
130 for (MachineRegnumToNameAndLLDBRegnum::iterator it = m_reg_map.begin();
131 it != m_reg_map.end(); ++it) {
132 const RegisterInfo *ri = reg_ctx->GetRegisterInfoByName(it->second.name);
133 if (ri)
134 it->second.lldb_regnum = ri->kinds[eRegisterKindLLDB];
135 }
136
137 uint32_t lldb_regno;
138 if (machine_regno_to_lldb_regno(m_machine_sp_regnum, lldb_regno))
139 m_lldb_sp_regnum = lldb_regno;
140 if (machine_regno_to_lldb_regno(m_machine_fp_regnum, lldb_regno))
141 m_lldb_fp_regnum = lldb_regno;
142 if (machine_regno_to_lldb_regno(m_machine_alt_fp_regnum, lldb_regno))
143 m_lldb_alt_fp_regnum = lldb_regno;
144 if (machine_regno_to_lldb_regno(m_machine_ip_regnum, lldb_regno))
145 m_lldb_ip_regnum = lldb_regno;
146
147 m_register_map_initialized = true;
148}
149
150void x86AssemblyInspectionEngine::Initialize(
151 std::vector<lldb_reg_info> &reg_info) {
152 m_cpu = k_cpu_unspecified;
153 m_wordsize = -1;
154 m_register_map_initialized = false;
155
156 const llvm::Triple::ArchType cpu = m_arch.GetMachine();
157 if (cpu == llvm::Triple::x86)
158 m_cpu = k_i386;
159 else if (cpu == llvm::Triple::x86_64)
160 m_cpu = k_x86_64;
161
162 if (m_cpu == k_cpu_unspecified)
163 return;
164
165 if (m_cpu == k_i386) {
166 m_machine_ip_regnum = k_machine_eip;
167 m_machine_sp_regnum = k_machine_esp;
168 m_machine_fp_regnum = k_machine_ebp;
169 m_machine_alt_fp_regnum = k_machine_ebx;
170 m_wordsize = 4;
171
172 struct lldb_reg_info reginfo;
173 reginfo.name = "eax";
174 m_reg_map[k_machine_eax] = reginfo;
175 reginfo.name = "edx";
176 m_reg_map[k_machine_edx] = reginfo;
177 reginfo.name = "esp";
178 m_reg_map[k_machine_esp] = reginfo;
179 reginfo.name = "esi";
180 m_reg_map[k_machine_esi] = reginfo;
181 reginfo.name = "eip";
182 m_reg_map[k_machine_eip] = reginfo;
183 reginfo.name = "ecx";
184 m_reg_map[k_machine_ecx] = reginfo;
185 reginfo.name = "ebx";
186 m_reg_map[k_machine_ebx] = reginfo;
187 reginfo.name = "ebp";
188 m_reg_map[k_machine_ebp] = reginfo;
189 reginfo.name = "edi";
190 m_reg_map[k_machine_edi] = reginfo;
191 } else {
192 m_machine_ip_regnum = k_machine_rip;
193 m_machine_sp_regnum = k_machine_rsp;
194 m_machine_fp_regnum = k_machine_rbp;
195 m_machine_alt_fp_regnum = k_machine_rbx;
196 m_wordsize = 8;
197
198 struct lldb_reg_info reginfo;
199 reginfo.name = "rax";
200 m_reg_map[k_machine_rax] = reginfo;
201 reginfo.name = "rdx";
202 m_reg_map[k_machine_rdx] = reginfo;
203 reginfo.name = "rsp";
204 m_reg_map[k_machine_rsp] = reginfo;
205 reginfo.name = "rsi";
206 m_reg_map[k_machine_rsi] = reginfo;
207 reginfo.name = "r8";
208 m_reg_map[k_machine_r8] = reginfo;
209 reginfo.name = "r10";
210 m_reg_map[k_machine_r10] = reginfo;
211 reginfo.name = "r12";
212 m_reg_map[k_machine_r12] = reginfo;
213 reginfo.name = "r14";
214 m_reg_map[k_machine_r14] = reginfo;
215 reginfo.name = "rip";
216 m_reg_map[k_machine_rip] = reginfo;
217 reginfo.name = "rcx";
218 m_reg_map[k_machine_rcx] = reginfo;
219 reginfo.name = "rbx";
220 m_reg_map[k_machine_rbx] = reginfo;
221 reginfo.name = "rbp";
222 m_reg_map[k_machine_rbp] = reginfo;
223 reginfo.name = "rdi";
224 m_reg_map[k_machine_rdi] = reginfo;
225 reginfo.name = "r9";
226 m_reg_map[k_machine_r9] = reginfo;
227 reginfo.name = "r11";
228 m_reg_map[k_machine_r11] = reginfo;
229 reginfo.name = "r13";
230 m_reg_map[k_machine_r13] = reginfo;
231 reginfo.name = "r15";
232 m_reg_map[k_machine_r15] = reginfo;
233 }
234
235 for (MachineRegnumToNameAndLLDBRegnum::iterator it = m_reg_map.begin();
236 it != m_reg_map.end(); ++it) {
237 for (size_t i = 0; i < reg_info.size(); ++i) {
238 if (::strcmp(reg_info[i].name, it->second.name) == 0) {
239 it->second.lldb_regnum = reg_info[i].lldb_regnum;
240 break;
241 }
242 }
243 }
244
245 uint32_t lldb_regno;
246 if (machine_regno_to_lldb_regno(m_machine_sp_regnum, lldb_regno))
247 m_lldb_sp_regnum = lldb_regno;
248 if (machine_regno_to_lldb_regno(m_machine_fp_regnum, lldb_regno))
249 m_lldb_fp_regnum = lldb_regno;
250 if (machine_regno_to_lldb_regno(m_machine_alt_fp_regnum, lldb_regno))
251 m_lldb_alt_fp_regnum = lldb_regno;
252 if (machine_regno_to_lldb_regno(m_machine_ip_regnum, lldb_regno))
253 m_lldb_ip_regnum = lldb_regno;
254
255 m_register_map_initialized = true;
256}
257
258// This function expects an x86 native register number (i.e. the bits stripped
259// out of the actual instruction), not an lldb register number.
260//
261// FIXME: This is ABI dependent, it shouldn't be hardcoded here.
262
263bool x86AssemblyInspectionEngine::nonvolatile_reg_p(int machine_regno) {
264 if (m_cpu == k_i386) {
265 switch (machine_regno) {
266 case k_machine_ebx:
267 case k_machine_ebp: // not actually a nonvolatile but often treated as such
268 // by convention
269 case k_machine_esi:
270 case k_machine_edi:
271 case k_machine_esp:
272 return true;
273 default:
274 return false;
275 }
276 }
277 if (m_cpu == k_x86_64) {
278 switch (machine_regno) {
279 case k_machine_rbx:
280 case k_machine_rsp:
281 case k_machine_rbp: // not actually a nonvolatile but often treated as such
282 // by convention
283 case k_machine_r12:
284 case k_machine_r13:
285 case k_machine_r14:
286 case k_machine_r15:
287 return true;
288 default:
289 return false;
290 }
291 }
292 return false;
293}
294
295// Macro to detect if this is a REX mode prefix byte.
296#define REX_W_PREFIX_P(opcode)(((opcode) & (~0x5)) == 0x48) (((opcode) & (~0x5)) == 0x48)
297
298// The high bit which should be added to the source register number (the "R"
299// bit)
300#define REX_W_SRCREG(opcode)(((opcode)&0x4) >> 2) (((opcode)&0x4) >> 2)
301
302// The high bit which should be added to the destination register number (the
303// "B" bit)
304#define REX_W_DSTREG(opcode)((opcode)&0x1) ((opcode)&0x1)
305
306// pushq %rbp [0x55]
307bool x86AssemblyInspectionEngine::push_rbp_pattern_p() {
308 uint8_t *p = m_cur_insn;
309 return *p == 0x55;
310}
311
312// pushq $0 ; the first instruction in start() [0x6a 0x00]
313bool x86AssemblyInspectionEngine::push_0_pattern_p() {
314 uint8_t *p = m_cur_insn;
315 return *p == 0x6a && *(p + 1) == 0x0;
316}
317
318// pushq $0
319// pushl $0
320bool x86AssemblyInspectionEngine::push_imm_pattern_p() {
321 uint8_t *p = m_cur_insn;
322 return *p == 0x68 || *p == 0x6a;
323}
324
325// pushl imm8(%esp)
326//
327// e.g. 0xff 0x74 0x24 0x20 - 'pushl 0x20(%esp)' (same byte pattern for 'pushq
328// 0x20(%rsp)' in an x86_64 program)
329//
330// 0xff (with opcode bits '6' in next byte, PUSH r/m32) 0x74 (ModR/M byte with
331// three bits used to specify the opcode)
332// mod == b01, opcode == b110, R/M == b100
333// "+disp8"
334// 0x24 (SIB byte - scaled index = 0, r32 == esp) 0x20 imm8 value
335
336bool x86AssemblyInspectionEngine::push_extended_pattern_p() {
337 if (*m_cur_insn == 0xff) {
338 // Get the 3 opcode bits from the ModR/M byte
339 uint8_t opcode = (*(m_cur_insn + 1) >> 3) & 7;
340 if (opcode == 6) {
341 // I'm only looking for 0xff /6 here - I
342 // don't really care what value is being pushed, just that we're pushing
343 // a 32/64 bit value on to the stack is enough.
344 return true;
345 }
346 }
347 return false;
348}
349
350// instructions only valid in 32-bit mode:
351// 0x0e - push cs
352// 0x16 - push ss
353// 0x1e - push ds
354// 0x06 - push es
355bool x86AssemblyInspectionEngine::push_misc_reg_p() {
356 uint8_t p = *m_cur_insn;
357 if (m_wordsize == 4) {
358 if (p == 0x0e || p == 0x16 || p == 0x1e || p == 0x06)
359 return true;
360 }
361 return false;
362}
363
364// pushq %rbx
365// pushl %ebx
366bool x86AssemblyInspectionEngine::push_reg_p(int &regno) {
367 uint8_t *p = m_cur_insn;
368 int regno_prefix_bit = 0;
369 // If we have a rex prefix byte, check to see if a B bit is set
370 if (m_wordsize == 8 && (*p & 0xfe) == 0x40) {
371 regno_prefix_bit = (*p & 1) << 3;
372 p++;
373 }
374 if (*p >= 0x50 && *p <= 0x57) {
375 regno = (*p - 0x50) | regno_prefix_bit;
376 return true;
377 }
378 return false;
379}
380
381// movq %rsp, %rbp [0x48 0x8b 0xec] or [0x48 0x89 0xe5] movl %esp, %ebp [0x8b
382// 0xec] or [0x89 0xe5]
383bool x86AssemblyInspectionEngine::mov_rsp_rbp_pattern_p() {
384 uint8_t *p = m_cur_insn;
385 if (m_wordsize == 8 && *p == 0x48)
386 p++;
387 if (*(p) == 0x8b && *(p + 1) == 0xec)
388 return true;
389 if (*(p) == 0x89 && *(p + 1) == 0xe5)
390 return true;
391 return false;
392}
393
394// movq %rsp, %rbx [0x48 0x8b 0xdc] or [0x48 0x89 0xe3]
395// movl %esp, %ebx [0x8b 0xdc] or [0x89 0xe3]
396bool x86AssemblyInspectionEngine::mov_rsp_rbx_pattern_p() {
397 uint8_t *p = m_cur_insn;
398 if (m_wordsize == 8 && *p == 0x48)
399 p++;
400 if (*(p) == 0x8b && *(p + 1) == 0xdc)
401 return true;
402 if (*(p) == 0x89 && *(p + 1) == 0xe3)
403 return true;
404 return false;
405}
406
407// movq %rbp, %rsp [0x48 0x8b 0xe5] or [0x48 0x89 0xec]
408// movl %ebp, %esp [0x8b 0xe5] or [0x89 0xec]
409bool x86AssemblyInspectionEngine::mov_rbp_rsp_pattern_p() {
410 uint8_t *p = m_cur_insn;
411 if (m_wordsize == 8 && *p == 0x48)
412 p++;
413 if (*(p) == 0x8b && *(p + 1) == 0xe5)
414 return true;
415 if (*(p) == 0x89 && *(p + 1) == 0xec)
416 return true;
417 return false;
418}
419
420// movq %rbx, %rsp [0x48 0x8b 0xe3] or [0x48 0x89 0xdc]
421// movl %ebx, %esp [0x8b 0xe3] or [0x89 0xdc]
422bool x86AssemblyInspectionEngine::mov_rbx_rsp_pattern_p() {
423 uint8_t *p = m_cur_insn;
424 if (m_wordsize == 8 && *p == 0x48)
425 p++;
426 if (*(p) == 0x8b && *(p + 1) == 0xe3)
427 return true;
428 if (*(p) == 0x89 && *(p + 1) == 0xdc)
429 return true;
430 return false;
431}
432
433// subq $0x20, %rsp
434bool x86AssemblyInspectionEngine::sub_rsp_pattern_p(int &amount) {
435 uint8_t *p = m_cur_insn;
436 if (m_wordsize == 8 && *p == 0x48)
437 p++;
438 // 8-bit immediate operand
439 if (*p == 0x83 && *(p + 1) == 0xec) {
440 amount = (int8_t) * (p + 2);
441 return true;
442 }
443 // 32-bit immediate operand
444 if (*p == 0x81 && *(p + 1) == 0xec) {
445 amount = (int32_t)extract_4(p + 2);
446 return true;
447 }
448 return false;
449}
450
451// addq $0x20, %rsp
452bool x86AssemblyInspectionEngine::add_rsp_pattern_p(int &amount) {
453 uint8_t *p = m_cur_insn;
454 if (m_wordsize == 8 && *p == 0x48)
455 p++;
456 // 8-bit immediate operand
457 if (*p == 0x83 && *(p + 1) == 0xc4) {
458 amount = (int8_t) * (p + 2);
459 return true;
460 }
461 // 32-bit immediate operand
462 if (*p == 0x81 && *(p + 1) == 0xc4) {
463 amount = (int32_t)extract_4(p + 2);
464 return true;
465 }
466 return false;
467}
468
469// lea esp, [esp - 0x28]
470// lea esp, [esp + 0x28]
471bool x86AssemblyInspectionEngine::lea_rsp_pattern_p(int &amount) {
472 uint8_t *p = m_cur_insn;
473 if (m_wordsize == 8 && *p == 0x48)
474 p++;
475
476 // Check opcode
477 if (*p != 0x8d)
478 return false;
479
480 // 8 bit displacement
481 if (*(p + 1) == 0x64 && (*(p + 2) & 0x3f) == 0x24) {
482 amount = (int8_t) * (p + 3);
483 return true;
484 }
485
486 // 32 bit displacement
487 if (*(p + 1) == 0xa4 && (*(p + 2) & 0x3f) == 0x24) {
488 amount = (int32_t)extract_4(p + 3);
489 return true;
490 }
491
492 return false;
493}
494
495// lea -0x28(%ebp), %esp
496// (32-bit and 64-bit variants, 8-bit and 32-bit displacement)
497bool x86AssemblyInspectionEngine::lea_rbp_rsp_pattern_p(int &amount) {
498 uint8_t *p = m_cur_insn;
499 if (m_wordsize == 8 && *p == 0x48)
500 p++;
501
502 // Check opcode
503 if (*p != 0x8d)
504 return false;
505 ++p;
506
507 // 8 bit displacement
508 if (*p == 0x65) {
509 amount = (int8_t)p[1];
510 return true;
511 }
512
513 // 32 bit displacement
514 if (*p == 0xa5) {
515 amount = (int32_t)extract_4(p + 1);
516 return true;
517 }
518
519 return false;
520}
521
522// lea -0x28(%ebx), %esp
523// (32-bit and 64-bit variants, 8-bit and 32-bit displacement)
524bool x86AssemblyInspectionEngine::lea_rbx_rsp_pattern_p(int &amount) {
525 uint8_t *p = m_cur_insn;
526 if (m_wordsize == 8 && *p == 0x48)
527 p++;
528
529 // Check opcode
530 if (*p != 0x8d)
531 return false;
532 ++p;
533
534 // 8 bit displacement
535 if (*p == 0x63) {
536 amount = (int8_t)p[1];
537 return true;
538 }
539
540 // 32 bit displacement
541 if (*p == 0xa3) {
542 amount = (int32_t)extract_4(p + 1);
543 return true;
544 }
545
546 return false;
547}
548
549// and -0xfffffff0, %esp
550// (32-bit and 64-bit variants, 8-bit and 32-bit displacement)
551bool x86AssemblyInspectionEngine::and_rsp_pattern_p() {
552 uint8_t *p = m_cur_insn;
553 if (m_wordsize == 8 && *p == 0x48)
554 p++;
555
556 if (*p != 0x81 && *p != 0x83)
557 return false;
558
559 return *++p == 0xe4;
560}
561
562// popq %rbx
563// popl %ebx
564bool x86AssemblyInspectionEngine::pop_reg_p(int &regno) {
565 uint8_t *p = m_cur_insn;
566 int regno_prefix_bit = 0;
567 // If we have a rex prefix byte, check to see if a B bit is set
568 if (m_wordsize == 8 && (*p & 0xfe) == 0x40) {
569 regno_prefix_bit = (*p & 1) << 3;
570 p++;
571 }
572 if (*p >= 0x58 && *p <= 0x5f) {
573 regno = (*p - 0x58) | regno_prefix_bit;
574 return true;
575 }
576 return false;
577}
578
579// popq %rbp [0x5d]
580// popl %ebp [0x5d]
581bool x86AssemblyInspectionEngine::pop_rbp_pattern_p() {
582 uint8_t *p = m_cur_insn;
583 return (*p == 0x5d);
584}
585
586// instructions valid only in 32-bit mode:
587// 0x1f - pop ds
588// 0x07 - pop es
589// 0x17 - pop ss
590bool x86AssemblyInspectionEngine::pop_misc_reg_p() {
591 uint8_t p = *m_cur_insn;
592 if (m_wordsize == 4) {
593 if (p == 0x1f || p == 0x07 || p == 0x17)
594 return true;
595 }
596 return false;
597}
598
599// leave [0xc9]
600bool x86AssemblyInspectionEngine::leave_pattern_p() {
601 uint8_t *p = m_cur_insn;
602 return (*p == 0xc9);
603}
604
605// call $0 [0xe8 0x0 0x0 0x0 0x0]
606bool x86AssemblyInspectionEngine::call_next_insn_pattern_p() {
607 uint8_t *p = m_cur_insn;
608 return (*p == 0xe8) && (*(p + 1) == 0x0) && (*(p + 2) == 0x0) &&
609 (*(p + 3) == 0x0) && (*(p + 4) == 0x0);
610}
611
612// Look for an instruction sequence storing a nonvolatile register on to the
613// stack frame.
614
615// movq %rax, -0x10(%rbp) [0x48 0x89 0x45 0xf0]
616// movl %eax, -0xc(%ebp) [0x89 0x45 0xf4]
617
618// The offset value returned in rbp_offset will be positive -- but it must be
619// subtraced from the frame base register to get the actual location. The
620// positive value returned for the offset is a convention used elsewhere for
621// CFA offsets et al.
622
623bool x86AssemblyInspectionEngine::mov_reg_to_local_stack_frame_p(
624 int &regno, int &rbp_offset) {
625 uint8_t *p = m_cur_insn;
626 int src_reg_prefix_bit = 0;
627 int target_reg_prefix_bit = 0;
628
629 if (m_wordsize == 8 && REX_W_PREFIX_P(*p)(((*p) & (~0x5)) == 0x48)) {
630 src_reg_prefix_bit = REX_W_SRCREG(*p)(((*p)&0x4) >> 2) << 3;
631 target_reg_prefix_bit = REX_W_DSTREG(*p)((*p)&0x1) << 3;
632 if (target_reg_prefix_bit == 1) {
633 // rbp/ebp don't need a prefix bit - we know this isn't the reg we care
634 // about.
635 return false;
636 }
637 p++;
638 }
639
640 if (*p == 0x89) {
641 /* Mask off the 3-5 bits which indicate the destination register
642 if this is a ModR/M byte. */
643 int opcode_destreg_masked_out = *(p + 1) & (~0x38);
644
645 /* Is this a ModR/M byte with Mod bits 01 and R/M bits 101
646 and three bits between them, e.g. 01nnn101
647 We're looking for a destination of ebp-disp8 or ebp-disp32. */
648 int immsize;
649 if (opcode_destreg_masked_out == 0x45)
650 immsize = 2;
651 else if (opcode_destreg_masked_out == 0x85)
652 immsize = 4;
653 else
654 return false;
655
656 int offset = 0;
657 if (immsize == 2)
658 offset = (int8_t) * (p + 2);
659 if (immsize == 4)
660 offset = (uint32_t)extract_4(p + 2);
661 if (offset > 0)
662 return false;
663
664 regno = ((*(p + 1) >> 3) & 0x7) | src_reg_prefix_bit;
665 rbp_offset = offset > 0 ? offset : -offset;
666 return true;
667 }
668 return false;
669}
670
671// Returns true if this is a jmp instruction where we can't
672// know the destination address statically.
673//
674// ff e0 jmpq *%rax
675// ff e1 jmpq *%rcx
676// ff 60 28 jmpq *0x28(%rax)
677// ff 60 60 jmpq *0x60(%rax)
678bool x86AssemblyInspectionEngine::jmp_to_reg_p() {
679 if (*m_cur_insn != 0xff)
680 return false;
681
682 // The second byte is a ModR/M /4 byte, strip off the registers
683 uint8_t second_byte_sans_reg = *(m_cur_insn + 1) & ~7;
684
685 // [reg]
686 if (second_byte_sans_reg == 0x20)
687 return true;
688
689 // [reg]+disp8
690 if (second_byte_sans_reg == 0x60)
691 return true;
692
693 // [reg]+disp32
694 if (second_byte_sans_reg == 0xa0)
695 return true;
696
697 // reg
698 if (second_byte_sans_reg == 0xe0)
699 return true;
700
701 return false;
702}
703
704// Detect branches to fixed pc-relative offsets.
705// Returns the offset from the address of the next instruction
706// that may be branch/jumped to.
707//
708// Cannot determine the offset of a JMP that jumps to the address in
709// a register ("jmpq *%rax") or offset from a register value
710// ("jmpq *0x28(%rax)"), this method will return false on those
711// instructions.
712//
713// These instructions all end in either a relative 8/16/32 bit value
714// depending on the instruction and the current execution mode of the
715// inferior process. Once we know the size of the opcode instruction,
716// we can use the total instruction length to determine the size of
717// the relative offset without having to compute it correctly.
718
719bool x86AssemblyInspectionEngine::pc_rel_branch_or_jump_p (
720 const int instruction_length, int &offset)
721{
722 int opcode_size = 0;
723
724 uint8_t b1 = m_cur_insn[0];
725
726 switch (b1) {
727 case 0x77: // JA/JNBE rel8
728 case 0x73: // JAE/JNB/JNC rel8
729 case 0x72: // JB/JC/JNAE rel8
730 case 0x76: // JBE/JNA rel8
731 case 0xe3: // JCXZ/JECXZ/JRCXZ rel8
732 case 0x74: // JE/JZ rel8
733 case 0x7f: // JG/JNLE rel8
734 case 0x7d: // JGE/JNL rel8
735 case 0x7c: // JL/JNGE rel8
736 case 0x7e: // JNG/JLE rel8
737 case 0x71: // JNO rel8
738 case 0x7b: // JNP/JPO rel8
739 case 0x79: // JNS rel8
740 case 0x75: // JNE/JNZ rel8
741 case 0x70: // JO rel8
742 case 0x7a: // JP/JPE rel8
743 case 0x78: // JS rel8
744 case 0xeb: // JMP rel8
745 case 0xe9: // JMP rel16/rel32
746 opcode_size = 1;
747 break;
748 default:
749 break;
750 }
751 if (b1 == 0x0f && opcode_size == 0) {
752 uint8_t b2 = m_cur_insn[1];
753 switch (b2) {
754 case 0x87: // JA/JNBE rel16/rel32
755 case 0x86: // JBE/JNA rel16/rel32
756 case 0x84: // JE/JZ rel16/rel32
757 case 0x8f: // JG/JNLE rel16/rel32
758 case 0x8d: // JNL/JGE rel16/rel32
759 case 0x8e: // JLE rel16/rel32
760 case 0x82: // JB/JC/JNAE rel16/rel32
761 case 0x83: // JAE/JNB/JNC rel16/rel32
762 case 0x85: // JNE/JNZ rel16/rel32
763 case 0x8c: // JL/JNGE rel16/rel32
764 case 0x81: // JNO rel16/rel32
765 case 0x8b: // JNP/JPO rel16/rel32
766 case 0x89: // JNS rel16/rel32
767 case 0x80: // JO rel16/rel32
768 case 0x8a: // JP rel16/rel32
769 case 0x88: // JS rel16/rel32
770 opcode_size = 2;
771 break;
772 default:
773 break;
774 }
775 }
776
777 if (opcode_size == 0)
778 return false;
779
780 offset = 0;
781 if (instruction_length - opcode_size == 1) {
782 int8_t rel8 = (int8_t) *(m_cur_insn + opcode_size);
783 offset = rel8;
784 } else if (instruction_length - opcode_size == 2) {
785 int16_t rel16 = extract_2_signed (m_cur_insn + opcode_size);
786 offset = rel16;
787 } else if (instruction_length - opcode_size == 4) {
788 int32_t rel32 = extract_4_signed (m_cur_insn + opcode_size);
789 offset = rel32;
790 } else {
791 return false;
792 }
793 return true;
794}
795
796// Returns true if this instruction is a intra-function branch or jump -
797// a branch/jump within the bounds of this same function.
798// Cannot predict where a jump through a register value ("jmpq *%rax")
799// will go, so it will return false on that instruction.
800bool x86AssemblyInspectionEngine::local_branch_p (
801 const addr_t current_func_text_offset,
802 const AddressRange &func_range,
803 const int instruction_length,
804 addr_t &target_insn_offset) {
805 int offset;
806 if (pc_rel_branch_or_jump_p (instruction_length, offset) && offset != 0) {
807 addr_t next_pc_value = current_func_text_offset + instruction_length;
808 if (offset < 0 && addr_t(-offset) > current_func_text_offset) {
809 // Branch target is before the start of this function
810 return false;
811 }
812 if (offset + next_pc_value > func_range.GetByteSize()) {
813 // Branch targets outside this function's bounds
814 return false;
815 }
816 // This instruction branches to target_insn_offset (byte offset into the function)
817 target_insn_offset = next_pc_value + offset;
818 return true;
819 }
820 return false;
821}
822
823// Returns true if this instruction is a inter-function branch or jump - a
824// branch/jump to another function.
825// Cannot predict where a jump through a register value ("jmpq *%rax")
826// will go, so it will return false on that instruction.
827bool x86AssemblyInspectionEngine::non_local_branch_p (
828 const addr_t current_func_text_offset,
829 const AddressRange &func_range,
830 const int instruction_length) {
831 int offset;
832 addr_t target_insn_offset;
833 if (pc_rel_branch_or_jump_p (instruction_length, offset)) {
834 return !local_branch_p(current_func_text_offset,func_range,instruction_length,target_insn_offset);
835 }
836 return false;
837}
838
839// ret [0xc3] or [0xcb] or [0xc2 imm16] or [0xca imm16]
840bool x86AssemblyInspectionEngine::ret_pattern_p() {
841 uint8_t *p = m_cur_insn;
842 return *p == 0xc3 || *p == 0xc2 || *p == 0xca || *p == 0xcb;
843}
844
845uint16_t x86AssemblyInspectionEngine::extract_2(uint8_t *b) {
846 uint16_t v = 0;
847 for (int i = 1; i >= 0; i--)
848 v = (v << 8) | b[i];
849 return v;
850}
851
852int16_t x86AssemblyInspectionEngine::extract_2_signed(uint8_t *b) {
853 int16_t v = 0;
854 for (int i = 1; i >= 0; i--)
855 v = (v << 8) | b[i];
856 return v;
857}
858
859uint32_t x86AssemblyInspectionEngine::extract_4(uint8_t *b) {
860 uint32_t v = 0;
861 for (int i = 3; i >= 0; i--)
862 v = (v << 8) | b[i];
863 return v;
864}
865
866int32_t x86AssemblyInspectionEngine::extract_4_signed(uint8_t *b) {
867 int32_t v = 0;
868 for (int i = 3; i >= 0; i--)
869 v = (v << 8) | b[i];
870 return v;
871}
872
873
874bool x86AssemblyInspectionEngine::instruction_length(uint8_t *insn_p,
875 int &length,
876 uint32_t buffer_remaining_bytes) {
877
878 uint32_t max_op_byte_size = std::min(buffer_remaining_bytes, m_arch.GetMaximumOpcodeByteSize());
879 llvm::SmallVector<uint8_t, 32> opcode_data;
880 opcode_data.resize(max_op_byte_size);
881
882 char out_string[512];
883 const size_t inst_size =
884 ::LLVMDisasmInstruction(m_disasm_context, insn_p, max_op_byte_size, 0,
885 out_string, sizeof(out_string));
886
887 length = inst_size;
888 return true;
889}
890
891bool x86AssemblyInspectionEngine::machine_regno_to_lldb_regno(
892 int machine_regno, uint32_t &lldb_regno) {
893 MachineRegnumToNameAndLLDBRegnum::iterator it = m_reg_map.find(machine_regno);
894 if (it != m_reg_map.end()) {
895 lldb_regno = it->second.lldb_regnum;
896 return true;
897 }
898 return false;
899}
900
901bool x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(
902 uint8_t *data, size_t size, AddressRange &func_range,
903 UnwindPlan &unwind_plan) {
904 unwind_plan.Clear();
905
906 if (data == nullptr || size == 0)
907 return false;
908
909 if (!m_register_map_initialized)
910 return false;
911
912 addr_t current_func_text_offset = 0;
913 int current_sp_bytes_offset_from_fa = 0;
914 bool is_aligned = false;
915 UnwindPlan::Row::RegisterLocation initial_regloc;
916 UnwindPlan::RowSP row(new UnwindPlan::Row);
917
918 unwind_plan.SetPlanValidAddressRange(func_range);
919 unwind_plan.SetRegisterKind(eRegisterKindLLDB);
920
921 // At the start of the function, find the CFA by adding wordsize to the SP
922 // register
923 row->SetOffset(current_func_text_offset);
924 row->GetCFAValue().SetIsRegisterPlusOffset(m_lldb_sp_regnum, m_wordsize);
925
926 // caller's stack pointer value before the call insn is the CFA address
927 initial_regloc.SetIsCFAPlusOffset(0);
928 row->SetRegisterInfo(m_lldb_sp_regnum, initial_regloc);
929
930 // saved instruction pointer can be found at CFA - wordsize.
931 current_sp_bytes_offset_from_fa = m_wordsize;
932 initial_regloc.SetAtCFAPlusOffset(-current_sp_bytes_offset_from_fa);
933 row->SetRegisterInfo(m_lldb_ip_regnum, initial_regloc);
934
935 unwind_plan.AppendRow(row);
936
937 // Allocate a new Row, populate it with the existing Row contents.
938 UnwindPlan::Row *newrow = new UnwindPlan::Row;
939 *newrow = *row.get();
940 row.reset(newrow);
941
942 // Track which registers have been saved so far in the prologue. If we see
943 // another push of that register, it's not part of the prologue. The register
944 // numbers used here are the machine register #'s (i386_register_numbers,
945 // x86_64_register_numbers).
946 std::vector<bool> saved_registers(32, false);
947
948 // Once the prologue has completed we'll save a copy of the unwind
949 // instructions If there is an epilogue in the middle of the function, after
950 // that epilogue we'll reinstate the unwind setup -- we assume that some code
951 // path jumps over the mid-function epilogue
952
953 UnwindPlan::RowSP prologue_completed_row; // copy of prologue row of CFI
954 int prologue_completed_sp_bytes_offset_from_cfa = 0; // The sp value before the
955 // epilogue started executed
956 bool prologue_completed_is_aligned = false;
957 std::vector<bool> prologue_completed_saved_registers;
958
959 while (current_func_text_offset < size) {
960 int stack_offset, insn_len;
961 int machine_regno; // register numbers masked directly out of instructions
962 uint32_t lldb_regno; // register numbers in lldb's eRegisterKindLLDB
963 // numbering scheme
964
965 bool in_epilogue = false; // we're in the middle of an epilogue sequence
966 bool row_updated = false; // The UnwindPlan::Row 'row' has been updated
967
968 m_cur_insn = data + current_func_text_offset;
969 if (!instruction_length(m_cur_insn, insn_len, size - current_func_text_offset)
970 || insn_len == 0
971 || insn_len > kMaxInstructionByteSize) {
972 // An unrecognized/junk instruction
973 break;
974 }
975
976 auto &cfa_value = row->GetCFAValue();
977 auto &afa_value = row->GetAFAValue();
978 auto fa_value_ptr = is_aligned ? &afa_value : &cfa_value;
979
980 if (mov_rsp_rbp_pattern_p()) {
981 if (fa_value_ptr->GetRegisterNumber() == m_lldb_sp_regnum) {
982 fa_value_ptr->SetIsRegisterPlusOffset(
983 m_lldb_fp_regnum, fa_value_ptr->GetOffset());
984 row_updated = true;
985 }
986 }
987
988 else if (mov_rsp_rbx_pattern_p()) {
989 if (fa_value_ptr->GetRegisterNumber() == m_lldb_sp_regnum) {
990 fa_value_ptr->SetIsRegisterPlusOffset(
991 m_lldb_alt_fp_regnum, fa_value_ptr->GetOffset());
992 row_updated = true;
993 }
994 }
995
996 else if (and_rsp_pattern_p()) {
997 current_sp_bytes_offset_from_fa = 0;
998 afa_value.SetIsRegisterPlusOffset(
999 m_lldb_sp_regnum, current_sp_bytes_offset_from_fa);
1000 fa_value_ptr = &afa_value;
Value stored to 'fa_value_ptr' is never read
1001 is_aligned = true;
1002 row_updated = true;
1003 }
1004
1005 else if (mov_rbp_rsp_pattern_p()) {
1006 if (is_aligned && cfa_value.GetRegisterNumber() == m_lldb_fp_regnum)
1007 {
1008 is_aligned = false;
1009 fa_value_ptr = &cfa_value;
1010 afa_value.SetUnspecified();
1011 row_updated = true;
1012 }
1013 if (fa_value_ptr->GetRegisterNumber() == m_lldb_fp_regnum)
1014 current_sp_bytes_offset_from_fa = fa_value_ptr->GetOffset();
1015 }
1016
1017 else if (mov_rbx_rsp_pattern_p()) {
1018 if (is_aligned && cfa_value.GetRegisterNumber() == m_lldb_alt_fp_regnum)
1019 {
1020 is_aligned = false;
1021 fa_value_ptr = &cfa_value;
1022 afa_value.SetUnspecified();
1023 row_updated = true;
1024 }
1025 if (fa_value_ptr->GetRegisterNumber() == m_lldb_alt_fp_regnum)
1026 current_sp_bytes_offset_from_fa = fa_value_ptr->GetOffset();
1027 }
1028
1029 // This is the start() function (or a pthread equivalent), it starts with a
1030 // pushl $0x0 which puts the saved pc value of 0 on the stack. In this
1031 // case we want to pretend we didn't see a stack movement at all --
1032 // normally the saved pc value is already on the stack by the time the
1033 // function starts executing.
1034 else if (push_0_pattern_p()) {
1035 }
1036
1037 else if (push_reg_p(machine_regno)) {
1038 current_sp_bytes_offset_from_fa += m_wordsize;
1039 // the PUSH instruction has moved the stack pointer - if the FA is set
1040 // in terms of the stack pointer, we need to add a new row of
1041 // instructions.
1042 if (fa_value_ptr->GetRegisterNumber() == m_lldb_sp_regnum) {
1043 fa_value_ptr->SetOffset(current_sp_bytes_offset_from_fa);
1044 row_updated = true;
1045 }
1046 // record where non-volatile (callee-saved, spilled) registers are saved
1047 // on the stack
1048 if (nonvolatile_reg_p(machine_regno) &&
1049 machine_regno_to_lldb_regno(machine_regno, lldb_regno) &&
1050 !saved_registers[machine_regno]) {
1051 UnwindPlan::Row::RegisterLocation regloc;
1052 if (is_aligned)
1053 regloc.SetAtAFAPlusOffset(-current_sp_bytes_offset_from_fa);
1054 else
1055 regloc.SetAtCFAPlusOffset(-current_sp_bytes_offset_from_fa);
1056 row->SetRegisterInfo(lldb_regno, regloc);
1057 saved_registers[machine_regno] = true;
1058 row_updated = true;
1059 }
1060 }
1061
1062 else if (pop_reg_p(machine_regno)) {
1063 current_sp_bytes_offset_from_fa -= m_wordsize;
1064
1065 if (nonvolatile_reg_p(machine_regno) &&
1066 machine_regno_to_lldb_regno(machine_regno, lldb_regno) &&
1067 saved_registers[machine_regno]) {
1068 saved_registers[machine_regno] = false;
1069 row->RemoveRegisterInfo(lldb_regno);
1070
1071 if (lldb_regno == fa_value_ptr->GetRegisterNumber()) {
1072 fa_value_ptr->SetIsRegisterPlusOffset(
1073 m_lldb_sp_regnum, fa_value_ptr->GetOffset());
1074 }
1075
1076 in_epilogue = true;
1077 row_updated = true;
1078 }
1079
1080 // the POP instruction has moved the stack pointer - if the FA is set in
1081 // terms of the stack pointer, we need to add a new row of instructions.
1082 if (fa_value_ptr->GetRegisterNumber() == m_lldb_sp_regnum) {
1083 fa_value_ptr->SetIsRegisterPlusOffset(
1084 m_lldb_sp_regnum, current_sp_bytes_offset_from_fa);
1085 row_updated = true;
1086 }
1087 }
1088
1089 else if (pop_misc_reg_p()) {
1090 current_sp_bytes_offset_from_fa -= m_wordsize;
1091 if (fa_value_ptr->GetRegisterNumber() == m_lldb_sp_regnum) {
1092 fa_value_ptr->SetIsRegisterPlusOffset(
1093 m_lldb_sp_regnum, current_sp_bytes_offset_from_fa);
1094 row_updated = true;
1095 }
1096 }
1097
1098 // The LEAVE instruction moves the value from rbp into rsp and pops a value
1099 // off the stack into rbp (restoring the caller's rbp value). It is the
1100 // opposite of ENTER, or 'push rbp, mov rsp rbp'.
1101 else if (leave_pattern_p()) {
1102 if (saved_registers[m_machine_fp_regnum]) {
1103 saved_registers[m_machine_fp_regnum] = false;
1104 row->RemoveRegisterInfo(m_lldb_fp_regnum);
1105
1106 row_updated = true;
1107 }
1108
1109 if (is_aligned && cfa_value.GetRegisterNumber() == m_lldb_fp_regnum)
1110 {
1111 is_aligned = false;
1112 fa_value_ptr = &cfa_value;
1113 afa_value.SetUnspecified();
1114 row_updated = true;
1115 }
1116
1117 if (fa_value_ptr->GetRegisterNumber() == m_lldb_fp_regnum)
1118 {
1119 fa_value_ptr->SetIsRegisterPlusOffset(
1120 m_lldb_sp_regnum, fa_value_ptr->GetOffset());
1121
1122 current_sp_bytes_offset_from_fa = fa_value_ptr->GetOffset();
1123 }
1124
1125 current_sp_bytes_offset_from_fa -= m_wordsize;
1126
1127 if (fa_value_ptr->GetRegisterNumber() == m_lldb_sp_regnum) {
1128 fa_value_ptr->SetIsRegisterPlusOffset(
1129 m_lldb_sp_regnum, current_sp_bytes_offset_from_fa);
1130 row_updated = true;
1131 }
1132
1133 in_epilogue = true;
1134 }
1135
1136 else if (mov_reg_to_local_stack_frame_p(machine_regno, stack_offset) &&
1137 nonvolatile_reg_p(machine_regno) &&
1138 machine_regno_to_lldb_regno(machine_regno, lldb_regno) &&
1139 !saved_registers[machine_regno]) {
1140 saved_registers[machine_regno] = true;
1141
1142 UnwindPlan::Row::RegisterLocation regloc;
1143
1144 // stack_offset for 'movq %r15, -80(%rbp)' will be 80. In the Row, we
1145 // want to express this as the offset from the FA. If the frame base is
1146 // rbp (like the above instruction), the FA offset for rbp is probably
1147 // 16. So we want to say that the value is stored at the FA address -
1148 // 96.
1149 if (is_aligned)
1150 regloc.SetAtAFAPlusOffset(-(stack_offset + fa_value_ptr->GetOffset()));
1151 else
1152 regloc.SetAtCFAPlusOffset(-(stack_offset + fa_value_ptr->GetOffset()));
1153
1154 row->SetRegisterInfo(lldb_regno, regloc);
1155
1156 row_updated = true;
1157 }
1158
1159 else if (sub_rsp_pattern_p(stack_offset)) {
1160 current_sp_bytes_offset_from_fa += stack_offset;
1161 if (fa_value_ptr->GetRegisterNumber() == m_lldb_sp_regnum) {
1162 fa_value_ptr->SetOffset(current_sp_bytes_offset_from_fa);
1163 row_updated = true;
1164 }
1165 }
1166
1167 else if (add_rsp_pattern_p(stack_offset)) {
1168 current_sp_bytes_offset_from_fa -= stack_offset;
1169 if (fa_value_ptr->GetRegisterNumber() == m_lldb_sp_regnum) {
1170 fa_value_ptr->SetOffset(current_sp_bytes_offset_from_fa);
1171 row_updated = true;
1172 }
1173 in_epilogue = true;
1174 }
1175
1176 else if (push_extended_pattern_p() || push_imm_pattern_p() ||
1177 push_misc_reg_p()) {
1178 current_sp_bytes_offset_from_fa += m_wordsize;
1179 if (fa_value_ptr->GetRegisterNumber() == m_lldb_sp_regnum) {
1180 fa_value_ptr->SetOffset(current_sp_bytes_offset_from_fa);
1181 row_updated = true;
1182 }
1183 }
1184
1185 else if (lea_rsp_pattern_p(stack_offset)) {
1186 current_sp_bytes_offset_from_fa -= stack_offset;
1187 if (fa_value_ptr->GetRegisterNumber() == m_lldb_sp_regnum) {
1188 fa_value_ptr->SetOffset(current_sp_bytes_offset_from_fa);
1189 row_updated = true;
1190 }
1191 if (stack_offset > 0)
1192 in_epilogue = true;
1193 }
1194
1195 else if (lea_rbp_rsp_pattern_p(stack_offset)) {
1196 if (is_aligned &&
1197 cfa_value.GetRegisterNumber() == m_lldb_fp_regnum) {
1198 is_aligned = false;
1199 fa_value_ptr = &cfa_value;
1200 afa_value.SetUnspecified();
1201 row_updated = true;
1202 }
1203 if (fa_value_ptr->GetRegisterNumber() == m_lldb_fp_regnum) {
1204 current_sp_bytes_offset_from_fa =
1205 fa_value_ptr->GetOffset() - stack_offset;
1206 }
1207 }
1208
1209 else if (lea_rbx_rsp_pattern_p(stack_offset)) {
1210 if (is_aligned &&
1211 cfa_value.GetRegisterNumber() == m_lldb_alt_fp_regnum) {
1212 is_aligned = false;
1213 fa_value_ptr = &cfa_value;
1214 afa_value.SetUnspecified();
1215 row_updated = true;
1216 }
1217 if (fa_value_ptr->GetRegisterNumber() == m_lldb_alt_fp_regnum) {
1218 current_sp_bytes_offset_from_fa = fa_value_ptr->GetOffset() - stack_offset;
1219 }
1220 }
1221
1222 else if (prologue_completed_row.get() &&
1223 (ret_pattern_p() ||
1224 non_local_branch_p (current_func_text_offset, func_range, insn_len) ||
1225 jmp_to_reg_p())) {
1226 // Check if the current instruction is the end of an epilogue sequence,
1227 // and if so, re-instate the prologue-completed unwind state.
1228
1229 // The current instruction is a branch/jump outside this function,
1230 // a ret, or a jump through a register value which we cannot
1231 // determine the effcts of. Verify that the stack frame state
1232 // has been unwound to the same as it was at function entry to avoid
1233 // mis-identifying a JMP instruction as an epilogue.
1234 UnwindPlan::Row::RegisterLocation sp, pc;
1235 if (row->GetRegisterInfo(m_lldb_sp_regnum, sp) &&
1236 row->GetRegisterInfo(m_lldb_ip_regnum, pc)) {
1237 // Any ret instruction variant is definitely indicative of an
1238 // epilogue; for other insn patterns verify that we're back to
1239 // the original unwind state.
1240 if (ret_pattern_p() ||
1241 (sp.IsCFAPlusOffset() && sp.GetOffset() == 0 &&
1242 pc.IsAtCFAPlusOffset() && pc.GetOffset() == -m_wordsize)) {
1243 // Reinstate the saved prologue setup for any instructions that come
1244 // after the epilogue
1245
1246 UnwindPlan::Row *newrow = new UnwindPlan::Row;
1247 *newrow = *prologue_completed_row.get();
1248 row.reset(newrow);
1249 current_sp_bytes_offset_from_fa =
1250 prologue_completed_sp_bytes_offset_from_cfa;
1251 is_aligned = prologue_completed_is_aligned;
1252
1253 saved_registers.clear();
1254 saved_registers.resize(prologue_completed_saved_registers.size(), false);
1255 for (size_t i = 0; i < prologue_completed_saved_registers.size(); ++i) {
1256 saved_registers[i] = prologue_completed_saved_registers[i];
1257 }
1258
1259 in_epilogue = true;
1260 row_updated = true;
1261 }
1262 }
1263 }
1264
1265 // call next instruction
1266 // call 0
1267 // => pop %ebx
1268 // This is used in i386 programs to get the PIC base address for finding
1269 // global data
1270 else if (call_next_insn_pattern_p()) {
1271 current_sp_bytes_offset_from_fa += m_wordsize;
1272 if (fa_value_ptr->GetRegisterNumber() == m_lldb_sp_regnum) {
1273 fa_value_ptr->SetOffset(current_sp_bytes_offset_from_fa);
1274 row_updated = true;
1275 }
1276 }
1277
1278 if (row_updated) {
1279 if (current_func_text_offset + insn_len < size) {
1280 row->SetOffset(current_func_text_offset + insn_len);
1281 unwind_plan.AppendRow(row);
1282 // Allocate a new Row, populate it with the existing Row contents.
1283 newrow = new UnwindPlan::Row;
1284 *newrow = *row.get();
1285 row.reset(newrow);
1286 }
1287 }
1288
1289 if (!in_epilogue && row_updated) {
1290 // If we're not in an epilogue sequence, save the updated Row
1291 UnwindPlan::Row *newrow = new UnwindPlan::Row;
1292 *newrow = *row.get();
1293 prologue_completed_row.reset(newrow);
1294
1295 prologue_completed_saved_registers.clear();
1296 prologue_completed_saved_registers.resize(saved_registers.size(), false);
1297 for (size_t i = 0; i < saved_registers.size(); ++i) {
1298 prologue_completed_saved_registers[i] = saved_registers[i];
1299 }
1300 }
1301
1302 // We may change the sp value without adding a new Row necessarily -- keep
1303 // track of it either way.
1304 if (!in_epilogue) {
1305 prologue_completed_sp_bytes_offset_from_cfa =
1306 current_sp_bytes_offset_from_fa;
1307 prologue_completed_is_aligned = is_aligned;
1308 }
1309
1310 m_cur_insn = m_cur_insn + insn_len;
1311 current_func_text_offset += insn_len;
1312 }
1313
1314 unwind_plan.SetSourceName("assembly insn profiling");
1315 unwind_plan.SetSourcedFromCompiler(eLazyBoolNo);
1316 unwind_plan.SetUnwindPlanValidAtAllInstructions(eLazyBoolYes);
1317 unwind_plan.SetUnwindPlanForSignalTrap(eLazyBoolNo);
1318
1319 return true;
1320}
1321
1322bool x86AssemblyInspectionEngine::AugmentUnwindPlanFromCallSite(
1323 uint8_t *data, size_t size, AddressRange &func_range,
1324 UnwindPlan &unwind_plan, RegisterContextSP &reg_ctx) {
1325 Address addr_start = func_range.GetBaseAddress();
1326 if (!addr_start.IsValid())
1327 return false;
1328
1329 // We either need a live RegisterContext, or we need the UnwindPlan to
1330 // already be in the lldb register numbering scheme.
1331 if (reg_ctx.get() == nullptr &&
1332 unwind_plan.GetRegisterKind() != eRegisterKindLLDB)
1333 return false;
1334
1335 // Is original unwind_plan valid?
1336 // unwind_plan should have at least one row which is ABI-default (CFA
1337 // register is sp), and another row in mid-function.
1338 if (unwind_plan.GetRowCount() < 2)
1339 return false;
1340
1341 UnwindPlan::RowSP first_row = unwind_plan.GetRowAtIndex(0);
1342 if (first_row->GetOffset() != 0)
1343 return false;
1344 uint32_t cfa_reg = first_row->GetCFAValue().GetRegisterNumber();
1345 if (unwind_plan.GetRegisterKind() != eRegisterKindLLDB) {
1346 cfa_reg = reg_ctx->ConvertRegisterKindToRegisterNumber(
1347 unwind_plan.GetRegisterKind(),
1348 first_row->GetCFAValue().GetRegisterNumber());
1349 }
1350 if (cfa_reg != m_lldb_sp_regnum ||
1351 first_row->GetCFAValue().GetOffset() != m_wordsize)
1352 return false;
1353
1354 UnwindPlan::RowSP original_last_row = unwind_plan.GetRowForFunctionOffset(-1);
1355
1356 size_t offset = 0;
1357 int row_id = 1;
1358 bool unwind_plan_updated = false;
1359 UnwindPlan::RowSP row(new UnwindPlan::Row(*first_row));
1360
1361 // After a mid-function epilogue we will need to re-insert the original
1362 // unwind rules so unwinds work for the remainder of the function. These
1363 // aren't common with clang/gcc on x86 but it is possible.
1364 bool reinstate_unwind_state = false;
1365
1366 while (offset < size) {
1367 m_cur_insn = data + offset;
1368 int insn_len;
1369 if (!instruction_length(m_cur_insn, insn_len, size - offset) ||
1370 insn_len == 0 || insn_len > kMaxInstructionByteSize) {
1371 // An unrecognized/junk instruction.
1372 break;
1373 }
1374
1375 // Advance offsets.
1376 offset += insn_len;
1377
1378 // offset is pointing beyond the bounds of the function; stop looping.
1379 if (offset >= size)
1380 continue;
1381
1382 if (reinstate_unwind_state) {
1383 UnwindPlan::RowSP new_row(new UnwindPlan::Row());
1384 *new_row = *original_last_row;
1385 new_row->SetOffset(offset);
1386 unwind_plan.AppendRow(new_row);
1387 row = std::make_shared<UnwindPlan::Row>();
1388 *row = *new_row;
1389 reinstate_unwind_state = false;
1390 unwind_plan_updated = true;
1391 continue;
1392 }
1393
1394 // If we already have one row for this instruction, we can continue.
1395 while (row_id < unwind_plan.GetRowCount() &&
1396 unwind_plan.GetRowAtIndex(row_id)->GetOffset() <= offset) {
1397 row_id++;
1398 }
1399 UnwindPlan::RowSP original_row = unwind_plan.GetRowAtIndex(row_id - 1);
1400 if (original_row->GetOffset() == offset) {
1401 *row = *original_row;
1402 continue;
1403 }
1404
1405 if (row_id == 0) {
1406 // If we are here, compiler didn't generate CFI for prologue. This won't
1407 // happen to GCC or clang. In this case, bail out directly.
1408 return false;
1409 }
1410
1411 // Inspect the instruction to check if we need a new row for it.
1412 cfa_reg = row->GetCFAValue().GetRegisterNumber();
1413 if (unwind_plan.GetRegisterKind() != eRegisterKindLLDB) {
1414 cfa_reg = reg_ctx->ConvertRegisterKindToRegisterNumber(
1415 unwind_plan.GetRegisterKind(),
1416 row->GetCFAValue().GetRegisterNumber());
1417 }
1418 if (cfa_reg == m_lldb_sp_regnum) {
1419 // CFA register is sp.
1420
1421 // call next instruction
1422 // call 0
1423 // => pop %ebx
1424 if (call_next_insn_pattern_p()) {
1425 row->SetOffset(offset);
1426 row->GetCFAValue().IncOffset(m_wordsize);
1427
1428 UnwindPlan::RowSP new_row(new UnwindPlan::Row(*row));
1429 unwind_plan.InsertRow(new_row);
1430 unwind_plan_updated = true;
1431 continue;
1432 }
1433
1434 // push/pop register
1435 int regno;
1436 if (push_reg_p(regno)) {
1437 row->SetOffset(offset);
1438 row->GetCFAValue().IncOffset(m_wordsize);
1439
1440 UnwindPlan::RowSP new_row(new UnwindPlan::Row(*row));
1441 unwind_plan.InsertRow(new_row);
1442 unwind_plan_updated = true;
1443 continue;
1444 }
1445 if (pop_reg_p(regno)) {
1446 // Technically, this might be a nonvolatile register recover in
1447 // epilogue. We should reset RegisterInfo for the register. But in
1448 // practice, previous rule for the register is still valid... So we
1449 // ignore this case.
1450
1451 row->SetOffset(offset);
1452 row->GetCFAValue().IncOffset(-m_wordsize);
1453
1454 UnwindPlan::RowSP new_row(new UnwindPlan::Row(*row));
1455 unwind_plan.InsertRow(new_row);
1456 unwind_plan_updated = true;
1457 continue;
1458 }
1459
1460 if (pop_misc_reg_p()) {
1461 row->SetOffset(offset);
1462 row->GetCFAValue().IncOffset(-m_wordsize);
1463
1464 UnwindPlan::RowSP new_row(new UnwindPlan::Row(*row));
1465 unwind_plan.InsertRow(new_row);
1466 unwind_plan_updated = true;
1467 continue;
1468 }
1469
1470 // push imm
1471 if (push_imm_pattern_p()) {
1472 row->SetOffset(offset);
1473 row->GetCFAValue().IncOffset(m_wordsize);
1474 UnwindPlan::RowSP new_row(new UnwindPlan::Row(*row));
1475 unwind_plan.InsertRow(new_row);
1476 unwind_plan_updated = true;
1477 continue;
1478 }
1479
1480 // push extended
1481 if (push_extended_pattern_p() || push_misc_reg_p()) {
1482 row->SetOffset(offset);
1483 row->GetCFAValue().IncOffset(m_wordsize);
1484 UnwindPlan::RowSP new_row(new UnwindPlan::Row(*row));
1485 unwind_plan.InsertRow(new_row);
1486 unwind_plan_updated = true;
1487 continue;
1488 }
1489
1490 // add/sub %rsp/%esp
1491 int amount;
1492 if (add_rsp_pattern_p(amount)) {
1493 row->SetOffset(offset);
1494 row->GetCFAValue().IncOffset(-amount);
1495
1496 UnwindPlan::RowSP new_row(new UnwindPlan::Row(*row));
1497 unwind_plan.InsertRow(new_row);
1498 unwind_plan_updated = true;
1499 continue;
1500 }
1501 if (sub_rsp_pattern_p(amount)) {
1502 row->SetOffset(offset);
1503 row->GetCFAValue().IncOffset(amount);
1504
1505 UnwindPlan::RowSP new_row(new UnwindPlan::Row(*row));
1506 unwind_plan.InsertRow(new_row);
1507 unwind_plan_updated = true;
1508 continue;
1509 }
1510
1511 // lea %rsp, [%rsp + $offset]
1512 if (lea_rsp_pattern_p(amount)) {
1513 row->SetOffset(offset);
1514 row->GetCFAValue().IncOffset(-amount);
1515
1516 UnwindPlan::RowSP new_row(new UnwindPlan::Row(*row));
1517 unwind_plan.InsertRow(new_row);
1518 unwind_plan_updated = true;
1519 continue;
1520 }
1521
1522 if (ret_pattern_p()) {
1523 reinstate_unwind_state = true;
1524 continue;
1525 }
1526 } else if (cfa_reg == m_lldb_fp_regnum) {
1527 // CFA register is fp.
1528
1529 // The only case we care about is epilogue:
1530 // [0x5d] pop %rbp/%ebp
1531 // => [0xc3] ret
1532 if (pop_rbp_pattern_p() || leave_pattern_p()) {
1533 m_cur_insn++;
1534 if (ret_pattern_p()) {
1535 row->SetOffset(offset);
1536 row->GetCFAValue().SetIsRegisterPlusOffset(
1537 first_row->GetCFAValue().GetRegisterNumber(), m_wordsize);
1538
1539 UnwindPlan::RowSP new_row(new UnwindPlan::Row(*row));
1540 unwind_plan.InsertRow(new_row);
1541 unwind_plan_updated = true;
1542 reinstate_unwind_state = true;
1543 continue;
1544 }
1545 }
1546 } else {
1547 // CFA register is not sp or fp.
1548
1549 // This must be hand-written assembly.
1550 // Just trust eh_frame and assume we have finished.
1551 break;
1552 }
1553 }
1554
1555 unwind_plan.SetPlanValidAddressRange(func_range);
1556 if (unwind_plan_updated) {
1557 std::string unwind_plan_source(unwind_plan.GetSourceName().AsCString());
1558 unwind_plan_source += " plus augmentation from assembly parsing";
1559 unwind_plan.SetSourceName(unwind_plan_source.c_str());
1560 unwind_plan.SetSourcedFromCompiler(eLazyBoolNo);
1561 unwind_plan.SetUnwindPlanValidAtAllInstructions(eLazyBoolYes);
1562 }
1563 return true;
1564}
1565
1566bool x86AssemblyInspectionEngine::FindFirstNonPrologueInstruction(
1567 uint8_t *data, size_t size, size_t &offset) {
1568 offset = 0;
1569
1570 if (!m_register_map_initialized)
1571 return false;
1572
1573 while (offset < size) {
1574 int regno;
1575 int insn_len;
1576 int scratch;
1577
1578 m_cur_insn = data + offset;
1579 if (!instruction_length(m_cur_insn, insn_len, size - offset)
1580 || insn_len > kMaxInstructionByteSize
1581 || insn_len == 0) {
1582 // An error parsing the instruction, i.e. probably data/garbage - stop
1583 // scanning
1584 break;
1585 }
1586
1587 if (push_rbp_pattern_p() || mov_rsp_rbp_pattern_p() ||
1588 sub_rsp_pattern_p(scratch) || push_reg_p(regno) ||
1589 mov_reg_to_local_stack_frame_p(regno, scratch) ||
1590 (lea_rsp_pattern_p(scratch) && offset == 0)) {
1591 offset += insn_len;
1592 continue;
1593 }
1594 //
1595 // Unknown non-prologue instruction - stop scanning
1596 break;
1597 }
1598
1599 return true;
1600}