Bug Summary

File:build/source/lldb/source/Plugins/Process/Utility/NativeRegisterContextDBReg_x86.cpp
Warning:line 120, column 16
Branch condition evaluates to a garbage value

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 NativeRegisterContextDBReg_x86.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/source/build-llvm/tools/clang/stage2-bins -resource-dir /usr/lib/llvm-17/lib/clang/17 -isystem /usr/include/libxml2 -D HAVE_ROUND -D _DEBUG -D _GLIBCXX_ASSERTIONS -D _GNU_SOURCE -D _LIBCPP_ENABLE_ASSERTIONS -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I tools/lldb/source/Plugins/Process/Utility -I /build/source/lldb/source/Plugins/Process/Utility -I /build/source/lldb/include -I tools/lldb/include -I include -I /build/source/llvm/include -I /usr/include/python3.9 -I /build/source/clang/include -I tools/lldb/../clang/include -I /build/source/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-17/lib/clang/17/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/source/build-llvm/tools/clang/stage2-bins=build-llvm/tools/clang/stage2-bins -fmacro-prefix-map=/build/source/= -fcoverage-prefix-map=/build/source/build-llvm/tools/clang/stage2-bins=build-llvm/tools/clang/stage2-bins -fcoverage-prefix-map=/build/source/= -source-date-epoch 1683717183 -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/source/build-llvm/tools/clang/stage2-bins -fdebug-prefix-map=/build/source/build-llvm/tools/clang/stage2-bins=build-llvm/tools/clang/stage2-bins -fdebug-prefix-map=/build/source/= -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-2023-05-10-133810-16478-1 -x c++ /build/source/lldb/source/Plugins/Process/Utility/NativeRegisterContextDBReg_x86.cpp
1//===-- NativeRegisterContextDBReg_x86.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 "NativeRegisterContextDBReg_x86.h"
10#include "lldb/Utility/LLDBLog.h"
11#include "lldb/Utility/RegisterValue.h"
12
13#include "Plugins/Process/Utility/lldb-x86-register-enums.h"
14
15using namespace lldb_private;
16
17// Returns mask/value for status bit of wp_index in DR6
18static inline uint64_t GetStatusBit(uint32_t wp_index) {
19 // DR6: ...BBBB
20 // 3210 <- status bits for bp./wp. i; 1 if hit
21 return 1ULL << wp_index;
22}
23
24// Returns mask/value for global enable bit of wp_index in DR7
25static inline uint64_t GetEnableBit(uint32_t wp_index) {
26 // DR7: ...GLGLGLGL
27 // 33221100 <- global/local enable for bp./wp.; 1 if enabled
28 // we use global bits because NetBSD kernel does not preserve local
29 // bits reliably; Linux seems fine with either
30 return 1ULL << (2 * wp_index + 1);
31}
32
33// Returns mask for both enable bits of wp_index in DR7
34static inline uint64_t GetBothEnableBitMask(uint32_t wp_index) {
35 // DR7: ...GLGLGLGL
36 // 33221100 <- global/local enable for bp./wp.; 1 if enabled
37 return 3ULL << (2 * wp_index + 1);
38}
39
40// Returns value for type bits of wp_index in DR7
41static inline uint64_t GetWatchTypeBits(uint32_t watch_flags,
42 uint32_t wp_index) {
43 // DR7:
44 // bit: 3322222222221111...
45 // 1098765432109876...
46 // val: SSTTSSTTSSTTSSTT...
47 // wp.: 3333222211110000...
48 //
49 // where T - type is 01 for write, 11 for r/w
50 return static_cast<uint64_t>(watch_flags) << (16 + 4 * wp_index);
51}
52
53// Returns value for size bits of wp_index in DR7
54static inline uint64_t GetWatchSizeBits(uint32_t size, uint32_t wp_index) {
55 // DR7:
56 // bit: 3322222222221111...
57 // 1098765432109876...
58 // val: SSTTSSTTSSTTSSTT...
59 // wp.: 3333222211110000...
60 //
61 // where S - size is:
62 // 00 for 1 byte
63 // 01 for 2 bytes
64 // 10 for 8 bytes
65 // 11 for 4 bytes
66 return static_cast<uint64_t>(size == 8 ? 0x2 : size - 1)
67 << (18 + 4 * wp_index);
68}
69
70// Returns bitmask for all bits controlling wp_index in DR7
71static inline uint64_t GetWatchControlBitmask(uint32_t wp_index) {
72 // DR7:
73 // bit: 33222222222211111111110000000000
74 // 10987654321098765432109876543210
75 // val: SSTTSSTTSSTTSSTTxxxxxxGLGLGLGLGL
76 // wp.: 3333222211110000xxxxxxEE33221100
77 return GetBothEnableBitMask(wp_index) | (0xF << (16 + 4 * wp_index));
78}
79
80// Bit mask for control bits regarding all watchpoints.
81static constexpr uint64_t watchpoint_all_control_bit_mask = 0xFFFF00FF;
82
83const RegisterInfo *NativeRegisterContextDBReg_x86::GetDR(int num) const {
84 assert(num >= 0 && num <= 7)(static_cast <bool> (num >= 0 && num <= 7
) ? void (0) : __assert_fail ("num >= 0 && num <= 7"
, "lldb/source/Plugins/Process/Utility/NativeRegisterContextDBReg_x86.cpp"
, 84, __extension__ __PRETTY_FUNCTION__));
85 switch (GetRegisterInfoInterface().GetTargetArchitecture().GetMachine()) {
86 case llvm::Triple::x86:
87 return GetRegisterInfoAtIndex(lldb_dr0_i386 + num);
88 case llvm::Triple::x86_64:
89 return GetRegisterInfoAtIndex(lldb_dr0_x86_64 + num);
90 default:
91 llvm_unreachable("Unhandled target architecture.")::llvm::llvm_unreachable_internal("Unhandled target architecture."
, "lldb/source/Plugins/Process/Utility/NativeRegisterContextDBReg_x86.cpp"
, 91);
92 }
93}
94
95Status NativeRegisterContextDBReg_x86::IsWatchpointHit(uint32_t wp_index,
96 bool &is_hit) {
97 if (wp_index >= NumSupportedHardwareWatchpoints())
4
←
Assuming the condition is true
→
5
←
Taking true branch
→
98 return Status("Watchpoint index out of range");
6
←
Returning without writing to 'is_hit', which participates in a condition later
→
7
←
Returning without writing to 'is_hit'
→
99
100 RegisterValue dr6;
101 Status error = ReadRegister(GetDR(6), dr6);
102 if (error.Fail())
103 is_hit = false;
104 else
105 is_hit = dr6.GetAsUInt64() & GetStatusBit(wp_index);
106
107 return error;
108}
109
110Status
111NativeRegisterContextDBReg_x86::GetWatchpointHitIndex(uint32_t &wp_index,
112 lldb::addr_t trap_addr) {
113 uint32_t num_hw_wps = NumSupportedHardwareWatchpoints();
114 for (wp_index = 0; wp_index < num_hw_wps; ++wp_index) {
1
Loop condition is true. Entering loop body
→
115 bool is_hit;
2
←
'is_hit' declared without an initial value
→
116 Status error = IsWatchpointHit(wp_index, is_hit);
3
←
Calling 'NativeRegisterContextDBReg_x86::IsWatchpointHit'
→
8
←
Returning from 'NativeRegisterContextDBReg_x86::IsWatchpointHit'
→
117 if (error.Fail()) {
9
←
Assuming the condition is false
→
10
←
Taking false branch
→
118 wp_index = LLDB_INVALID_INDEX32(4294967295U);
119 return error;
120 } else if (is_hit) {
11
←
Branch condition evaluates to a garbage value
121 return error;
122 }
123 }
124 wp_index = LLDB_INVALID_INDEX32(4294967295U);
125 return Status();
126}
127
128Status NativeRegisterContextDBReg_x86::IsWatchpointVacant(uint32_t wp_index,
129 bool &is_vacant) {
130 if (wp_index >= NumSupportedHardwareWatchpoints())
131 return Status("Watchpoint index out of range");
132
133 RegisterValue dr7;
134 Status error = ReadRegister(GetDR(7), dr7);
135 if (error.Fail())
136 is_vacant = false;
137 else
138 is_vacant = !(dr7.GetAsUInt64() & GetEnableBit(wp_index));
139
140 return error;
141}
142
143Status NativeRegisterContextDBReg_x86::SetHardwareWatchpointWithIndex(
144 lldb::addr_t addr, size_t size, uint32_t watch_flags, uint32_t wp_index) {
145
146 if (wp_index >= NumSupportedHardwareWatchpoints())
147 return Status("Watchpoint index out of range");
148
149 // Read only watchpoints aren't supported on x86_64. Fall back to read/write
150 // waitchpoints instead.
151 // TODO: Add logic to detect when a write happens and ignore that watchpoint
152 // hit.
153 if (watch_flags == 2)
154 watch_flags = 3;
155
156 if (watch_flags != 1 && watch_flags != 3)
157 return Status("Invalid read/write bits for watchpoint");
158 if (size != 1 && size != 2 && size != 4 && size != 8)
159 return Status("Invalid size for watchpoint");
160
161 bool is_vacant;
162 Status error = IsWatchpointVacant(wp_index, is_vacant);
163 if (error.Fail())
164 return error;
165 if (!is_vacant)
166 return Status("Watchpoint index not vacant");
167
168 RegisterValue dr7, drN;
169 error = ReadRegister(GetDR(7), dr7);
170 if (error.Fail())
171 return error;
172 error = ReadRegister(GetDR(wp_index), drN);
173 if (error.Fail())
174 return error;
175
176 uint64_t control_bits = dr7.GetAsUInt64() & ~GetWatchControlBitmask(wp_index);
177 control_bits |= GetEnableBit(wp_index) |
178 GetWatchTypeBits(watch_flags, wp_index) |
179 GetWatchSizeBits(size, wp_index);
180
181 // Clear dr6 if address or bits changed (i.e. we're not reenabling the same
182 // watchpoint). This can not be done when clearing watchpoints since
183 // the gdb-remote protocol repeatedly clears and readds watchpoints on all
184 // program threads, effectively clearing pending events on NetBSD.
185 // NB: enable bits in dr7 are always 0 here since we're (re)adding it
186 if (drN.GetAsUInt64() != addr ||
187 (dr7.GetAsUInt64() & GetWatchControlBitmask(wp_index)) !=
188 (GetWatchTypeBits(watch_flags, wp_index) |
189 GetWatchSizeBits(size, wp_index))) {
190 ClearWatchpointHit(wp_index);
191
192 // We skip update to drN if neither address nor mode changed.
193 error = WriteRegister(GetDR(wp_index), RegisterValue(addr));
194 if (error.Fail())
195 return error;
196 }
197
198 error = WriteRegister(GetDR(7), RegisterValue(control_bits));
199 if (error.Fail())
200 return error;
201
202 return error;
203}
204
205bool NativeRegisterContextDBReg_x86::ClearHardwareWatchpoint(
206 uint32_t wp_index) {
207 if (wp_index >= NumSupportedHardwareWatchpoints())
208 return false;
209
210 RegisterValue dr7;
211 Status error = ReadRegister(GetDR(7), dr7);
212 if (error.Fail())
213 return false;
214
215 return WriteRegister(GetDR(7), RegisterValue(dr7.GetAsUInt64() &
216 ~GetBothEnableBitMask(wp_index)))
217 .Success();
218}
219
220Status NativeRegisterContextDBReg_x86::ClearWatchpointHit(uint32_t wp_index) {
221 if (wp_index >= NumSupportedHardwareWatchpoints())
222 return Status("Watchpoint index out of range");
223
224 RegisterValue dr6;
225 Status error = ReadRegister(GetDR(6), dr6);
226 if (error.Fail())
227 return error;
228
229 return WriteRegister(
230 GetDR(6), RegisterValue(dr6.GetAsUInt64() & ~GetStatusBit(wp_index)));
231}
232
233Status NativeRegisterContextDBReg_x86::ClearAllHardwareWatchpoints() {
234 RegisterValue dr7;
235 Status error = ReadRegister(GetDR(7), dr7);
236 if (error.Fail())
237 return error;
238 return WriteRegister(
239 GetDR(7),
240 RegisterValue(dr7.GetAsUInt64() & ~watchpoint_all_control_bit_mask));
241}
242
243uint32_t NativeRegisterContextDBReg_x86::SetHardwareWatchpoint(
244 lldb::addr_t addr, size_t size, uint32_t watch_flags) {
245 Log *log = GetLog(LLDBLog::Watchpoints);
246 const uint32_t num_hw_watchpoints = NumSupportedHardwareWatchpoints();
247 for (uint32_t wp_index = 0; wp_index < num_hw_watchpoints; ++wp_index) {
248 bool is_vacant;
249 Status error = IsWatchpointVacant(wp_index, is_vacant);
250 if (is_vacant) {
251 error = SetHardwareWatchpointWithIndex(addr, size, watch_flags, wp_index);
252 if (error.Success())
253 return wp_index;
254 }
255 if (error.Fail() && log) {
256 LLDB_LOGF(log, "NativeRegisterContextDBReg_x86::%s Error: %s",do { ::lldb_private::Log *log_private = (log); if (log_private
) log_private->Printf("NativeRegisterContextDBReg_x86::%s Error: %s"
, __FUNCTION__, error.AsCString()); } while (0)
257 __FUNCTION__, error.AsCString())do { ::lldb_private::Log *log_private = (log); if (log_private
) log_private->Printf("NativeRegisterContextDBReg_x86::%s Error: %s"
, __FUNCTION__, error.AsCString()); } while (0);
258 }
259 }
260 return LLDB_INVALID_INDEX32(4294967295U);
261}
262
263lldb::addr_t
264NativeRegisterContextDBReg_x86::GetWatchpointAddress(uint32_t wp_index) {
265 if (wp_index >= NumSupportedHardwareWatchpoints())
266 return LLDB_INVALID_ADDRESS(18446744073709551615UL);
267 RegisterValue drN;
268 if (ReadRegister(GetDR(wp_index), drN).Fail())
269 return LLDB_INVALID_ADDRESS(18446744073709551615UL);
270 return drN.GetAsUInt64();
271}
272
273uint32_t NativeRegisterContextDBReg_x86::NumSupportedHardwareWatchpoints() {
274 // Available debug address registers: dr0, dr1, dr2, dr3
275 return 4;
276}