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
11 #include "lldb/Utility/Log.h"
12 #include "lldb/Utility/RegisterValue.h"
13
14 #include "Plugins/Process/Utility/lldb-x86-register-enums.h"
15
16 using namespace lldb_private;
17
18 // Returns mask/value for status bit of wp_index in DR6
GetStatusBit(uint32_t wp_index)19 static inline uint64_t GetStatusBit(uint32_t wp_index) {
20 // DR6: ...BBBB
21 // 3210 <- status bits for bp./wp. i; 1 if hit
22 return 1 << wp_index;
23 }
24
25 // Returns mask/value for global enable bit of wp_index in DR7
GetEnableBit(uint32_t wp_index)26 static inline uint64_t GetEnableBit(uint32_t wp_index) {
27 // DR7: ...GLGLGLGL
28 // 33221100 <- global/local enable for bp./wp.; 1 if enabled
29 // we use global bits because NetBSD kernel does not preserve local
30 // bits reliably; Linux seems fine with either
31 return 1 << (2 * wp_index + 1);
32 }
33
34 // Returns mask for both enable bits of wp_index in DR7
GetBothEnableBitMask(uint32_t wp_index)35 static inline uint64_t GetBothEnableBitMask(uint32_t wp_index) {
36 // DR7: ...GLGLGLGL
37 // 33221100 <- global/local enable for bp./wp.; 1 if enabled
38 return 3 << (2 * wp_index + 1);
39 }
40
41 // Returns value for type bits of wp_index in DR7
GetWatchTypeBits(uint32_t watch_flags,uint32_t wp_index)42 static inline uint64_t GetWatchTypeBits(uint32_t watch_flags,
43 uint32_t wp_index) {
44 // DR7:
45 // bit: 3322222222221111...
46 // 1098765432109876...
47 // val: SSTTSSTTSSTTSSTT...
48 // wp.: 3333222211110000...
49 //
50 // where T - type is 01 for write, 11 for r/w
51 return watch_flags << (16 + 4 * wp_index);
52 }
53
54 // Returns value for size bits of wp_index in DR7
GetWatchSizeBits(uint32_t size,uint32_t wp_index)55 static inline uint64_t GetWatchSizeBits(uint32_t size, uint32_t wp_index) {
56 // DR7:
57 // bit: 3322222222221111...
58 // 1098765432109876...
59 // val: SSTTSSTTSSTTSSTT...
60 // wp.: 3333222211110000...
61 //
62 // where S - size is:
63 // 00 for 1 byte
64 // 01 for 2 bytes
65 // 10 for 8 bytes
66 // 11 for 4 bytes
67 return (size == 8 ? 0x2 : size - 1) << (18 + 4 * wp_index);
68 }
69
70 // Returns bitmask for all bits controlling wp_index in DR7
GetWatchControlBitmask(uint32_t wp_index)71 static 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.
81 static constexpr uint64_t watchpoint_all_control_bit_mask = 0xFFFF00FF;
82
GetDR(int num) const83 const RegisterInfo *NativeRegisterContextDBReg_x86::GetDR(int num) const {
84 assert(num >= 0 && num <= 7);
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.");
92 }
93 }
94
IsWatchpointHit(uint32_t wp_index,bool & is_hit)95 Status NativeRegisterContextDBReg_x86::IsWatchpointHit(uint32_t wp_index,
96 bool &is_hit) {
97 if (wp_index >= NumSupportedHardwareWatchpoints())
98 return Status("Watchpoint index out of range");
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
110 Status
GetWatchpointHitIndex(uint32_t & wp_index,lldb::addr_t trap_addr)111 NativeRegisterContextDBReg_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) {
115 bool is_hit;
116 Status error = IsWatchpointHit(wp_index, is_hit);
117 if (error.Fail()) {
118 wp_index = LLDB_INVALID_INDEX32;
119 return error;
120 } else if (is_hit) {
121 return error;
122 }
123 }
124 wp_index = LLDB_INVALID_INDEX32;
125 return Status();
126 }
127
IsWatchpointVacant(uint32_t wp_index,bool & is_vacant)128 Status 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
SetHardwareWatchpointWithIndex(lldb::addr_t addr,size_t size,uint32_t watch_flags,uint32_t wp_index)143 Status 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
ClearHardwareWatchpoint(uint32_t wp_index)205 bool 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
ClearWatchpointHit(uint32_t wp_index)220 Status 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
ClearAllHardwareWatchpoints()233 Status 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
SetHardwareWatchpoint(lldb::addr_t addr,size_t size,uint32_t watch_flags)243 uint32_t NativeRegisterContextDBReg_x86::SetHardwareWatchpoint(
244 lldb::addr_t addr, size_t size, uint32_t watch_flags) {
245 Log *log(GetLogIfAllCategoriesSet(LIBLLDB_LOG_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",
257 __FUNCTION__, error.AsCString());
258 }
259 }
260 return LLDB_INVALID_INDEX32;
261 }
262
263 lldb::addr_t
GetWatchpointAddress(uint32_t wp_index)264 NativeRegisterContextDBReg_x86::GetWatchpointAddress(uint32_t wp_index) {
265 if (wp_index >= NumSupportedHardwareWatchpoints())
266 return LLDB_INVALID_ADDRESS;
267 RegisterValue drN;
268 if (ReadRegister(GetDR(wp_index), drN).Fail())
269 return LLDB_INVALID_ADDRESS;
270 return drN.GetAsUInt64();
271 }
272
NumSupportedHardwareWatchpoints()273 uint32_t NativeRegisterContextDBReg_x86::NumSupportedHardwareWatchpoints() {
274 // Available debug address registers: dr0, dr1, dr2, dr3
275 return 4;
276 }
277