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1 //===-- sanitizer_stacktrace.cc -------------------------------------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file is shared between AddressSanitizer and ThreadSanitizer
11 // run-time libraries.
12 //===----------------------------------------------------------------------===//
13 
14 #include "sanitizer_common.h"
15 #include "sanitizer_procmaps.h"
16 #include "sanitizer_stacktrace.h"
17 #include "sanitizer_symbolizer.h"
18 
19 namespace __sanitizer {
StripPathPrefix(const char * filepath,const char * strip_file_prefix)20 const char *StripPathPrefix(const char *filepath,
21                             const char *strip_file_prefix) {
22   if (filepath == 0) return 0;
23   const char *prefix_beg = internal_strstr(filepath, strip_file_prefix);
24   if (prefix_beg)
25     return prefix_beg + internal_strlen(strip_file_prefix);
26   return filepath;
27 }
28 
29 // ----------------------- StackTrace ----------------------------- {{{1
GetPreviousInstructionPc(uptr pc)30 uptr StackTrace::GetPreviousInstructionPc(uptr pc) {
31 #ifdef __arm__
32   // Cancel Thumb bit.
33   pc = pc & (~1);
34 #endif
35 #if defined(__powerpc__) || defined(__powerpc64__)
36   // PCs are always 4 byte aligned.
37   return pc - 4;
38 #elif defined(__sparc__)
39   return pc - 8;
40 #else
41   return pc - 1;
42 #endif
43 }
44 
PrintStackFramePrefix(uptr frame_num,uptr pc)45 static void PrintStackFramePrefix(uptr frame_num, uptr pc) {
46   Printf("    #%zu 0x%zx", frame_num, pc);
47 }
48 
PrintSourceLocation(const char * file,int line,int column,const char * strip_file_prefix)49 static void PrintSourceLocation(const char *file, int line, int column,
50                                 const char *strip_file_prefix) {
51   CHECK(file);
52   Printf(" %s", StripPathPrefix(file, strip_file_prefix));
53   if (line > 0) {
54     Printf(":%d", line);
55     if (column > 0)
56       Printf(":%d", column);
57   }
58 }
59 
PrintModuleAndOffset(const char * module,uptr offset,const char * strip_file_prefix)60 static void PrintModuleAndOffset(const char *module, uptr offset,
61                                  const char *strip_file_prefix) {
62   Printf(" (%s+0x%zx)", StripPathPrefix(module, strip_file_prefix), offset);
63 }
64 
PrintStack(const uptr * addr,uptr size,bool symbolize,const char * strip_file_prefix,SymbolizeCallback symbolize_callback)65 void StackTrace::PrintStack(const uptr *addr, uptr size,
66                             bool symbolize, const char *strip_file_prefix,
67                             SymbolizeCallback symbolize_callback ) {
68   MemoryMappingLayout proc_maps(/*cache_enabled*/true);
69   InternalScopedBuffer<char> buff(GetPageSizeCached() * 2);
70   InternalScopedBuffer<AddressInfo> addr_frames(64);
71   uptr frame_num = 0;
72   for (uptr i = 0; i < size && addr[i]; i++) {
73     // PCs in stack traces are actually the return addresses, that is,
74     // addresses of the next instructions after the call.
75     uptr pc = GetPreviousInstructionPc(addr[i]);
76     uptr addr_frames_num = 0;  // The number of stack frames for current
77                                // instruction address.
78     if (symbolize_callback) {
79       if (symbolize_callback((void*)pc, buff.data(), buff.size())) {
80         addr_frames_num = 1;
81         PrintStackFramePrefix(frame_num, pc);
82         // We can't know anything about the string returned by external
83         // symbolizer, but if it starts with filename, try to strip path prefix
84         // from it.
85         Printf(" %s\n", StripPathPrefix(buff.data(), strip_file_prefix));
86         frame_num++;
87       }
88     }
89     if (symbolize && addr_frames_num == 0 && &SymbolizeCode) {
90       // Use our own (online) symbolizer, if necessary.
91       addr_frames_num = SymbolizeCode(pc, addr_frames.data(),
92                                       addr_frames.size());
93       for (uptr j = 0; j < addr_frames_num; j++) {
94         AddressInfo &info = addr_frames[j];
95         PrintStackFramePrefix(frame_num, pc);
96         if (info.function) {
97           Printf(" in %s", info.function);
98         }
99         if (info.file) {
100           PrintSourceLocation(info.file, info.line, info.column,
101                               strip_file_prefix);
102         } else if (info.module) {
103           PrintModuleAndOffset(info.module, info.module_offset,
104                                strip_file_prefix);
105         }
106         Printf("\n");
107         info.Clear();
108         frame_num++;
109       }
110     }
111     if (addr_frames_num == 0) {
112       // If online symbolization failed, try to output at least module and
113       // offset for instruction.
114       PrintStackFramePrefix(frame_num, pc);
115       uptr offset;
116       if (proc_maps.GetObjectNameAndOffset(pc, &offset,
117                                            buff.data(), buff.size(),
118                                            /* protection */0)) {
119         PrintModuleAndOffset(buff.data(), offset, strip_file_prefix);
120       }
121       Printf("\n");
122       frame_num++;
123     }
124   }
125 }
126 
GetCurrentPc()127 uptr StackTrace::GetCurrentPc() {
128   return GET_CALLER_PC();
129 }
130 
FastUnwindStack(uptr pc,uptr bp,uptr stack_top,uptr stack_bottom)131 void StackTrace::FastUnwindStack(uptr pc, uptr bp,
132                                  uptr stack_top, uptr stack_bottom) {
133   CHECK(size == 0 && trace[0] == pc);
134   size = 1;
135   uhwptr *frame = (uhwptr *)bp;
136   uhwptr *prev_frame = frame - 1;
137   if (stack_top < 4096) return;  // Sanity check for stack top.
138   // Avoid infinite loop when frame == frame[0] by using frame > prev_frame.
139   while (frame > prev_frame &&
140          frame < (uhwptr *)stack_top - 2 &&
141          frame > (uhwptr *)stack_bottom &&
142          IsAligned((uptr)frame, sizeof(*frame)) &&
143          size < max_size) {
144     uhwptr pc1 = frame[1];
145     if (pc1 != pc) {
146       trace[size++] = (uptr) pc1;
147     }
148     prev_frame = frame;
149     frame = (uhwptr *)frame[0];
150   }
151 }
152 
PopStackFrames(uptr count)153 void StackTrace::PopStackFrames(uptr count) {
154   CHECK(size >= count);
155   size -= count;
156   for (uptr i = 0; i < size; i++) {
157     trace[i] = trace[i + count];
158   }
159 }
160 
161 // On 32-bits we don't compress stack traces.
162 // On 64-bits we compress stack traces: if a given pc differes slightly from
163 // the previous one, we record a 31-bit offset instead of the full pc.
164 SANITIZER_INTERFACE_ATTRIBUTE
CompressStack(StackTrace * stack,u32 * compressed,uptr size)165 uptr StackTrace::CompressStack(StackTrace *stack, u32 *compressed, uptr size) {
166 #if SANITIZER_WORDSIZE == 32
167   // Don't compress, just copy.
168   uptr res = 0;
169   for (uptr i = 0; i < stack->size && i < size; i++) {
170     compressed[i] = stack->trace[i];
171     res++;
172   }
173   if (stack->size < size)
174     compressed[stack->size] = 0;
175 #else  // 64 bits, compress.
176   uptr prev_pc = 0;
177   const uptr kMaxOffset = (1ULL << 30) - 1;
178   uptr c_index = 0;
179   uptr res = 0;
180   for (uptr i = 0, n = stack->size; i < n; i++) {
181     uptr pc = stack->trace[i];
182     if (!pc) break;
183     if ((s64)pc < 0) break;
184     // Printf("C pc[%zu] %zx\n", i, pc);
185     if (prev_pc - pc < kMaxOffset || pc - prev_pc < kMaxOffset) {
186       uptr offset = (s64)(pc - prev_pc);
187       offset |= (1U << 31);
188       if (c_index >= size) break;
189       // Printf("C co[%zu] offset %zx\n", i, offset);
190       compressed[c_index++] = offset;
191     } else {
192       uptr hi = pc >> 32;
193       uptr lo = (pc << 32) >> 32;
194       CHECK_EQ((hi & (1 << 31)), 0);
195       if (c_index + 1 >= size) break;
196       // Printf("C co[%zu] hi/lo: %zx %zx\n", c_index, hi, lo);
197       compressed[c_index++] = hi;
198       compressed[c_index++] = lo;
199     }
200     res++;
201     prev_pc = pc;
202   }
203   if (c_index < size)
204     compressed[c_index] = 0;
205   if (c_index + 1 < size)
206     compressed[c_index + 1] = 0;
207 #endif  // SANITIZER_WORDSIZE
208 
209   // debug-only code
210 #if 0
211   StackTrace check_stack;
212   UncompressStack(&check_stack, compressed, size);
213   if (res < check_stack.size) {
214     Printf("res %zu check_stack.size %zu; c_size %zu\n", res,
215            check_stack.size, size);
216   }
217   // |res| may be greater than check_stack.size, because
218   // UncompressStack(CompressStack(stack)) eliminates the 0x0 frames.
219   CHECK(res >= check_stack.size);
220   CHECK_EQ(0, REAL(memcmp)(check_stack.trace, stack->trace,
221                           check_stack.size * sizeof(uptr)));
222 #endif
223 
224   return res;
225 }
226 
227 SANITIZER_INTERFACE_ATTRIBUTE
UncompressStack(StackTrace * stack,u32 * compressed,uptr size)228 void StackTrace::UncompressStack(StackTrace *stack,
229                                  u32 *compressed, uptr size) {
230 #if SANITIZER_WORDSIZE == 32
231   // Don't uncompress, just copy.
232   stack->size = 0;
233   for (uptr i = 0; i < size && i < kStackTraceMax; i++) {
234     if (!compressed[i]) break;
235     stack->size++;
236     stack->trace[i] = compressed[i];
237   }
238 #else  // 64 bits, uncompress
239   uptr prev_pc = 0;
240   stack->size = 0;
241   for (uptr i = 0; i < size && stack->size < kStackTraceMax; i++) {
242     u32 x = compressed[i];
243     uptr pc = 0;
244     if (x & (1U << 31)) {
245       // Printf("U co[%zu] offset: %x\n", i, x);
246       // this is an offset
247       s32 offset = x;
248       offset = (offset << 1) >> 1;  // remove the 31-byte and sign-extend.
249       pc = prev_pc + offset;
250       CHECK(pc);
251     } else {
252       // CHECK(i + 1 < size);
253       if (i + 1 >= size) break;
254       uptr hi = x;
255       uptr lo = compressed[i+1];
256       // Printf("U co[%zu] hi/lo: %zx %zx\n", i, hi, lo);
257       i++;
258       pc = (hi << 32) | lo;
259       if (!pc) break;
260     }
261     // Printf("U pc[%zu] %zx\n", stack->size, pc);
262     stack->trace[stack->size++] = pc;
263     prev_pc = pc;
264   }
265 #endif  // SANITIZER_WORDSIZE
266 }
267 
268 }  // namespace __sanitizer
269