1 //===-- sanitizer_printf.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 // This file is shared between AddressSanitizer and ThreadSanitizer.
10 //
11 // Internal printf function, used inside run-time libraries.
12 // We can't use libc printf because we intercept some of the functions used
13 // inside it.
14 //===----------------------------------------------------------------------===//
15 
16 #include "sanitizer_common.h"
17 #include "sanitizer_flags.h"
18 #include "sanitizer_libc.h"
19 
20 #include <stdio.h>
21 #include <stdarg.h>
22 
23 #if SANITIZER_WINDOWS && defined(_MSC_VER) && _MSC_VER < 1800 &&               \
24       !defined(va_copy)
25 # define va_copy(dst, src) ((dst) = (src))
26 #endif
27 
28 namespace __sanitizer {
29 
30 static int AppendChar(char **buff, const char *buff_end, char c) {
31   if (*buff < buff_end) {
32     **buff = c;
33     (*buff)++;
34   }
35   return 1;
36 }
37 
38 // Appends number in a given base to buffer. If its length is less than
39 // |minimal_num_length|, it is padded with leading zeroes or spaces, depending
40 // on the value of |pad_with_zero|.
41 static int AppendNumber(char **buff, const char *buff_end, u64 absolute_value,
42                         u8 base, u8 minimal_num_length, bool pad_with_zero,
43                         bool negative, bool uppercase) {
44   uptr const kMaxLen = 30;
45   RAW_CHECK(base == 10 || base == 16);
46   RAW_CHECK(base == 10 || !negative);
47   RAW_CHECK(absolute_value || !negative);
48   RAW_CHECK(minimal_num_length < kMaxLen);
49   int result = 0;
50   if (negative && minimal_num_length)
51     --minimal_num_length;
52   if (negative && pad_with_zero)
53     result += AppendChar(buff, buff_end, '-');
54   uptr num_buffer[kMaxLen];
55   int pos = 0;
56   do {
57     RAW_CHECK_MSG((uptr)pos < kMaxLen, "AppendNumber buffer overflow");
58     num_buffer[pos++] = absolute_value % base;
59     absolute_value /= base;
60   } while (absolute_value > 0);
61   if (pos < minimal_num_length) {
62     // Make sure compiler doesn't insert call to memset here.
63     internal_memset(&num_buffer[pos], 0,
64                     sizeof(num_buffer[0]) * (minimal_num_length - pos));
65     pos = minimal_num_length;
66   }
67   RAW_CHECK(pos > 0);
68   pos--;
69   for (; pos >= 0 && num_buffer[pos] == 0; pos--) {
70     char c = (pad_with_zero || pos == 0) ? '0' : ' ';
71     result += AppendChar(buff, buff_end, c);
72   }
73   if (negative && !pad_with_zero) result += AppendChar(buff, buff_end, '-');
74   for (; pos >= 0; pos--) {
75     char digit = static_cast<char>(num_buffer[pos]);
76     digit = (digit < 10) ? '0' + digit : (uppercase ? 'A' : 'a') + digit - 10;
77     result += AppendChar(buff, buff_end, digit);
78   }
79   return result;
80 }
81 
82 static int AppendUnsigned(char **buff, const char *buff_end, u64 num, u8 base,
83                           u8 minimal_num_length, bool pad_with_zero,
84                           bool uppercase) {
85   return AppendNumber(buff, buff_end, num, base, minimal_num_length,
86                       pad_with_zero, false /* negative */, uppercase);
87 }
88 
89 static int AppendSignedDecimal(char **buff, const char *buff_end, s64 num,
90                                u8 minimal_num_length, bool pad_with_zero) {
91   bool negative = (num < 0);
92   return AppendNumber(buff, buff_end, (u64)(negative ? -num : num), 10,
93                       minimal_num_length, pad_with_zero, negative,
94                       false /* uppercase */);
95 }
96 
97 
98 // Use the fact that explicitly requesting 0 width (%0s) results in UB and
99 // interpret width == 0 as "no width requested":
100 // width == 0 - no width requested
101 // width  < 0 - left-justify s within and pad it to -width chars, if necessary
102 // width  > 0 - right-justify s, not implemented yet
103 static int AppendString(char **buff, const char *buff_end, int width,
104                         int max_chars, const char *s) {
105   if (!s)
106     s = "<null>";
107   int result = 0;
108   for (; *s; s++) {
109     if (max_chars >= 0 && result >= max_chars)
110       break;
111     result += AppendChar(buff, buff_end, *s);
112   }
113   // Only the left justified strings are supported.
114   while (width < -result)
115     result += AppendChar(buff, buff_end, ' ');
116   return result;
117 }
118 
119 static int AppendPointer(char **buff, const char *buff_end, u64 ptr_value) {
120   int result = 0;
121   result += AppendString(buff, buff_end, 0, -1, "0x");
122   result += AppendUnsigned(buff, buff_end, ptr_value, 16,
123                            SANITIZER_POINTER_FORMAT_LENGTH,
124                            true /* pad_with_zero */, false /* uppercase */);
125   return result;
126 }
127 
128 int VSNPrintf(char *buff, int buff_length,
129               const char *format, va_list args) {
130   static const char *kPrintfFormatsHelp =
131       "Supported Printf formats: %([0-9]*)?(z|l|ll)?{d,u,x,X}; %p; "
132       "%[-]([0-9]*)?(\\.\\*)?s; %c\nProvided format: ";
133   RAW_CHECK(format);
134   RAW_CHECK(buff_length > 0);
135   const char *buff_end = &buff[buff_length - 1];
136   const char *cur = format;
137   int result = 0;
138   for (; *cur; cur++) {
139     if (*cur != '%') {
140       result += AppendChar(&buff, buff_end, *cur);
141       continue;
142     }
143     cur++;
144     bool left_justified = *cur == '-';
145     if (left_justified)
146       cur++;
147     bool have_width = (*cur >= '0' && *cur <= '9');
148     bool pad_with_zero = (*cur == '0');
149     int width = 0;
150     if (have_width) {
151       while (*cur >= '0' && *cur <= '9') {
152         width = width * 10 + *cur++ - '0';
153       }
154     }
155     bool have_precision = (cur[0] == '.' && cur[1] == '*');
156     int precision = -1;
157     if (have_precision) {
158       cur += 2;
159       precision = va_arg(args, int);
160     }
161     bool have_z = (*cur == 'z');
162     cur += have_z;
163     bool have_l = cur[0] == 'l' && cur[1] != 'l';
164     cur += have_l;
165     bool have_ll = cur[0] == 'l' && cur[1] == 'l';
166     cur += have_ll * 2;
167     const bool have_length = have_z || have_l || have_ll;
168     const bool have_flags = have_width || have_length;
169     // At the moment only %s supports precision and left-justification.
170     CHECK(!((precision >= 0 || left_justified) && *cur != 's'));
171     switch (*cur) {
172       case 'd': {
173         s64 dval = have_ll  ? va_arg(args, s64)
174                    : have_z ? va_arg(args, sptr)
175                    : have_l ? va_arg(args, long)
176                             : va_arg(args, int);
177         result += AppendSignedDecimal(&buff, buff_end, dval, width,
178                                       pad_with_zero);
179         break;
180       }
181       case 'u':
182       case 'x':
183       case 'X': {
184         u64 uval = have_ll  ? va_arg(args, u64)
185                    : have_z ? va_arg(args, uptr)
186                    : have_l ? va_arg(args, unsigned long)
187                             : va_arg(args, unsigned);
188         bool uppercase = (*cur == 'X');
189         result += AppendUnsigned(&buff, buff_end, uval, (*cur == 'u') ? 10 : 16,
190                                  width, pad_with_zero, uppercase);
191         break;
192       }
193       case 'p': {
194         RAW_CHECK_VA(!have_flags, kPrintfFormatsHelp, format);
195         result += AppendPointer(&buff, buff_end, va_arg(args, uptr));
196         break;
197       }
198       case 's': {
199         RAW_CHECK_VA(!have_length, kPrintfFormatsHelp, format);
200         // Only left-justified width is supported.
201         CHECK(!have_width || left_justified);
202         result += AppendString(&buff, buff_end, left_justified ? -width : width,
203                                precision, va_arg(args, char*));
204         break;
205       }
206       case 'c': {
207         RAW_CHECK_VA(!have_flags, kPrintfFormatsHelp, format);
208         result += AppendChar(&buff, buff_end, va_arg(args, int));
209         break;
210       }
211       case '%' : {
212         RAW_CHECK_VA(!have_flags, kPrintfFormatsHelp, format);
213         result += AppendChar(&buff, buff_end, '%');
214         break;
215       }
216       default: {
217         RAW_CHECK_VA(false, kPrintfFormatsHelp, format);
218       }
219     }
220   }
221   RAW_CHECK(buff <= buff_end);
222   AppendChar(&buff, buff_end + 1, '\0');
223   return result;
224 }
225 
226 static void (*PrintfAndReportCallback)(const char *);
227 void SetPrintfAndReportCallback(void (*callback)(const char *)) {
228   PrintfAndReportCallback = callback;
229 }
230 
231 // Can be overriden in frontend.
232 #if SANITIZER_GO && defined(TSAN_EXTERNAL_HOOKS)
233 // Implementation must be defined in frontend.
234 extern "C" void __sanitizer_on_print(const char *str);
235 #else
236 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_on_print, const char *str) {
237   (void)str;
238 }
239 #endif
240 
241 static void CallPrintfAndReportCallback(const char *str) {
242   __sanitizer_on_print(str);
243   if (PrintfAndReportCallback)
244     PrintfAndReportCallback(str);
245 }
246 
247 static void NOINLINE SharedPrintfCodeNoBuffer(bool append_pid,
248                                               char *local_buffer,
249                                               int buffer_size,
250                                               const char *format,
251                                               va_list args) {
252   va_list args2;
253   va_copy(args2, args);
254   InternalMmapVector<char> v;
255   int needed_length = 0;
256   char *buffer = local_buffer;
257   // First try to print a message using a local buffer, and then fall back to
258   // mmaped buffer.
259   for (int use_mmap = 0;; use_mmap++) {
260     if (use_mmap) {
261       va_end(args);
262       va_copy(args, args2);
263       v.resize(needed_length + 1);
264       buffer_size = v.capacity();
265       v.resize(buffer_size);
266       buffer = &v[0];
267     }
268     needed_length = 0;
269     // Fuchsia's logging infrastructure always keeps track of the logging
270     // process, thread, and timestamp, so never prepend such information.
271     if (!SANITIZER_FUCHSIA && append_pid) {
272       int pid = internal_getpid();
273       const char *exe_name = GetProcessName();
274       if (common_flags()->log_exe_name && exe_name) {
275         needed_length += internal_snprintf(buffer, buffer_size,
276                                            "==%s", exe_name);
277         if (needed_length >= buffer_size)
278           continue;
279       }
280       needed_length += internal_snprintf(
281           buffer + needed_length, buffer_size - needed_length, "==%d==", pid);
282       if (needed_length >= buffer_size)
283         continue;
284     }
285     needed_length += VSNPrintf(buffer + needed_length,
286                                buffer_size - needed_length, format, args);
287     if (needed_length >= buffer_size)
288       continue;
289     // If the message fit into the buffer, print it and exit.
290     break;
291   }
292   RawWrite(buffer);
293 
294   // Remove color sequences from the message.
295   RemoveANSIEscapeSequencesFromString(buffer);
296   CallPrintfAndReportCallback(buffer);
297   LogMessageOnPrintf(buffer);
298 
299   va_end(args2);
300 }
301 
302 static void NOINLINE SharedPrintfCode(bool append_pid, const char *format,
303                                       va_list args) {
304   // |local_buffer| is small enough not to overflow the stack and/or violate
305   // the stack limit enforced by TSan (-Wframe-larger-than=512). On the other
306   // hand, the bigger the buffer is, the more the chance the error report will
307   // fit into it.
308   char local_buffer[400];
309   SharedPrintfCodeNoBuffer(append_pid, local_buffer, ARRAY_SIZE(local_buffer),
310                            format, args);
311 }
312 
313 void Printf(const char *format, ...) {
314   va_list args;
315   va_start(args, format);
316   SharedPrintfCode(false, format, args);
317   va_end(args);
318 }
319 
320 // Like Printf, but prints the current PID before the output string.
321 void Report(const char *format, ...) {
322   va_list args;
323   va_start(args, format);
324   SharedPrintfCode(true, format, args);
325   va_end(args);
326 }
327 
328 // Writes at most "length" symbols to "buffer" (including trailing '\0').
329 // Returns the number of symbols that should have been written to buffer
330 // (not including trailing '\0'). Thus, the string is truncated
331 // iff return value is not less than "length".
332 int internal_snprintf(char *buffer, uptr length, const char *format, ...) {
333   va_list args;
334   va_start(args, format);
335   int needed_length = VSNPrintf(buffer, length, format, args);
336   va_end(args);
337   return needed_length;
338 }
339 
340 void InternalScopedString::append(const char *format, ...) {
341   uptr prev_len = length();
342 
343   while (true) {
344     buffer_.resize(buffer_.capacity());
345 
346     va_list args;
347     va_start(args, format);
348     uptr sz = VSNPrintf(buffer_.data() + prev_len, buffer_.size() - prev_len,
349                         format, args);
350     va_end(args);
351     if (sz < buffer_.size() - prev_len) {
352       buffer_.resize(prev_len + sz + 1);
353       break;
354     }
355 
356     buffer_.reserve(buffer_.capacity() * 2);
357   }
358   CHECK_EQ(buffer_[length()], '\0');
359 }
360 
361 } // namespace __sanitizer
362