Extend s{,n}printf custom wrappers to support '*' in the format specifiers

[martignlo]

Summary

This is D7249 minus the changes to dfsan.cc

[pcc]

LGTM

[yingcong-wu]

compiler-rt/trunk/lib/dfsan/dfsan_custom.cc

1046

Hi guys, should it be dfsan_set_label(0, ptr, sizeof(*ptr) so that we set label for what ptr points to. I think it can be problems when sizeof(ptr) != sizeof(*ptr).

compiler-rt/trunk/lib/dfsan/dfsan_custom.cc

write_callback_info.write_callback_trampoline(
         write_callback_info.write_callback,
         fd, buf, count,
         fd_label, buf_label, count_label);
   }
 
   *ret_label = 0;
   return write(fd, buf, count);
 }
+}
 
 // Type used to extract a dfsan_label with va_arg()
 typedef int dfsan_label_va;
 
-// A chunk of data representing the output of formatting either a constant
-// string or a single format directive.
-struct Chunk {
-  // Address of the beginning of the formatted string
-  const char *ptr;
-  // Size of the formatted string
-  size_t size;
+// Formats a chunk either a constant string or a single format directive (e.g.,
+// '%.3f').
+struct Formatter {
+  Formatter(char *str_, const char *fmt_, size_t size_)
+      : str(str_), str_off(0), size(size_), fmt_start(fmt_), fmt_cur(fmt_),
+        width(-1) {}
+
+  int format() {
+    char *tmp_fmt = build_format_string();
+    int retval =
+        snprintf(str + str_off, str_off < size ? size - str_off : 0, tmp_fmt,
+                 0 /* used only to avoid warnings */);
+    free(tmp_fmt);
+    return retval;
+  }
+
+  template <typename T> int format(T arg) {
+    char *tmp_fmt = build_format_string();
+    int retval;
+    if (width >= 0) {
+      retval = snprintf(str + str_off, str_off < size ? size - str_off : 0,
+                        tmp_fmt, width, arg);
+    } else {
+      retval = snprintf(str + str_off, str_off < size ? size - str_off : 0,
+                        tmp_fmt, arg);
+    }
+    free(tmp_fmt);
+    return retval;
+  }
+
+  char *build_format_string() {
+    size_t fmt_size = fmt_cur - fmt_start + 1;
+    char *new_fmt = (char *)malloc(fmt_size + 1);
+    assert(new_fmt);
+    internal_memcpy(new_fmt, fmt_start, fmt_size);
+    new_fmt[fmt_size] = '\0';
+    return new_fmt;
+  }
 
-  // Type of DFSan label (depends on the format directive)
-  enum {
-    // Constant string, no argument and thus no label
-    NONE = 0,
-    // Label for an argument of '%n'
-    IGNORED,
-    // Label for a '%s' argument
-    STRING,
-    // Label for any other type of argument
-    NUMERIC,
-  } label_type;
+  char *str_cur() { return str + str_off; }
 
-  // Value of the argument (if label_type == STRING)
-  const char *arg;
-};
+  size_t num_written_bytes(int retval) {
+    if (retval < 0) {
+      return 0;
+    }
 
-// Formats the input. The output is stored in 'str' starting from offset
-// 'off'. The format directive is represented by the first 'format_size' bytes
-// of 'format'. If 'has_size' is true, 'size' bounds the number of output
-// bytes. Returns the return value of the vsnprintf call used to format the
-// input.
-static int format_chunk(char *str, size_t off, bool has_size, size_t size,
-                        const char *format, size_t format_size, ...) {
-  char *chunk_format = (char *) malloc(format_size + 1);
-  assert(chunk_format);
-  internal_memcpy(chunk_format, format, format_size);
-  chunk_format[format_size] = '\0';
+    size_t num_avail = str_off < size ? size - str_off : 0;
+    if (num_avail == 0) {
+      return 0;
+    }
 
-  va_list ap;
-  va_start(ap, format_size);
-  int r = 0;
-  if (has_size) {
-    r = vsnprintf(str + off, off < size ? size - off : 0, chunk_format, ap);
-  } else {
-    r = vsprintf(str + off, chunk_format, ap);
+    size_t num_written = retval;
+    // A return value of {v,}snprintf of size or more means that the output was
+    // truncated.
+    if (num_written >= num_avail) {
+      num_written -= num_avail;
     }
-  va_end(ap);
 
-  free(chunk_format);
-  return r;
+    return num_written;
   }
 
+  char *str;
+  size_t str_off;
+  size_t size;
+  const char *fmt_start;
+  const char *fmt_cur;
+  int width;
+};
+
 // Formats the input and propagates the input labels to the output. The output
-// is stored in 'str'. If 'has_size' is true, 'size' bounds the number of
-// output bytes. 'format' and 'ap' are the format string and the list of
-// arguments for formatting. Returns the return value vsnprintf would return.
+// is stored in 'str'. 'size' bounds the number of output bytes. 'format' and
+// 'ap' are the format string and the list of arguments for formatting. Returns
+// the return value vsnprintf would return.
 //
 // The function tokenizes the format string in chunks representing either a
 // constant string or a single format directive (e.g., '%.3f') and formats each
 // chunk independently into the output string. This approach allows to figure
 // out which bytes of the output string depends on which argument and thus to
 // propagate labels more precisely.
-static int format_buffer(char *str, bool has_size, size_t size,
-                         const char *format, dfsan_label *va_labels,
-                         dfsan_label *ret_label, va_list ap) {
-  InternalMmapVector<Chunk> chunks(8);
-  size_t off = 0;
-
-  while (*format) {
-    chunks.push_back(Chunk());
-    Chunk& chunk = chunks.back();
-    chunk.ptr = str + off;
-    chunk.arg = nullptr;
-
-    int status = 0;
+//
+// WARNING: This implementation does not support conversion specifiers with
+// positional arguments.
+static int format_buffer(char *str, size_t size, const char *fmt,
+                         dfsan_label *va_labels, dfsan_label *ret_label,
+                         va_list ap) {
+  Formatter formatter(str, fmt, size);
+
+  while (*formatter.fmt_cur) {
+    formatter.fmt_start = formatter.fmt_cur;
+    formatter.width = -1;
+    int retval = 0;
 
-    if (*format != '%') {
+    if (*formatter.fmt_cur != '%') {
       // Ordinary character. Consume all the characters until a '%' or the end
       // of the string.
-      size_t format_size = 0;
-      for (; *format && *format != '%'; ++format, ++format_size) {}
-      status = format_chunk(str, off, has_size, size, format - format_size,
-                            format_size);
-      chunk.label_type = Chunk::NONE;
+      for (; *(formatter.fmt_cur + 1) && *(formatter.fmt_cur + 1) != '%';
+           ++formatter.fmt_cur) {}
+      retval = formatter.format();
+      dfsan_set_label(0, formatter.str_cur(),
+                      formatter.num_written_bytes(retval));
     } else {
       // Conversion directive. Consume all the characters until a conversion
       // specifier or the end of the string.
-      bool end_format = false;
-#define FORMAT_CHUNK(t)                                                  \
-      format_chunk(str, off, has_size, size, format - format_size,  \
-                   format_size + 1, va_arg(ap, t))
-
-      for (size_t format_size = 1; *++format && !end_format; ++format_size) {
-        switch (*format) {
-          case 'd':
-          case 'i':
-          case 'o':
-          case 'u':
-          case 'x':
-          case 'X':
-            switch (*(format - 1)) {
-              case 'h':
-                // Also covers the 'hh' case (since the size of the arg is still
-                // an int).
-                status = FORMAT_CHUNK(int);
-                break;
-              case 'l':
-                if (format_size >= 2 && *(format - 2) == 'l') {
-                  status = FORMAT_CHUNK(long long int);
-                } else {
-                  status = FORMAT_CHUNK(long int);
-                }
-                break;
-              case 'q':
-                status = FORMAT_CHUNK(long long int);
-                break;
-              case 'j':
-                status = FORMAT_CHUNK(intmax_t);
-                break;
-              case 'z':
-                status = FORMAT_CHUNK(size_t);
-                break;
-              case 't':
-                status = FORMAT_CHUNK(size_t);
-                break;
-              default:
-                status = FORMAT_CHUNK(int);
-            }
-            chunk.label_type = Chunk::NUMERIC;
-            end_format = true;
-            break;
+      bool end_fmt = false;
+      for (; *formatter.fmt_cur && !end_fmt; ) {
+        switch (*++formatter.fmt_cur) {
+          switch (*(formatter.fmt_cur - 1)) {
+            retval = formatter.format(va_arg(ap, int));
+            if (formatter.fmt_cur - formatter.fmt_start >= 2 &&
+                *(formatter.fmt_cur - 2) == 'l') {
+              retval = formatter.format(va_arg(ap, long long int));
+              retval = formatter.format(va_arg(ap, long int));
+            retval = formatter.format(va_arg(ap, long long int));
+            retval = formatter.format(va_arg(ap, intmax_t));
+            retval = formatter.format(va_arg(ap, size_t));
+            retval = formatter.format(va_arg(ap, int));
+          dfsan_set_label(*va_labels++, formatter.str_cur(),
+                          formatter.num_written_bytes(retval));
+          end_fmt = true;
 
-          case 'a':
-          case 'A':
-          case 'e':
-          case 'E':
-          case 'f':
-          case 'F':
-          case 'g':
-          case 'G':
-            if (*(format - 1) == 'L') {
-              status = FORMAT_CHUNK(long double);
-            } else {
-              status = FORMAT_CHUNK(double);
-            }
-            chunk.label_type = Chunk::NUMERIC;
-            end_format = true;
-            break;
+          if (*(formatter.fmt_cur - 1) == 'L') {
+            retval = formatter.format(va_arg(ap, long double));
+            retval = formatter.format(va_arg(ap, double));
+          dfsan_set_label(*va_labels++, formatter.str_cur(),
+                          formatter.num_written_bytes(retval));
+          end_fmt = true;
 
-          case 'c':
-            status = FORMAT_CHUNK(int);
-            chunk.label_type = Chunk::NUMERIC;
-            end_format = true;
-            break;
+          retval = formatter.format(va_arg(ap, int));
+          dfsan_set_label(*va_labels++, formatter.str_cur(),
+                          formatter.num_written_bytes(retval));
+          end_fmt = true;
 
-          case 's':
-            chunk.arg = va_arg(ap, char *);
-            status =
-                format_chunk(str, off, has_size, size,
-                             format - format_size, format_size + 1,
-                             chunk.arg);
-            chunk.label_type = Chunk::STRING;
-            end_format = true;
-            break;
+        case 's': {
+          char *arg = va_arg(ap, char *);
+          retval = formatter.format(arg);
+          va_labels++;
+          internal_memcpy(shadow_for(formatter.str_cur()), shadow_for(arg),
+                          sizeof(dfsan_label) *
+                              formatter.num_written_bytes(retval));
+          end_fmt = true;
+        }
 
-          case 'p':
-            status = FORMAT_CHUNK(void *);
-            chunk.label_type = Chunk::NUMERIC;
-            end_format = true;
-            break;
+          retval = formatter.format(va_arg(ap, void *));
+          dfsan_set_label(*va_labels++, formatter.str_cur(),
+                          formatter.num_written_bytes(retval));
+          end_fmt = true;
 
-          case 'n':
-            *(va_arg(ap, int *)) = (int)off;
-            chunk.label_type = Chunk::IGNORED;
-            end_format = true;
-            break;
+        case 'n': {
+          int *ptr = va_arg(ap, int *);
+          *ptr = (int)formatter.str_off;
+          va_labels++;
+          dfsan_set_label(0, ptr, sizeof(ptr));
+          end_fmt = true;
+        }
 
-          case '%':
-            status = format_chunk(str, off, has_size, size,
-                                  format - format_size, format_size + 1);
-            chunk.label_type = Chunk::NONE;
-            end_format = true;
-            break;
+          retval = formatter.format();
+          dfsan_set_label(0, formatter.str_cur(),
+                          formatter.num_written_bytes(retval));
+          end_fmt = true;
+          break;
+
+        case '*':
+          formatter.width = va_arg(ap, int);
+          va_labels++;
 
-          default:
-            break;
         }
       }
-#undef FORMAT_CHUNK
     }
 
-    if (status < 0) {
-      return status;
+    if (retval < 0) {
+      return retval;
     }
 
-    // A return value of {v,}snprintf of size or more means that the output was
-    // truncated.
-    if (has_size) {
-      if (off < size) {
-        size_t ustatus = (size_t) status;
-        chunk.size = ustatus >= (size - off) ?
-            ustatus - (size - off) : ustatus;
-      } else {
-        chunk.size = 0;
-      }
-    } else {
-      chunk.size = status;
-    }
-    off += status;
-  }
-
-  // TODO(martignlo): Decide how to combine labels (e.g., whether to ignore or
-  // not the label of the format string).
-
-  // Label each output chunk according to the label supplied as argument to the
-  // function. We need to go through all the chunks and arguments even if the
-  // string was only partially printed ({v,}snprintf case).
-  for (size_t i = 0; i < chunks.size(); ++i) {
-    const Chunk& chunk = chunks[i];
-    void *chunk_ptr = const_cast<char *>(chunk.ptr);
-
-    switch (chunk.label_type) {
-      case Chunk::NONE:
-        dfsan_set_label(0, chunk_ptr, chunk.size);
-        break;
-      case Chunk::IGNORED:
-        va_labels++;
-        dfsan_set_label(0, chunk_ptr, chunk.size);
-        break;
-      case Chunk::NUMERIC: {
-        dfsan_label label = *va_labels++;
-        dfsan_set_label(label, chunk_ptr, chunk.size);
-        break;
-      }
-      case Chunk::STRING: {
-        // Consume the label of the pointer to the string
-        va_labels++;
-        internal_memcpy(shadow_for(chunk_ptr),
-                        shadow_for(chunk.arg),
-                        sizeof(dfsan_label) * (strlen(chunk.arg)));
-        break;
-      }
-    }
+    formatter.fmt_cur++;
+    formatter.str_off += retval;
   }
 
   *ret_label = 0;
 
   // Number of bytes written in total.
-  return off;
+  return formatter.str_off;
 }
 
+extern "C" {
 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfsw_sprintf(char *str, const char *format, dfsan_label str_label,
                    dfsan_label format_label, dfsan_label *va_labels,
                    dfsan_label *ret_label, ...) {
   va_list ap;
   va_start(ap, ret_label);
-  int ret = format_buffer(str, false, 0, format, va_labels, ret_label, ap);
+  int ret = format_buffer(str, ~0ul, format, va_labels, ret_label, ap);
   va_end(ap);
   return ret;
 }
 
 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfsw_snprintf(char *str, size_t size, const char *format,
                     dfsan_label str_label, dfsan_label size_label,
                     dfsan_label format_label, dfsan_label *va_labels,
                     dfsan_label *ret_label, ...) {
   va_list ap;
   va_start(ap, ret_label);
-  int ret = format_buffer(str, true, size, format, va_labels, ret_label, ap);
+  int ret = format_buffer(str, size, format, va_labels, ret_label, ap);
   va_end(ap);
   return ret;
 }
 }

compiler-rt/trunk/test/dfsan/custom.cc

void test_sprintf() {
   test_sprintf_chunk("1.234560e-01", "%e", 0.123456);
   test_sprintf_chunk("1.234560E-01", "%E", 0.123456);
   test_sprintf_chunk("0.1234567891234560", "%.16Lf",
                      (long double) 0.123456789123456);
 
   test_sprintf_chunk("z", "%c", 'z');
 
   // %n, %s, %d, %f, and %% already tested
+
+  // Test formatting with width passed as an argument.
+  r = sprintf(buf, "hi %*d my %*s friend %.*f", 3, 1, 6, "dear", 4, 3.14159265359);
+  assert(r == 30);
+  assert(strcmp(buf, "hi   1 my   dear friend 3.1416") == 0);
 }
 
 void test_snprintf() {
   char buf[2048];
   memset(buf, 'a', sizeof(buf));
   dfsan_set_label(0, buf, sizeof(buf));
   const char* s = "world";
   int y = 2014;