minidump_dump: dump stack memory like hexdump

The current stack output is one line byte string which is not easy for
humans to parse.  Extend the print mode to support a hexdump-like view
and switch to that by default.  Now we get something like:
Stack
00000000  20 67 7b 53 94 7f 00 00  01 00 00 00 00 00 00 00  | g{S...........|
00000010  00 70 c4 44 9a 25 00 00  08 65 7a 53 94 7f 00 00  |.p.D.%...ezS...|

BUG=chromium:598947

Change-Id: I868e1cf4faa435a14c5f1c35f94a5db4a49b6a6d
Reviewed-on: https://chromium-review.googlesource.com/404008
Reviewed-by: Mark Mentovai <mark@chromium.org>

src/google_breakpad/processor/minidump.h

@@ -236,6 +236,7 @@ class MinidumpMemoryRegion : public MinidumpObject,
 
   // Print a human-readable representation of the object to stdout.
   void Print() const;
+  void SetPrintMode(bool hexdump, unsigned int width);
 
  protected:
   explicit MinidumpMemoryRegion(Minidump* minidump);
@@ -252,6 +253,10 @@ class MinidumpMemoryRegion : public MinidumpObject,
   template<typename T> bool GetMemoryAtAddressInternal(uint64_t address,
                                                        T*        value) const;
 
+  // Knobs for controlling display of memory printing.
+  bool hexdump_;
+  unsigned int hexdump_width_;
+
   // The largest memory region that will be read from a minidump.  The
   // default is 1MB.
   static uint32_t max_bytes_;
@@ -1104,7 +1109,9 @@ class MinidumpLinuxMapsList : public MinidumpStream {
 class Minidump {
  public:
   // path is the pathname of a file containing the minidump.
-  explicit Minidump(const string& path);
+  explicit Minidump(const string& path,
+                    bool hexdump=false,
+                    unsigned int hexdump_width=16);
   // input is an istream wrapping minidump data. Minidump holds a
   // weak pointer to input, and the caller must ensure that the stream
   // is valid as long as the Minidump object is.
@@ -1214,6 +1221,9 @@ class Minidump {
   // Is the OS Android.
   bool IsAndroid();
 
+  // Get current hexdump display settings.
+  unsigned int HexdumpMode() const { return hexdump_ ? hexdump_width_ : 0; }
+
  private:
   // MinidumpStreamInfo is used in the MinidumpStreamMap.  It lets
   // the Minidump object locate interesting streams quickly, and
@@ -1275,6 +1285,10 @@ class Minidump {
   // Read().
   bool                      valid_;
 
+  // Knobs for controlling display of memory printing.
+  bool                      hexdump_;
+  unsigned int              hexdump_width_;
+
   DISALLOW_COPY_AND_ASSIGN(Minidump);
 };
 

src/processor/minidump.cc

@@ -1202,6 +1202,8 @@ MinidumpMemoryRegion::MinidumpMemoryRegion(Minidump* minidump)
     : MinidumpObject(minidump),
       descriptor_(NULL),
       memory_(NULL) {
+  hexdump_width_ = minidump->HexdumpMode();
+  hexdump_ = hexdump_width_ != 0;
 }
 
 
@@ -1360,19 +1362,77 @@ void MinidumpMemoryRegion::Print() const {
 
   const uint8_t* memory = GetMemory();
   if (memory) {
-    printf("0x");
+    if (hexdump_) {
+      // Pretty hexdump view.
       for (unsigned int byte_index = 0;
            byte_index < descriptor_->memory.data_size;
-         byte_index++) {
-      printf("%02x", memory[byte_index]);
+           byte_index += hexdump_width_) {
+        // In case the memory won't fill a whole line.
+        unsigned int num_bytes = std::min(
+            descriptor_->memory.data_size - byte_index, hexdump_width_);
+
+        // Display the leading address.
+        printf("%08x  ", byte_index);
+
+        // Show the bytes in hex.
+        for (unsigned int i = 0; i < hexdump_width_; ++i) {
+          if (i < num_bytes) {
+            // Show the single byte of memory in hex.
+            printf("%02x ", memory[byte_index + i]);
+          } else {
+            // If this line doesn't fill up, pad it out.
+            printf("   ");
+          }
+
+          // Insert a space every 8 bytes to make it more readable.
+          if (((i + 1) % 8) == 0) {
+            printf(" ");
+          }
+        }
+
+        // Decode the line as ASCII.
+        printf("|");
+        for (unsigned int i = 0; i < hexdump_width_; ++i) {
+          if (i < num_bytes) {
+            uint8_t byte = memory[byte_index + i];
+            printf("%c", isprint(byte) ? byte : '.');
+          } else {
+            // If this line doesn't fill up, pad it out.
+            printf(" ");
+          }
+        }
+        printf("|\n");
+      }
+    } else {
+      // Ugly raw string view.
+      printf("0x");
+      for (unsigned int i = 0;
+           i < descriptor_->memory.data_size;
+           i++) {
+        printf("%02x", memory[i]);
       }
       printf("\n");
+    }
   } else {
     printf("No memory\n");
   }
 }
 
 
+void MinidumpMemoryRegion::SetPrintMode(bool hexdump,
+                                        unsigned int hexdump_width) {
+  // Require the width to be a multiple of 8 bytes.
+  if (hexdump_width == 0 || (hexdump_width % 8) != 0) {
+    BPLOG(ERROR) << "MinidumpMemoryRegion print hexdump_width must be "
+                    "multiple of 8, not " << hexdump_width;
+    return;
+  }
+
+  hexdump_ = hexdump;
+  hexdump_width_ = hexdump_width;
+}
+
+
 //
 // MinidumpThread
 //
@@ -4694,14 +4754,16 @@ uint32_t Minidump::max_streams_ = 128;
 unsigned int Minidump::max_string_length_ = 1024;
 
 
-Minidump::Minidump(const string& path)
+Minidump::Minidump(const string& path, bool hexdump, unsigned int hexdump_width)
     : header_(),
       directory_(NULL),
       stream_map_(new MinidumpStreamMap()),
       path_(path),
       stream_(NULL),
       swap_(false),
-      valid_(false) {
+      valid_(false),
+      hexdump_(hexdump),
+      hexdump_width_(hexdump_width) {
 }
 
 Minidump::Minidump(istream& stream)

src/processor/minidump_dump.cc

@@ -55,9 +55,11 @@ using google_breakpad::MinidumpBreakpadInfo;
 
 struct Options {
   Options()
-      : minidumpPath() {}
+      : minidumpPath(), hexdump(false), hexdump_width(hexdump_width) {}
 
   string minidumpPath;
+  bool hexdump;
+  unsigned int hexdump_width;
 };
 
 static void DumpRawStream(Minidump *minidump,
@@ -99,8 +101,9 @@ static void DumpRawStream(Minidump *minidump,
   printf("\n\n");
 }
 
-static bool PrintMinidumpDump(const string& minidump_file) {
-  Minidump minidump(minidump_file);
+static bool PrintMinidumpDump(const Options& options) {
+  Minidump minidump(options.minidumpPath,
+                    options.hexdump);
   if (!minidump.Read()) {
     BPLOG(ERROR) << "minidump.Read() failed";
     return false;
@@ -218,6 +221,7 @@ Usage(int argc, const char *argv[], bool error) {
           "\n"
           "Options:\n"
           "  <minidump> should be a minidump.\n"
+          "  -x:\t Display memory in a hexdump like format\n"
           "  -h:\t Usage\n",
           argv[0]);
 }
@@ -227,8 +231,11 @@ static void
 SetupOptions(int argc, const char *argv[], Options *options) {
   int ch;
 
-  while ((ch = getopt(argc, (char * const *)argv, "h")) != -1) {
+  while ((ch = getopt(argc, (char * const *)argv, "xh")) != -1) {
     switch (ch) {
+      case 'x':
+        options->hexdump = true;
+        break;
       case 'h':
         Usage(argc, argv, false);
         exit(0);
@@ -254,5 +261,5 @@ int main(int argc, const char *argv[]) {
   Options options;
   BPLOG_INIT(&argc, &argv);
   SetupOptions(argc, argv, &options);
-  return PrintMinidumpDump(options.minidumpPath) ? 0 : 1;
+  return PrintMinidumpDump(options) ? 0 : 1;
 }