return a crc32 uuid when an ELF file has no build ID

BUILD

@@ -205,6 +205,7 @@ filegroup(
         "Headers/DebugServer2/Target/ThreadBase.h",
         "Headers/DebugServer2/Utils/Backtrace.h",
         "Headers/DebugServer2/Utils/Bits.h",
+        "Headers/DebugServer2/Utils/crc32.h",
         "Headers/DebugServer2/Utils/CompilerSupport.h",
         "Headers/DebugServer2/Utils/Daemon.h",
         "Headers/DebugServer2/Utils/Enums.h",
@@ -348,6 +349,7 @@ filegroup(
         "Sources/Target/Common/ProcessBase.cpp",
         "Sources/Target/Common/ThreadBase.cpp",
         "Sources/Utils/Backtrace.cpp",
+        "Sources/Utils/crc32.cpp",
         "Sources/Utils/Log.cpp",
         "Sources/Utils/OptParse.cpp",
         "Sources/Utils/Stringify.cpp",

CMakeLists.txt

@@ -202,6 +202,7 @@ add_executable(ds2
   Sources/Target/Common/${DS2_ARCHITECTURE}/ProcessBase${DS2_ARCHITECTURE}.cpp
 
   Sources/Utils/Backtrace.cpp
+  Sources/Utils/crc32.c
   Sources/Utils/Log.cpp
   Sources/Utils/OptParse.cpp
   Sources/Utils/Stringify.cpp)

Headers/DebugServer2/Host/File.h

@@ -65,6 +65,7 @@ class File {
 public:
   static ErrorCode fileSize(std::string const &path, uint64_t &size);
   static ErrorCode fileMode(std::string const &path, uint32_t &mode);
+  static ErrorCode crc32(std::string const &path, uint32_t &crc);
 
 protected:
   int _fd;

Headers/DebugServer2/Support/POSIX/ELFSupport.h

@@ -32,8 +32,16 @@ class ELFSupport {
                           NotesHeader &nhdr, ByteVector &id);
 
   template <typename ELFHeader, typename SectionHeader>
-  static bool ReadSectionHeader(int fd, const ELFHeader &ehdr, SectionHeader &shdr,
-                                size_t idx);
+  static bool ReadSectionHeader(int fd, const ELFHeader &ehdr,
+                                SectionHeader &shdr, size_t idx);
+
+  template <typename ELFHeader, typename SectionHeader>
+  static bool ReadStringTable(int fd, const ELFHeader &ehdr,
+                              SectionHeader &shdr, std::vector<char> &table);
+
+  template <typename ELFHeader, typename SectionHeader>
+  static bool ReadDebugLinkCRC(int fd, const ELFHeader &ehdr,
+                               SectionHeader &shdr, ByteVector &crc);
 };
 } // namespace Support
 } // namespace ds2

Headers/DebugServer2/Utils/crc32.h

@@ -0,0 +1,19 @@
+/*-
+ *  COPYRIGHT (C) 1986 Gary S. Brown.  You may use this program, or
+ *  code or tables extracted from it, as desired without restriction.
+ */
+
+#pragma once
+
+#include <stddef.h>
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+uint32_t crc32(uint32_t crc, const void *buf, size_t size);
+
+#ifdef __cplusplus
+}
+#endif

Sources/GDBRemote/Mixins/FileOperationsMixin.hpp

@@ -130,18 +130,26 @@ ErrorCode FileOperationsMixin<T>::onQueryModuleInfo(Session &session,
                                                      std::string &triple,
                                                      ModuleInfo &info) const {
   ByteVector buildId;
-  if (Platform::GetExecutableFileBuildID(path, buildId)) {
-    // format the uuid as an upper-case string with two hex chars per byte
-    std::ostringstream ss;
-    for(const auto b : buildId)
-      ss << std::uppercase << std::hex << std::setfill('0') << std::setw(2) << int(b);
-
-    info.uuid = ss.str();
+  if (!Platform::GetExecutableFileBuildID(path, buildId)) {
+    // Not all executable files contain an embedded build ID. In this case,
+    // return a crc32 of the contents of the file. The documentation for
+    // `qModuleInfo` suggests an md5 hash can be returned as "md5" in the
+    // response instead of "uuid." However, returning a crc32 is consistent
+    // with behavior of lldb-server.
+    uint32_t crc;
+    CHK(File::crc32(path, crc));
+    std::copy(reinterpret_cast<uint8_t*>(&crc),
+              reinterpret_cast<uint8_t*>(&crc) + sizeof(crc),
+              std::back_inserter(buildId));
   }
 
-  // TODO(andrurogerz): Not all executable files contain an embedded build ID.
-  // If GetExecutableFileBuildID fails, calculate an md5 hash of the file
-  // contents and return that as an "md5" field instead of the "uuid" field.
+  // format the uuid as an upper-case string with two hex chars per byte
+  std::ostringstream ss;
+  for(const auto b : buildId)
+    ss << std::uppercase << std::hex << std::setfill('0') << std::setw(2) << int(b);
+
+  info.uuid = ss.str();
+
 
   auto error = File::fileSize(path, info.file_size);
   if (error != kSuccess)

Sources/Host/POSIX/File.cpp

@@ -10,6 +10,7 @@
 
 #include "DebugServer2/Host/File.h"
 #include "DebugServer2/Host/Platform.h"
+#include "DebugServer2/Utils/crc32.h"
 
 #include <fcntl.h>
 #include <limits>
@@ -216,5 +217,23 @@ ErrorCode File::fileMode(std::string const &path, uint32_t &mode) {
   mode = static_cast<uint32_t>(ALLPERMS & stbuf.st_mode);
   return kSuccess;
 }
+
+ErrorCode File::crc32(std::string const &path, uint32_t &crc) {
+  int fd = ::open(path.c_str(), O_RDONLY);
+  if (fd < 0)
+    return Platform::TranslateError();
+
+  ByteVector buffer(getpagesize());
+  ssize_t bytesRead;
+
+  crc = ::crc32(0L, nullptr, 0);
+  while ((bytesRead = ::read(fd, buffer.data(), buffer.size())) > 0)
+      crc = ::crc32(crc, buffer.data(), bytesRead);
+
+  ::close(fd);
+
+  return kSuccess;
+}
+
 } // namespace Host
 } // namespace ds2

Sources/Host/Windows/File.cpp

@@ -51,5 +51,9 @@ ErrorCode File::fileMode(std::string const &path, uint32_t &mode) {
   return kErrorUnsupported;
 }
 
+ErrorCode File::crc32(std::string const &path, uint32_t &crc) {
+  return kErrorUnsupported;
+}
+
 } // namespace Host
 } // namespace ds2

Sources/Support/POSIX/ELFSupport.cpp

@@ -91,7 +91,8 @@ bool ELFSupport::GetELFFileBuildID(std::string const &path, ByteVector &buildId)
     case ELFCLASS32: {
       Elf32_Shdr shdr;
       Elf32_Nhdr nhdr;
-      result = ReadBuildID(fd, ehdr, shdr, nhdr, buildId);
+      if (!(result = ReadBuildID(fd, ehdr, shdr, nhdr, buildId)))
+        result = ReadDebugLinkCRC(fd, ehdr, shdr, buildId);
       break;
     }
 
@@ -102,7 +103,8 @@ bool ELFSupport::GetELFFileBuildID(std::string const &path, ByteVector &buildId)
 
       Elf64_Shdr shdr;
       Elf64_Nhdr nhdr;
-      result = ReadBuildID(fd, ehdr, shdr, nhdr, buildId);
+      if (!(result = ReadBuildID(fd, ehdr, shdr, nhdr, buildId)))
+        result = ReadDebugLinkCRC(fd, ehdr, shdr, buildId);
       break;
     }
 
@@ -123,30 +125,30 @@ bool ELFSupport::GetELFFileBuildID(std::string const &path, ByteVector &buildId)
 template <typename ELFHeader, typename SectionHeader, typename NotesHeader>
 bool ELFSupport::ReadBuildID(int fd, const ELFHeader &ehdr, SectionHeader &shdr,
                              NotesHeader &nhdr, ByteVector &id) {
-    // Build ID is found in a note section with note type NT_GNU_BUILD_ID.
-    // The section is typically named .note.gnu.build-id.
-    for (size_t i = 0; i < ehdr.e_shnum; i++) {
-      if (!ReadSectionHeader(fd, ehdr, shdr, i))
-        return false;
+  // Build ID is found in a note section with note type NT_GNU_BUILD_ID.
+  // The section is typically named .note.gnu.build-id.
+  for (size_t i = 0; i < ehdr.e_shnum; i++) {
+    if (!ReadSectionHeader(fd, ehdr, shdr, i))
+      return false;
 
-      if (shdr.sh_type != SHT_NOTE)
-        continue;
+    if (shdr.sh_type != SHT_NOTE)
+      continue;
 
-      if (::pread(fd, &nhdr, sizeof(nhdr), shdr.sh_offset) != sizeof(nhdr))
-        return false;
+    if (::pread(fd, &nhdr, sizeof(nhdr), shdr.sh_offset) != sizeof(nhdr))
+      return false;
 
-      if (nhdr.n_type != NT_GNU_BUILD_ID)
-        continue;
+    if (nhdr.n_type != NT_GNU_BUILD_ID)
+      continue;
 
-      id.resize(nhdr.n_descsz);
-      const off_t pos = shdr.sh_offset + sizeof(nhdr) + nhdr.n_namesz;
-      if (::pread(fd, id.data(), nhdr.n_descsz, pos) != nhdr.n_descsz)
-        return false;
+    id.resize(nhdr.n_descsz);
+    const off_t pos = shdr.sh_offset + sizeof(nhdr) + nhdr.n_namesz;
+    if (::pread(fd, id.data(), nhdr.n_descsz, pos) != nhdr.n_descsz)
+      return false;
 
-      return true;
-    }
+    return true;
+  }
 
-    return false;
+  return false;
 }
 
 template <typename ELFHeader, typename SectionHeader>
@@ -161,5 +163,70 @@ bool ELFSupport::ReadSectionHeader(int fd, const ELFHeader &ehdr, SectionHeader
 
   return true;
 }
+
+template <typename ELFHeader, typename SectionHeader>
+bool ELFSupport::ReadStringTable(int fd, const ELFHeader &ehdr,
+                                 SectionHeader &shdr,
+                                 std::vector<char> &table) {
+  // e_shstrndx is the index of the string table containing section names
+  if (!ReadSectionHeader(fd, ehdr, shdr, ehdr.e_shstrndx))
+    return false;
+
+  if (shdr.sh_type != SHT_STRTAB)
+    return false;
+
+  table.resize(shdr.sh_size);
+  if (::pread(fd, &table[0], shdr.sh_size, shdr.sh_offset) != shdr.sh_size)
+    return false;
+
+  return true;
+}
+
+template <typename ELFHeader, typename SectionHeader>
+bool ELFSupport::ReadDebugLinkCRC(int fd, const ELFHeader &ehdr,
+                                  SectionHeader &shdr, ByteVector &crc) {
+
+  std::vector<char> table;
+  if (!ReadStringTable(fd, ehdr, shdr, table))
+    return false;
+
+  for (size_t i = 0; i < ehdr.e_shnum; i++) {
+    if (!ReadSectionHeader(fd, ehdr, shdr, i))
+      return false;
+
+    if (shdr.sh_type != SHT_PROGBITS)
+      continue;
+
+    const std::string sectionName(&table[shdr.sh_name]);
+    if (sectionName != ".gnu_debuglink")
+      continue;
+
+    // The .gnu_debuglink section contains the following:
+    // 1) A filename with any leading directory components removed (base name)
+    // 2) A string-terminating zero byte
+    // 3) Zero to three bytes of padding to ensure the next value is four-byte
+    //    aligned
+    // 4) A four byte crc32 checksum of the debug information file's contents
+    //    (same endianness as used for the containing executable file)
+    ByteVector section(shdr.sh_size);
+    if (::pread(fd, &section[0], shdr.sh_size, shdr.sh_offset) != shdr.sh_size)
+      return false;
+
+    const std::string name = reinterpret_cast<char*>(section.data());
+    const size_t offset = (name.length() + 4) & ~static_cast<size_t>(3);
+
+    if (offset + sizeof(uint32_t) > section.size())
+      return false; // malformated
+
+    crc.clear();
+    auto start = section.begin() + offset;
+    std::copy(start, start + sizeof(uint32_t), std::back_inserter(crc));
+
+    DS2LOG(Info, "using .gnu_debuglink (%s) as build id", name.c_str());
+    return true;
+  }
+
+  return false;
+}
 } // namespace Support
 } // namespace ds2

Sources/Utils/crc32.c

@@ -0,0 +1,101 @@
+/*-
+ *  COPYRIGHT (C) 1986 Gary S. Brown.  You may use this program, or
+ *  code or tables extracted from it, as desired without restriction.
+ */
+
+/*
+ *  First, the polynomial itself and its table of feedback terms.  The
+ *  polynomial is
+ *  X^32+X^26+X^23+X^22+X^16+X^12+X^11+X^10+X^8+X^7+X^5+X^4+X^2+X^1+X^0
+ *
+ *  Note that we take it "backwards" and put the highest-order term in
+ *  the lowest-order bit.  The X^32 term is "implied"; the LSB is the
+ *  X^31 term, etc.  The X^0 term (usually shown as "+1") results in
+ *  the MSB being 1
+ *
+ *  Note that the usual hardware shift register implementation, which
+ *  is what we're using (we're merely optimizing it by doing eight-bit
+ *  chunks at a time) shifts bits into the lowest-order term.  In our
+ *  implementation, that means shifting towards the right.  Why do we
+ *  do it this way?  Because the calculated CRC must be transmitted in
+ *  order from highest-order term to lowest-order term.  UARTs transmit
+ *  characters in order from LSB to MSB.  By storing the CRC this way
+ *  we hand it to the UART in the order low-byte to high-byte; the UART
+ *  sends each low-bit to hight-bit; and the result is transmission bit
+ *  by bit from highest- to lowest-order term without requiring any bit
+ *  shuffling on our part.  Reception works similarly
+ *
+ *  The feedback terms table consists of 256, 32-bit entries.  Notes
+ *
+ *      The table can be generated at runtime if desired; code to do so
+ *      is shown later.  It might not be obvious, but the feedback
+ *      terms simply represent the results of eight shift/xor opera
+ *      tions for all combinations of data and CRC register values
+ *
+ *      The values must be right-shifted by eight bits by the "updcrc
+ *      logic; the shift must be unsigned (bring in zeroes).  On some
+ *      hardware you could probably optimize the shift in assembler by
+ *      using byte-swap instructions
+ *      polynomial $edb88320
+ *
+ *
+ * CRC32 code derived from work by Gary S. Brown.
+ */
+
+#include <stddef.h>
+#include <stdint.h>
+
+static const uint32_t crc32_tab[] = {
+  0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f,
+  0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988,
+  0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91, 0x1db71064, 0x6ab020f2,
+  0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
+  0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
+  0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172,
+  0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, 0x35b5a8fa, 0x42b2986c,
+  0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
+  0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423,
+  0xcfba9599, 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
+  0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190, 0x01db7106,
+  0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
+  0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d,
+  0x91646c97, 0xe6635c01, 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e,
+  0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
+  0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
+  0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7,
+  0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0,
+  0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa,
+  0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
+  0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81,
+  0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a,
+  0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683, 0xe3630b12, 0x94643b84,
+  0x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
+  0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
+  0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc,
+  0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5, 0xd6d6a3e8, 0xa1d1937e,
+  0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
+  0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55,
+  0x316e8eef, 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
+  0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe, 0xb2bd0b28,
+  0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
+  0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f,
+  0x72076785, 0x05005713, 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38,
+  0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
+  0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
+  0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69,
+  0x616bffd3, 0x166ccf45, 0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2,
+  0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc,
+  0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
+  0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693,
+  0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94,
+  0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d
+};
+
+uint32_t
+crc32(uint32_t crc, const void *buf, size_t size) {
+  const uint8_t *p = buf;
+  crc = crc ^ 0xffffffffUL;
+  while (size--)
+    crc = crc32_tab[(crc ^ *p++) & 0xFF] ^ (crc >> 8);
+  return (crc ^ ~0U);
+}