if (klass == simgrid::dwarf::TagClass::Subprogram) {
const char *name = MC_dwarf_attr_integrate_string(die, DW_AT_name);
- if (ns)
+ if (name && ns)
frame.name = std::string(ns) + "::" + name;
else if (name)
frame.name = name;
static
std::vector<char> get_build_id(Elf* elf)
{
+#ifdef __linux
+ // Summary: the GNU build ID is stored in a ("GNU, NT_GNU_BUILD_ID) note
+ // found in a PT_NOTE entry in the program header table.
+
size_t phnum;
if (elf_getphdrnum (elf, &phnum) != 0)
xbt_die("Could not read program headers");
// Iterate over the notes and find the NT_GNU_BUILD_ID one:
size_t pos = 0;
- while (1) {
+ while (pos < data->d_size) {
GElf_Nhdr nhdr;
+ // Location of the name within Elf_Data:
size_t name_pos;
size_t desc_pos;
pos = gelf_getnote(data, pos, &nhdr, &name_pos, &desc_pos);
- // A note is identified by a name "GNU" and a integer type within
- // the namespace defined by this name (here NT_GNU_BUILD_ID):
+ // A build ID note is identified by the pair ("GNU", NT_GNU_BUILD_ID)
+ // (a namespace and a type within this namespace):
if (nhdr.n_type == NT_GNU_BUILD_ID
&& nhdr.n_namesz == sizeof("GNU")
&& memcmp((char*) data->d_buf + name_pos, "GNU", sizeof("GNU")) == 0) {
-
- // Found the NT_GNU_BUILD_ID note:
+ XBT_DEBUG("Found GNU/NT_GNU_BUILD_ID note");
char* start = (char*) data->d_buf + desc_pos;
char* end = (char*) start + nhdr.n_descsz;
return std::vector<char>(start, end);
-
}
}
}
+#endif
return std::vector<char>();
}
* This is one of the mechanisms used for
* [separate debug files](https://sourceware.org/gdb/onlinedocs/gdb/Separate-Debug-Files.html).
*/
+// Example:
+// /usr/lib/debug/.build-id/0b/dc77f1c29aea2b14ff5acd9a19ab3175ffdeae.debug
static
std::string find_by_build_id(std::vector<char> id)
{
std::string filename;
+ std::string hex = to_hex(id);
for (const char* debug_path : debug_paths) {
- filename = debug_path;
- filename += ".build-id/" + to_hex(id.data(), 1) + '/'
+ // Example:
+ filename = std::string(debug_path) + ".build-id/"
+ + to_hex(id.data(), 1) + '/'
+ to_hex(id.data() + 1, id.size() - 1) + ".debug";
XBT_DEBUG("Checking debug file: %s", filename.c_str());
- if (access(filename.c_str(), F_OK) == 0)
+ if (access(filename.c_str(), F_OK) == 0) {
+ XBT_DEBUG("Found debug file: %s\n", hex.c_str());
return filename;
+ }
}
+ XBT_DEBUG("Not debuf info found for build ID %s\n", hex.data());
return std::string();
}
* lists of types, variables, functions.
*/
static
-void MC_dwarf_get_variables(simgrid::mc::ObjectInformation* info)
+void MC_load_dwarf(simgrid::mc::ObjectInformation* info)
{
if (elf_version(EV_CURRENT) == EV_NONE)
xbt_die("libelf initialization error");
xbt_die("Could not open file %s", info->file_name.c_str());
Elf* elf = elf_begin(fd, ELF_C_READ, nullptr);
if (elf == nullptr)
- xbt_die("Not an ELF file 1");
+ xbt_die("Not an ELF file");
Elf_Kind kind = elf_kind(elf);
if (kind != ELF_K_ELF)
- xbt_die("Not an ELF file 2");
+ xbt_die("Not an ELF file");
- // Remember if this is a `ET_EXEC` (fixed location) or `ET_DYN` (relocatable):
+ // Remember if this is a `ET_EXEC` (fixed location) or `ET_DYN`:
Elf64_Half type = get_type(elf);
if (type == ET_EXEC)
info->flags |= simgrid::mc::ObjectInformation::Executable;
}
dwarf_end(dwarf);
- // If there was no DWARF in the file, try to find it in a separate file
- // with NT_GNU_BUILD_ID:
+ // If there was no DWARF in the file, try to find it in a separate file.
+ // Different methods might be used to store the DWARF informations:
+ // * GNU NT_GNU_BUILD_ID;
+ // * .gnu_debuglink.
+ // See https://sourceware.org/gdb/onlinedocs/gdb/Separate-Debug-Files.html
+ // for reference of what we are doing.
+
+ // Try with NT_GNU_BUILD_ID: we find the build ID in the ELF file and then
+ // use this ID to find the file in some known locations in the filesystem.
std::vector<char> build_id = get_build_id(elf);
if (!build_id.empty()) {
elf_end(elf);
std::string debug_file = find_by_build_id(build_id);
if (debug_file.empty()) {
std::string hex = to_hex(build_id);
- xbt_die(
- "Missing debug info for %s with build-id %s\n"
+ xbt_die("Missing debug info for %s with build-id %s\n"
"You might want to install the suitable debugging package.\n",
info->file_name.c_str(), hex.c_str());
}
return;
}
- // TODO, try to find DWARF info using debug-link.
- // Is this method really used anywhere?
+ // TODO, try to find DWARF info using .gnu_debuglink.
+ elf_end(elf);
+ close(fd);
xbt_die("Debugging information not found for %s\n"
"Try recompiling with -g\n",
info->file_name.c_str());
std::make_shared<simgrid::mc::ObjectInformation>();
result->file_name = name;
simgrid::mc::find_object_address(maps, result.get());
- MC_dwarf_get_variables(result.get());
+ MC_load_dwarf(result.get());
MC_post_process_variables(result.get());
MC_post_process_types(result.get());
for (auto& entry : result.get()->subprograms)