X-Git-Url: http://info.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/blobdiff_plain/3cf8dfbfab4595b3e7ae85d3cd89ce9dbcdd7a24..83339f7ee7c47e16583c280915b853a98c59b923:/src/mc/mc_dwarf.cpp diff --git a/src/mc/mc_dwarf.cpp b/src/mc/mc_dwarf.cpp index 5e1b5e5f7b..dc7736a29a 100644 --- a/src/mc/mc_dwarf.cpp +++ b/src/mc/mc_dwarf.cpp @@ -9,7 +9,9 @@ #include #include +#include +#include #include #define DW_LANG_Objc DW_LANG_ObjC /* fix spelling error in older dwarf.h */ #include @@ -978,9 +980,8 @@ static void MC_dwarf_handle_die(simgrid::mc::ObjectInformation* info, Dwarf_Die } static -Elf64_Half MC_dwarf_elf_type(Dwarf* dwarf) +Elf64_Half get_type(Elf* elf) { - Elf* elf = dwarf_getelf(dwarf); Elf64_Ehdr* ehdr64 = elf64_getehdr(elf); if (ehdr64) return ehdr64->e_type; @@ -990,28 +991,9 @@ Elf64_Half MC_dwarf_elf_type(Dwarf* dwarf) xbt_die("Could not get ELF heeader"); } -/** \brief Populate the debugging informations of the given ELF object - * - * Read the DWARf information of the EFFL object and populate the - * lists of types, variables, functions. - */ static -void MC_dwarf_get_variables(simgrid::mc::ObjectInformation* info) +void read_dwarf_info(simgrid::mc::ObjectInformation* info, Dwarf* dwarf) { - int fd = open(info->file_name.c_str(), O_RDONLY); - if (fd < 0) - xbt_die("Could not open file %s", info->file_name.c_str()); - Dwarf *dwarf = dwarf_begin(fd, DWARF_C_READ); - if (dwarf == nullptr) - xbt_die("Missing debugging information in %s\n" - "Your program and its dependencies must have debugging information.\n" - "You might want to recompile with -g or install the suitable debugging package.\n", - info->file_name.c_str()); - - Elf64_Half elf_type = MC_dwarf_elf_type(dwarf); - if (elf_type == ET_EXEC) - info->flags |= simgrid::mc::ObjectInformation::Executable; - // For each compilation unit: Dwarf_Off offset = 0; Dwarf_Off next_offset = 0; @@ -1024,9 +1006,195 @@ void MC_dwarf_get_variables(simgrid::mc::ObjectInformation* info) MC_dwarf_handle_children(info, &unit_die, &unit_die, nullptr, NULL); offset = next_offset; } +} + +/** Get the build-id (NT_GNU_BUILD_ID) from the ELF file + * + * This build-id may is used to locate an external debug (DWARF) file + * for this ELF file. + * + * @param elf libelf handle for an ELF file + * @return build-id for this ELF file (or an empty vector if none is found) + */ +static +std::vector get_build_id(Elf* elf) +{ + size_t phnum; + if (elf_getphdrnum (elf, &phnum) != 0) + xbt_die("Could not read program headers"); + + // Iterate over the program headers and find the PT_NOTE ones: + for (size_t i = 0; i < phnum; ++i) { + GElf_Phdr phdr_temp; + GElf_Phdr *phdr = gelf_getphdr(elf, i, &phdr_temp); + if (phdr->p_type != PT_NOTE) + continue; + + Elf_Data* data = elf_getdata_rawchunk(elf, phdr->p_offset, phdr->p_filesz, ELF_T_NHDR); + + // Iterate over the notes and find the NT_GNU_BUILD_ID one: + size_t pos = 0; + while (1) { + GElf_Nhdr nhdr; + 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): + 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: + char* start = (char*) data->d_buf + desc_pos; + char* end = (char*) start + nhdr.n_descsz; + return std::vector(start, end); + + } + } + + } + return std::vector(); +} + +static char hexdigits[16] = { + '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', + 'a', 'b', 'c', 'd', 'e', 'f' +}; + +/** Binary data to hexadecimal */ +static inline +std::array to_hex(std::uint8_t byte) +{ + // Horrid double braces! + // Apparently, this is needed in C++11 (not in C++14). + return { { hexdigits[byte >> 4], hexdigits[byte & 0xF] } }; +} + +/** Binary data to hexadecimal */ +static +std::string to_hex(const char* data, std::size_t count) +{ + std::string res; + res.resize(2*count); + for (std::size_t i = 0; i < count; i++) { + std::array hex_byte = to_hex(data[i]); + for (int j = 0; j < 2; ++j) + res[2 * i + j] = hex_byte[j]; + } + return std::move(res); +} + +/** Binary data to hexadecimal */ +static +std::string to_hex(std::vector const& data) +{ + return to_hex(data.data(), data.size()); +} + +/** Base directories for external debug files */ +const char* debug_paths[] = { + "/usr/lib/debug/", + "/usr/local/lib/debug/", +}; + +/** Locate an external debug file from the NT_GNU_BUILD_ID + * + * This is one of the mechanisms used for + * [separate debug files](https://sourceware.org/gdb/onlinedocs/gdb/Separate-Debug-Files.html). + */ +static +std::string find_by_build_id(std::vector id) +{ + std::string filename; + for (const char* debug_path : debug_paths) { + filename = debug_path; + filename += ".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) + return std::move(filename); + } + return std::string(); +} + +/** \brief Populate the debugging informations of the given ELF object + * + * Read the DWARf information of the EFFL object and populate the + * lists of types, variables, functions. + */ +static +void MC_dwarf_get_variables(simgrid::mc::ObjectInformation* info) +{ + if (elf_version(EV_CURRENT) == EV_NONE) + xbt_die("libelf initialization error"); + + // Open the ELF file: + int fd = open(info->file_name.c_str(), O_RDONLY); + if (fd < 0) + 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"); + Elf_Kind kind = elf_kind(elf); + if (kind != ELF_K_ELF) + xbt_die("Not an ELF file 2"); + + // Remember if this is a `ET_EXEC` (fixed location) or `ET_DYN` (relocatable): + Elf64_Half type = get_type(elf); + if (type == ET_EXEC) + info->flags |= simgrid::mc::ObjectInformation::Executable; + // Read DWARF debug information in the file: + Dwarf* dwarf = dwarf_begin_elf (elf, DWARF_C_READ, nullptr); + if (dwarf != nullptr) { + read_dwarf_info(info, dwarf); + dwarf_end(dwarf); + elf_end(elf); + close(fd); + return; + } dwarf_end(dwarf); - close(fd); + + // If there was no DWARF in the file, try to find it in a separate file + // with NT_GNU_BUILD_ID: + std::vector build_id = get_build_id(elf); + if (!build_id.empty()) { + elf_end(elf); + close(fd); + + // Find the debug file using the build id: + 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" + "You might want to install the suitable debugging package.\n", + info->file_name.c_str(), hex.c_str()); + } + + // Load the DWARF info from this file: + XBT_DEBUG("Load DWARF for %s from %s", + info->file_name.c_str(), debug_file.c_str()); + fd = open(debug_file.c_str(), O_RDONLY); + if (fd < 0) + xbt_die("Could not open file %s", debug_file.c_str()); + Dwarf* dwarf = dwarf_begin(fd, DWARF_C_READ); + if (dwarf == nullptr) + xbt_die("No DWARF info in %s for %s", + debug_file.c_str(), info->file_name.c_str()); + read_dwarf_info(info, dwarf); + dwarf_end(dwarf); + close(fd); + return; + } + + // TODO, try to find DWARF info using debug-link. + // Is this method really used anywhere? + + xbt_die("Debugging information not found for %s\n" + "Try recompiling with -g\n", + info->file_name.c_str()); } // ***** Functions index