Hi Mark, I tried to use the program you showed me (attached below) which gets a list of source files from DWARF by calling dwarf_getsrcfiles from libdw. The dwarf_getsrcfiles function calls the dwarf_getsrclines function, which uses stack (alloca) to store intermediate data when reading/processing .debug_lines. Using stack this way doesn't scale, the program receives SIGSEGV for stack overflow when trying to process real debug files.
$ ./dwarfsrcfiles /usr/lib/debug/usr/bin/enfuse.debug Segmentation fault (core dumped) The reason is that ./dwarfsrcfiles needs approx. 15 MB on stack to process enfuse.debug (37MB, from enblend-debuginfo Fedora 14 package). $ ulimit -a | grep stack stack size (kbytes, -s) 8192 When I increase the stack size, it works as expected: $ valgrind --main-stacksize=16000000 ./dwarfsrcfiles /usr/lib/debug/usr/bin/enfuse.debug One could increase the stack size limit permanently on a machine, but it doesn't seem to be the right solution: there are even bigger debuginfo files in Fedora today, and the code size (=> dwarf size) is growing over years, while the default stack size limit not so much. I guess that most of the stack is used for storing lines in the NEW_LINE macro in dwarf_getsrclines. You might want to consider using the heap there. Kind regards, Karel Klic
// dwarfsrcfiles.c - Get source files associated with the dwarf in a elf file. // gcc -Wall -g -O2 -lelf -ldw -o dwarfsrcfiles dwarfsrcfiles.c // // Copyright (C) 2011, Mark Wielaard <[email protected]> // // This file is free software. You can redistribute it and/or modify // it under the terms of the GNU General Public License (GPL); either // version 2, or (at your option) any later version. #include <argp.h> #include <error.h> #include <stdio.h> #include <dwarf.h> #include <elfutils/libdw.h> #include <elfutils/libdwfl.h> static int process_cu (Dwarf_Die *cu_die) { Dwarf_Attribute attr; const char *name; const char *dir = NULL; Dwarf_Files *files; size_t n; int i; if (dwarf_tag (cu_die) != DW_TAG_compile_unit) { error (0, 0, "DIE isn't a compile unit"); return -1; } if (dwarf_attr (cu_die, DW_AT_name, &attr) == NULL) { error (0, 0, "CU doesn't have a DW_AT_name"); return -1; } name = dwarf_formstring (&attr); if (name == NULL) { error (0, 0, "Couldn't get DW_AT_name as string, %s", dwarf_errmsg (-1)); return -1; } if (dwarf_attr (cu_die, DW_AT_comp_dir, &attr) != NULL) { dir = dwarf_formstring (&attr); if (dir == NULL) { error (0, 0, "Couldn't get DW_AT_comp_die as string, %s", dwarf_errmsg (-1)); return -1; } } if (dir == NULL) printf ("%s\n", name); else printf ("%s/%s\n", dir, name); if (dwarf_getsrcfiles (cu_die, &files, &n) != 0) { error (0, 0, "Couldn't get CU file table, %s", dwarf_errmsg (-1)); return -1; } for (i = 1; i < n; i++) { const char *file = dwarf_filesrc (files, i, NULL, NULL); if (dir != NULL && file[0] != '/') printf ("\t%s/%s\n", dir, file); else printf ("\t%s\n", file); } return 0; } int main (int argc, char **argv) { char* args[3]; int res = 0; Dwfl *dwfl; Dwarf_Addr bias; if (argc != 2) error (-1, 0, "Usage %s <file>", argv[0]); // Pretend "dwarfsrcfiles -e <file>" was given, so we can use standard // dwfl argp parser to open the file for us and get our Dwfl. Useful // in case argument is an ET_REL file (like kernel modules). libdwfl // will fix up relocations for us. args[0] = argv[0]; args[1] = "-e"; args[2] = argv[1]; argp_parse (dwfl_standard_argp (), 3, args, 0, NULL, &dwfl); Dwarf_Die *cu = NULL; while ((cu = dwfl_nextcu (dwfl, cu, &bias)) != NULL) res |= process_cu (cu); dwfl_end (dwfl); return res; }
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