/* Recover relocatibility for addresses computed from debug information. Copyright (C) 2005-2009 Red Hat, Inc. This file is part of Red Hat elfutils. Red Hat elfutils is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; version 2 of the License. Red Hat elfutils is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with Red Hat elfutils; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301 USA. In addition, as a special exception, Red Hat, Inc. gives You the additional right to link the code of Red Hat elfutils with code licensed under any Open Source Initiative certified open source license (http://www.opensource.org/licenses/index.php) which requires the distribution of source code with any binary distribution and to distribute linked combinations of the two. Non-GPL Code permitted under this exception must only link to the code of Red Hat elfutils through those well defined interfaces identified in the file named EXCEPTION found in the source code files (the "Approved Interfaces"). The files of Non-GPL Code may instantiate templates or use macros or inline functions from the Approved Interfaces without causing the resulting work to be covered by the GNU General Public License. Only Red Hat, Inc. may make changes or additions to the list of Approved Interfaces. Red Hat's grant of this exception is conditioned upon your not adding any new exceptions. If you wish to add a new Approved Interface or exception, please contact Red Hat. You must obey the GNU General Public License in all respects for all of the Red Hat elfutils code and other code used in conjunction with Red Hat elfutils except the Non-GPL Code covered by this exception. If you modify this file, you may extend this exception to your version of the file, but you are not obligated to do so. If you do not wish to provide this exception without modification, you must delete this exception statement from your version and license this file solely under the GPL without exception. Red Hat elfutils is an included package of the Open Invention Network. An included package of the Open Invention Network is a package for which Open Invention Network licensees cross-license their patents. No patent license is granted, either expressly or impliedly, by designation as an included package. Should you wish to participate in the Open Invention Network licensing program, please visit www.openinventionnetwork.com . */ #include "libdwflP.h" struct dwfl_relocation { size_t count; struct { Elf_Scn *scn; Elf_Scn *relocs; const char *name; GElf_Addr start, end; } refs[0]; }; struct secref { struct secref *next; Elf_Scn *scn; Elf_Scn *relocs; const char *name; GElf_Addr start, end; }; static int compare_secrefs (const void *a, const void *b) { struct secref *const *p1 = a; struct secref *const *p2 = b; /* No signed difference calculation is correct here, since the terms are unsigned and could be more than INT64_MAX apart. */ if ((*p1)->start < (*p2)->start) return -1; if ((*p1)->start > (*p2)->start) return 1; return 0; } static int cache_sections (Dwfl_Module *mod) { struct secref *refs = NULL; size_t nrefs = 0; size_t shstrndx; if (unlikely (elf_getshdrstrndx (mod->main.elf, &shstrndx) < 0)) { elf_error: __libdwfl_seterrno (DWFL_E_LIBELF); return -1; } bool check_reloc_sections = false; Elf_Scn *scn = NULL; while ((scn = elf_nextscn (mod->main.elf, scn)) != NULL) { GElf_Shdr shdr_mem; GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem); if (shdr == NULL) goto elf_error; if ((shdr->sh_flags & SHF_ALLOC) && shdr->sh_addr == 0 && mod->e_type == ET_REL) { /* This section might not yet have been looked at. */ if (__libdwfl_relocate_value (mod, mod->main.elf, &shstrndx, elf_ndxscn (scn), &shdr->sh_addr) != DWFL_E_NOERROR) continue; shdr = gelf_getshdr (scn, &shdr_mem); if (unlikely (shdr == NULL)) goto elf_error; } if (shdr->sh_flags & SHF_ALLOC) { const char *name = elf_strptr (mod->main.elf, shstrndx, shdr->sh_name); if (unlikely (name == NULL)) goto elf_error; struct secref *newref = alloca (sizeof *newref); newref->scn = scn; newref->relocs = NULL; newref->name = name; newref->start = shdr->sh_addr + mod->main.bias; newref->end = newref->start + shdr->sh_size; newref->next = refs; refs = newref; ++nrefs; } if (mod->e_type == ET_REL && shdr->sh_size != 0 && (shdr->sh_type == SHT_REL || shdr->sh_type == SHT_RELA) && mod->dwfl->callbacks->section_address != NULL) { if (shdr->sh_info < elf_ndxscn (scn)) { /* We've already looked at the section these relocs apply to. */ Elf_Scn *tscn = elf_getscn (mod->main.elf, shdr->sh_info); if (likely (tscn != NULL)) for (struct secref *sec = refs; sec != NULL; sec = sec->next) if (sec->scn == tscn) { sec->relocs = scn; break; } } else /* We'll have to do a second pass. */ check_reloc_sections = true; } } mod->reloc_info = malloc (offsetof (struct dwfl_relocation, refs[nrefs])); if (mod->reloc_info == NULL) { __libdwfl_seterrno (DWFL_E_NOMEM); return -1; } struct secref **sortrefs = alloca (nrefs * sizeof sortrefs[0]); for (size_t i = nrefs; i-- > 0; refs = refs->next) sortrefs[i] = refs; assert (refs == NULL); qsort (sortrefs, nrefs, sizeof sortrefs[0], &compare_secrefs); mod->reloc_info->count = nrefs; for (size_t i = 0; i < nrefs; ++i) { mod->reloc_info->refs[i].name = sortrefs[i]->name; mod->reloc_info->refs[i].scn = sortrefs[i]->scn; mod->reloc_info->refs[i].relocs = sortrefs[i]->relocs; mod->reloc_info->refs[i].start = sortrefs[i]->start; mod->reloc_info->refs[i].end = sortrefs[i]->end; } if (unlikely (check_reloc_sections)) { /* There was a reloc section that preceded its target section. So we have to scan again now that we have cached all the possible target sections we care about. */ scn = NULL; while ((scn = elf_nextscn (mod->main.elf, scn)) != NULL) { GElf_Shdr shdr_mem; GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem); if (shdr == NULL) goto elf_error; if (shdr->sh_size != 0 && (shdr->sh_type == SHT_REL || shdr->sh_type == SHT_RELA)) { Elf_Scn *tscn = elf_getscn (mod->main.elf, shdr->sh_info); if (likely (tscn != NULL)) for (size_t i = 0; i < nrefs; ++i) if (mod->reloc_info->refs[i].scn == tscn) { mod->reloc_info->refs[i].relocs = scn; break; } } } } return nrefs; } int dwfl_module_relocations (Dwfl_Module *mod) { if (mod == NULL) return -1; if (mod->reloc_info != NULL) return mod->reloc_info->count; switch (mod->e_type) { case ET_REL: return cache_sections (mod); case ET_DYN: return 1; case ET_EXEC: assert (mod->main.bias == 0); assert (mod->debug.bias == 0); break; } return 0; } const char * dwfl_module_relocation_info (Dwfl_Module *mod, unsigned int idx, Elf32_Word *shndxp) { if (mod == NULL) return NULL; switch (mod->e_type) { case ET_REL: break; case ET_DYN: if (idx != 0) return NULL; if (shndxp) *shndxp = SHN_ABS; return ""; default: return NULL; } if (unlikely (mod->reloc_info == NULL) && cache_sections (mod) < 0) return NULL; struct dwfl_relocation *sections = mod->reloc_info; if (idx >= sections->count) return NULL; if (shndxp) *shndxp = elf_ndxscn (sections->refs[idx].scn); return sections->refs[idx].name; } /* Check that MOD is valid and make sure its relocation has been done. */ static bool check_module (Dwfl_Module *mod) { if (INTUSE(dwfl_module_getsymtab) (mod) < 0) { Dwfl_Error error = dwfl_errno (); if (error != DWFL_E_NO_SYMTAB) { __libdwfl_seterrno (error); return true; } } if (mod->dw == NULL) { Dwarf_Addr bias; if (INTUSE(dwfl_module_getdwarf) (mod, &bias) == NULL) { Dwfl_Error error = dwfl_errno (); if (error != DWFL_E_NO_DWARF) { __libdwfl_seterrno (error); return true; } } } return false; } /* Find the index in MOD->reloc_info.refs containing *ADDR. */ static int find_section (Dwfl_Module *mod, Dwarf_Addr *addr) { if (unlikely (mod->reloc_info == NULL) && cache_sections (mod) < 0) return -1; struct dwfl_relocation *sections = mod->reloc_info; /* The sections are sorted by address, so we can use binary search. */ size_t l = 0, u = sections->count; while (l < u) { size_t idx = (l + u) / 2; if (*addr < sections->refs[idx].start) u = idx; else if (*addr > sections->refs[idx].end) l = idx + 1; else { /* Consider the limit of a section to be inside it, unless it's inside the next one. A section limit address can appear in line records. */ if (*addr == sections->refs[idx].end && idx < sections->count && *addr == sections->refs[idx + 1].start) ++idx; *addr -= sections->refs[idx].start; return idx; } } __libdwfl_seterrno (DWFL_E (LIBDW, DWARF_E_NO_MATCH)); return -1; } int dwfl_module_relocate_address (Dwfl_Module *mod, Dwarf_Addr *addr) { if (unlikely (check_module (mod))) return -1; switch (mod->e_type) { case ET_REL: return find_section (mod, addr); case ET_DYN: /* All relative to first and only relocation base: module start. */ *addr -= mod->low_addr; break; default: /* Already absolute, dwfl_module_relocations returned zero. We shouldn't really have been called, but it's a harmless no-op. */ break; } return 0; } INTDEF (dwfl_module_relocate_address) Elf_Scn * dwfl_module_address_section (Dwfl_Module *mod, Dwarf_Addr *address, Dwarf_Addr *bias) { if (check_module (mod)) return NULL; int idx = find_section (mod, address); if (idx < 0) return NULL; if (mod->reloc_info->refs[idx].relocs != NULL) { assert (mod->e_type == ET_REL); Elf_Scn *tscn = mod->reloc_info->refs[idx].scn; Elf_Scn *relocscn = mod->reloc_info->refs[idx].relocs; Dwfl_Error result = __libdwfl_relocate_section (mod, mod->main.elf, relocscn, tscn, true); if (likely (result == DWFL_E_NOERROR)) mod->reloc_info->refs[idx].relocs = NULL; else { __libdwfl_seterrno (result); return NULL; } } *bias = mod->main.bias; return mod->reloc_info->refs[idx].scn; } INTDEF (dwfl_module_address_section)