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Diffstat (limited to 'src/libdwfl/relocate.c')
| -rw-r--r-- | src/libdwfl/relocate.c | 655 |
1 files changed, 655 insertions, 0 deletions
diff --git a/src/libdwfl/relocate.c b/src/libdwfl/relocate.c new file mode 100644 index 00000000..95206f47 --- /dev/null +++ b/src/libdwfl/relocate.c @@ -0,0 +1,655 @@ +/* Relocate debug information. + Copyright (C) 2005-2010 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 + <http://www.openinventionnetwork.com>. */ + +#include "libdwflP.h" + +typedef uint8_t GElf_Byte; + +/* Adjust *VALUE to add the load address of the SHNDX section. + We update the section header in place to cache the result. */ + +Dwfl_Error +internal_function +__libdwfl_relocate_value (Dwfl_Module *mod, Elf *elf, size_t *shstrndx, + Elf32_Word shndx, GElf_Addr *value) +{ + assert (mod->e_type == ET_REL); + + Elf_Scn *refscn = elf_getscn (elf, shndx); + GElf_Shdr refshdr_mem, *refshdr = gelf_getshdr (refscn, &refshdr_mem); + if (refshdr == NULL) + return DWFL_E_LIBELF; + + if (refshdr->sh_addr == 0 && (refshdr->sh_flags & SHF_ALLOC)) + { + /* This is a loaded section. Find its actual + address and update the section header. */ + + if (*shstrndx == SHN_UNDEF + && unlikely (elf_getshdrstrndx (elf, shstrndx) < 0)) + return DWFL_E_LIBELF; + + const char *name = elf_strptr (elf, *shstrndx, refshdr->sh_name); + if (unlikely (name == NULL)) + return DWFL_E_LIBELF; + + if ((*mod->dwfl->callbacks->section_address) (MODCB_ARGS (mod), + name, shndx, refshdr, + &refshdr->sh_addr)) + return CBFAIL; + + if (refshdr->sh_addr == (Dwarf_Addr) -1l) + /* The callback indicated this section wasn't really loaded but we + don't really care. */ + refshdr->sh_addr = 0; /* Make no adjustment below. */ + + /* Update the in-core file's section header to show the final + load address (or unloadedness). This serves as a cache, + so we won't get here again for the same section. */ + if (likely (refshdr->sh_addr != 0) + && unlikely (! gelf_update_shdr (refscn, refshdr))) + return DWFL_E_LIBELF; + } + + if (refshdr->sh_flags & SHF_ALLOC) + /* Apply the adjustment. */ + *value += dwfl_adjusted_address (mod, refshdr->sh_addr); + + return DWFL_E_NOERROR; +} + + +/* Cache used by relocate_getsym. */ +struct reloc_symtab_cache +{ + Elf *symelf; + Elf_Data *symdata; + Elf_Data *symxndxdata; + Elf_Data *symstrdata; + size_t symshstrndx; + size_t strtabndx; +}; +#define RELOC_SYMTAB_CACHE(cache) \ + struct reloc_symtab_cache cache = \ + { NULL, NULL, NULL, NULL, SHN_UNDEF, SHN_UNDEF } + +/* This is just doing dwfl_module_getsym, except that we must always use + the symbol table in RELOCATED itself when it has one, not MOD->symfile. */ +static Dwfl_Error +relocate_getsym (Dwfl_Module *mod, + Elf *relocated, struct reloc_symtab_cache *cache, + int symndx, GElf_Sym *sym, GElf_Word *shndx) +{ + if (cache->symdata == NULL) + { + if (mod->symfile == NULL || mod->symfile->elf != relocated) + { + /* We have to look up the symbol table in the file we are + relocating, if it has its own. These reloc sections refer to + the symbol table in this file, and a symbol table in the main + file might not match. However, some tools did produce ET_REL + .debug files with relocs but no symtab of their own. */ + Elf_Scn *scn = NULL; + while ((scn = elf_nextscn (relocated, scn)) != NULL) + { + GElf_Shdr shdr_mem, *shdr = gelf_getshdr (scn, &shdr_mem); + if (shdr != NULL) + switch (shdr->sh_type) + { + default: + continue; + case SHT_SYMTAB: + cache->symelf = relocated; + cache->symdata = elf_getdata (scn, NULL); + cache->strtabndx = shdr->sh_link; + if (unlikely (cache->symdata == NULL)) + return DWFL_E_LIBELF; + break; + case SHT_SYMTAB_SHNDX: + cache->symxndxdata = elf_getdata (scn, NULL); + if (unlikely (cache->symxndxdata == NULL)) + return DWFL_E_LIBELF; + break; + } + if (cache->symdata != NULL && cache->symxndxdata != NULL) + break; + } + } + if (cache->symdata == NULL) + { + /* We might not have looked for a symbol table file yet, + when coming from __libdwfl_relocate_section. */ + if (unlikely (mod->symfile == NULL) + && unlikely (INTUSE(dwfl_module_getsymtab) (mod) < 0)) + return dwfl_errno (); + + /* The symbol table we have already cached is the one from + the file being relocated, so it's what we need. Or else + this is an ET_REL .debug file with no .symtab of its own; + the symbols refer to the section indices in the main file. */ + cache->symelf = mod->symfile->elf; + cache->symdata = mod->symdata; + cache->symxndxdata = mod->symxndxdata; + cache->symstrdata = mod->symstrdata; + } + } + + if (unlikely (gelf_getsymshndx (cache->symdata, cache->symxndxdata, + symndx, sym, shndx) == NULL)) + return DWFL_E_LIBELF; + + if (sym->st_shndx != SHN_XINDEX) + *shndx = sym->st_shndx; + + switch (sym->st_shndx) + { + case SHN_ABS: + case SHN_UNDEF: + return DWFL_E_NOERROR; + + case SHN_COMMON: + sym->st_value = 0; /* Value is size, not helpful. */ + return DWFL_E_NOERROR; + } + + return __libdwfl_relocate_value (mod, cache->symelf, &cache->symshstrndx, + *shndx, &sym->st_value); +} + +/* Handle an undefined symbol. We really only support ET_REL for Linux + kernel modules, and offline archives. The behavior of the Linux module + loader is very simple and easy to mimic. It only matches magically + exported symbols, and we match any defined symbols. But we get the same + answer except when the module's symbols are undefined and would prevent + it from being loaded. */ +static Dwfl_Error +resolve_symbol (Dwfl_Module *referer, struct reloc_symtab_cache *symtab, + GElf_Sym *sym, GElf_Word shndx) +{ + /* First we need its name. */ + if (sym->st_name != 0) + { + if (symtab->symstrdata == NULL) + { + /* Cache the strtab for this symtab. */ + assert (referer->symfile == NULL + || referer->symfile->elf != symtab->symelf); + symtab->symstrdata = elf_getdata (elf_getscn (symtab->symelf, + symtab->strtabndx), + NULL); + if (unlikely (symtab->symstrdata == NULL)) + return DWFL_E_LIBELF; + } + if (unlikely (sym->st_name >= symtab->symstrdata->d_size)) + return DWFL_E_BADSTROFF; + + const char *name = symtab->symstrdata->d_buf; + name += sym->st_name; + + for (Dwfl_Module *m = referer->dwfl->modulelist; m != NULL; m = m->next) + if (m != referer) + { + /* Get this module's symtab. + If we got a fresh error reading the table, report it. + If we just have no symbols in this module, no harm done. */ + if (m->symdata == NULL + && m->symerr == DWFL_E_NOERROR + && INTUSE(dwfl_module_getsymtab) (m) < 0 + && m->symerr != DWFL_E_NO_SYMTAB) + return m->symerr; + + for (size_t ndx = 1; ndx < m->syments; ++ndx) + { + sym = gelf_getsymshndx (m->symdata, m->symxndxdata, + ndx, sym, &shndx); + if (unlikely (sym == NULL)) + return DWFL_E_LIBELF; + if (sym->st_shndx != SHN_XINDEX) + shndx = sym->st_shndx; + + /* We are looking for a defined global symbol with a name. */ + if (shndx == SHN_UNDEF || shndx == SHN_COMMON + || GELF_ST_BIND (sym->st_info) == STB_LOCAL + || sym->st_name == 0) + continue; + + /* Get this candidate symbol's name. */ + if (unlikely (sym->st_name >= m->symstrdata->d_size)) + return DWFL_E_BADSTROFF; + const char *n = m->symstrdata->d_buf; + n += sym->st_name; + + /* Does the name match? */ + if (strcmp (name, n)) + continue; + + /* We found it! */ + if (shndx == SHN_ABS) /* XXX maybe should apply bias? */ + return DWFL_E_NOERROR; + + if (m->e_type != ET_REL) + { + sym->st_value = dwfl_adjusted_st_value (m, sym->st_value); + return DWFL_E_NOERROR; + } + + /* In an ET_REL file, the symbol table values are relative + to the section, not to the module's load base. */ + size_t symshstrndx = SHN_UNDEF; + return __libdwfl_relocate_value (m, m->symfile->elf, + &symshstrndx, + shndx, &sym->st_value); + } + } + } + + return DWFL_E_RELUNDEF; +} + +static Dwfl_Error +relocate_section (Dwfl_Module *mod, Elf *relocated, const GElf_Ehdr *ehdr, + size_t shstrndx, struct reloc_symtab_cache *reloc_symtab, + Elf_Scn *scn, GElf_Shdr *shdr, + Elf_Scn *tscn, bool debugscn, bool partial) +{ + /* First, fetch the name of the section these relocations apply to. */ + GElf_Shdr tshdr_mem; + GElf_Shdr *tshdr = gelf_getshdr (tscn, &tshdr_mem); + const char *tname = elf_strptr (relocated, shstrndx, tshdr->sh_name); + if (tname == NULL) + return DWFL_E_LIBELF; + + if (unlikely (tshdr->sh_type == SHT_NOBITS) || unlikely (tshdr->sh_size == 0)) + /* No contents to relocate. */ + return DWFL_E_NOERROR; + + if (debugscn && ! ebl_debugscn_p (mod->ebl, tname)) + /* This relocation section is not for a debugging section. + Nothing to do here. */ + return DWFL_E_NOERROR; + + /* Fetch the section data that needs the relocations applied. */ + Elf_Data *tdata = elf_rawdata (tscn, NULL); + if (tdata == NULL) + return DWFL_E_LIBELF; + + /* Apply one relocation. Returns true for any invalid data. */ + Dwfl_Error relocate (GElf_Addr offset, const GElf_Sxword *addend, + int rtype, int symndx) + { + /* First see if this is a reloc we can handle. + If we are skipping it, don't bother resolving the symbol. */ + + if (unlikely (rtype == 0)) + /* In some odd situations, the linker can leave R_*_NONE relocs + behind. This is probably bogus ld -r behavior, but the only + cases it's known to appear in are harmless: DWARF data + referring to addresses in a section that has been discarded. + So we just pretend it's OK without further relocation. */ + return DWFL_E_NOERROR; + + Elf_Type type = ebl_reloc_simple_type (mod->ebl, rtype); + if (unlikely (type == ELF_T_NUM)) + return DWFL_E_BADRELTYPE; + + /* First, resolve the symbol to an absolute value. */ + GElf_Addr value; + + if (symndx == STN_UNDEF) + /* When strip removes a section symbol referring to a + section moved into the debuginfo file, it replaces + that symbol index in relocs with STN_UNDEF. We + don't actually need the symbol, because those relocs + are always references relative to the nonallocated + debugging sections, which start at zero. */ + value = 0; + else + { + GElf_Sym sym; + GElf_Word shndx; + Dwfl_Error error = relocate_getsym (mod, relocated, reloc_symtab, + symndx, &sym, &shndx); + if (unlikely (error != DWFL_E_NOERROR)) + return error; + + if (shndx == SHN_UNDEF || shndx == SHN_COMMON) + { + /* Maybe we can figure it out anyway. */ + error = resolve_symbol (mod, reloc_symtab, &sym, shndx); + if (error != DWFL_E_NOERROR + && !(error == DWFL_E_RELUNDEF && shndx == SHN_COMMON)) + return error; + } + + value = sym.st_value; + } + + /* These are the types we can relocate. */ +#define TYPES DO_TYPE (BYTE, Byte); DO_TYPE (HALF, Half); \ + DO_TYPE (WORD, Word); DO_TYPE (SWORD, Sword); \ + DO_TYPE (XWORD, Xword); DO_TYPE (SXWORD, Sxword) + size_t size; + switch (type) + { +#define DO_TYPE(NAME, Name) \ + case ELF_T_##NAME: \ + size = sizeof (GElf_##Name); \ + break + TYPES; +#undef DO_TYPE + default: + return DWFL_E_BADRELTYPE; + } + + if (offset + size > tdata->d_size) + return DWFL_E_BADRELOFF; + +#define DO_TYPE(NAME, Name) GElf_##Name Name; + union { TYPES; } tmpbuf; +#undef DO_TYPE + Elf_Data tmpdata = + { + .d_type = type, + .d_buf = &tmpbuf, + .d_size = size, + .d_version = EV_CURRENT, + }; + Elf_Data rdata = + { + .d_type = type, + .d_buf = tdata->d_buf + offset, + .d_size = size, + .d_version = EV_CURRENT, + }; + + /* XXX check for overflow? */ + if (addend) + { + /* For the addend form, we have the value already. */ + value += *addend; + switch (type) + { +#define DO_TYPE(NAME, Name) \ + case ELF_T_##NAME: \ + tmpbuf.Name = value; \ + break + TYPES; +#undef DO_TYPE + default: + abort (); + } + } + else + { + /* Extract the original value and apply the reloc. */ + Elf_Data *d = gelf_xlatetom (relocated, &tmpdata, &rdata, + ehdr->e_ident[EI_DATA]); + if (d == NULL) + return DWFL_E_LIBELF; + assert (d == &tmpdata); + switch (type) + { +#define DO_TYPE(NAME, Name) \ + case ELF_T_##NAME: \ + tmpbuf.Name += (GElf_##Name) value; \ + break + TYPES; +#undef DO_TYPE + default: + abort (); + } + } + + /* Now convert the relocated datum back to the target + format. This will write into rdata.d_buf, which + points into the raw section data being relocated. */ + Elf_Data *s = gelf_xlatetof (relocated, &rdata, &tmpdata, + ehdr->e_ident[EI_DATA]); + if (s == NULL) + return DWFL_E_LIBELF; + assert (s == &rdata); + + /* We have applied this relocation! */ + return DWFL_E_NOERROR; + } + + /* Fetch the relocation section and apply each reloc in it. */ + Elf_Data *reldata = elf_getdata (scn, NULL); + if (reldata == NULL) + return DWFL_E_LIBELF; + + Dwfl_Error result = DWFL_E_NOERROR; + bool first_badreltype = true; + inline void check_badreltype (void) + { + if (first_badreltype) + { + first_badreltype = false; + if (ebl_get_elfmachine (mod->ebl) == EM_NONE) + /* This might be because ebl_openbackend failed to find + any libebl_CPU.so library. Diagnose that clearly. */ + result = DWFL_E_UNKNOWN_MACHINE; + } + } + + size_t nrels = shdr->sh_size / shdr->sh_entsize; + size_t complete = 0; + if (shdr->sh_type == SHT_REL) + for (size_t relidx = 0; !result && relidx < nrels; ++relidx) + { + GElf_Rel rel_mem, *r = gelf_getrel (reldata, relidx, &rel_mem); + if (r == NULL) + return DWFL_E_LIBELF; + result = relocate (r->r_offset, NULL, + GELF_R_TYPE (r->r_info), + GELF_R_SYM (r->r_info)); + check_badreltype (); + if (partial) + switch (result) + { + case DWFL_E_NOERROR: + /* We applied the relocation. Elide it. */ + memset (&rel_mem, 0, sizeof rel_mem); + gelf_update_rel (reldata, relidx, &rel_mem); + ++complete; + break; + case DWFL_E_BADRELTYPE: + case DWFL_E_RELUNDEF: + /* We couldn't handle this relocation. Skip it. */ + result = DWFL_E_NOERROR; + break; + default: + break; + } + } + else + for (size_t relidx = 0; !result && relidx < nrels; ++relidx) + { + GElf_Rela rela_mem, *r = gelf_getrela (reldata, relidx, + &rela_mem); + if (r == NULL) + return DWFL_E_LIBELF; + result = relocate (r->r_offset, &r->r_addend, + GELF_R_TYPE (r->r_info), + GELF_R_SYM (r->r_info)); + check_badreltype (); + if (partial) + switch (result) + { + case DWFL_E_NOERROR: + /* We applied the relocation. Elide it. */ + memset (&rela_mem, 0, sizeof rela_mem); + gelf_update_rela (reldata, relidx, &rela_mem); + ++complete; + break; + case DWFL_E_BADRELTYPE: + case DWFL_E_RELUNDEF: + /* We couldn't handle this relocation. Skip it. */ + result = DWFL_E_NOERROR; + break; + default: + break; + } + } + + if (likely (result == DWFL_E_NOERROR)) + { + if (!partial || complete == nrels) + /* Mark this relocation section as being empty now that we have + done its work. This affects unstrip -R, so e.g. it emits an + empty .rela.debug_info along with a .debug_info that has + already been fully relocated. */ + nrels = 0; + else if (complete != 0) + { + /* We handled some of the relocations but not all. + We've zeroed out the ones we processed. + Now remove them from the section. */ + + size_t next = 0; + if (shdr->sh_type == SHT_REL) + for (size_t relidx = 0; relidx < nrels; ++relidx) + { + GElf_Rel rel_mem; + GElf_Rel *r = gelf_getrel (reldata, relidx, &rel_mem); + if (r->r_info != 0 || r->r_offset != 0) + { + if (next != relidx) + gelf_update_rel (reldata, next, r); + ++next; + } + } + else + for (size_t relidx = 0; relidx < nrels; ++relidx) + { + GElf_Rela rela_mem; + GElf_Rela *r = gelf_getrela (reldata, relidx, &rela_mem); + if (r->r_info != 0 || r->r_offset != 0 || r->r_addend != 0) + { + if (next != relidx) + gelf_update_rela (reldata, next, r); + ++next; + } + } + nrels = next; + } + + shdr->sh_size = reldata->d_size = nrels * shdr->sh_entsize; + gelf_update_shdr (scn, shdr); + } + + return result; +} + +Dwfl_Error +internal_function +__libdwfl_relocate (Dwfl_Module *mod, Elf *debugfile, bool debug) +{ + assert (mod->e_type == ET_REL); + + GElf_Ehdr ehdr_mem; + const GElf_Ehdr *ehdr = gelf_getehdr (debugfile, &ehdr_mem); + if (ehdr == NULL) + return DWFL_E_LIBELF; + + size_t d_shstrndx; + if (elf_getshdrstrndx (debugfile, &d_shstrndx) < 0) + return DWFL_E_LIBELF; + + RELOC_SYMTAB_CACHE (reloc_symtab); + + /* Look at each section in the debuginfo file, and process the + relocation sections for debugging sections. */ + Dwfl_Error result = DWFL_E_NOERROR; + Elf_Scn *scn = NULL; + while (result == DWFL_E_NOERROR + && (scn = elf_nextscn (debugfile, scn)) != NULL) + { + GElf_Shdr shdr_mem; + GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem); + + if ((shdr->sh_type == SHT_REL || shdr->sh_type == SHT_RELA) + && shdr->sh_size != 0) + { + /* It's a relocation section. */ + + Elf_Scn *tscn = elf_getscn (debugfile, shdr->sh_info); + if (unlikely (tscn == NULL)) + result = DWFL_E_LIBELF; + else + result = relocate_section (mod, debugfile, ehdr, d_shstrndx, + &reloc_symtab, scn, shdr, tscn, + debug, !debug); + } + } + + return result; +} + +Dwfl_Error +internal_function +__libdwfl_relocate_section (Dwfl_Module *mod, Elf *relocated, + Elf_Scn *relocscn, Elf_Scn *tscn, bool partial) +{ + GElf_Ehdr ehdr_mem; + GElf_Shdr shdr_mem; + + RELOC_SYMTAB_CACHE (reloc_symtab); + + size_t shstrndx; + if (elf_getshdrstrndx (relocated, &shstrndx) < 0) + return DWFL_E_LIBELF; + + return (__libdwfl_module_getebl (mod) + ?: relocate_section (mod, relocated, + gelf_getehdr (relocated, &ehdr_mem), shstrndx, + &reloc_symtab, + relocscn, gelf_getshdr (relocscn, &shdr_mem), + tscn, false, partial)); +} |