diff options
Diffstat (limited to 'libdwfl/dwfl_module_getdwarf.c')
| -rw-r--r-- | libdwfl/dwfl_module_getdwarf.c | 1358 |
1 files changed, 1358 insertions, 0 deletions
diff --git a/libdwfl/dwfl_module_getdwarf.c b/libdwfl/dwfl_module_getdwarf.c new file mode 100644 index 00000000..494407dd --- /dev/null +++ b/libdwfl/dwfl_module_getdwarf.c @@ -0,0 +1,1358 @@ +/* Find debugging and symbol information for a module in libdwfl. + Copyright (C) 2005-2012, 2014 Red Hat, Inc. + This file is part of elfutils. + + This file is free software; you can redistribute it and/or modify + it under the terms of either + + * the GNU Lesser General Public License as published by the Free + Software Foundation; either version 3 of the License, or (at + your option) any later version + + or + + * the GNU General Public License as published by the Free + Software Foundation; either version 2 of the License, or (at + your option) any later version + + or both in parallel, as here. + + 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 copies of the GNU General Public License and + the GNU Lesser General Public License along with this program. If + not, see <http://www.gnu.org/licenses/>. */ + +#include "libdwflP.h" +#include <inttypes.h> +#include <fcntl.h> +#include <string.h> +#include <unistd.h> +#include "../libdw/libdwP.h" /* DWARF_E_* values are here. */ +#include "../libelf/libelfP.h" + +static inline Dwfl_Error +open_elf_file (Elf **elf, int *fd, char **name) +{ + if (*elf == NULL) + { + /* CBFAIL uses errno if it's set, so clear it first in case we don't + set it with an open failure below. */ + errno = 0; + + /* If there was a pre-primed file name left that the callback left + behind, try to open that file name. */ + if (*fd < 0 && *name != NULL) + *fd = TEMP_FAILURE_RETRY (open64 (*name, O_RDONLY)); + + if (*fd < 0) + return CBFAIL; + + return __libdw_open_file (fd, elf, true, false); + } + else if (unlikely (elf_kind (*elf) != ELF_K_ELF)) + { + elf_end (*elf); + *elf = NULL; + close (*fd); + *fd = -1; + return DWFL_E_BADELF; + } + + /* Elf file already open and looks fine. */ + return DWFL_E_NOERROR; +} + +/* Open libelf FILE->fd and compute the load base of ELF as loaded in MOD. + When we return success, FILE->elf and FILE->vaddr are set up. */ +static inline Dwfl_Error +open_elf (Dwfl_Module *mod, struct dwfl_file *file) +{ + Dwfl_Error error = open_elf_file (&file->elf, &file->fd, &file->name); + if (error != DWFL_E_NOERROR) + return error; + + GElf_Ehdr ehdr_mem, *ehdr = gelf_getehdr (file->elf, &ehdr_mem); + if (ehdr == NULL) + { + elf_error: + elf_end (file->elf); + file->elf = NULL; + close (file->fd); + file->fd = -1; + return DWFL_E (LIBELF, elf_errno ()); + } + + if (ehdr->e_type != ET_REL) + { + /* In any non-ET_REL file, we compute the "synchronization address". + + We start with the address at the end of the first PT_LOAD + segment. When prelink converts REL to RELA in an ET_DYN + file, it expands the space between the beginning of the + segment and the actual code/data addresses. Since that + change wasn't made in the debug file, the distance from + p_vaddr to an address of interest (in an st_value or DWARF + data) now differs between the main and debug files. The + distance from address_sync to an address of interest remains + consistent. + + If there are no section headers at all (full stripping), then + the end of the first segment is a valid synchronization address. + This cannot happen in a prelinked file, since prelink itself + relies on section headers for prelinking and for undoing it. + (If you do full stripping on a prelinked file, then you get what + you deserve--you can neither undo the prelinking, nor expect to + line it up with a debug file separated before prelinking.) + + However, when prelink processes an ET_EXEC file, it can do + something different. There it juggles the "special" sections + (SHT_DYNSYM et al) to make space for the additional prelink + special sections. Sometimes it will do this by moving a special + section like .dynstr after the real program sections in the first + PT_LOAD segment--i.e. to the end. That changes the end address of + the segment, so it no longer lines up correctly and is not a valid + synchronization address to use. Because of this, we need to apply + a different prelink-savvy means to discover the synchronization + address when there is a separate debug file and a prelinked main + file. That is done in find_debuginfo, below. */ + + size_t phnum; + if (unlikely (elf_getphdrnum (file->elf, &phnum) != 0)) + goto elf_error; + + file->vaddr = file->address_sync = 0; + for (size_t i = 0; i < phnum; ++i) + { + GElf_Phdr ph_mem; + GElf_Phdr *ph = gelf_getphdr (file->elf, i, &ph_mem); + if (unlikely (ph == NULL)) + goto elf_error; + if (ph->p_type == PT_LOAD) + { + file->vaddr = ph->p_vaddr & -ph->p_align; + file->address_sync = ph->p_vaddr + ph->p_memsz; + break; + } + } + } + + /* We only want to set the module e_type explictly once, derived from + the main ELF file. (It might be changed for the kernel, because + that is special - see below.) open_elf is always called first for + the main ELF file, because both find_dw and find_symtab call + __libdwfl_getelf first to open the main file. So don't let debug + or aux files override the module e_type. The kernel heuristic + below could otherwise trigger for non-kernel/non-main files, since + their phdrs might not match the actual load addresses. */ + if (file == &mod->main) + { + mod->e_type = ehdr->e_type; + + /* Relocatable Linux kernels are ET_EXEC but act like ET_DYN. */ + if (mod->e_type == ET_EXEC && file->vaddr != mod->low_addr) + mod->e_type = ET_DYN; + } + else + assert (mod->main.elf != NULL); + + return DWFL_E_NOERROR; +} + +/* We have an authoritative build ID for this module MOD, so don't use + a file by name that doesn't match that ID. */ +static void +mod_verify_build_id (Dwfl_Module *mod) +{ + assert (mod->build_id_len > 0); + + switch (__builtin_expect (__libdwfl_find_build_id (mod, false, + mod->main.elf), 2)) + { + case 2: + /* Build ID matches as it should. */ + return; + + case -1: /* ELF error. */ + mod->elferr = INTUSE(dwfl_errno) (); + break; + + case 0: /* File has no build ID note. */ + case 1: /* FIle has a build ID that does not match. */ + mod->elferr = DWFL_E_WRONG_ID_ELF; + break; + + default: + abort (); + } + + /* We get here when it was the right ELF file. Clear it out. */ + elf_end (mod->main.elf); + mod->main.elf = NULL; + if (mod->main.fd >= 0) + { + close (mod->main.fd); + mod->main.fd = -1; + } +} + +/* Find the main ELF file for this module and open libelf on it. + When we return success, MOD->main.elf and MOD->main.bias are set up. */ +void +internal_function +__libdwfl_getelf (Dwfl_Module *mod) +{ + if (mod->main.elf != NULL /* Already done. */ + || mod->elferr != DWFL_E_NOERROR) /* Cached failure. */ + return; + + mod->main.fd = (*mod->dwfl->callbacks->find_elf) (MODCB_ARGS (mod), + &mod->main.name, + &mod->main.elf); + const bool fallback = mod->main.elf == NULL && mod->main.fd < 0; + mod->elferr = open_elf (mod, &mod->main); + if (mod->elferr != DWFL_E_NOERROR) + return; + + if (!mod->main.valid) + { + /* Clear any explicitly reported build ID, just in case it was wrong. + We'll fetch it from the file when asked. */ + free (mod->build_id_bits); + mod->build_id_bits = NULL; + mod->build_id_len = 0; + } + else if (fallback) + mod_verify_build_id (mod); + + mod->main_bias = mod->e_type == ET_REL ? 0 : mod->low_addr - mod->main.vaddr; +} + +/* If the main file might have been prelinked, then we need to + discover the correct synchronization address between the main and + debug files. Because of prelink's section juggling, we cannot rely + on the address_sync computed from PT_LOAD segments (see open_elf). + + We will attempt to discover a synchronization address based on the + section headers instead. But finding a section address that is + safe to use requires identifying which sections are SHT_PROGBITS. + We can do that in the main file, but in the debug file all the + allocated sections have been transformed into SHT_NOBITS so we have + lost the means to match them up correctly. + + The only method left to us is to decode the .gnu.prelink_undo + section in the prelinked main file. This shows what the sections + looked like before prelink juggled them--when they still had a + direct correspondence to the debug file. */ +static Dwfl_Error +find_prelink_address_sync (Dwfl_Module *mod, struct dwfl_file *file) +{ + /* The magic section is only identified by name. */ + size_t shstrndx; + if (elf_getshdrstrndx (mod->main.elf, &shstrndx) < 0) + return DWFL_E_LIBELF; + + 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 (unlikely (shdr == NULL)) + return DWFL_E_LIBELF; + if (shdr->sh_type == SHT_PROGBITS + && !(shdr->sh_flags & SHF_ALLOC) + && shdr->sh_name != 0) + { + const char *secname = elf_strptr (mod->main.elf, shstrndx, + shdr->sh_name); + if (unlikely (secname == NULL)) + return DWFL_E_LIBELF; + if (!strcmp (secname, ".gnu.prelink_undo")) + break; + } + } + + if (scn == NULL) + /* There was no .gnu.prelink_undo section. */ + return DWFL_E_NOERROR; + + Elf_Data *undodata = elf_rawdata (scn, NULL); + if (unlikely (undodata == NULL)) + return DWFL_E_LIBELF; + + /* Decode the section. It consists of the original ehdr, phdrs, + and shdrs (but omits section 0). */ + + union + { + Elf32_Ehdr e32; + Elf64_Ehdr e64; + } ehdr; + Elf_Data dst = + { + .d_buf = &ehdr, + .d_size = sizeof ehdr, + .d_type = ELF_T_EHDR, + .d_version = EV_CURRENT + }; + Elf_Data src = *undodata; + src.d_size = gelf_fsize (mod->main.elf, ELF_T_EHDR, 1, EV_CURRENT); + src.d_type = ELF_T_EHDR; + if (unlikely (gelf_xlatetom (mod->main.elf, &dst, &src, + elf_getident (mod->main.elf, NULL)[EI_DATA]) + == NULL)) + return DWFL_E_LIBELF; + + size_t shentsize = gelf_fsize (mod->main.elf, ELF_T_SHDR, 1, EV_CURRENT); + size_t phentsize = gelf_fsize (mod->main.elf, ELF_T_PHDR, 1, EV_CURRENT); + + uint_fast16_t phnum; + uint_fast16_t shnum; + if (ehdr.e32.e_ident[EI_CLASS] == ELFCLASS32) + { + if (ehdr.e32.e_shentsize != shentsize + || ehdr.e32.e_phentsize != phentsize) + return DWFL_E_BAD_PRELINK; + phnum = ehdr.e32.e_phnum; + shnum = ehdr.e32.e_shnum; + } + else + { + if (ehdr.e64.e_shentsize != shentsize + || ehdr.e64.e_phentsize != phentsize) + return DWFL_E_BAD_PRELINK; + phnum = ehdr.e64.e_phnum; + shnum = ehdr.e64.e_shnum; + } + + /* Since prelink does not store the zeroth section header in the undo + section, it cannot support SHN_XINDEX encoding. */ + if (unlikely (shnum >= SHN_LORESERVE) + || unlikely (undodata->d_size != (src.d_size + + phnum * phentsize + + (shnum - 1) * shentsize))) + return DWFL_E_BAD_PRELINK; + + /* We look at the allocated SHT_PROGBITS (or SHT_NOBITS) sections. (Most + every file will have some SHT_PROGBITS sections, but it's possible to + have one with nothing but .bss, i.e. SHT_NOBITS.) The special sections + that can be moved around have different sh_type values--except for + .interp, the section that became the PT_INTERP segment. So we exclude + the SHT_PROGBITS section whose address matches the PT_INTERP p_vaddr. + For this reason, we must examine the phdrs first to find PT_INTERP. */ + + GElf_Addr main_interp = 0; + { + size_t main_phnum; + if (unlikely (elf_getphdrnum (mod->main.elf, &main_phnum))) + return DWFL_E_LIBELF; + for (size_t i = 0; i < main_phnum; ++i) + { + GElf_Phdr phdr; + if (unlikely (gelf_getphdr (mod->main.elf, i, &phdr) == NULL)) + return DWFL_E_LIBELF; + if (phdr.p_type == PT_INTERP) + { + main_interp = phdr.p_vaddr; + break; + } + } + } + + src.d_buf += src.d_size; + src.d_type = ELF_T_PHDR; + src.d_size = phnum * phentsize; + + GElf_Addr undo_interp = 0; + { + union + { + Elf32_Phdr p32[phnum]; + Elf64_Phdr p64[phnum]; + } phdr; + dst.d_buf = &phdr; + dst.d_size = sizeof phdr; + if (unlikely (gelf_xlatetom (mod->main.elf, &dst, &src, + ehdr.e32.e_ident[EI_DATA]) == NULL)) + return DWFL_E_LIBELF; + if (ehdr.e32.e_ident[EI_CLASS] == ELFCLASS32) + { + for (uint_fast16_t i = 0; i < phnum; ++i) + if (phdr.p32[i].p_type == PT_INTERP) + { + undo_interp = phdr.p32[i].p_vaddr; + break; + } + } + else + { + for (uint_fast16_t i = 0; i < phnum; ++i) + if (phdr.p64[i].p_type == PT_INTERP) + { + undo_interp = phdr.p64[i].p_vaddr; + break; + } + } + } + + if (unlikely ((main_interp == 0) != (undo_interp == 0))) + return DWFL_E_BAD_PRELINK; + + src.d_buf += src.d_size; + src.d_type = ELF_T_SHDR; + src.d_size = gelf_fsize (mod->main.elf, ELF_T_SHDR, shnum - 1, EV_CURRENT); + + union + { + Elf32_Shdr s32[shnum - 1]; + Elf64_Shdr s64[shnum - 1]; + } shdr; + dst.d_buf = &shdr; + dst.d_size = sizeof shdr; + if (unlikely (gelf_xlatetom (mod->main.elf, &dst, &src, + ehdr.e32.e_ident[EI_DATA]) == NULL)) + return DWFL_E_LIBELF; + + /* Now we can look at the original section headers of the main file + before it was prelinked. First we'll apply our method to the main + file sections as they are after prelinking, to calculate the + synchronization address of the main file. Then we'll apply that + same method to the saved section headers, to calculate the matching + synchronization address of the debug file. + + The method is to consider SHF_ALLOC sections that are either + SHT_PROGBITS or SHT_NOBITS, excluding the section whose sh_addr + matches the PT_INTERP p_vaddr. The special sections that can be + moved by prelink have other types, except for .interp (which + becomes PT_INTERP). The "real" sections cannot move as such, but + .bss can be split into .dynbss and .bss, with the total memory + image remaining the same but being spread across the two sections. + So we consider the highest section end, which still matches up. */ + + GElf_Addr highest; + + inline void consider_shdr (GElf_Addr interp, + GElf_Word sh_type, + GElf_Xword sh_flags, + GElf_Addr sh_addr, + GElf_Xword sh_size) + { + if ((sh_flags & SHF_ALLOC) + && ((sh_type == SHT_PROGBITS && sh_addr != interp) + || sh_type == SHT_NOBITS)) + { + const GElf_Addr sh_end = sh_addr + sh_size; + if (sh_end > highest) + highest = sh_end; + } + } + + highest = 0; + scn = NULL; + while ((scn = elf_nextscn (mod->main.elf, scn)) != NULL) + { + GElf_Shdr sh_mem; + GElf_Shdr *sh = gelf_getshdr (scn, &sh_mem); + if (unlikely (sh == NULL)) + return DWFL_E_LIBELF; + consider_shdr (main_interp, sh->sh_type, sh->sh_flags, + sh->sh_addr, sh->sh_size); + } + if (highest > mod->main.vaddr) + { + mod->main.address_sync = highest; + + highest = 0; + if (ehdr.e32.e_ident[EI_CLASS] == ELFCLASS32) + for (size_t i = 0; i < shnum - 1; ++i) + consider_shdr (undo_interp, shdr.s32[i].sh_type, shdr.s32[i].sh_flags, + shdr.s32[i].sh_addr, shdr.s32[i].sh_size); + else + for (size_t i = 0; i < shnum - 1; ++i) + consider_shdr (undo_interp, shdr.s64[i].sh_type, shdr.s64[i].sh_flags, + shdr.s64[i].sh_addr, shdr.s64[i].sh_size); + + if (highest > file->vaddr) + file->address_sync = highest; + else + return DWFL_E_BAD_PRELINK; + } + + return DWFL_E_NOERROR; +} + +/* Find the separate debuginfo file for this module and open libelf on it. + When we return success, MOD->debug is set up. */ +static Dwfl_Error +find_debuginfo (Dwfl_Module *mod) +{ + if (mod->debug.elf != NULL) + return DWFL_E_NOERROR; + + GElf_Word debuglink_crc = 0; + const char *debuglink_file; + debuglink_file = INTUSE(dwelf_elf_gnu_debuglink) (mod->main.elf, + &debuglink_crc); + + mod->debug.fd = (*mod->dwfl->callbacks->find_debuginfo) (MODCB_ARGS (mod), + mod->main.name, + debuglink_file, + debuglink_crc, + &mod->debug.name); + Dwfl_Error result = open_elf (mod, &mod->debug); + if (result == DWFL_E_NOERROR && mod->debug.address_sync != 0) + result = find_prelink_address_sync (mod, &mod->debug); + return result; +} + +/* Try to find the alternative debug link for the given DWARF and set + it if found. Only called when mod->dw is already setup but still + might need an alternative (dwz multi) debug file. filename is either + the main or debug name from which the Dwarf was created. */ +static void +find_debug_altlink (Dwfl_Module *mod, const char *filename) +{ + assert (mod->dw != NULL); + + const char *altname; + const void *build_id; + ssize_t build_id_len = INTUSE(dwelf_dwarf_gnu_debugaltlink) (mod->dw, + &altname, + &build_id); + + if (build_id_len > 0) + { + /* We could store altfile in the module, but don't really need it. */ + char *altfile = NULL; + mod->alt_fd = (*mod->dwfl->callbacks->find_debuginfo) (MODCB_ARGS (mod), + filename, + altname, + 0, + &altfile); + + /* The (internal) callbacks might just set mod->alt_elf directly + because they open the Elf anyway for sanity checking. + Otherwise open either the given file name or use the fd + returned. */ + Dwfl_Error error = open_elf_file (&mod->alt_elf, &mod->alt_fd, + &altfile); + if (error == DWFL_E_NOERROR) + { + mod->alt = INTUSE(dwarf_begin_elf) (mod->alt_elf, + DWARF_C_READ, NULL); + if (mod->alt == NULL) + { + elf_end (mod->alt_elf); + mod->alt_elf = NULL; + close (mod->alt_fd); + mod->alt_fd = -1; + } + else + dwarf_setalt (mod->dw, mod->alt); + } + + free (altfile); /* See above, we don't really need it. */ + } +} + +/* Try to find a symbol table in FILE. + Returns DWFL_E_NOERROR if a proper one is found. + Returns DWFL_E_NO_SYMTAB if not, but still sets results for SHT_DYNSYM. */ +static Dwfl_Error +load_symtab (struct dwfl_file *file, struct dwfl_file **symfile, + Elf_Scn **symscn, Elf_Scn **xndxscn, + size_t *syments, int *first_global, GElf_Word *strshndx) +{ + bool symtab = false; + Elf_Scn *scn = NULL; + while ((scn = elf_nextscn (file->elf, scn)) != NULL) + { + GElf_Shdr shdr_mem, *shdr = gelf_getshdr (scn, &shdr_mem); + if (shdr != NULL) + switch (shdr->sh_type) + { + case SHT_SYMTAB: + if (shdr->sh_entsize == 0) + break; + symtab = true; + *symscn = scn; + *symfile = file; + *strshndx = shdr->sh_link; + *syments = shdr->sh_size / shdr->sh_entsize; + *first_global = shdr->sh_info; + if (*xndxscn != NULL) + return DWFL_E_NOERROR; + break; + + case SHT_DYNSYM: + if (symtab) + break; + /* Use this if need be, but keep looking for SHT_SYMTAB. */ + if (shdr->sh_entsize == 0) + break; + *symscn = scn; + *symfile = file; + *strshndx = shdr->sh_link; + *syments = shdr->sh_size / shdr->sh_entsize; + *first_global = shdr->sh_info; + break; + + case SHT_SYMTAB_SHNDX: + *xndxscn = scn; + if (symtab) + return DWFL_E_NOERROR; + break; + + default: + break; + } + } + + if (symtab) + /* We found one, though no SHT_SYMTAB_SHNDX to go with it. */ + return DWFL_E_NOERROR; + + /* We found no SHT_SYMTAB, so any SHT_SYMTAB_SHNDX was bogus. + We might have found an SHT_DYNSYM and set *SYMSCN et al though. */ + *xndxscn = NULL; + return DWFL_E_NO_SYMTAB; +} + + +/* Translate addresses into file offsets. + OFFS[*] start out zero and remain zero if unresolved. */ +static void +find_offsets (Elf *elf, GElf_Addr main_bias, size_t phnum, size_t n, + GElf_Addr addrs[n], GElf_Off offs[n]) +{ + size_t unsolved = n; + for (size_t i = 0; i < phnum; ++i) + { + GElf_Phdr phdr_mem; + GElf_Phdr *phdr = gelf_getphdr (elf, i, &phdr_mem); + if (phdr != NULL && phdr->p_type == PT_LOAD && phdr->p_memsz > 0) + for (size_t j = 0; j < n; ++j) + if (offs[j] == 0 + && addrs[j] >= phdr->p_vaddr + main_bias + && addrs[j] - (phdr->p_vaddr + main_bias) < phdr->p_filesz) + { + offs[j] = addrs[j] - (phdr->p_vaddr + main_bias) + phdr->p_offset; + if (--unsolved == 0) + break; + } + } +} + +/* Try to find a dynamic symbol table via phdrs. */ +static void +find_dynsym (Dwfl_Module *mod) +{ + GElf_Ehdr ehdr_mem; + GElf_Ehdr *ehdr = gelf_getehdr (mod->main.elf, &ehdr_mem); + + size_t phnum; + if (unlikely (elf_getphdrnum (mod->main.elf, &phnum) != 0)) + return; + + for (size_t i = 0; i < phnum; ++i) + { + GElf_Phdr phdr_mem; + GElf_Phdr *phdr = gelf_getphdr (mod->main.elf, i, &phdr_mem); + if (phdr == NULL) + break; + + if (phdr->p_type == PT_DYNAMIC) + { + /* Examine the dynamic section for the pointers we need. */ + + Elf_Data *data = elf_getdata_rawchunk (mod->main.elf, + phdr->p_offset, phdr->p_filesz, + ELF_T_DYN); + if (data == NULL) + continue; + + enum + { + i_symtab, + i_strtab, + i_hash, + i_gnu_hash, + i_max + }; + GElf_Addr addrs[i_max] = { 0, }; + GElf_Xword strsz = 0; + size_t n = data->d_size / gelf_fsize (mod->main.elf, + ELF_T_DYN, 1, EV_CURRENT); + for (size_t j = 0; j < n; ++j) + { + GElf_Dyn dyn_mem; + GElf_Dyn *dyn = gelf_getdyn (data, j, &dyn_mem); + if (dyn != NULL) + switch (dyn->d_tag) + { + case DT_SYMTAB: + addrs[i_symtab] = dyn->d_un.d_ptr; + continue; + + case DT_HASH: + addrs[i_hash] = dyn->d_un.d_ptr; + continue; + + case DT_GNU_HASH: + addrs[i_gnu_hash] = dyn->d_un.d_ptr; + continue; + + case DT_STRTAB: + addrs[i_strtab] = dyn->d_un.d_ptr; + continue; + + case DT_STRSZ: + strsz = dyn->d_un.d_val; + continue; + + default: + continue; + + case DT_NULL: + break; + } + break; + } + + /* Translate pointers into file offsets. ADJUST is either zero + in case the dynamic segment wasn't adjusted or mod->main_bias. */ + void translate_offs (GElf_Addr adjust) + { + GElf_Off offs[i_max] = { 0, }; + find_offsets (mod->main.elf, adjust, phnum, i_max, addrs, offs); + + /* Figure out the size of the symbol table. */ + if (offs[i_hash] != 0) + { + /* In the original format, .hash says the size of .dynsym. */ + + size_t entsz = SH_ENTSIZE_HASH (ehdr); + data = elf_getdata_rawchunk (mod->main.elf, + offs[i_hash] + entsz, entsz, + entsz == 4 ? ELF_T_WORD + : ELF_T_XWORD); + if (data != NULL) + mod->syments = (entsz == 4 + ? *(const GElf_Word *) data->d_buf + : *(const GElf_Xword *) data->d_buf); + } + if (offs[i_gnu_hash] != 0 && mod->syments == 0) + { + /* In the new format, we can derive it with some work. */ + + const struct + { + Elf32_Word nbuckets; + Elf32_Word symndx; + Elf32_Word maskwords; + Elf32_Word shift2; + } *header; + + data = elf_getdata_rawchunk (mod->main.elf, offs[i_gnu_hash], + sizeof *header, ELF_T_WORD); + if (data != NULL) + { + header = data->d_buf; + Elf32_Word nbuckets = header->nbuckets; + Elf32_Word symndx = header->symndx; + GElf_Off buckets_at = (offs[i_gnu_hash] + sizeof *header + + (gelf_getclass (mod->main.elf) + * sizeof (Elf32_Word) + * header->maskwords)); + + // elf_getdata_rawchunk takes a size_t, make sure it + // doesn't overflow. +#if SIZE_MAX <= UINT32_MAX + if (nbuckets > SIZE_MAX / sizeof (Elf32_Word)) + data = NULL; + else +#endif + data + = elf_getdata_rawchunk (mod->main.elf, buckets_at, + nbuckets * sizeof (Elf32_Word), + ELF_T_WORD); + if (data != NULL && symndx < nbuckets) + { + const Elf32_Word *const buckets = data->d_buf; + Elf32_Word maxndx = symndx; + for (Elf32_Word bucket = 0; bucket < nbuckets; ++bucket) + if (buckets[bucket] > maxndx) + maxndx = buckets[bucket]; + + GElf_Off hasharr_at = (buckets_at + + nbuckets * sizeof (Elf32_Word)); + hasharr_at += (maxndx - symndx) * sizeof (Elf32_Word); + do + { + data = elf_getdata_rawchunk (mod->main.elf, + hasharr_at, + sizeof (Elf32_Word), + ELF_T_WORD); + if (data != NULL + && (*(const Elf32_Word *) data->d_buf & 1u)) + { + mod->syments = maxndx + 1; + break; + } + ++maxndx; + hasharr_at += sizeof (Elf32_Word); + } while (data != NULL); + } + } + } + if (offs[i_strtab] > offs[i_symtab] && mod->syments == 0) + mod->syments = ((offs[i_strtab] - offs[i_symtab]) + / gelf_fsize (mod->main.elf, + ELF_T_SYM, 1, EV_CURRENT)); + + if (mod->syments > 0) + { + mod->symdata = elf_getdata_rawchunk (mod->main.elf, + offs[i_symtab], + gelf_fsize (mod->main.elf, + ELF_T_SYM, + mod->syments, + EV_CURRENT), + ELF_T_SYM); + if (mod->symdata != NULL) + { + mod->symstrdata = elf_getdata_rawchunk (mod->main.elf, + offs[i_strtab], + strsz, + ELF_T_BYTE); + if (mod->symstrdata == NULL) + mod->symdata = NULL; + } + if (mod->symdata == NULL) + mod->symerr = DWFL_E (LIBELF, elf_errno ()); + else + { + mod->symfile = &mod->main; + mod->symerr = DWFL_E_NOERROR; + } + } + } + + /* First try unadjusted, like ELF files from disk, vdso. + Then try for already adjusted dynamic section, like ELF + from remote memory. */ + translate_offs (0); + if (mod->symfile == NULL) + translate_offs (mod->main_bias); + + return; + } + } +} + + +#if USE_LZMA +/* Try to find the offset between the main file and .gnu_debugdata. */ +static bool +find_aux_address_sync (Dwfl_Module *mod) +{ + /* Don't trust the phdrs in the minisymtab elf file to be setup correctly. + The address_sync is equal to the main file it is embedded in at first. */ + mod->aux_sym.address_sync = mod->main.address_sync; + + /* Adjust address_sync for the difference in entry addresses, attempting to + account for ELF relocation changes after aux was split. */ + GElf_Ehdr ehdr_main, ehdr_aux; + if (unlikely (gelf_getehdr (mod->main.elf, &ehdr_main) == NULL) + || unlikely (gelf_getehdr (mod->aux_sym.elf, &ehdr_aux) == NULL)) + return false; + mod->aux_sym.address_sync += ehdr_aux.e_entry - ehdr_main.e_entry; + + /* The shdrs are setup OK to make find_prelink_address_sync () do the right + thing, which is possibly more reliable, but it needs .gnu.prelink_undo. */ + if (mod->aux_sym.address_sync != 0) + return find_prelink_address_sync (mod, &mod->aux_sym) == DWFL_E_NOERROR; + + return true; +} +#endif + +/* Try to find the auxiliary symbol table embedded in the main elf file + section .gnu_debugdata. Only matters if the symbol information comes + from the main file dynsym. No harm done if not found. */ +static void +find_aux_sym (Dwfl_Module *mod __attribute__ ((unused)), + Elf_Scn **aux_symscn __attribute__ ((unused)), + Elf_Scn **aux_xndxscn __attribute__ ((unused)), + GElf_Word *aux_strshndx __attribute__ ((unused))) +{ + /* Since a .gnu_debugdata section is compressed using lzma don't do + anything unless we have support for that. */ +#if USE_LZMA + Elf *elf = mod->main.elf; + + size_t shstrndx; + if (elf_getshdrstrndx (elf, &shstrndx) < 0) + return; + + Elf_Scn *scn = NULL; + while ((scn = elf_nextscn (elf, scn)) != NULL) + { + GElf_Shdr shdr_mem; + GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem); + if (shdr == NULL) + return; + + const char *name = elf_strptr (elf, shstrndx, shdr->sh_name); + if (name == NULL) + return; + + if (!strcmp (name, ".gnu_debugdata")) + break; + } + + if (scn == NULL) + return; + + /* Found the .gnu_debugdata section. Uncompress the lzma image and + turn it into an ELF image. */ + Elf_Data *rawdata = elf_rawdata (scn, NULL); + if (rawdata == NULL) + return; + + Dwfl_Error error; + void *buffer = NULL; + size_t size = 0; + error = __libdw_unlzma (-1, 0, rawdata->d_buf, rawdata->d_size, + &buffer, &size); + if (error == DWFL_E_NOERROR) + { + if (unlikely (size == 0)) + free (buffer); + else + { + mod->aux_sym.elf = elf_memory (buffer, size); + if (mod->aux_sym.elf == NULL) + free (buffer); + else + { + mod->aux_sym.fd = -1; + mod->aux_sym.elf->flags |= ELF_F_MALLOCED; + if (open_elf (mod, &mod->aux_sym) != DWFL_E_NOERROR) + return; + if (! find_aux_address_sync (mod)) + { + elf_end (mod->aux_sym.elf); + mod->aux_sym.elf = NULL; + return; + } + + /* So far, so good. Get minisymtab table data and cache it. */ + bool minisymtab = false; + scn = NULL; + while ((scn = elf_nextscn (mod->aux_sym.elf, scn)) != NULL) + { + GElf_Shdr shdr_mem, *shdr = gelf_getshdr (scn, &shdr_mem); + if (shdr != NULL) + switch (shdr->sh_type) + { + case SHT_SYMTAB: + minisymtab = true; + *aux_symscn = scn; + *aux_strshndx = shdr->sh_link; + mod->aux_syments = shdr->sh_size / shdr->sh_entsize; + mod->aux_first_global = shdr->sh_info; + if (*aux_xndxscn != NULL) + return; + break; + + case SHT_SYMTAB_SHNDX: + *aux_xndxscn = scn; + if (minisymtab) + return; + break; + + default: + break; + } + } + + if (minisymtab) + /* We found one, though no SHT_SYMTAB_SHNDX to go with it. */ + return; + + /* We found no SHT_SYMTAB, so everything else is bogus. */ + *aux_xndxscn = NULL; + *aux_strshndx = 0; + mod->aux_syments = 0; + elf_end (mod->aux_sym.elf); + mod->aux_sym.elf = NULL; + return; + } + } + } + else + free (buffer); +#endif +} + +/* Try to find a symbol table in either MOD->main.elf or MOD->debug.elf. */ +static void +find_symtab (Dwfl_Module *mod) +{ + if (mod->symdata != NULL || mod->aux_symdata != NULL /* Already done. */ + || mod->symerr != DWFL_E_NOERROR) /* Cached previous failure. */ + return; + + __libdwfl_getelf (mod); + mod->symerr = mod->elferr; + if (mod->symerr != DWFL_E_NOERROR) + return; + + /* First see if the main ELF file has the debugging information. */ + Elf_Scn *symscn = NULL, *xndxscn = NULL; + Elf_Scn *aux_symscn = NULL, *aux_xndxscn = NULL; + GElf_Word strshndx, aux_strshndx = 0; + mod->symerr = load_symtab (&mod->main, &mod->symfile, &symscn, + &xndxscn, &mod->syments, &mod->first_global, + &strshndx); + switch (mod->symerr) + { + default: + return; + + case DWFL_E_NOERROR: + break; + + case DWFL_E_NO_SYMTAB: + /* Now we have to look for a separate debuginfo file. */ + mod->symerr = find_debuginfo (mod); + switch (mod->symerr) + { + default: + return; + + case DWFL_E_NOERROR: + mod->symerr = load_symtab (&mod->debug, &mod->symfile, &symscn, + &xndxscn, &mod->syments, + &mod->first_global, &strshndx); + break; + + case DWFL_E_CB: /* The find_debuginfo hook failed. */ + mod->symerr = DWFL_E_NO_SYMTAB; + break; + } + + switch (mod->symerr) + { + default: + return; + + case DWFL_E_NOERROR: + break; + + case DWFL_E_NO_SYMTAB: + /* There might be an auxiliary table. */ + find_aux_sym (mod, &aux_symscn, &aux_xndxscn, &aux_strshndx); + + if (symscn != NULL) + { + /* We still have the dynamic symbol table. */ + mod->symerr = DWFL_E_NOERROR; + break; + } + + if (aux_symscn != NULL) + { + /* We still have the auxiliary symbol table. */ + mod->symerr = DWFL_E_NOERROR; + goto aux_cache; + } + + /* Last ditch, look for dynamic symbols without section headers. */ + find_dynsym (mod); + return; + } + break; + } + + /* This does some sanity checks on the string table section. */ + if (elf_strptr (mod->symfile->elf, strshndx, 0) == NULL) + { + elferr: + mod->symerr = DWFL_E (LIBELF, elf_errno ()); + goto aux_cleanup; /* This cleans up some more and tries find_dynsym. */ + } + + /* Cache the data; MOD->syments and MOD->first_global were set above. */ + + mod->symstrdata = elf_getdata (elf_getscn (mod->symfile->elf, strshndx), + NULL); + if (mod->symstrdata == NULL || mod->symstrdata->d_buf == NULL) + goto elferr; + + if (xndxscn == NULL) + mod->symxndxdata = NULL; + else + { + mod->symxndxdata = elf_getdata (xndxscn, NULL); + if (mod->symxndxdata == NULL || mod->symxndxdata->d_buf == NULL) + goto elferr; + } + + mod->symdata = elf_getdata (symscn, NULL); + if (mod->symdata == NULL || mod->symdata->d_buf == NULL) + goto elferr; + + // Sanity check number of symbols. + GElf_Shdr shdr_mem, *shdr = gelf_getshdr (symscn, &shdr_mem); + if (mod->syments > mod->symdata->d_size / shdr->sh_entsize + || (size_t) mod->first_global > mod->syments) + goto elferr; + + /* Cache any auxiliary symbol info, when it fails, just ignore aux_sym. */ + if (aux_symscn != NULL) + { + aux_cache: + /* This does some sanity checks on the string table section. */ + if (elf_strptr (mod->aux_sym.elf, aux_strshndx, 0) == NULL) + { + aux_cleanup: + mod->aux_syments = 0; + elf_end (mod->aux_sym.elf); + mod->aux_sym.elf = NULL; + /* We thought we had something through shdrs, but it failed... + Last ditch, look for dynamic symbols without section headers. */ + find_dynsym (mod); + return; + } + + mod->aux_symstrdata = elf_getdata (elf_getscn (mod->aux_sym.elf, + aux_strshndx), + NULL); + if (mod->aux_symstrdata == NULL || mod->aux_symstrdata->d_buf == NULL) + goto aux_cleanup; + + if (aux_xndxscn == NULL) + mod->aux_symxndxdata = NULL; + else + { + mod->aux_symxndxdata = elf_getdata (aux_xndxscn, NULL); + if (mod->aux_symxndxdata == NULL + || mod->aux_symxndxdata->d_buf == NULL) + goto aux_cleanup; + } + + mod->aux_symdata = elf_getdata (aux_symscn, NULL); + if (mod->aux_symdata == NULL || mod->aux_symdata->d_buf == NULL) + goto aux_cleanup; + + // Sanity check number of aux symbols. + shdr = gelf_getshdr (aux_symscn, &shdr_mem); + if (mod->aux_syments > mod->aux_symdata->d_size / shdr->sh_entsize + || (size_t) mod->aux_first_global > mod->aux_syments) + goto aux_cleanup; + } +} + + +/* Try to open a libebl backend for MOD. */ +Dwfl_Error +internal_function +__libdwfl_module_getebl (Dwfl_Module *mod) +{ + if (mod->ebl == NULL) + { + __libdwfl_getelf (mod); + if (mod->elferr != DWFL_E_NOERROR) + return mod->elferr; + + mod->ebl = ebl_openbackend (mod->main.elf); + if (mod->ebl == NULL) + return DWFL_E_LIBEBL; + } + return DWFL_E_NOERROR; +} + +/* Try to start up libdw on DEBUGFILE. */ +static Dwfl_Error +load_dw (Dwfl_Module *mod, struct dwfl_file *debugfile) +{ + if (mod->e_type == ET_REL && !debugfile->relocated) + { + const Dwfl_Callbacks *const cb = mod->dwfl->callbacks; + + /* The debugging sections have to be relocated. */ + if (cb->section_address == NULL) + return DWFL_E_NOREL; + + Dwfl_Error error = __libdwfl_module_getebl (mod); + if (error != DWFL_E_NOERROR) + return error; + + find_symtab (mod); + Dwfl_Error result = mod->symerr; + if (result == DWFL_E_NOERROR) + result = __libdwfl_relocate (mod, debugfile->elf, true); + if (result != DWFL_E_NOERROR) + return result; + + /* Don't keep the file descriptors around. */ + if (mod->main.fd != -1 && elf_cntl (mod->main.elf, ELF_C_FDREAD) == 0) + { + close (mod->main.fd); + mod->main.fd = -1; + } + if (debugfile->fd != -1 && elf_cntl (debugfile->elf, ELF_C_FDREAD) == 0) + { + close (debugfile->fd); + debugfile->fd = -1; + } + } + + mod->dw = INTUSE(dwarf_begin_elf) (debugfile->elf, DWARF_C_READ, NULL); + if (mod->dw == NULL) + { + int err = INTUSE(dwarf_errno) (); + return err == DWARF_E_NO_DWARF ? DWFL_E_NO_DWARF : DWFL_E (LIBDW, err); + } + + /* Until we have iterated through all CU's, we might do lazy lookups. */ + mod->lazycu = 1; + + return DWFL_E_NOERROR; +} + +/* Try to start up libdw on either the main file or the debuginfo file. */ +static void +find_dw (Dwfl_Module *mod) +{ + if (mod->dw != NULL /* Already done. */ + || mod->dwerr != DWFL_E_NOERROR) /* Cached previous failure. */ + return; + + __libdwfl_getelf (mod); + mod->dwerr = mod->elferr; + if (mod->dwerr != DWFL_E_NOERROR) + return; + + /* First see if the main ELF file has the debugging information. */ + mod->dwerr = load_dw (mod, &mod->main); + switch (mod->dwerr) + { + case DWFL_E_NOERROR: + mod->debug.elf = mod->main.elf; + mod->debug.address_sync = mod->main.address_sync; + + /* The Dwarf might need an alt debug file, find that now after + everything about the debug file has been setup (the + find_debuginfo callback might need it). */ + find_debug_altlink (mod, mod->main.name); + return; + + case DWFL_E_NO_DWARF: + break; + + default: + goto canonicalize; + } + + /* Now we have to look for a separate debuginfo file. */ + mod->dwerr = find_debuginfo (mod); + switch (mod->dwerr) + { + case DWFL_E_NOERROR: + mod->dwerr = load_dw (mod, &mod->debug); + if (mod->dwerr == DWFL_E_NOERROR) + { + /* The Dwarf might need an alt debug file, find that now after + everything about the debug file has been setup (the + find_debuginfo callback might need it). */ + find_debug_altlink (mod, mod->debug.name); + return; + } + + break; + + case DWFL_E_CB: /* The find_debuginfo hook failed. */ + mod->dwerr = DWFL_E_NO_DWARF; + return; + + default: + break; + } + + canonicalize: + mod->dwerr = __libdwfl_canon_error (mod->dwerr); +} + +Dwarf * +dwfl_module_getdwarf (Dwfl_Module *mod, Dwarf_Addr *bias) +{ + if (mod == NULL) + return NULL; + + find_dw (mod); + if (mod->dwerr == DWFL_E_NOERROR) + { + /* If dwfl_module_getelf was used previously, then partial apply + relocation to miscellaneous sections in the debug file too. */ + if (mod->e_type == ET_REL + && mod->main.relocated && ! mod->debug.relocated) + { + mod->debug.relocated = true; + if (mod->debug.elf != mod->main.elf) + (void) __libdwfl_relocate (mod, mod->debug.elf, false); + } + + *bias = dwfl_adjusted_dwarf_addr (mod, 0); + return mod->dw; + } + + __libdwfl_seterrno (mod->dwerr); + return NULL; +} +INTDEF (dwfl_module_getdwarf) + +int +dwfl_module_getsymtab (Dwfl_Module *mod) +{ + if (mod == NULL) + return -1; + + find_symtab (mod); + if (mod->symerr == DWFL_E_NOERROR) + /* We will skip the auxiliary zero entry if there is another one. */ + return (mod->syments + mod->aux_syments + - (mod->syments > 0 && mod->aux_syments > 0 ? 1 : 0)); + + __libdwfl_seterrno (mod->symerr); + return -1; +} +INTDEF (dwfl_module_getsymtab) + +int +dwfl_module_getsymtab_first_global (Dwfl_Module *mod) +{ + if (mod == NULL) + return -1; + + find_symtab (mod); + if (mod->symerr == DWFL_E_NOERROR) + { + /* All local symbols should come before all global symbols. If + we have an auxiliary table make sure all the main locals come + first, then all aux locals, then all main globals and finally all + aux globals. And skip the auxiliary table zero undefined + entry. */ + int skip_aux_zero = (mod->syments > 0 && mod->aux_syments > 0) ? 1 : 0; + return mod->first_global + mod->aux_first_global - skip_aux_zero; + } + + __libdwfl_seterrno (mod->symerr); + return -1; +} +INTDEF (dwfl_module_getsymtab_first_global) |