/* Build a section containing all non-stack symbols. Copyright 2000 Keith Owens This file is part of the Linux modutils. This program 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; either version 2 of the License, or (at your option) any later version. This program 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 this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ #ident "$Id: obj_kallsyms.c,v 1.1.1.2 2000/10/04 18:44:45 notting Exp $" #include #include #include #include "obj.h" #include "kallsyms.h" #include "util.h" /*======================================================================*/ #define EXPAND_BY 4096 /* Arbitrary */ /* Append a string to the big list of strings */ static void append_string (const char *s, char **strings, ElfW(Word) *strings_size, ElfW(Word) *strings_left) { int l = strlen(s) + 1; while (l > *strings_left) { *strings = xrealloc(*strings, *strings_size += EXPAND_BY); *strings_left += EXPAND_BY; } memcpy((char *)*strings+*strings_size-*strings_left, s, l); *strings_left -= l; } /* Append a symbol to the big list of symbols */ static void append_symbol (const struct kallsyms_symbol *s, struct kallsyms_symbol **symbols, ElfW(Word) *symbols_size, ElfW(Word) *symbols_left) { int l = sizeof(*s); while (l > *symbols_left) { *symbols = xrealloc(*symbols, *symbols_size += EXPAND_BY); *symbols_left += EXPAND_BY; } memcpy((char *)*symbols+*symbols_size-*symbols_left, s, l); *symbols_left -= l; } /* qsort compare routine to sort symbols */ static const char *sym_strings; static int symbol_compare (const void *a, const void *b) { struct kallsyms_symbol *c = (struct kallsyms_symbol *) a; struct kallsyms_symbol *d = (struct kallsyms_symbol *) b; if (c->symbol_addr > d->symbol_addr) return(1); if (c->symbol_addr < d->symbol_addr) return(-1); return(strcmp(sym_strings+c->name_off, sym_strings+d->name_off)); } /* Extract all symbols from the input obj_file, ignore ones that are * no use for debugging, build an output obj_file containing only the * kallsyms section. * * The kallsyms section is a bit unusual. It deliberately has no * relocatable data, all "pointers" are represented as byte offsets * into the the section. This means it can be stored anywhere without * relocation problems. In particular it can be stored within a kernel * image, it can be stored separately from the kernel image, it can be * appended to a module just before loading, it can be stored in a * separate area etc. * * Format of the kallsyms section. * * Header: * Size of header. * Total size of kallsyms data, including strings. * Number of loaded sections. * Offset to first section entry from start of header. * Size of each section entry, excluding the name string. * Number of symbols. * Offset to first symbol entry from start of header. * Size of each symbol entry, excluding the name string. * * Section entry - one per loaded section. * Start of section[1]. * Size of section. * Offset to name of section, from start of strings. * Section flags. * * Symbol entry - one per symbol in the input file[2]. * Offset of section that owns this symbol, from start of section data. * Address of symbol within the real section[1]. * Offset to name of symbol, from start of strings. * * Notes: [1] This is an exception to the "represent pointers as * offsets" rule, it is a value, not an offset. The start * address of a section or a symbol is extracted from the * obj_file data which may contain absolute or relocatable * addresses. If the addresses are relocatable then the * caller must adjust the section and/or symbol entries in * kallsyms after relocation. * [2] Only symbols that fall within loaded sections are stored. */ int obj_kallsyms (struct obj_file *fin, struct obj_file **fout_result) { struct obj_file *fout; int i, loaded = 0, *fin_to_allsym_map; struct obj_section *isec, *osec; struct kallsyms_header *a_hdr; struct kallsyms_section *a_sec; ElfW(Off) sec_off; struct kallsyms_symbol *symbols = NULL, a_sym; ElfW(Word) symbols_size = 0, symbols_left = 0; char *strings = NULL, *p; ElfW(Word) strings_size = 0, strings_left = 0; ElfW(Off) file_offset; static char strtab[] = "\000" KALLSYMS_SEC_NAME; /* Create the kallsyms section. */ fout = arch_new_file(); memset(fout, 0, sizeof(*fout)); fout->symbol_cmp = strcmp; fout->symbol_hash = obj_elf_hash; fout->load_order_search_start = &fout->load_order; /* Copy file characteristics from input file and modify to suit */ memcpy(&fout->header, &fin->header, sizeof(fout->header)); fout->header.e_type = ET_REL; /* Output is relocatable */ fout->header.e_entry = 0; /* No entry point */ fout->header.e_phoff = 0; /* No program header */ file_offset = sizeof(fout->header); /* Step over Elf header */ fout->header.e_shoff = file_offset; /* Section headers next */ fout->header.e_phentsize = 0; /* No program header */ fout->header.e_phnum = 0; /* No program header */ fout->header.e_shnum = KALLSYMS_IDX+1; /* Initial, strtab, kallsyms */ fout->header.e_shstrndx = KALLSYMS_IDX-1; /* strtab */ file_offset += fout->header.e_shentsize * fout->header.e_shnum; /* Populate the section data for kallsyms itself */ fout->sections = xmalloc(sizeof(*(fout->sections))*fout->header.e_shnum); memset(fout->sections, 0, sizeof(*(fout->sections))*fout->header.e_shnum); fout->sections[0] = osec = arch_new_section(); memset(osec, 0, sizeof(*osec)); osec->header.sh_type = SHT_NULL; osec->header.sh_link = SHN_UNDEF; fout->sections[KALLSYMS_IDX-1] = osec = arch_new_section(); memset(osec, 0, sizeof(*osec)); osec->name = ".strtab"; osec->header.sh_type = SHT_STRTAB; osec->header.sh_link = SHN_UNDEF; osec->header.sh_offset = file_offset; osec->header.sh_size = sizeof(strtab); osec->contents = xmalloc(sizeof(strtab)); memcpy(osec->contents, strtab, sizeof(strtab)); file_offset += osec->header.sh_size; fout->sections[KALLSYMS_IDX] = osec = arch_new_section(); memset(osec, 0, sizeof(*osec)); osec->name = KALLSYMS_SEC_NAME; osec->header.sh_name = 1; /* Offset in strtab */ osec->header.sh_type = SHT_PROGBITS; /* Load it */ osec->header.sh_flags = SHF_ALLOC; /* Read only data */ osec->header.sh_link = SHN_UNDEF; osec->header.sh_addralign = sizeof(ElfW(Word)); file_offset = (file_offset + osec->header.sh_addralign - 1) & -(osec->header.sh_addralign); osec->header.sh_offset = file_offset; /* How many loaded sections are there? */ for (i = 0; i < fin->header.e_shnum; ++i) { if (fin->sections[i]->header.sh_flags & SHF_ALLOC) ++loaded; } /* Initial contents, header + one entry per input section. No strings. */ osec->header.sh_size = sizeof(*a_hdr) + loaded*sizeof(*a_sec); a_hdr = (struct kallsyms_header *) osec->contents = xmalloc(osec->header.sh_size); memset(osec->contents, 0, osec->header.sh_size); a_hdr->size = sizeof(*a_hdr); a_hdr->sections = loaded; a_hdr->section_off = a_hdr->size; a_hdr->section_size = sizeof(*a_sec); a_hdr->symbol_off = osec->header.sh_size; a_hdr->symbol_size = sizeof(a_sym); a_hdr->start = (ElfW(Addr))(~0); /* Map input section numbers to kallsyms section offsets. */ sec_off = 0; /* Offset to first kallsyms section entry */ fin_to_allsym_map = xmalloc(sizeof(*fin_to_allsym_map)*fin->header.e_shnum); for (i = 0; i < fin->header.e_shnum; ++i) { isec = fin->sections[i]; if (isec->header.sh_flags & SHF_ALLOC) { fin_to_allsym_map[isec->idx] = sec_off; sec_off += a_hdr->section_size; } else fin_to_allsym_map[isec->idx] = -1; /* Ignore this section */ } /* Copy the loaded section data. */ a_sec = (struct kallsyms_section *) ((char *) a_hdr + a_hdr->section_off); for (i = 0; i < fin->header.e_shnum; ++i) { isec = fin->sections[i]; if (!(isec->header.sh_flags & SHF_ALLOC)) continue; a_sec->start = isec->header.sh_addr; a_sec->size = isec->header.sh_size; a_sec->flags = isec->header.sh_flags; a_sec->name_off = strings_size - strings_left; append_string(isec->name, &strings, &strings_size, &strings_left); if (a_sec->start < a_hdr->start) a_hdr->start = a_sec->start; if (a_sec->start+a_sec->size > a_hdr->end) a_hdr->end = a_sec->start+a_sec->size; ++a_sec; } /* Build the kallsyms symbol table from the symbol hashes. */ for (i = 0; i < HASH_BUCKETS; ++i) { struct obj_symbol *sym = fin->symtab[i]; for (sym = fin->symtab[i]; sym ; sym = sym->next) { if (!sym || sym->secidx >= fin->header.e_shnum) continue; if ((a_sym.section_off = fin_to_allsym_map[sym->secidx]) == -1) continue; if (strcmp(sym->name, "gcc2_compiled.") == 0 || strncmp(sym->name, "__insmod_", 9) == 0) continue; a_sym.symbol_addr = sym->value; if (fin->header.e_type == ET_REL) a_sym.symbol_addr += fin->sections[sym->secidx]->header.sh_addr; a_sym.name_off = strings_size - strings_left; append_symbol(&a_sym, &symbols, &symbols_size, &symbols_left); append_string(sym->name, &strings, &strings_size, &strings_left); ++a_hdr->symbols; } } free(fin_to_allsym_map); /* Sort the symbols into ascending order by address and name */ sym_strings = strings; /* For symbol_compare */ qsort((char *) symbols, (unsigned) a_hdr->symbols, sizeof(* symbols), symbol_compare); sym_strings = NULL; /* Put the lot together */ osec->header.sh_size = a_hdr->total_size = a_hdr->symbol_off + a_hdr->symbols*a_hdr->symbol_size + strings_size - strings_left; a_hdr = (struct kallsyms_header *) osec->contents = xrealloc(a_hdr, a_hdr->total_size); p = (char *)a_hdr + a_hdr->symbol_off; memcpy(p, symbols, a_hdr->symbols*a_hdr->symbol_size); free(symbols); p += a_hdr->symbols*a_hdr->symbol_size; a_hdr->string_off = p - (char *)a_hdr; memcpy(p, strings, strings_size - strings_left); free(strings); *fout_result = fout; return 0; }