/* readelf.c - display information about ELF files. * * Copyright 2019 The Android Open Source Project * * See http://pubs.opengroup.org/onlinepubs/9699919799/utilities/nm.html USE_READELF(NEWTOY(readelf, "<1(dyn-syms)adehlnp:SsWx:", TOYFLAG_USR|TOYFLAG_BIN)) config READELF bool "readelf" default y help usage: readelf [-adehlnSs] [-p SECTION] [-x SECTION] [file...] Displays information about ELF files. -a Equivalent to -dhlnSs -d Show dynamic section -e Headers (equivalent to -hlS) -h Show ELF header -l Show program headers -n Show notes -p S Dump strings found in named/numbered section -S Show section headers -s Show symbol tables (.dynsym and .symtab) -x S Hex dump of named/numbered section --dyn-syms Show just .dynsym symbol table */ #define FOR_readelf #include "toys.h" GLOBALS( char *x, *p; char *elf, *shstrtab, *f; unsigned long long shoff, phoff, size; int bits, endian, shnum, shentsize, phentsize; ) // Section header. struct sh { unsigned type, link, info; unsigned long long flags, addr, offset, size, addralign, entsize; char *name; }; // Program header. struct ph { unsigned type, flags; unsigned long long offset, vaddr, paddr, filesz, memsz, align; }; static long long elf_get(char **p, int len) { long long result = ((TT.endian == 2) ? peek_be : peek_le)(*p, len); *p += len; return result; } static unsigned long long elf_long(char **p) { return elf_get(p, 4*(TT.bits+1)); } static unsigned elf_int(char **p) { return elf_get(p, 4); } static unsigned short elf_short(char **p) { return elf_get(p, 2); } static void get_sh(int i, struct sh *s) { char *shdr = TT.elf+TT.shoff+i*TT.shentsize; int name_offset; if (i >= TT.shnum || shdr > TT.elf+TT.size-TT.shentsize) { error_exit("%s: no shdr %d",TT.f,i); } name_offset = elf_int(&shdr); s->type = elf_int(&shdr); s->flags = elf_long(&shdr); s->addr = elf_long(&shdr); s->offset = elf_long(&shdr); s->size = elf_long(&shdr); s->link = elf_int(&shdr); s->info = elf_int(&shdr); s->addralign = elf_long(&shdr); s->entsize = elf_long(&shdr); if (!TT.shstrtab) s->name = "?"; else { s->name = TT.shstrtab + name_offset; if (s->name >= TT.elf+TT.size) error_exit("%s: shdr %d bad name", TT.f, i); if (s->offset >= TT.size-s->size && s->type != 8 /*SHT_NOBITS*/) error_exit("%s: shdr %d has bad offset/size %llu/%llu", TT.f, i, s->offset, s->size); } } static int find_section(char *spec, struct sh *s) { char *end; int i; // Valid section number? errno = 0; i = strtoul(spec, &end, 0); if (!errno && !*end && i < TT.shnum) { get_sh(i, s); return 1; } // Search the section names. for (i=0; i<TT.shnum; i++) { get_sh(i, s); if (!strcmp(s->name, spec)) return 1; } error_msg("%s: no section '%s", TT.f, spec); return 0; } static void get_ph(int i, struct ph *ph) { char *phdr = TT.elf+TT.phoff+i*TT.phentsize; if (phdr > TT.elf+TT.size-TT.phentsize) error_exit("%s: no phdr %d",TT.f,i); // Elf64_Phdr reordered fields. ph->type = elf_int(&phdr); if (TT.bits) { ph->flags = elf_int(&phdr); ph->offset = elf_long(&phdr); ph->vaddr = elf_long(&phdr); ph->paddr = elf_long(&phdr); ph->filesz = elf_long(&phdr); ph->memsz = elf_long(&phdr); ph->align = elf_long(&phdr); } else { ph->offset = elf_int(&phdr); ph->vaddr = elf_int(&phdr); ph->paddr = elf_int(&phdr); ph->filesz = elf_int(&phdr); ph->memsz = elf_int(&phdr); ph->flags = elf_int(&phdr); ph->align = elf_int(&phdr); } if (ph->offset >= TT.size-ph->filesz) error_exit("%s: phdr %d has bad offset/size %llu/%llu", TT.f, i, ph->offset, ph->filesz); } #define MAP(...) __VA_ARGS__ #define DECODER(name, values) \ static char *name(int type) { \ static char unknown[20]; \ struct {int v; char *s;} a[] = values; \ int i; \ \ for (i=0; i<ARRAY_LEN(a); i++) if (type==a[i].v) return a[i].s; \ sprintf(unknown, "0x%x", type); \ return unknown; \ } DECODER(dt_type, MAP({{0,"x(NULL)"},{1,"N(NEEDED)"},{2,"b(PLTRELSZ)"}, {3,"x(PLTGOT)"},{4,"x(HASH)"},{5,"x(STRTAB)"},{6,"x(SYMTAB)"},{7,"x(RELA)"}, {8,"b(RELASZ)"},{9,"b(RELAENT)"},{10,"b(STRSZ)"},{11,"b(SYMENT)"}, {12,"x(INIT)"},{13,"x(FINI)"},{14,"S(SONAME)"},{15,"R(RPATH)"}, {16,"x(SYMBOLIC)"},{17,"x(REL)"},{18,"b(RELSZ)"},{19,"b(RELENT)"}, {20,"P(PLTREL)"},{21,"x(DEBUG)"},{22,"x(TEXTREL)"},{23,"x(JMPREL)"}, {24,"d(BIND_NOW)"},{25,"x(INIT_ARRAY)"},{26,"x(FINI_ARRAY)"}, {27,"b(INIT_ARRAYSZ)"},{28,"b(FINI_ARRAYSZ)"},{29,"R(RUNPATH)"}, {30,"f(FLAGS)"},{32,"x(PREINIT_ARRAY)"},{33,"x(PREINIT_ARRAYSZ)"}, {35,"b(RELRSZ)"},{36,"x(RELR)"},{37,"b(RELRENT)"}, {0x6000000f,"x(ANDROID_REL)"},{0x60000010,"b(ANDROID_RELSZ)"}, {0x60000011,"x(ANDROID_RELA)"},{0x60000012,"b(ANDROID_RELASZ)"}, {0x6fffe000,"x(ANDROID_RELR)"},{0x6fffe001,"b(ANDROID_RELRSZ)"}, {0x6fffe003,"x(ANDROID_RELRENT)"},{0x6ffffef5,"x(GNU_HASH)"}, {0x6ffffef6,"x(TLSDESC_PLT)"},{0x6ffffef7,"x(TLSDESC_GOT)"}, {0x6ffffff0,"x(VERSYM)"},{0x6ffffff9,"d(RELACOUNT)"}, {0x6ffffffa,"d(RELCOUNT)"},{0x6ffffffb,"F(FLAGS_1)"}, {0x6ffffffc," (VERDEF)"},{0x6ffffffd,"d(VERDEFNUM)"}, {0x6ffffffe,"x(VERNEED)"},{0x6fffffff,"d(VERNEEDNUM)"}})) DECODER(et_type, MAP({{0,"NONE (None)"},{1,"REL (Relocatable file)"}, {2,"EXEC (Executable file)"},{3,"DYN (Shared object file)"}, {4,"CORE (Core file)"}})) DECODER(nt_type_core, MAP({{1,"NT_PRSTATUS"},{2,"NT_FPREGSET"}, {3,"NT_PRPSINFO"},{5,"NT_PLATFORM"},{6,"NT_AUXV"}, {0x46494c45,"NT_FILE"},{0x53494749,"NT_SIGINFO"}})) DECODER(nt_type_linux, MAP({{0x200,"NT_386_TLS"},{0x202, "NT_X86_XSTATE"}, {0x400,"NT_ARM_VFP"},{0x401,"NT_ARM_TLS"},{0x405,"NT_ARM_SVE"}})) DECODER(os_abi, MAP({{0,"UNIX - System V"}})) DECODER(ph_type, MAP({{0,"NULL"},{1,"LOAD"},{2,"DYNAMIC"},{3,"INTERP"}, {4,"NOTE"},{5,"SHLIB"},{6,"PHDR"},{7,"TLS"},{0x6474e550,"GNU_EH_FRAME"}, {0x6474e551,"GNU_STACK"},{0x6474e552,"GNU_RELRO"},{0x70000001,"EXIDX"}})) DECODER(sh_type, MAP({{0,"NULL"},{1,"PROGBITS"},{2,"SYMTAB"},{3,"STRTAB"}, {4,"RELA"},{5,"HASH"},{6,"DYNAMIC"},{7,"NOTE"},{8,"NOBITS"},{9,"REL"}, {10,"SHLIB"},{11,"DYNSYM"},{14,"INIT_ARRAY"},{15,"FINI_ARRAY"}, {16,"PREINIT_ARRAY"},{17,"GROUP"},{18,"SYMTAB_SHNDX"},{19,"RELR"}, {0x60000001,"ANDROID_REL"},{0x60000002,"ANDROID_RELA"}, {0x6fffff00,"ANDROID_RELR"},{0x6ffffff6,"GNU_HASH"}, {0x6ffffffd,"VERDEF"},{0x6ffffffe,"VERNEED"}, {0x6fffffff,"VERSYM"},{0x70000001,"ARM_EXIDX"}, {0x70000003,"ARM_ATTRIBUTES"}})) DECODER(stb_type, MAP({{0,"LOCAL"},{1,"GLOBAL"},{2,"WEAK"}})) DECODER(stt_type, MAP({{0,"NOTYPE"},{1,"OBJECT"},{2,"FUNC"},{3,"SECTION"}, {4,"FILE"},{5,"COMMON"},{6,"TLS"},{10,"GNU_IFUNC"}})) DECODER(stv_type, MAP({{0,"DEFAULT"},{1,"INTERNAL"},{2,"HIDDEN"}, {3,"PROTECTED"}})) static void show_symbols(struct sh *table, struct sh *strtab) { char *symtab = TT.elf+table->offset, *ndx; int numsym = table->size/(TT.bits ? 24 : 16), i; if (numsym == 0) return; xputc('\n'); printf("Symbol table '%s' contains %d entries:\n" " Num: %*s Size Type Bind Vis Ndx Name\n", table->name, numsym, 5+8*TT.bits, "Value"); for (i=0; i<numsym; i++) { int st_name = elf_int(&symtab), st_value, st_shndx; unsigned char st_info, st_other; long st_size; char *name; // The various fields were moved around for 64-bit. if (TT.bits) { st_info = *symtab++; st_other = *symtab++; st_shndx = elf_short(&symtab); st_value = elf_long(&symtab); st_size = elf_long(&symtab); } else { st_value = elf_int(&symtab); st_size = elf_int(&symtab); st_info = *symtab++; st_other = *symtab++; st_shndx = elf_short(&symtab); } name = TT.elf + strtab->offset + st_name; if (name >= TT.elf+TT.size) error_exit("%s: bad symbol name", TT.f); if (!st_shndx) ndx = "UND"; else if (st_shndx==0xfff1) ndx = "ABS"; else sprintf(ndx = toybuf, "%d", st_shndx); // TODO: look up and show any symbol versions with @ or @@. printf("%6d: %0*x %5ld %-7s %-6s %-9s%3s %s\n", i, 8*(TT.bits+1), st_value, st_size, stt_type(st_info & 0xf), stb_type(st_info >> 4), stv_type(st_other & 3), ndx, name); } } static int notematch(int namesz, char **p, char *expected, int len) { if (namesz != len || memcmp(*p, expected, namesz)) return 0; *p += namesz; return 1; } static void show_notes(long offset, long size) { char *note = TT.elf + offset; printf(" %-20s %10s\tDescription\n", "Owner", "Data size"); while (note < TT.elf+offset+size) { char *p = note, *desc; int namesz = elf_int(&p), descsz = elf_int(&p), type = elf_int(&p), j = 0; printf(" %-20.*s 0x%08x\t", namesz, p, descsz); if (notematch(namesz, &p, "GNU", 4)) { if (type == 1) { printf("NT_GNU_ABI_TAG\tOS: %s, ABI: %u.%u.%u", !elf_int(&p)?"Linux":"?", elf_int(&p), elf_int(&p), elf_int(&p)), j=1; } else if (type == 3) { printf("NT_GNU_BUILD_ID\t"); for (;j<descsz;j++) printf("%02x", *p++); } else if (type == 4) { printf("NT_GNU_GOLD_VERSION\t%.*s", descsz, p), j=1; } else p -= 4; } else if (notematch(namesz, &p, "Android", 8)) { if (type == 1) { printf("NT_VERSION\tAPI level %u", elf_int(&p)), j=1; if (descsz>=132) printf(", NDK %.64s (%.64s)", p, p+64); } else p -= 8; } else if (notematch(namesz, &p, "CORE", 5)) { if (*(desc = nt_type_core(type)) != '0') printf("%s", desc), j=1; } else if (notematch(namesz, &p, "LINUX", 6)) { if (*(desc = nt_type_linux(type)) != '0') printf("%s", desc), j=1; } // If we didn't do custom output above, show a hex dump. if (!j) { printf("0x%x\t", type); for (;j<descsz;j++) printf("%c%02x",!j?'\t':' ', *p++/*note[16+j]*/); } xputc('\n'); note += 3*4 + ((namesz+3)&~3) + ((descsz+3)&~3); } } static void scan_elf() { struct sh dynamic = {}, dynstr = {}, dynsym = {}, shstr = {}, strtab = {}, symtab = {}, s; struct ph ph; char *hdr = TT.elf; int type, machine, version, flags, entry, ehsize, phnum, shstrndx, i, j, w; if (TT.size < 45 || memcmp(hdr, "\177ELF", 4)) { error_msg("%s: not ELF", TT.f); return; } TT.bits = hdr[4] - 1; TT.endian = hdr[5]; if (TT.bits<0 || TT.bits>1 || TT.endian<1 || TT.endian>2 || hdr[6]!=1) { error_msg("%s: bad ELF", TT.f); return; } hdr += 16; // EI_NIDENT type = elf_short(&hdr); machine = elf_short(&hdr); version = elf_int(&hdr); entry = elf_long(&hdr); TT.phoff = elf_long(&hdr); TT.shoff = elf_long(&hdr); flags = elf_int(&hdr); ehsize = elf_short(&hdr); TT.phentsize = elf_short(&hdr); phnum = elf_short(&hdr); TT.shentsize = elf_short(&hdr); TT.shnum = elf_short(&hdr); shstrndx = elf_short(&hdr); // Set up the section header string table so we can use section header names. // Core files have shstrndx == 0. TT.shstrtab = 0; if (shstrndx != 0) { get_sh(shstrndx, &shstr); if (shstr.type != 3 /*SHT_STRTAB*/) { error_msg("%s: bad shstrndx", TT.f); return; } TT.shstrtab = TT.elf+shstr.offset; } if (toys.optc > 1) printf("\nFile: %s\n", TT.f); if (FLAG(h)) { printf("ELF Header:\n"); printf(" Magic: "); for (i=0; i<16; i++) printf("%02x%c", TT.elf[i], i==15?'\n':' '); printf(" Class: ELF%d\n", TT.bits?64:32); printf(" Data: 2's complement, %s endian\n", (TT.endian==2)?"big":"little"); printf(" Version: 1 (current)\n"); printf(" OS/ABI: %s\n", os_abi(TT.elf[7])); printf(" ABI Version: %d\n", TT.elf[8]); printf(" Type: %s\n", et_type(type)); printf(" Machine: %s\n", elf_arch_name(machine)); printf(" Version: 0x%x\n", version); printf(" Entry point address: 0x%x\n", entry); printf(" Start of program headers: %lld (bytes into file)\n", TT.phoff); printf(" Start of section headers: %lld (bytes into file)\n", TT.shoff); printf(" Flags: 0x%x\n", flags); printf(" Size of this header: %d (bytes)\n", ehsize); printf(" Size of program headers: %d (bytes)\n", TT.phentsize); printf(" Number of program headers: %d\n", phnum); printf(" Size of section headers: %d (bytes)\n", TT.shentsize); printf(" Number of section headers: %d\n", TT.shnum); printf(" Section header string table index: %d\n", shstrndx); } w = 8*(TT.bits+1); if (FLAG(S)) { if (!TT.shnum) printf("\nThere are no sections in this file.\n"); else { if (!FLAG(h)) { printf("There are %d section headers, starting at offset %#llx:\n", TT.shnum, TT.shoff); } printf("\n" "Section Headers:\n" " [Nr] %-20s %-14s %-*s %-6s %-6s ES Flg Lk Inf Al\n", "Name", "Type", w, "Address", "Off", "Size"); } } // We need to iterate through the section headers even if we're not // dumping them, to find specific sections. for (i=0; i<TT.shnum; i++) { get_sh(i, &s); if (s.type == 2 /*SHT_SYMTAB*/) symtab = s; else if (s.type == 6 /*SHT_DYNAMIC*/) dynamic = s; else if (s.type == 11 /*SHT_DYNSYM*/) dynsym = s; else if (s.type == 3 /*SHT_STRTAB*/) { if (!strcmp(s.name, ".strtab")) strtab = s; else if (!strcmp(s.name, ".dynstr")) dynstr = s; } if (FLAG(S)) { char sh_flags[12] = {}, *p = sh_flags; for (j=0; j<12; j++) if (s.flags&(1<<j)) *p++="WAXxMSILOTC"[j]; printf(" [%2d] %-20s %-14s %0*llx %06llx %06llx %02llx %3s %2d %2d %2lld\n", i, s.name, sh_type(s.type), w, s.addr, s.offset, s.size, s.entsize, sh_flags, s.link, s.info, s.addralign); } } if (FLAG(S) && TT.shnum) { printf("Key:\n" " (W)rite, (A)lloc, e(X)ecute, (M)erge, (S)trings, (I)nfo\n" " (L)ink order, (O)S, (G)roup, (T)LS, (C)ompressed, x=unknown\n"); } if (FLAG(l)) { xputc('\n'); if (!phnum) printf("There are no program headers in this file.\n"); else { if (!FLAG(h)) { printf("Elf file type is %s\n" "Entry point %#x\n" "There are %d program headers, starting at offset %lld\n" "\n", et_type(type), entry, phnum, TT.phoff); } printf("Program Headers:\n" " %-14s %-8s %-*s %-*s %-7s %-7s Flg Align\n", "Type", "Offset", w, "VirtAddr", w, "PhysAddr", "FileSiz", "MemSiz"); for (i=0; i<phnum; i++) { get_ph(i, &ph); printf(" %-14s 0x%06llx 0x%0*llx 0x%0*llx 0x%05llx 0x%05llx %c%c%c %#llx\n", ph_type(ph.type), ph.offset, w, ph.vaddr, w, ph.paddr, ph.filesz, ph.memsz, ph.flags&4?'R':' ', ph.flags&2?'W':' ', ph.flags&1?'E':' ', ph.align); if (ph.type == 3 /*PH_INTERP*/ && ph.filesz && ph.filesz) { printf(" [Requesting program interpreter: %*s]\n", (int) ph.filesz-1, TT.elf+ph.offset); } } printf("\n" " Section to Segment mapping:\n" " Segment Sections...\n"); for (i=0; i<phnum; i++) { get_ph(i, &ph); printf(" %02d ", i); for (j=0; j<TT.shnum; j++) { get_sh(j, &s); if (!*s.name) continue; if (s.offset >= ph.offset && s.offset+s.size <= ph.offset+ph.filesz) printf("%s ", s.name); } xputc('\n'); } } } // binutils ld emits a bunch of extra DT_NULL entries, so binutils readelf // uses two passes here! We just tell the truth, which matches -h. if (FLAG(d)) { char *dyn = TT.elf+dynamic.offset, *end = dyn+dynamic.size; xputc('\n'); if (!dynamic.size) printf("There is no dynamic section in this file.\n"); else printf("Dynamic section at offset 0x%llx contains %lld entries:\n" " %-*s %-20s %s\n", dynamic.offset, dynamic.size/dynamic.entsize, w+2, "Tag", "Type", "Name/Value"); while (dyn < end) { unsigned long long tag = elf_long(&dyn), val = elf_long(&dyn); char *type = dt_type(tag); printf(" 0x%0*llx %-20s ", w, tag, *type=='0' ? type : type+1); if (*type == 'd') printf("%lld\n", val); else if (*type == 'b') printf("%lld (bytes)\n", val); else if (*type == 's') printf("%s\n", TT.elf+dynstr.offset+val); else if (*type == 'f' || *type == 'F') { struct bitname { int bit; char *s; } df_names[] = {{0, "ORIGIN"},{1,"SYMBOLIC"},{2,"TEXTREL"}, {3,"BIND_NOW"},{4,"STATIC_TLS"},{}}, df_1_names[]={{0,"NOW"},{1,"GLOBAL"},{2,"GROUP"},{3,"NODELETE"}, {5,"INITFIRST"},{27,"PIE"},{}}, *names = *type == 'f' ? df_names : df_1_names; int mask; if (*type == 'F') printf("Flags: "); for (j=0; names[j].s; j++) { if (val & (mask=(1<<names[j].bit))) { printf("%s%s", names[j].s, (val &= ~mask) ? " " : ""); } } if (val) printf("0x%llx", val); xputc('\n'); } else if (*type == 'N' || *type == 'R' || *type == 'S') { printf("%s: [%s]\n", *type=='N' ? "Shared library" : (*type=='R' ? "Library runpath" : "Library soname"), TT.elf+dynstr.offset+val); } else if (*type == 'P') { type = dt_type(val); j = strlen(type); if (*type != '0') type += 2, j -= 3; printf("%*.*s\n", j, j, type); } else printf("0x%llx\n", val); } } if (FLAG(dyn_syms)) show_symbols(&dynsym, &dynstr); if (FLAG(s)) show_symbols(&symtab, &strtab); if (FLAG(n)) { int found = 0; for (i=0; i<TT.shnum; i++) { get_sh(i, &s); if (s.type == 7 /*SHT_NOTE*/) { printf("\nDisplaying notes found in: %s\n", s.name); show_notes(s.offset, s.size); found = 1; } } for (i=0; !found && i<phnum; i++) { get_ph(i, &ph); if (ph.type == 4 /*PT_NOTE*/) { printf("\n" "Displaying notes found at file offset 0x%llx with length 0x%llx:\n", ph.offset, ph.filesz); show_notes(ph.offset, ph.filesz); } } } if (FLAG(x)) { if (find_section(TT.x, &s)) { char *p = TT.elf+s.offset; long offset = 0; printf("\nHex dump of section '%s':\n", s.name); while (offset < s.size) { int space = 2*16 + 16/4; printf(" 0x%08lx ", offset); for (i=0; i<16 && offset < s.size; offset++) { space -= printf("%02x%s", *p++, ++i%4 ? "" : " "); } printf("%*s", space, ""); for (p-=i; i; i--, p++) putchar(*p>=' ' && *p<='~' ? *p : '.'); xputc('\n'); } printf("\n"); } } if (FLAG(p)) { if (find_section(TT.p, &s)) { char *begin = TT.elf+s.offset, *end = begin + s.size, *p = begin; int any = 0; printf("\nString dump of section '%s':\n", s.name); for (; p < end; p++) { if (isprint(*p)) { printf(" [%6tx] ", p-begin); while (p < end && isprint(*p)) putchar(*p++); xputc('\n'); any=1; } } if (!any) printf(" No strings found in this section.\n"); printf("\n"); } } } void readelf_main(void) { char **arg; int all = FLAG_d|FLAG_h|FLAG_l|FLAG_n|FLAG_S|FLAG_s|FLAG_dyn_syms; if (FLAG(a)) toys.optflags |= all; if (FLAG(e)) toys.optflags |= FLAG_h|FLAG_l|FLAG_S; if (FLAG(s)) toys.optflags |= FLAG_dyn_syms; if (!(toys.optflags & (all|FLAG_p|FLAG_x))) help_exit("needs a flag"); for (arg = toys.optargs; *arg; arg++) { int fd = open(TT.f = *arg, O_RDONLY); struct stat sb; if (fd == -1) perror_msg("%s", TT.f); else { if (fstat(fd, &sb)) perror_msg("%s", TT.f); else if (!sb.st_size) error_msg("%s: empty", TT.f); else if (!S_ISREG(sb.st_mode)) error_msg("%s: not a regular file",TT.f); else { TT.elf = xmmap(NULL, TT.size=sb.st_size, PROT_READ, MAP_SHARED, fd, 0); scan_elf(); munmap(TT.elf, TT.size); } close(fd); } } }