1 /* $OpenBSD: init.c,v 1.18 2023/02/27 15:00:17 deraadt Exp $ */ 2 /* 3 * Copyright (c) 2014,2015 Philip Guenther <guenther@openbsd.org> 4 * 5 * Permission to use, copy, modify, and distribute this software for any 6 * purpose with or without fee is hereby granted, provided that the above 7 * copyright notice and this permission notice appear in all copies. 8 * 9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 16 */ 17 18 19 #define _DYN_LOADER 20 21 #include <sys/types.h> 22 #include <sys/syscall.h> 23 #include <sys/timetc.h> /* timekeep */ 24 25 #ifndef PIC 26 #include <sys/mman.h> 27 #endif 28 29 #include <tib.h> 30 #include <limits.h> /* NAME_MAX */ 31 #include <link.h> 32 #include <stdlib.h> /* atexit */ 33 #include <string.h> 34 #include <unistd.h> 35 36 #include "init.h" 37 38 #if defined(APIWARN) 39 __warn_references(syscall, 40 "syscall() may go away, please rewrite code to use direct calls"); 41 #endif 42 43 #define MAX(a,b) (((a)>(b))?(a):(b)) 44 45 #ifdef TIB_EXTRA_ALIGN 46 # define TIB_ALIGN MAX(__alignof__(struct tib), TIB_EXTRA_ALIGN) 47 #else 48 # define TIB_ALIGN __alignof__(struct tib) 49 #endif 50 51 /* XXX should be in an include file shared with csu */ 52 char ***_csu_finish(char **_argv, char **_envp, void (*_cleanup)(void)); 53 54 /* provide definitions for these */ 55 int _pagesize = 0; 56 struct timekeep *_timekeep; 57 58 /* 59 * In dynamically linked binaries environ and __progname are overridden by 60 * the definitions in ld.so. 61 */ 62 char **environ __attribute__((weak)) = NULL; 63 char *__progname __attribute__((weak)) = NULL; 64 65 66 #ifndef PIC 67 struct dl_phdr_info _static_phdr_info __relro = { .dlpi_name = "a.out" }; 68 69 static inline void early_static_init(char **_argv, char **_envp); 70 static inline void setup_static_tib(Elf_Phdr *_phdr, int _phnum); 71 72 /* provided by the linker */ 73 extern Elf_Ehdr __executable_start[] __attribute__((weak)); 74 #endif /* PIC */ 75 76 /* provide definitions for these */ 77 const dl_cb *_dl_cb __relro = NULL; 78 79 int pinsyscall(int, void *, size_t); 80 PROTO_NORMAL(pinsyscall); 81 82 int HIDDEN(execve)(const char *, char *const *, char *const *) 83 __attribute__((weak)); 84 85 void _libc_preinit(int, char **, char **, dl_cb_cb *) __dso_hidden; 86 void 87 _libc_preinit(int argc, char **argv, char **envp, dl_cb_cb *cb) 88 { 89 AuxInfo *aux; 90 #ifndef PIC 91 Elf_Phdr *phdr = NULL; 92 int phnum = 0; 93 94 /* static libc in a static link? */ 95 if (cb == NULL) 96 early_static_init(argv, envp); 97 #endif /* !PIC */ 98 99 if (cb != NULL) 100 _dl_cb = cb(DL_CB_CUR); 101 102 /* Extract useful bits from the auxiliary vector */ 103 while (*envp++ != NULL) 104 ; 105 for (aux = (void *)envp; aux->au_id != AUX_null; aux++) { 106 switch (aux->au_id) { 107 case AUX_pagesz: 108 _pagesize = aux->au_v; 109 break; 110 #ifndef PIC 111 case AUX_base: 112 _static_phdr_info.dlpi_addr = aux->au_v; 113 break; 114 case AUX_phdr: 115 phdr = (void *)aux->au_v; 116 break; 117 case AUX_phnum: 118 phnum = aux->au_v; 119 break; 120 #endif /* !PIC */ 121 case AUX_openbsd_timekeep: 122 if (_tc_get_timecount) { 123 _timekeep = (void *)aux->au_v; 124 if (_timekeep && 125 _timekeep->tk_version != TK_VERSION) 126 _timekeep = NULL; 127 } 128 if (issetugid() == 0 && getenv("LIBC_NOUSERTC")) 129 _timekeep = NULL; 130 break; 131 } 132 } 133 134 #ifndef PIC 135 if (cb == NULL && phdr == NULL && __executable_start != NULL) { 136 /* 137 * Static non-PIE processes don't get an AUX vector, 138 * so find the phdrs through the ELF header 139 */ 140 _static_phdr_info.dlpi_addr = (Elf_Addr)__executable_start; 141 phdr = (void *)((char *)__executable_start + 142 __executable_start->e_phoff); 143 phnum = __executable_start->e_phnum; 144 } 145 _static_phdr_info.dlpi_phdr = phdr; 146 _static_phdr_info.dlpi_phnum = phnum; 147 148 /* static libc in a static link? */ 149 if (cb == NULL) { 150 setup_static_tib(phdr, phnum); 151 152 #if !defined(__hppa__) 153 if (&HIDDEN(execve)) { 154 extern const int _execve_size; 155 156 pinsyscall(SYS_execve, &HIDDEN(execve), _execve_size); 157 } 158 #endif 159 } 160 161 /* 162 * If a static binary has text relocations (DT_TEXT), then un-writeable 163 * segments were not made immutable by the kernel. Textrel and RELRO 164 * changes have now been completed and permissions corrected, so these 165 * regions can become immutable. 166 */ 167 if (phdr) { 168 int i; 169 170 for (i = 0; i < phnum; i++) { 171 if (phdr[i].p_type == PT_LOAD && 172 (phdr[i].p_flags & PF_W) == 0) 173 mimmutable((void *)(_static_phdr_info.dlpi_addr + 174 phdr[i].p_vaddr), phdr[i].p_memsz); 175 } 176 } 177 #endif /* !PIC */ 178 } 179 180 /* ARM just had to be different... */ 181 #ifndef __arm__ 182 # define TYPE "@" 183 #else 184 # define TYPE "%" 185 #endif 186 187 #ifdef __LP64__ 188 # define VALUE_ALIGN ".balign 8" 189 # define VALUE_DIRECTIVE ".quad" 190 #else 191 # define VALUE_ALIGN ".balign 4" 192 # ifdef __hppa__ 193 /* hppa just had to be different: func pointers prefix with 'P%' */ 194 # define VALUE_DIRECTIVE ".int P%" 195 # else 196 # define VALUE_DIRECTIVE ".int" 197 # endif 198 #endif 199 200 #define ADD_TO_ARRAY(func, which) \ 201 __asm( " .section ."#which",\"a\","TYPE#which"\n " \ 202 VALUE_ALIGN"\n "VALUE_DIRECTIVE" "#func"\n .previous") 203 204 #ifdef PIC 205 ADD_TO_ARRAY(_libc_preinit, init_array); 206 #else 207 ADD_TO_ARRAY(_libc_preinit, preinit_array); 208 #endif 209 210 /* 211 * In dynamic links, invoke ld.so's dl_clean_boot() callback, if any, 212 * and register its cleanup. 213 */ 214 char *** 215 _csu_finish(char **argv, char **envp, void (*cleanup)(void)) 216 { 217 if (_dl_cb != NULL && _dl_cb->dl_clean_boot != NULL) 218 _dl_cb->dl_clean_boot(); 219 220 if (cleanup != NULL) 221 atexit(cleanup); 222 223 return &environ; 224 } 225 226 #ifndef PIC 227 /* 228 * static libc in a static link? Then set up __progname and environ 229 */ 230 static inline void 231 early_static_init(char **argv, char **envp) 232 { 233 static char progname_storage[NAME_MAX+1]; 234 235 environ = envp; 236 237 /* set up __progname */ 238 if (*argv != NULL) { /* NULL ptr if argc = 0 */ 239 const char *p = strrchr(*argv, '/'); 240 241 if (p == NULL) 242 p = *argv; 243 else 244 p++; 245 strlcpy(progname_storage, p, sizeof(progname_storage)); 246 } 247 __progname = progname_storage; 248 } 249 250 /* 251 * static TLS handling 252 */ 253 #define ELF_ROUND(x,malign) (((x) + (malign)-1) & ~((malign)-1)) 254 255 /* for static binaries, the location and size of the TLS image */ 256 static void *static_tls __relro; 257 static size_t static_tls_fsize __relro; 258 259 size_t _static_tls_size __relro = 0; 260 int _static_tls_align __relro; 261 int _static_tls_align_offset __relro; 262 263 static inline void 264 setup_static_tib(Elf_Phdr *phdr, int phnum) 265 { 266 struct tib *tib; 267 char *base; 268 int i; 269 270 _static_tls_align = TIB_ALIGN; 271 if (phdr != NULL) { 272 for (i = 0; i < phnum; i++) { 273 if (phdr[i].p_type != PT_TLS) 274 continue; 275 if (phdr[i].p_memsz == 0) 276 break; 277 if (phdr[i].p_memsz < phdr[i].p_filesz) 278 break; /* invalid */ 279 if (phdr[i].p_align > getpagesize()) 280 break; /* nope */ 281 _static_tls_align = MAX(phdr[i].p_align, TIB_ALIGN); 282 #if TLS_VARIANT == 1 283 /* 284 * Variant 1 places the data after the TIB. If the 285 * TLS alignment is larger than the TIB alignment 286 * then we may need to pad in front of the TIB to 287 * place the TLS data on the proper alignment. 288 * Example: p_align=16 sizeof(TIB)=52 align(TIB)=4 289 * - need to offset the TIB 12 bytes from the start 290 * - to place ths TLS data at offset 64 291 */ 292 _static_tls_size = phdr[i].p_memsz; 293 _static_tls_align_offset = 294 ELF_ROUND(sizeof(struct tib), _static_tls_align) - 295 sizeof(struct tib); 296 #elif TLS_VARIANT == 2 297 /* 298 * Variant 2 places the data before the TIB 299 * so we need to round up the size to the 300 * TLS data alignment TIB's alignment. 301 * Example A: p_memsz=24 p_align=16 align(TIB)=8 302 * - need to allocate 32 bytes for TLS as compiler 303 * - will give the first TLS symbol an offset of -32 304 * Example B: p_memsz=4 p_align=4 align(TIB)=8 305 * - need to allocate 8 bytes so that the TIB is 306 * - properly aligned 307 */ 308 _static_tls_size = ELF_ROUND(phdr[i].p_memsz, 309 phdr[i].p_align); 310 _static_tls_align_offset = ELF_ROUND(_static_tls_size, 311 _static_tls_align) - _static_tls_size; 312 #endif 313 if (phdr[i].p_vaddr != 0 && phdr[i].p_filesz != 0) { 314 static_tls = (void *)phdr[i].p_vaddr + 315 _static_phdr_info.dlpi_addr; 316 static_tls_fsize = phdr[i].p_filesz; 317 } 318 break; 319 } 320 } 321 322 base = mmap(NULL, _static_tls_size + _static_tls_align_offset 323 + sizeof *tib, PROT_READ|PROT_WRITE, MAP_ANON|MAP_PRIVATE, -1, 0); 324 325 tib = _static_tls_init(base, NULL); 326 tib->tib_tid = getthrid(); 327 TCB_SET(TIB_TO_TCB(tib)); 328 #if ! TCB_HAVE_MD_GET 329 _libc_single_tcb = TIB_TO_TCB(tib); 330 #endif 331 } 332 333 struct tib * 334 _static_tls_init(char *base, void *thread) 335 { 336 struct tib *tib; 337 338 base += _static_tls_align_offset; 339 # if TLS_VARIANT == 1 340 tib = (struct tib *)base; 341 base += sizeof(struct tib); 342 # elif TLS_VARIANT == 2 343 tib = (struct tib *)(base + _static_tls_size); 344 # endif 345 346 if (_static_tls_size) { 347 if (static_tls != NULL) 348 memcpy(base, static_tls, static_tls_fsize); 349 memset(base + static_tls_fsize, 0, 350 _static_tls_size - static_tls_fsize); 351 } 352 353 TIB_INIT(tib, NULL, thread); 354 return tib; 355 } 356 #endif /* !PIC */ 357