1 /* $OpenBSD: init.c,v 1.23 2024/07/14 09:48:48 jca 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 #define MAX(a,b) (((a)>(b))?(a):(b)) 39 40 #ifdef TIB_EXTRA_ALIGN 41 # define TIB_ALIGN MAX(__alignof__(struct tib), TIB_EXTRA_ALIGN) 42 #else 43 # define TIB_ALIGN __alignof__(struct tib) 44 #endif 45 46 /* XXX should be in an include file shared with csu */ 47 char ***_csu_finish(char **_argv, char **_envp, void (*_cleanup)(void)); 48 49 /* provide definitions for these */ 50 int _pagesize = 0; 51 struct timekeep *_timekeep; 52 unsigned long _hwcap, _hwcap2; 53 int _hwcap_avail, _hwcap2_avail; 54 55 /* 56 * In dynamically linked binaries environ and __progname are overridden by 57 * the definitions in ld.so. 58 */ 59 char **environ __attribute__((weak)) = NULL; 60 char *__progname __attribute__((weak)) = NULL; 61 62 63 #ifndef PIC 64 struct dl_phdr_info _static_phdr_info __relro = { .dlpi_name = "a.out" }; 65 66 static inline void early_static_init(char **_argv, char **_envp); 67 static inline void setup_static_tib(Elf_Phdr *_phdr, int _phnum); 68 69 /* provided by the linker */ 70 extern Elf_Ehdr __executable_start[] __attribute__((weak)); 71 #endif /* PIC */ 72 73 /* provide definitions for these */ 74 const dl_cb *_dl_cb __relro = NULL; 75 76 int HIDDEN(execve)(const char *, char *const *, char *const *) 77 __attribute__((weak)); 78 79 void _libc_preinit(int, char **, char **, dl_cb_cb *) __dso_hidden; 80 void 81 _libc_preinit(int argc, char **argv, char **envp, dl_cb_cb *cb) 82 { 83 AuxInfo *aux; 84 #ifndef PIC 85 Elf_Phdr *phdr = NULL; 86 int phnum = 0; 87 88 /* static libc in a static link? */ 89 if (cb == NULL) 90 early_static_init(argv, envp); 91 #endif /* !PIC */ 92 93 if (cb != NULL) 94 _dl_cb = cb(DL_CB_CUR); 95 96 /* Extract useful bits from the auxiliary vector */ 97 while (*envp++ != NULL) 98 ; 99 for (aux = (void *)envp; aux->au_id != AUX_null; aux++) { 100 switch (aux->au_id) { 101 case AUX_hwcap: 102 _hwcap = aux->au_v; 103 _hwcap_avail = 1; 104 break; 105 case AUX_hwcap2: 106 _hwcap2 = aux->au_v; 107 _hwcap2_avail = 1; 108 break; 109 case AUX_pagesz: 110 _pagesize = aux->au_v; 111 break; 112 #ifndef PIC 113 case AUX_base: 114 _static_phdr_info.dlpi_addr = aux->au_v; 115 break; 116 case AUX_phdr: 117 phdr = (void *)aux->au_v; 118 break; 119 case AUX_phnum: 120 phnum = aux->au_v; 121 break; 122 #endif /* !PIC */ 123 case AUX_openbsd_timekeep: 124 if (_tc_get_timecount) { 125 _timekeep = (void *)aux->au_v; 126 if (_timekeep && 127 _timekeep->tk_version != TK_VERSION) 128 _timekeep = NULL; 129 } 130 if (issetugid() == 0 && getenv("LIBC_NOUSERTC")) 131 _timekeep = NULL; 132 break; 133 } 134 } 135 136 #ifndef PIC 137 if (cb == NULL && phdr == NULL && __executable_start != NULL) { 138 /* 139 * Static non-PIE processes don't get an AUX vector, 140 * so find the phdrs through the ELF header 141 */ 142 phdr = (void *)((char *)__executable_start + 143 __executable_start->e_phoff); 144 phnum = __executable_start->e_phnum; 145 } 146 _static_phdr_info.dlpi_phdr = phdr; 147 _static_phdr_info.dlpi_phnum = phnum; 148 149 /* static libc in a static link? */ 150 if (cb == NULL) 151 setup_static_tib(phdr, phnum); 152 153 /* 154 * If a static binary has text relocations (DT_TEXT), then un-writeable 155 * segments were not made immutable by the kernel. Textrel and RELRO 156 * changes have now been completed and permissions corrected, so these 157 * regions can become immutable. 158 */ 159 if (phdr) { 160 int i; 161 162 for (i = 0; i < phnum; i++) { 163 if (phdr[i].p_type == PT_LOAD && 164 (phdr[i].p_flags & PF_W) == 0) 165 mimmutable((void *)(_static_phdr_info.dlpi_addr + 166 phdr[i].p_vaddr), phdr[i].p_memsz); 167 } 168 } 169 #endif /* !PIC */ 170 } 171 172 /* ARM just had to be different... */ 173 #ifndef __arm__ 174 # define TYPE "@" 175 #else 176 # define TYPE "%" 177 #endif 178 179 #ifdef __LP64__ 180 # define VALUE_ALIGN ".balign 8" 181 # define VALUE_DIRECTIVE ".quad" 182 #else 183 # define VALUE_ALIGN ".balign 4" 184 # ifdef __hppa__ 185 /* hppa just had to be different: func pointers prefix with 'P%' */ 186 # define VALUE_DIRECTIVE ".int P%" 187 # else 188 # define VALUE_DIRECTIVE ".int" 189 # endif 190 #endif 191 192 #define ADD_TO_ARRAY(func, which) \ 193 __asm( " .section ."#which",\"a\","TYPE#which"\n " \ 194 VALUE_ALIGN"\n "VALUE_DIRECTIVE" "#func"\n .previous") 195 196 #ifdef PIC 197 ADD_TO_ARRAY(_libc_preinit, init_array); 198 #else 199 ADD_TO_ARRAY(_libc_preinit, preinit_array); 200 #endif 201 202 /* 203 * In dynamic links, invoke ld.so's dl_clean_boot() callback, if any, 204 * and register its cleanup. 205 */ 206 char *** 207 _csu_finish(char **argv, char **envp, void (*cleanup)(void)) 208 { 209 if (_dl_cb != NULL && _dl_cb->dl_clean_boot != NULL) 210 _dl_cb->dl_clean_boot(); 211 212 if (cleanup != NULL) 213 atexit(cleanup); 214 215 return &environ; 216 } 217 218 #ifndef PIC 219 /* 220 * static libc in a static link? Then set up __progname and environ 221 */ 222 static inline void 223 early_static_init(char **argv, char **envp) 224 { 225 static char progname_storage[NAME_MAX+1]; 226 227 environ = envp; 228 229 /* set up __progname */ 230 if (*argv != NULL) { /* NULL ptr if argc = 0 */ 231 const char *p = strrchr(*argv, '/'); 232 233 if (p == NULL) 234 p = *argv; 235 else 236 p++; 237 strlcpy(progname_storage, p, sizeof(progname_storage)); 238 } 239 __progname = progname_storage; 240 } 241 242 /* 243 * static TLS handling 244 */ 245 #define ELF_ROUND(x,malign) (((x) + (malign)-1) & ~((malign)-1)) 246 247 /* for static binaries, the location and size of the TLS image */ 248 static void *static_tls __relro; 249 static size_t static_tls_fsize __relro; 250 251 size_t _static_tls_size __relro = 0; 252 int _static_tls_align __relro; 253 int _static_tls_align_offset __relro; 254 255 static inline void 256 setup_static_tib(Elf_Phdr *phdr, int phnum) 257 { 258 struct tib *tib; 259 char *base; 260 int i; 261 262 _static_tls_align = TIB_ALIGN; 263 if (phdr != NULL) { 264 for (i = 0; i < phnum; i++) { 265 if (phdr[i].p_type != PT_TLS) 266 continue; 267 if (phdr[i].p_memsz == 0) 268 break; 269 if (phdr[i].p_memsz < phdr[i].p_filesz) 270 break; /* invalid */ 271 if (phdr[i].p_align > getpagesize()) 272 break; /* nope */ 273 _static_tls_align = MAX(phdr[i].p_align, TIB_ALIGN); 274 #if TLS_VARIANT == 1 275 /* 276 * Variant 1 places the data after the TIB. If the 277 * TLS alignment is larger than the TIB alignment 278 * then we may need to pad in front of the TIB to 279 * place the TLS data on the proper alignment. 280 * Example: p_align=16 sizeof(TIB)=52 align(TIB)=4 281 * - need to offset the TIB 12 bytes from the start 282 * - to place ths TLS data at offset 64 283 */ 284 _static_tls_size = phdr[i].p_memsz; 285 _static_tls_align_offset = 286 ELF_ROUND(sizeof(struct tib), _static_tls_align) - 287 sizeof(struct tib); 288 #elif TLS_VARIANT == 2 289 /* 290 * Variant 2 places the data before the TIB 291 * so we need to round up the size to the 292 * TLS data alignment TIB's alignment. 293 * Example A: p_memsz=24 p_align=16 align(TIB)=8 294 * - need to allocate 32 bytes for TLS as compiler 295 * - will give the first TLS symbol an offset of -32 296 * Example B: p_memsz=4 p_align=4 align(TIB)=8 297 * - need to allocate 8 bytes so that the TIB is 298 * - properly aligned 299 */ 300 _static_tls_size = ELF_ROUND(phdr[i].p_memsz, 301 phdr[i].p_align); 302 _static_tls_align_offset = ELF_ROUND(_static_tls_size, 303 _static_tls_align) - _static_tls_size; 304 #endif 305 if (phdr[i].p_vaddr != 0 && phdr[i].p_filesz != 0) { 306 static_tls = (void *)phdr[i].p_vaddr + 307 _static_phdr_info.dlpi_addr; 308 static_tls_fsize = phdr[i].p_filesz; 309 } 310 break; 311 } 312 } 313 314 base = mmap(NULL, _static_tls_size + _static_tls_align_offset 315 + sizeof *tib, PROT_READ|PROT_WRITE, MAP_ANON|MAP_PRIVATE, -1, 0); 316 317 tib = _static_tls_init(base, NULL); 318 tib->tib_tid = getthrid(); 319 TCB_SET(TIB_TO_TCB(tib)); 320 #if ! TCB_HAVE_MD_GET 321 _libc_single_tcb = TIB_TO_TCB(tib); 322 #endif 323 } 324 325 struct tib * 326 _static_tls_init(char *base, void *thread) 327 { 328 struct tib *tib; 329 330 base += _static_tls_align_offset; 331 # if TLS_VARIANT == 1 332 tib = (struct tib *)base; 333 base += sizeof(struct tib); 334 # elif TLS_VARIANT == 2 335 tib = (struct tib *)(base + _static_tls_size); 336 # endif 337 338 if (_static_tls_size) { 339 if (static_tls != NULL) 340 memcpy(base, static_tls, static_tls_fsize); 341 memset(base + static_tls_fsize, 0, 342 _static_tls_size - static_tls_fsize); 343 } 344 345 TIB_INIT(tib, NULL, thread); 346 return tib; 347 } 348 #endif /* !PIC */ 349