1 /* $OpenBSD: init.c,v 1.12 2023/01/16 07:09:12 guenther 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 53 /* 54 * In dynamically linked binaries environ and __progname are overridden by 55 * the definitions in ld.so. 56 */ 57 char **environ __attribute__((weak)) = NULL; 58 char *__progname __attribute__((weak)) = NULL; 59 60 61 #ifndef PIC 62 struct dl_phdr_info _static_phdr_info __relro = { .dlpi_name = "a.out" }; 63 64 static inline void early_static_init(char **_argv, char **_envp); 65 static inline void setup_static_tib(Elf_Phdr *_phdr, int _phnum); 66 67 /* provided by the linker */ 68 extern Elf_Ehdr __executable_start[] __attribute__((weak)); 69 #endif /* PIC */ 70 71 /* provide definitions for these */ 72 const dl_cb *_dl_cb __relro = NULL; 73 74 void _libc_preinit(int, char **, char **, dl_cb_cb *) __dso_hidden; 75 void 76 _libc_preinit(int argc, char **argv, char **envp, dl_cb_cb *cb) 77 { 78 AuxInfo *aux; 79 #ifndef PIC 80 Elf_Phdr *phdr = NULL; 81 int phnum = 0; 82 83 /* static libc in a static link? */ 84 if (cb == NULL) 85 early_static_init(argv, envp); 86 #endif /* !PIC */ 87 88 if (cb != NULL) 89 _dl_cb = cb(DL_CB_CUR); 90 91 /* Extract useful bits from the auxiliary vector */ 92 while (*envp++ != NULL) 93 ; 94 for (aux = (void *)envp; aux->au_id != AUX_null; aux++) { 95 switch (aux->au_id) { 96 case AUX_pagesz: 97 _pagesize = aux->au_v; 98 break; 99 #ifndef PIC 100 case AUX_base: 101 _static_phdr_info.dlpi_addr = aux->au_v; 102 break; 103 case AUX_phdr: 104 phdr = (void *)aux->au_v; 105 break; 106 case AUX_phnum: 107 phnum = aux->au_v; 108 break; 109 #endif /* !PIC */ 110 case AUX_openbsd_timekeep: 111 if (_tc_get_timecount) { 112 _timekeep = (void *)aux->au_v; 113 if (_timekeep && 114 _timekeep->tk_version != TK_VERSION) 115 _timekeep = NULL; 116 } 117 if (issetugid() == 0 && getenv("LIBC_NOUSERTC")) 118 _timekeep = NULL; 119 break; 120 } 121 } 122 123 #ifndef PIC 124 if (cb == NULL && phdr == NULL && __executable_start != NULL) { 125 /* 126 * Static non-PIE processes don't get an AUX vector, 127 * so find the phdrs through the ELF header 128 */ 129 _static_phdr_info.dlpi_addr = (Elf_Addr)__executable_start; 130 phdr = (void *)((char *)__executable_start + 131 __executable_start->e_phoff); 132 phnum = __executable_start->e_phnum; 133 } 134 _static_phdr_info.dlpi_phdr = phdr; 135 _static_phdr_info.dlpi_phnum = phnum; 136 137 /* static libc in a static link? */ 138 if (cb == NULL) 139 setup_static_tib(phdr, phnum); 140 141 /* 142 * If a static binary has text relocations (DT_TEXT), then un-writeable 143 * segments were not made immutable by the kernel. Textrel and RELRO 144 * changes have now been completed and permissions corrected, so these 145 * regions can become immutable. 146 */ 147 if (phdr) { 148 int i; 149 150 for (i = 0; i < phnum; i++) { 151 if (phdr[i].p_type == PT_LOAD && 152 (phdr[i].p_flags & PF_W) == 0) 153 mimmutable((void *)(_static_phdr_info.dlpi_addr + 154 phdr[i].p_vaddr), phdr[i].p_memsz); 155 } 156 } 157 #endif /* !PIC */ 158 } 159 160 /* ARM just had to be different... */ 161 #ifndef __arm__ 162 # define TYPE "@" 163 #else 164 # define TYPE "%" 165 #endif 166 167 #ifdef __LP64__ 168 # define VALUE_ALIGN ".balign 8" 169 # define VALUE_DIRECTIVE ".quad" 170 #else 171 # define VALUE_ALIGN ".balign 4" 172 # ifdef __hppa__ 173 /* hppa just had to be different: func pointers prefix with 'P%' */ 174 # define VALUE_DIRECTIVE ".int P%" 175 # else 176 # define VALUE_DIRECTIVE ".int" 177 # endif 178 #endif 179 180 #define ADD_TO_ARRAY(func, which) \ 181 __asm( " .section ."#which",\"a\","TYPE#which"\n " \ 182 VALUE_ALIGN"\n "VALUE_DIRECTIVE" "#func"\n .previous") 183 184 #ifdef PIC 185 ADD_TO_ARRAY(_libc_preinit, init_array); 186 #else 187 ADD_TO_ARRAY(_libc_preinit, preinit_array); 188 #endif 189 190 /* 191 * In dynamic links, invoke ld.so's dl_clean_boot() callback, if any, 192 * and register its cleanup. 193 */ 194 char *** 195 _csu_finish(char **argv, char **envp, void (*cleanup)(void)) 196 { 197 if (_dl_cb != NULL && _dl_cb->dl_clean_boot != NULL) 198 _dl_cb->dl_clean_boot(); 199 200 if (cleanup != NULL) 201 atexit(cleanup); 202 203 return &environ; 204 } 205 206 #ifndef PIC 207 /* 208 * static libc in a static link? Then set up __progname and environ 209 */ 210 static inline void 211 early_static_init(char **argv, char **envp) 212 { 213 static char progname_storage[NAME_MAX+1]; 214 215 environ = envp; 216 217 /* set up __progname */ 218 if (*argv != NULL) { /* NULL ptr if argc = 0 */ 219 const char *p = strrchr(*argv, '/'); 220 221 if (p == NULL) 222 p = *argv; 223 else 224 p++; 225 strlcpy(progname_storage, p, sizeof(progname_storage)); 226 } 227 __progname = progname_storage; 228 } 229 230 /* 231 * static TLS handling 232 */ 233 #define ELF_ROUND(x,malign) (((x) + (malign)-1) & ~((malign)-1)) 234 235 /* for static binaries, the location and size of the TLS image */ 236 static void *static_tls __relro; 237 static size_t static_tls_fsize __relro; 238 239 size_t _static_tls_size __relro = 0; 240 int _static_tls_align __relro; 241 int _static_tls_align_offset __relro; 242 243 static inline void 244 setup_static_tib(Elf_Phdr *phdr, int phnum) 245 { 246 struct tib *tib; 247 char *base; 248 int i; 249 250 _static_tls_align = TIB_ALIGN; 251 if (phdr != NULL) { 252 for (i = 0; i < phnum; i++) { 253 if (phdr[i].p_type != PT_TLS) 254 continue; 255 if (phdr[i].p_memsz == 0) 256 break; 257 if (phdr[i].p_memsz < phdr[i].p_filesz) 258 break; /* invalid */ 259 if (phdr[i].p_align > getpagesize()) 260 break; /* nope */ 261 _static_tls_align = MAX(phdr[i].p_align, TIB_ALIGN); 262 #if TLS_VARIANT == 1 263 /* 264 * Variant 1 places the data after the TIB. If the 265 * TLS alignment is larger than the TIB alignment 266 * then we may need to pad in front of the TIB to 267 * place the TLS data on the proper alignment. 268 * Example: p_align=16 sizeof(TIB)=52 align(TIB)=4 269 * - need to offset the TIB 12 bytes from the start 270 * - to place ths TLS data at offset 64 271 */ 272 _static_tls_size = phdr[i].p_memsz; 273 _static_tls_align_offset = 274 ELF_ROUND(sizeof(struct tib), _static_tls_align) - 275 sizeof(struct tib); 276 #elif TLS_VARIANT == 2 277 /* 278 * Variant 2 places the data before the TIB 279 * so we need to round up the size to the 280 * TLS data alignment TIB's alignment. 281 * Example A: p_memsz=24 p_align=16 align(TIB)=8 282 * - need to allocate 32 bytes for TLS as compiler 283 * - will give the first TLS symbol an offset of -32 284 * Example B: p_memsz=4 p_align=4 align(TIB)=8 285 * - need to allocate 8 bytes so that the TIB is 286 * - properly aligned 287 */ 288 _static_tls_size = ELF_ROUND(phdr[i].p_memsz, 289 phdr[i].p_align); 290 _static_tls_align_offset = ELF_ROUND(_static_tls_size, 291 _static_tls_align) - _static_tls_size; 292 #endif 293 if (phdr[i].p_vaddr != 0 && phdr[i].p_filesz != 0) { 294 static_tls = (void *)phdr[i].p_vaddr + 295 _static_phdr_info.dlpi_addr; 296 static_tls_fsize = phdr[i].p_filesz; 297 } 298 break; 299 } 300 } 301 302 base = mmap(NULL, _static_tls_size + _static_tls_align_offset 303 + sizeof *tib, PROT_READ|PROT_WRITE, MAP_ANON|MAP_PRIVATE, -1, 0); 304 305 tib = _static_tls_init(base, NULL); 306 tib->tib_tid = getthrid(); 307 TCB_SET(TIB_TO_TCB(tib)); 308 #if ! TCB_HAVE_MD_GET 309 _libc_single_tcb = TIB_TO_TCB(tib); 310 #endif 311 } 312 313 struct tib * 314 _static_tls_init(char *base, void *thread) 315 { 316 struct tib *tib; 317 318 base += _static_tls_align_offset; 319 # if TLS_VARIANT == 1 320 tib = (struct tib *)base; 321 base += sizeof(struct tib); 322 # elif TLS_VARIANT == 2 323 tib = (struct tib *)(base + _static_tls_size); 324 # endif 325 326 if (_static_tls_size) { 327 if (static_tls != NULL) 328 memcpy(base, static_tls, static_tls_fsize); 329 memset(base + static_tls_fsize, 0, 330 _static_tls_size - static_tls_fsize); 331 } 332 333 TIB_INIT(tib, NULL, thread); 334 return tib; 335 } 336 #endif /* !PIC */ 337