1 /* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 5 * Common Development and Distribution License (the "License"). 6 * You may not use this file except in compliance with the License. 7 * 8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 9 * or http://www.opensolaris.org/os/licensing. 10 * See the License for the specific language governing permissions 11 * and limitations under the License. 12 * 13 * When distributing Covered Code, include this CDDL HEADER in each 14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 15 * If applicable, add the following below this CDDL HEADER, with the 16 * fields enclosed by brackets "[]" replaced with your own identifying 17 * information: Portions Copyright [yyyy] [name of copyright owner] 18 * 19 * CDDL HEADER END 20 */ 21 22 /* 23 * Copyright 2010 Sun Microsystems, Inc. All rights reserved. 24 * Use is subject to license terms. 25 */ 26 27 /* 28 * Redirection ld.so. Based on the 4.x binary compatibility ld.so, used 29 * to redirect aliases for ld.so to the real one. 30 */ 31 32 /* 33 * Import data structures 34 */ 35 #include "lint.h" 36 #include <sys/types.h> 37 #include <sys/mman.h> 38 #include <sys/fcntl.h> 39 #include <sys/stat.h> 40 #include <sys/sysconfig.h> 41 #include <sys/auxv.h> 42 #include <elf.h> 43 #include <link.h> 44 #include <string.h> 45 #include "alias_boot.h" 46 47 /* 48 * Local manifest constants and macros. 49 */ 50 #define ALIGN(x, a) ((uintptr_t)(x) & ~((a) - 1)) 51 #define ROUND(x, a) (((uintptr_t)(x) + ((a) - 1)) & ~((a) - 1)) 52 53 #define EMPTY strings[EMPTY_S] 54 #define LDSO strings[LDSO_S] 55 #define ZERO strings[ZERO_S] 56 #define CLOSE (*(funcs[CLOSE_F])) 57 #define FSTATAT (*(funcs[FSTATAT_F])) 58 #define MMAP (*(funcs[MMAP_F])) 59 #define MUNMAP (*(funcs[MUNMAP_F])) 60 #define OPENAT (*(funcs[OPENAT_F])) 61 #define PANIC (*(funcs[PANIC_F])) 62 #define SYSCONFIG (*(funcs[SYSCONFIG_F])) 63 64 /* 65 * Alias ld.so entry point -- receives a bootstrap structure and a vector 66 * of strings. The vector is "well-known" to us, and consists of pointers 67 * to string constants. This aliasing bootstrap requires no relocation in 68 * order to run, save for the pointers of constant strings. This second 69 * parameter provides this. Note that this program is carefully coded in 70 * order to maintain the "no bootstrapping" requirement -- it calls only 71 * local functions, uses no intrinsics, etc. 72 */ 73 void * 74 __rtld(Elf32_Boot *ebp, const char *strings[], int (*funcs[])()) 75 { 76 int i, p; /* working */ 77 long j; /* working */ 78 long page_size = 0; /* size of a page */ 79 const char *program_name = EMPTY; /* our name */ 80 int ldfd; /* fd assigned to ld.so */ 81 int dzfd = 0; /* fd assigned to /dev/zero */ 82 Elf32_Ehdr *ehdr; /* ELF header of ld.so */ 83 Elf32_Phdr *phdr; /* first Phdr in file */ 84 Elf32_Phdr *pptr; /* working Phdr */ 85 Elf32_Phdr *lph = NULL; /* last loadable Phdr */ 86 Elf32_Phdr *fph = NULL; /* first loadable Phdr */ 87 caddr_t maddr; /* pointer to mapping claim */ 88 Elf32_Off mlen; /* total mapping claim */ 89 caddr_t faddr; /* first program mapping of ld.so */ 90 Elf32_Off foff; /* file offset for segment mapping */ 91 Elf32_Off flen; /* file length for segment mapping */ 92 caddr_t addr; /* working mapping address */ 93 caddr_t zaddr; /* /dev/zero working mapping addr */ 94 struct stat sb; /* stat buffer for sizing */ 95 auxv_t *ap; /* working aux pointer */ 96 97 /* 98 * Discover things about our environment: auxiliary vector (if 99 * any), arguments, program name, and the like. 100 */ 101 while (ebp->eb_tag != 0) { 102 switch (ebp->eb_tag) { 103 case EB_ARGV: 104 program_name = *((char **)ebp->eb_un.eb_ptr); 105 break; 106 case EB_AUXV: 107 for (ap = (auxv_t *)ebp->eb_un.eb_ptr; 108 ap->a_type != AT_NULL; ap++) 109 if (ap->a_type == AT_PAGESZ) { 110 page_size = ap->a_un.a_val; 111 break; 112 } 113 break; 114 } 115 ebp++; 116 } 117 118 /* 119 * If we didn't get a page size from looking in the auxiliary 120 * vector, we need to get one now. 121 */ 122 if (page_size == 0) { 123 page_size = SYSCONFIG(_CONFIG_PAGESIZE); 124 ebp->eb_tag = EB_PAGESIZE, (ebp++)->eb_un.eb_val = 125 (Elf32_Word)page_size; 126 } 127 128 /* 129 * Map in the real ld.so. Note that we're mapping it as 130 * an ELF database, not as a program -- we just want to walk it's 131 * data structures. Further mappings will actually establish the 132 * program in the address space. 133 */ 134 if ((ldfd = OPENAT(AT_FDCWD, LDSO, O_RDONLY)) == -1) 135 PANIC(program_name); 136 if (FSTATAT(ldfd, NULL, &sb, 0) == -1) 137 PANIC(program_name); 138 ehdr = (Elf32_Ehdr *)MMAP(0, sb.st_size, PROT_READ | PROT_EXEC, 139 MAP_SHARED, ldfd, 0); 140 if (ehdr == (Elf32_Ehdr *)-1) 141 PANIC(program_name); 142 143 /* 144 * Validate the file we're looking at, ensure it has the correct 145 * ELF structures, such as: ELF magic numbers, coded for SPARC, 146 * is a ".so", etc. 147 */ 148 if (ehdr->e_ident[EI_MAG0] != ELFMAG0 || 149 ehdr->e_ident[EI_MAG1] != ELFMAG1 || 150 ehdr->e_ident[EI_MAG2] != ELFMAG2 || 151 ehdr->e_ident[EI_MAG3] != ELFMAG3) 152 PANIC(program_name); 153 if (ehdr->e_ident[EI_CLASS] != ELFCLASS32 || 154 ehdr->e_ident[EI_DATA] != ELFDATA2MSB) 155 PANIC(program_name); 156 if (ehdr->e_type != ET_DYN) 157 PANIC(program_name); 158 if ((ehdr->e_machine != EM_SPARC) && 159 (ehdr->e_machine != EM_SPARC32PLUS)) 160 PANIC(program_name); 161 if (ehdr->e_version > EV_CURRENT) 162 PANIC(program_name); 163 164 /* 165 * Point at program headers and start figuring out what to load. 166 */ 167 phdr = (Elf32_Phdr *)((caddr_t)ehdr + ehdr->e_phoff); 168 for (p = 0, pptr = phdr; p < (int)ehdr->e_phnum; p++, 169 pptr = (Elf32_Phdr *)((caddr_t)pptr + ehdr->e_phentsize)) 170 if (pptr->p_type == PT_LOAD) { 171 if (fph == 0) { 172 fph = pptr; 173 } else if (pptr->p_vaddr <= lph->p_vaddr) 174 PANIC(program_name); 175 lph = pptr; 176 } 177 178 /* 179 * We'd better have at least one loadable segment. 180 */ 181 if (fph == 0) 182 PANIC(program_name); 183 184 /* 185 * Map enough address space to hold the program (as opposed to the 186 * file) represented by ld.so. The amount to be assigned is the 187 * range between the end of the last loadable segment and the 188 * beginning of the first PLUS the alignment of the first segment. 189 * mmap() can assign us any page-aligned address, but the relocations 190 * assume the alignments included in the program header. As an 191 * optimization, however, let's assume that mmap() will actually 192 * give us an aligned address -- since if it does, we can save 193 * an munmap() later on. If it doesn't -- then go try it again. 194 */ 195 mlen = ROUND((lph->p_vaddr + lph->p_memsz) - 196 ALIGN(fph->p_vaddr, page_size), page_size); 197 maddr = (caddr_t)MMAP(0, mlen, PROT_READ | PROT_EXEC, 198 MAP_SHARED, ldfd, 0); 199 if (maddr == (caddr_t)-1) 200 PANIC(program_name); 201 faddr = (caddr_t)ROUND(maddr, fph->p_align); 202 203 /* 204 * Check to see whether alignment skew was really needed. 205 */ 206 if (faddr != maddr) { 207 (void) MUNMAP(maddr, mlen); 208 mlen = ROUND((lph->p_vaddr + lph->p_memsz) - 209 ALIGN(fph->p_vaddr, fph->p_align) + fph->p_align, 210 page_size); 211 maddr = (caddr_t)MMAP(0, mlen, PROT_READ | PROT_EXEC, 212 MAP_SHARED, ldfd, 0); 213 if (maddr == (caddr_t)-1) 214 PANIC(program_name); 215 faddr = (caddr_t)ROUND(maddr, fph->p_align); 216 } 217 218 /* 219 * We have the address space reserved, so map each loadable segment. 220 */ 221 for (p = 0, pptr = phdr; p < (int)ehdr->e_phnum; p++, 222 pptr = (Elf32_Phdr *)((caddr_t)pptr + ehdr->e_phentsize)) { 223 224 /* 225 * Skip non-loadable segments or segments that don't occupy 226 * any memory. 227 */ 228 if ((pptr->p_type != PT_LOAD) || (pptr->p_memsz == 0)) 229 continue; 230 231 /* 232 * Determine the file offset to which the mapping will 233 * directed (must be aligned) and how much to map (might 234 * be more than the file in the case of .bss.) 235 */ 236 foff = ALIGN(pptr->p_offset, page_size); 237 flen = pptr->p_memsz + (pptr->p_offset - foff); 238 239 /* 240 * Set address of this segment relative to our base. 241 */ 242 addr = (caddr_t)ALIGN(faddr + pptr->p_vaddr, page_size); 243 244 /* 245 * If this is the first program header, record our base 246 * address for later use. 247 */ 248 if (pptr == phdr) { 249 ebp->eb_tag = EB_LDSO_BASE; 250 (ebp++)->eb_un.eb_ptr = (Elf32_Addr)addr; 251 } 252 253 /* 254 * Unmap anything from the last mapping address to this 255 * one. 256 */ 257 if (addr - maddr) { 258 (void) MUNMAP(maddr, addr - maddr); 259 mlen -= addr - maddr; 260 } 261 262 /* 263 * Determine the mapping protection from the section 264 * attributes. 265 */ 266 i = 0; 267 if (pptr->p_flags & PF_R) 268 i |= PROT_READ; 269 if (pptr->p_flags & PF_W) 270 i |= PROT_WRITE; 271 if (pptr->p_flags & PF_X) 272 i |= PROT_EXEC; 273 if ((caddr_t)MMAP((caddr_t)addr, flen, i, 274 MAP_FIXED | MAP_PRIVATE, ldfd, foff) == (caddr_t)-1) 275 PANIC(program_name); 276 277 /* 278 * If the memory occupancy of the segment overflows the 279 * definition in the file, we need to "zero out" the 280 * end of the mapping we've established, and if necessary, 281 * map some more space from /dev/zero. 282 */ 283 if (pptr->p_memsz > pptr->p_filesz) { 284 foff = (uintptr_t)faddr + pptr->p_vaddr + 285 pptr->p_filesz; 286 zaddr = (caddr_t)ROUND(foff, page_size); 287 for (j = 0; j < (int)(zaddr - foff); j++) 288 *((char *)foff + j) = 0; 289 j = (faddr + pptr->p_vaddr + pptr->p_memsz) - zaddr; 290 if (j > 0) { 291 if (dzfd == 0) { 292 dzfd = OPENAT(AT_FDCWD, ZERO, O_RDWR); 293 if (dzfd == -1) 294 PANIC(program_name); 295 } 296 if ((caddr_t)MMAP((caddr_t)zaddr, j, i, 297 MAP_FIXED | MAP_PRIVATE, dzfd, 298 0) == (caddr_t)-1) 299 PANIC(program_name); 300 } 301 } 302 303 /* 304 * Update the mapping claim pointer. 305 */ 306 maddr = addr + ROUND(flen, page_size); 307 mlen -= maddr - addr; 308 } 309 310 /* 311 * Unmap any final reservation. 312 */ 313 if (mlen != 0) 314 (void) MUNMAP(maddr, mlen); 315 316 /* 317 * Clean up file descriptor space we've consumed. Pass along 318 * the /dev/zero file descriptor we got -- every cycle counts. 319 */ 320 (void) CLOSE(ldfd); 321 if (dzfd != 0) 322 ebp->eb_tag = EB_DEVZERO, (ebp++)->eb_un.eb_val = dzfd; 323 324 /* 325 * The call itself. Note that we start 1 instruction word in. 326 * The ELF ld.so contains an "entry vector" of branch instructions, 327 * which, for our interest are: 328 * +0: ba, a <normal startup> 329 * +4: ba, a <compatibility startup> 330 * +8: ba, a <alias startup> 331 * By starting at the alias startup, the ELF ld.so knows 332 * that a pointer to "eb" is available to it and further knows 333 * how to calculate the offset to the program's arguments and 334 * other structures. We do the "call" by returning to our 335 * bootstrap and then jumping to the address that we return. 336 */ 337 ebp->eb_tag = EB_NULL, ebp->eb_un.eb_val = 0; 338 return ((void *)(ehdr->e_entry + faddr + 8)); 339 } 340