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 2008 Sun Microsystems, Inc. All rights reserved. 24 * Use is subject to license terms. 25 */ 26 27 #pragma ident "%Z%%M% %I% %E% SMI" 28 29 /* 30 * Redirection ld.so. Based on the 4.x binary compatibility ld.so, used 31 * to redirect aliases for ld.so to the real one. 32 */ 33 34 /* 35 * Import data structures 36 */ 37 #include "lint.h" 38 #include <sys/types.h> 39 #include <sys/mman.h> 40 #include <sys/fcntl.h> 41 #include <sys/stat.h> 42 #include <sys/sysconfig.h> 43 #include <sys/auxv.h> 44 #include <elf.h> 45 #include <link.h> 46 #include <string.h> 47 #include "alias_boot.h" 48 49 /* 50 * Local manifest constants and macros. 51 */ 52 #define ALIGN(x, a) ((uintptr_t)(x) & ~((a) - 1)) 53 #define ROUND(x, a) (((uintptr_t)(x) + ((a) - 1)) & ~((a) - 1)) 54 55 #define EMPTY strings[EMPTY_S] 56 #define LDSO strings[LDSO_S] 57 #define ZERO strings[ZERO_S] 58 #define CLOSE (*(funcs[CLOSE_F])) 59 #define FSTAT (*(funcs[FSTAT_F])) 60 #define MMAP (*(funcs[MMAP_F])) 61 #define MUNMAP (*(funcs[MUNMAP_F])) 62 #define OPEN (*(funcs[OPEN_F])) 63 #define PANIC (*(funcs[PANIC_F])) 64 #define SYSCONFIG (*(funcs[SYSCONFIG_F])) 65 66 /* 67 * Alias ld.so entry point -- receives a bootstrap structure and a vector 68 * of strings. The vector is "well-known" to us, and consists of pointers 69 * to string constants. This aliasing bootstrap requires no relocation in 70 * order to run, save for the pointers of constant strings. This second 71 * parameter provides this. Note that this program is carefully coded in 72 * order to maintain the "no bootstrapping" requirement -- it calls only 73 * local functions, uses no intrinsics, etc. 74 */ 75 static void * 76 __rtld(Elf32_Boot *ebp, const char *strings[], int (*funcs[])()) 77 { 78 int i, p; /* working */ 79 long j; /* working */ 80 long page_size = 0; /* size of a page */ 81 const char *program_name = EMPTY; /* our name */ 82 int ldfd; /* fd assigned to ld.so */ 83 int dzfd = 0; /* fd assigned to /dev/zero */ 84 Elf32_Ehdr *ehdr; /* ELF header of ld.so */ 85 Elf32_Phdr *phdr; /* first Phdr in file */ 86 Elf32_Phdr *pptr; /* working Phdr */ 87 Elf32_Phdr *lph = NULL; /* last loadable Phdr */ 88 Elf32_Phdr *fph = NULL; /* first loadable Phdr */ 89 caddr_t maddr; /* pointer to mapping claim */ 90 Elf32_Off mlen; /* total mapping claim */ 91 caddr_t faddr; /* first program mapping of ld.so */ 92 Elf32_Off foff; /* file offset for segment mapping */ 93 Elf32_Off flen; /* file length for segment mapping */ 94 caddr_t addr; /* working mapping address */ 95 caddr_t zaddr; /* /dev/zero working mapping addr */ 96 struct stat sb; /* stat buffer for sizing */ 97 auxv_t *ap; /* working aux pointer */ 98 99 /* 100 * Discover things about our environment: auxiliary vector (if 101 * any), arguments, program name, and the like. 102 */ 103 while (ebp->eb_tag != NULL) { 104 switch (ebp->eb_tag) { 105 case EB_ARGV: 106 program_name = *((char **)ebp->eb_un.eb_ptr); 107 break; 108 case EB_AUXV: 109 for (ap = (auxv_t *)ebp->eb_un.eb_ptr; 110 ap->a_type != AT_NULL; ap++) 111 if (ap->a_type == AT_PAGESZ) { 112 page_size = ap->a_un.a_val; 113 break; 114 } 115 break; 116 } 117 ebp++; 118 } 119 120 /* 121 * If we didn't get a page size from looking in the auxiliary 122 * vector, we need to get one now. 123 */ 124 if (page_size == 0) { 125 page_size = SYSCONFIG(_CONFIG_PAGESIZE); 126 ebp->eb_tag = EB_PAGESIZE, (ebp++)->eb_un.eb_val = 127 (Elf32_Word)page_size; 128 } 129 130 /* 131 * Map in the real ld.so. Note that we're mapping it as 132 * an ELF database, not as a program -- we just want to walk it's 133 * data structures. Further mappings will actually establish the 134 * program in the address space. 135 */ 136 if ((ldfd = OPEN(LDSO, O_RDONLY)) == -1) 137 PANIC(program_name); 138 if (FSTAT(ldfd, &sb) == -1) 139 PANIC(program_name); 140 ehdr = (Elf32_Ehdr *)MMAP(0, sb.st_size, PROT_READ | PROT_EXEC, 141 MAP_SHARED, ldfd, 0); 142 if (ehdr == (Elf32_Ehdr *)-1) 143 PANIC(program_name); 144 145 /* 146 * Validate the file we're looking at, ensure it has the correct 147 * ELF structures, such as: ELF magic numbers, coded for SPARC, 148 * is a ".so", etc. 149 */ 150 if (ehdr->e_ident[EI_MAG0] != ELFMAG0 || 151 ehdr->e_ident[EI_MAG1] != ELFMAG1 || 152 ehdr->e_ident[EI_MAG2] != ELFMAG2 || 153 ehdr->e_ident[EI_MAG3] != ELFMAG3) 154 PANIC(program_name); 155 if (ehdr->e_ident[EI_CLASS] != ELFCLASS32 || 156 ehdr->e_ident[EI_DATA] != ELFDATA2MSB) 157 PANIC(program_name); 158 if (ehdr->e_type != ET_DYN) 159 PANIC(program_name); 160 if ((ehdr->e_machine != EM_SPARC) && 161 (ehdr->e_machine != EM_SPARC32PLUS)) 162 PANIC(program_name); 163 if (ehdr->e_version > EV_CURRENT) 164 PANIC(program_name); 165 166 /* 167 * Point at program headers and start figuring out what to load. 168 */ 169 phdr = (Elf32_Phdr *)((caddr_t)ehdr + ehdr->e_phoff); 170 for (p = 0, pptr = phdr; p < (int)ehdr->e_phnum; p++, 171 pptr = (Elf32_Phdr *)((caddr_t)pptr + ehdr->e_phentsize)) 172 if (pptr->p_type == PT_LOAD) { 173 if (fph == 0) { 174 fph = pptr; 175 } else if (pptr->p_vaddr <= lph->p_vaddr) 176 PANIC(program_name); 177 lph = pptr; 178 } 179 180 /* 181 * We'd better have at least one loadable segment. 182 */ 183 if (fph == 0) 184 PANIC(program_name); 185 186 /* 187 * Map enough address space to hold the program (as opposed to the 188 * file) represented by ld.so. The amount to be assigned is the 189 * range between the end of the last loadable segment and the 190 * beginning of the first PLUS the alignment of the first segment. 191 * mmap() can assign us any page-aligned address, but the relocations 192 * assume the alignments included in the program header. As an 193 * optimization, however, let's assume that mmap() will actually 194 * give us an aligned address -- since if it does, we can save 195 * an munmap() later on. If it doesn't -- then go try it again. 196 */ 197 mlen = ROUND((lph->p_vaddr + lph->p_memsz) - 198 ALIGN(fph->p_vaddr, page_size), page_size); 199 maddr = (caddr_t)MMAP(0, mlen, PROT_READ | PROT_EXEC, 200 MAP_SHARED, ldfd, 0); 201 if (maddr == (caddr_t)-1) 202 PANIC(program_name); 203 faddr = (caddr_t)ROUND(maddr, fph->p_align); 204 205 /* 206 * Check to see whether alignment skew was really needed. 207 */ 208 if (faddr != maddr) { 209 (void) MUNMAP(maddr, mlen); 210 mlen = ROUND((lph->p_vaddr + lph->p_memsz) - 211 ALIGN(fph->p_vaddr, fph->p_align) + fph->p_align, 212 page_size); 213 maddr = (caddr_t)MMAP(0, mlen, PROT_READ | PROT_EXEC, 214 MAP_SHARED, ldfd, 0); 215 if (maddr == (caddr_t)-1) 216 PANIC(program_name); 217 faddr = (caddr_t)ROUND(maddr, fph->p_align); 218 } 219 220 /* 221 * We have the address space reserved, so map each loadable segment. 222 */ 223 for (p = 0, pptr = phdr; p < (int)ehdr->e_phnum; p++, 224 pptr = (Elf32_Phdr *)((caddr_t)pptr + ehdr->e_phentsize)) { 225 226 /* 227 * Skip non-loadable segments or segments that don't occupy 228 * any memory. 229 */ 230 if ((pptr->p_type != PT_LOAD) || (pptr->p_memsz == 0)) 231 continue; 232 233 /* 234 * Determine the file offset to which the mapping will 235 * directed (must be aligned) and how much to map (might 236 * be more than the file in the case of .bss.) 237 */ 238 foff = ALIGN(pptr->p_offset, page_size); 239 flen = pptr->p_memsz + (pptr->p_offset - foff); 240 241 /* 242 * Set address of this segment relative to our base. 243 */ 244 addr = (caddr_t)ALIGN(faddr + pptr->p_vaddr, page_size); 245 246 /* 247 * If this is the first program header, record our base 248 * address for later use. 249 */ 250 if (pptr == phdr) { 251 ebp->eb_tag = EB_LDSO_BASE; 252 (ebp++)->eb_un.eb_ptr = (Elf32_Addr)addr; 253 } 254 255 /* 256 * Unmap anything from the last mapping address to this 257 * one. 258 */ 259 if (addr - maddr) { 260 (void) MUNMAP(maddr, addr - maddr); 261 mlen -= addr - maddr; 262 } 263 264 /* 265 * Determine the mapping protection from the section 266 * attributes. 267 */ 268 i = 0; 269 if (pptr->p_flags & PF_R) 270 i |= PROT_READ; 271 if (pptr->p_flags & PF_W) 272 i |= PROT_WRITE; 273 if (pptr->p_flags & PF_X) 274 i |= PROT_EXEC; 275 if ((caddr_t)MMAP((caddr_t)addr, flen, i, 276 MAP_FIXED | MAP_PRIVATE, ldfd, foff) == (caddr_t)-1) 277 PANIC(program_name); 278 279 /* 280 * If the memory occupancy of the segment overflows the 281 * definition in the file, we need to "zero out" the 282 * end of the mapping we've established, and if necessary, 283 * map some more space from /dev/zero. 284 */ 285 if (pptr->p_memsz > pptr->p_filesz) { 286 foff = (uintptr_t)faddr + pptr->p_vaddr + 287 pptr->p_filesz; 288 zaddr = (caddr_t)ROUND(foff, page_size); 289 for (j = 0; j < (int)(zaddr - foff); j++) 290 *((char *)foff + j) = 0; 291 j = (faddr + pptr->p_vaddr + pptr->p_memsz) - zaddr; 292 if (j > 0) { 293 if (dzfd == 0) { 294 dzfd = OPEN(ZERO, O_RDWR); 295 if (dzfd == -1) 296 PANIC(program_name); 297 } 298 if ((caddr_t)MMAP((caddr_t)zaddr, j, i, 299 MAP_FIXED | MAP_PRIVATE, dzfd, 300 0) == (caddr_t)-1) 301 PANIC(program_name); 302 } 303 } 304 305 /* 306 * Update the mapping claim pointer. 307 */ 308 maddr = addr + ROUND(flen, page_size); 309 mlen -= maddr - addr; 310 } 311 312 /* 313 * Unmap any final reservation. 314 */ 315 if (mlen != 0) 316 (void) MUNMAP(maddr, mlen); 317 318 /* 319 * Clean up file descriptor space we've consumed. Pass along 320 * the /dev/zero file descriptor we got -- every cycle counts. 321 */ 322 (void) CLOSE(ldfd); 323 if (dzfd != 0) 324 ebp->eb_tag = EB_DEVZERO, (ebp++)->eb_un.eb_val = dzfd; 325 326 /* 327 * The call itself. Note that we start 1 instruction word in. 328 * The ELF ld.so contains an "entry vector" of branch instructions, 329 * which, for our interest are: 330 * +0: ba, a <normal startup> 331 * +4: ba, a <compatibility startup> 332 * +8: ba, a <alias startup> 333 * By starting at the alias startup, the ELF ld.so knows 334 * that a pointer to "eb" is available to it and further knows 335 * how to calculate the offset to the program's arguments and 336 * other structures. We do the "call" by returning to our 337 * bootstrap and then jumping to the address that we return. 338 */ 339 ebp->eb_tag = EB_NULL, ebp->eb_un.eb_val = 0; 340 return ((void *)(ehdr->e_entry + faddr + 8)); 341 } 342