1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com) 4 */ 5 6 #include <stdio.h> 7 #include <stdlib.h> 8 #include <stdarg.h> 9 #include <unistd.h> 10 #include <errno.h> 11 #include <fcntl.h> 12 #include <sched.h> 13 #include <signal.h> 14 #include <string.h> 15 #include <sys/mman.h> 16 #include <sys/stat.h> 17 #include <sys/wait.h> 18 #include <sys/time.h> 19 #include <sys/resource.h> 20 #include <asm/unistd.h> 21 #include <init.h> 22 #include <os.h> 23 #include <mem_user.h> 24 #include <ptrace_user.h> 25 #include <registers.h> 26 #include <skas.h> 27 28 static void ptrace_child(void) 29 { 30 int ret; 31 /* Calling os_getpid because some libcs cached getpid incorrectly */ 32 int pid = os_getpid(), ppid = getppid(); 33 int sc_result; 34 35 if (change_sig(SIGWINCH, 0) < 0 || 36 ptrace(PTRACE_TRACEME, 0, 0, 0) < 0) { 37 perror("ptrace"); 38 kill(pid, SIGKILL); 39 } 40 kill(pid, SIGSTOP); 41 42 /* 43 * This syscall will be intercepted by the parent. Don't call more than 44 * once, please. 45 */ 46 sc_result = os_getpid(); 47 48 if (sc_result == pid) 49 /* Nothing modified by the parent, we are running normally. */ 50 ret = 1; 51 else if (sc_result == ppid) 52 /* 53 * Expected in check_ptrace and check_sysemu when they succeed 54 * in modifying the stack frame 55 */ 56 ret = 0; 57 else 58 /* Serious trouble! This could be caused by a bug in host 2.6 59 * SKAS3/2.6 patch before release -V6, together with a bug in 60 * the UML code itself. 61 */ 62 ret = 2; 63 64 exit(ret); 65 } 66 67 static void fatal_perror(const char *str) 68 { 69 perror(str); 70 exit(1); 71 } 72 73 static void fatal(char *fmt, ...) 74 { 75 va_list list; 76 77 va_start(list, fmt); 78 vfprintf(stderr, fmt, list); 79 va_end(list); 80 81 exit(1); 82 } 83 84 static void non_fatal(char *fmt, ...) 85 { 86 va_list list; 87 88 va_start(list, fmt); 89 vfprintf(stderr, fmt, list); 90 va_end(list); 91 } 92 93 static int start_ptraced_child(void) 94 { 95 int pid, n, status; 96 97 fflush(stdout); 98 99 pid = fork(); 100 if (pid == 0) 101 ptrace_child(); 102 else if (pid < 0) 103 fatal_perror("start_ptraced_child : fork failed"); 104 105 CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED)); 106 if (n < 0) 107 fatal_perror("check_ptrace : waitpid failed"); 108 if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP)) 109 fatal("check_ptrace : expected SIGSTOP, got status = %d", 110 status); 111 112 return pid; 113 } 114 115 /* When testing for SYSEMU support, if it is one of the broken versions, we 116 * must just avoid using sysemu, not panic, but only if SYSEMU features are 117 * broken. 118 * So only for SYSEMU features we test mustpanic, while normal host features 119 * must work anyway! 120 */ 121 static int stop_ptraced_child(int pid, int exitcode, int mustexit) 122 { 123 int status, n, ret = 0; 124 125 if (ptrace(PTRACE_CONT, pid, 0, 0) < 0) { 126 perror("stop_ptraced_child : ptrace failed"); 127 return -1; 128 } 129 CATCH_EINTR(n = waitpid(pid, &status, 0)); 130 if (!WIFEXITED(status) || (WEXITSTATUS(status) != exitcode)) { 131 int exit_with = WEXITSTATUS(status); 132 if (exit_with == 2) 133 non_fatal("check_ptrace : child exited with status 2. " 134 "\nDisabling SYSEMU support.\n"); 135 non_fatal("check_ptrace : child exited with exitcode %d, while " 136 "expecting %d; status 0x%x\n", exit_with, 137 exitcode, status); 138 if (mustexit) 139 exit(1); 140 ret = -1; 141 } 142 143 return ret; 144 } 145 146 /* Changed only during early boot */ 147 static int force_sysemu_disabled = 0; 148 149 static int __init nosysemu_cmd_param(char *str, int* add) 150 { 151 force_sysemu_disabled = 1; 152 return 0; 153 } 154 155 __uml_setup("nosysemu", nosysemu_cmd_param, 156 "nosysemu\n" 157 " Turns off syscall emulation patch for ptrace (SYSEMU).\n" 158 " SYSEMU is a performance-patch introduced by Laurent Vivier. It changes\n" 159 " behaviour of ptrace() and helps reduce host context switch rates.\n" 160 " To make it work, you need a kernel patch for your host, too.\n" 161 " See http://perso.wanadoo.fr/laurent.vivier/UML/ for further \n" 162 " information.\n\n"); 163 164 static void __init check_sysemu(void) 165 { 166 unsigned long regs[MAX_REG_NR]; 167 int pid, n, status, count=0; 168 169 os_info("Checking syscall emulation patch for ptrace..."); 170 sysemu_supported = 0; 171 pid = start_ptraced_child(); 172 173 if (ptrace(PTRACE_SYSEMU, pid, 0, 0) < 0) 174 goto fail; 175 176 CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED)); 177 if (n < 0) 178 fatal_perror("check_sysemu : wait failed"); 179 if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGTRAP)) 180 fatal("check_sysemu : expected SIGTRAP, got status = %d\n", 181 status); 182 183 if (ptrace(PTRACE_GETREGS, pid, 0, regs) < 0) 184 fatal_perror("check_sysemu : PTRACE_GETREGS failed"); 185 if (PT_SYSCALL_NR(regs) != __NR_getpid) { 186 non_fatal("check_sysemu got system call number %d, " 187 "expected %d...", PT_SYSCALL_NR(regs), __NR_getpid); 188 goto fail; 189 } 190 191 n = ptrace(PTRACE_POKEUSER, pid, PT_SYSCALL_RET_OFFSET, os_getpid()); 192 if (n < 0) { 193 non_fatal("check_sysemu : failed to modify system call " 194 "return"); 195 goto fail; 196 } 197 198 if (stop_ptraced_child(pid, 0, 0) < 0) 199 goto fail_stopped; 200 201 sysemu_supported = 1; 202 os_info("OK\n"); 203 set_using_sysemu(!force_sysemu_disabled); 204 205 os_info("Checking advanced syscall emulation patch for ptrace..."); 206 pid = start_ptraced_child(); 207 208 if ((ptrace(PTRACE_OLDSETOPTIONS, pid, 0, 209 (void *) PTRACE_O_TRACESYSGOOD) < 0)) 210 fatal_perror("check_sysemu: PTRACE_OLDSETOPTIONS failed"); 211 212 while (1) { 213 count++; 214 if (ptrace(PTRACE_SYSEMU_SINGLESTEP, pid, 0, 0) < 0) 215 goto fail; 216 CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED)); 217 if (n < 0) 218 fatal_perror("check_sysemu: wait failed"); 219 220 if (WIFSTOPPED(status) && 221 (WSTOPSIG(status) == (SIGTRAP|0x80))) { 222 if (!count) { 223 non_fatal("check_sysemu: SYSEMU_SINGLESTEP " 224 "doesn't singlestep"); 225 goto fail; 226 } 227 n = ptrace(PTRACE_POKEUSER, pid, PT_SYSCALL_RET_OFFSET, 228 os_getpid()); 229 if (n < 0) 230 fatal_perror("check_sysemu : failed to modify " 231 "system call return"); 232 break; 233 } 234 else if (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGTRAP)) 235 count++; 236 else { 237 non_fatal("check_sysemu: expected SIGTRAP or " 238 "(SIGTRAP | 0x80), got status = %d\n", 239 status); 240 goto fail; 241 } 242 } 243 if (stop_ptraced_child(pid, 0, 0) < 0) 244 goto fail_stopped; 245 246 sysemu_supported = 2; 247 os_info("OK\n"); 248 249 if (!force_sysemu_disabled) 250 set_using_sysemu(sysemu_supported); 251 return; 252 253 fail: 254 stop_ptraced_child(pid, 1, 0); 255 fail_stopped: 256 non_fatal("missing\n"); 257 } 258 259 static void __init check_ptrace(void) 260 { 261 int pid, syscall, n, status; 262 263 os_info("Checking that ptrace can change system call numbers..."); 264 pid = start_ptraced_child(); 265 266 if ((ptrace(PTRACE_OLDSETOPTIONS, pid, 0, 267 (void *) PTRACE_O_TRACESYSGOOD) < 0)) 268 fatal_perror("check_ptrace: PTRACE_OLDSETOPTIONS failed"); 269 270 while (1) { 271 if (ptrace(PTRACE_SYSCALL, pid, 0, 0) < 0) 272 fatal_perror("check_ptrace : ptrace failed"); 273 274 CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED)); 275 if (n < 0) 276 fatal_perror("check_ptrace : wait failed"); 277 278 if (!WIFSTOPPED(status) || 279 (WSTOPSIG(status) != (SIGTRAP | 0x80))) 280 fatal("check_ptrace : expected (SIGTRAP|0x80), " 281 "got status = %d", status); 282 283 syscall = ptrace(PTRACE_PEEKUSER, pid, PT_SYSCALL_NR_OFFSET, 284 0); 285 if (syscall == __NR_getpid) { 286 n = ptrace(PTRACE_POKEUSER, pid, PT_SYSCALL_NR_OFFSET, 287 __NR_getppid); 288 if (n < 0) 289 fatal_perror("check_ptrace : failed to modify " 290 "system call"); 291 break; 292 } 293 } 294 stop_ptraced_child(pid, 0, 1); 295 os_info("OK\n"); 296 check_sysemu(); 297 } 298 299 extern void check_tmpexec(void); 300 301 static void __init check_coredump_limit(void) 302 { 303 struct rlimit lim; 304 int err = getrlimit(RLIMIT_CORE, &lim); 305 306 if (err) { 307 perror("Getting core dump limit"); 308 return; 309 } 310 311 os_info("Core dump limits :\n\tsoft - "); 312 if (lim.rlim_cur == RLIM_INFINITY) 313 os_info("NONE\n"); 314 else 315 os_info("%llu\n", (unsigned long long)lim.rlim_cur); 316 317 os_info("\thard - "); 318 if (lim.rlim_max == RLIM_INFINITY) 319 os_info("NONE\n"); 320 else 321 os_info("%llu\n", (unsigned long long)lim.rlim_max); 322 } 323 324 void __init os_early_checks(void) 325 { 326 int pid; 327 328 /* Print out the core dump limits early */ 329 check_coredump_limit(); 330 331 check_ptrace(); 332 333 /* Need to check this early because mmapping happens before the 334 * kernel is running. 335 */ 336 check_tmpexec(); 337 338 pid = start_ptraced_child(); 339 if (init_registers(pid)) 340 fatal("Failed to initialize default registers"); 341 stop_ptraced_child(pid, 1, 1); 342 } 343 344 int __init parse_iomem(char *str, int *add) 345 { 346 struct iomem_region *new; 347 struct stat64 buf; 348 char *file, *driver; 349 int fd, size; 350 351 driver = str; 352 file = strchr(str,','); 353 if (file == NULL) { 354 os_warn("parse_iomem : failed to parse iomem\n"); 355 goto out; 356 } 357 *file = '\0'; 358 file++; 359 fd = open(file, O_RDWR, 0); 360 if (fd < 0) { 361 perror("parse_iomem - Couldn't open io file"); 362 goto out; 363 } 364 365 if (fstat64(fd, &buf) < 0) { 366 perror("parse_iomem - cannot stat_fd file"); 367 goto out_close; 368 } 369 370 new = malloc(sizeof(*new)); 371 if (new == NULL) { 372 perror("Couldn't allocate iomem_region struct"); 373 goto out_close; 374 } 375 376 size = (buf.st_size + UM_KERN_PAGE_SIZE) & ~(UM_KERN_PAGE_SIZE - 1); 377 378 *new = ((struct iomem_region) { .next = iomem_regions, 379 .driver = driver, 380 .fd = fd, 381 .size = size, 382 .phys = 0, 383 .virt = 0 }); 384 iomem_regions = new; 385 iomem_size += new->size + UM_KERN_PAGE_SIZE; 386 387 return 0; 388 out_close: 389 close(fd); 390 out: 391 return 1; 392 } 393