1 /* 2 * Copyright (C) 2005 Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it> 3 * Licensed under the GPL 4 */ 5 6 #include <linux/percpu.h> 7 #include <linux/sched.h> 8 #include <linux/syscalls.h> 9 #include <linux/uaccess.h> 10 #include <asm/ptrace-abi.h> 11 #include <os.h> 12 #include <skas.h> 13 #include <sysdep/tls.h> 14 15 /* 16 * If needed we can detect when it's uninitialized. 17 * 18 * These are initialized in an initcall and unchanged thereafter. 19 */ 20 static int host_supports_tls = -1; 21 int host_gdt_entry_tls_min; 22 23 int do_set_thread_area(struct user_desc *info) 24 { 25 int ret; 26 u32 cpu; 27 28 cpu = get_cpu(); 29 ret = os_set_thread_area(info, userspace_pid[cpu]); 30 put_cpu(); 31 32 if (ret) 33 printk(KERN_ERR "PTRACE_SET_THREAD_AREA failed, err = %d, " 34 "index = %d\n", ret, info->entry_number); 35 36 return ret; 37 } 38 39 int do_get_thread_area(struct user_desc *info) 40 { 41 int ret; 42 u32 cpu; 43 44 cpu = get_cpu(); 45 ret = os_get_thread_area(info, userspace_pid[cpu]); 46 put_cpu(); 47 48 if (ret) 49 printk(KERN_ERR "PTRACE_GET_THREAD_AREA failed, err = %d, " 50 "index = %d\n", ret, info->entry_number); 51 52 return ret; 53 } 54 55 /* 56 * sys_get_thread_area: get a yet unused TLS descriptor index. 57 * XXX: Consider leaving one free slot for glibc usage at first place. This must 58 * be done here (and by changing GDT_ENTRY_TLS_* macros) and nowhere else. 59 * 60 * Also, this must be tested when compiling in SKAS mode with dynamic linking 61 * and running against NPTL. 62 */ 63 static int get_free_idx(struct task_struct* task) 64 { 65 struct thread_struct *t = &task->thread; 66 int idx; 67 68 for (idx = 0; idx < GDT_ENTRY_TLS_ENTRIES; idx++) 69 if (!t->arch.tls_array[idx].present) 70 return idx + GDT_ENTRY_TLS_MIN; 71 return -ESRCH; 72 } 73 74 static inline void clear_user_desc(struct user_desc* info) 75 { 76 /* Postcondition: LDT_empty(info) returns true. */ 77 memset(info, 0, sizeof(*info)); 78 79 /* 80 * Check the LDT_empty or the i386 sys_get_thread_area code - we obtain 81 * indeed an empty user_desc. 82 */ 83 info->read_exec_only = 1; 84 info->seg_not_present = 1; 85 } 86 87 #define O_FORCE 1 88 89 static int load_TLS(int flags, struct task_struct *to) 90 { 91 int ret = 0; 92 int idx; 93 94 for (idx = GDT_ENTRY_TLS_MIN; idx < GDT_ENTRY_TLS_MAX; idx++) { 95 struct uml_tls_struct* curr = 96 &to->thread.arch.tls_array[idx - GDT_ENTRY_TLS_MIN]; 97 98 /* 99 * Actually, now if it wasn't flushed it gets cleared and 100 * flushed to the host, which will clear it. 101 */ 102 if (!curr->present) { 103 if (!curr->flushed) { 104 clear_user_desc(&curr->tls); 105 curr->tls.entry_number = idx; 106 } else { 107 WARN_ON(!LDT_empty(&curr->tls)); 108 continue; 109 } 110 } 111 112 if (!(flags & O_FORCE) && curr->flushed) 113 continue; 114 115 ret = do_set_thread_area(&curr->tls); 116 if (ret) 117 goto out; 118 119 curr->flushed = 1; 120 } 121 out: 122 return ret; 123 } 124 125 /* 126 * Verify if we need to do a flush for the new process, i.e. if there are any 127 * present desc's, only if they haven't been flushed. 128 */ 129 static inline int needs_TLS_update(struct task_struct *task) 130 { 131 int i; 132 int ret = 0; 133 134 for (i = GDT_ENTRY_TLS_MIN; i < GDT_ENTRY_TLS_MAX; i++) { 135 struct uml_tls_struct* curr = 136 &task->thread.arch.tls_array[i - GDT_ENTRY_TLS_MIN]; 137 138 /* 139 * Can't test curr->present, we may need to clear a descriptor 140 * which had a value. 141 */ 142 if (curr->flushed) 143 continue; 144 ret = 1; 145 break; 146 } 147 return ret; 148 } 149 150 /* 151 * On a newly forked process, the TLS descriptors haven't yet been flushed. So 152 * we mark them as such and the first switch_to will do the job. 153 */ 154 void clear_flushed_tls(struct task_struct *task) 155 { 156 int i; 157 158 for (i = GDT_ENTRY_TLS_MIN; i < GDT_ENTRY_TLS_MAX; i++) { 159 struct uml_tls_struct* curr = 160 &task->thread.arch.tls_array[i - GDT_ENTRY_TLS_MIN]; 161 162 /* 163 * Still correct to do this, if it wasn't present on the host it 164 * will remain as flushed as it was. 165 */ 166 if (!curr->present) 167 continue; 168 169 curr->flushed = 0; 170 } 171 } 172 173 /* 174 * In SKAS0 mode, currently, multiple guest threads sharing the same ->mm have a 175 * common host process. So this is needed in SKAS0 too. 176 * 177 * However, if each thread had a different host process (and this was discussed 178 * for SMP support) this won't be needed. 179 * 180 * And this will not need be used when (and if) we'll add support to the host 181 * SKAS patch. 182 */ 183 184 int arch_switch_tls(struct task_struct *to) 185 { 186 if (!host_supports_tls) 187 return 0; 188 189 /* 190 * We have no need whatsoever to switch TLS for kernel threads; beyond 191 * that, that would also result in us calling os_set_thread_area with 192 * userspace_pid[cpu] == 0, which gives an error. 193 */ 194 if (likely(to->mm)) 195 return load_TLS(O_FORCE, to); 196 197 return 0; 198 } 199 200 static int set_tls_entry(struct task_struct* task, struct user_desc *info, 201 int idx, int flushed) 202 { 203 struct thread_struct *t = &task->thread; 204 205 if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX) 206 return -EINVAL; 207 208 t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].tls = *info; 209 t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].present = 1; 210 t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].flushed = flushed; 211 212 return 0; 213 } 214 215 int arch_set_tls(struct task_struct *new, unsigned long tls) 216 { 217 struct user_desc info; 218 int idx, ret = -EFAULT; 219 220 if (copy_from_user(&info, (void __user *) tls, sizeof(info))) 221 goto out; 222 223 ret = -EINVAL; 224 if (LDT_empty(&info)) 225 goto out; 226 227 idx = info.entry_number; 228 229 ret = set_tls_entry(new, &info, idx, 0); 230 out: 231 return ret; 232 } 233 234 /* XXX: use do_get_thread_area to read the host value? I'm not at all sure! */ 235 static int get_tls_entry(struct task_struct *task, struct user_desc *info, 236 int idx) 237 { 238 struct thread_struct *t = &task->thread; 239 240 if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX) 241 return -EINVAL; 242 243 if (!t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].present) 244 goto clear; 245 246 *info = t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].tls; 247 248 out: 249 /* 250 * Temporary debugging check, to make sure that things have been 251 * flushed. This could be triggered if load_TLS() failed. 252 */ 253 if (unlikely(task == current && 254 !t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].flushed)) { 255 printk(KERN_ERR "get_tls_entry: task with pid %d got here " 256 "without flushed TLS.", current->pid); 257 } 258 259 return 0; 260 clear: 261 /* 262 * When the TLS entry has not been set, the values read to user in the 263 * tls_array are 0 (because it's cleared at boot, see 264 * arch/i386/kernel/head.S:cpu_gdt_table). Emulate that. 265 */ 266 clear_user_desc(info); 267 info->entry_number = idx; 268 goto out; 269 } 270 271 SYSCALL_DEFINE1(set_thread_area, struct user_desc __user *, user_desc) 272 { 273 struct user_desc info; 274 int idx, ret; 275 276 if (!host_supports_tls) 277 return -ENOSYS; 278 279 if (copy_from_user(&info, user_desc, sizeof(info))) 280 return -EFAULT; 281 282 idx = info.entry_number; 283 284 if (idx == -1) { 285 idx = get_free_idx(current); 286 if (idx < 0) 287 return idx; 288 info.entry_number = idx; 289 /* Tell the user which slot we chose for him.*/ 290 if (put_user(idx, &user_desc->entry_number)) 291 return -EFAULT; 292 } 293 294 ret = do_set_thread_area(&info); 295 if (ret) 296 return ret; 297 return set_tls_entry(current, &info, idx, 1); 298 } 299 300 /* 301 * Perform set_thread_area on behalf of the traced child. 302 * Note: error handling is not done on the deferred load, and this differ from 303 * i386. However the only possible error are caused by bugs. 304 */ 305 int ptrace_set_thread_area(struct task_struct *child, int idx, 306 struct user_desc __user *user_desc) 307 { 308 struct user_desc info; 309 310 if (!host_supports_tls) 311 return -EIO; 312 313 if (copy_from_user(&info, user_desc, sizeof(info))) 314 return -EFAULT; 315 316 return set_tls_entry(child, &info, idx, 0); 317 } 318 319 SYSCALL_DEFINE1(get_thread_area, struct user_desc __user *, user_desc) 320 { 321 struct user_desc info; 322 int idx, ret; 323 324 if (!host_supports_tls) 325 return -ENOSYS; 326 327 if (get_user(idx, &user_desc->entry_number)) 328 return -EFAULT; 329 330 ret = get_tls_entry(current, &info, idx); 331 if (ret < 0) 332 goto out; 333 334 if (copy_to_user(user_desc, &info, sizeof(info))) 335 ret = -EFAULT; 336 337 out: 338 return ret; 339 } 340 341 /* 342 * Perform get_thread_area on behalf of the traced child. 343 */ 344 int ptrace_get_thread_area(struct task_struct *child, int idx, 345 struct user_desc __user *user_desc) 346 { 347 struct user_desc info; 348 int ret; 349 350 if (!host_supports_tls) 351 return -EIO; 352 353 ret = get_tls_entry(child, &info, idx); 354 if (ret < 0) 355 goto out; 356 357 if (copy_to_user(user_desc, &info, sizeof(info))) 358 ret = -EFAULT; 359 out: 360 return ret; 361 } 362 363 /* 364 * This code is really i386-only, but it detects and logs x86_64 GDT indexes 365 * if a 32-bit UML is running on a 64-bit host. 366 */ 367 static int __init __setup_host_supports_tls(void) 368 { 369 check_host_supports_tls(&host_supports_tls, &host_gdt_entry_tls_min); 370 if (host_supports_tls) { 371 printk(KERN_INFO "Host TLS support detected\n"); 372 printk(KERN_INFO "Detected host type: "); 373 switch (host_gdt_entry_tls_min) { 374 case GDT_ENTRY_TLS_MIN_I386: 375 printk(KERN_CONT "i386"); 376 break; 377 case GDT_ENTRY_TLS_MIN_X86_64: 378 printk(KERN_CONT "x86_64"); 379 break; 380 } 381 printk(KERN_CONT " (GDT indexes %d to %d)\n", 382 host_gdt_entry_tls_min, 383 host_gdt_entry_tls_min + GDT_ENTRY_TLS_ENTRIES); 384 } else 385 printk(KERN_ERR " Host TLS support NOT detected! " 386 "TLS support inside UML will not work\n"); 387 return 0; 388 } 389 390 __initcall(__setup_host_supports_tls); 391