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TOMOYO Linux Cross Reference
Linux/arch/um/os-Linux/start_up.c

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  1 /*
  2  * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
  3  * Licensed under the GPL
  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/ptrace.h>
 17 #include <sys/stat.h>
 18 #include <sys/wait.h>
 19 #include <asm/unistd.h>
 20 #include "init.h"
 21 #include "kern_constants.h"
 22 #include "os.h"
 23 #include "mem_user.h"
 24 #include "ptrace_user.h"
 25 #include "registers.h"
 26 #include "skas.h"
 27 #include "skas_ptrace.h"
 28 
 29 static void ptrace_child(void)
 30 {
 31         int ret;
 32         /* Calling os_getpid because some libcs cached getpid incorrectly */
 33         int pid = os_getpid(), ppid = getppid();
 34         int sc_result;
 35 
 36         if (change_sig(SIGWINCH, 0) < 0 ||
 37             ptrace(PTRACE_TRACEME, 0, 0, 0) < 0) {
 38                 perror("ptrace");
 39                 kill(pid, SIGKILL);
 40         }
 41         kill(pid, SIGSTOP);
 42 
 43         /*
 44          * This syscall will be intercepted by the parent. Don't call more than
 45          * once, please.
 46          */
 47         sc_result = os_getpid();
 48 
 49         if (sc_result == pid)
 50                 /* Nothing modified by the parent, we are running normally. */
 51                 ret = 1;
 52         else if (sc_result == ppid)
 53                 /*
 54                  * Expected in check_ptrace and check_sysemu when they succeed
 55                  * in modifying the stack frame
 56                  */
 57                 ret = 0;
 58         else
 59                 /* Serious trouble! This could be caused by a bug in host 2.6
 60                  * SKAS3/2.6 patch before release -V6, together with a bug in
 61                  * the UML code itself.
 62                  */
 63                 ret = 2;
 64 
 65         exit(ret);
 66 }
 67 
 68 static void fatal_perror(const char *str)
 69 {
 70         perror(str);
 71         exit(1);
 72 }
 73 
 74 static void fatal(char *fmt, ...)
 75 {
 76         va_list list;
 77 
 78         va_start(list, fmt);
 79         vfprintf(stderr, fmt, list);
 80         va_end(list);
 81 
 82         exit(1);
 83 }
 84 
 85 static void non_fatal(char *fmt, ...)
 86 {
 87         va_list list;
 88 
 89         va_start(list, fmt);
 90         vfprintf(stderr, fmt, list);
 91         va_end(list);
 92 }
 93 
 94 static int start_ptraced_child(void)
 95 {
 96         int pid, n, status;
 97 
 98         pid = fork();
 99         if (pid == 0)
100                 ptrace_child();
101         else if (pid < 0)
102                 fatal_perror("start_ptraced_child : fork failed");
103 
104         CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
105         if (n < 0)
106                 fatal_perror("check_ptrace : waitpid failed");
107         if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP))
108                 fatal("check_ptrace : expected SIGSTOP, got status = %d",
109                       status);
110 
111         return pid;
112 }
113 
114 /* When testing for SYSEMU support, if it is one of the broken versions, we
115  * must just avoid using sysemu, not panic, but only if SYSEMU features are
116  * broken.
117  * So only for SYSEMU features we test mustpanic, while normal host features
118  * must work anyway!
119  */
120 static int stop_ptraced_child(int pid, int exitcode, int mustexit)
121 {
122         int status, n, ret = 0;
123 
124         if (ptrace(PTRACE_CONT, pid, 0, 0) < 0) {
125                 perror("stop_ptraced_child : ptrace failed");
126                 return -1;
127         }
128         CATCH_EINTR(n = waitpid(pid, &status, 0));
129         if (!WIFEXITED(status) || (WEXITSTATUS(status) != exitcode)) {
130                 int exit_with = WEXITSTATUS(status);
131                 if (exit_with == 2)
132                         non_fatal("check_ptrace : child exited with status 2. "
133                                   "\nDisabling SYSEMU support.\n");
134                 non_fatal("check_ptrace : child exited with exitcode %d, while "
135                           "expecting %d; status 0x%x\n", exit_with,
136                           exitcode, status);
137                 if (mustexit)
138                         exit(1);
139                 ret = -1;
140         }
141 
142         return ret;
143 }
144 
145 /* Changed only during early boot */
146 int ptrace_faultinfo;
147 static int disable_ptrace_faultinfo;
148 
149 int ptrace_ldt;
150 static int disable_ptrace_ldt;
151 
152 int proc_mm;
153 static int disable_proc_mm;
154 
155 int have_switch_mm;
156 static int disable_switch_mm;
157 
158 int skas_needs_stub;
159 
160 static int __init skas0_cmd_param(char *str, int* add)
161 {
162         disable_ptrace_faultinfo = 1;
163         disable_ptrace_ldt = 1;
164         disable_proc_mm = 1;
165         disable_switch_mm = 1;
166 
167         return 0;
168 }
169 
170 /* The two __uml_setup would conflict, without this stupid alias. */
171 
172 static int __init mode_skas0_cmd_param(char *str, int* add)
173         __attribute__((alias("skas0_cmd_param")));
174 
175 __uml_setup("skas0", skas0_cmd_param,
176 "skas0\n"
177 "    Disables SKAS3 and SKAS4 usage, so that SKAS0 is used\n\n");
178 
179 __uml_setup("mode=skas0", mode_skas0_cmd_param,
180 "mode=skas0\n"
181 "    Disables SKAS3 and SKAS4 usage, so that SKAS0 is used.\n\n");
182 
183 /* Changed only during early boot */
184 static int force_sysemu_disabled = 0;
185 
186 static int __init nosysemu_cmd_param(char *str, int* add)
187 {
188         force_sysemu_disabled = 1;
189         return 0;
190 }
191 
192 __uml_setup("nosysemu", nosysemu_cmd_param,
193 "nosysemu\n"
194 "    Turns off syscall emulation patch for ptrace (SYSEMU) on.\n"
195 "    SYSEMU is a performance-patch introduced by Laurent Vivier. It changes\n"
196 "    behaviour of ptrace() and helps reducing host context switch rate.\n"
197 "    To make it working, you need a kernel patch for your host, too.\n"
198 "    See http://perso.wanadoo.fr/laurent.vivier/UML/ for further \n"
199 "    information.\n\n");
200 
201 static void __init check_sysemu(void)
202 {
203         unsigned long regs[MAX_REG_NR];
204         int pid, n, status, count=0;
205 
206         non_fatal("Checking syscall emulation patch for ptrace...");
207         sysemu_supported = 0;
208         pid = start_ptraced_child();
209 
210         if (ptrace(PTRACE_SYSEMU, pid, 0, 0) < 0)
211                 goto fail;
212 
213         CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
214         if (n < 0)
215                 fatal_perror("check_sysemu : wait failed");
216         if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGTRAP))
217                 fatal("check_sysemu : expected SIGTRAP, got status = %d\n",
218                       status);
219 
220         if (ptrace(PTRACE_GETREGS, pid, 0, regs) < 0)
221                 fatal_perror("check_sysemu : PTRACE_GETREGS failed");
222         if (PT_SYSCALL_NR(regs) != __NR_getpid) {
223                 non_fatal("check_sysemu got system call number %d, "
224                           "expected %d...", PT_SYSCALL_NR(regs), __NR_getpid);
225                 goto fail;
226         }
227 
228         n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_RET_OFFSET, os_getpid());
229         if (n < 0) {
230                 non_fatal("check_sysemu : failed to modify system call "
231                           "return");
232                 goto fail;
233         }
234 
235         if (stop_ptraced_child(pid, 0, 0) < 0)
236                 goto fail_stopped;
237 
238         sysemu_supported = 1;
239         non_fatal("OK\n");
240         set_using_sysemu(!force_sysemu_disabled);
241 
242         non_fatal("Checking advanced syscall emulation patch for ptrace...");
243         pid = start_ptraced_child();
244 
245         if ((ptrace(PTRACE_OLDSETOPTIONS, pid, 0,
246                    (void *) PTRACE_O_TRACESYSGOOD) < 0))
247                 fatal_perror("check_sysemu: PTRACE_OLDSETOPTIONS failed");
248 
249         while (1) {
250                 count++;
251                 if (ptrace(PTRACE_SYSEMU_SINGLESTEP, pid, 0, 0) < 0)
252                         goto fail;
253                 CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
254                 if (n < 0)
255                         fatal_perror("check_sysemu: wait failed");
256 
257                 if (WIFSTOPPED(status) &&
258                     (WSTOPSIG(status) == (SIGTRAP|0x80))) {
259                         if (!count) {
260                                 non_fatal("check_sysemu: SYSEMU_SINGLESTEP "
261                                           "doesn't singlestep");
262                                 goto fail;
263                         }
264                         n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_RET_OFFSET,
265                                    os_getpid());
266                         if (n < 0)
267                                 fatal_perror("check_sysemu : failed to modify "
268                                              "system call return");
269                         break;
270                 }
271                 else if (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGTRAP))
272                         count++;
273                 else {
274                         non_fatal("check_sysemu: expected SIGTRAP or "
275                                   "(SIGTRAP | 0x80), got status = %d\n",
276                                   status);
277                         goto fail;
278                 }
279         }
280         if (stop_ptraced_child(pid, 0, 0) < 0)
281                 goto fail_stopped;
282 
283         sysemu_supported = 2;
284         non_fatal("OK\n");
285 
286         if (!force_sysemu_disabled)
287                 set_using_sysemu(sysemu_supported);
288         return;
289 
290 fail:
291         stop_ptraced_child(pid, 1, 0);
292 fail_stopped:
293         non_fatal("missing\n");
294 }
295 
296 static void __init check_ptrace(void)
297 {
298         int pid, syscall, n, status;
299 
300         non_fatal("Checking that ptrace can change system call numbers...");
301         pid = start_ptraced_child();
302 
303         if ((ptrace(PTRACE_OLDSETOPTIONS, pid, 0,
304                    (void *) PTRACE_O_TRACESYSGOOD) < 0))
305                 fatal_perror("check_ptrace: PTRACE_OLDSETOPTIONS failed");
306 
307         while (1) {
308                 if (ptrace(PTRACE_SYSCALL, pid, 0, 0) < 0)
309                         fatal_perror("check_ptrace : ptrace failed");
310 
311                 CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
312                 if (n < 0)
313                         fatal_perror("check_ptrace : wait failed");
314 
315                 if (!WIFSTOPPED(status) ||
316                    (WSTOPSIG(status) != (SIGTRAP | 0x80)))
317                         fatal("check_ptrace : expected (SIGTRAP|0x80), "
318                                "got status = %d", status);
319 
320                 syscall = ptrace(PTRACE_PEEKUSR, pid, PT_SYSCALL_NR_OFFSET,
321                                  0);
322                 if (syscall == __NR_getpid) {
323                         n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_NR_OFFSET,
324                                    __NR_getppid);
325                         if (n < 0)
326                                 fatal_perror("check_ptrace : failed to modify "
327                                              "system call");
328                         break;
329                 }
330         }
331         stop_ptraced_child(pid, 0, 1);
332         non_fatal("OK\n");
333         check_sysemu();
334 }
335 
336 extern void check_tmpexec(void);
337 
338 static void __init check_coredump_limit(void)
339 {
340         struct rlimit lim;
341         int err = getrlimit(RLIMIT_CORE, &lim);
342 
343         if (err) {
344                 perror("Getting core dump limit");
345                 return;
346         }
347 
348         printf("Core dump limits :\n\tsoft - ");
349         if (lim.rlim_cur == RLIM_INFINITY)
350                 printf("NONE\n");
351         else printf("%lu\n", lim.rlim_cur);
352 
353         printf("\thard - ");
354         if (lim.rlim_max == RLIM_INFINITY)
355                 printf("NONE\n");
356         else printf("%lu\n", lim.rlim_max);
357 }
358 
359 void __init os_early_checks(void)
360 {
361         int pid;
362 
363         /* Print out the core dump limits early */
364         check_coredump_limit();
365 
366         check_ptrace();
367 
368         /* Need to check this early because mmapping happens before the
369          * kernel is running.
370          */
371         check_tmpexec();
372 
373         pid = start_ptraced_child();
374         if (init_registers(pid))
375                 fatal("Failed to initialize default registers");
376         stop_ptraced_child(pid, 1, 1);
377 }
378 
379 static int __init noprocmm_cmd_param(char *str, int* add)
380 {
381         disable_proc_mm = 1;
382         return 0;
383 }
384 
385 __uml_setup("noprocmm", noprocmm_cmd_param,
386 "noprocmm\n"
387 "    Turns off usage of /proc/mm, even if host supports it.\n"
388 "    To support /proc/mm, the host needs to be patched using\n"
389 "    the current skas3 patch.\n\n");
390 
391 static int __init noptracefaultinfo_cmd_param(char *str, int* add)
392 {
393         disable_ptrace_faultinfo = 1;
394         return 0;
395 }
396 
397 __uml_setup("noptracefaultinfo", noptracefaultinfo_cmd_param,
398 "noptracefaultinfo\n"
399 "    Turns off usage of PTRACE_FAULTINFO, even if host supports\n"
400 "    it. To support PTRACE_FAULTINFO, the host needs to be patched\n"
401 "    using the current skas3 patch.\n\n");
402 
403 static int __init noptraceldt_cmd_param(char *str, int* add)
404 {
405         disable_ptrace_ldt = 1;
406         return 0;
407 }
408 
409 __uml_setup("noptraceldt", noptraceldt_cmd_param,
410 "noptraceldt\n"
411 "    Turns off usage of PTRACE_LDT, even if host supports it.\n"
412 "    To support PTRACE_LDT, the host needs to be patched using\n"
413 "    the current skas3 patch.\n\n");
414 
415 static inline void check_skas3_ptrace_faultinfo(void)
416 {
417         struct ptrace_faultinfo fi;
418         int pid, n;
419 
420         non_fatal("  - PTRACE_FAULTINFO...");
421         pid = start_ptraced_child();
422 
423         n = ptrace(PTRACE_FAULTINFO, pid, 0, &fi);
424         if (n < 0) {
425                 if (errno == EIO)
426                         non_fatal("not found\n");
427                 else
428                         perror("not found");
429         } else if (disable_ptrace_faultinfo)
430                 non_fatal("found but disabled on command line\n");
431         else {
432                 ptrace_faultinfo = 1;
433                 non_fatal("found\n");
434         }
435 
436         stop_ptraced_child(pid, 1, 1);
437 }
438 
439 static inline void check_skas3_ptrace_ldt(void)
440 {
441 #ifdef PTRACE_LDT
442         int pid, n;
443         unsigned char ldtbuf[40];
444         struct ptrace_ldt ldt_op = (struct ptrace_ldt) {
445                 .func = 2, /* read default ldt */
446                 .ptr = ldtbuf,
447                 .bytecount = sizeof(ldtbuf)};
448 
449         non_fatal("  - PTRACE_LDT...");
450         pid = start_ptraced_child();
451 
452         n = ptrace(PTRACE_LDT, pid, 0, (unsigned long) &ldt_op);
453         if (n < 0) {
454                 if (errno == EIO)
455                         non_fatal("not found\n");
456                 else
457                         perror("not found");
458         } else if (disable_ptrace_ldt)
459                 non_fatal("found, but use is disabled\n");
460         else {
461                 ptrace_ldt = 1;
462                 non_fatal("found\n");
463         }
464 
465         stop_ptraced_child(pid, 1, 1);
466 #endif
467 }
468 
469 static inline void check_skas3_proc_mm(void)
470 {
471         non_fatal("  - /proc/mm...");
472         if (access("/proc/mm", W_OK) < 0)
473                 perror("not found");
474         else if (disable_proc_mm)
475                 non_fatal("found but disabled on command line\n");
476         else {
477                 proc_mm = 1;
478                 non_fatal("found\n");
479         }
480 }
481 
482 void can_do_skas(void)
483 {
484         non_fatal("Checking for the skas3 patch in the host:\n");
485 
486         check_skas3_proc_mm();
487         check_skas3_ptrace_faultinfo();
488         check_skas3_ptrace_ldt();
489 
490         if (!proc_mm || !ptrace_faultinfo || !ptrace_ldt)
491                 skas_needs_stub = 1;
492 }
493 
494 int __init parse_iomem(char *str, int *add)
495 {
496         struct iomem_region *new;
497         struct stat64 buf;
498         char *file, *driver;
499         int fd, size;
500 
501         driver = str;
502         file = strchr(str,',');
503         if (file == NULL) {
504                 fprintf(stderr, "parse_iomem : failed to parse iomem\n");
505                 goto out;
506         }
507         *file = '\0';
508         file++;
509         fd = open(file, O_RDWR, 0);
510         if (fd < 0) {
511                 perror("parse_iomem - Couldn't open io file");
512                 goto out;
513         }
514 
515         if (fstat64(fd, &buf) < 0) {
516                 perror("parse_iomem - cannot stat_fd file");
517                 goto out_close;
518         }
519 
520         new = malloc(sizeof(*new));
521         if (new == NULL) {
522                 perror("Couldn't allocate iomem_region struct");
523                 goto out_close;
524         }
525 
526         size = (buf.st_size + UM_KERN_PAGE_SIZE) & ~(UM_KERN_PAGE_SIZE - 1);
527 
528         *new = ((struct iomem_region) { .next           = iomem_regions,
529                                         .driver         = driver,
530                                         .fd             = fd,
531                                         .size           = size,
532                                         .phys           = 0,
533                                         .virt           = 0 });
534         iomem_regions = new;
535         iomem_size += new->size + UM_KERN_PAGE_SIZE;
536 
537         return 0;
538  out_close:
539         close(fd);
540  out:
541         return 1;
542 }
543 

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