1 /* SPDX-License-Identifier: GPL-2.0 */
2 
3 #define _GNU_SOURCE
4 
5 #include <stdio.h>
6 #include <sys/time.h>
7 #include <time.h>
8 #include <stdlib.h>
9 #include <sys/syscall.h>
10 #include <unistd.h>
11 #include <dlfcn.h>
12 #include <string.h>
13 #include <inttypes.h>
14 #include <signal.h>
15 #include <sys/ucontext.h>
16 #include <errno.h>
17 #include <err.h>
18 #include <sched.h>
19 #include <stdbool.h>
20 #include <setjmp.h>
21 #include <sys/uio.h>
22 
23 #include "helpers.h"
24 
25 #ifdef __x86_64__
26 # define VSYS(x) (x)
27 #else
28 # define VSYS(x) 0
29 #endif
30 
31 #ifndef SYS_getcpu
32 # ifdef __x86_64__
33 #  define SYS_getcpu 309
34 # else
35 #  define SYS_getcpu 318
36 # endif
37 #endif
38 
39 /* max length of lines in /proc/self/maps - anything longer is skipped here */
40 #define MAPS_LINE_LEN 128
41 
sethandler(int sig,void (* handler)(int,siginfo_t *,void *),int flags)42 static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
43 		       int flags)
44 {
45 	struct sigaction sa;
46 	memset(&sa, 0, sizeof(sa));
47 	sa.sa_sigaction = handler;
48 	sa.sa_flags = SA_SIGINFO | flags;
49 	sigemptyset(&sa.sa_mask);
50 	if (sigaction(sig, &sa, 0))
51 		err(1, "sigaction");
52 }
53 
54 /* vsyscalls and vDSO */
55 bool vsyscall_map_r = false, vsyscall_map_x = false;
56 
57 typedef long (*gtod_t)(struct timeval *tv, struct timezone *tz);
58 const gtod_t vgtod = (gtod_t)VSYS(0xffffffffff600000);
59 gtod_t vdso_gtod;
60 
61 typedef int (*vgettime_t)(clockid_t, struct timespec *);
62 vgettime_t vdso_gettime;
63 
64 typedef long (*time_func_t)(time_t *t);
65 const time_func_t vtime = (time_func_t)VSYS(0xffffffffff600400);
66 time_func_t vdso_time;
67 
68 typedef long (*getcpu_t)(unsigned *, unsigned *, void *);
69 const getcpu_t vgetcpu = (getcpu_t)VSYS(0xffffffffff600800);
70 getcpu_t vdso_getcpu;
71 
init_vdso(void)72 static void init_vdso(void)
73 {
74 	void *vdso = dlopen("linux-vdso.so.1", RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD);
75 	if (!vdso)
76 		vdso = dlopen("linux-gate.so.1", RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD);
77 	if (!vdso) {
78 		printf("[WARN]\tfailed to find vDSO\n");
79 		return;
80 	}
81 
82 	vdso_gtod = (gtod_t)dlsym(vdso, "__vdso_gettimeofday");
83 	if (!vdso_gtod)
84 		printf("[WARN]\tfailed to find gettimeofday in vDSO\n");
85 
86 	vdso_gettime = (vgettime_t)dlsym(vdso, "__vdso_clock_gettime");
87 	if (!vdso_gettime)
88 		printf("[WARN]\tfailed to find clock_gettime in vDSO\n");
89 
90 	vdso_time = (time_func_t)dlsym(vdso, "__vdso_time");
91 	if (!vdso_time)
92 		printf("[WARN]\tfailed to find time in vDSO\n");
93 
94 	vdso_getcpu = (getcpu_t)dlsym(vdso, "__vdso_getcpu");
95 	if (!vdso_getcpu) {
96 		/* getcpu() was never wired up in the 32-bit vDSO. */
97 		printf("[%s]\tfailed to find getcpu in vDSO\n",
98 		       sizeof(long) == 8 ? "WARN" : "NOTE");
99 	}
100 }
101 
init_vsys(void)102 static int init_vsys(void)
103 {
104 #ifdef __x86_64__
105 	int nerrs = 0;
106 	FILE *maps;
107 	char line[MAPS_LINE_LEN];
108 	bool found = false;
109 
110 	maps = fopen("/proc/self/maps", "r");
111 	if (!maps) {
112 		printf("[WARN]\tCould not open /proc/self/maps -- assuming vsyscall is r-x\n");
113 		vsyscall_map_r = true;
114 		return 0;
115 	}
116 
117 	while (fgets(line, MAPS_LINE_LEN, maps)) {
118 		char r, x;
119 		void *start, *end;
120 		char name[MAPS_LINE_LEN];
121 
122 		/* sscanf() is safe here as strlen(name) >= strlen(line) */
123 		if (sscanf(line, "%p-%p %c-%cp %*x %*x:%*x %*u %s",
124 			   &start, &end, &r, &x, name) != 5)
125 			continue;
126 
127 		if (strcmp(name, "[vsyscall]"))
128 			continue;
129 
130 		printf("\tvsyscall map: %s", line);
131 
132 		if (start != (void *)0xffffffffff600000 ||
133 		    end != (void *)0xffffffffff601000) {
134 			printf("[FAIL]\taddress range is nonsense\n");
135 			nerrs++;
136 		}
137 
138 		printf("\tvsyscall permissions are %c-%c\n", r, x);
139 		vsyscall_map_r = (r == 'r');
140 		vsyscall_map_x = (x == 'x');
141 
142 		found = true;
143 		break;
144 	}
145 
146 	fclose(maps);
147 
148 	if (!found) {
149 		printf("\tno vsyscall map in /proc/self/maps\n");
150 		vsyscall_map_r = false;
151 		vsyscall_map_x = false;
152 	}
153 
154 	return nerrs;
155 #else
156 	return 0;
157 #endif
158 }
159 
160 /* syscalls */
sys_gtod(struct timeval * tv,struct timezone * tz)161 static inline long sys_gtod(struct timeval *tv, struct timezone *tz)
162 {
163 	return syscall(SYS_gettimeofday, tv, tz);
164 }
165 
sys_clock_gettime(clockid_t id,struct timespec * ts)166 static inline int sys_clock_gettime(clockid_t id, struct timespec *ts)
167 {
168 	return syscall(SYS_clock_gettime, id, ts);
169 }
170 
sys_time(time_t * t)171 static inline long sys_time(time_t *t)
172 {
173 	return syscall(SYS_time, t);
174 }
175 
sys_getcpu(unsigned * cpu,unsigned * node,void * cache)176 static inline long sys_getcpu(unsigned * cpu, unsigned * node,
177 			      void* cache)
178 {
179 	return syscall(SYS_getcpu, cpu, node, cache);
180 }
181 
182 static jmp_buf jmpbuf;
183 static volatile unsigned long segv_err;
184 
sigsegv(int sig,siginfo_t * info,void * ctx_void)185 static void sigsegv(int sig, siginfo_t *info, void *ctx_void)
186 {
187 	ucontext_t *ctx = (ucontext_t *)ctx_void;
188 
189 	segv_err =  ctx->uc_mcontext.gregs[REG_ERR];
190 	siglongjmp(jmpbuf, 1);
191 }
192 
tv_diff(const struct timeval * a,const struct timeval * b)193 static double tv_diff(const struct timeval *a, const struct timeval *b)
194 {
195 	return (double)(a->tv_sec - b->tv_sec) +
196 		(double)((int)a->tv_usec - (int)b->tv_usec) * 1e-6;
197 }
198 
check_gtod(const struct timeval * tv_sys1,const struct timeval * tv_sys2,const struct timezone * tz_sys,const char * which,const struct timeval * tv_other,const struct timezone * tz_other)199 static int check_gtod(const struct timeval *tv_sys1,
200 		      const struct timeval *tv_sys2,
201 		      const struct timezone *tz_sys,
202 		      const char *which,
203 		      const struct timeval *tv_other,
204 		      const struct timezone *tz_other)
205 {
206 	int nerrs = 0;
207 	double d1, d2;
208 
209 	if (tz_other && (tz_sys->tz_minuteswest != tz_other->tz_minuteswest || tz_sys->tz_dsttime != tz_other->tz_dsttime)) {
210 		printf("[FAIL] %s tz mismatch\n", which);
211 		nerrs++;
212 	}
213 
214 	d1 = tv_diff(tv_other, tv_sys1);
215 	d2 = tv_diff(tv_sys2, tv_other);
216 	printf("\t%s time offsets: %lf %lf\n", which, d1, d2);
217 
218 	if (d1 < 0 || d2 < 0) {
219 		printf("[FAIL]\t%s time was inconsistent with the syscall\n", which);
220 		nerrs++;
221 	} else {
222 		printf("[OK]\t%s gettimeofday()'s timeval was okay\n", which);
223 	}
224 
225 	return nerrs;
226 }
227 
test_gtod(void)228 static int test_gtod(void)
229 {
230 	struct timeval tv_sys1, tv_sys2, tv_vdso, tv_vsys;
231 	struct timezone tz_sys, tz_vdso, tz_vsys;
232 	long ret_vdso = -1;
233 	long ret_vsys = -1;
234 	int nerrs = 0;
235 
236 	printf("[RUN]\ttest gettimeofday()\n");
237 
238 	if (sys_gtod(&tv_sys1, &tz_sys) != 0)
239 		err(1, "syscall gettimeofday");
240 	if (vdso_gtod)
241 		ret_vdso = vdso_gtod(&tv_vdso, &tz_vdso);
242 	if (vsyscall_map_x)
243 		ret_vsys = vgtod(&tv_vsys, &tz_vsys);
244 	if (sys_gtod(&tv_sys2, &tz_sys) != 0)
245 		err(1, "syscall gettimeofday");
246 
247 	if (vdso_gtod) {
248 		if (ret_vdso == 0) {
249 			nerrs += check_gtod(&tv_sys1, &tv_sys2, &tz_sys, "vDSO", &tv_vdso, &tz_vdso);
250 		} else {
251 			printf("[FAIL]\tvDSO gettimeofday() failed: %ld\n", ret_vdso);
252 			nerrs++;
253 		}
254 	}
255 
256 	if (vsyscall_map_x) {
257 		if (ret_vsys == 0) {
258 			nerrs += check_gtod(&tv_sys1, &tv_sys2, &tz_sys, "vsyscall", &tv_vsys, &tz_vsys);
259 		} else {
260 			printf("[FAIL]\tvsys gettimeofday() failed: %ld\n", ret_vsys);
261 			nerrs++;
262 		}
263 	}
264 
265 	return nerrs;
266 }
267 
test_time(void)268 static int test_time(void) {
269 	int nerrs = 0;
270 
271 	printf("[RUN]\ttest time()\n");
272 	long t_sys1, t_sys2, t_vdso = 0, t_vsys = 0;
273 	long t2_sys1 = -1, t2_sys2 = -1, t2_vdso = -1, t2_vsys = -1;
274 	t_sys1 = sys_time(&t2_sys1);
275 	if (vdso_time)
276 		t_vdso = vdso_time(&t2_vdso);
277 	if (vsyscall_map_x)
278 		t_vsys = vtime(&t2_vsys);
279 	t_sys2 = sys_time(&t2_sys2);
280 	if (t_sys1 < 0 || t_sys1 != t2_sys1 || t_sys2 < 0 || t_sys2 != t2_sys2) {
281 		printf("[FAIL]\tsyscall failed (ret1:%ld output1:%ld ret2:%ld output2:%ld)\n", t_sys1, t2_sys1, t_sys2, t2_sys2);
282 		nerrs++;
283 		return nerrs;
284 	}
285 
286 	if (vdso_time) {
287 		if (t_vdso < 0 || t_vdso != t2_vdso) {
288 			printf("[FAIL]\tvDSO failed (ret:%ld output:%ld)\n", t_vdso, t2_vdso);
289 			nerrs++;
290 		} else if (t_vdso < t_sys1 || t_vdso > t_sys2) {
291 			printf("[FAIL]\tvDSO returned the wrong time (%ld %ld %ld)\n", t_sys1, t_vdso, t_sys2);
292 			nerrs++;
293 		} else {
294 			printf("[OK]\tvDSO time() is okay\n");
295 		}
296 	}
297 
298 	if (vsyscall_map_x) {
299 		if (t_vsys < 0 || t_vsys != t2_vsys) {
300 			printf("[FAIL]\tvsyscall failed (ret:%ld output:%ld)\n", t_vsys, t2_vsys);
301 			nerrs++;
302 		} else if (t_vsys < t_sys1 || t_vsys > t_sys2) {
303 			printf("[FAIL]\tvsyscall returned the wrong time (%ld %ld %ld)\n", t_sys1, t_vsys, t_sys2);
304 			nerrs++;
305 		} else {
306 			printf("[OK]\tvsyscall time() is okay\n");
307 		}
308 	}
309 
310 	return nerrs;
311 }
312 
test_getcpu(int cpu)313 static int test_getcpu(int cpu)
314 {
315 	int nerrs = 0;
316 	long ret_sys, ret_vdso = -1, ret_vsys = -1;
317 
318 	printf("[RUN]\tgetcpu() on CPU %d\n", cpu);
319 
320 	cpu_set_t cpuset;
321 	CPU_ZERO(&cpuset);
322 	CPU_SET(cpu, &cpuset);
323 	if (sched_setaffinity(0, sizeof(cpuset), &cpuset) != 0) {
324 		printf("[SKIP]\tfailed to force CPU %d\n", cpu);
325 		return nerrs;
326 	}
327 
328 	unsigned cpu_sys, cpu_vdso, cpu_vsys, node_sys, node_vdso, node_vsys;
329 	unsigned node = 0;
330 	bool have_node = false;
331 	ret_sys = sys_getcpu(&cpu_sys, &node_sys, 0);
332 	if (vdso_getcpu)
333 		ret_vdso = vdso_getcpu(&cpu_vdso, &node_vdso, 0);
334 	if (vsyscall_map_x)
335 		ret_vsys = vgetcpu(&cpu_vsys, &node_vsys, 0);
336 
337 	if (ret_sys == 0) {
338 		if (cpu_sys != cpu) {
339 			printf("[FAIL]\tsyscall reported CPU %hu but should be %d\n", cpu_sys, cpu);
340 			nerrs++;
341 		}
342 
343 		have_node = true;
344 		node = node_sys;
345 	}
346 
347 	if (vdso_getcpu) {
348 		if (ret_vdso) {
349 			printf("[FAIL]\tvDSO getcpu() failed\n");
350 			nerrs++;
351 		} else {
352 			if (!have_node) {
353 				have_node = true;
354 				node = node_vdso;
355 			}
356 
357 			if (cpu_vdso != cpu) {
358 				printf("[FAIL]\tvDSO reported CPU %hu but should be %d\n", cpu_vdso, cpu);
359 				nerrs++;
360 			} else {
361 				printf("[OK]\tvDSO reported correct CPU\n");
362 			}
363 
364 			if (node_vdso != node) {
365 				printf("[FAIL]\tvDSO reported node %hu but should be %hu\n", node_vdso, node);
366 				nerrs++;
367 			} else {
368 				printf("[OK]\tvDSO reported correct node\n");
369 			}
370 		}
371 	}
372 
373 	if (vsyscall_map_x) {
374 		if (ret_vsys) {
375 			printf("[FAIL]\tvsyscall getcpu() failed\n");
376 			nerrs++;
377 		} else {
378 			if (!have_node) {
379 				have_node = true;
380 				node = node_vsys;
381 			}
382 
383 			if (cpu_vsys != cpu) {
384 				printf("[FAIL]\tvsyscall reported CPU %hu but should be %d\n", cpu_vsys, cpu);
385 				nerrs++;
386 			} else {
387 				printf("[OK]\tvsyscall reported correct CPU\n");
388 			}
389 
390 			if (node_vsys != node) {
391 				printf("[FAIL]\tvsyscall reported node %hu but should be %hu\n", node_vsys, node);
392 				nerrs++;
393 			} else {
394 				printf("[OK]\tvsyscall reported correct node\n");
395 			}
396 		}
397 	}
398 
399 	return nerrs;
400 }
401 
test_vsys_r(void)402 static int test_vsys_r(void)
403 {
404 #ifdef __x86_64__
405 	printf("[RUN]\tChecking read access to the vsyscall page\n");
406 	bool can_read;
407 	if (sigsetjmp(jmpbuf, 1) == 0) {
408 		*(volatile int *)0xffffffffff600000;
409 		can_read = true;
410 	} else {
411 		can_read = false;
412 	}
413 
414 	if (can_read && !vsyscall_map_r) {
415 		printf("[FAIL]\tWe have read access, but we shouldn't\n");
416 		return 1;
417 	} else if (!can_read && vsyscall_map_r) {
418 		printf("[FAIL]\tWe don't have read access, but we should\n");
419 		return 1;
420 	} else if (can_read) {
421 		printf("[OK]\tWe have read access\n");
422 	} else {
423 		printf("[OK]\tWe do not have read access: #PF(0x%lx)\n",
424 		       segv_err);
425 	}
426 #endif
427 
428 	return 0;
429 }
430 
test_vsys_x(void)431 static int test_vsys_x(void)
432 {
433 #ifdef __x86_64__
434 	if (vsyscall_map_x) {
435 		/* We already tested this adequately. */
436 		return 0;
437 	}
438 
439 	printf("[RUN]\tMake sure that vsyscalls really page fault\n");
440 
441 	bool can_exec;
442 	if (sigsetjmp(jmpbuf, 1) == 0) {
443 		vgtod(NULL, NULL);
444 		can_exec = true;
445 	} else {
446 		can_exec = false;
447 	}
448 
449 	if (can_exec) {
450 		printf("[FAIL]\tExecuting the vsyscall did not page fault\n");
451 		return 1;
452 	} else if (segv_err & (1 << 4)) { /* INSTR */
453 		printf("[OK]\tExecuting the vsyscall page failed: #PF(0x%lx)\n",
454 		       segv_err);
455 	} else {
456 		printf("[FAIL]\tExecution failed with the wrong error: #PF(0x%lx)\n",
457 		       segv_err);
458 		return 1;
459 	}
460 #endif
461 
462 	return 0;
463 }
464 
465 /*
466  * Debuggers expect ptrace() to be able to peek at the vsyscall page.
467  * Use process_vm_readv() as a proxy for ptrace() to test this.  We
468  * want it to work in the vsyscall=emulate case and to fail in the
469  * vsyscall=xonly case.
470  *
471  * It's worth noting that this ABI is a bit nutty.  write(2) can't
472  * read from the vsyscall page on any kernel version or mode.  The
473  * fact that ptrace() ever worked was a nice courtesy of old kernels,
474  * but the code to support it is fairly gross.
475  */
test_process_vm_readv(void)476 static int test_process_vm_readv(void)
477 {
478 #ifdef __x86_64__
479 	char buf[4096];
480 	struct iovec local, remote;
481 	int ret;
482 
483 	printf("[RUN]\tprocess_vm_readv() from vsyscall page\n");
484 
485 	local.iov_base = buf;
486 	local.iov_len = 4096;
487 	remote.iov_base = (void *)0xffffffffff600000;
488 	remote.iov_len = 4096;
489 	ret = process_vm_readv(getpid(), &local, 1, &remote, 1, 0);
490 	if (ret != 4096) {
491 		/*
492 		 * We expect process_vm_readv() to work if and only if the
493 		 * vsyscall page is readable.
494 		 */
495 		printf("[%s]\tprocess_vm_readv() failed (ret = %d, errno = %d)\n", vsyscall_map_r ? "FAIL" : "OK", ret, errno);
496 		return vsyscall_map_r ? 1 : 0;
497 	}
498 
499 	if (vsyscall_map_r) {
500 		if (!memcmp(buf, (const void *)0xffffffffff600000, 4096)) {
501 			printf("[OK]\tIt worked and read correct data\n");
502 		} else {
503 			printf("[FAIL]\tIt worked but returned incorrect data\n");
504 			return 1;
505 		}
506 	} else {
507 		printf("[FAIL]\tprocess_rm_readv() succeeded, but it should have failed in this configuration\n");
508 		return 1;
509 	}
510 #endif
511 
512 	return 0;
513 }
514 
515 #ifdef __x86_64__
516 static volatile sig_atomic_t num_vsyscall_traps;
517 
sigtrap(int sig,siginfo_t * info,void * ctx_void)518 static void sigtrap(int sig, siginfo_t *info, void *ctx_void)
519 {
520 	ucontext_t *ctx = (ucontext_t *)ctx_void;
521 	unsigned long ip = ctx->uc_mcontext.gregs[REG_RIP];
522 
523 	if (((ip ^ 0xffffffffff600000UL) & ~0xfffUL) == 0)
524 		num_vsyscall_traps++;
525 }
526 
test_emulation(void)527 static int test_emulation(void)
528 {
529 	time_t tmp;
530 	bool is_native;
531 
532 	if (!vsyscall_map_x)
533 		return 0;
534 
535 	printf("[RUN]\tchecking that vsyscalls are emulated\n");
536 	sethandler(SIGTRAP, sigtrap, 0);
537 	set_eflags(get_eflags() | X86_EFLAGS_TF);
538 	vtime(&tmp);
539 	set_eflags(get_eflags() & ~X86_EFLAGS_TF);
540 
541 	/*
542 	 * If vsyscalls are emulated, we expect a single trap in the
543 	 * vsyscall page -- the call instruction will trap with RIP
544 	 * pointing to the entry point before emulation takes over.
545 	 * In native mode, we expect two traps, since whatever code
546 	 * the vsyscall page contains will be more than just a ret
547 	 * instruction.
548 	 */
549 	is_native = (num_vsyscall_traps > 1);
550 
551 	printf("[%s]\tvsyscalls are %s (%d instructions in vsyscall page)\n",
552 	       (is_native ? "FAIL" : "OK"),
553 	       (is_native ? "native" : "emulated"),
554 	       (int)num_vsyscall_traps);
555 
556 	return is_native;
557 }
558 #endif
559 
main(int argc,char ** argv)560 int main(int argc, char **argv)
561 {
562 	int nerrs = 0;
563 
564 	init_vdso();
565 	nerrs += init_vsys();
566 
567 	nerrs += test_gtod();
568 	nerrs += test_time();
569 	nerrs += test_getcpu(0);
570 	nerrs += test_getcpu(1);
571 
572 	sethandler(SIGSEGV, sigsegv, 0);
573 	nerrs += test_vsys_r();
574 	nerrs += test_vsys_x();
575 
576 	nerrs += test_process_vm_readv();
577 
578 #ifdef __x86_64__
579 	nerrs += test_emulation();
580 #endif
581 
582 	return nerrs ? 1 : 0;
583 }
584