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

source code of linux/tools/testing/selftests/x86/test_vsyscall.c