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1#if defined __amd64__ || defined __i386__
2/*
3 * Copyright (c) 2022 Alexey Dobriyan <[email protected]>
4 *
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 */
17/*
18 * Create a process without mappings by unmapping everything at once and
19 * holding it with ptrace(2). See what happens to
20 *
21 * /proc/${pid}/maps
22 * /proc/${pid}/numa_maps
23 * /proc/${pid}/smaps
24 * /proc/${pid}/smaps_rollup
25 */
26#undef _GNU_SOURCE
27#define _GNU_SOURCE
28
29#undef NDEBUG
30#include <assert.h>
31#include <errno.h>
32#include <stdint.h>
33#include <stdio.h>
34#include <stdlib.h>
35#include <string.h>
36#include <fcntl.h>
37#include <sys/mman.h>
38#include <sys/ptrace.h>
39#include <sys/resource.h>
40#include <sys/syscall.h>
41#include <sys/types.h>
42#include <sys/wait.h>
43#include <unistd.h>
44
45#ifdef __amd64__
46#define TEST_VSYSCALL
47#endif
48
49#if defined __amd64__
50 #ifndef SYS_pkey_alloc
51 #define SYS_pkey_alloc 330
52 #endif
53 #ifndef SYS_pkey_free
54 #define SYS_pkey_free 331
55 #endif
56#elif defined __i386__
57 #ifndef SYS_pkey_alloc
58 #define SYS_pkey_alloc 381
59 #endif
60 #ifndef SYS_pkey_free
61 #define SYS_pkey_free 382
62 #endif
63#else
64 #error "SYS_pkey_alloc"
65#endif
66
67static int g_protection_key_support;
68
69static int protection_key_support(void)
70{
71 long rv = syscall(SYS_pkey_alloc, 0, 0);
72 if (rv > 0) {
73 syscall(SYS_pkey_free, (int)rv);
74 return 1;
75 } else if (rv == -1 && errno == ENOSYS) {
76 return 0;
77 } else if (rv == -1 && errno == EINVAL) {
78 // ospke=n
79 return 0;
80 } else {
81 fprintf(stderr, "%s: error: rv %ld, errno %d\n", __func__, rv, errno);
82 exit(EXIT_FAILURE);
83 }
84}
85
86/*
87 * 0: vsyscall VMA doesn't exist vsyscall=none
88 * 1: vsyscall VMA is --xp vsyscall=xonly
89 * 2: vsyscall VMA is r-xp vsyscall=emulate
90 */
91static volatile int g_vsyscall;
92static const char *g_proc_pid_maps_vsyscall;
93static const char *g_proc_pid_smaps_vsyscall;
94
95static const char proc_pid_maps_vsyscall_0[] = "";
96static const char proc_pid_maps_vsyscall_1[] =
97"ffffffffff600000-ffffffffff601000 --xp 00000000 00:00 0 [vsyscall]\n";
98static const char proc_pid_maps_vsyscall_2[] =
99"ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0 [vsyscall]\n";
100
101static const char proc_pid_smaps_vsyscall_0[] = "";
102
103static const char proc_pid_smaps_vsyscall_1[] =
104"ffffffffff600000-ffffffffff601000 --xp 00000000 00:00 0 [vsyscall]\n"
105"Size: 4 kB\n"
106"KernelPageSize: 4 kB\n"
107"MMUPageSize: 4 kB\n"
108"Rss: 0 kB\n"
109"Pss: 0 kB\n"
110"Pss_Dirty: 0 kB\n"
111"Shared_Clean: 0 kB\n"
112"Shared_Dirty: 0 kB\n"
113"Private_Clean: 0 kB\n"
114"Private_Dirty: 0 kB\n"
115"Referenced: 0 kB\n"
116"Anonymous: 0 kB\n"
117"KSM: 0 kB\n"
118"LazyFree: 0 kB\n"
119"AnonHugePages: 0 kB\n"
120"ShmemPmdMapped: 0 kB\n"
121"FilePmdMapped: 0 kB\n"
122"Shared_Hugetlb: 0 kB\n"
123"Private_Hugetlb: 0 kB\n"
124"Swap: 0 kB\n"
125"SwapPss: 0 kB\n"
126"Locked: 0 kB\n"
127"THPeligible: 0\n"
128;
129
130static const char proc_pid_smaps_vsyscall_2[] =
131"ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0 [vsyscall]\n"
132"Size: 4 kB\n"
133"KernelPageSize: 4 kB\n"
134"MMUPageSize: 4 kB\n"
135"Rss: 0 kB\n"
136"Pss: 0 kB\n"
137"Pss_Dirty: 0 kB\n"
138"Shared_Clean: 0 kB\n"
139"Shared_Dirty: 0 kB\n"
140"Private_Clean: 0 kB\n"
141"Private_Dirty: 0 kB\n"
142"Referenced: 0 kB\n"
143"Anonymous: 0 kB\n"
144"KSM: 0 kB\n"
145"LazyFree: 0 kB\n"
146"AnonHugePages: 0 kB\n"
147"ShmemPmdMapped: 0 kB\n"
148"FilePmdMapped: 0 kB\n"
149"Shared_Hugetlb: 0 kB\n"
150"Private_Hugetlb: 0 kB\n"
151"Swap: 0 kB\n"
152"SwapPss: 0 kB\n"
153"Locked: 0 kB\n"
154"THPeligible: 0\n"
155;
156
157static void sigaction_SIGSEGV(int _, siginfo_t *__, void *___)
158{
159 _exit(EXIT_FAILURE);
160}
161
162#ifdef TEST_VSYSCALL
163static void sigaction_SIGSEGV_vsyscall(int _, siginfo_t *__, void *___)
164{
165 _exit(g_vsyscall);
166}
167
168/*
169 * vsyscall page can't be unmapped, probe it directly.
170 */
171static void vsyscall(void)
172{
173 pid_t pid;
174 int wstatus;
175
176 pid = fork();
177 if (pid < 0) {
178 fprintf(stderr, "fork, errno %d\n", errno);
179 exit(1);
180 }
181 if (pid == 0) {
182 setrlimit(RLIMIT_CORE, &(struct rlimit){});
183
184 /* Hide "segfault at ffffffffff600000" messages. */
185 struct sigaction act = {};
186 act.sa_flags = SA_SIGINFO;
187 act.sa_sigaction = sigaction_SIGSEGV_vsyscall;
188 sigaction(SIGSEGV, &act, NULL);
189
190 g_vsyscall = 0;
191 /* gettimeofday(NULL, NULL); */
192 uint64_t rax = 0xffffffffff600000;
193 asm volatile (
194 "call *%[rax]"
195 : [rax] "+a" (rax)
196 : "D" (NULL), "S" (NULL)
197 : "rcx", "r11"
198 );
199
200 g_vsyscall = 1;
201 *(volatile int *)0xffffffffff600000UL;
202
203 g_vsyscall = 2;
204 exit(g_vsyscall);
205 }
206 waitpid(pid, &wstatus, 0);
207 if (WIFEXITED(wstatus)) {
208 g_vsyscall = WEXITSTATUS(wstatus);
209 } else {
210 fprintf(stderr, "error: vsyscall wstatus %08x\n", wstatus);
211 exit(1);
212 }
213}
214#endif
215
216static int test_proc_pid_maps(pid_t pid)
217{
218 char buf[4096];
219 snprintf(buf, sizeof(buf), "/proc/%u/maps", pid);
220 int fd = open(buf, O_RDONLY);
221 if (fd == -1) {
222 perror("open /proc/${pid}/maps");
223 return EXIT_FAILURE;
224 } else {
225 ssize_t rv = read(fd, buf, sizeof(buf));
226 close(fd);
227 if (g_vsyscall == 0) {
228 assert(rv == 0);
229 } else {
230 size_t len = strlen(g_proc_pid_maps_vsyscall);
231 assert(rv == len);
232 assert(memcmp(buf, g_proc_pid_maps_vsyscall, len) == 0);
233 }
234 return EXIT_SUCCESS;
235 }
236}
237
238static int test_proc_pid_numa_maps(pid_t pid)
239{
240 char buf[4096];
241 snprintf(buf, sizeof(buf), "/proc/%u/numa_maps", pid);
242 int fd = open(buf, O_RDONLY);
243 if (fd == -1) {
244 if (errno == ENOENT) {
245 /*
246 * /proc/${pid}/numa_maps is under CONFIG_NUMA,
247 * it doesn't necessarily exist.
248 */
249 return EXIT_SUCCESS;
250 }
251 perror("open /proc/${pid}/numa_maps");
252 return EXIT_FAILURE;
253 } else {
254 ssize_t rv = read(fd, buf, sizeof(buf));
255 close(fd);
256 assert(rv == 0);
257 return EXIT_SUCCESS;
258 }
259}
260
261static int test_proc_pid_smaps(pid_t pid)
262{
263 char buf[4096];
264 snprintf(buf, sizeof(buf), "/proc/%u/smaps", pid);
265 int fd = open(buf, O_RDONLY);
266 if (fd == -1) {
267 if (errno == ENOENT) {
268 /*
269 * /proc/${pid}/smaps is under CONFIG_PROC_PAGE_MONITOR,
270 * it doesn't necessarily exist.
271 */
272 return EXIT_SUCCESS;
273 }
274 perror("open /proc/${pid}/smaps");
275 return EXIT_FAILURE;
276 }
277 ssize_t rv = read(fd, buf, sizeof(buf));
278 close(fd);
279
280 assert(0 <= rv);
281 assert(rv <= sizeof(buf));
282
283 if (g_vsyscall == 0) {
284 assert(rv == 0);
285 } else {
286 size_t len = strlen(g_proc_pid_smaps_vsyscall);
287 assert(rv > len);
288 assert(memcmp(buf, g_proc_pid_smaps_vsyscall, len) == 0);
289
290 if (g_protection_key_support) {
291#define PROTECTION_KEY "ProtectionKey: 0\n"
292 assert(memmem(buf, rv, PROTECTION_KEY, strlen(PROTECTION_KEY)));
293 }
294 }
295
296 return EXIT_SUCCESS;
297}
298
299static const char g_smaps_rollup[] =
300"00000000-00000000 ---p 00000000 00:00 0 [rollup]\n"
301"Rss: 0 kB\n"
302"Pss: 0 kB\n"
303"Pss_Dirty: 0 kB\n"
304"Pss_Anon: 0 kB\n"
305"Pss_File: 0 kB\n"
306"Pss_Shmem: 0 kB\n"
307"Shared_Clean: 0 kB\n"
308"Shared_Dirty: 0 kB\n"
309"Private_Clean: 0 kB\n"
310"Private_Dirty: 0 kB\n"
311"Referenced: 0 kB\n"
312"Anonymous: 0 kB\n"
313"KSM: 0 kB\n"
314"LazyFree: 0 kB\n"
315"AnonHugePages: 0 kB\n"
316"ShmemPmdMapped: 0 kB\n"
317"FilePmdMapped: 0 kB\n"
318"Shared_Hugetlb: 0 kB\n"
319"Private_Hugetlb: 0 kB\n"
320"Swap: 0 kB\n"
321"SwapPss: 0 kB\n"
322"Locked: 0 kB\n"
323;
324
325static int test_proc_pid_smaps_rollup(pid_t pid)
326{
327 char buf[4096];
328 snprintf(buf, sizeof(buf), "/proc/%u/smaps_rollup", pid);
329 int fd = open(buf, O_RDONLY);
330 if (fd == -1) {
331 if (errno == ENOENT) {
332 /*
333 * /proc/${pid}/smaps_rollup is under CONFIG_PROC_PAGE_MONITOR,
334 * it doesn't necessarily exist.
335 */
336 return EXIT_SUCCESS;
337 }
338 perror("open /proc/${pid}/smaps_rollup");
339 return EXIT_FAILURE;
340 } else {
341 ssize_t rv = read(fd, buf, sizeof(buf));
342 close(fd);
343 assert(rv == sizeof(g_smaps_rollup) - 1);
344 assert(memcmp(buf, g_smaps_rollup, sizeof(g_smaps_rollup) - 1) == 0);
345 return EXIT_SUCCESS;
346 }
347}
348
349static const char *parse_u64(const char *p, const char *const end, uint64_t *rv)
350{
351 *rv = 0;
352 for (; p != end; p += 1) {
353 if ('0' <= *p && *p <= '9') {
354 assert(!__builtin_mul_overflow(*rv, 10, rv));
355 assert(!__builtin_add_overflow(*rv, *p - '0', rv));
356 } else {
357 break;
358 }
359 }
360 assert(p != end);
361 return p;
362}
363
364/*
365 * There seems to be 2 types of valid output:
366 * "0 A A B 0 0 0\n" for dynamic exeuctables,
367 * "0 0 0 B 0 0 0\n" for static executables.
368 */
369static int test_proc_pid_statm(pid_t pid)
370{
371 char buf[4096];
372 snprintf(buf, sizeof(buf), "/proc/%u/statm", pid);
373 int fd = open(buf, O_RDONLY);
374 if (fd == -1) {
375 perror("open /proc/${pid}/statm");
376 return EXIT_FAILURE;
377 }
378
379 ssize_t rv = read(fd, buf, sizeof(buf));
380 close(fd);
381
382 assert(rv >= 0);
383 assert(rv <= sizeof(buf));
384
385 const char *p = buf;
386 const char *const end = p + rv;
387
388 /* size */
389 assert(p != end && *p++ == '0');
390 assert(p != end && *p++ == ' ');
391
392 uint64_t resident;
393 p = parse_u64(p, end, &resident);
394 assert(p != end && *p++ == ' ');
395
396 uint64_t shared;
397 p = parse_u64(p, end, &shared);
398 assert(p != end && *p++ == ' ');
399
400 uint64_t text;
401 p = parse_u64(p, end, &text);
402 assert(p != end && *p++ == ' ');
403
404 assert(p != end && *p++ == '0');
405 assert(p != end && *p++ == ' ');
406
407 /* data */
408 assert(p != end && *p++ == '0');
409 assert(p != end && *p++ == ' ');
410
411 assert(p != end && *p++ == '0');
412 assert(p != end && *p++ == '\n');
413
414 assert(p == end);
415
416 /*
417 * "text" is "mm->end_code - mm->start_code" at execve(2) time.
418 * munmap() doesn't change it. It can be anything (just link
419 * statically). It can't be 0 because executing to this point
420 * implies at least 1 page of code.
421 */
422 assert(text > 0);
423
424 /*
425 * These two are always equal. Always 0 for statically linked
426 * executables and sometimes 0 for dynamically linked executables.
427 * There is no way to tell one from another without parsing ELF
428 * which is too much for this test.
429 */
430 assert(resident == shared);
431
432 return EXIT_SUCCESS;
433}
434
435int main(void)
436{
437 int rv = EXIT_SUCCESS;
438
439#ifdef TEST_VSYSCALL
440 vsyscall();
441#endif
442
443 switch (g_vsyscall) {
444 case 0:
445 g_proc_pid_maps_vsyscall = proc_pid_maps_vsyscall_0;
446 g_proc_pid_smaps_vsyscall = proc_pid_smaps_vsyscall_0;
447 break;
448 case 1:
449 g_proc_pid_maps_vsyscall = proc_pid_maps_vsyscall_1;
450 g_proc_pid_smaps_vsyscall = proc_pid_smaps_vsyscall_1;
451 break;
452 case 2:
453 g_proc_pid_maps_vsyscall = proc_pid_maps_vsyscall_2;
454 g_proc_pid_smaps_vsyscall = proc_pid_smaps_vsyscall_2;
455 break;
456 default:
457 abort();
458 }
459
460 g_protection_key_support = protection_key_support();
461
462 pid_t pid = fork();
463 if (pid == -1) {
464 perror("fork");
465 return EXIT_FAILURE;
466 } else if (pid == 0) {
467 rv = ptrace(PTRACE_TRACEME, 0, NULL, NULL);
468 if (rv != 0) {
469 if (errno == EPERM) {
470 fprintf(stderr,
471"Did you know? ptrace(PTRACE_TRACEME) doesn't work under strace.\n"
472 );
473 kill(getppid(), SIGTERM);
474 return EXIT_FAILURE;
475 }
476 perror("ptrace PTRACE_TRACEME");
477 return EXIT_FAILURE;
478 }
479
480 /*
481 * Hide "segfault at ..." messages. Signal handler won't run.
482 */
483 struct sigaction act = {};
484 act.sa_flags = SA_SIGINFO;
485 act.sa_sigaction = sigaction_SIGSEGV;
486 sigaction(SIGSEGV, &act, NULL);
487
488#ifdef __amd64__
489 munmap(NULL, ((size_t)1 << 47) - 4096);
490#elif defined __i386__
491 {
492 size_t len;
493
494 for (len = -4096;; len -= 4096) {
495 munmap(NULL, len);
496 }
497 }
498#else
499#error "implement 'unmap everything'"
500#endif
501 return EXIT_FAILURE;
502 } else {
503 /*
504 * TODO find reliable way to signal parent that munmap(2) completed.
505 * Child can't do it directly because it effectively doesn't exist
506 * anymore. Looking at child's VM files isn't 100% reliable either:
507 * due to a bug they may not become empty or empty-like.
508 */
509 sleep(1);
510
511 if (rv == EXIT_SUCCESS) {
512 rv = test_proc_pid_maps(pid);
513 }
514 if (rv == EXIT_SUCCESS) {
515 rv = test_proc_pid_numa_maps(pid);
516 }
517 if (rv == EXIT_SUCCESS) {
518 rv = test_proc_pid_smaps(pid);
519 }
520 if (rv == EXIT_SUCCESS) {
521 rv = test_proc_pid_smaps_rollup(pid);
522 }
523 if (rv == EXIT_SUCCESS) {
524 rv = test_proc_pid_statm(pid);
525 }
526
527 /* Cut the rope. */
528 int wstatus;
529 waitpid(pid, &wstatus, 0);
530 assert(WIFSTOPPED(wstatus));
531 assert(WSTOPSIG(wstatus) == SIGSEGV);
532 }
533
534 return rv;
535}
536#else
537int main(void)
538{
539 return 4;
540}
541#endif