1 // SPDX-License-Identifier: GPL-2.0
2 #define _GNU_SOURCE
3
4 #include <sys/ptrace.h>
5 #include <sys/types.h>
6 #include <sys/wait.h>
7 #include <sys/syscall.h>
8 #include <sys/user.h>
9 #include <unistd.h>
10 #include <errno.h>
11 #include <stddef.h>
12 #include <stdio.h>
13 #include <err.h>
14 #include <string.h>
15 #include <asm/ptrace-abi.h>
16 #include <sys/auxv.h>
17
18 /* Bitness-agnostic defines for user_regs_struct fields. */
19 #ifdef __x86_64__
20 # define user_syscall_nr orig_rax
21 # define user_arg0 rdi
22 # define user_arg1 rsi
23 # define user_arg2 rdx
24 # define user_arg3 r10
25 # define user_arg4 r8
26 # define user_arg5 r9
27 # define user_ip rip
28 # define user_ax rax
29 #else
30 # define user_syscall_nr orig_eax
31 # define user_arg0 ebx
32 # define user_arg1 ecx
33 # define user_arg2 edx
34 # define user_arg3 esi
35 # define user_arg4 edi
36 # define user_arg5 ebp
37 # define user_ip eip
38 # define user_ax eax
39 #endif
40
41 static int nerrs = 0;
42
43 struct syscall_args32 {
44 uint32_t nr, arg0, arg1, arg2, arg3, arg4, arg5;
45 };
46
47 #ifdef __i386__
48 extern void sys32_helper(struct syscall_args32 *, void *);
49 extern void int80_and_ret(void);
50 #endif
51
52 /*
53 * Helper to invoke int80 with controlled regs and capture the final regs.
54 */
do_full_int80(struct syscall_args32 * args)55 static void do_full_int80(struct syscall_args32 *args)
56 {
57 #ifdef __x86_64__
58 register unsigned long bp asm("bp") = args->arg5;
59 asm volatile ("int $0x80"
60 : "+a" (args->nr),
61 "+b" (args->arg0), "+c" (args->arg1), "+d" (args->arg2),
62 "+S" (args->arg3), "+D" (args->arg4), "+r" (bp)
63 : : "r8", "r9", "r10", "r11");
64 args->arg5 = bp;
65 #else
66 sys32_helper(args, int80_and_ret);
67 #endif
68 }
69
70 #ifdef __i386__
71 static void (*vsyscall32)(void);
72
73 /*
74 * Nasty helper to invoke AT_SYSINFO (i.e. __kernel_vsyscall) with
75 * controlled regs and capture the final regs. This is so nasty that it
76 * crashes my copy of gdb :)
77 */
do_full_vsyscall32(struct syscall_args32 * args)78 static void do_full_vsyscall32(struct syscall_args32 *args)
79 {
80 sys32_helper(args, vsyscall32);
81 }
82 #endif
83
wait_trap(pid_t chld)84 static siginfo_t wait_trap(pid_t chld)
85 {
86 siginfo_t si;
87 if (waitid(P_PID, chld, &si, WEXITED|WSTOPPED) != 0)
88 err(1, "waitid");
89 if (si.si_pid != chld)
90 errx(1, "got unexpected pid in event\n");
91 if (si.si_code != CLD_TRAPPED)
92 errx(1, "got unexpected event type %d\n", si.si_code);
93 return si;
94 }
95
sethandler(int sig,void (* handler)(int,siginfo_t *,void *),int flags)96 static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
97 int flags)
98 {
99 struct sigaction sa;
100 memset(&sa, 0, sizeof(sa));
101 sa.sa_sigaction = handler;
102 sa.sa_flags = SA_SIGINFO | flags;
103 sigemptyset(&sa.sa_mask);
104 if (sigaction(sig, &sa, 0))
105 err(1, "sigaction");
106 }
107
setsigign(int sig,int flags)108 static void setsigign(int sig, int flags)
109 {
110 struct sigaction sa;
111 memset(&sa, 0, sizeof(sa));
112 sa.sa_sigaction = (void *)SIG_IGN;
113 sa.sa_flags = flags;
114 sigemptyset(&sa.sa_mask);
115 if (sigaction(sig, &sa, 0))
116 err(1, "sigaction");
117 }
118
clearhandler(int sig)119 static void clearhandler(int sig)
120 {
121 struct sigaction sa;
122 memset(&sa, 0, sizeof(sa));
123 sa.sa_handler = SIG_DFL;
124 sigemptyset(&sa.sa_mask);
125 if (sigaction(sig, &sa, 0))
126 err(1, "sigaction");
127 }
128
129 #ifdef __x86_64__
130 # define REG_BP REG_RBP
131 #else
132 # define REG_BP REG_EBP
133 #endif
134
empty_handler(int sig,siginfo_t * si,void * ctx_void)135 static void empty_handler(int sig, siginfo_t *si, void *ctx_void)
136 {
137 }
138
test_sys32_regs(void (* do_syscall)(struct syscall_args32 *))139 static void test_sys32_regs(void (*do_syscall)(struct syscall_args32 *))
140 {
141 struct syscall_args32 args = {
142 .nr = 224, /* gettid */
143 .arg0 = 10, .arg1 = 11, .arg2 = 12,
144 .arg3 = 13, .arg4 = 14, .arg5 = 15,
145 };
146
147 do_syscall(&args);
148
149 if (args.nr != getpid() ||
150 args.arg0 != 10 || args.arg1 != 11 || args.arg2 != 12 ||
151 args.arg3 != 13 || args.arg4 != 14 || args.arg5 != 15) {
152 printf("[FAIL]\tgetpid() failed to preserve regs\n");
153 nerrs++;
154 } else {
155 printf("[OK]\tgetpid() preserves regs\n");
156 }
157
158 sethandler(SIGUSR1, empty_handler, 0);
159
160 args.nr = 37; /* kill */
161 args.arg0 = getpid();
162 args.arg1 = SIGUSR1;
163 do_syscall(&args);
164 if (args.nr != 0 ||
165 args.arg0 != getpid() || args.arg1 != SIGUSR1 || args.arg2 != 12 ||
166 args.arg3 != 13 || args.arg4 != 14 || args.arg5 != 15) {
167 printf("[FAIL]\tkill(getpid(), SIGUSR1) failed to preserve regs\n");
168 nerrs++;
169 } else {
170 printf("[OK]\tkill(getpid(), SIGUSR1) preserves regs\n");
171 }
172 clearhandler(SIGUSR1);
173 }
174
test_ptrace_syscall_restart(void)175 static void test_ptrace_syscall_restart(void)
176 {
177 printf("[RUN]\tptrace-induced syscall restart\n");
178 pid_t chld = fork();
179 if (chld < 0)
180 err(1, "fork");
181
182 if (chld == 0) {
183 if (ptrace(PTRACE_TRACEME, 0, 0, 0) != 0)
184 err(1, "PTRACE_TRACEME");
185
186 pid_t pid = getpid(), tid = syscall(SYS_gettid);
187
188 printf("\tChild will make one syscall\n");
189 syscall(SYS_tgkill, pid, tid, SIGSTOP);
190
191 syscall(SYS_gettid, 10, 11, 12, 13, 14, 15);
192 _exit(0);
193 }
194
195 int status;
196
197 /* Wait for SIGSTOP. */
198 if (waitpid(chld, &status, 0) != chld || !WIFSTOPPED(status))
199 err(1, "waitpid");
200
201 struct user_regs_struct regs;
202
203 printf("[RUN]\tSYSEMU\n");
204 if (ptrace(PTRACE_SYSEMU, chld, 0, 0) != 0)
205 err(1, "PTRACE_SYSEMU");
206 wait_trap(chld);
207
208 if (ptrace(PTRACE_GETREGS, chld, 0, ®s) != 0)
209 err(1, "PTRACE_GETREGS");
210
211 if (regs.user_syscall_nr != SYS_gettid ||
212 regs.user_arg0 != 10 || regs.user_arg1 != 11 ||
213 regs.user_arg2 != 12 || regs.user_arg3 != 13 ||
214 regs.user_arg4 != 14 || regs.user_arg5 != 15) {
215 printf("[FAIL]\tInitial args are wrong (nr=%lu, args=%lu %lu %lu %lu %lu %lu)\n", (unsigned long)regs.user_syscall_nr, (unsigned long)regs.user_arg0, (unsigned long)regs.user_arg1, (unsigned long)regs.user_arg2, (unsigned long)regs.user_arg3, (unsigned long)regs.user_arg4, (unsigned long)regs.user_arg5);
216 nerrs++;
217 } else {
218 printf("[OK]\tInitial nr and args are correct\n");
219 }
220
221 printf("[RUN]\tRestart the syscall (ip = 0x%lx)\n",
222 (unsigned long)regs.user_ip);
223
224 /*
225 * This does exactly what it appears to do if syscall is int80 or
226 * SYSCALL64. For SYSCALL32 or SYSENTER, though, this is highly
227 * magical. It needs to work so that ptrace and syscall restart
228 * work as expected.
229 */
230 regs.user_ax = regs.user_syscall_nr;
231 regs.user_ip -= 2;
232 if (ptrace(PTRACE_SETREGS, chld, 0, ®s) != 0)
233 err(1, "PTRACE_SETREGS");
234
235 if (ptrace(PTRACE_SYSEMU, chld, 0, 0) != 0)
236 err(1, "PTRACE_SYSEMU");
237 wait_trap(chld);
238
239 if (ptrace(PTRACE_GETREGS, chld, 0, ®s) != 0)
240 err(1, "PTRACE_GETREGS");
241
242 if (regs.user_syscall_nr != SYS_gettid ||
243 regs.user_arg0 != 10 || regs.user_arg1 != 11 ||
244 regs.user_arg2 != 12 || regs.user_arg3 != 13 ||
245 regs.user_arg4 != 14 || regs.user_arg5 != 15) {
246 printf("[FAIL]\tRestart nr or args are wrong (nr=%lu, args=%lu %lu %lu %lu %lu %lu)\n", (unsigned long)regs.user_syscall_nr, (unsigned long)regs.user_arg0, (unsigned long)regs.user_arg1, (unsigned long)regs.user_arg2, (unsigned long)regs.user_arg3, (unsigned long)regs.user_arg4, (unsigned long)regs.user_arg5);
247 nerrs++;
248 } else {
249 printf("[OK]\tRestarted nr and args are correct\n");
250 }
251
252 printf("[RUN]\tChange nr and args and restart the syscall (ip = 0x%lx)\n",
253 (unsigned long)regs.user_ip);
254
255 regs.user_ax = SYS_getpid;
256 regs.user_arg0 = 20;
257 regs.user_arg1 = 21;
258 regs.user_arg2 = 22;
259 regs.user_arg3 = 23;
260 regs.user_arg4 = 24;
261 regs.user_arg5 = 25;
262 regs.user_ip -= 2;
263
264 if (ptrace(PTRACE_SETREGS, chld, 0, ®s) != 0)
265 err(1, "PTRACE_SETREGS");
266
267 if (ptrace(PTRACE_SYSEMU, chld, 0, 0) != 0)
268 err(1, "PTRACE_SYSEMU");
269 wait_trap(chld);
270
271 if (ptrace(PTRACE_GETREGS, chld, 0, ®s) != 0)
272 err(1, "PTRACE_GETREGS");
273
274 if (regs.user_syscall_nr != SYS_getpid ||
275 regs.user_arg0 != 20 || regs.user_arg1 != 21 || regs.user_arg2 != 22 ||
276 regs.user_arg3 != 23 || regs.user_arg4 != 24 || regs.user_arg5 != 25) {
277 printf("[FAIL]\tRestart nr or args are wrong (nr=%lu, args=%lu %lu %lu %lu %lu %lu)\n", (unsigned long)regs.user_syscall_nr, (unsigned long)regs.user_arg0, (unsigned long)regs.user_arg1, (unsigned long)regs.user_arg2, (unsigned long)regs.user_arg3, (unsigned long)regs.user_arg4, (unsigned long)regs.user_arg5);
278 nerrs++;
279 } else {
280 printf("[OK]\tReplacement nr and args are correct\n");
281 }
282
283 if (ptrace(PTRACE_CONT, chld, 0, 0) != 0)
284 err(1, "PTRACE_CONT");
285 if (waitpid(chld, &status, 0) != chld)
286 err(1, "waitpid");
287 if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
288 printf("[FAIL]\tChild failed\n");
289 nerrs++;
290 } else {
291 printf("[OK]\tChild exited cleanly\n");
292 }
293 }
294
test_restart_under_ptrace(void)295 static void test_restart_under_ptrace(void)
296 {
297 printf("[RUN]\tkernel syscall restart under ptrace\n");
298 pid_t chld = fork();
299 if (chld < 0)
300 err(1, "fork");
301
302 if (chld == 0) {
303 if (ptrace(PTRACE_TRACEME, 0, 0, 0) != 0)
304 err(1, "PTRACE_TRACEME");
305
306 pid_t pid = getpid(), tid = syscall(SYS_gettid);
307
308 printf("\tChild will take a nap until signaled\n");
309 setsigign(SIGUSR1, SA_RESTART);
310 syscall(SYS_tgkill, pid, tid, SIGSTOP);
311
312 syscall(SYS_pause, 0, 0, 0, 0, 0, 0);
313 _exit(0);
314 }
315
316 int status;
317
318 /* Wait for SIGSTOP. */
319 if (waitpid(chld, &status, 0) != chld || !WIFSTOPPED(status))
320 err(1, "waitpid");
321
322 struct user_regs_struct regs;
323
324 printf("[RUN]\tSYSCALL\n");
325 if (ptrace(PTRACE_SYSCALL, chld, 0, 0) != 0)
326 err(1, "PTRACE_SYSCALL");
327 wait_trap(chld);
328
329 /* We should be stopped at pause(2) entry. */
330
331 if (ptrace(PTRACE_GETREGS, chld, 0, ®s) != 0)
332 err(1, "PTRACE_GETREGS");
333
334 if (regs.user_syscall_nr != SYS_pause ||
335 regs.user_arg0 != 0 || regs.user_arg1 != 0 ||
336 regs.user_arg2 != 0 || regs.user_arg3 != 0 ||
337 regs.user_arg4 != 0 || regs.user_arg5 != 0) {
338 printf("[FAIL]\tInitial args are wrong (nr=%lu, args=%lu %lu %lu %lu %lu %lu)\n", (unsigned long)regs.user_syscall_nr, (unsigned long)regs.user_arg0, (unsigned long)regs.user_arg1, (unsigned long)regs.user_arg2, (unsigned long)regs.user_arg3, (unsigned long)regs.user_arg4, (unsigned long)regs.user_arg5);
339 nerrs++;
340 } else {
341 printf("[OK]\tInitial nr and args are correct\n");
342 }
343
344 /* Interrupt it. */
345 kill(chld, SIGUSR1);
346
347 /* Advance. We should be stopped at exit. */
348 printf("[RUN]\tSYSCALL\n");
349 if (ptrace(PTRACE_SYSCALL, chld, 0, 0) != 0)
350 err(1, "PTRACE_SYSCALL");
351 wait_trap(chld);
352
353 if (ptrace(PTRACE_GETREGS, chld, 0, ®s) != 0)
354 err(1, "PTRACE_GETREGS");
355
356 if (regs.user_syscall_nr != SYS_pause ||
357 regs.user_arg0 != 0 || regs.user_arg1 != 0 ||
358 regs.user_arg2 != 0 || regs.user_arg3 != 0 ||
359 regs.user_arg4 != 0 || regs.user_arg5 != 0) {
360 printf("[FAIL]\tArgs after SIGUSR1 are wrong (nr=%lu, args=%lu %lu %lu %lu %lu %lu)\n", (unsigned long)regs.user_syscall_nr, (unsigned long)regs.user_arg0, (unsigned long)regs.user_arg1, (unsigned long)regs.user_arg2, (unsigned long)regs.user_arg3, (unsigned long)regs.user_arg4, (unsigned long)regs.user_arg5);
361 nerrs++;
362 } else {
363 printf("[OK]\tArgs after SIGUSR1 are correct (ax = %ld)\n",
364 (long)regs.user_ax);
365 }
366
367 /* Poke the regs back in. This must not break anything. */
368 if (ptrace(PTRACE_SETREGS, chld, 0, ®s) != 0)
369 err(1, "PTRACE_SETREGS");
370
371 /* Catch the (ignored) SIGUSR1. */
372 if (ptrace(PTRACE_CONT, chld, 0, 0) != 0)
373 err(1, "PTRACE_CONT");
374 if (waitpid(chld, &status, 0) != chld)
375 err(1, "waitpid");
376 if (!WIFSTOPPED(status)) {
377 printf("[FAIL]\tChild was stopped for SIGUSR1 (status = 0x%x)\n", status);
378 nerrs++;
379 } else {
380 printf("[OK]\tChild got SIGUSR1\n");
381 }
382
383 /* The next event should be pause(2) again. */
384 printf("[RUN]\tStep again\n");
385 if (ptrace(PTRACE_SYSCALL, chld, 0, 0) != 0)
386 err(1, "PTRACE_SYSCALL");
387 wait_trap(chld);
388
389 /* We should be stopped at pause(2) entry. */
390
391 if (ptrace(PTRACE_GETREGS, chld, 0, ®s) != 0)
392 err(1, "PTRACE_GETREGS");
393
394 if (regs.user_syscall_nr != SYS_pause ||
395 regs.user_arg0 != 0 || regs.user_arg1 != 0 ||
396 regs.user_arg2 != 0 || regs.user_arg3 != 0 ||
397 regs.user_arg4 != 0 || regs.user_arg5 != 0) {
398 printf("[FAIL]\tpause did not restart (nr=%lu, args=%lu %lu %lu %lu %lu %lu)\n", (unsigned long)regs.user_syscall_nr, (unsigned long)regs.user_arg0, (unsigned long)regs.user_arg1, (unsigned long)regs.user_arg2, (unsigned long)regs.user_arg3, (unsigned long)regs.user_arg4, (unsigned long)regs.user_arg5);
399 nerrs++;
400 } else {
401 printf("[OK]\tpause(2) restarted correctly\n");
402 }
403
404 /* Kill it. */
405 kill(chld, SIGKILL);
406 if (waitpid(chld, &status, 0) != chld)
407 err(1, "waitpid");
408 }
409
main()410 int main()
411 {
412 printf("[RUN]\tCheck int80 return regs\n");
413 test_sys32_regs(do_full_int80);
414
415 #if defined(__i386__) && (!defined(__GLIBC__) || __GLIBC__ > 2 || __GLIBC_MINOR__ >= 16)
416 vsyscall32 = (void *)getauxval(AT_SYSINFO);
417 if (vsyscall32) {
418 printf("[RUN]\tCheck AT_SYSINFO return regs\n");
419 test_sys32_regs(do_full_vsyscall32);
420 } else {
421 printf("[SKIP]\tAT_SYSINFO is not available\n");
422 }
423 #endif
424
425 test_ptrace_syscall_restart();
426
427 test_restart_under_ptrace();
428
429 return 0;
430 }
431