xref: /linux/tools/testing/selftests/x86/ptrace_syscall.c (revision ead5d1f4d877e92c051e1a1ade623d0d30e71619)
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, &regs) != 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, &regs) != 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, &regs) != 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, &regs) != 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, &regs) != 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, &regs) != 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, &regs) != 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, &regs) != 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, &regs) != 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