Linux Audio

Check our new training course

Embedded Linux Audio

Check our new training course
with Creative Commons CC-BY-SA
lecture materials

Bootlin logo

Elixir Cross Referencer

Loading...
  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
// SPDX-License-Identifier: GPL-2.0
#define _GNU_SOURCE

#include <sys/ptrace.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/syscall.h>
#include <sys/user.h>
#include <unistd.h>
#include <errno.h>
#include <stddef.h>
#include <stdio.h>
#include <err.h>
#include <string.h>
#include <asm/ptrace-abi.h>
#include <sys/auxv.h>

/* Bitness-agnostic defines for user_regs_struct fields. */
#ifdef __x86_64__
# define user_syscall_nr	orig_rax
# define user_arg0		rdi
# define user_arg1		rsi
# define user_arg2		rdx
# define user_arg3		r10
# define user_arg4		r8
# define user_arg5		r9
# define user_ip		rip
# define user_ax		rax
#else
# define user_syscall_nr	orig_eax
# define user_arg0		ebx
# define user_arg1		ecx
# define user_arg2		edx
# define user_arg3		esi
# define user_arg4		edi
# define user_arg5		ebp
# define user_ip		eip
# define user_ax		eax
#endif

static int nerrs = 0;

struct syscall_args32 {
	uint32_t nr, arg0, arg1, arg2, arg3, arg4, arg5;
};

#ifdef __i386__
extern void sys32_helper(struct syscall_args32 *, void *);
extern void int80_and_ret(void);
#endif

/*
 * Helper to invoke int80 with controlled regs and capture the final regs.
 */
static void do_full_int80(struct syscall_args32 *args)
{
#ifdef __x86_64__
	register unsigned long bp asm("bp") = args->arg5;
	asm volatile ("int $0x80"
		      : "+a" (args->nr),
			"+b" (args->arg0), "+c" (args->arg1), "+d" (args->arg2),
			"+S" (args->arg3), "+D" (args->arg4), "+r" (bp)
			: : "r8", "r9", "r10", "r11");
	args->arg5 = bp;
#else
	sys32_helper(args, int80_and_ret);
#endif
}

#ifdef __i386__
static void (*vsyscall32)(void);

/*
 * Nasty helper to invoke AT_SYSINFO (i.e. __kernel_vsyscall) with
 * controlled regs and capture the final regs.  This is so nasty that it
 * crashes my copy of gdb :)
 */
static void do_full_vsyscall32(struct syscall_args32 *args)
{
	sys32_helper(args, vsyscall32);
}
#endif

static siginfo_t wait_trap(pid_t chld)
{
	siginfo_t si;
	if (waitid(P_PID, chld, &si, WEXITED|WSTOPPED) != 0)
		err(1, "waitid");
	if (si.si_pid != chld)
		errx(1, "got unexpected pid in event\n");
	if (si.si_code != CLD_TRAPPED)
		errx(1, "got unexpected event type %d\n", si.si_code);
	return si;
}

static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
		       int flags)
{
	struct sigaction sa;
	memset(&sa, 0, sizeof(sa));
	sa.sa_sigaction = handler;
	sa.sa_flags = SA_SIGINFO | flags;
	sigemptyset(&sa.sa_mask);
	if (sigaction(sig, &sa, 0))
		err(1, "sigaction");
}

static void setsigign(int sig, int flags)
{
	struct sigaction sa;
	memset(&sa, 0, sizeof(sa));
	sa.sa_sigaction = (void *)SIG_IGN;
	sa.sa_flags = flags;
	sigemptyset(&sa.sa_mask);
	if (sigaction(sig, &sa, 0))
		err(1, "sigaction");
}

static void clearhandler(int sig)
{
	struct sigaction sa;
	memset(&sa, 0, sizeof(sa));
	sa.sa_handler = SIG_DFL;
	sigemptyset(&sa.sa_mask);
	if (sigaction(sig, &sa, 0))
		err(1, "sigaction");
}

#ifdef __x86_64__
# define REG_BP REG_RBP
#else
# define REG_BP REG_EBP
#endif

static void empty_handler(int sig, siginfo_t *si, void *ctx_void)
{
}

static void test_sys32_regs(void (*do_syscall)(struct syscall_args32 *))
{
	struct syscall_args32 args = {
		.nr = 224,	/* gettid */
		.arg0 = 10, .arg1 = 11, .arg2 = 12,
		.arg3 = 13, .arg4 = 14, .arg5 = 15,
	};

	do_syscall(&args);

	if (args.nr != getpid() ||
	    args.arg0 != 10 || args.arg1 != 11 || args.arg2 != 12 ||
	    args.arg3 != 13 || args.arg4 != 14 || args.arg5 != 15) {
		printf("[FAIL]\tgetpid() failed to preserve regs\n");
		nerrs++;
	} else {
		printf("[OK]\tgetpid() preserves regs\n");
	}

	sethandler(SIGUSR1, empty_handler, 0);

	args.nr = 37;	/* kill */
	args.arg0 = getpid();
	args.arg1 = SIGUSR1;
	do_syscall(&args);
	if (args.nr != 0 ||
	    args.arg0 != getpid() || args.arg1 != SIGUSR1 || args.arg2 != 12 ||
	    args.arg3 != 13 || args.arg4 != 14 || args.arg5 != 15) {
		printf("[FAIL]\tkill(getpid(), SIGUSR1) failed to preserve regs\n");
		nerrs++;
	} else {
		printf("[OK]\tkill(getpid(), SIGUSR1) preserves regs\n");
	}
	clearhandler(SIGUSR1);
}

static void test_ptrace_syscall_restart(void)
{
	printf("[RUN]\tptrace-induced syscall restart\n");
	pid_t chld = fork();
	if (chld < 0)
		err(1, "fork");

	if (chld == 0) {
		if (ptrace(PTRACE_TRACEME, 0, 0, 0) != 0)
			err(1, "PTRACE_TRACEME");

		pid_t pid = getpid(), tid = syscall(SYS_gettid);

		printf("\tChild will make one syscall\n");
		syscall(SYS_tgkill, pid, tid, SIGSTOP);

		syscall(SYS_gettid, 10, 11, 12, 13, 14, 15);
		_exit(0);
	}

	int status;

	/* Wait for SIGSTOP. */
	if (waitpid(chld, &status, 0) != chld || !WIFSTOPPED(status))
		err(1, "waitpid");

	struct user_regs_struct regs;

	printf("[RUN]\tSYSEMU\n");
	if (ptrace(PTRACE_SYSEMU, chld, 0, 0) != 0)
		err(1, "PTRACE_SYSEMU");
	wait_trap(chld);

	if (ptrace(PTRACE_GETREGS, chld, 0, &regs) != 0)
		err(1, "PTRACE_GETREGS");

	if (regs.user_syscall_nr != SYS_gettid ||
	    regs.user_arg0 != 10 || regs.user_arg1 != 11 ||
	    regs.user_arg2 != 12 || regs.user_arg3 != 13 ||
	    regs.user_arg4 != 14 || regs.user_arg5 != 15) {
		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);
		nerrs++;
	} else {
		printf("[OK]\tInitial nr and args are correct\n");
	}

	printf("[RUN]\tRestart the syscall (ip = 0x%lx)\n",
	       (unsigned long)regs.user_ip);

	/*
	 * This does exactly what it appears to do if syscall is int80 or
	 * SYSCALL64.  For SYSCALL32 or SYSENTER, though, this is highly
	 * magical.  It needs to work so that ptrace and syscall restart
	 * work as expected.
	 */
	regs.user_ax = regs.user_syscall_nr;
	regs.user_ip -= 2;
	if (ptrace(PTRACE_SETREGS, chld, 0, &regs) != 0)
		err(1, "PTRACE_SETREGS");

	if (ptrace(PTRACE_SYSEMU, chld, 0, 0) != 0)
		err(1, "PTRACE_SYSEMU");
	wait_trap(chld);

	if (ptrace(PTRACE_GETREGS, chld, 0, &regs) != 0)
		err(1, "PTRACE_GETREGS");

	if (regs.user_syscall_nr != SYS_gettid ||
	    regs.user_arg0 != 10 || regs.user_arg1 != 11 ||
	    regs.user_arg2 != 12 || regs.user_arg3 != 13 ||
	    regs.user_arg4 != 14 || regs.user_arg5 != 15) {
		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);
		nerrs++;
	} else {
		printf("[OK]\tRestarted nr and args are correct\n");
	}

	printf("[RUN]\tChange nr and args and restart the syscall (ip = 0x%lx)\n",
	       (unsigned long)regs.user_ip);

	regs.user_ax = SYS_getpid;
	regs.user_arg0 = 20;
	regs.user_arg1 = 21;
	regs.user_arg2 = 22;
	regs.user_arg3 = 23;
	regs.user_arg4 = 24;
	regs.user_arg5 = 25;
	regs.user_ip -= 2;

	if (ptrace(PTRACE_SETREGS, chld, 0, &regs) != 0)
		err(1, "PTRACE_SETREGS");

	if (ptrace(PTRACE_SYSEMU, chld, 0, 0) != 0)
		err(1, "PTRACE_SYSEMU");
	wait_trap(chld);

	if (ptrace(PTRACE_GETREGS, chld, 0, &regs) != 0)
		err(1, "PTRACE_GETREGS");

	if (regs.user_syscall_nr != SYS_getpid ||
	    regs.user_arg0 != 20 || regs.user_arg1 != 21 || regs.user_arg2 != 22 ||
	    regs.user_arg3 != 23 || regs.user_arg4 != 24 || regs.user_arg5 != 25) {
		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);
		nerrs++;
	} else {
		printf("[OK]\tReplacement nr and args are correct\n");
	}

	if (ptrace(PTRACE_CONT, chld, 0, 0) != 0)
		err(1, "PTRACE_CONT");
	if (waitpid(chld, &status, 0) != chld)
		err(1, "waitpid");
	if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
		printf("[FAIL]\tChild failed\n");
		nerrs++;
	} else {
		printf("[OK]\tChild exited cleanly\n");
	}
}

static void test_restart_under_ptrace(void)
{
	printf("[RUN]\tkernel syscall restart under ptrace\n");
	pid_t chld = fork();
	if (chld < 0)
		err(1, "fork");

	if (chld == 0) {
		if (ptrace(PTRACE_TRACEME, 0, 0, 0) != 0)
			err(1, "PTRACE_TRACEME");

		pid_t pid = getpid(), tid = syscall(SYS_gettid);

		printf("\tChild will take a nap until signaled\n");
		setsigign(SIGUSR1, SA_RESTART);
		syscall(SYS_tgkill, pid, tid, SIGSTOP);

		syscall(SYS_pause, 0, 0, 0, 0, 0, 0);
		_exit(0);
	}

	int status;

	/* Wait for SIGSTOP. */
	if (waitpid(chld, &status, 0) != chld || !WIFSTOPPED(status))
		err(1, "waitpid");

	struct user_regs_struct regs;

	printf("[RUN]\tSYSCALL\n");
	if (ptrace(PTRACE_SYSCALL, chld, 0, 0) != 0)
		err(1, "PTRACE_SYSCALL");
	wait_trap(chld);

	/* We should be stopped at pause(2) entry. */

	if (ptrace(PTRACE_GETREGS, chld, 0, &regs) != 0)
		err(1, "PTRACE_GETREGS");

	if (regs.user_syscall_nr != SYS_pause ||
	    regs.user_arg0 != 0 || regs.user_arg1 != 0 ||
	    regs.user_arg2 != 0 || regs.user_arg3 != 0 ||
	    regs.user_arg4 != 0 || regs.user_arg5 != 0) {
		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);
		nerrs++;
	} else {
		printf("[OK]\tInitial nr and args are correct\n");
	}

	/* Interrupt it. */
	kill(chld, SIGUSR1);

	/* Advance.  We should be stopped at exit. */
	printf("[RUN]\tSYSCALL\n");
	if (ptrace(PTRACE_SYSCALL, chld, 0, 0) != 0)
		err(1, "PTRACE_SYSCALL");
	wait_trap(chld);

	if (ptrace(PTRACE_GETREGS, chld, 0, &regs) != 0)
		err(1, "PTRACE_GETREGS");

	if (regs.user_syscall_nr != SYS_pause ||
	    regs.user_arg0 != 0 || regs.user_arg1 != 0 ||
	    regs.user_arg2 != 0 || regs.user_arg3 != 0 ||
	    regs.user_arg4 != 0 || regs.user_arg5 != 0) {
		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);
		nerrs++;
	} else {
		printf("[OK]\tArgs after SIGUSR1 are correct (ax = %ld)\n",
		       (long)regs.user_ax);
	}

	/* Poke the regs back in.  This must not break anything. */
	if (ptrace(PTRACE_SETREGS, chld, 0, &regs) != 0)
		err(1, "PTRACE_SETREGS");

	/* Catch the (ignored) SIGUSR1. */
	if (ptrace(PTRACE_CONT, chld, 0, 0) != 0)
		err(1, "PTRACE_CONT");
	if (waitpid(chld, &status, 0) != chld)
		err(1, "waitpid");
	if (!WIFSTOPPED(status)) {
		printf("[FAIL]\tChild was stopped for SIGUSR1 (status = 0x%x)\n", status);
		nerrs++;
	} else {
		printf("[OK]\tChild got SIGUSR1\n");
	}

	/* The next event should be pause(2) again. */
	printf("[RUN]\tStep again\n");
	if (ptrace(PTRACE_SYSCALL, chld, 0, 0) != 0)
		err(1, "PTRACE_SYSCALL");
	wait_trap(chld);

	/* We should be stopped at pause(2) entry. */

	if (ptrace(PTRACE_GETREGS, chld, 0, &regs) != 0)
		err(1, "PTRACE_GETREGS");

	if (regs.user_syscall_nr != SYS_pause ||
	    regs.user_arg0 != 0 || regs.user_arg1 != 0 ||
	    regs.user_arg2 != 0 || regs.user_arg3 != 0 ||
	    regs.user_arg4 != 0 || regs.user_arg5 != 0) {
		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);
		nerrs++;
	} else {
		printf("[OK]\tpause(2) restarted correctly\n");
	}

	/* Kill it. */
	kill(chld, SIGKILL);
	if (waitpid(chld, &status, 0) != chld)
		err(1, "waitpid");
}

int main()
{
	printf("[RUN]\tCheck int80 return regs\n");
	test_sys32_regs(do_full_int80);

#if defined(__i386__) && (!defined(__GLIBC__) || __GLIBC__ > 2 || __GLIBC_MINOR__ >= 16)
	vsyscall32 = (void *)getauxval(AT_SYSINFO);
	if (vsyscall32) {
		printf("[RUN]\tCheck AT_SYSINFO return regs\n");
		test_sys32_regs(do_full_vsyscall32);
	} else {
		printf("[SKIP]\tAT_SYSINFO is not available\n");
	}
#endif

	test_ptrace_syscall_restart();

	test_restart_under_ptrace();

	return 0;
}