/arch/um/kernel/process.c

  1/* 
  2 * Copyright (C) 2000, 2001, 2002 Jeff Dike (jdike@karaya.com)
  3 * Licensed under the GPL
  4 */
  5
  6#include <stdio.h>
  7#include <unistd.h>
  8#include <signal.h>
  9#include <sched.h>
 10#include <errno.h>
 11#include <stdarg.h>
 12#include <stdlib.h>
 13#include <setjmp.h>
 14#include <sys/time.h>
 15#include <sys/wait.h>
 16#include <sys/mman.h>
 17#include <asm/unistd.h>
 18#include <asm/page.h>
 19#include "user_util.h"
 20#include "kern_util.h"
 21#include "user.h"
 22#include "process.h"
 23#include "signal_kern.h"
 24#include "signal_user.h"
 25#include "sysdep/ptrace.h"
 26#include "sysdep/sigcontext.h"
 27#include "irq_user.h"
 28#include "ptrace_user.h"
 29#include "time_user.h"
 30#include "init.h"
 31#include "os.h"
 32#include "uml-config.h"
 33#include "ptrace_user.h"
 34#include "choose-mode.h"
 35#include "mode.h"
 36#ifdef UML_CONFIG_MODE_SKAS
 37#include "skas.h"
 38#include "skas_ptrace.h"
 39#include "registers.h"
 40#endif
 41
 42void init_new_thread_stack(void *sig_stack, void (*usr1_handler)(int))
 43{
 44	int flags = 0, pages;
 45
 46	if(sig_stack != NULL){
 47		pages = (1 << UML_CONFIG_KERNEL_STACK_ORDER);
 48		set_sigstack(sig_stack, pages * page_size());
 49		flags = SA_ONSTACK;
 50	}
 51	if(usr1_handler) set_handler(SIGUSR1, usr1_handler, flags, -1);
 52}
 53
 54void init_new_thread_signals(int altstack)
 55{
 56	int flags = altstack ? SA_ONSTACK : 0;
 57
 58	set_handler(SIGSEGV, (__sighandler_t) sig_handler, flags,
 59		    SIGUSR1, SIGIO, SIGWINCH, SIGALRM, SIGVTALRM, -1);
 60	set_handler(SIGTRAP, (__sighandler_t) sig_handler, flags, 
 61		    SIGUSR1, SIGIO, SIGWINCH, SIGALRM, SIGVTALRM, -1);
 62	set_handler(SIGFPE, (__sighandler_t) sig_handler, flags, 
 63		    SIGUSR1, SIGIO, SIGWINCH, SIGALRM, SIGVTALRM, -1);
 64	set_handler(SIGILL, (__sighandler_t) sig_handler, flags, 
 65		    SIGUSR1, SIGIO, SIGWINCH, SIGALRM, SIGVTALRM, -1);
 66	set_handler(SIGBUS, (__sighandler_t) sig_handler, flags, 
 67		    SIGUSR1, SIGIO, SIGWINCH, SIGALRM, SIGVTALRM, -1);
 68	set_handler(SIGWINCH, (__sighandler_t) sig_handler, flags, 
 69		    SIGUSR1, SIGIO, SIGWINCH, SIGALRM, SIGVTALRM, -1);
 70	set_handler(SIGUSR2, (__sighandler_t) sig_handler, 
 71		    flags, SIGUSR1, SIGIO, SIGWINCH, SIGALRM, SIGVTALRM, -1);
 72	signal(SIGHUP, SIG_IGN);
 73
 74	init_irq_signals(altstack);
 75}
 76
 77struct tramp {
 78	int (*tramp)(void *);
 79	void *tramp_data;
 80	unsigned long temp_stack;
 81	int flags;
 82	int pid;
 83};
 84
 85/* See above for why sigkill is here */
 86
 87int sigkill = SIGKILL;
 88
 89int outer_tramp(void *arg)
 90{
 91	struct tramp *t;
 92	int sig = sigkill;
 93
 94	t = arg;
 95	t->pid = clone(t->tramp, (void *) t->temp_stack + page_size()/2,
 96		       t->flags, t->tramp_data);
 97	if(t->pid > 0) wait_for_stop(t->pid, SIGSTOP, PTRACE_CONT, NULL);
 98	kill(os_getpid(), sig);
 99	_exit(0);
100}
101
102int start_fork_tramp(void *thread_arg, unsigned long temp_stack, 
103		     int clone_flags, int (*tramp)(void *))
104{
105	struct tramp arg;
106	unsigned long sp;
107	int new_pid, status, err;
108
109	/* The trampoline will run on the temporary stack */
110	sp = stack_sp(temp_stack);
111
112	clone_flags |= CLONE_FILES | SIGCHLD;
113
114	arg.tramp = tramp;
115	arg.tramp_data = thread_arg;
116	arg.temp_stack = temp_stack;
117	arg.flags = clone_flags;
118
119	/* Start the process and wait for it to kill itself */
120	new_pid = clone(outer_tramp, (void *) sp, clone_flags, &arg);
121	if(new_pid < 0)
122		return(new_pid);
123
124	CATCH_EINTR(err = waitpid(new_pid, &status, 0));
125	if(err < 0)
126		panic("Waiting for outer trampoline failed - errno = %d",
127		      errno);
128
129	if(!WIFSIGNALED(status) || (WTERMSIG(status) != SIGKILL))
130		panic("outer trampoline didn't exit with SIGKILL, "
131		      "status = %d", status);
132
133	return(arg.pid);
134}
135
136static int ptrace_child(void *arg)
137{
138	int ret;
139	int pid = os_getpid(), ppid = getppid();
140	int sc_result;
141
142	if(ptrace(PTRACE_TRACEME, 0, 0, 0) < 0){
143		perror("ptrace");
144		os_kill_process(pid, 0);
145	}
146	os_stop_process(pid);
147
148	/*This syscall will be intercepted by the parent. Don't call more than
149	 * once, please.*/
150	sc_result = os_getpid();
151
152	if (sc_result == pid)
153		ret = 1; /*Nothing modified by the parent, we are running
154			   normally.*/
155	else if (sc_result == ppid)
156		ret = 0; /*Expected in check_ptrace and check_sysemu when they
157			   succeed in modifying the stack frame*/
158	else
159		ret = 2; /*Serious trouble! This could be caused by a bug in
160			   host 2.6 SKAS3/2.6 patch before release -V6, together
161			   with a bug in the UML code itself.*/
162	_exit(ret);
163}
164
165static int start_ptraced_child(void **stack_out)
166{
167	void *stack;
168	unsigned long sp;
169	int pid, n, status;
170	
171	stack = mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC,
172		     MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
173	if(stack == MAP_FAILED)
174		panic("check_ptrace : mmap failed, errno = %d", errno);
175	sp = (unsigned long) stack + PAGE_SIZE - sizeof(void *);
176	pid = clone(ptrace_child, (void *) sp, SIGCHLD, NULL);
177	if(pid < 0)
178		panic("check_ptrace : clone failed, errno = %d", errno);
179	CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
180	if(n < 0)
181		panic("check_ptrace : wait failed, errno = %d", errno);
182	if(!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP))
183		panic("check_ptrace : expected SIGSTOP, got status = %d",
184		      status);
185
186	*stack_out = stack;
187	return(pid);
188}
189
190/* When testing for SYSEMU support, if it is one of the broken versions, we must
191 * just avoid using sysemu, not panic, but only if SYSEMU features are broken.
192 * So only for SYSEMU features we test mustpanic, while normal host features
193 * must work anyway!*/
194static int stop_ptraced_child(int pid, void *stack, int exitcode, int mustpanic)
195{
196	int status, n, ret = 0;
197
198	if(ptrace(PTRACE_CONT, pid, 0, 0) < 0)
199		panic("check_ptrace : ptrace failed, errno = %d", errno);
200	CATCH_EINTR(n = waitpid(pid, &status, 0));
201	if(!WIFEXITED(status) || (WEXITSTATUS(status) != exitcode)) {
202		int exit_with = WEXITSTATUS(status);
203		if (exit_with == 2)
204			printk("check_ptrace : child exited with status 2. "
205			       "Serious trouble happening! Try updating your "
206			       "host skas patch!\nDisabling SYSEMU support.");
207		printk("check_ptrace : child exited with exitcode %d, while "
208		      "expecting %d; status 0x%x", exit_with,
209		      exitcode, status);
210		if (mustpanic)
211			panic("\n");
212		else
213			printk("\n");
214		ret = -1;
215	}
216
217	if(munmap(stack, PAGE_SIZE) < 0)
218		panic("check_ptrace : munmap failed, errno = %d", errno);
219	return ret;
220}
221
222static int force_sysemu_disabled = 0;
223
224static int __init nosysemu_cmd_param(char *str, int* add)
225{
226	force_sysemu_disabled = 1;
227	return 0;
228}
229
230__uml_setup("nosysemu", nosysemu_cmd_param,
231		"nosysemu\n"
232		"    Turns off syscall emulation patch for ptrace (SYSEMU) on.\n"
233		"    SYSEMU is a performance-patch introduced by Laurent Vivier. It changes\n"
234		"    behaviour of ptrace() and helps reducing host context switch rate.\n"
235		"    To make it working, you need a kernel patch for your host, too.\n"
236		"    See http://perso.wanadoo.fr/laurent.vivier/UML/ for further information.\n\n");
237
238static void __init check_sysemu(void)
239{
240	void *stack;
241	int pid, syscall, n, status, count=0;
242
243	printk("Checking syscall emulation patch for ptrace...");
244	sysemu_supported = 0;
245	pid = start_ptraced_child(&stack);
246
247	if(ptrace(PTRACE_SYSEMU, pid, 0, 0) < 0)
248		goto fail;
249
250	CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
251	if (n < 0)
252		panic("check_sysemu : wait failed, errno = %d", errno);
253	if(!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGTRAP))
254		panic("check_sysemu : expected SIGTRAP, "
255		      "got status = %d", status);
256
257	n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_RET_OFFSET,
258		   os_getpid());
259	if(n < 0)
260		panic("check_sysemu : failed to modify system "
261		      "call return, errno = %d", errno);
262
263	if (stop_ptraced_child(pid, stack, 0, 0) < 0)
264		goto fail_stopped;
265
266	sysemu_supported = 1;
267	printk("OK\n");
268	set_using_sysemu(!force_sysemu_disabled);
269
270	printk("Checking advanced syscall emulation patch for ptrace...");
271	pid = start_ptraced_child(&stack);
272	while(1){
273		count++;
274		if(ptrace(PTRACE_SYSEMU_SINGLESTEP, pid, 0, 0) < 0)
275			goto fail;
276		CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
277		if(n < 0)
278			panic("check_ptrace : wait failed, errno = %d", errno);
279		if(!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGTRAP))
280			panic("check_ptrace : expected (SIGTRAP|SYSCALL_TRAP), "
281			      "got status = %d", status);
282
283		syscall = ptrace(PTRACE_PEEKUSR, pid, PT_SYSCALL_NR_OFFSET,
284				 0);
285		if(syscall == __NR_getpid){
286			if (!count)
287				panic("check_ptrace : SYSEMU_SINGLESTEP doesn't singlestep");
288			n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_RET_OFFSET,
289				   os_getpid());
290			if(n < 0)
291				panic("check_sysemu : failed to modify system "
292				      "call return, errno = %d", errno);
293			break;
294		}
295	}
296	if (stop_ptraced_child(pid, stack, 0, 0) < 0)
297		goto fail_stopped;
298
299	sysemu_supported = 2;
300	printk("OK\n");
301
302	if ( !force_sysemu_disabled )
303		set_using_sysemu(sysemu_supported);
304	return;
305
306fail:
307	stop_ptraced_child(pid, stack, 1, 0);
308fail_stopped:
309	printk("missing\n");
310}
311
312void __init check_ptrace(void)
313{
314	void *stack;
315	int pid, syscall, n, status;
316
317	printk("Checking that ptrace can change system call numbers...");
318	pid = start_ptraced_child(&stack);
319
320	if (ptrace(PTRACE_OLDSETOPTIONS, pid, 0, (void *)PTRACE_O_TRACESYSGOOD) < 0)
321		panic("check_ptrace: PTRACE_SETOPTIONS failed, errno = %d", errno);
322
323	while(1){
324		if(ptrace(PTRACE_SYSCALL, pid, 0, 0) < 0)
325			panic("check_ptrace : ptrace failed, errno = %d", 
326			      errno);
327		CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
328		if(n < 0)
329			panic("check_ptrace : wait failed, errno = %d", errno);
330		if(!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGTRAP + 0x80))
331			panic("check_ptrace : expected SIGTRAP + 0x80, "
332			      "got status = %d", status);
333		
334		syscall = ptrace(PTRACE_PEEKUSR, pid, PT_SYSCALL_NR_OFFSET,
335				 0);
336		if(syscall == __NR_getpid){
337			n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_NR_OFFSET,
338				   __NR_getppid);
339			if(n < 0)
340				panic("check_ptrace : failed to modify system "
341				      "call, errno = %d", errno);
342			break;
343		}
344	}
345	stop_ptraced_child(pid, stack, 0, 1);
346	printk("OK\n");
347	check_sysemu();
348}
349
350int run_kernel_thread(int (*fn)(void *), void *arg, void **jmp_ptr)
351{
352	sigjmp_buf buf;
353	int n;
354
355	*jmp_ptr = &buf;
356	n = sigsetjmp(buf, 1);
357	if(n != 0)
358		return(n);
359	(*fn)(arg);
360	return(0);
361}
362
363void forward_pending_sigio(int target)
364{
365	sigset_t sigs;
366
367	if(sigpending(&sigs)) 
368		panic("forward_pending_sigio : sigpending failed");
369	if(sigismember(&sigs, SIGIO))
370		kill(target, SIGIO);
371}
372
373#ifdef UML_CONFIG_MODE_SKAS
374static inline int check_skas3_ptrace_support(void)
375{
376	struct ptrace_faultinfo fi;
377	void *stack;
378	int pid, n, ret = 1;
379
380	printf("Checking for the skas3 patch in the host...");
381	pid = start_ptraced_child(&stack);
382
383	n = ptrace(PTRACE_FAULTINFO, pid, 0, &fi);
384	if (n < 0) {
385		if(errno == EIO)
386			printf("not found\n");
387		else {
388			perror("not found");
389		}
390		ret = 0;
391	} else {
392		printf("found\n");
393	}
394
395	init_registers(pid);
396	stop_ptraced_child(pid, stack, 1, 1);
397
398	return(ret);
399}
400
401int can_do_skas(void)
402{
403	int ret = 1;
404
405	printf("Checking for /proc/mm...");
406	if (os_access("/proc/mm", OS_ACC_W_OK) < 0) {
407		printf("not found\n");
408		ret = 0;
409		goto out;
410	} else {
411		printf("found\n");
412	}
413
414	ret = check_skas3_ptrace_support();
415out:
416	return ret;
417}
418#else
419int can_do_skas(void)
420{
421	return(0);
422}
423#endif