Merge master.kernel.org:/home/rmk/linux-2.6-arm
[linux-2.6] / arch / um / os-Linux / start_up.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 "signal_kern.h"
23 #include "signal_user.h"
24 #include "sysdep/ptrace.h"
25 #include "sysdep/sigcontext.h"
26 #include "irq_user.h"
27 #include "ptrace_user.h"
28 #include "time_user.h"
29 #include "init.h"
30 #include "os.h"
31 #include "uml-config.h"
32 #include "choose-mode.h"
33 #include "mode.h"
34 #include "tempfile.h"
35 #ifdef UML_CONFIG_MODE_SKAS
36 #include "skas.h"
37 #include "skas_ptrace.h"
38 #include "registers.h"
39 #endif
40
41 static int ptrace_child(void *arg)
42 {
43         int ret;
44         int pid = os_getpid(), ppid = getppid();
45         int sc_result;
46
47         if(ptrace(PTRACE_TRACEME, 0, 0, 0) < 0){
48                 perror("ptrace");
49                 os_kill_process(pid, 0);
50         }
51         os_stop_process(pid);
52
53         /*This syscall will be intercepted by the parent. Don't call more than
54          * once, please.*/
55         sc_result = os_getpid();
56
57         if (sc_result == pid)
58                 ret = 1; /*Nothing modified by the parent, we are running
59                            normally.*/
60         else if (sc_result == ppid)
61                 ret = 0; /*Expected in check_ptrace and check_sysemu when they
62                            succeed in modifying the stack frame*/
63         else
64                 ret = 2; /*Serious trouble! This could be caused by a bug in
65                            host 2.6 SKAS3/2.6 patch before release -V6, together
66                            with a bug in the UML code itself.*/
67         _exit(ret);
68 }
69
70 static int start_ptraced_child(void **stack_out)
71 {
72         void *stack;
73         unsigned long sp;
74         int pid, n, status;
75
76         stack = mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC,
77                      MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
78         if(stack == MAP_FAILED)
79                 panic("check_ptrace : mmap failed, errno = %d", errno);
80         sp = (unsigned long) stack + PAGE_SIZE - sizeof(void *);
81         pid = clone(ptrace_child, (void *) sp, SIGCHLD, NULL);
82         if(pid < 0)
83                 panic("start_ptraced_child : clone failed, errno = %d", errno);
84         CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
85         if(n < 0)
86                 panic("check_ptrace : clone failed, errno = %d", errno);
87         if(!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP))
88                 panic("check_ptrace : expected SIGSTOP, got status = %d",
89                       status);
90
91         *stack_out = stack;
92         return(pid);
93 }
94
95 /* When testing for SYSEMU support, if it is one of the broken versions, we
96  * must just avoid using sysemu, not panic, but only if SYSEMU features are
97  * broken.
98  * So only for SYSEMU features we test mustpanic, while normal host features
99  * must work anyway!
100  */
101 static int stop_ptraced_child(int pid, void *stack, int exitcode,
102                               int mustpanic)
103 {
104         int status, n, ret = 0;
105
106         if(ptrace(PTRACE_CONT, pid, 0, 0) < 0)
107                 panic("check_ptrace : ptrace failed, errno = %d", errno);
108         CATCH_EINTR(n = waitpid(pid, &status, 0));
109         if(!WIFEXITED(status) || (WEXITSTATUS(status) != exitcode)) {
110                 int exit_with = WEXITSTATUS(status);
111                 if (exit_with == 2)
112                         printk("check_ptrace : child exited with status 2. "
113                                "Serious trouble happening! Try updating your "
114                                "host skas patch!\nDisabling SYSEMU support.");
115                 printk("check_ptrace : child exited with exitcode %d, while "
116                       "expecting %d; status 0x%x", exit_with,
117                       exitcode, status);
118                 if (mustpanic)
119                         panic("\n");
120                 else
121                         printk("\n");
122                 ret = -1;
123         }
124
125         if(munmap(stack, PAGE_SIZE) < 0)
126                 panic("check_ptrace : munmap failed, errno = %d", errno);
127         return ret;
128 }
129
130 int ptrace_faultinfo = 1;
131 int proc_mm = 1;
132
133 static int __init skas0_cmd_param(char *str, int* add)
134 {
135         ptrace_faultinfo = proc_mm = 0;
136         return 0;
137 }
138
139 __uml_setup("skas0", skas0_cmd_param,
140                 "skas0\n"
141                 "    Disables SKAS3 usage, so that SKAS0 is used, unless \n"
142                 "    you specify mode=tt.\n\n");
143
144 static int force_sysemu_disabled = 0;
145
146 static int __init nosysemu_cmd_param(char *str, int* add)
147 {
148         force_sysemu_disabled = 1;
149         return 0;
150 }
151
152 __uml_setup("nosysemu", nosysemu_cmd_param,
153 "nosysemu\n"
154 "    Turns off syscall emulation patch for ptrace (SYSEMU) on.\n"
155 "    SYSEMU is a performance-patch introduced by Laurent Vivier. It changes\n"
156 "    behaviour of ptrace() and helps reducing host context switch rate.\n"
157 "    To make it working, you need a kernel patch for your host, too.\n"
158 "    See http://perso.wanadoo.fr/laurent.vivier/UML/ for further \n"
159 "    information.\n\n");
160
161 static void __init check_sysemu(void)
162 {
163         void *stack;
164         int pid, n, status, count=0;
165
166         printk("Checking syscall emulation patch for ptrace...");
167         sysemu_supported = 0;
168         pid = start_ptraced_child(&stack);
169
170         if(ptrace(PTRACE_SYSEMU, pid, 0, 0) < 0)
171                 goto fail;
172
173         CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
174         if (n < 0)
175                 panic("check_sysemu : wait failed, errno = %d", errno);
176         if(!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGTRAP))
177                 panic("check_sysemu : expected SIGTRAP, "
178                       "got status = %d", status);
179
180         n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_RET_OFFSET,
181                    os_getpid());
182         if(n < 0)
183                 panic("check_sysemu : failed to modify system "
184                       "call return, errno = %d", errno);
185
186         if (stop_ptraced_child(pid, stack, 0, 0) < 0)
187                 goto fail_stopped;
188
189         sysemu_supported = 1;
190         printk("OK\n");
191         set_using_sysemu(!force_sysemu_disabled);
192
193         printk("Checking advanced syscall emulation patch for ptrace...");
194         pid = start_ptraced_child(&stack);
195
196         if(ptrace(PTRACE_OLDSETOPTIONS, pid, 0,
197                   (void *) PTRACE_O_TRACESYSGOOD) < 0)
198                 panic("check_ptrace: PTRACE_OLDSETOPTIONS failed, errno = %d",
199                       errno);
200
201         while(1){
202                 count++;
203                 if(ptrace(PTRACE_SYSEMU_SINGLESTEP, pid, 0, 0) < 0)
204                         goto fail;
205                 CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
206                 if(n < 0)
207                         panic("check_ptrace : wait failed, errno = %d", errno);
208                 if(WIFSTOPPED(status) && (WSTOPSIG(status) == (SIGTRAP|0x80))){
209                         if (!count)
210                                 panic("check_ptrace : SYSEMU_SINGLESTEP "
211                                       "doesn't singlestep");
212                         n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_RET_OFFSET,
213                                    os_getpid());
214                         if(n < 0)
215                                 panic("check_sysemu : failed to modify system "
216                                       "call return, errno = %d", errno);
217                         break;
218                 }
219                 else if(WIFSTOPPED(status) && (WSTOPSIG(status) == SIGTRAP))
220                         count++;
221                 else
222                         panic("check_ptrace : expected SIGTRAP or "
223                               "(SIGTRAP|0x80), got status = %d", status);
224         }
225         if (stop_ptraced_child(pid, stack, 0, 0) < 0)
226                 goto fail_stopped;
227
228         sysemu_supported = 2;
229         printk("OK\n");
230
231         if ( !force_sysemu_disabled )
232                 set_using_sysemu(sysemu_supported);
233         return;
234
235 fail:
236         stop_ptraced_child(pid, stack, 1, 0);
237 fail_stopped:
238         printk("missing\n");
239 }
240
241 static void __init check_ptrace(void)
242 {
243         void *stack;
244         int pid, syscall, n, status;
245
246         printk("Checking that ptrace can change system call numbers...");
247         pid = start_ptraced_child(&stack);
248
249         if(ptrace(PTRACE_OLDSETOPTIONS, pid, 0, (void *)PTRACE_O_TRACESYSGOOD) < 0)
250                 panic("check_ptrace: PTRACE_OLDSETOPTIONS failed, errno = %d", errno);
251
252         while(1){
253                 if(ptrace(PTRACE_SYSCALL, pid, 0, 0) < 0)
254                         panic("check_ptrace : ptrace failed, errno = %d",
255                               errno);
256                 CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
257                 if(n < 0)
258                         panic("check_ptrace : wait failed, errno = %d", errno);
259                 if(!WIFSTOPPED(status) || (WSTOPSIG(status) != (SIGTRAP|0x80)))
260                         panic("check_ptrace : expected (SIGTRAP|0x80), "
261                               "got status = %d", status);
262
263                 syscall = ptrace(PTRACE_PEEKUSR, pid, PT_SYSCALL_NR_OFFSET,
264                                  0);
265                 if(syscall == __NR_getpid){
266                         n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_NR_OFFSET,
267                                    __NR_getppid);
268                         if(n < 0)
269                                 panic("check_ptrace : failed to modify system "
270                                       "call, errno = %d", errno);
271                         break;
272                 }
273         }
274         stop_ptraced_child(pid, stack, 0, 1);
275         printk("OK\n");
276         check_sysemu();
277 }
278
279 void os_early_checks(void)
280 {
281         check_ptrace();
282 }
283
284 static int __init noprocmm_cmd_param(char *str, int* add)
285 {
286         proc_mm = 0;
287         return 0;
288 }
289
290 __uml_setup("noprocmm", noprocmm_cmd_param,
291 "noprocmm\n"
292 "    Turns off usage of /proc/mm, even if host supports it.\n"
293 "    To support /proc/mm, the host needs to be patched using\n"
294 "    the current skas3 patch.\n\n");
295
296 static int __init noptracefaultinfo_cmd_param(char *str, int* add)
297 {
298         ptrace_faultinfo = 0;
299         return 0;
300 }
301
302 __uml_setup("noptracefaultinfo", noptracefaultinfo_cmd_param,
303 "noptracefaultinfo\n"
304 "    Turns off usage of PTRACE_FAULTINFO, even if host supports\n"
305 "    it. To support PTRACE_FAULTINFO, the host needs to be patched\n"
306 "    using the current skas3 patch.\n\n");
307
308 #ifdef UML_CONFIG_MODE_SKAS
309 static inline void check_skas3_ptrace_support(void)
310 {
311         struct ptrace_faultinfo fi;
312         void *stack;
313         int pid, n;
314
315         printf("Checking for the skas3 patch in the host...");
316         pid = start_ptraced_child(&stack);
317
318         n = ptrace(PTRACE_FAULTINFO, pid, 0, &fi);
319         if (n < 0) {
320                 ptrace_faultinfo = 0;
321                 if(errno == EIO)
322                         printf("not found\n");
323                 else
324                         perror("not found");
325         }
326         else {
327                 if (!ptrace_faultinfo)
328                         printf("found but disabled on command line\n");
329                 else
330                         printf("found\n");
331         }
332
333         init_registers(pid);
334         stop_ptraced_child(pid, stack, 1, 1);
335 }
336
337 int can_do_skas(void)
338 {
339         printf("Checking for /proc/mm...");
340         if (os_access("/proc/mm", OS_ACC_W_OK) < 0) {
341                 proc_mm = 0;
342                 printf("not found\n");
343         }
344         else {
345                 if (!proc_mm)
346                         printf("found but disabled on command line\n");
347                 else
348                         printf("found\n");
349         }
350
351         check_skas3_ptrace_support();
352         return 1;
353 }
354 #else
355 int can_do_skas(void)
356 {
357         return(0);
358 }
359 #endif