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, syscall, 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         while(1){
 196                 count++;
 197                 if(ptrace(PTRACE_SYSEMU_SINGLESTEP, pid, 0, 0) < 0)
 198                         goto fail;
 199                 CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
 200                 if(n < 0)
 201                         panic("check_ptrace : wait failed, errno = %d", errno);
 202                 if(!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGTRAP))
 203                         panic("check_ptrace : expected (SIGTRAP|SYSCALL_TRAP), "
 204                               "got status = %d", status);
 205
 206                 syscall = ptrace(PTRACE_PEEKUSR, pid, PT_SYSCALL_NR_OFFSET,
 207                                  0);
 208                 if(syscall == __NR_getpid){
 209                         if (!count)
 210                                 panic("check_ptrace : SYSEMU_SINGLESTEP doesn't singlestep");
 211                         n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_RET_OFFSET,
 212                                    os_getpid());
 213                         if(n < 0)
 214                                 panic("check_sysemu : failed to modify system "
 215                                       "call return, errno = %d", errno);
 216                         break;
 217                 }
 218         }
 219         if (stop_ptraced_child(pid, stack, 0, 0) < 0)
 220                 goto fail_stopped;
 221
 222         sysemu_supported = 2;
 223         printk("OK\n");
 224
 225         if ( !force_sysemu_disabled )
 226                 set_using_sysemu(sysemu_supported);
 227         return;
 228
 229 fail:
 230         stop_ptraced_child(pid, stack, 1, 0);
 231 fail_stopped:
 232         printk("missing\n");
 233 }
 234
 235 static void __init check_ptrace(void)
 236 {
 237         void *stack;
 238         int pid, syscall, n, status;
 239
 240         printk("Checking that ptrace can change system call numbers...");
 241         pid = start_ptraced_child(&stack);
 242
 243         if(ptrace(PTRACE_OLDSETOPTIONS, pid, 0, (void *)PTRACE_O_TRACESYSGOOD) < 0)
 244                 panic("check_ptrace: PTRACE_OLDSETOPTIONS failed, errno = %d", errno);
 245
 246         while(1){
 247                 if(ptrace(PTRACE_SYSCALL, pid, 0, 0) < 0)
 248                         panic("check_ptrace : ptrace failed, errno = %d",
 249                               errno);
 250                 CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
 251                 if(n < 0)
 252                         panic("check_ptrace : wait failed, errno = %d", errno);
 253                 if(!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGTRAP + 0x80))
 254                         panic("check_ptrace : expected SIGTRAP + 0x80, "
 255                               "got status = %d", status);
 256
 257                 syscall = ptrace(PTRACE_PEEKUSR, pid, PT_SYSCALL_NR_OFFSET,
 258                                  0);
 259                 if(syscall == __NR_getpid){
 260                         n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_NR_OFFSET,
 261                                    __NR_getppid);
 262                         if(n < 0)
 263                                 panic("check_ptrace : failed to modify system "
 264                                       "call, errno = %d", errno);
 265                         break;
 266                 }
 267         }
 268         stop_ptraced_child(pid, stack, 0, 1);
 269         printk("OK\n");
 270         check_sysemu();
 271 }
 272
 273 void os_early_checks(void)
 274 {
 275         check_ptrace();
 276 }
 277
 278 #ifdef UML_CONFIG_MODE_SKAS
 279 static inline void check_skas3_ptrace_support(void)
 280 {
 281         struct ptrace_faultinfo fi;
 282         void *stack;
 283         int pid, n;
 284
 285         printf("Checking for the skas3 patch in the host...");
 286         pid = start_ptraced_child(&stack);
 287
 288         n = ptrace(PTRACE_FAULTINFO, pid, 0, &fi);
 289         if (n < 0) {
 290                 ptrace_faultinfo = 0;
 291                 if(errno == EIO)
 292                         printf("not found\n");
 293                 else
 294                         perror("not found");
 295         }
 296         else {
 297                 if (!ptrace_faultinfo)
 298                         printf("found but disabled on command line\n");
 299                 else
 300                         printf("found\n");
 301         }
 302
 303         init_registers(pid);
 304         stop_ptraced_child(pid, stack, 1, 1);
 305 }
 306
 307 int can_do_skas(void)
 308 {
 309         printf("Checking for /proc/mm...");
 310         if (os_access("/proc/mm", OS_ACC_W_OK) < 0) {
 311                 proc_mm = 0;
 312                 printf("not found\n");
 313         }
 314         else {
 315                 if (!proc_mm)
 316                         printf("found but disabled on command line\n");
 317                 else
 318                         printf("found\n");
 319         }
 320
 321         check_skas3_ptrace_support();
 322         return 1;
 323 }
 324 #else
 325 int can_do_skas(void)
 326 {
 327         return(0);
 328 }
 329 #endif