static int ptrace_dump_regs(int pid)
 {
-        unsigned long regs[MAX_REG_NR];
-        int i;
+       unsigned long regs[MAX_REG_NR];
+       int i;
 
-        if (ptrace(PTRACE_GETREGS, pid, 0, regs) < 0)
-                return -errno;
+       if (ptrace(PTRACE_GETREGS, pid, 0, regs) < 0)
+               return -errno;
 
        printk(UM_KERN_ERR "Stub registers -\n");
        for (i = 0; i < ARRAY_SIZE(regs); i++)
                printk(UM_KERN_ERR "\t%d - %lx\n", i, regs[i]);
 
-        return 0;
+       return 0;
 }
 
 /*
                        break;
 
                err = ptrace(PTRACE_CONT, pid, 0, 0);
-               if (err)
-                       panic("wait_stub_done : continue failed, errno = %d\n",
-                             errno);
+               if (err) {
+                       printk(UM_KERN_ERR "wait_stub_done : continue failed, "
+                              "errno = %d\n", errno);
+                       fatal_sigsegv();
+               }
        }
 
        if (((1 << WSTOPSIG(status)) & STUB_DONE_MASK) != 0)
        if (err)
                printk(UM_KERN_ERR "Failed to get registers from stub, "
                       "errno = %d\n", -err);
-       panic("wait_stub_done : failed to wait for SIGUSR1/SIGTRAP, pid = %d, "
-             "n = %d, errno = %d, status = 0x%x\n", pid, n, errno, status);
+       printk(UM_KERN_ERR "wait_stub_done : failed to wait for SIGTRAP, "
+              "pid = %d, n = %d, errno = %d, status = 0x%x\n", pid, n, errno,
+              status);
+       fatal_sigsegv();
 }
 
 extern unsigned long current_stub_stack(void);
 
        if (ptrace_faultinfo) {
                err = ptrace(PTRACE_FAULTINFO, pid, 0, fi);
-               if (err)
-                       panic("get_skas_faultinfo - PTRACE_FAULTINFO failed, "
-                             "errno = %d\n", errno);
+               if (err) {
+                       printk(UM_KERN_ERR "get_skas_faultinfo - "
+                              "PTRACE_FAULTINFO failed, errno = %d\n", errno);
+                       fatal_sigsegv();
+               }
 
                /* Special handling for i386, which has different structs */
                if (sizeof(struct ptrace_faultinfo) < sizeof(struct faultinfo))
        }
        else {
                err = ptrace(PTRACE_CONT, pid, 0, SIGSEGV);
-               if (err)
-                       panic("Failed to continue stub, pid = %d, errno = %d\n",
-                             pid, errno);
+               if (err) {
+                       printk(UM_KERN_ERR "Failed to continue stub, pid = %d, "
+                              "errno = %d\n", pid, errno);
+                       fatal_sigsegv();
+               }
                wait_stub_done(pid);
 
                /*
        {
                err = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_NR_OFFSET,
                             __NR_getpid);
-               if (err < 0)
-                       panic("handle_trap - nullifying syscall failed, "
-                             "errno = %d\n", errno);
+               if (err < 0) {
+                       printk(UM_KERN_ERR "handle_trap - nullifying syscall "
+                              "failed, errno = %d\n", errno);
+                       fatal_sigsegv();
+               }
 
                err = ptrace(PTRACE_SYSCALL, pid, 0, 0);
-               if (err < 0)
-                       panic("handle_trap - continuing to end of syscall "
-                             "failed, errno = %d\n", errno);
+               if (err < 0) {
+                       printk(UM_KERN_ERR "handle_trap - continuing to end of "
+                              "syscall failed, errno = %d\n", errno);
+                       fatal_sigsegv();
+               }
 
                CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED | __WALL));
                if ((err < 0) || !WIFSTOPPED(status) ||
-                  (WSTOPSIG(status) != SIGTRAP + 0x80)) {
-                        err = ptrace_dump_regs(pid);
-                        if (err)
-                                printk(UM_KERN_ERR "Failed to get registers "
+                   (WSTOPSIG(status) != SIGTRAP + 0x80)) {
+                       err = ptrace_dump_regs(pid);
+                       if (err)
+                               printk(UM_KERN_ERR "Failed to get registers "
                                       "from process, errno = %d\n", -err);
-                       panic("handle_trap - failed to wait at end of syscall, "
-                             "errno = %d, status = %d\n", errno, status);
-                }
+                       printk(UM_KERN_ERR "handle_trap - failed to wait at "
+                              "end of syscall, errno = %d, status = %d\n",
+                              errno, status);
+                       fatal_sigsegv();
+               }
        }
 
        handle_syscall(regs);
        signal(SIGTERM, SIG_DFL);
        signal(SIGWINCH, SIG_IGN);
        err = set_interval();
-       if (err)
-               panic("userspace_tramp - setting timer failed, errno = %d\n",
-                     err);
+       if (err) {
+               printk(UM_KERN_ERR "userspace_tramp - setting timer failed, "
+                      "errno = %d\n", err);
+               exit(1);
+       }
 
        if (!proc_mm) {
                /*
                sa.sa_flags = SA_ONSTACK | SA_NODEFER;
                sa.sa_handler = (void *) v;
                sa.sa_restorer = NULL;
-               if (sigaction(SIGSEGV, &sa, NULL) < 0)
-                       panic("userspace_tramp - setting SIGSEGV handler "
-                             "failed - errno = %d\n", errno);
+               if (sigaction(SIGSEGV, &sa, NULL) < 0) {
+                       printk(UM_KERN_ERR "userspace_tramp - setting SIGSEGV "
+                              "handler failed - errno = %d\n", errno);
+                       exit(1);
+               }
        }
 
        kill(os_getpid(), SIGSTOP);
 {
        void *stack;
        unsigned long sp;
-       int pid, status, n, flags;
+       int pid, status, n, flags, err;
 
        stack = mmap(NULL, UM_KERN_PAGE_SIZE,
                     PROT_READ | PROT_WRITE | PROT_EXEC,
                     MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
-       if (stack == MAP_FAILED)
-               panic("start_userspace : mmap failed, errno = %d", errno);
+       if (stack == MAP_FAILED) {
+               err = -errno;
+               printk(UM_KERN_ERR "start_userspace : mmap failed, "
+                      "errno = %d", errno);
+               return err;
+       }
+
        sp = (unsigned long) stack + UM_KERN_PAGE_SIZE - sizeof(void *);
 
        flags = CLONE_FILES;
                flags |= SIGCHLD;
 
        pid = clone(userspace_tramp, (void *) sp, flags, (void *) stub_stack);
-       if (pid < 0)
-               panic("start_userspace : clone failed, errno = %d", errno);
+       if (pid < 0) {
+               err = -errno;
+               printk(UM_KERN_ERR "start_userspace : clone failed, "
+                      "errno = %d", errno);
+               return err;
+       }
 
        do {
                CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED | __WALL));
-               if (n < 0)
-                       panic("start_userspace : wait failed, errno = %d",
-                             errno);
+               if (n < 0) {
+                       err = -errno;
+                       printk(UM_KERN_ERR "start_userspace : wait failed, "
+                              "errno = %d", errno);
+                       goto out_kill;
+               }
        } while (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGVTALRM));
 
-       if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP))
-               panic("start_userspace : expected SIGSTOP, got status = %d",
-                     status);
+       if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP)) {
+               err = -EINVAL;
+               printk(UM_KERN_ERR "start_userspace : expected SIGSTOP, got "
+                      "status = %d", status);
+               goto out_kill;
+       }
 
        if (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL,
-                  (void *) PTRACE_O_TRACESYSGOOD) < 0)
-               panic("start_userspace : PTRACE_OLDSETOPTIONS failed, "
-                     "errno = %d\n", errno);
+                  (void *) PTRACE_O_TRACESYSGOOD) < 0) {
+               err = -errno;
+               printk(UM_KERN_ERR "start_userspace : PTRACE_OLDSETOPTIONS "
+                      "failed, errno = %d\n", errno);
+               goto out_kill;
+       }
 
-       if (munmap(stack, UM_KERN_PAGE_SIZE) < 0)
-               panic("start_userspace : munmap failed, errno = %d\n", errno);
+       if (munmap(stack, UM_KERN_PAGE_SIZE) < 0) {
+               err = -errno;
+               printk(UM_KERN_ERR "start_userspace : munmap failed, "
+                      "errno = %d\n", errno);
+               goto out_kill;
+       }
 
        return pid;
+
+ out_kill:
+       os_kill_ptraced_process(pid, 1);
+       return err;
 }
 
 void userspace(struct uml_pt_regs *regs)
        nsecs += os_nsecs();
 
        while (1) {
+               /*
+                * This can legitimately fail if the process loads a
+                * bogus value into a segment register.  It will
+                * segfault and PTRACE_GETREGS will read that value
+                * out of the process.  However, PTRACE_SETREGS will
+                * fail.  In this case, there is nothing to do but
+                * just kill the process.
+                */
                if (ptrace(PTRACE_SETREGS, pid, 0, regs->gp))
-                       panic("userspace - PTRACE_SETREGS failed, "
-                             "errno = %d\n", errno);
+                       fatal_sigsegv();
 
                /* Now we set local_using_sysemu to be used for one loop */
                local_using_sysemu = get_using_sysemu();
                op = SELECT_PTRACE_OPERATION(local_using_sysemu,
                                             singlestepping(NULL));
 
-               err = ptrace(op, pid, 0, 0);
-               if (err)
-                       panic("userspace - could not resume userspace process, "
-                             "pid=%d, ptrace operation = %d, errno = %d\n",
-                             pid, op, errno);
+               if (ptrace(op, pid, 0, 0)) {
+                       printk(UM_KERN_ERR "userspace - ptrace continue "
+                              "failed, op = %d, errno = %d\n", op, errno);
+                       fatal_sigsegv();
+               }
 
                CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED | __WALL));
-               if (err < 0)
-                       panic("userspace - waitpid failed, errno = %d\n",
-                             errno);
+               if (err < 0) {
+                       printk(UM_KERN_ERR "userspace - wait failed, "
+                              "errno = %d\n", errno);
+                       fatal_sigsegv();
+               }
 
                regs->is_user = 1;
-               if (ptrace(PTRACE_GETREGS, pid, 0, regs->gp))
-                       panic("userspace - saving registers failed, "
-                             "errno = %d\n", errno);
+               if (ptrace(PTRACE_GETREGS, pid, 0, regs->gp)) {
+                       printk(UM_KERN_ERR "userspace - PTRACE_GETREGS failed, "
+                              "errno = %d\n", errno);
+                       fatal_sigsegv();
+               }
 
                UPT_SYSCALL_NR(regs) = -1; /* Assume: It's not a syscall */
 
                        default:
                                printk(UM_KERN_ERR "userspace - child stopped "
                                       "with signal %d\n", sig);
+                               fatal_sigsegv();
                        }
                        pid = userspace_pid[0];
                        interrupt_end();
                                                     .it_interval = tv }) });
 
        err = ptrace_setregs(pid, thread_regs);
-       if (err < 0)
-               panic("copy_context_skas0 : PTRACE_SETREGS failed, "
-                     "pid = %d, errno = %d\n", pid, -err);
+       if (err < 0) {
+               err = -errno;
+               printk(UM_KERN_ERR "copy_context_skas0 : PTRACE_SETREGS "
+                      "failed, pid = %d, errno = %d\n", pid, -err);
+               return err;
+       }
 
        /* set a well known return code for detection of child write failure */
        child_data->err = 12345678;
         * parent's stack, and check, if bad result.
         */
        err = ptrace(PTRACE_CONT, pid, 0, 0);
-       if (err)
-               panic("Failed to continue new process, pid = %d, "
-                     "errno = %d\n", pid, errno);
+       if (err) {
+               err = -errno;
+               printk(UM_KERN_ERR "Failed to continue new process, pid = %d, "
+                      "errno = %d\n", pid, errno);
+               return err;
+       }
+
        wait_stub_done(pid);
 
        pid = data->err;
-       if (pid < 0)
-               panic("copy_context_skas0 - stub-parent reports error %d\n",
-                     -pid);
+       if (pid < 0) {
+               printk(UM_KERN_ERR "copy_context_skas0 - stub-parent reports "
+                      "error %d\n", -pid);
+               return pid;
+       }
 
        /*
         * Wait, until child has finished too: read child's result from
         * child's stack and check it.
         */
        wait_stub_done(pid);
-       if (child_data->err != STUB_DATA)
-               panic("copy_context_skas0 - stub-child reports error %ld\n",
-                     child_data->err);
+       if (child_data->err != STUB_DATA) {
+               printk(UM_KERN_ERR "copy_context_skas0 - stub-child reports "
+                      "error %ld\n", child_data->err);
+               err = child_data->err;
+               goto out_kill;
+       }
 
        if (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL,
-                  (void *)PTRACE_O_TRACESYSGOOD) < 0)
-               panic("copy_context_skas0 : PTRACE_OLDSETOPTIONS failed, "
-                     "errno = %d\n", errno);
+                  (void *)PTRACE_O_TRACESYSGOOD) < 0) {
+               err = -errno;
+               printk(UM_KERN_ERR "copy_context_skas0 : PTRACE_OLDSETOPTIONS "
+                      "failed, errno = %d\n", errno);
+               goto out_kill;
+       }
 
        return pid;
+
+ out_kill:
+       os_kill_ptraced_process(pid, 1);
+       return err;
 }
 
 /*
  * available. Opening /proc/mm creates a new mm_context, which lacks
  * the stub-pages. Thus, we map them using /proc/mm-fd
  */
-void map_stub_pages(int fd, unsigned long code,
-                   unsigned long data, unsigned long stack)
+int map_stub_pages(int fd, unsigned long code, unsigned long data,
+                  unsigned long stack)
 {
        struct proc_mm_op mmop;
        int n;
                printk(UM_KERN_ERR "mmap args - addr = 0x%lx, fd = %d, "
                       "offset = %llx\n", code, code_fd,
                       (unsigned long long) code_offset);
-               panic("map_stub_pages : /proc/mm map for code failed, "
-                     "err = %d\n", n);
+               printk(UM_KERN_ERR "map_stub_pages : /proc/mm map for code "
+                      "failed, err = %d\n", n);
+               return -n;
        }
 
        if (stack) {
                                      .offset  = map_offset
                } } });
                CATCH_EINTR(n = write(fd, &mmop, sizeof(mmop)));
-               if (n != sizeof(mmop))
-                       panic("map_stub_pages : /proc/mm map for data failed, "
-                             "err = %d\n", errno);
+               if (n != sizeof(mmop)) {
+                       n = errno;
+                       printk(UM_KERN_ERR "map_stub_pages : /proc/mm map for "
+                              "data failed, err = %d\n", n);
+                       return -n;
+               }
        }
+
+       return 0;
 }
 
 void new_thread(void *stack, jmp_buf *buf, void (*handler)(void))
                kmalloc_ok = 0;
                return 1;
        default:
-               panic("Bad sigsetjmp return in start_idle_thread - %d\n", n);
+               printk(UM_KERN_ERR "Bad sigsetjmp return in "
+                      "start_idle_thread - %d\n", n);
+               fatal_sigsegv();
        }
        longjmp(*switch_buf, 1);
 }
        if (proc_mm) {
                err = ptrace(PTRACE_SWITCH_MM, userspace_pid[0], 0,
                             mm_idp->u.mm_fd);
-               if (err)
-                       panic("__switch_mm - PTRACE_SWITCH_MM failed, "
-                             "errno = %d\n", errno);
+               if (err) {
+                       printk(UM_KERN_ERR "__switch_mm - PTRACE_SWITCH_MM "
+                              "failed, errno = %d\n", errno);
+                       fatal_sigsegv();
+               }
        }
        else userspace_pid[0] = mm_idp->u.pid;
 }