process.c

linux内核源码

		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);

		CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED | __WALL));
		if (err < 0)
			panic("userspace - waitpid failed, errno = %d\n",
			      errno);

		regs->is_user = 1;
		save_registers(pid, regs);
		UPT_SYSCALL_NR(regs) = -1; /* Assume: It's not a syscall */

		if (WIFSTOPPED(status)) {
			int sig = WSTOPSIG(status);
		  	switch(sig) {
			case SIGSEGV:
				if (PTRACE_FULL_FAULTINFO ||
				    !ptrace_faultinfo) {
					get_skas_faultinfo(pid,
							   &regs->faultinfo);
					(*sig_info[SIGSEGV])(SIGSEGV, regs);
				}
				else handle_segv(pid, regs);
				break;
			case SIGTRAP + 0x80:
			        handle_trap(pid, regs, local_using_sysemu);
				break;
			case SIGTRAP:
				relay_signal(SIGTRAP, regs);
				break;
			case SIGVTALRM:
				now = os_nsecs();
				if(now < nsecs)
					break;
				block_signals();
				(*sig_info[sig])(sig, regs);
				unblock_signals();
				nsecs = timer.it_value.tv_sec *
					UM_NSEC_PER_SEC +
					timer.it_value.tv_usec *
					UM_NSEC_PER_USEC;
				nsecs += os_nsecs();
				break;
			case SIGIO:
			case SIGILL:
			case SIGBUS:
			case SIGFPE:
			case SIGWINCH:
				block_signals();
				(*sig_info[sig])(sig, regs);
				unblock_signals();
				break;
			default:
			        printk(UM_KERN_ERR "userspace - child stopped "
				       "with signal %d\n", sig);
			}
			pid = userspace_pid[0];
			interrupt_end();

			/* Avoid -ERESTARTSYS handling in host */
			if (PT_SYSCALL_NR_OFFSET != PT_SYSCALL_RET_OFFSET)
				PT_SYSCALL_NR(regs->gp) = -1;
		}
	}
}

static unsigned long thread_regs[MAX_REG_NR];

static int __init init_thread_regs(void)
{
	get_safe_registers(thread_regs);
	/* Set parent's instruction pointer to start of clone-stub */
	thread_regs[REGS_IP_INDEX] = STUB_CODE +
				(unsigned long) stub_clone_handler -
				(unsigned long) &__syscall_stub_start;
	thread_regs[REGS_SP_INDEX] = STUB_DATA + UM_KERN_PAGE_SIZE -
		sizeof(void *);
#ifdef __SIGNAL_FRAMESIZE
	thread_regs[REGS_SP_INDEX] -= __SIGNAL_FRAMESIZE;
#endif
	return 0;
}

__initcall(init_thread_regs);

int copy_context_skas0(unsigned long new_stack, int pid)
{
	struct timeval tv = { .tv_sec = 0, .tv_usec = UM_USEC_PER_SEC / UM_HZ };
	int err;
	unsigned long current_stack = current_stub_stack();
	struct stub_data *data = (struct stub_data *) current_stack;
	struct stub_data *child_data = (struct stub_data *) new_stack;
	unsigned long long new_offset;
	int new_fd = phys_mapping(to_phys((void *)new_stack), &new_offset);

	/*
	 * prepare offset and fd of child's stack as argument for parent's
	 * and child's mmap2 calls
	 */
	*data = ((struct stub_data) { .offset	= MMAP_OFFSET(new_offset),
				      .fd	= new_fd,
				      .timer    = ((struct itimerval)
					           { .it_value = tv,
						     .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);

	/* set a well known return code for detection of child write failure */
	child_data->err = 12345678;

	/*
	 * Wait, until parent has finished its work: read child's pid from
	 * 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);
	wait_stub_done(pid);

	pid = data->err;
	if (pid < 0)
		panic("copy_context_skas0 - stub-parent reports error %d\n",
		      -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 (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL,
		   (void *)PTRACE_O_TRACESYSGOOD) < 0)
		panic("copy_context_skas0 : PTRACE_OLDSETOPTIONS failed, "
		      "errno = %d\n", errno);

	return pid;
}

/*
 * This is used only, if stub pages are needed, while proc_mm is
 * 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)
{
	struct proc_mm_op mmop;
	int n;
	unsigned long long code_offset;
	int code_fd = phys_mapping(to_phys((void *) &__syscall_stub_start),
				   &code_offset);

	mmop = ((struct proc_mm_op) { .op        = MM_MMAP,
				      .u         =
				      { .mmap    =
					{ .addr    = code,
					  .len     = UM_KERN_PAGE_SIZE,
					  .prot    = PROT_EXEC,
					  .flags   = MAP_FIXED | MAP_PRIVATE,
					  .fd      = code_fd,
					  .offset  = code_offset
	} } });
	CATCH_EINTR(n = write(fd, &mmop, sizeof(mmop)));
	if (n != sizeof(mmop)) {
		n = errno;
		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);
	}

	if (stack) {
		unsigned long long map_offset;
		int map_fd = phys_mapping(to_phys((void *)stack), &map_offset);
		mmop = ((struct proc_mm_op)
				{ .op        = MM_MMAP,
				  .u         =
				  { .mmap    =
				    { .addr    = data,
				      .len     = UM_KERN_PAGE_SIZE,
				      .prot    = PROT_READ | PROT_WRITE,
				      .flags   = MAP_FIXED | MAP_SHARED,
				      .fd      = map_fd,
				      .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);
	}
}

void new_thread(void *stack, jmp_buf *buf, void (*handler)(void))
{
	(*buf)[0].JB_IP = (unsigned long) handler;
	(*buf)[0].JB_SP = (unsigned long) stack + UM_THREAD_SIZE -
		sizeof(void *);
}

#define INIT_JMP_NEW_THREAD 0
#define INIT_JMP_CALLBACK 1
#define INIT_JMP_HALT 2
#define INIT_JMP_REBOOT 3

void switch_threads(jmp_buf *me, jmp_buf *you)
{
	if (UML_SETJMP(me) == 0)
		UML_LONGJMP(you, 1);
}

static jmp_buf initial_jmpbuf;

/* XXX Make these percpu */
static void (*cb_proc)(void *arg);
static void *cb_arg;
static jmp_buf *cb_back;

int start_idle_thread(void *stack, jmp_buf *switch_buf)
{
	int n;

	set_handler(SIGWINCH, (__sighandler_t) sig_handler,
		    SA_ONSTACK | SA_RESTART, SIGUSR1, SIGIO, SIGVTALRM, -1);

	/*
	 * Can't use UML_SETJMP or UML_LONGJMP here because they save
	 * and restore signals, with the possible side-effect of
	 * trying to handle any signals which came when they were
	 * blocked, which can't be done on this stack.
	 * Signals must be blocked when jumping back here and restored
	 * after returning to the jumper.
	 */
	n = setjmp(initial_jmpbuf);
	switch(n) {
	case INIT_JMP_NEW_THREAD:
		(*switch_buf)[0].JB_IP = (unsigned long) new_thread_handler;
		(*switch_buf)[0].JB_SP = (unsigned long) stack +
			UM_THREAD_SIZE - sizeof(void *);
		break;
	case INIT_JMP_CALLBACK:
		(*cb_proc)(cb_arg);
		longjmp(*cb_back, 1);
		break;
	case INIT_JMP_HALT:
		kmalloc_ok = 0;
		return 0;
	case INIT_JMP_REBOOT:
		kmalloc_ok = 0;
		return 1;
	default:
		panic("Bad sigsetjmp return in start_idle_thread - %d\n", n);
	}
	longjmp(*switch_buf, 1);
}

void initial_thread_cb_skas(void (*proc)(void *), void *arg)
{
	jmp_buf here;

	cb_proc = proc;
	cb_arg = arg;
	cb_back = &here;

	block_signals();
	if (UML_SETJMP(&here) == 0)
		UML_LONGJMP(&initial_jmpbuf, INIT_JMP_CALLBACK);
	unblock_signals();

	cb_proc = NULL;
	cb_arg = NULL;
	cb_back = NULL;
}

void halt_skas(void)
{
	block_signals();
	UML_LONGJMP(&initial_jmpbuf, INIT_JMP_HALT);
}

void reboot_skas(void)
{
	block_signals();
	UML_LONGJMP(&initial_jmpbuf, INIT_JMP_REBOOT);
}

void __switch_mm(struct mm_id *mm_idp)
{
	int err;

	/* FIXME: need cpu pid in __switch_mm */
	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);
	}
	else userspace_pid[0] = mm_idp->u.pid;
}