arch/um/os-Linux/helper.c

   1 /*
   2  * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
   3  * Licensed under the GPL
   4  */
   5
   6 #include <stdlib.h>
   7 #include <unistd.h>
   8 #include <errno.h>
   9 #include <sched.h>
  10 #include <linux/limits.h>
  11 #include <sys/socket.h>
  12 #include <sys/wait.h>
  13 #include "kern_constants.h"
  14 #include "kern_util.h"
  15 #include "os.h"
  16 #include "um_malloc.h"
  17 #include "user.h"
  18
  19 struct helper_data {
  20         void (*pre_exec)(void*);
  21         void *pre_data;
  22         char **argv;
  23         int fd;
  24         char *buf;
  25 };
  26
  27 static int helper_child(void *arg)
  28 {
  29         struct helper_data *data = arg;
  30         char **argv = data->argv;
  31         int err, ret;
  32
  33         if (data->pre_exec != NULL)
  34                 (*data->pre_exec)(data->pre_data);
  35         err = execvp_noalloc(data->buf, argv[0], argv);
  36
  37         /* If the exec succeeds, we don't get here */
  38         CATCH_EINTR(ret = write(data->fd, &err, sizeof(err)));
  39
  40         return 0;
  41 }
  42
  43 /* Returns either the pid of the child process we run or -E* on failure. */
  44 int run_helper(void (*pre_exec)(void *), void *pre_data, char **argv)
  45 {
  46         struct helper_data data;
  47         unsigned long stack, sp;
  48         int pid, fds[2], ret, n;
  49
  50         stack = alloc_stack(0, __cant_sleep());
  51         if (stack == 0)
  52                 return -ENOMEM;
  53
  54         ret = socketpair(AF_UNIX, SOCK_STREAM, 0, fds);
  55         if (ret < 0) {
  56                 ret = -errno;
  57                 printk(UM_KERN_ERR "run_helper : pipe failed, errno = %d\n",
  58                        errno);
  59                 goto out_free;
  60         }
  61
  62         ret = os_set_exec_close(fds[1]);
  63         if (ret < 0) {
  64                 printk(UM_KERN_ERR "run_helper : setting FD_CLOEXEC failed, "
  65                        "ret = %d\n", -ret);
  66                 goto out_close;
  67         }
  68
  69         sp = stack + UM_KERN_PAGE_SIZE - sizeof(void *);
  70         data.pre_exec = pre_exec;
  71         data.pre_data = pre_data;
  72         data.argv = argv;
  73         data.fd = fds[1];
  74         data.buf = __cant_sleep() ? uml_kmalloc(PATH_MAX, UM_GFP_ATOMIC) :
  75                                         uml_kmalloc(PATH_MAX, UM_GFP_KERNEL);
  76         pid = clone(helper_child, (void *) sp, CLONE_VM, &data);
  77         if (pid < 0) {
  78                 ret = -errno;
  79                 printk(UM_KERN_ERR "run_helper : clone failed, errno = %d\n",
  80                        errno);
  81                 goto out_free2;
  82         }
  83
  84         close(fds[1]);
  85         fds[1] = -1;
  86
  87         /*
  88          * Read the errno value from the child, if the exec failed, or get 0 if
  89          * the exec succeeded because the pipe fd was set as close-on-exec.
  90          */
  91         n = read(fds[0], &ret, sizeof(ret));
  92         if (n == 0) {
  93                 ret = pid;
  94         } else {
  95                 if (n < 0) {
  96                         n = -errno;
  97                         printk(UM_KERN_ERR "run_helper : read on pipe failed, "
  98                                "ret = %d\n", -n);
  99                         ret = n;
 100                 }
 101                 CATCH_EINTR(waitpid(pid, NULL, __WCLONE));
 102         }
 103
 104 out_free2:
 105         kfree(data.buf);
 106 out_close:
 107         if (fds[1] != -1)
 108                 close(fds[1]);
 109         close(fds[0]);
 110 out_free:
 111         free_stack(stack, 0);
 112         return ret;
 113 }
 114
 115 int run_helper_thread(int (*proc)(void *), void *arg, unsigned int flags,
 116                       unsigned long *stack_out)
 117 {
 118         unsigned long stack, sp;
 119         int pid, status, err;
 120
 121         stack = alloc_stack(0, __cant_sleep());
 122         if (stack == 0)
 123                 return -ENOMEM;
 124
 125         sp = stack + UM_KERN_PAGE_SIZE - sizeof(void *);
 126         pid = clone(proc, (void *) sp, flags, arg);
 127         if (pid < 0) {
 128                 err = -errno;
 129                 printk(UM_KERN_ERR "run_helper_thread : clone failed, "
 130                        "errno = %d\n", errno);
 131                 return err;
 132         }
 133         if (stack_out == NULL) {
 134                 CATCH_EINTR(pid = waitpid(pid, &status, __WCLONE));
 135                 if (pid < 0) {
 136                         err = -errno;
 137                         printk(UM_KERN_ERR "run_helper_thread - wait failed, "
 138                                "errno = %d\n", errno);
 139                         pid = err;
 140                 }
 141                 if (!WIFEXITED(status) || (WEXITSTATUS(status) != 0))
 142                         printk(UM_KERN_ERR "run_helper_thread - thread "
 143                                "returned status 0x%x\n", status);
 144                 free_stack(stack, 0);
 145         } else
 146                 *stack_out = stack;
 147         return pid;
 148 }
 149
 150 int helper_wait(int pid)
 151 {
 152         int ret, status;
 153         int wflags = __WCLONE;
 154
 155         CATCH_EINTR(ret = waitpid(pid, &status, wflags));
 156         if (ret < 0) {
 157                 printk(UM_KERN_ERR "helper_wait : waitpid process %d failed, "
 158                        "errno = %d\n", pid, errno);
 159                 return -errno;
 160         } else if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
 161                 printk(UM_KERN_ERR "helper_wait : process %d exited with "
 162                        "status 0x%x\n", pid, status);
 163                 return -ECHILD;
 164         } else
 165                 return 0;
 166 }