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 <linux/slab.h>
  12 #include <sys/socket.h>
  13 #include <sys/wait.h>
  14 #include "kern_constants.h"
  15 #include "kern_util.h"
  16 #include "os.h"
  17 #include "um_malloc.h"
  18 #include "user.h"
  19
  20 struct helper_data {
  21         void (*pre_exec)(void*);
  22         void *pre_data;
  23         char **argv;
  24         int fd;
  25         char *buf;
  26 };
  27
  28 static int helper_child(void *arg)
  29 {
  30         struct helper_data *data = arg;
  31         char **argv = data->argv;
  32         int err;
  33
  34         if (data->pre_exec != NULL)
  35                 (*data->pre_exec)(data->pre_data);
  36         err = execvp_noalloc(data->buf, argv[0], argv);
  37
  38         /* If the exec succeeds, we don't get here */
  39         write(data->fd, &err, sizeof(err));
  40
  41         return 0;
  42 }
  43
  44 /* Returns either the pid of the child process we run or -E* on failure. */
  45 int run_helper(void (*pre_exec)(void *), void *pre_data, char **argv)
  46 {
  47         struct helper_data data;
  48         unsigned long stack, sp;
  49         int pid, fds[2], ret, n;
  50
  51         stack = alloc_stack(0, __cant_sleep());
  52         if (stack == 0)
  53                 return -ENOMEM;
  54
  55         ret = socketpair(AF_UNIX, SOCK_STREAM, 0, fds);
  56         if (ret < 0) {
  57                 ret = -errno;
  58                 printk(UM_KERN_ERR "run_helper : pipe failed, errno = %d\n",
  59                        errno);
  60                 goto out_free;
  61         }
  62
  63         ret = os_set_exec_close(fds[1]);
  64         if (ret < 0) {
  65                 printk(UM_KERN_ERR "run_helper : setting FD_CLOEXEC failed, "
  66                        "ret = %d\n", -ret);
  67                 goto out_close;
  68         }
  69
  70         sp = stack + UM_KERN_PAGE_SIZE - sizeof(void *);
  71         data.pre_exec = pre_exec;
  72         data.pre_data = pre_data;
  73         data.argv = argv;
  74         data.fd = fds[1];
  75         data.buf = __cant_sleep() ? uml_kmalloc(PATH_MAX, UM_GFP_ATOMIC) :
  76                                         uml_kmalloc(PATH_MAX, UM_GFP_KERNEL);
  77         pid = clone(helper_child, (void *) sp, CLONE_VM, &data);
  78         if (pid < 0) {
  79                 ret = -errno;
  80                 printk(UM_KERN_ERR "run_helper : clone failed, errno = %d\n",
  81                        errno);
  82                 goto out_free2;
  83         }
  84
  85         close(fds[1]);
  86         fds[1] = -1;
  87
  88         /*
  89          * Read the errno value from the child, if the exec failed, or get 0 if
  90          * the exec succeeded because the pipe fd was set as close-on-exec.
  91          */
  92         n = read(fds[0], &ret, sizeof(ret));
  93         if (n == 0) {
  94                 ret = pid;
  95         } else {
  96                 if (n < 0) {
  97                         n = -errno;
  98                         printk(UM_KERN_ERR "run_helper : read on pipe failed, "
  99                                "ret = %d\n", -n);
 100                         ret = n;
 101                 }
 102                 CATCH_EINTR(waitpid(pid, NULL, __WCLONE));
 103         }
 104
 105 out_free2:
 106         kfree(data.buf);
 107 out_close:
 108         if (fds[1] != -1)
 109                 close(fds[1]);
 110         close(fds[0]);
 111 out_free:
 112         free_stack(stack, 0);
 113         return ret;
 114 }
 115
 116 int run_helper_thread(int (*proc)(void *), void *arg, unsigned int flags,
 117                       unsigned long *stack_out)
 118 {
 119         unsigned long stack, sp;
 120         int pid, status, err;
 121
 122         stack = alloc_stack(0, __cant_sleep());
 123         if (stack == 0)
 124                 return -ENOMEM;
 125
 126         sp = stack + UM_KERN_PAGE_SIZE - sizeof(void *);
 127         pid = clone(proc, (void *) sp, flags, arg);
 128         if (pid < 0) {
 129                 err = -errno;
 130                 printk(UM_KERN_ERR "run_helper_thread : clone failed, "
 131                        "errno = %d\n", errno);
 132                 return err;
 133         }
 134         if (stack_out == NULL) {
 135                 CATCH_EINTR(pid = waitpid(pid, &status, __WCLONE));
 136                 if (pid < 0) {
 137                         err = -errno;
 138                         printk(UM_KERN_ERR "run_helper_thread - wait failed, "
 139                                "errno = %d\n", errno);
 140                         pid = err;
 141                 }
 142                 if (!WIFEXITED(status) || (WEXITSTATUS(status) != 0))
 143                         printk(UM_KERN_ERR "run_helper_thread - thread "
 144                                "returned status 0x%x\n", status);
 145                 free_stack(stack, 0);
 146         } else
 147                 *stack_out = stack;
 148         return pid;
 149 }
 150
 151 int helper_wait(int pid)
 152 {
 153         int ret, status;
 154         int wflags = __WCLONE;
 155
 156         CATCH_EINTR(ret = waitpid(pid, &status, wflags));
 157         if (ret < 0) {
 158                 printk(UM_KERN_ERR "helper_wait : waitpid process %d failed, "
 159                        "errno = %d\n", pid, errno);
 160                 return -errno;
 161         } else if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
 162                 printk(UM_KERN_ERR "helper_wait : process %d exited with "
 163                        "status 0x%x\n", pid, status);
 164                 return -ECHILD;
 165         } else
 166                 return 0;
 167 }