arch/um/os-Linux/helper.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
   4  */
   5
   6 #include <stdlib.h>
   7 #include <string.h>
   8 #include <unistd.h>
   9 #include <errno.h>
  10 #include <sched.h>
  11 #include <linux/limits.h>
  12 #include <sys/socket.h>
  13 #include <sys/wait.h>
  14 #include <kern_util.h>
  15 #include <os.h>
  16 #include <um_malloc.h>
  17
  18 struct helper_data {
  19         void (*pre_exec)(void*);
  20         void *pre_data;
  21         char **argv;
  22         int fd;
  23         char *buf;
  24 };
  25
  26 static int helper_child(void *arg)
  27 {
  28         struct helper_data *data = arg;
  29         char **argv = data->argv;
  30         int err, ret;
  31
  32         if (data->pre_exec != NULL)
  33                 (*data->pre_exec)(data->pre_data);
  34         err = execvp_noalloc(data->buf, argv[0], argv);
  35
  36         /* If the exec succeeds, we don't get here */
  37         CATCH_EINTR(ret = write(data->fd, &err, sizeof(err)));
  38
  39         return 0;
  40 }
  41
  42 /* Returns either the pid of the child process we run or -E* on failure. */
  43 int run_helper(void (*pre_exec)(void *), void *pre_data, char **argv)
  44 {
  45         struct helper_data data;
  46         unsigned long stack, sp;
  47         int pid, fds[2], ret, n;
  48
  49         stack = alloc_stack(0, __uml_cant_sleep());
  50         if (stack == 0)
  51                 return -ENOMEM;
  52
  53         ret = socketpair(AF_UNIX, SOCK_STREAM, 0, fds);
  54         if (ret < 0) {
  55                 ret = -errno;
  56                 printk(UM_KERN_ERR "run_helper : pipe failed, errno = %d\n",
  57                        errno);
  58                 goto out_free;
  59         }
  60
  61         ret = os_set_exec_close(fds[1]);
  62         if (ret < 0) {
  63                 printk(UM_KERN_ERR "run_helper : setting FD_CLOEXEC failed, "
  64                        "ret = %d\n", -ret);
  65                 goto out_close;
  66         }
  67
  68         sp = stack + UM_KERN_PAGE_SIZE;
  69         data.pre_exec = pre_exec;
  70         data.pre_data = pre_data;
  71         data.argv = argv;
  72         data.fd = fds[1];
  73         data.buf = __uml_cant_sleep() ? uml_kmalloc(PATH_MAX, UM_GFP_ATOMIC) :
  74                                         uml_kmalloc(PATH_MAX, UM_GFP_KERNEL);
  75         pid = clone(helper_child, (void *) sp, CLONE_VM, &data);
  76         if (pid < 0) {
  77                 ret = -errno;
  78                 printk(UM_KERN_ERR "run_helper : clone failed, errno = %d\n",
  79                        errno);
  80                 goto out_free2;
  81         }
  82
  83         close(fds[1]);
  84         fds[1] = -1;
  85
  86         /*
  87          * Read the errno value from the child, if the exec failed, or get 0 if
  88          * the exec succeeded because the pipe fd was set as close-on-exec.
  89          */
  90         n = read(fds[0], &ret, sizeof(ret));
  91         if (n == 0) {
  92                 ret = pid;
  93         } else {
  94                 if (n < 0) {
  95                         n = -errno;
  96                         printk(UM_KERN_ERR "run_helper : read on pipe failed, "
  97                                "ret = %d\n", -n);
  98                         ret = n;
  99                 }
 100                 CATCH_EINTR(waitpid(pid, NULL, __WALL));
 101         }
 102
 103         if (ret < 0)
 104                 printk(UM_KERN_ERR "run_helper : failed to exec %s on host: %s\n",
 105                        argv[0], strerror(-ret));
 106
 107 out_free2:
 108         kfree(data.buf);
 109 out_close:
 110         if (fds[1] != -1)
 111                 close(fds[1]);
 112         close(fds[0]);
 113 out_free:
 114         free_stack(stack, 0);
 115         return ret;
 116 }
 117
 118 int run_helper_thread(int (*proc)(void *), void *arg, unsigned int flags,
 119                       unsigned long *stack_out)
 120 {
 121         unsigned long stack, sp;
 122         int pid, status, err;
 123
 124         stack = alloc_stack(0, __uml_cant_sleep());
 125         if (stack == 0)
 126                 return -ENOMEM;
 127
 128         sp = stack + UM_KERN_PAGE_SIZE;
 129         pid = clone(proc, (void *) sp, flags, arg);
 130         if (pid < 0) {
 131                 err = -errno;
 132                 printk(UM_KERN_ERR "run_helper_thread : clone failed, "
 133                        "errno = %d\n", errno);
 134                 return err;
 135         }
 136         if (stack_out == NULL) {
 137                 CATCH_EINTR(pid = waitpid(pid, &status, __WALL));
 138                 if (pid < 0) {
 139                         err = -errno;
 140                         printk(UM_KERN_ERR "run_helper_thread - wait failed, "
 141                                "errno = %d\n", errno);
 142                         pid = err;
 143                 }
 144                 if (!WIFEXITED(status) || (WEXITSTATUS(status) != 0))
 145                         printk(UM_KERN_ERR "run_helper_thread - thread "
 146                                "returned status 0x%x\n", status);
 147                 free_stack(stack, 0);
 148         } else
 149                 *stack_out = stack;
 150         return pid;
 151 }
 152
 153 int helper_wait(int pid)
 154 {
 155         int ret, status;
 156         int wflags = __WALL;
 157
 158         CATCH_EINTR(ret = waitpid(pid, &status, wflags));
 159         if (ret < 0) {
 160                 printk(UM_KERN_ERR "helper_wait : waitpid process %d failed, "
 161                        "errno = %d\n", pid, errno);
 162                 return -errno;
 163         } else if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
 164                 printk(UM_KERN_ERR "helper_wait : process %d exited with "
 165                        "status 0x%x\n", pid, status);
 166                 return -ECHILD;
 167         } else
 168                 return 0;
 169 }