root/arch/um/os-Linux/helper.c

DEFINITIONS

1. helper_child
2. run_helper
3. run_helper_thread
4. helper_wait

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