arch/um/os-Linux/helper.c

   1 /*
   2  * Copyright (C) 2002 Jeff Dike (jdike@karaya.com)
   3  * Licensed under the GPL
   4  */
   5
   6 #include <stdio.h>
   7 #include <stdlib.h>
   8 #include <unistd.h>
   9 #include <errno.h>
  10 #include <sched.h>
  11 #include <limits.h>
  12 #include <sys/signal.h>
  13 #include <sys/wait.h>
  14 #include "user.h"
  15 #include "kern_util.h"
  16 #include "os.h"
  17 #include "um_malloc.h"
  18 #include "kern_constants.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 errval;
  33
  34         if (data->pre_exec != NULL)
  35                 (*data->pre_exec)(data->pre_data);
  36         errval = execvp_noalloc(data->buf, argv[0], argv);
  37         printk("helper_child - execvp of '%s' failed - errno = %d\n", argv[0],
  38                -errval);
  39         write(data->fd, &errval, sizeof(errval));
  40         kill(os_getpid(), SIGKILL);
  41         return 0;
  42 }
  43
  44 /* Returns either the pid of the child process we run or -E* on failure.
  45  * XXX The alloc_stack here breaks if this is called in the tracing thread, so
  46  * we need to receive a preallocated stack (a local buffer is ok). */
  47 int run_helper(void (*pre_exec)(void *), void *pre_data, char **argv)
  48 {
  49         struct helper_data data;
  50         unsigned long stack, sp;
  51         int pid, fds[2], ret, n;
  52
  53         stack = alloc_stack(0, __cant_sleep());
  54         if (stack == 0)
  55                 return -ENOMEM;
  56
  57         ret = os_pipe(fds, 1, 0);
  58         if (ret < 0) {
  59                 printk("run_helper : pipe failed, ret = %d\n", -ret);
  60                 goto out_free;
  61         }
  62
  63         ret = os_set_exec_close(fds[1], 1);
  64         if (ret < 0) {
  65                 printk("run_helper : setting FD_CLOEXEC failed, ret = %d\n",
  66                        -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() ? kmalloc(PATH_MAX, UM_GFP_ATOMIC) :
  76                                         kmalloc(PATH_MAX, UM_GFP_KERNEL);
  77         pid = clone(helper_child, (void *) sp, CLONE_VM | SIGCHLD, &data);
  78         if (pid < 0) {
  79                 ret = -errno;
  80                 printk("run_helper : clone failed, errno = %d\n", 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("run_helper : read on pipe failed, ret = %d\n",
  98                                -n);
  99                         ret = n;
 100                         kill(pid, SIGKILL);
 101                 }
 102                 CATCH_EINTR(waitpid(pid, NULL, 0));
 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 | SIGCHLD, arg);
 128         if (pid < 0) {
 129                 err = -errno;
 130                 printk("run_helper_thread : clone failed, errno = %d\n",
 131                        errno);
 132                 return err;
 133         }
 134         if (stack_out == NULL) {
 135                 CATCH_EINTR(pid = waitpid(pid, &status, 0));
 136                 if (pid < 0) {
 137                         err = -errno;
 138                         printk("run_helper_thread - wait failed, errno = %d\n",
 139                                errno);
 140                         pid = err;
 141                 }
 142                 if (!WIFEXITED(status) || (WEXITSTATUS(status) != 0))
 143                         printk("run_helper_thread - thread returned status "
 144                                "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;
 154
 155         CATCH_EINTR(ret = waitpid(pid, NULL, WNOHANG));
 156         if (ret < 0) {
 157                 ret = -errno;
 158                 printk("helper_wait : waitpid failed, errno = %d\n", errno);
 159         }
 160         return ret;
 161 }