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 <sys/socket.h>
  15 #include "user.h"
  16 #include "kern_util.h"
  17 #include "os.h"
  18 #include "um_malloc.h"
  19 #include "kern_constants.h"
  20
  21 struct helper_data {
  22         void (*pre_exec)(void*);
  23         void *pre_data;
  24         char **argv;
  25         int fd;
  26         char *buf;
  27 };
  28
  29 static int helper_child(void *arg)
  30 {
  31         struct helper_data *data = arg;
  32         char **argv = data->argv;
  33         int errval;
  34
  35         if (data->pre_exec != NULL)
  36                 (*data->pre_exec)(data->pre_data);
  37         errval = execvp_noalloc(data->buf, argv[0], argv);
  38         printk("helper_child - execvp of '%s' failed - errno = %d\n", argv[0],
  39                -errval);
  40         write(data->fd, &errval, sizeof(errval));
  41         kill(os_getpid(), SIGKILL);
  42         return 0;
  43 }
  44
  45 /* Returns either the pid of the child process we run or -E* on failure.
  46  * XXX The alloc_stack here breaks if this is called in the tracing thread, so
  47  * we need to receive a preallocated stack (a local buffer is ok). */
  48 int run_helper(void (*pre_exec)(void *), void *pre_data, char **argv)
  49 {
  50         struct helper_data data;
  51         unsigned long stack, sp;
  52         int pid, fds[2], ret, n;
  53
  54         stack = alloc_stack(0, __cant_sleep());
  55         if (stack == 0)
  56                 return -ENOMEM;
  57
  58         ret = socketpair(AF_UNIX, SOCK_STREAM, 0, fds);
  59         if (ret < 0) {
  60                 ret = -errno;
  61                 printk("run_helper : pipe failed, errno = %d\n", errno);
  62                 goto out_free;
  63         }
  64
  65         ret = os_set_exec_close(fds[1]);
  66         if (ret < 0) {
  67                 printk("run_helper : setting FD_CLOEXEC failed, ret = %d\n",
  68                        -ret);
  69                 goto out_close;
  70         }
  71
  72         sp = stack + UM_KERN_PAGE_SIZE - sizeof(void *);
  73         data.pre_exec = pre_exec;
  74         data.pre_data = pre_data;
  75         data.argv = argv;
  76         data.fd = fds[1];
  77         data.buf = __cant_sleep() ? kmalloc(PATH_MAX, UM_GFP_ATOMIC) :
  78                                         kmalloc(PATH_MAX, UM_GFP_KERNEL);
  79         pid = clone(helper_child, (void *) sp, CLONE_VM | SIGCHLD, &data);
  80         if (pid < 0) {
  81                 ret = -errno;
  82                 printk("run_helper : clone failed, errno = %d\n", errno);
  83                 goto out_free2;
  84         }
  85
  86         close(fds[1]);
  87         fds[1] = -1;
  88
  89         /*
  90          * Read the errno value from the child, if the exec failed, or get 0 if
  91          * the exec succeeded because the pipe fd was set as close-on-exec.
  92          */
  93         n = read(fds[0], &ret, sizeof(ret));
  94         if (n == 0) {
  95                 ret = pid;
  96         } else {
  97                 if (n < 0) {
  98                         n = -errno;
  99                         printk("run_helper : read on pipe failed, ret = %d\n",
 100                                -n);
 101                         ret = n;
 102                         kill(pid, SIGKILL);
 103                 }
 104                 CATCH_EINTR(waitpid(pid, NULL, 0));
 105         }
 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, __cant_sleep());
 125         if (stack == 0)
 126                 return -ENOMEM;
 127
 128         sp = stack + UM_KERN_PAGE_SIZE - sizeof(void *);
 129         pid = clone(proc, (void *) sp, flags | SIGCHLD, arg);
 130         if (pid < 0) {
 131                 err = -errno;
 132                 printk("run_helper_thread : clone failed, errno = %d\n",
 133                        errno);
 134                 return err;
 135         }
 136         if (stack_out == NULL) {
 137                 CATCH_EINTR(pid = waitpid(pid, &status, 0));
 138                 if (pid < 0) {
 139                         err = -errno;
 140                         printk("run_helper_thread - wait failed, errno = %d\n",
 141                                errno);
 142                         pid = err;
 143                 }
 144                 if (!WIFEXITED(status) || (WEXITSTATUS(status) != 0))
 145                         printk("run_helper_thread - thread returned status "
 146                                "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;
 156
 157         CATCH_EINTR(ret = waitpid(pid, NULL, WNOHANG));
 158         if (ret < 0) {
 159                 ret = -errno;
 160                 printk("helper_wait : waitpid failed, errno = %d\n", errno);
 161         }
 162         return ret;
 163 }