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 <sys/signal.h>
  12 #include <sys/wait.h>
  13 #include "user.h"
  14 #include "kern_util.h"
  15 #include "user_util.h"
  16 #include "os.h"
  17
  18 struct helper_data {
  19         void (*pre_exec)(void*);
  20         void *pre_data;
  21         char **argv;
  22         int fd;
  23 };
  24
  25 /* Debugging aid, changed only from gdb */
  26 int helper_pause = 0;
  27
  28 static void helper_hup(int sig)
  29 {
  30 }
  31
  32 static int helper_child(void *arg)
  33 {
  34         struct helper_data *data = arg;
  35         char **argv = data->argv;
  36         int errval;
  37
  38         if (helper_pause){
  39                 signal(SIGHUP, helper_hup);
  40                 pause();
  41         }
  42         if (data->pre_exec != NULL)
  43                 (*data->pre_exec)(data->pre_data);
  44         execvp(argv[0], argv);
  45         errval = -errno;
  46         printk("helper_child - execve of '%s' failed - errno = %d\n", argv[0], errno);
  47         os_write_file(data->fd, &errval, sizeof(errval));
  48         kill(os_getpid(), SIGKILL);
  49         return 0;
  50 }
  51
  52 /* Returns either the pid of the child process we run or -E* on failure.
  53  * XXX The alloc_stack here breaks if this is called in the tracing thread, so
  54  * we need to receive a preallocated stack (a local buffer is ok). */
  55 int run_helper(void (*pre_exec)(void *), void *pre_data, char **argv,
  56                unsigned long *stack_out)
  57 {
  58         struct helper_data data;
  59         unsigned long stack, sp;
  60         int pid, fds[2], ret, n;
  61
  62         if ((stack_out != NULL) && (*stack_out != 0))
  63                 stack = *stack_out;
  64         else
  65                 stack = alloc_stack(0, __cant_sleep());
  66         if (stack == 0)
  67                 return -ENOMEM;
  68
  69         ret = os_pipe(fds, 1, 0);
  70         if (ret < 0) {
  71                 printk("run_helper : pipe failed, ret = %d\n", -ret);
  72                 goto out_free;
  73         }
  74
  75         ret = os_set_exec_close(fds[1], 1);
  76         if (ret < 0) {
  77                 printk("run_helper : setting FD_CLOEXEC failed, ret = %d\n",
  78                        -ret);
  79                 goto out_close;
  80         }
  81
  82         sp = stack + page_size() - sizeof(void *);
  83         data.pre_exec = pre_exec;
  84         data.pre_data = pre_data;
  85         data.argv = argv;
  86         data.fd = fds[1];
  87         pid = clone(helper_child, (void *) sp, CLONE_VM | SIGCHLD, &data);
  88         if (pid < 0) {
  89                 ret = -errno;
  90                 printk("run_helper : clone failed, errno = %d\n", errno);
  91                 goto out_close;
  92         }
  93
  94         close(fds[1]);
  95         fds[1] = -1;
  96
  97         /* Read the errno value from the child, if the exec failed, or get 0 if
  98          * the exec succeeded because the pipe fd was set as close-on-exec. */
  99         n = os_read_file(fds[0], &ret, sizeof(ret));
 100         if (n == 0) {
 101                 ret = pid;
 102         } else {
 103                 if (n < 0) {
 104                         printk("run_helper : read on pipe failed, ret = %d\n",
 105                                -n);
 106                         ret = n;
 107                         kill(pid, SIGKILL);
 108                 }
 109                 CATCH_EINTR(waitpid(pid, NULL, 0));
 110         }
 111
 112 out_close:
 113         if (fds[1] != -1)
 114                 close(fds[1]);
 115         close(fds[0]);
 116 out_free:
 117         if ((stack_out == NULL) || (*stack_out == 0))
 118                 free_stack(stack, 0);
 119         return ret;
 120 }
 121
 122 int run_helper_thread(int (*proc)(void *), void *arg, unsigned int flags,
 123                       unsigned long *stack_out, int stack_order)
 124 {
 125         unsigned long stack, sp;
 126         int pid, status, err;
 127
 128         stack = alloc_stack(stack_order, __cant_sleep());
 129         if (stack == 0)
 130                 return -ENOMEM;
 131
 132         sp = stack + (page_size() << stack_order) - sizeof(void *);
 133         pid = clone(proc, (void *) sp, flags | SIGCHLD, arg);
 134         if (pid < 0) {
 135                 err = -errno;
 136                 printk("run_helper_thread : clone failed, errno = %d\n",
 137                        errno);
 138                 return err;
 139         }
 140         if (stack_out == NULL) {
 141                 CATCH_EINTR(pid = waitpid(pid, &status, 0));
 142                 if (pid < 0) {
 143                         err = -errno;
 144                         printk("run_helper_thread - wait failed, errno = %d\n",
 145                                errno);
 146                         pid = err;
 147                 }
 148                 if (!WIFEXITED(status) || (WEXITSTATUS(status) != 0))
 149                         printk("run_helper_thread - thread returned status "
 150                                "0x%x\n", status);
 151                 free_stack(stack, stack_order);
 152         } else
 153                 *stack_out = stack;
 154         return pid;
 155 }
 156
 157 int helper_wait(int pid)
 158 {
 159         int ret;
 160
 161         CATCH_EINTR(ret = waitpid(pid, NULL, WNOHANG));
 162         if (ret < 0) {
 163                 ret = -errno;
 164                 printk("helper_wait : waitpid failed, errno = %d\n", errno);
 165         }
 166         return ret;
 167 }