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], -errval);
  38         os_write_file(data->fd, &errval, sizeof(errval));
  39         kill(os_getpid(), SIGKILL);
  40         return 0;
  41 }
  42
  43 /* Returns either the pid of the child process we run or -E* on failure.
  44  * XXX The alloc_stack here breaks if this is called in the tracing thread, so
  45  * we need to receive a preallocated stack (a local buffer is ok). */
  46 int run_helper(void (*pre_exec)(void *), void *pre_data, char **argv,
  47                unsigned long *stack_out)
  48 {
  49         struct helper_data data;
  50         unsigned long stack, sp;
  51         int pid, fds[2], ret, n;
  52
  53         if ((stack_out != NULL) && (*stack_out != 0))
  54                 stack = *stack_out;
  55         else
  56                 stack = alloc_stack(0, __cant_sleep());
  57         if (stack == 0)
  58                 return -ENOMEM;
  59
  60         ret = os_pipe(fds, 1, 0);
  61         if (ret < 0) {
  62                 printk("run_helper : pipe failed, ret = %d\n", -ret);
  63                 goto out_free;
  64         }
  65
  66         ret = os_set_exec_close(fds[1], 1);
  67         if (ret < 0) {
  68                 printk("run_helper : setting FD_CLOEXEC failed, ret = %d\n",
  69                        -ret);
  70                 goto out_close;
  71         }
  72
  73         sp = stack + UM_KERN_PAGE_SIZE - sizeof(void *);
  74         data.pre_exec = pre_exec;
  75         data.pre_data = pre_data;
  76         data.argv = argv;
  77         data.fd = fds[1];
  78         data.buf = __cant_sleep() ? um_kmalloc_atomic(PATH_MAX) :
  79                                         um_kmalloc(PATH_MAX);
  80         pid = clone(helper_child, (void *) sp, CLONE_VM | SIGCHLD, &data);
  81         if (pid < 0) {
  82                 ret = -errno;
  83                 printk("run_helper : clone failed, errno = %d\n", errno);
  84                 goto out_free2;
  85         }
  86
  87         close(fds[1]);
  88         fds[1] = -1;
  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         n = os_read_file(fds[0], &ret, sizeof(ret));
  93         if (n == 0) {
  94                 ret = pid;
  95         } else {
  96                 if (n < 0) {
  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         if ((stack_out == NULL) || (*stack_out == 0))
 113                 free_stack(stack, 0);
 114         return ret;
 115 }
 116
 117 int run_helper_thread(int (*proc)(void *), void *arg, unsigned int flags,
 118                       unsigned long *stack_out, int stack_order)
 119 {
 120         unsigned long stack, sp;
 121         int pid, status, err;
 122
 123         stack = alloc_stack(stack_order, __cant_sleep());
 124         if (stack == 0)
 125                 return -ENOMEM;
 126
 127         sp = stack + (UM_KERN_PAGE_SIZE << stack_order) - sizeof(void *);
 128         pid = clone(proc, (void *) sp, flags | SIGCHLD, arg);
 129         if (pid < 0) {
 130                 err = -errno;
 131                 printk("run_helper_thread : clone failed, errno = %d\n",
 132                        errno);
 133                 return err;
 134         }
 135         if (stack_out == NULL) {
 136                 CATCH_EINTR(pid = waitpid(pid, &status, 0));
 137                 if (pid < 0) {
 138                         err = -errno;
 139                         printk("run_helper_thread - wait failed, errno = %d\n",
 140                                errno);
 141                         pid = err;
 142                 }
 143                 if (!WIFEXITED(status) || (WEXITSTATUS(status) != 0))
 144                         printk("run_helper_thread - thread returned status "
 145                                "0x%x\n", status);
 146                 free_stack(stack, stack_order);
 147         } else
 148                 *stack_out = stack;
 149         return pid;
 150 }
 151
 152 int helper_wait(int pid)
 153 {
 154         int ret;
 155
 156         CATCH_EINTR(ret = waitpid(pid, NULL, WNOHANG));
 157         if (ret < 0) {
 158                 ret = -errno;
 159                 printk("helper_wait : waitpid failed, errno = %d\n", errno);
 160         }
 161         return ret;
 162 }