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                unsigned long *stack_out)
  49 {
  50         struct helper_data data;
  51         unsigned long stack, sp;
  52         int pid, fds[2], ret, n;
  53
  54         if ((stack_out != NULL) && (*stack_out != 0))
  55                 stack = *stack_out;
  56         else
  57                 stack = alloc_stack(0, __cant_sleep());
  58         if (stack == 0)
  59                 return -ENOMEM;
  60
  61         ret = os_pipe(fds, 1, 0);
  62         if (ret < 0) {
  63                 printk("run_helper : pipe failed, ret = %d\n", -ret);
  64                 goto out_free;
  65         }
  66
  67         ret = os_set_exec_close(fds[1], 1);
  68         if (ret < 0) {
  69                 printk("run_helper : setting FD_CLOEXEC failed, ret = %d\n",
  70                        -ret);
  71                 goto out_close;
  72         }
  73
  74         sp = stack + UM_KERN_PAGE_SIZE - sizeof(void *);
  75         data.pre_exec = pre_exec;
  76         data.pre_data = pre_data;
  77         data.argv = argv;
  78         data.fd = fds[1];
  79         data.buf = __cant_sleep() ? um_kmalloc_atomic(PATH_MAX) :
  80                                         um_kmalloc(PATH_MAX);
  81         pid = clone(helper_child, (void *) sp, CLONE_VM | SIGCHLD, &data);
  82         if (pid < 0) {
  83                 ret = -errno;
  84                 printk("run_helper : clone failed, errno = %d\n", errno);
  85                 goto out_free2;
  86         }
  87
  88         close(fds[1]);
  89         fds[1] = -1;
  90
  91         /*
  92          * Read the errno value from the child, if the exec failed, or get 0 if
  93          * the exec succeeded because the pipe fd was set as close-on-exec.
  94          */
  95         n = read(fds[0], &ret, sizeof(ret));
  96         if (n == 0) {
  97                 ret = pid;
  98         } else {
  99                 if (n < 0) {
 100                         n = -errno;
 101                         printk("run_helper : read on pipe failed, ret = %d\n",
 102                                -n);
 103                         ret = n;
 104                         kill(pid, SIGKILL);
 105                 }
 106                 CATCH_EINTR(waitpid(pid, NULL, 0));
 107         }
 108
 109 out_free2:
 110         kfree(data.buf);
 111 out_close:
 112         if (fds[1] != -1)
 113                 close(fds[1]);
 114         close(fds[0]);
 115 out_free:
 116         if ((stack_out == NULL) || (*stack_out == 0))
 117                 free_stack(stack, 0);
 118         return ret;
 119 }
 120
 121 int run_helper_thread(int (*proc)(void *), void *arg, unsigned int flags,
 122                       unsigned long *stack_out, int stack_order)
 123 {
 124         unsigned long stack, sp;
 125         int pid, status, err;
 126
 127         stack = alloc_stack(stack_order, __cant_sleep());
 128         if (stack == 0)
 129                 return -ENOMEM;
 130
 131         sp = stack + (UM_KERN_PAGE_SIZE << stack_order) - sizeof(void *);
 132         pid = clone(proc, (void *) sp, flags | SIGCHLD, arg);
 133         if (pid < 0) {
 134                 err = -errno;
 135                 printk("run_helper_thread : clone failed, errno = %d\n",
 136                        errno);
 137                 return err;
 138         }
 139         if (stack_out == NULL) {
 140                 CATCH_EINTR(pid = waitpid(pid, &status, 0));
 141                 if (pid < 0) {
 142                         err = -errno;
 143                         printk("run_helper_thread - wait failed, errno = %d\n",
 144                                errno);
 145                         pid = err;
 146                 }
 147                 if (!WIFEXITED(status) || (WEXITSTATUS(status) != 0))
 148                         printk("run_helper_thread - thread returned status "
 149                                "0x%x\n", status);
 150                 free_stack(stack, stack_order);
 151         } else
 152                 *stack_out = stack;
 153         return pid;
 154 }
 155
 156 int helper_wait(int pid)
 157 {
 158         int ret;
 159
 160         CATCH_EINTR(ret = waitpid(pid, NULL, WNOHANG));
 161         if (ret < 0) {
 162                 ret = -errno;
 163                 printk("helper_wait : waitpid failed, errno = %d\n", errno);
 164         }
 165         return ret;
 166 }