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 "user_util.h"
  17 #include "os.h"
  18 #include "um_malloc.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 /* Debugging aid, changed only from gdb */
  29 int helper_pause = 0;
  30
  31 static void helper_hup(int sig)
  32 {
  33 }
  34
  35 static int helper_child(void *arg)
  36 {
  37         struct helper_data *data = arg;
  38         char **argv = data->argv;
  39         int errval;
  40
  41         if (helper_pause){
  42                 signal(SIGHUP, helper_hup);
  43                 pause();
  44         }
  45         if (data->pre_exec != NULL)
  46                 (*data->pre_exec)(data->pre_data);
  47         errval = execvp_noalloc(data->buf, argv[0], argv);
  48         printk("helper_child - execvp of '%s' failed - errno = %d\n", argv[0], -errval);
  49         os_write_file(data->fd, &errval, sizeof(errval));
  50         kill(os_getpid(), SIGKILL);
  51         return 0;
  52 }
  53
  54 /* Returns either the pid of the child process we run or -E* on failure.
  55  * XXX The alloc_stack here breaks if this is called in the tracing thread, so
  56  * we need to receive a preallocated stack (a local buffer is ok). */
  57 int run_helper(void (*pre_exec)(void *), void *pre_data, char **argv,
  58                unsigned long *stack_out)
  59 {
  60         struct helper_data data;
  61         unsigned long stack, sp;
  62         int pid, fds[2], ret, n;
  63
  64         if ((stack_out != NULL) && (*stack_out != 0))
  65                 stack = *stack_out;
  66         else
  67                 stack = alloc_stack(0, __cant_sleep());
  68         if (stack == 0)
  69                 return -ENOMEM;
  70
  71         ret = os_pipe(fds, 1, 0);
  72         if (ret < 0) {
  73                 printk("run_helper : pipe failed, ret = %d\n", -ret);
  74                 goto out_free;
  75         }
  76
  77         ret = os_set_exec_close(fds[1], 1);
  78         if (ret < 0) {
  79                 printk("run_helper : setting FD_CLOEXEC failed, ret = %d\n",
  80                        -ret);
  81                 goto out_close;
  82         }
  83
  84         sp = stack + page_size() - sizeof(void *);
  85         data.pre_exec = pre_exec;
  86         data.pre_data = pre_data;
  87         data.argv = argv;
  88         data.fd = fds[1];
  89         data.buf = __cant_sleep() ? um_kmalloc_atomic(PATH_MAX) :
  90                                         um_kmalloc(PATH_MAX);
  91         pid = clone(helper_child, (void *) sp, CLONE_VM | SIGCHLD, &data);
  92         if (pid < 0) {
  93                 ret = -errno;
  94                 printk("run_helper : clone failed, errno = %d\n", errno);
  95                 goto out_free2;
  96         }
  97
  98         close(fds[1]);
  99         fds[1] = -1;
 100
 101         /* Read the errno value from the child, if the exec failed, or get 0 if
 102          * the exec succeeded because the pipe fd was set as close-on-exec. */
 103         n = os_read_file(fds[0], &ret, sizeof(ret));
 104         if (n == 0) {
 105                 ret = pid;
 106         } else {
 107                 if (n < 0) {
 108                         printk("run_helper : read on pipe failed, ret = %d\n",
 109                                -n);
 110                         ret = n;
 111                         kill(pid, SIGKILL);
 112                 }
 113                 CATCH_EINTR(waitpid(pid, NULL, 0));
 114         }
 115
 116 out_free2:
 117         kfree(data.buf);
 118 out_close:
 119         if (fds[1] != -1)
 120                 close(fds[1]);
 121         close(fds[0]);
 122 out_free:
 123         if ((stack_out == NULL) || (*stack_out == 0))
 124                 free_stack(stack, 0);
 125         return ret;
 126 }
 127
 128 int run_helper_thread(int (*proc)(void *), void *arg, unsigned int flags,
 129                       unsigned long *stack_out, int stack_order)
 130 {
 131         unsigned long stack, sp;
 132         int pid, status, err;
 133
 134         stack = alloc_stack(stack_order, __cant_sleep());
 135         if (stack == 0)
 136                 return -ENOMEM;
 137
 138         sp = stack + (page_size() << stack_order) - sizeof(void *);
 139         pid = clone(proc, (void *) sp, flags | SIGCHLD, arg);
 140         if (pid < 0) {
 141                 err = -errno;
 142                 printk("run_helper_thread : clone failed, errno = %d\n",
 143                        errno);
 144                 return err;
 145         }
 146         if (stack_out == NULL) {
 147                 CATCH_EINTR(pid = waitpid(pid, &status, 0));
 148                 if (pid < 0) {
 149                         err = -errno;
 150                         printk("run_helper_thread - wait failed, errno = %d\n",
 151                                errno);
 152                         pid = err;
 153                 }
 154                 if (!WIFEXITED(status) || (WEXITSTATUS(status) != 0))
 155                         printk("run_helper_thread - thread returned status "
 156                                "0x%x\n", status);
 157                 free_stack(stack, stack_order);
 158         } else
 159                 *stack_out = stack;
 160         return pid;
 161 }
 162
 163 int helper_wait(int pid)
 164 {
 165         int ret;
 166
 167         CATCH_EINTR(ret = waitpid(pid, NULL, WNOHANG));
 168         if (ret < 0) {
 169                 ret = -errno;
 170                 printk("helper_wait : waitpid failed, errno = %d\n", errno);
 171         }
 172         return ret;
 173 }