arch/um/kernel/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("execvp of '%s' failed - errno = %d\n", argv[0], errno);
  47         os_write_file(data->fd, &errval, sizeof(errval));
  48         os_kill_process(os_getpid(), 0);
  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 */
  54 int run_helper(void (*pre_exec)(void *), void *pre_data, char **argv,
  55                unsigned long *stack_out)
  56 {
  57         struct helper_data data;
  58         unsigned long stack, sp;
  59         int pid, fds[2], ret, n;
  60
  61         if((stack_out != NULL) && (*stack_out != 0))
  62                 stack = *stack_out;
  63         else stack = alloc_stack(0, um_in_interrupt());
  64         if(stack == 0)
  65                 return(-ENOMEM);
  66
  67         ret = os_pipe(fds, 1, 0);
  68         if(ret < 0){
  69                 printk("run_helper : pipe failed, ret = %d\n", -ret);
  70                 goto out_free;
  71         }
  72
  73         ret = os_set_exec_close(fds[1], 1);
  74         if(ret < 0){
  75                 printk("run_helper : setting FD_CLOEXEC failed, ret = %d\n",
  76                        -ret);
  77                 goto out_close;
  78         }
  79
  80         sp = stack + page_size() - sizeof(void *);
  81         data.pre_exec = pre_exec;
  82         data.pre_data = pre_data;
  83         data.argv = argv;
  84         data.fd = fds[1];
  85         pid = clone(helper_child, (void *) sp, CLONE_VM | SIGCHLD, &data);
  86         if(pid < 0){
  87                 printk("run_helper : clone failed, errno = %d\n", errno);
  88                 ret = -errno;
  89                 goto out_close;
  90         }
  91
  92         os_close_file(fds[1]);
  93         fds[1] = -1;
  94
  95         /*Read the errno value from the child.*/
  96         n = os_read_file(fds[0], &ret, sizeof(ret));
  97         if(n < 0){
  98                 printk("run_helper : read on pipe failed, ret = %d\n", -n);
  99                 ret = n;
 100                 os_kill_process(pid, 1);
 101         }
 102         else if(n != 0){
 103                 CATCH_EINTR(n = waitpid(pid, NULL, 0));
 104                 ret = -errno;
 105         } else {
 106                 ret = pid;
 107         }
 108
 109 out_close:
 110         if (fds[1] != -1)
 111                 os_close_file(fds[1]);
 112         os_close_file(fds[0]);
 113 out_free:
 114         if(stack_out == NULL)
 115                 free_stack(stack, 0);
 116         else *stack_out = stack;
 117         return(ret);
 118 }
 119
 120 int run_helper_thread(int (*proc)(void *), void *arg, unsigned int flags,
 121                       unsigned long *stack_out, int stack_order)
 122 {
 123         unsigned long stack, sp;
 124         int pid, status;
 125
 126         stack = alloc_stack(stack_order, um_in_interrupt());
 127         if(stack == 0) return(-ENOMEM);
 128
 129         sp = stack + (page_size() << stack_order) - sizeof(void *);
 130         pid = clone(proc, (void *) sp, flags | SIGCHLD, arg);
 131         if(pid < 0){
 132                 printk("run_helper_thread : clone failed, errno = %d\n",
 133                        errno);
 134                 return(-errno);
 135         }
 136         if(stack_out == NULL){
 137                 CATCH_EINTR(pid = waitpid(pid, &status, 0));
 138                 if(pid < 0){
 139                         printk("run_helper_thread - wait failed, errno = %d\n",
 140                                errno);
 141                         pid = -errno;
 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         }
 148         else *stack_out = stack;
 149         return(pid);
 150 }
 151
 152 int helper_wait(int pid, int block)
 153 {
 154         int ret;
 155
 156         CATCH_EINTR(ret = waitpid(pid, NULL, WNOHANG));
 157         if(ret < 0){
 158                 printk("helper_wait : waitpid failed, errno = %d\n", errno);
 159                 return(-errno);
 160         }
 161         return(ret);
 162 }
 163
 164 /*
 165  * Overrides for Emacs so that we follow Linus's tabbing style.
 166  * Emacs will notice this stuff at the end of the file and automatically
 167  * adjust the settings for this buffer only.  This must remain at the end
 168  * of the file.
 169  * ---------------------------------------------------------------------------
 170  * Local variables:
 171  * c-file-style: "linux"
 172  * End:
 173  */