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