linux/arch/um/os-Linux/helper.c
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   1/*
   2 * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
   3 * Licensed under the GPL
   4 */
   5
   6#include <stdlib.h>
   7#include <unistd.h>
   8#include <errno.h>
   9#include <sched.h>
  10#include <linux/limits.h>
  11#include <sys/socket.h>
  12#include <sys/wait.h>
  13#include "kern_util.h"
  14#include "os.h"
  15#include "um_malloc.h"
  16
  17struct helper_data {
  18        void (*pre_exec)(void*);
  19        void *pre_data;
  20        char **argv;
  21        int fd;
  22        char *buf;
  23};
  24
  25static int helper_child(void *arg)
  26{
  27        struct helper_data *data = arg;
  28        char **argv = data->argv;
  29        int err, ret;
  30
  31        if (data->pre_exec != NULL)
  32                (*data->pre_exec)(data->pre_data);
  33        err = execvp_noalloc(data->buf, argv[0], argv);
  34
  35        /* If the exec succeeds, we don't get here */
  36        CATCH_EINTR(ret = write(data->fd, &err, sizeof(err)));
  37
  38        return 0;
  39}
  40
  41/* Returns either the pid of the child process we run or -E* on failure. */
  42int run_helper(void (*pre_exec)(void *), void *pre_data, char **argv)
  43{
  44        struct helper_data data;
  45        unsigned long stack, sp;
  46        int pid, fds[2], ret, n;
  47
  48        stack = alloc_stack(0, __cant_sleep());
  49        if (stack == 0)
  50                return -ENOMEM;
  51
  52        ret = socketpair(AF_UNIX, SOCK_STREAM, 0, fds);
  53        if (ret < 0) {
  54                ret = -errno;
  55                printk(UM_KERN_ERR "run_helper : pipe failed, errno = %d\n",
  56                       errno);
  57                goto out_free;
  58        }
  59
  60        ret = os_set_exec_close(fds[1]);
  61        if (ret < 0) {
  62                printk(UM_KERN_ERR "run_helper : setting FD_CLOEXEC failed, "
  63                       "ret = %d\n", -ret);
  64                goto out_close;
  65        }
  66
  67        sp = stack + UM_KERN_PAGE_SIZE - sizeof(void *);
  68        data.pre_exec = pre_exec;
  69        data.pre_data = pre_data;
  70        data.argv = argv;
  71        data.fd = fds[1];
  72        data.buf = __cant_sleep() ? uml_kmalloc(PATH_MAX, UM_GFP_ATOMIC) :
  73                                        uml_kmalloc(PATH_MAX, UM_GFP_KERNEL);
  74        pid = clone(helper_child, (void *) sp, CLONE_VM, &data);
  75        if (pid < 0) {
  76                ret = -errno;
  77                printk(UM_KERN_ERR "run_helper : clone failed, errno = %d\n",
  78                       errno);
  79                goto out_free2;
  80        }
  81
  82        close(fds[1]);
  83        fds[1] = -1;
  84
  85        /*
  86         * Read the errno value from the child, if the exec failed, or get 0 if
  87         * the exec succeeded because the pipe fd was set as close-on-exec.
  88         */
  89        n = read(fds[0], &ret, sizeof(ret));
  90        if (n == 0) {
  91                ret = pid;
  92        } else {
  93                if (n < 0) {
  94                        n = -errno;
  95                        printk(UM_KERN_ERR "run_helper : read on pipe failed, "
  96                               "ret = %d\n", -n);
  97                        ret = n;
  98                }
  99                CATCH_EINTR(waitpid(pid, NULL, __WCLONE));
 100        }
 101
 102out_free2:
 103        kfree(data.buf);
 104out_close:
 105        if (fds[1] != -1)
 106                close(fds[1]);
 107        close(fds[0]);
 108out_free:
 109        free_stack(stack, 0);
 110        return ret;
 111}
 112
 113int run_helper_thread(int (*proc)(void *), void *arg, unsigned int flags,
 114                      unsigned long *stack_out)
 115{
 116        unsigned long stack, sp;
 117        int pid, status, err;
 118
 119        stack = alloc_stack(0, __cant_sleep());
 120        if (stack == 0)
 121                return -ENOMEM;
 122
 123        sp = stack + UM_KERN_PAGE_SIZE - sizeof(void *);
 124        pid = clone(proc, (void *) sp, flags, arg);
 125        if (pid < 0) {
 126                err = -errno;
 127                printk(UM_KERN_ERR "run_helper_thread : clone failed, "
 128                       "errno = %d\n", errno);
 129                return err;
 130        }
 131        if (stack_out == NULL) {
 132                CATCH_EINTR(pid = waitpid(pid, &status, __WCLONE));
 133                if (pid < 0) {
 134                        err = -errno;
 135                        printk(UM_KERN_ERR "run_helper_thread - wait failed, "
 136                               "errno = %d\n", errno);
 137                        pid = err;
 138                }
 139                if (!WIFEXITED(status) || (WEXITSTATUS(status) != 0))
 140                        printk(UM_KERN_ERR "run_helper_thread - thread "
 141                               "returned status 0x%x\n", status);
 142                free_stack(stack, 0);
 143        } else
 144                *stack_out = stack;
 145        return pid;
 146}
 147
 148int helper_wait(int pid)
 149{
 150        int ret, status;
 151        int wflags = __WCLONE;
 152
 153        CATCH_EINTR(ret = waitpid(pid, &status, wflags));
 154        if (ret < 0) {
 155                printk(UM_KERN_ERR "helper_wait : waitpid process %d failed, "
 156                       "errno = %d\n", pid, errno);
 157                return -errno;
 158        } else if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
 159                printk(UM_KERN_ERR "helper_wait : process %d exited with "
 160                       "status 0x%x\n", pid, status);
 161                return -ECHILD;
 162        } else
 163                return 0;
 164}
 165
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