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1 | /* vi: set sw=4 ts=4: */
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2 | /*
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3 | * Utility routines.
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4 | *
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5 | * Copyright (C) many different people. If you wrote this, please
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6 | * acknowledge your work.
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7 | *
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8 | * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
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9 | */
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10 |
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11 | //#include <sys/ioctl.h>
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12 | #include "libbb.h"
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13 |
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14 |
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15 | /* From <linux/kd.h> */
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16 | enum { KDGKBTYPE = 0x4B33 }; /* get keyboard type */
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17 |
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18 |
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19 | static int open_a_console(const char *fnam)
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20 | {
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21 | int fd;
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22 |
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23 | /* try read-write */
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24 | fd = open(fnam, O_RDWR);
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25 |
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26 | /* if failed, try read-only */
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27 | if (fd < 0 && errno == EACCES)
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28 | fd = open(fnam, O_RDONLY);
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29 |
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30 | /* if failed, try write-only */
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31 | if (fd < 0 && errno == EACCES)
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32 | fd = open(fnam, O_WRONLY);
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33 |
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34 | return fd;
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35 | }
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36 |
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37 | /*
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38 | * Get an fd for use with kbd/console ioctls.
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39 | * We try several things because opening /dev/console will fail
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40 | * if someone else used X (which does a chown on /dev/console).
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41 | */
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42 |
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43 | int get_console_fd(void)
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44 | {
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45 | static const char *const console_names[] = {
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46 | DEV_CONSOLE, CURRENT_VC, CURRENT_TTY
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47 | };
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48 |
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49 | int fd;
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50 |
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51 | for (fd = 2; fd >= 0; fd--) {
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52 | int fd4name;
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53 | int choice_fd;
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54 | char arg;
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55 |
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56 | fd4name = open_a_console(console_names[fd]);
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57 | chk_std:
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58 | choice_fd = (fd4name >= 0 ? fd4name : fd);
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59 |
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60 | arg = 0;
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61 | if (ioctl(choice_fd, KDGKBTYPE, &arg) == 0)
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62 | return choice_fd;
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63 | if (fd4name >= 0) {
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64 | close(fd4name);
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65 | fd4name = -1;
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66 | goto chk_std;
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67 | }
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68 | }
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69 |
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70 | bb_error_msg("cannot get file descriptor referring to console");
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71 | return fd; /* total failure */
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72 | }
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