273 lines
8.0 KiB
C
273 lines
8.0 KiB
C
/*
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* Copyright © 2014 Red Hat, Inc.
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice (including the next
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* paragraph) shall be included in all copies or substantial portions of the
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* Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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* DEALINGS IN THE SOFTWARE.
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*
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* Author: Hans de Goede <hdegoede@redhat.com>
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*/
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#include "dix-config.h"
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#include <errno.h>
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#include <fcntl.h>
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#include <limits.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/ioctl.h>
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#include <sys/stat.h>
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#include <sys/types.h>
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#if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
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#include <sys/consio.h>
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#endif
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#include <unistd.h>
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#include <drm.h>
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#include <xf86drm.h> /* For DRM_DEV_NAME */
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#define CONFIG_FILE SYSCONFDIR "/X11/Xwrapper.config"
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static const char *progname;
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enum { ROOT_ONLY, CONSOLE_ONLY, ANYBODY };
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/* KISS non locale / LANG parsing isspace version */
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static int is_space(char c)
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{
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return c == ' ' || c == '\t' || c == '\n';
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}
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static char *strip(char *s)
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{
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int i;
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/* Strip leading whitespace */
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while (s[0] && is_space(s[0]))
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s++;
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/* Strip trailing whitespace */
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i = strlen(s) - 1;
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while (i >= 0 && is_space(s[i])) {
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s[i] = 0;
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i--;
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}
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return s;
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}
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static void parse_config(int *allowed, int *needs_root_rights)
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{
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FILE *f;
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char buf[1024];
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char *stripped, *equals, *key, *value;
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int line = 0;
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f = fopen(CONFIG_FILE, "r");
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if (!f)
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return;
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while (fgets(buf, sizeof(buf), f)) {
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line++;
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/* Skip comments and empty lines */
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stripped = strip(buf);
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if (stripped[0] == '#' || stripped[0] == 0)
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continue;
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/* Split in a key + value pair */
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equals = strchr(stripped, '=');
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if (!equals) {
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fprintf(stderr, "%s: Syntax error at %s line %d\n", progname,
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CONFIG_FILE, line);
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exit(1);
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}
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*equals = 0;
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key = strip(stripped); /* To remove trailing whitespace from key */
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value = strip(equals + 1); /* To remove leading whitespace from val */
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if (!key[0]) {
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fprintf(stderr, "%s: Missing key at %s line %d\n", progname,
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CONFIG_FILE, line);
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exit(1);
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}
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if (!value[0]) {
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fprintf(stderr, "%s: Missing value at %s line %d\n", progname,
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CONFIG_FILE, line);
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exit(1);
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}
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/* And finally process */
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if (strcmp(key, "allowed_users") == 0) {
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if (strcmp(value, "rootonly") == 0)
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*allowed = ROOT_ONLY;
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else if (strcmp(value, "console") == 0)
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*allowed = CONSOLE_ONLY;
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else if (strcmp(value, "anybody") == 0)
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*allowed = ANYBODY;
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else {
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fprintf(stderr,
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"%s: Invalid value '%s' for 'allowed_users' at %s line %d\n",
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progname, value, CONFIG_FILE, line);
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exit(1);
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}
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}
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else if (strcmp(key, "needs_root_rights") == 0) {
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if (strcmp(value, "yes") == 0)
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*needs_root_rights = 1;
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else if (strcmp(value, "no") == 0)
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*needs_root_rights = 0;
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else if (strcmp(value, "auto") == 0)
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*needs_root_rights = -1;
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else {
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fprintf(stderr,
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"%s: Invalid value '%s' for 'needs_root_rights' at %s line %d\n",
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progname, value, CONFIG_FILE, line);
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exit(1);
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}
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}
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else if (strcmp(key, "nice_value") == 0) {
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/* Backward compatibility with older Debian Xwrapper, ignore */
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}
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else {
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fprintf(stderr, "%s: Invalid key '%s' at %s line %d\n", key,
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progname, CONFIG_FILE, line);
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exit(1);
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}
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}
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fclose(f);
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}
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static int on_console(int fd)
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{
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#if defined(__linux__)
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struct stat st;
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int r;
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r = fstat(fd, &st);
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if (r == 0 && S_ISCHR(st.st_mode) && major(st.st_rdev) == 4)
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return 1;
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#elif defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
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int idx;
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if (ioctl(fd, VT_GETINDEX, &idx) != -1)
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return 1;
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#else
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#warning This program needs porting to your kernel.
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static int seen;
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if (!seen) {
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fprintf(stderr, "%s: Unable to determine if running on a console\n",
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progname);
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seen = 1;
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}
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#endif
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return 0;
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}
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int main(int argc, char *argv[])
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{
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struct drm_mode_card_res res;
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char buf[PATH_MAX];
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int i, r, fd;
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int kms_cards = 0;
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int total_cards = 0;
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int allowed = CONSOLE_ONLY;
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int needs_root_rights = -1;
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progname = argv[0];
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parse_config(&allowed, &needs_root_rights);
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/* For non root users check if they are allowed to run the X server */
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if (getuid() != 0) {
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switch (allowed) {
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case ROOT_ONLY:
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/* Already checked above */
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fprintf(stderr, "%s: Only root is allowed to run the X server\n", argv[0]);
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exit(1);
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break;
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case CONSOLE_ONLY:
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/* Some of stdin / stdout / stderr maybe redirected to a file */
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for (i = STDIN_FILENO; i <= STDERR_FILENO; i++) {
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if (on_console(i))
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break;
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}
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if (i > STDERR_FILENO) {
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fprintf(stderr, "%s: Only console users are allowed to run the X server\n", argv[0]);
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exit(1);
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}
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break;
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case ANYBODY:
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break;
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}
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}
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/* Detect if we need root rights, except when overriden by the config */
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if (needs_root_rights == -1) {
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for (i = 0; i < 16; i++) {
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snprintf(buf, sizeof(buf), DRM_DEV_NAME, DRM_DIR_NAME, i);
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fd = open(buf, O_RDWR);
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if (fd == -1)
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continue;
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total_cards++;
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memset(&res, 0, sizeof(struct drm_mode_card_res));
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r = ioctl(fd, DRM_IOCTL_MODE_GETRESOURCES, &res);
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if (r == 0 && res.count_connectors > 0)
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kms_cards++;
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close(fd);
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}
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}
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/* If we've found cards, and all cards support kms, drop root rights */
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if (needs_root_rights == 0 || (total_cards && kms_cards == total_cards)) {
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gid_t realgid = getgid();
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uid_t realuid = getuid();
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if (setresgid(-1, realgid, realgid) != 0) {
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fprintf(stderr, "%s: Could not drop setgid privileges: %s\n",
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progname, strerror(errno));
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exit(1);
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}
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if (setresuid(-1, realuid, realuid) != 0) {
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fprintf(stderr, "%s: Could not drop setuid privileges: %s\n",
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progname, strerror(errno));
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exit(1);
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}
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}
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snprintf(buf, sizeof(buf), "%s/Xorg", SUID_WRAPPER_DIR);
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/* Check if the server is executable by our real uid */
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if (access(buf, X_OK) != 0) {
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fprintf(stderr, "%s: Missing execute permissions for %s: %s\n",
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progname, buf, strerror(errno));
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exit(1);
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}
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argv[0] = buf;
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(void) execv(argv[0], argv);
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fprintf(stderr, "%s: Failed to execute %s: %s\n",
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progname, buf, strerror(errno));
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exit(1);
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}
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