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#define _POSIX_C_SOURCE 200809L
#include <errno.h>
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/sysmacros.h>
#include <sys/wait.h>
#include <xf86drm.h>
#include <linux/major.h>
#include <wlr/util/log.h>
#include "session/direct-ipc.h"
enum { DRM_MAJOR = 226 };
#ifdef HAS_LIBCAP
#include <sys/capability.h>
static bool have_permissions(void) {
cap_t cap = cap_get_proc();
cap_flag_value_t val;
if (!cap || cap_get_flag(cap, CAP_SYS_ADMIN, CAP_PERMITTED, &val) || val != CAP_SET) {
wlr_log(L_ERROR, "Do not have CAP_SYS_ADMIN; cannot become DRM master");
cap_free(cap);
return false;
}
cap_free(cap);
return true;
}
#else
static bool have_permissions(void) {
if (geteuid() != 0) {
wlr_log(L_ERROR, "Do not have root privileges; cannot become DRM master");
return false;
}
return true;
}
#endif
static void send_msg(int sock, int fd, void *buf, size_t buf_len) {
char control[CMSG_SPACE(sizeof(fd))] = {0};
struct iovec iovec = { .iov_base = buf, .iov_len = buf_len };
struct msghdr msghdr = {0};
if (buf) {
msghdr.msg_iov = &iovec;
msghdr.msg_iovlen = 1;
}
if (fd >= 0) {
msghdr.msg_control = &control;
msghdr.msg_controllen = sizeof(control);
struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msghdr);
*cmsg = (struct cmsghdr) {
.cmsg_level = SOL_SOCKET,
.cmsg_type = SCM_RIGHTS,
.cmsg_len = CMSG_LEN(sizeof(fd)),
};
*(int *)CMSG_DATA(cmsg) = fd;
}
ssize_t ret;
do {
ret = sendmsg(sock, &msghdr, 0);
} while (ret < 0 && errno == EINTR);
}
static ssize_t recv_msg(int sock, int *fd_out, void *buf, size_t buf_len) {
char control[CMSG_SPACE(sizeof(*fd_out))] = {0};
struct iovec iovec = { .iov_base = buf, .iov_len = buf_len };
struct msghdr msghdr = {0};
if (buf) {
msghdr.msg_iov = &iovec;
msghdr.msg_iovlen = 1;
}
if (fd_out) {
msghdr.msg_control = &control;
msghdr.msg_controllen = sizeof(control);
}
ssize_t ret;
do {
ret = recvmsg(sock, &msghdr, MSG_CMSG_CLOEXEC);
} while (ret < 0 && errno == EINTR);
if (fd_out) {
struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msghdr);
*fd_out = cmsg ? *(int *)CMSG_DATA(cmsg) : -1;
}
return ret;
}
enum msg_type {
MSG_OPEN,
MSG_SETMASTER,
MSG_DROPMASTER,
MSG_END,
};
struct msg {
enum msg_type type;
char path[256];
};
static void communicate(int sock) {
struct msg msg;
int drm_fd = -1;
bool running = true;
while (running && recv_msg(sock, &drm_fd, &msg, sizeof(msg)) >= 0) {
switch (msg.type) {
case MSG_OPEN:
errno = 0;
// These are the same flags that logind opens files with
int fd = open(msg.path, O_RDWR|O_CLOEXEC|O_NOCTTY|O_NONBLOCK);
int ret = errno;
if (fd == -1) {
goto error;
}
struct stat st;
if (fstat(fd, &st) < 0) {
ret = errno;
goto error;
}
uint32_t maj = major(st.st_rdev);
if (maj != INPUT_MAJOR && maj != DRM_MAJOR) {
ret = ENOTSUP;
goto error;
}
if (maj == DRM_MAJOR && drmSetMaster(fd)) {
ret = errno;
}
error:
send_msg(sock, ret ? -1 : fd, &ret, sizeof(ret));
close(fd);
break;
case MSG_SETMASTER:
drmSetMaster(drm_fd);
close(drm_fd);
send_msg(sock, -1, NULL, 0);
break;
case MSG_DROPMASTER:
drmDropMaster(drm_fd);
close(drm_fd);
send_msg(sock, -1, NULL, 0);
break;
case MSG_END:
running = false;
send_msg(sock, -1, NULL, 0);
break;
}
}
close(sock);
}
int direct_ipc_open(int sock, const char *path) {
struct msg msg = { .type = MSG_OPEN };
snprintf(msg.path, sizeof(msg.path), "%s", path);
send_msg(sock, -1, &msg, sizeof(msg));
int fd, err;
recv_msg(sock, &fd, &err, sizeof(err));
return err ? -err : fd;
}
void direct_ipc_setmaster(int sock, int fd) {
struct msg msg = { .type = MSG_SETMASTER };
send_msg(sock, fd, &msg, sizeof(msg));
recv_msg(sock, NULL, NULL, 0);
}
void direct_ipc_dropmaster(int sock, int fd) {
struct msg msg = { .type = MSG_DROPMASTER };
send_msg(sock, fd, &msg, sizeof(msg));
recv_msg(sock, NULL, NULL, 0);
}
void direct_ipc_finish(int sock, pid_t pid) {
struct msg msg = { .type = MSG_END };
send_msg(sock, -1, &msg, sizeof(msg));
recv_msg(sock, NULL, NULL, 0);
waitpid(pid, NULL, 0);
}
int direct_ipc_start(pid_t *pid_out) {
if (!have_permissions()) {
return -1;
}
int sock[2];
if (socketpair(AF_UNIX, SOCK_SEQPACKET, 0, sock) < 0) {
wlr_log_errno(L_ERROR, "Failed to create socket pair");
return -1;
}
pid_t pid = fork();
if (pid < 0) {
wlr_log_errno(L_ERROR, "Fork failed");
close(sock[0]);
close(sock[1]);
return -1;
} else if (pid == 0) {
close(sock[0]);
communicate(sock[1]);
_Exit(0);
}
close(sock[1]);
*pid_out = pid;
return sock[0];
}
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