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terminal: Construct TTY paths correctly on FreeBSD

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FreeBSD TTY paths are contructed in the kernel using the %r formatter,
which in this case ends up being a base 32 encoding.

The base 32 implementation is taken more or less directly from wlroots
commit fc6c0ca12e94.
This commit is contained in:
Kenny Levinsen 2020-08-28 15:25:04 +00:00
parent 60a8e809b2
commit dbdce8a54b
1 changed files with 79 additions and 4 deletions
Download patch file Download diff file Expand all files Collapse all files

83
common/terminal.c
View file

@ -1,3 +1,4 @@
#include <assert.h>
#include <errno.h> #include <errno.h>
#include <fcntl.h> #include <fcntl.h>
#include <signal.h> #include <signal.h>
@ -10,7 +11,6 @@
#if defined(__linux__) #if defined(__linux__)
#include <linux/kd.h> #include <linux/kd.h>
#include <linux/vt.h> #include <linux/vt.h>
#define TTYF "/dev/tty%d"
#define K_ENABLE K_UNICODE #define K_ENABLE K_UNICODE
#define K_DISABLE K_OFF #define K_DISABLE K_OFF
#define FRSIG 0 #define FRSIG 0
@ -18,7 +18,6 @@
#include <sys/consio.h> #include <sys/consio.h>
#include <sys/kbio.h> #include <sys/kbio.h>
#include <termios.h> #include <termios.h>
#define TTYF "/dev/ttyv%d"
#define K_ENABLE K_XLATE #define K_ENABLE K_XLATE
#define K_DISABLE K_RAW #define K_DISABLE K_RAW
#define FRSIG SIGIO #define FRSIG SIGIO
@ -29,11 +28,87 @@
#include "log.h" #include "log.h"
#include "terminal.h" #include "terminal.h"
#define TTYPATHLEN 64 #define TTYPATHLEN 16
#if defined(__FreeBSD__)
static int get_tty_path(int tty, char path[static TTYPATHLEN]) {
assert(tty >= 0);
const char prefix[] = "/dev/ttyv";
const size_t prefix_len = sizeof(prefix) - 1;
strcpy(path, prefix);
// The FreeBSD tty name is constructed in the kernel as follows:
//
// static void
// vtterm_cnprobe(struct terminal *tm, struct consdev *cp)
// {
// ...
// struct vt_window *vw = tm->tm_softc;
// ...
// sprintf(cp->cn_name, "ttyv%r", VT_UNIT(vw));
// ...
// }
//
// With %r being a FreeBSD-internal radix formatter (seemingly set to
// base 32), and VT_UNIT expanding to the following to extract the
// internal VT number (which is one less than the external VT number):
//
// ((vw)->vw_device->vd_unit * VT_MAXWINDOWS + (vw)->vw_number)
//
// As the %r formatter is kernel-internal, we implement the base 32
// encoding ourselves below.
size_t offset = prefix_len;
if (tty == 0) {
path[offset++] = '0';
path[offset++] = '\0';
return 0;
}
const int base = 32;
for (int remaining = tty; remaining > 0; remaining /= base, offset++) {
// Return early if the buffer is too small.
if (offset + 1 >= TTYPATHLEN) {
errno = ENOMEM;
return -1;
}
const int value = remaining % base;
if (value >= 10) {
path[offset] = 'a' + value - 10;
} else {
path[offset] = '0' + value;
}
}
const size_t num_len = offset - prefix_len;
for (size_t i = 0; i < num_len / 2; i++) {
const size_t p1 = prefix_len + i;
const size_t p2 = offset - 1 - i;
const char tmp = path[p1];
path[p1] = path[p2];
path[p2] = tmp;
}
path[offset++] = '\0';
return 0;
}
#elif defined(__linux__)
static int get_tty_path(int tty, char path[static TTYPATHLEN]) {
assert(tty >= 0);
if (snprintf(path, TTYPATHLEN, "/dev/tty%d", tty) == -1) {
return -1;
}
return 0;
}
#else
#error Unsupported platform
#endif
int terminal_open(int vt) { int terminal_open(int vt) {
char path[TTYPATHLEN]; char path[TTYPATHLEN];
if (snprintf(path, TTYPATHLEN, TTYF, vt) == -1) { if (get_tty_path(vt, path) == -1) {
log_errorf("could not generate tty path: %s", strerror(errno)); log_errorf("could not generate tty path: %s", strerror(errno));
return -1; return -1;
} }