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Takashi Yano 10477d95ec Cygwin: console: Fix race issue on allocating console simultaneously.
Previously, if two or more processes request to allocate a console at
the same time, the same device number could be accidentally allocated.
This patch fixes the issue by creating a named mutex (input_mutex) and
checking if GetLastError() is ERROR_ALREADY_EXIST or not to ensure
the unit number will be allocated in an atomic way. Thanks to this,
EnumWindow() is not necessary anymore to scan console units.

This also makes minor device numbers unique and console devices visible
across sessions. This disallows duplicated device number for different
sessions, so the MAX_CONS_DEV has been increased from 64 to 128.

Additionally, the console allocation and scanning will be faster as
a side effect of eliminating EnumWindows().

Fixes: 3721a756b0d8 ("Cygwin: console: Make the console accessible from other terminals.")
Signed-off-by: Takashi Yano <takashi.yano@nifty.ne.jp>
2024-07-09 00:01:22 +09:00

220 lines
5.6 KiB
C++

/* tty.h: shared tty info for cygwin
This file is part of Cygwin.
This software is a copyrighted work licensed under the terms of the
Cygwin license. Please consult the file "CYGWIN_LICENSE" for
details. */
#ifndef _TTY_H
#define _TTY_H
/* tty tables */
#define INP_BUFFER_SIZE 256
#define OUT_BUFFER_SIZE 256
#define NTTYS 128
#define real_tty_attached(p) (CTTY_IS_VALID ((p)->ctty) && !iscons_dev ((p)->ctty))
/* Input/Output/ioctl events */
#define INPUT_AVAILABLE_EVENT "cygtty.input.avail"
#define OUTPUT_MUTEX "cygtty.output.mutex"
#define INPUT_MUTEX "cygtty.input.mutex"
#define PIPE_SW_MUTEX "cygtty.pipe_sw.mutex"
#define TTY_SLAVE_ALIVE "cygtty.slave_alive"
#define TTY_SLAVE_READING "cygtty.slave_reading"
#include <sys/termios.h>
#ifndef MIN_CTRL_C_SLOP
#define MIN_CTRL_C_SLOP 50
#endif
typedef void *HPCON;
#include "devices.h"
class tty_min
{
pid_t sid; /* Session ID of tty */
struct status_flags
{
unsigned initialized : 1; /* Set if tty is initialized */
} status;
public:
pid_t pgid;
bool output_stopped; /* FIXME: Maybe do this with a mutex someday? */
fh_devices ntty;
ULONGLONG last_ctrl_c; /* tick count of last ctrl-c */
bool is_console;
int last_sig;
IMPLEMENT_STATUS_FLAG (bool, initialized)
struct termios ti;
struct winsize winsize;
/* ioctl requests buffer */
int cmd;
union
{
struct termios termios;
struct winsize winsize;
int value;
pid_t pid;
} arg;
/* XXX_retval variables holds master's completion codes. Error are stored as
* -ERRNO
*/
int ioctl_retval;
void setntty (_major_t t, _minor_t n) {ntty = (fh_devices) FHDEV (t, n);}
dev_t getntty () const {return ntty;}
_minor_t get_minor () const {return device::minor (ntty);}
pid_t getpgid () const {return pgid;}
void setpgid (int pid);
int getsid () const {return sid;}
void setsid (pid_t tsid) {sid = tsid;}
void kill_pgrp (int, pid_t target_pgid = 0);
int is_orphaned_process_group (int);
const char *ttyname () __attribute (());
};
/* The name *nat* comes from 'native' which means non-cygwin
(native windows). They are used for non-cygwin process. */
class fhandler_pty_master;
class tty: public tty_min
{
HANDLE get_event (const char *fmt, PSECURITY_ATTRIBUTES sa,
BOOL manual_reset = FALSE);
public:
pid_t master_pid; /* PID of tty master process */
/* Transfer direction for fhandler_pty_slave::transfer_input() */
enum xfer_dir
{
to_cyg,
to_nat
};
enum cons_mode
{
restore, /* For restoring when exit from cygwin. */
cygwin, /* For cygwin apps */
native /* For native apps executed from cygwin. */
};
private:
HANDLE _from_master_nat;
HANDLE _from_master;
HANDLE _to_master_nat;
HANDLE _to_master;
HANDLE _to_slave_nat;
HANDLE _to_slave;
bool pcon_activated;
bool pcon_start;
pid_t pcon_start_pid;
bool switch_to_nat_pipe;
DWORD nat_pipe_owner_pid;
UINT term_code_page;
ULONGLONG fwd_last_time;
bool fwd_not_empty;
HANDLE h_pcon_write_pipe;
HANDLE h_pcon_condrv_reference;
HANDLE h_pcon_conhost_process;
HANDLE h_pcon_in;
HANDLE h_pcon_out;
bool pcon_cap_checked;
bool has_csi6n;
bool need_invisible_console;
pid_t invisible_console_pid;
UINT previous_code_page;
UINT previous_output_code_page;
bool master_is_running_as_service;
bool req_xfer_input;
xfer_dir pty_input_state;
bool mask_flusho;
bool discard_input;
bool stop_fwd_thread;
public:
HANDLE from_master_nat () const { return _from_master_nat; }
HANDLE from_master () const { return _from_master; }
HANDLE to_master_nat () const { return _to_master_nat; }
HANDLE to_master () const { return _to_master; }
HANDLE to_slave_nat () const { return _to_slave_nat; }
HANDLE to_slave () const { return _to_slave; }
void set_from_master_nat (HANDLE h) { _from_master_nat = h; }
void set_from_master (HANDLE h) { _from_master = h; }
void set_to_master_nat (HANDLE h) { _to_master_nat = h; }
void set_to_master (HANDLE h) { _to_master = h; }
void set_to_slave_nat (HANDLE h) { _to_slave_nat = h; }
void set_to_slave (HANDLE h) { _to_slave = h; }
int read_retval;
bool was_opened; /* True if opened at least once. */
int column; /* Current Column */
void init ();
HANDLE open_inuse (ACCESS_MASK access);
HANDLE create_inuse (PSECURITY_ATTRIBUTES);
bool slave_alive ();
HANDLE open_mutex (const char *mutex, ACCESS_MASK access);
inline HANDLE open_output_mutex (ACCESS_MASK access)
{ return open_mutex (OUTPUT_MUTEX, access); }
inline HANDLE open_input_mutex (ACCESS_MASK access)
{ return open_mutex (INPUT_MUTEX, access); }
bool exists ();
bool not_allocated (HANDLE&, HANDLE&);
void set_master_ctl_closed () {master_pid = -1;}
static void create_master (int);
static void init_session ();
void wait_fwd ();
bool pty_input_state_eq (xfer_dir x) { return pty_input_state == x; }
bool nat_fg (pid_t pgid);
friend class fhandler_pty_common;
friend class fhandler_pty_master;
friend class fhandler_pty_slave;
friend class tty_min;
};
class tty_list
{
tty ttys[NTTYS];
static HANDLE mutex;
public:
tty * operator [](int n) {return ttys + device::minor (n);}
int allocate (HANDLE& r, HANDLE& w); /* allocate a pty */
int connect (int);
void init ();
tty_min *get_cttyp ();
int attach (int n);
static void init_session ();
friend class lock_ttys;
};
class lock_ttys
{
bool release_me;
public:
lock_ttys (DWORD = INFINITE);
static void release ();
void dont_release () {release_me = false;}
~lock_ttys ()
{
if (release_me)
release ();
}
};
extern "C" int ttyslot (void);
/* Console stuff */
#define MAX_CONS_DEV 128
#define CONS_SCAN_UNUSED (-1)
#endif /*_TTY_H*/