/* * CDDL HEADER START * * The contents of this file are subject to the terms of the * Common Development and Distribution License (the "License"). * You may not use this file except in compliance with the License. * * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE * or http://www.opensolaris.org/os/licensing. * See the License for the specific language governing permissions * and limitations under the License. * * When distributing Covered Code, include this CDDL HEADER in each * file and include the License file at usr/src/OPENSOLARIS.LICENSE. * If applicable, add the following below this CDDL HEADER, with the * fields enclosed by brackets "[]" replaced with your own identifying * information: Portions Copyright [yyyy] [name of copyright owner] * * CDDL HEADER END */ /* * Copyright 2008 Sun Microsystems, Inc. All rights reserved. * Use is subject to license terms. * Copyright 2021 Oxide Computer Company */ /* * PSEUDO-TERMINAL COMMON DATA AND ROUTINES (PTM, PTS) * * This file contains global data and code shared between manager and * subsidiary parts of the pseudo-terminal driver. * * Pseudo-terminals (or ptys for short) are allocated dynamically. * ptys are put in the global ptms_slots array indexed by minor numbers. * * The slots array is initially small (of the size NPTY_MIN). When more ptys are * needed than the slot array size, the larger slot array is allocated and all * opened ptys move to the new one. * * * RESOURCE ALLOCATION * * - pt_ttys structures are allocated via pt_ttys_alloc, which uses * kmem_cache_alloc(). * - Minor number space is allocated via vmem_alloc() interface. * - ptms_slots arrays are allocated via kmem_alloc(). * * Minors start from 1 instead of 0, because vmem_alloc() returns 0 in case of * failure. Also, in anticipation of removing the clone device interface to * pseudo-terminal subsystem, minor 0 should not be used. (Potential future * development). * * After the table slot size reaches pt_maxdelta, we stop 2^N extension * algorithm and start extending the slot table size by pt_maxdelta. * * Device entries /dev/pts directory are created dynamically by the /dev * filesystem. We no longer call ddi_create_minor_node() on behalf of the * subsidiary driver. The /dev filesystem creates /dev/pts nodes based on the * pt_ttys array. * * * SYNCHRONIZATION * * All global data synchronization between ptm/pts is done via global ptms_lock * mutex which is implicitly initialized by declaring it global. * * Individual fields of pt_ttys structure (except ptm_rdq, pts_rdq and * pt_nullmsg) are protected by pt_ttys.pt_lock mutex. * * PT_ENTER_READ/PT_ENTER_WRITE are reference counter based read-write locks * which allow reader locks to be reacquired by the same thread (usual * reader/writer locks can't be used for that purpose since it is illegal for a * thread to acquire a lock it already holds, even as a reader). The sole * purpose of these macros is to guarantee that the peer queue will not * disappear (due to closing peer) while it is used. It is safe to use * PT_ENTER_READ/PT_EXIT_READ brackets across calls like putq/putnext (since * they are not real locks but reference counts). * * PT_ENTER_WRITE/PT_EXIT_WRITE brackets are used ONLY in manager/subsidiary * open/close paths to modify ptm_rdq and pts_rdq fields. These fields should * be set to appropriate queues *after* qprocson() is called during open (to * prevent peer from accessing the queue with incomplete plumbing) and set to * NULL before qprocsoff() is called during close. Put and service procedures * use PT_ENTER_READ/PT_EXIT_READ to prevent peer closes. * * The pt_nullmsg field is only used in open/close routines and is also * protected by PT_ENTER_WRITE/PT_EXIT_WRITE brackets to avoid extra mutex * holds. * * * LOCK ORDERING * * If both ptms_lock and per-pty lock should be held, ptms_lock should always * be entered first, followed by per-pty lock. * * * GLOBAL FUNCTIONS * * void ptms_init(void); * * Called by pts/ptm _init entry points. It performes one-time * initialization needed for both pts and ptm. This initialization is done * here and not in ptms_initspace because all these data structures are not * needed if pseudo-terminals are not used in the system. * * struct pt_ttys *pt_ttys_alloc(void); * * Allocate new minor number and pseudo-terminal entry. May sleep. * New minor number is recorded in pt_minor field of the entry returned. * This routine also initializes pt_minor and pt_state fields of the new * pseudo-terminal and puts a pointer to it into ptms_slots array. * * struct pt_ttys *ptms_minor2ptty(minor_t minor) * * Find pt_ttys structure by minor number. * Returns NULL when minor is out of range. * * int ptms_minor_valid(minor_t minor, uid_t *ruid, gid_t *rgid) * * Check if minor refers to an allocated pty in the current zone. * Returns * 0 if not allocated or not for this zone. * 1 if an allocated pty in the current zone. * Also returns owner of pty. * * int ptms_minor_exists(minor_t minor) * * Check if minor refers to an allocated pty (in any zone) * Returns * 0 if not an allocated pty * 1 if an allocated pty * * void ptms_set_owner(minor_t minor, uid_t ruid, gid_t rgid) * * Sets the owner associated with a pty. * * void ptms_close(struct pt_ttys *pt, uint_t flags_to_clear); * * Clear flags_to_clear in pt and if no one owns it (PTMOPEN/PTSOPEN not * set) free pt entry and corresponding slot. * * * TUNEABLES AND CONFIGURATION * * pt_cnt: minimum number of pseudo-terminals in the system. The system * should provide at least this number of ptys (provided sufficient * memory is available). It is different from the older semantics * of pt_cnt meaning maximum number of ptys. * Set to 0 by default. * * pt_max_pty: Maximum number of pseudo-terminals in the system. The system * should not allocate more ptys than pt_max_pty (although, it may * impose stricter maximum). Zero value means no user-defined * maximum. This is intended to be used as "denial-of-service" * protection. * Set to 0 by default. * * Both pt_cnt and pt_max_pty may be modified during system * lifetime with their semantics preserved. * * pt_init_cnt: Initial size of ptms_slots array. Set to NPTY_INITIAL. * * pt_ptyofmem: Approximate percentage of system memory that may be * occupied by pty data structures. Initially set to NPTY_PERCENT. * This variable is used once during initialization to estimate * maximum number of ptys in the system. The actual maximum is * determined as minimum of pt_max_pty and calculated value. * * pt_maxdelta: Maximum extension chunk of the slot table. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #ifdef DEBUG #include #endif /* Initial number of ptms slots */ #define NPTY_INITIAL 16 #define NPTY_PERCENT 5 /* Maximum increment of the slot table size */ #define PTY_MAXDELTA 128 /* * Tuneable variables. */ uint_t pt_cnt = 0; /* Minimum number of ptys */ size_t pt_max_pty = 0; /* Maximum number of ptys */ uint_t pt_init_cnt = NPTY_INITIAL; /* Initial number of ptms slots */ uint_t pt_pctofmem = NPTY_PERCENT; /* Percent of memory to use for ptys */ uint_t pt_maxdelta = PTY_MAXDELTA; /* Max increment for slot table size */ /* Other global variables */ kmutex_t ptms_lock; /* Global data access lock */ /* * Slot array and its management variables */ static struct pt_ttys **ptms_slots = NULL; /* Slots for actual pt structures */ static size_t ptms_nslots = 0; /* Size of slot array */ static size_t ptms_ptymax = 0; /* Maximum number of ptys */ static size_t ptms_inuse = 0; /* # of ptys currently allocated */ dev_info_t *pts_dip = NULL; /* Set if subsidiary is attached */ static struct kmem_cache *ptms_cache = NULL; /* pty cache */ static vmem_t *ptms_minor_arena = NULL; /* Arena for device minors */ static uint_t ptms_roundup(uint_t); static int ptms_constructor(void *, void *, int); static void ptms_destructor(void *, void *); static minor_t ptms_grow(void); /* * Total size occupied by one pty. Each pty manager/subsidiary pair consumes * one pointer for ptms_slots array, one pt_ttys structure, and one empty * message preallocated for pts close. */ #define PTY_SIZE (sizeof (struct pt_ttys) + \ sizeof (struct pt_ttys *) + \ sizeof (dblk_t)) #ifdef DEBUG int ptms_debug = 0; #define PTMOD_ID 5 #endif /* * Clear all bits of x except the highest bit */ #define truncate(x) ((x) <= 2 ? (x) : (1 << (highbit(x) - 1))) /* * Roundup the number to the nearest power of 2 */ static uint_t ptms_roundup(uint_t x) { uint_t p = truncate(x); /* x with non-high bits stripped */ /* * If x is a power of 2, return x, otherwise roundup. */ return (p == x ? p : (p * 2)); } /* * Allocate ptms_slots array and kmem cache for pt_ttys. This initialization is * only called once during system lifetime. Called from ptm or pts _init * routine. */ void ptms_init(void) { mutex_enter(&ptms_lock); if (ptms_slots == NULL) { ptms_slots = kmem_zalloc(pt_init_cnt * sizeof (struct pt_ttys *), KM_SLEEP); ptms_cache = kmem_cache_create("pty_map", sizeof (struct pt_ttys), 0, ptms_constructor, ptms_destructor, NULL, NULL, NULL, 0); ptms_nslots = pt_init_cnt; /* Allocate integer space for minor numbers */ ptms_minor_arena = vmem_create("ptms_minor", (void *)1, ptms_nslots, 1, NULL, NULL, NULL, 0, VM_SLEEP | VMC_IDENTIFIER); /* * Calculate available number of ptys - how many ptys can we * allocate in pt_pctofmem % of available memory. The value is * rounded up to the nearest power of 2. */ ptms_ptymax = ptms_roundup((pt_pctofmem * kmem_maxavail()) / (100 * PTY_SIZE)); } mutex_exit(&ptms_lock); } /* * This routine attaches the pts dip. */ int ptms_attach_subsidiary(void) { if (pts_dip == NULL && i_ddi_attach_pseudo_node("pts") == NULL) return (-1); ASSERT(pts_dip); return (0); } /* * Called from /dev fs. Checks if dip is attached, * and if it is, returns its major number. */ major_t ptms_subsidiary_attached(void) { major_t maj = DDI_MAJOR_T_NONE; mutex_enter(&ptms_lock); if (pts_dip) maj = ddi_driver_major(pts_dip); mutex_exit(&ptms_lock); return (maj); } /* * Allocate new minor number and pseudo-terminal entry. Returns the new entry or * NULL if no memory or maximum number of entries reached. */ struct pt_ttys * pt_ttys_alloc(void) { minor_t dminor; struct pt_ttys *pt = NULL; mutex_enter(&ptms_lock); /* * Always try to allocate new pty when pt_cnt minimum limit is not * achieved. If it is achieved, the maximum is determined by either * user-specified value (if it is non-zero) or our memory estimations - * whatever is less. */ if (ptms_inuse >= pt_cnt) { /* * When system achieved required minimum of ptys, check for the * denial of service limits. * * Since pt_max_pty may be zero, the formula below is used to * avoid conditional expression. It will equal to pt_max_pty if * it is not zero and ptms_ptymax otherwise. */ size_t user_max = (pt_max_pty == 0 ? ptms_ptymax : pt_max_pty); /* Do not try to allocate more than allowed */ if (ptms_inuse >= min(ptms_ptymax, user_max)) { mutex_exit(&ptms_lock); return (NULL); } } ptms_inuse++; /* * Allocate new minor number. If this fails, all slots are busy and * we need to grow the hash. */ dminor = (minor_t)(uintptr_t) vmem_alloc(ptms_minor_arena, 1, VM_NOSLEEP); if (dminor == 0) { /* Grow the cache and retry allocation */ dminor = ptms_grow(); } if (dminor == 0) { /* Not enough memory now */ ptms_inuse--; mutex_exit(&ptms_lock); return (NULL); } pt = kmem_cache_alloc(ptms_cache, KM_NOSLEEP); if (pt == NULL) { /* Not enough memory - this entry can't be used now. */ vmem_free(ptms_minor_arena, (void *)(uintptr_t)dminor, 1); ptms_inuse--; } else { pt->pt_minor = dminor; pt->pt_pid = curproc->p_pid; /* For debugging */ pt->pt_state = (PTMOPEN | PTLOCK); pt->pt_zoneid = getzoneid(); pt->pt_ruid = 0; /* we don't know uid/gid yet. Report as root */ pt->pt_rgid = 0; ASSERT(ptms_slots[dminor - 1] == NULL); ptms_slots[dminor - 1] = pt; } mutex_exit(&ptms_lock); return (pt); } /* * Get pt_ttys structure by minor number. * Returns NULL when minor is out of range. */ struct pt_ttys * ptms_minor2ptty(minor_t dminor) { struct pt_ttys *pt = NULL; ASSERT(mutex_owned(&ptms_lock)); if ((dminor >= 1) && (dminor <= ptms_nslots) && ptms_slots != NULL) pt = ptms_slots[dminor - 1]; return (pt); } /* * Invoked in response to chown on /dev/pts nodes to change the * permission on a pty */ void ptms_set_owner(minor_t dminor, uid_t ruid, gid_t rgid) { struct pt_ttys *pt; if (ruid > MAXUID || rgid > MAXUID) return; /* * /dev/pts/0 is not used, but some applications may check it. There * is no pty backing it - so we have nothing to do. */ if (dminor == 0) return; mutex_enter(&ptms_lock); pt = ptms_minor2ptty(dminor); if (pt != NULL && pt->pt_zoneid == getzoneid()) { pt->pt_ruid = ruid; pt->pt_rgid = rgid; } mutex_exit(&ptms_lock); } /* * Given a ptm/pts minor number * returns: * 1 if the pty is allocated to the current zone. * 0 otherwise * * If the pty is allocated to the current zone, it also returns the owner. */ int ptms_minor_valid(minor_t dminor, uid_t *ruid, gid_t *rgid) { struct pt_ttys *pt; int ret; ASSERT(ruid); ASSERT(rgid); *ruid = (uid_t)-1; *rgid = (gid_t)-1; /* * /dev/pts/0 is not used, but some applications may check it, so create * it also. Report the owner as root. It belongs to all zones. */ if (dminor == 0) { *ruid = 0; *rgid = 0; return (1); } ret = 0; mutex_enter(&ptms_lock); pt = ptms_minor2ptty(dminor); if (pt != NULL) { ASSERT(pt->pt_ruid <= MAXUID); ASSERT(pt->pt_rgid <= MAXUID); if (pt->pt_zoneid == getzoneid()) { ret = 1; *ruid = pt->pt_ruid; *rgid = pt->pt_rgid; } } mutex_exit(&ptms_lock); return (ret); } /* * Given a ptm/pts minor number * returns: * 0 if the pty is not allocated * 1 if the pty is allocated */ int ptms_minor_exists(minor_t dminor) { int ret; mutex_enter(&ptms_lock); ret = ptms_minor2ptty(dminor) ? 1 : 0; mutex_exit(&ptms_lock); return (ret); } /* * Close the pt and clear flags_to_clear. * If pt device is not opened by someone else, free it and clear its slot. */ void ptms_close(struct pt_ttys *pt, uint_t flags_to_clear) { uint_t flags; ASSERT(MUTEX_NOT_HELD(&ptms_lock)); ASSERT(pt != NULL); mutex_enter(&ptms_lock); mutex_enter(&pt->pt_lock); pt->pt_state &= ~flags_to_clear; flags = pt->pt_state; mutex_exit(&pt->pt_lock); if (! (flags & (PTMOPEN | PTSOPEN))) { /* No one owns the entry - free it */ ASSERT(pt->ptm_rdq == NULL); ASSERT(pt->pts_rdq == NULL); ASSERT(pt->pt_nullmsg == NULL); ASSERT(pt->pt_refcnt == 0); ASSERT(pt->pt_minor <= ptms_nslots); ASSERT(ptms_slots[pt->pt_minor - 1] == pt); ASSERT(ptms_inuse > 0); ptms_inuse--; pt->pt_pid = 0; ptms_slots[pt->pt_minor - 1] = NULL; /* Return minor number to the pool of minors */ vmem_free(ptms_minor_arena, (void *)(uintptr_t)pt->pt_minor, 1); /* Return pt to the cache */ kmem_cache_free(ptms_cache, pt); } mutex_exit(&ptms_lock); } /* * Allocate another slot table twice as large as the original one (limited to * global maximum). Migrate all pt to the new slot table and free the original * one. Create more /devices entries for new devices. */ static minor_t ptms_grow() { minor_t old_size = ptms_nslots; minor_t delta = MIN(pt_maxdelta, old_size); minor_t new_size = old_size + delta; struct pt_ttys **ptms_old = ptms_slots; struct pt_ttys **ptms_new; void *vaddr; /* vmem_add return value */ ASSERT(MUTEX_HELD(&ptms_lock)); DDBG("ptmopen(%d): need to grow\n", (int)ptms_inuse); /* Allocate new ptms array */ ptms_new = kmem_zalloc(new_size * sizeof (struct pt_ttys *), KM_NOSLEEP); if (ptms_new == NULL) return ((minor_t)0); /* Increase clone index space */ vaddr = vmem_add(ptms_minor_arena, (void *)(uintptr_t)(old_size + 1), new_size - old_size, VM_NOSLEEP); if (vaddr == NULL) { kmem_free(ptms_new, new_size * sizeof (struct pt_ttys *)); return ((minor_t)0); } /* Migrate pt entries to a new location */ ptms_nslots = new_size; bcopy(ptms_old, ptms_new, old_size * sizeof (struct pt_ttys *)); ptms_slots = ptms_new; kmem_free(ptms_old, old_size * sizeof (struct pt_ttys *)); /* Allocate minor number and return it */ return ((minor_t)(uintptr_t) vmem_alloc(ptms_minor_arena, 1, VM_NOSLEEP)); } /*ARGSUSED*/ static int ptms_constructor(void *maddr, void *arg, int kmflags) { struct pt_ttys *pt = maddr; pt->pts_rdq = NULL; pt->ptm_rdq = NULL; pt->pt_nullmsg = NULL; pt->pt_pid = 0; pt->pt_minor = 0; pt->pt_refcnt = 0; pt->pt_state = 0; pt->pt_zoneid = GLOBAL_ZONEID; cv_init(&pt->pt_cv, NULL, CV_DEFAULT, NULL); mutex_init(&pt->pt_lock, NULL, MUTEX_DEFAULT, NULL); return (0); } /*ARGSUSED*/ static void ptms_destructor(void *maddr, void *arg) { struct pt_ttys *pt = maddr; ASSERT(pt->pt_refcnt == 0); ASSERT(pt->pt_state == 0); ASSERT(pt->ptm_rdq == NULL); ASSERT(pt->pts_rdq == NULL); mutex_destroy(&pt->pt_lock); cv_destroy(&pt->pt_cv); } #ifdef DEBUG void ptms_log(char *str, uint_t arg) { if (ptms_debug) { if (ptms_debug & 2) cmn_err(CE_CONT, str, arg); if (ptms_debug & 4) (void) strlog(PTMOD_ID, -1, 0, SL_TRACE | SL_ERROR, str, arg); else (void) strlog(PTMOD_ID, -1, 0, SL_TRACE, str, arg); } } void ptms_logp(char *str, uintptr_t arg) { if (ptms_debug) { if (ptms_debug & 2) cmn_err(CE_CONT, str, arg); if (ptms_debug & 4) (void) strlog(PTMOD_ID, -1, 0, SL_TRACE | SL_ERROR, str, arg); else (void) strlog(PTMOD_ID, -1, 0, SL_TRACE, str, arg); } } #endif