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Diffstat (limited to 'libexec/rtld-elf/rtld_lock.c')
| -rw-r--r-- | libexec/rtld-elf/rtld_lock.c | 505 |
1 files changed, 505 insertions, 0 deletions
diff --git a/libexec/rtld-elf/rtld_lock.c b/libexec/rtld-elf/rtld_lock.c new file mode 100644 index 000000000000..d99b64d8c66a --- /dev/null +++ b/libexec/rtld-elf/rtld_lock.c @@ -0,0 +1,505 @@ +/*- + * SPDX-License-Identifier: BSD-2-Clause + * + * Copyright 1999, 2000 John D. Polstra. + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR + * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES + * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. + * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT + * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF + * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + * + * from: FreeBSD: src/libexec/rtld-elf/sparc64/lockdflt.c,v 1.3 2002/10/09 + */ + +/* + * Thread locking implementation for the dynamic linker. + * + * We use the "simple, non-scalable reader-preference lock" from: + * + * J. M. Mellor-Crummey and M. L. Scott. "Scalable Reader-Writer + * Synchronization for Shared-Memory Multiprocessors." 3rd ACM Symp. on + * Principles and Practice of Parallel Programming, April 1991. + * + * In this algorithm the lock is a single word. Its low-order bit is + * set when a writer holds the lock. The remaining high-order bits + * contain a count of readers desiring the lock. The algorithm requires + * atomic "compare_and_store" and "add" operations, which we take + * from machine/atomic.h. + */ + +#include <sys/param.h> +#include <sys/signalvar.h> +#include <signal.h> +#include <stdlib.h> +#include <time.h> + +#include "debug.h" +#include "rtld.h" +#include "rtld_machdep.h" +#include "rtld_libc.h" + +void _rtld_thread_init(struct RtldLockInfo *) __exported; +void _rtld_atfork_pre(int *) __exported; +void _rtld_atfork_post(int *) __exported; + +static char def_dlerror_msg[512]; +static int def_dlerror_seen_val = 1; + +static char * +def_dlerror_loc(void) +{ + return (def_dlerror_msg); +} + +static int * +def_dlerror_seen(void) +{ + return (&def_dlerror_seen_val); +} + +#define WAFLAG 0x1 /* A writer holds the lock */ +#define RC_INCR 0x2 /* Adjusts count of readers desiring lock */ + +typedef struct Struct_Lock { + volatile u_int lock; + void *base; +} Lock; + +static sigset_t fullsigmask, oldsigmask; +static int thread_flag, wnested; +static uint32_t fsigblock; + +static void * +def_lock_create(void) +{ + void *base; + char *p; + uintptr_t r; + Lock *l; + + /* + * Arrange for the lock to occupy its own cache line. First, we + * optimistically allocate just a cache line, hoping that malloc + * will give us a well-aligned block of memory. If that doesn't + * work, we allocate a larger block and take a well-aligned cache + * line from it. + */ + base = xmalloc(CACHE_LINE_SIZE); + p = base; + if ((uintptr_t)p % CACHE_LINE_SIZE != 0) { + free(base); + base = xmalloc(2 * CACHE_LINE_SIZE); + p = base; + if ((r = (uintptr_t)p % CACHE_LINE_SIZE) != 0) + p += CACHE_LINE_SIZE - r; + } + l = (Lock *)p; + l->base = base; + l->lock = 0; + return (l); +} + +static void +def_lock_destroy(void *lock) +{ + Lock *l = lock; + + free(l->base); +} + +static void +sig_fastunblock(void) +{ + uint32_t oldval; + + assert((fsigblock & ~SIGFASTBLOCK_FLAGS) >= SIGFASTBLOCK_INC); + oldval = atomic_fetchadd_32(&fsigblock, -SIGFASTBLOCK_INC); + if (oldval == (SIGFASTBLOCK_PEND | SIGFASTBLOCK_INC)) + __sys_sigfastblock(SIGFASTBLOCK_UNBLOCK, NULL); +} + +static bool +def_lock_acquire_set(Lock *l, bool wlock) +{ + if (wlock) { + if (atomic_cmpset_acq_int(&l->lock, 0, WAFLAG)) + return (true); + } else { + atomic_add_acq_int(&l->lock, RC_INCR); + if ((l->lock & WAFLAG) == 0) + return (true); + atomic_add_int(&l->lock, -RC_INCR); + } + return (false); +} + +static void +def_lock_acquire(Lock *l, bool wlock) +{ + sigset_t tmp_oldsigmask; + + if (ld_fast_sigblock) { + for (;;) { + atomic_add_32(&fsigblock, SIGFASTBLOCK_INC); + if (def_lock_acquire_set(l, wlock)) + break; + sig_fastunblock(); + } + } else { + for (;;) { + sigprocmask(SIG_BLOCK, &fullsigmask, &tmp_oldsigmask); + if (def_lock_acquire_set(l, wlock)) + break; + sigprocmask(SIG_SETMASK, &tmp_oldsigmask, NULL); + } + if (atomic_fetchadd_int(&wnested, 1) == 0) + oldsigmask = tmp_oldsigmask; + } +} + +static void +def_rlock_acquire(void *lock) +{ + def_lock_acquire(lock, false); +} + +static void +def_wlock_acquire(void *lock) +{ + def_lock_acquire(lock, true); +} + +static void +def_lock_release(void *lock) +{ + Lock *l = lock; + + atomic_add_rel_int(&l->lock, -((l->lock & WAFLAG) == 0 ? + RC_INCR : WAFLAG)); + if (ld_fast_sigblock) + sig_fastunblock(); + else if (atomic_fetchadd_int(&wnested, -1) == 1) + sigprocmask(SIG_SETMASK, &oldsigmask, NULL); +} + +static int +def_thread_set_flag(int mask) +{ + int old_val = thread_flag; + + thread_flag |= mask; + return (old_val); +} + +static int +def_thread_clr_flag(int mask) +{ + int old_val = thread_flag; + + thread_flag &= ~mask; + return (old_val); +} + +/* + * Public interface exposed to the rest of the dynamic linker. + */ +struct RtldLockInfo lockinfo; +static struct RtldLockInfo deflockinfo; + +static __inline int +thread_mask_set(int mask) +{ + return (lockinfo.thread_set_flag(mask)); +} + +static __inline void +thread_mask_clear(int mask) +{ + lockinfo.thread_clr_flag(mask); +} + +#define RTLD_LOCK_CNT 3 +static struct rtld_lock { + void *handle; + int mask; +} rtld_locks[RTLD_LOCK_CNT]; + +rtld_lock_t rtld_bind_lock = &rtld_locks[0]; +rtld_lock_t rtld_libc_lock = &rtld_locks[1]; +rtld_lock_t rtld_phdr_lock = &rtld_locks[2]; + +void +rlock_acquire(rtld_lock_t lock, RtldLockState *lockstate) +{ + + if (lockstate == NULL) + return; + + if ((thread_mask_set(lock->mask) & lock->mask) != 0) { + dbg("rlock_acquire: recursed"); + lockstate->lockstate = RTLD_LOCK_UNLOCKED; + return; + } + lockinfo.rlock_acquire(lock->handle); + lockstate->lockstate = RTLD_LOCK_RLOCKED; +} + +void +wlock_acquire(rtld_lock_t lock, RtldLockState *lockstate) +{ + + if (lockstate == NULL) + return; + + if ((thread_mask_set(lock->mask) & lock->mask) != 0) { + dbg("wlock_acquire: recursed"); + lockstate->lockstate = RTLD_LOCK_UNLOCKED; + return; + } + lockinfo.wlock_acquire(lock->handle); + lockstate->lockstate = RTLD_LOCK_WLOCKED; +} + +void +lock_release(rtld_lock_t lock, RtldLockState *lockstate) +{ + + if (lockstate == NULL) + return; + + switch (lockstate->lockstate) { + case RTLD_LOCK_UNLOCKED: + break; + case RTLD_LOCK_RLOCKED: + case RTLD_LOCK_WLOCKED: + thread_mask_clear(lock->mask); + lockinfo.lock_release(lock->handle); + break; + default: + assert(0); + } +} + +void +lock_upgrade(rtld_lock_t lock, RtldLockState *lockstate) +{ + + if (lockstate == NULL) + return; + + lock_release(lock, lockstate); + wlock_acquire(lock, lockstate); +} + +void +lock_restart_for_upgrade(RtldLockState *lockstate) +{ + + if (lockstate == NULL) + return; + + switch (lockstate->lockstate) { + case RTLD_LOCK_UNLOCKED: + case RTLD_LOCK_WLOCKED: + break; + case RTLD_LOCK_RLOCKED: + siglongjmp(lockstate->env, 1); + break; + default: + assert(0); + } +} + +bool +lockstate_wlocked(const RtldLockState *lockstate) +{ + return (lockstate->lockstate == RTLD_LOCK_WLOCKED); +} + +void +dlerror_dflt_init(void) +{ + lockinfo.dlerror_loc = def_dlerror_loc; + lockinfo.dlerror_loc_sz = sizeof(def_dlerror_msg); + lockinfo.dlerror_seen = def_dlerror_seen; +} + +void +lockdflt_init(void) +{ + int i; + + deflockinfo.rtli_version = RTLI_VERSION; + deflockinfo.lock_create = def_lock_create; + deflockinfo.lock_destroy = def_lock_destroy; + deflockinfo.rlock_acquire = def_rlock_acquire; + deflockinfo.wlock_acquire = def_wlock_acquire; + deflockinfo.lock_release = def_lock_release; + deflockinfo.thread_set_flag = def_thread_set_flag; + deflockinfo.thread_clr_flag = def_thread_clr_flag; + deflockinfo.at_fork = NULL; + deflockinfo.dlerror_loc = def_dlerror_loc; + deflockinfo.dlerror_loc_sz = sizeof(def_dlerror_msg); + deflockinfo.dlerror_seen = def_dlerror_seen; + + for (i = 0; i < RTLD_LOCK_CNT; i++) { + rtld_locks[i].mask = (1 << i); + rtld_locks[i].handle = NULL; + } + + memcpy(&lockinfo, &deflockinfo, sizeof(lockinfo)); + _rtld_thread_init(NULL); + if (ld_fast_sigblock) { + __sys_sigfastblock(SIGFASTBLOCK_SETPTR, &fsigblock); + } else { + /* + * Construct a mask to block all signals. Note that + * blocked traps mean that the process is terminated + * if trap occurs while we are in locked section, with + * the default settings for kern.forcesigexit. + */ + sigfillset(&fullsigmask); + } +} + +/* + * Callback function to allow threads implementation to + * register their own locking primitives if the default + * one is not suitable. + * The current context should be the only context + * executing at the invocation time. + */ +void +_rtld_thread_init(struct RtldLockInfo *pli) +{ + const Obj_Entry *obj; + SymLook req; + void *locks[RTLD_LOCK_CNT]; + int flags, i, res; + + if (pli == NULL) { + lockinfo.rtli_version = RTLI_VERSION; + } else { + lockinfo.rtli_version = RTLI_VERSION_ONE; + obj = obj_from_addr(pli->lock_create); + if (obj != NULL) { + symlook_init(&req, "_pli_rtli_version"); + res = symlook_obj(&req, obj); + if (res == 0) + lockinfo.rtli_version = pli->rtli_version; + } + } + + /* disable all locking while this function is running */ + flags = thread_mask_set(~0); + + if (pli == NULL) + pli = &deflockinfo; + else if (ld_fast_sigblock) { + fsigblock = 0; + __sys_sigfastblock(SIGFASTBLOCK_UNSETPTR, NULL); + } + + for (i = 0; i < RTLD_LOCK_CNT; i++) + if ((locks[i] = pli->lock_create()) == NULL) + break; + + if (i < RTLD_LOCK_CNT) { + while (--i >= 0) + pli->lock_destroy(locks[i]); + abort(); + } + + for (i = 0; i < RTLD_LOCK_CNT; i++) { + if (rtld_locks[i].handle == NULL) + continue; + if (flags & rtld_locks[i].mask) + lockinfo.lock_release(rtld_locks[i].handle); + lockinfo.lock_destroy(rtld_locks[i].handle); + } + + for (i = 0; i < RTLD_LOCK_CNT; i++) { + rtld_locks[i].handle = locks[i]; + if (flags & rtld_locks[i].mask) + pli->wlock_acquire(rtld_locks[i].handle); + } + + lockinfo.lock_create = pli->lock_create; + lockinfo.lock_destroy = pli->lock_destroy; + lockinfo.rlock_acquire = pli->rlock_acquire; + lockinfo.wlock_acquire = pli->wlock_acquire; + lockinfo.lock_release = pli->lock_release; + lockinfo.thread_set_flag = pli->thread_set_flag; + lockinfo.thread_clr_flag = pli->thread_clr_flag; + lockinfo.at_fork = pli->at_fork; + if (lockinfo.rtli_version > RTLI_VERSION_ONE && pli != NULL) { + strlcpy(pli->dlerror_loc(), lockinfo.dlerror_loc(), + lockinfo.dlerror_loc_sz); + lockinfo.dlerror_loc = pli->dlerror_loc; + lockinfo.dlerror_loc_sz = pli->dlerror_loc_sz; + lockinfo.dlerror_seen = pli->dlerror_seen; + } + + /* restore thread locking state, this time with new locks */ + thread_mask_clear(~0); + thread_mask_set(flags); + dbg("_rtld_thread_init: done"); +} + +void +_rtld_atfork_pre(int *locks) +{ + RtldLockState ls[2]; + + if (locks == NULL) + return; + bzero(ls, sizeof(ls)); + + /* + * Warning: this did not worked well with the rtld compat + * locks above, when the thread signal mask was corrupted (set + * to all signals blocked) if two locks were taken + * simultaneously in the write mode. The caller of the + * _rtld_atfork_pre() must provide the working implementation + * of the locks anyway, and libthr locks are fine. + */ + if (ld_get_env_var(LD_NO_DL_ITERATE_PHDR_AFTER_FORK) == NULL) + wlock_acquire(rtld_phdr_lock, &ls[0]); + wlock_acquire(rtld_bind_lock, &ls[1]); + + /* XXXKIB: I am really sorry for this. */ + locks[0] = ls[1].lockstate; + locks[2] = ls[0].lockstate; +} + +void +_rtld_atfork_post(int *locks) +{ + RtldLockState ls[2]; + + if (locks == NULL) + return; + + bzero(ls, sizeof(ls)); + ls[0].lockstate = locks[2]; + ls[1].lockstate = locks[0]; + lock_release(rtld_bind_lock, &ls[1]); + if (ld_get_env_var(LD_NO_DL_ITERATE_PHDR_AFTER_FORK) == NULL) + lock_release(rtld_phdr_lock, &ls[0]); +} |