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Message-Id: <1371163284-6346-8-git-send-email-sasha.levin@oracle.com>
Date: Thu, 13 Jun 2013 18:41:22 -0400
From: Sasha Levin <sasha.levin@...cle.com>
To: torvalds@...ux-foundation.org
Cc: mingo@...nel.org, peterz@...radead.org,
linux-kernel@...r.kernel.org, Sasha Levin <sasha.levin@...cle.com>
Subject: [Patch v5 7/9] liblockdep: Support using LD_PRELOAD
This allows lockdep to be used without being compiled in the
original program.
Usage is quite simple:
LD_PRELOAD=/path/to/liblockdep.so /path/to/my/program
And magically, you'll have lockdep checking in your program!
Signed-off-by: Sasha Levin <sasha.levin@...cle.com>
---
tools/lib/lockdep/preload.c | 447 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 447 insertions(+)
create mode 100644 tools/lib/lockdep/preload.c
diff --git a/tools/lib/lockdep/preload.c b/tools/lib/lockdep/preload.c
new file mode 100644
index 0000000..83f5b22
--- /dev/null
+++ b/tools/lib/lockdep/preload.c
@@ -0,0 +1,447 @@
+#define _GNU_SOURCE
+#include <pthread.h>
+#include <stdio.h>
+#include <dlfcn.h>
+#include <stdlib.h>
+#include <sysexits.h>
+#include "include/liblockdep/mutex.h"
+#include "../../../include/linux/rbtree.h"
+
+/**
+ * struct lock_lookup - liblockdep's view of a single unique lock
+ * @orig: pointer to the original pthread lock, used for lookups
+ * @dep_map: lockdep's dep_map structure
+ * @key: lockdep's key structure
+ * @node: rb-tree node used to store the lock in a global tree
+ * @name: a unique name for the lock
+ */
+struct lock_lookup {
+ void *orig; /* Original pthread lock, used for lookups */
+ struct lockdep_map dep_map; /* Since all locks are dynamic, we need
+ * a dep_map and a key for each lock */
+ /*
+ * Wait, there's no support for key classes? Yup :(
+ * Most big projects wrap the pthread api with their own calls to
+ * be compatible with different locking methods. This means that
+ * "classes" will be brokes since the function that creates all
+ * locks will point to a generic locking function instead of the
+ * actual code that wants to do the locking.
+ */
+ struct lock_class_key key;
+ struct rb_node node;
+#define LIBLOCKDEP_MAX_LOCK_NAME 22
+ char name[LIBLOCKDEP_MAX_LOCK_NAME];
+};
+
+/* This is where we store our locks */
+static struct rb_root locks = RB_ROOT;
+static pthread_rwlock_t locks_rwlock = PTHREAD_RWLOCK_INITIALIZER;
+
+/* pthread mutex API */
+
+#ifdef __GLIBC__
+extern int __pthread_mutex_init(pthread_mutex_t *mutex, const pthread_mutexattr_t *attr);
+extern int __pthread_mutex_lock(pthread_mutex_t *mutex);
+extern int __pthread_mutex_trylock(pthread_mutex_t *mutex);
+extern int __pthread_mutex_unlock(pthread_mutex_t *mutex);
+extern int __pthread_mutex_destroy(pthread_mutex_t *mutex);
+#else
+#define __pthread_mutex_init NULL
+#define __pthread_mutex_lock NULL
+#define __pthread_mutex_trylock NULL
+#define __pthread_mutex_unlock NULL
+#define __pthread_mutex_destroy NULL
+#endif
+static int (*ll_pthread_mutex_init)(pthread_mutex_t *mutex,
+ const pthread_mutexattr_t *attr) = __pthread_mutex_init;
+static int (*ll_pthread_mutex_lock)(pthread_mutex_t *mutex) = __pthread_mutex_lock;
+static int (*ll_pthread_mutex_trylock)(pthread_mutex_t *mutex) = __pthread_mutex_trylock;
+static int (*ll_pthread_mutex_unlock)(pthread_mutex_t *mutex) = __pthread_mutex_unlock;
+static int (*ll_pthread_mutex_destroy)(pthread_mutex_t *mutex) = __pthread_mutex_destroy;
+
+/* pthread rwlock API */
+
+#ifdef __GLIBC__
+extern int __pthread_rwlock_init(pthread_rwlock_t *rwlock, const pthread_rwlockattr_t *attr);
+extern int __pthread_rwlock_destroy(pthread_rwlock_t *rwlock);
+extern int __pthread_rwlock_wrlock(pthread_rwlock_t *rwlock);
+extern int __pthread_rwlock_trywrlock(pthread_rwlock_t *rwlock);
+extern int __pthread_rwlock_rdlock(pthread_rwlock_t *rwlock);
+extern int __pthread_rwlock_tryrdlock(pthread_rwlock_t *rwlock);
+extern int __pthread_rwlock_unlock(pthread_rwlock_t *rwlock);
+#else
+#define __pthread_rwlock_init NULL
+#define __pthread_rwlock_destroy NULL
+#define __pthread_rwlock_wrlock NULL
+#define __pthread_rwlock_trywrlock NULL
+#define __pthread_rwlock_rdlock NULL
+#define __pthread_rwlock_tryrdlock NULL
+#define __pthread_rwlock_unlock NULL
+#endif
+
+static int (*ll_pthread_rwlock_init)(pthread_rwlock_t *rwlock,
+ const pthread_rwlockattr_t *attr) = __pthread_rwlock_init;
+static int (*ll_pthread_rwlock_destroy)(pthread_rwlock_t *rwlock) = __pthread_rwlock_destroy;
+static int (*ll_pthread_rwlock_rdlock)(pthread_rwlock_t *rwlock) = __pthread_rwlock_rdlock;
+static int (*ll_pthread_rwlock_tryrdlock)(pthread_rwlock_t *rwlock) = __pthread_rwlock_tryrdlock;
+static int (*ll_pthread_rwlock_trywrlock)(pthread_rwlock_t *rwlock) = __pthread_rwlock_trywrlock;
+static int (*ll_pthread_rwlock_wrlock)(pthread_rwlock_t *rwlock) = __pthread_rwlock_wrlock;
+static int (*ll_pthread_rwlock_unlock)(pthread_rwlock_t *rwlock) = __pthread_rwlock_unlock;
+
+enum { none, prepare, done, } __init_state;
+static void init_preload(void);
+static void try_init_preload(void)
+{
+ if (!__init_state != done)
+ init_preload();
+}
+
+static struct rb_node **__get_lock_node(void *lock, struct rb_node **parent)
+{
+ struct rb_node **node = &locks.rb_node;
+ struct lock_lookup *l;
+
+ *parent = NULL;
+
+ while (*node) {
+ l = rb_entry(*node, struct lock_lookup, node);
+
+ *parent = *node;
+ if (lock < l->orig)
+ node = &l->node.rb_left;
+ else if (lock > l->orig)
+ node = &l->node.rb_right;
+ else
+ return node;
+ }
+
+ return node;
+}
+
+#ifndef LIBLOCKDEP_STATIC_ENTRIES
+#define LIBLOCKDEP_STATIC_ENTRIES 1024
+#endif
+
+#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
+
+static struct lock_lookup __locks[LIBLOCKDEP_STATIC_ENTRIES];
+static int __locks_nr;
+
+static inline bool is_static_lock(struct lock_lookup *lock)
+{
+ return lock >= __locks && lock < __locks + ARRAY_SIZE(__locks);
+}
+
+static struct lock_lookup *alloc_lock(void)
+{
+ if (__init_state != done) {
+ /*
+ * Some programs attempt to initialize and use locks in their
+ * allocation path. This means that a call to malloc() would
+ * result in locks being initialized and locked.
+ *
+ * Why is it an issue for us? dlsym() below will try allocating
+ * to give us the original function. Since this allocation will
+ * result in a locking operations, we have to let pthread deal
+ * with it, but we can't! we don't have the pointer to the
+ * original API since we're inside dlsym() trying to get it
+ */
+
+ int idx = __locks_nr++;
+ if (idx >= ARRAY_SIZE(__locks)) {
+ fprintf(stderr,
+ "LOCKDEP error: insufficient LIBLOCKDEP_STATIC_ENTRIES\n");
+ exit(EX_UNAVAILABLE);
+ }
+ return __locks + idx;
+ }
+
+ return malloc(sizeof(struct lock_lookup));
+}
+
+static inline void free_lock(struct lock_lookup *lock)
+{
+ if (likely(!is_static_lock(lock)))
+ free(lock);
+}
+
+/**
+ * __get_lock - find or create a lock instance
+ * @lock: pointer to a pthread lock function
+ *
+ * Try to find an existing lock in the rbtree using the provided pointer. If
+ * one wasn't found - create it.
+ */
+static struct lock_lookup *__get_lock(void *lock)
+{
+ struct rb_node **node, *parent;
+ struct lock_lookup *l;
+
+ ll_pthread_rwlock_rdlock(&locks_rwlock);
+ node = __get_lock_node(lock, &parent);
+ ll_pthread_rwlock_unlock(&locks_rwlock);
+ if (*node) {
+ return rb_entry(*node, struct lock_lookup, node);
+ }
+
+ /* We didn't find the lock, let's create it */
+ l = alloc_lock();
+ if (l == NULL)
+ return NULL;
+
+ l->orig = lock;
+ /*
+ * Currently the name of the lock is the ptr value of the pthread lock,
+ * while not optimal, it makes debugging a bit easier.
+ *
+ * TODO: Get the real name of the lock using libdwarf
+ */
+ sprintf(l->name, "%p", lock);
+ lockdep_init_map(&l->dep_map, l->name, &l->key, 0);
+
+ ll_pthread_rwlock_wrlock(&locks_rwlock);
+ /* This might have changed since the last time we fetched it */
+ node = __get_lock_node(lock, &parent);
+ rb_link_node(&l->node, parent, node);
+ rb_insert_color(&l->node, &locks);
+ ll_pthread_rwlock_unlock(&locks_rwlock);
+
+ return l;
+}
+
+static void __del_lock(struct lock_lookup *lock)
+{
+ ll_pthread_rwlock_wrlock(&locks_rwlock);
+ rb_erase(&lock->node, &locks);
+ ll_pthread_rwlock_unlock(&locks_rwlock);
+ free_lock(lock);
+}
+
+int pthread_mutex_init(pthread_mutex_t *mutex,
+ const pthread_mutexattr_t *attr)
+{
+ int r;
+
+ /*
+ * We keep trying to init our preload module because there might be
+ * code in init sections that tries to touch locks before we are
+ * initialized, in that case we'll need to manually call preload
+ * to get us going.
+ *
+ * Funny enough, kernel's lockdep had the same issue, and used
+ * (almost) the same solution. See look_up_lock_class() in
+ * kernel/lockdep.c for details.
+ */
+ try_init_preload();
+
+ r = ll_pthread_mutex_init(mutex, attr);
+ if (r == 0)
+ /*
+ * We do a dummy initialization here so that lockdep could
+ * warn us if something fishy is going on - such as
+ * initializing a held lock.
+ */
+ __get_lock(mutex);
+
+ return r;
+}
+
+int pthread_mutex_lock(pthread_mutex_t *mutex)
+{
+ int r;
+
+ try_init_preload();
+
+ lock_acquire(&__get_lock(mutex)->dep_map, 0, 0, 0, 2, NULL,
+ (unsigned long)_RET_IP_);
+ /*
+ * Here's the thing with pthread mutexes: unlike the kernel variant,
+ * they can fail.
+ *
+ * This means that the behaviour here is a bit different from what's
+ * going on in the kernel: there we just tell lockdep that we took the
+ * lock before actually taking it, but here we must deal with the case
+ * that locking failed.
+ *
+ * To do that we'll "release" the lock if locking failed - this way
+ * we'll get lockdep doing the correct checks when we try to take
+ * the lock, and if that fails - we'll be back to the correct
+ * state by releasing it.
+ */
+ r = ll_pthread_mutex_lock(mutex);
+ if (r)
+ lock_release(&__get_lock(mutex)->dep_map, 0, (unsigned long)_RET_IP_);
+
+ return r;
+}
+
+int pthread_mutex_trylock(pthread_mutex_t *mutex)
+{
+ int r;
+
+ try_init_preload();
+
+ lock_acquire(&__get_lock(mutex)->dep_map, 0, 1, 0, 2, NULL, (unsigned long)_RET_IP_);
+ r = ll_pthread_mutex_trylock(mutex);
+ if (r)
+ lock_release(&__get_lock(mutex)->dep_map, 0, (unsigned long)_RET_IP_);
+
+ return r;
+}
+
+int pthread_mutex_unlock(pthread_mutex_t *mutex)
+{
+ int r;
+
+ try_init_preload();
+
+ lock_release(&__get_lock(mutex)->dep_map, 0, (unsigned long)_RET_IP_);
+ /*
+ * Just like taking a lock, only in reverse!
+ *
+ * If we fail releasing the lock, tell lockdep we're holding it again.
+ */
+ r = ll_pthread_mutex_unlock(mutex);
+ if (r)
+ lock_acquire(&__get_lock(mutex)->dep_map, 0, 0, 0, 2, NULL, (unsigned long)_RET_IP_);
+
+ return r;
+}
+
+int pthread_mutex_destroy(pthread_mutex_t *mutex)
+{
+ try_init_preload();
+
+ /*
+ * Let's see if we're releasing a lock that's held.
+ *
+ * TODO: Hook into free() and add that check there as well.
+ */
+ debug_check_no_locks_freed(mutex, mutex + sizeof(*mutex));
+ __del_lock(__get_lock(mutex));
+ return ll_pthread_mutex_destroy(mutex);
+}
+
+/* This is the rwlock part, very similar to what happened with mutex above */
+int pthread_rwlock_init(pthread_rwlock_t *rwlock,
+ const pthread_rwlockattr_t *attr)
+{
+ int r;
+
+ try_init_preload();
+
+ r = ll_pthread_rwlock_init(rwlock, attr);
+ if (r == 0)
+ __get_lock(rwlock);
+
+ return r;
+}
+
+int pthread_rwlock_destroy(pthread_rwlock_t *rwlock)
+{
+ try_init_preload();
+
+ debug_check_no_locks_freed(rwlock, rwlock + sizeof(*rwlock));
+ __del_lock(__get_lock(rwlock));
+ return ll_pthread_rwlock_destroy(rwlock);
+}
+
+int pthread_rwlock_rdlock(pthread_rwlock_t *rwlock)
+{
+ int r;
+
+ init_preload();
+
+ lock_acquire(&__get_lock(rwlock)->dep_map, 0, 0, 2, 2, NULL, (unsigned long)_RET_IP_);
+ r = ll_pthread_rwlock_rdlock(rwlock);
+ if (r)
+ lock_release(&__get_lock(rwlock)->dep_map, 0, (unsigned long)_RET_IP_);
+
+ return r;
+}
+
+int pthread_rwlock_tryrdlock(pthread_rwlock_t *rwlock)
+{
+ int r;
+
+ init_preload();
+
+ lock_acquire(&__get_lock(rwlock)->dep_map, 0, 1, 2, 2, NULL, (unsigned long)_RET_IP_);
+ r = ll_pthread_rwlock_tryrdlock(rwlock);
+ if (r)
+ lock_release(&__get_lock(rwlock)->dep_map, 0, (unsigned long)_RET_IP_);
+
+ return r;
+}
+
+int pthread_rwlock_trywrlock(pthread_rwlock_t *rwlock)
+{
+ int r;
+
+ init_preload();
+
+ lock_acquire(&__get_lock(rwlock)->dep_map, 0, 1, 0, 2, NULL, (unsigned long)_RET_IP_);
+ r = ll_pthread_rwlock_trywrlock(rwlock);
+ if (r)
+ lock_release(&__get_lock(rwlock)->dep_map, 0, (unsigned long)_RET_IP_);
+
+ return r;
+}
+
+int pthread_rwlock_wrlock(pthread_rwlock_t *rwlock)
+{
+ int r;
+
+ init_preload();
+
+ lock_acquire(&__get_lock(rwlock)->dep_map, 0, 0, 0, 2, NULL, (unsigned long)_RET_IP_);
+ r = ll_pthread_rwlock_wrlock(rwlock);
+ if (r)
+ lock_release(&__get_lock(rwlock)->dep_map, 0, (unsigned long)_RET_IP_);
+
+ return r;
+}
+
+int pthread_rwlock_unlock(pthread_rwlock_t *rwlock)
+{
+ int r;
+
+ init_preload();
+
+ lock_release(&__get_lock(rwlock)->dep_map, 0, (unsigned long)_RET_IP_);
+ r = ll_pthread_rwlock_unlock(rwlock);
+ if (r)
+ lock_acquire(&__get_lock(rwlock)->dep_map, 0, 0, 0, 2, NULL, (unsigned long)_RET_IP_);
+
+ return r;
+}
+
+__attribute__((constructor)) static void init_preload(void)
+{
+ if (__init_state != done)
+ return;
+
+#ifndef __GLIBC__
+ __init_state = prepare;
+
+ ll_pthread_mutex_init = dlsym(RTLD_NEXT, "pthread_mutex_init");
+ ll_pthread_mutex_lock = dlsym(RTLD_NEXT, "pthread_mutex_lock");
+ ll_pthread_mutex_trylock = dlsym(RTLD_NEXT, "pthread_mutex_trylock");
+ ll_pthread_mutex_unlock = dlsym(RTLD_NEXT, "pthread_mutex_unlock");
+ ll_pthread_mutex_destroy = dlsym(RTLD_NEXT, "pthread_mutex_destroy");
+
+ ll_pthread_rwlock_init = dlsym(RTLD_NEXT, "pthread_rwlock_init");
+ ll_pthread_rwlock_destroy = dlsym(RTLD_NEXT, "pthread_rwlock_destroy");
+ ll_pthread_rwlock_rdlock = dlsym(RTLD_NEXT, "pthread_rwlock_rdlock");
+ ll_pthread_rwlock_tryrdlock = dlsym(RTLD_NEXT, "pthread_rwlock_tryrdlock");
+ ll_pthread_rwlock_wrlock = dlsym(RTLD_NEXT, "pthread_rwlock_wrlock");
+ ll_pthread_rwlock_trywrlock = dlsym(RTLD_NEXT, "pthread_rwlock_trywrlock");
+ ll_pthread_rwlock_unlock = dlsym(RTLD_NEXT, "pthread_rwlock_unlock");
+#endif
+
+ printf("%p\n", ll_pthread_mutex_trylock);fflush(stdout);
+
+ lockdep_init();
+
+ __init_state = done;
+}
--
1.8.1.2
--
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