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RE: [Patch 2/3][Djprobe] Djprobe update for linux-2.6.14-mm1
- From: "Zhang, Yanmin" <yanmin dot zhang at intel dot com>
- To: "Masami Hiramatsu" <hiramatu at sdl dot hitachi dot co dot jp>, <systemtap at sources dot redhat dot com>
- Cc: "Satoshi Oshima" <soshima at redhat dot com>, "Yumiko Sugita" <sugita at sdl dot hitachi dot co dot jp>, "Hideo Aoki" <haoki at redhat dot com>, "Keshavamurthy, Anil S" <anil dot s dot keshavamurthy at intel dot com>
- Date: Fri, 11 Nov 2005 10:33:02 +0800
- Subject: RE: [Patch 2/3][Djprobe] Djprobe update for linux-2.6.14-mm1
>>-----Original Message-----
>>From: systemtap-owner@sourceware.org [mailto:systemtap-owner@sourceware.org]
>>On Behalf Of Masami Hiramatsu
>>Sent: 2005年11月8日 21:26
>>To: systemtap@sources.redhat.com
>>Cc: Satoshi Oshima; Yumiko Sugita; Hideo Aoki
>>Subject: [Patch 2/3][Djprobe] Djprobe update for linux-2.6.14-mm1
>>
>>Hi,
>>
>>This patch is the architecture independant part of djprobe.
>>+static inline
>>+ struct djprobe_instance *__create_djprobe_instance(struct djprobe *djp,
>>+ void *addr, int size)
>>+{
>>+ struct djprobe_instance *djpi;
>>+ /* allocate a new instance */
>>+ djpi = kcalloc(1, sizeof(struct djprobe_instance), GFP_ATOMIC);
>>+ if (djpi == NULL) {
>>+ goto out;
>>+ }
>>+ /* allocate stub */
>>+ djpi->stub.insn = __get_insn_slot(&djprobe_insn_pages);
>>+ if (djpi->stub.insn == NULL) {
[YM] If coming here, djpi->plist is not initiated. So __free_djprobe_instance=>hlist_del will cause panic. How about to move the INIT_LIST_HEAD(&djpi->plist) just after kcalloc?
>>+ __free_djprobe_instance(djpi);
>>+ djpi = NULL;
>>+ goto out;
>>+ }
>>+
>>+ /* attach */
>>+ djp->inst = djpi;
>>+ INIT_LIST_HEAD(&djpi->plist);
>>+ list_add_rcu(&djp->plist, &djpi->plist);
>>+ djpi->kp.addr = addr;
>>+ djpi->kp.pre_handler = djprobe_pre_handler;
>>+ arch_prepare_djprobe_instance(djpi, size);
>>+
>>+ INIT_HLIST_NODE(&djpi->hlist);
>>+ hlist_add_head(&djpi->hlist,
>>&djprobe_inst_table[hash_djprobe(addr)]);
>>+ out:
>>+ return djpi;
>>+}
>>+
>>+static struct djprobe_instance *__kprobes __get_djprobe_instance(void
>>*addr,
>>+ int size)
>>+{
>>+ struct djprobe_instance *djpi;
>>+ struct hlist_node *node;
>>+ unsigned long idx, eidx;
>>+
>>+ idx = hash_djprobe(addr - ARCH_STUB_INSN_MAX);
>>+ eidx = ((hash_djprobe(addr + size) + 1) & DJPROBE_TABLE_MASK);
>>+ do {
>>+ hlist_for_each_entry(djpi, node, &djprobe_inst_table[idx],
>>+ hlist) {
>>+ if (((long)addr <
>>+ (long)djpi->kp.addr + DJPI_ARCH_SIZE(djpi))
>>+ && ((long)djpi->kp.addr < (long)addr + size)) {
>>+ return djpi;
>>+ }
>>+ }
>>+ idx = ((idx + 1) & DJPROBE_TABLE_MASK);
>>+ }while (idx != eidx);
>>+
>>+ return NULL;
>>+}
>>+
>>+struct djprobe_instance *__kprobes get_djprobe_instance(void *addr, int
>>size)
>>+{
>>+ struct djprobe_instance *djpi;
>>+ down(&djprobe_mutex);
>>+ djpi = __get_djprobe_instance(addr, size);
>>+ up(&djprobe_mutex);
>>+ return djpi;
>>+}
>>+
>>+/* This work function invoked while djprobe_mutex is locked. */
>>+static void __kprobes __work_check_safety(void *data)
>>+{
>>+ if (atomic_dec_and_test(&djprobe_count)) {
>>+ wake_up_all(&djprobe_wqh);
>>+ }
>>+}
>>+
>>+static void __kprobes __check_safety(void)
>>+{
>>+ int cpu;
>>+ struct work_struct *wk;
>>+ lock_cpu_hotplug();
>>+ atomic_set(&djprobe_count, num_online_cpus() - 1);
>>+ for_each_online_cpu(cpu) {
>>+ if (cpu == smp_processor_id())
>>+ continue;
>>+ wk = &per_cpu(djprobe_works, cpu);
>>+ INIT_WORK(wk, __work_check_safety, NULL);
>>+ schedule_delayed_work_on(cpu, wk, 0);
>>+ }
>>+ wait_event(djprobe_wqh, (atomic_read(&djprobe_count) == 0));
>>+ unlock_cpu_hotplug();
>>+}
>>+
>>+int __kprobes register_djprobe(struct djprobe *djp, void *addr, int size)
>>+{
>>+ struct djprobe_instance *djpi;
>>+ struct kprobe *kp;
>>+ int ret = 0, i;
>>+
>>+ BUG_ON(in_interrupt());
>>+
>>+ if (size > ARCH_STUB_INSN_MAX || size < ARCH_STUB_INSN_MIN)
>>+ return -EINVAL;
>>+
>>+ if ((ret = in_kprobes_functions((unsigned long)addr)) != 0)
>>+ return ret;
>>+
>>+ down(&djprobe_mutex);
>>+ INIT_LIST_HEAD(&djp->plist);
>>+ /* check confliction with other djprobes */
>>+ djpi = __get_djprobe_instance(addr, size);
>>+ if (djpi) {
>>+ if (djpi->kp.addr == addr) {
>>+ djp->inst = djpi; /* add to another instance */
>>+ list_add_rcu(&djp->plist, &djpi->plist);
>>+ } else {
>>+ ret = -EEXIST; /* other djprobes were inserted */
>>+ }
>>+ goto out;
>>+ }
>>+ djpi = __create_djprobe_instance(djp, addr, size);
>>+ if (djpi == NULL) {
>>+ ret = -ENOMEM;
>>+ goto out;
>>+ }
>>+
>>+ /* check confliction with kprobes */
>>+ for (i = 0; i < size; i++) {
>>+ kp = get_kprobe((void *)((long)addr + i));
[YM] There is a race between get_kprobe and register_kprobe without locking kprobe_lock. Could register_kprobe to check if the address is in a JTPR of registered djprobe? I think djprobe and kprobe could share the same spin_lock, namely kprobe_lock.
>>+ if (kp != NULL) {
>>+ ret = -EEXIST; /* a kprobes were inserted */
>>+ goto fail;
>>+ }
>>+ }
>>+ ret = register_kprobe(&djpi->kp);
>>+ if (ret < 0) {
>>+ fail:
>>+ djpi->kp.addr = NULL;
>>+ djp->inst = NULL;
>>+ list_del_rcu(&djp->plist);
>>+ __free_djprobe_instance(djpi);
>>+ } else {
>>+ __check_safety();
>>+ arch_install_djprobe_instance(djpi);
>>+ }
>>+ out:
>>+ up(&djprobe_mutex);
>>+ return ret;