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    Subject[RFC] [PATCH 2.6.37-rc5-tip 10/20] 10: uprobes: task specific information.

    Uprobes needs to maintain some task specific information include if a
    task is currently uprobed, the currently handing uprobe, any arch
    specific information (for example to handle rip relative instructions),
    the per-task slot where the original instruction is copied to before
    single-stepping.

    Provides routines to create/manage and free the task specific
    information.

    Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
    ---
    include/linux/sched.h | 3 +++
    include/linux/uprobes.h | 25 +++++++++++++++++++++++++
    kernel/fork.c | 4 ++++
    kernel/uprobes.c | 37 +++++++++++++++++++++++++++++++++++++
    4 files changed, 69 insertions(+), 0 deletions(-)

    diff --git a/include/linux/sched.h b/include/linux/sched.h
    index f4e90b6..5a3ebea 100644
    --- a/include/linux/sched.h
    +++ b/include/linux/sched.h
    @@ -1523,6 +1523,9 @@ struct task_struct {
    unsigned long memsw_bytes; /* uncharged mem+swap usage */
    } memcg_batch;
    #endif
    +#ifdef CONFIG_UPROBES
    + struct uprobe_task *utask;
    +#endif
    };

    /* Future-safe accessor for struct task_struct's cpus_allowed. */
    diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
    index 0d4f5e3..14a4fce 100644
    --- a/include/linux/uprobes.h
    +++ b/include/linux/uprobes.h
    @@ -26,12 +26,14 @@
    #include <linux/rbtree.h>
    #ifdef CONFIG_ARCH_SUPPORTS_UPROBES
    #include <asm/uprobes.h>
    +struct uprobe_task_arch_info; /* arch specific task info */
    #else
    /*
    * ARCH_SUPPORTS_UPROBES has not be defined.
    */
    typedef u8 uprobe_opcode_t;
    struct uprobe_arch_info {}; /* arch specific info*/
    +struct uprobe_task_arch_info {}; /* arch specific task info */

    /* Post-execution fixups. Some architectures may define others. */
    #endif /* CONFIG_ARCH_SUPPORTS_UPROBES */
    @@ -85,6 +87,27 @@ struct uprobe {
    u8 insn[MAX_UINSN_BYTES]; /* orig instruction */
    };

    +enum uprobe_task_state {
    + UTASK_RUNNING,
    + UTASK_BP_HIT,
    + UTASK_SSTEP
    +};
    +
    +/*
    + * uprobe_utask -- not a user-visible struct.
    + * Corresponds to a thread in a probed process.
    + * Guarded by uproc->mutex.
    + */
    +struct uprobe_task {
    + unsigned long xol_vaddr;
    + unsigned long vaddr;
    +
    + enum uprobe_task_state state;
    + struct uprobe_task_arch_info tskinfo;
    +
    + struct uprobe *active_uprobe;
    +};
    +
    /*
    * Most architectures can use the default versions of @read_opcode(),
    * @set_bkpt(), @set_orig_insn(), and @is_bkpt_insn();
    @@ -108,6 +131,7 @@ extern int register_uprobe(struct inode *inode, unsigned long offset,
    struct uprobe_consumer *consumer);
    extern void unregister_uprobe(struct inode *inode, unsigned long offset,
    struct uprobe_consumer *consumer);
    +extern void uprobe_free_utask(struct task_struct *tsk);

    struct vm_area_struct;
    extern void uprobe_mmap(struct vm_area_struct *vma);
    @@ -126,6 +150,7 @@ static inline void uprobe_dup_mmap(struct mm_struct *old_mm,
    struct mm_struct *mm)
    {
    }
    +static inline void uprobe_free_utask(struct task_struct *tsk) {}
    static inline void uprobe_mmap(struct vm_area_struct *vma) { }
    #endif /* CONFIG_UPROBES */
    #endif /* _LINUX_UPROBES_H */
    diff --git a/kernel/fork.c b/kernel/fork.c
    index b135d1b..ae99239 100644
    --- a/kernel/fork.c
    +++ b/kernel/fork.c
    @@ -191,6 +191,7 @@ void __put_task_struct(struct task_struct *tsk)
    delayacct_tsk_free(tsk);
    put_signal_struct(tsk->signal);

    + uprobe_free_utask(tsk);
    if (!profile_handoff_task(tsk))
    free_task(tsk);
    }
    @@ -1202,6 +1203,9 @@ static struct task_struct *copy_process(unsigned long clone_flags,
    INIT_LIST_HEAD(&p->pi_state_list);
    p->pi_state_cache = NULL;
    #endif
    +#ifdef CONFIG_UPROBES
    + p->utask = NULL;
    +#endif
    /*
    * sigaltstack should be cleared when sharing the same VM
    */
    diff --git a/kernel/uprobes.c b/kernel/uprobes.c
    index 31867a6..f182fe6 100644
    --- a/kernel/uprobes.c
    +++ b/kernel/uprobes.c
    @@ -745,3 +745,40 @@ void uprobe_mmap(struct vm_area_struct *vma)
    down_write(&mm->mmap_sem);
    }

    +/*
    + * Called with no locks held.
    + * Called in context of a exiting or a exec-ing thread.
    + */
    +void uprobe_free_utask(struct task_struct *tsk)
    +{
    + struct uprobe_task *utask = tsk->utask;
    +
    + if (!utask)
    + return;
    +
    + if (utask->active_uprobe)
    + put_uprobe(utask->active_uprobe);
    + kfree(utask);
    + tsk->utask = NULL;
    +}
    +
    +/*
    + * Allocate a uprobe_task object for the task.
    + * Called when the thread hits a breakpoint for the first time.
    + *
    + * Returns:
    + * - pointer to new uprobe_task on success
    + * - negative errno otherwise
    + */
    +static struct uprobe_task *add_utask(void)
    +{
    + struct uprobe_task *utask;
    +
    + utask = kzalloc(sizeof *utask, GFP_KERNEL);
    + if (unlikely(utask == NULL))
    + return ERR_PTR(-ENOMEM);
    +
    + utask->active_uprobe = NULL;
    + current->utask = utask;
    + return utask;
    +}

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