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Subject[PATCH v4 3.0-rc2-tip 9/22] 9: 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 | 9 ++++++---
include/linux/uprobes.h | 25 +++++++++++++++++++++++++
kernel/fork.c | 4 ++++
kernel/uprobes.c | 38 ++++++++++++++++++++++++++++++++++++++
4 files changed, 73 insertions(+), 3 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index a837b20..9af9c99 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1304,9 +1304,9 @@ struct task_struct {
unsigned long stack_canary;
#endif

- /*
+ /*
* pointers to (original) parent process, youngest child, younger sibling,
- * older sibling, respectively. (p->father can be replaced with
+ * older sibling, respectively. (p->father can be replaced with
* p->real_parent->pid)
*/
struct task_struct *real_parent; /* real parent process */
@@ -1561,6 +1561,9 @@ struct task_struct {
#ifdef CONFIG_HAVE_HW_BREAKPOINT
atomic_t ptrace_bp_refcnt;
#endif
+#ifdef CONFIG_UPROBES
+ struct uprobe_task *utask;
+#endif
};

/* Future-safe accessor for struct task_struct's cpus_allowed. */
@@ -2127,7 +2130,7 @@ static inline int dequeue_signal_lock(struct task_struct *tsk, sigset_t *mask, s
spin_unlock_irqrestore(&tsk->sighand->siglock, flags);

return ret;
-}
+}

extern void block_all_signals(int (*notifier)(void *priv), void *priv,
sigset_t *mask);
diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
index fc2f9d2..821e000 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 is not defined.
*/
typedef u8 uprobe_opcode_t;
struct uprobe_arch_info {}; /* arch specific info*/
+struct uprobe_task_arch_info {}; /* arch specific task info */
#endif /* CONFIG_ARCH_SUPPORTS_UPROBES */

/* Post-execution fixups. Some architectures may define others. */
@@ -77,6 +79,27 @@ struct uprobe {
int copy;
};

+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();
@@ -111,6 +134,7 @@ extern int register_uprobe(struct inode *inode, loff_t offset,
struct uprobe_consumer *consumer);
extern void unregister_uprobe(struct inode *inode, loff_t offset,
struct uprobe_consumer *consumer);
+extern void free_uprobe_utask(struct task_struct *tsk);

struct vm_area_struct;
extern int mmap_uprobe(struct vm_area_struct *vma);
@@ -133,5 +157,6 @@ static inline int mmap_uprobe(struct vm_area_struct *vma)
{
return 0;
}
+static inline void free_uprobe_utask(struct task_struct *tsk) {}
#endif /* CONFIG_UPROBES */
#endif /* _LINUX_UPROBES_H */
diff --git a/kernel/fork.c b/kernel/fork.c
index f6c7cb1..bf5999b 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -196,6 +196,7 @@ void __put_task_struct(struct task_struct *tsk)
delayacct_tsk_free(tsk);
put_signal_struct(tsk->signal);

+ free_uprobe_utask(tsk);
if (!profile_handoff_task(tsk))
free_task(tsk);
}
@@ -1268,6 +1269,9 @@ 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 93a53c0..2bb2bd7 100644
--- a/kernel/uprobes.c
+++ b/kernel/uprobes.c
@@ -1022,3 +1022,41 @@ mmap_out:
down_write(&mm->mmap_sem);
return ret;
}
+
+/*
+ * Called with no locks held.
+ * Called in context of a exiting or a exec-ing thread.
+ */
+void free_uprobe_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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