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Subject[PATCH v6 3.2-rc1 2/28] Uprobes: Allow multiple consumers for an uprobe.

Since there is a unique uprobe for a inode, offset combination, provide
an ability for users to have more than one consumer for a uprobe.

Each consumer will define a handler and an optional filter. Handler
specifies the routine to run on hitting a probepoint. Filter allows to
selectively run the handler on hitting the probepoint. Handler/Filter
will be relevant on probehit.

Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
---
Changelog:(Since v5)
modified del_consumer as per comments from Peter.

include/linux/uprobes.h | 13 +++++++++++++
kernel/uprobes.c | 35 +++++++++++++++++++++++++++++++++++
2 files changed, 48 insertions(+), 0 deletions(-)
diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
index bfb85c4..bf31f7c 100644
--- a/include/linux/uprobes.h
+++ b/include/linux/uprobes.h
@@ -25,9 +25,22 @@

#include <linux/rbtree.h>

+struct uprobe_consumer {
+ int (*handler)(struct uprobe_consumer *self, struct pt_regs *regs);
+ /*
+ * filter is optional; If a filter exists, handler is run
+ * if and only if filter returns true.
+ */
+ bool (*filter)(struct uprobe_consumer *self, struct task_struct *task);
+
+ struct uprobe_consumer *next;
+};
+
struct uprobe {
struct rb_node rb_node; /* node in the rb tree */
atomic_t ref;
+ struct rw_semaphore consumer_rwsem;
+ struct uprobe_consumer *consumers;
struct inode *inode; /* Also hold a ref to inode */
loff_t offset;
};
diff --git a/kernel/uprobes.c b/kernel/uprobes.c
index cacf333..2c92b9a 100644
--- a/kernel/uprobes.c
+++ b/kernel/uprobes.c
@@ -149,6 +149,7 @@ static struct uprobe *alloc_uprobe(struct inode *inode, loff_t offset)

uprobe->inode = igrab(inode);
uprobe->offset = offset;
+ init_rwsem(&uprobe->consumer_rwsem);

/* add to uprobes_tree, sorted on inode:offset */
cur_uprobe = insert_uprobe(uprobe);
@@ -162,6 +163,40 @@ static struct uprobe *alloc_uprobe(struct inode *inode, loff_t offset)
return uprobe;
}

+/* Returns the previous consumer */
+static struct uprobe_consumer *add_consumer(struct uprobe *uprobe,
+ struct uprobe_consumer *consumer)
+{
+ down_write(&uprobe->consumer_rwsem);
+ consumer->next = uprobe->consumers;
+ uprobe->consumers = consumer;
+ up_write(&uprobe->consumer_rwsem);
+ return consumer->next;
+}
+
+/*
+ * For uprobe @uprobe, delete the consumer @consumer.
+ * Return true if the @consumer is deleted successfully
+ * or return false.
+ */
+static bool del_consumer(struct uprobe *uprobe,
+ struct uprobe_consumer *consumer)
+{
+ struct uprobe_consumer **con;
+ bool ret = false;
+
+ down_write(&uprobe->consumer_rwsem);
+ for (con = &uprobe->consumers; *con; con = &(*con)->next) {
+ if (*con == consumer) {
+ *con = consumer->next;
+ ret = true;
+ break;
+ }
+ }
+ up_write(&uprobe->consumer_rwsem);
+ return ret;
+}
+
static void delete_uprobe(struct uprobe *uprobe)
{
unsigned long flags;


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