During fault locating, the file name needs to be printed based on the
dentry  address. The offset needs to be calculated each time, which
is troublesome. Similar to printk, kprobe support print type '%pd' for
print dentry's name. For example "name=$arg1:%pd" casts the `$arg1`
as (struct dentry *), dereferences the "d_name.name" field and stores
it to "name" argument as a kernel string.
Here is an example:
[tracing]# echo 'p:testprobe dput name=$arg1:%pd' > kprobe_events
[tracing]# echo 1 > events/kprobes/testprobe/enable
[tracing]# grep -q "1" events/kprobes/testprobe/enable
[tracing]# echo 0 > events/kprobes/testprobe/enable
[tracing]# cat trace | grep "enable"
	    bash-14844   [002] ..... 16912.889543: testprobe: (dput+0x4/0x30) name="enable"
            grep-15389   [003] ..... 16922.834182: testprobe: (dput+0x4/0x30) name="enable"
            grep-15389   [003] ..... 16922.836103: testprobe: (dput+0x4/0x30) name="enable"
            bash-14844   [001] ..... 16931.820909: testprobe: (dput+0x4/0x30) name="enable"

Note that this expects the given argument (e.g. $arg1) is an address of struct
dentry. User must ensure it.

Link: https://lore.kernel.org/all/20240322064308.284457-2-yebin10@huawei.com/Signed-off-by: Ye Bin <yebin10@huawei.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>