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SubjectRe: [PATCH 2/2] trace_uprobe: Simplify probes_seq_show()
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On 02/08/2018 09:13 AM, Ravi Bangoria wrote:
>
> On 02/08/2018 08:59 AM, Kees Cook wrote:
>> On Tue, Feb 6, 2018 at 8:34 PM, Ravi Bangoria
>> <ravi.bangoria@linux.vnet.ibm.com> wrote:
>>> Simplify probes_seq_show() function. We are using %lx to display
>>> the offset and we don't prepend unnecessary 0s in the offset.
>>>
>>> Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
>>> ---
>>> kernel/trace/trace_uprobe.c | 21 +++------------------
>>> 1 file changed, 3 insertions(+), 18 deletions(-)
>>>
>>> diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
>>> index c2c965398893..c12a3957e1ee 100644
>>> --- a/kernel/trace/trace_uprobe.c
>>> +++ b/kernel/trace/trace_uprobe.c
>>> @@ -602,24 +602,9 @@ static int probes_seq_show(struct seq_file *m, void *v)
>>> char c = is_ret_probe(tu) ? 'r' : 'p';
>>> int i;
>>>
>>> - seq_printf(m, "%c:%s/%s", c, tu->tp.call.class->system,
>>> - trace_event_name(&tu->tp.call));
>>> - seq_printf(m, " %s:", tu->filename);
>>> -
>>> - /* Don't print "0x (null)" when offset is 0 */
>>> - if (tu->offset) {
>>> - seq_printf(m, "0x%lx", tu->offset);
>>> - } else {
>>> - switch (sizeof(void *)) {
>>> - case 4:
>>> - seq_printf(m, "0x00000000");
>>> - break;
>>> - case 8:
>>> - default:
>>> - seq_printf(m, "0x0000000000000000");
>>> - break;
>>> - }
>>> - }
>>> + seq_printf(m, "%c:%s/%s %s:0x%lx", c, tu->tp.call.class->system,
>>> + trace_event_name(&tu->tp.call), tu->filename,
>>> + tu->offset);
>> To keep the prepended zeros (and avoid the redundant 0x prefix):
>>
>> "...%#0*lx...", ... sizeof(void *) * 2, tu->offset);
>>
>> As in:
>>
>> + seq_printf(m, "%c:%s/%s %s:%#0*lx", c, tu->tp.call.class->system,
>> + trace_event_name(&tu->tp.call), tu->filename,
>> + sizeof(void *) * 2, tu->offset);
> This is useful, thanks Kees.
>
> @Wang, Do we really need those 0s? Won't just 0x0 should
> suffice? Here is the sample output...
>
>   # echo "p:probe_a/main /tmp/a.out:0x0" > uprobe_events
>
> Before patch:
>   # cat uprobe_events
>     p:probe_a/main /tmp/a.out:0x0000000000000000
>
> After patch:
>   # cat uprobe_events
>     p:probe_a/main /tmp/a.out:0x0

Wang, ping :)

Kees, I don't hear back from Wang and no one has reported any issues with
the patches yet. Can I have your Acked-by?

Thanks,
Ravi

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