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SubjectRe: [PATCH 2/2] trace_uprobe: Simplify probes_seq_show()
On Tue, Mar 6, 2018 at 12:12 AM, Ravi Bangoria
<ravi.bangoria@linux.vnet.ibm.com> wrote:
>
>
> 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?

I didn't see a v2 of these patches with the output fixed?

-Kees

--
Kees Cook
Pixel Security

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