Gilles Chanteperdrix wrote:
> Jan Kiszka wrote:
>> Christoph Permes wrote:
>>> Hi,
>>>
>>> I've created a patch that provides a workaround for the segmentation
>>> fault:
>>>
>>> --- a/src/rtdk/rt_print.c 2009-05-21 16:34:54.000000000 +0200
>>> +++ b/src/rtdk/rt_print.c 2009-09-04 10:09:19.000000000 +0200
>>> @@ -40,6 +40,7 @@
>>> struct entry_head {
>>> FILE *dest;
>>> uint32_t seq_no;
>>> + uint32_t len;
>>> char text[1];
>>> } __attribute__((packed));
>>>
>>> @@ -113,6 +114,7 @@
>>> /* Write out empty entry */
>>> head = buffer->ring + write_pos;
>>> head->seq_no = __seq_no;
>>> + head->len = 0;
>>> head->text[0] = 0;
>>>
>>> /* Forward to the ring buffer start */
>>> @@ -146,6 +148,7 @@
>>> /* If we were able to write some text, finalise the entry */
>>> if (len > 0) {
>>> head->seq_no = ++__seq_no;
>>> + head->len = len;
>>> head->dest = stream;
>>>
>>> /* Move forward by text and head length */
>>> @@ -158,6 +161,7 @@
>>> /* An empty entry marks the wrap-around */
>>> head = buffer->ring + write_pos;
>>> head->seq_no = __seq_no;
>>> + head->len = 0;
>>> head->text[0] = 0;
>>>
>>> write_pos = 0;
>>> @@ -373,7 +377,7 @@
>>>
>>> read_pos = buffer->read_pos;
>>> head = buffer->ring + read_pos;
>>> - len = strlen(head->text);
>>> + len = head->len;
>>>
>>> if (len) {
>>> /* Print out non-empty entry and proceed */
>>>
>>> With this patch I get no segfaults anymore, but of course it would be
>>> interesting why parts of the ring buffer are overwritten with null
>>> characters.
>>>
>> Frankly, I'm suspecting some issue in your application here - at least
>> as long as you do not have some broken-out test case for us...
>
> Would not it be possible to mprotect the rtdk buffer when it is not used
> in order to catch any write to it outside of rtdk functions?
>
Hmm, good idea, should work. Once set up, only rt_vsnprintf requires
write access to the ring.
Jan
--
Siemens AG, Corporate Technology, CT SE 2
Corporate Competence Center Embedded Linux
_______________________________________________
Xenomai-help mailing list
[email protected]
https://mail.gna.org/listinfo/xenomai-help
