Re: Segmentation Fault: Task died at uprobe probepoint

[Srikar Dronamraju <srikar at linux dot vnet dot ibm dot com>]

Hi, 

> 
> probe process("/home/gdhiman/tests/uprobe-test").begin
> {
>         printf("uprobe-test begin!!\n")
> }
> 
> probe process("/home/gdhiman/tests/uprobe-test").function("test_func")
> {
>         printf("test_func called!\n");
>         log($$parms);
> }
> 
> The uprobe-test code is as follows:
> 
> int test_func(int i)
> {
>         printf("%d\n", i);
>         return j;
	        ^^^^^ 
	Guess you meant "return i;"

> }
> 
> int main()
> {
>         int i;
>         i = test_func(5);
>         return 0;
> }
> 
> 

> Then I ran the script as root using stap -v test.stp; it is compiled
> and inserted successfully. I see the following message if I do dmesg:
> [ 1694.148460] stap_9736f2321b446f9fc03126194f89aac2_1643: systemtap:
> 1.2/0.131, base: ffffffffa0010000, memory
> 136data/29text/10ctx/13net/34alloc kb, probes: 2

Looks to me that you are using a pretty recent systemtap with a pretty 
old elfutils. Is is possible to try building systemtap with a later
version of elfutils?

> However, when i actually run uprobe-test, although both the probes
> fire successfully, the task generates a segmentation fault and dies on
> the 'test_func' probe. I see the following message on doing dmesg:

> [ 1709.650827] Task died at uprobe probepoint:  pid/tgid = 3934/3934,
> probepoint = 0x400517


This means that the process died before the uprobe operation completed.
i.e either it was still running the handler or singlestep operation
hadnt occurred.  
- Did you try using the core with gdb? Does address in bt and
  disassemble output of test_func show the same address?

I am not able to see this problem. (I am running on a different kernel)

--
Regards
Srikar