detect sender of signal (linux, ptrace)

Posted by osgx on Stack Overflow See other posts from Stack Overflow or by osgx
Published on 2010-03-29T16:08:36Z Indexed on 2010/03/29 16:13 UTC
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Filed under:

signal

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signals

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signal-processing

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ptrace

Hello

Can I distinguish signal, between delivered directly to a process and delivered via debugger.

Case 1:

 $ ./process1
 process1 (not ptraced)
 set up handler
 alarm(5);
 ....
 signal is handled and I can parse handler parameters

Case 2:

 $ debugger1 ./process1
 process1 (is ptraced by debugger1)
 set up handler
 alarm(5);
 ...
 signal is catched by debugger1. It resumes process1 with PTRACE_CONT,
  signal_number is 4th parameter of PTRACE_CONT.
 signal is redelivered to process1
 it is handled.

So, how can I detect in signal handler, was it redelivered by debugger or send by system?

OS is Linux, kernel is 2.6.30. Programs are written in plain C.

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