[Bug 162774] strace ignores int3 SIGTRAP

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https://bugzilla.redhat.com/show_bug.cgi?id=162774





--- Comment #6 from Denys Vlasenko <dvlasenk at redhat.com>  2008-09-10 08:53:06 EDT ---
Created an attachment (id=316309)
 --> (https://bugzilla.redhat.com/attachment.cgi?id=316309)
Proof-of-concept patch

This patch sets PTRACE_O_TRACESYSGOOD option for traced child. Kernel will flag
ptrace-related signals by setting bit 0x80 in signo.

Patch contains some debugging code nad comments which are easy to spot.

Patch is run-tested. int3 example:

# /root/srcdevel/strace/fix/strace.t1/strace ./int3
ptrace(PTRACE_SETOPTIONS, ..., PTRACE_O_TRACESYSGOOD) successful
execve("./int3", ["./int3"], [/* 54 vars */]bogus SIGTRAP: made it SIGTRAP80
) = 0
--- SIGTRAP (Trace/breakpoint trap) @ 0 (0) ---
+++ killed by SIGTRAP +++

Also tried running e.g. "ls -l" and it seems that stracing of normal programs
is not affected.

In this patch, "strace -p" is not using PTRACE_O_TRACESYSGOOD trick yet.

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