fake_execve() and -i option

[Johan Aurér]

Hi

This may be a known bug, but I've noticed that running strace with -i 
("print instruction pointer at time of syscall") can result in a failed 
upeek() call at the very beginning:

        # strace-4.5.6/strace -i /bin/ls
        upeek: ptrace(PTRACE_PEEKUSER,12475,48,0): No such process
        [????????] execve("/bin/ls", ["/bin/ls"], [/* 46 vars */]) = 0
        ....

I haven't seen this problem under i386/Linux 2.6.x, but it happens 
frequently under 2.4.x (and also under CRIS/Linux).

What happens is that when fake_execve() is called, the child process may 
or may not have stopped (it stops as a result of execve). If it hasn't 
stopped then obviously you can't do PTRACE_PEEKUSER. But with -i, strace 
tries to read the PC anyway causing the failed upeek().

Actually, I don't think strace should be trying to read the PC here in the 
first place. Printing the PC for the initial execve syscall doesn't seem 
very useful to me.

-- 
aurer at axis.com