[Crash-utility] Redirect with crash gdb commands

[Bob Montgomery]

I really like to use the x command in crash, as in:

crash-4.0.9> x/256xg 0xffff8801aa9c8000
0xffff8801aa9c8000:     0xffff8800c61541c0      0xffff880145a194c0
0xffff8801aa9c8010:     0xffff88016fa481c0      0xffff88016c7980c0
...


I like it better than the rd command (because of prior familiarity
perhaps?):
crash-4.0.9> rd -x -64 0xffff8801aa9c8000 256
ffff8801aa9c8000:  ffff8800c61541c0 ffff880145a194c0
ffff8801aa9c8010:  ffff88016fa481c0 ffff88016c7980c0
...

But I *really* like crash's ability to pipe and redirect commands, but
that doesn't work with the x command:

crash-4.0.9> x/256xg 0xffff8801aa9c8000 | grep ffff880145a194c0
crash-4.0.9>

But it works with rd:

crash-4.0.9> rd -x -64 0xffff8801aa9c8000 256 | grep ffff880145a194c0
ffff8801aa9c8000:  ffff8800c61541c0 ffff880145a194c0
crash-4.0.9>

Another fun one:
crash-4.0.9> x/256xg 0xffff8801aa9c8000 | head
Argument to arithmetic operation not a number or boolean.


If you redirect the output of x, you get a file containing an error
message:

crash-4.0.9> x/256xg 0xffff8801aa9c8000 >xold.out
crash-4.0.9> !sh
sh-3.2$ cat xold.out
No symbol "xold" in current context.
sh-3.2$

The problem is that the setup of gdb commands in is_gdb_command() with
merge_orig_args set puts the "| thing" or "> thing" back onto the
command it is building to be passed through to gdb.

I first thought that cmd_gdb() passing a NULL, instead of the fp with
the redirection set up, into gdb_pass_through was part of the problem
also, but that seems to be dealt with later in gdb_interface.

There might some other reason for the strange behavior of
merge_orig_args that my testing has not found.  But otherwise, the
attached patch will allow my favorite x command to be sent through pipes
and redirected to files.

Thanks,
Bob Montgomery






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