<s>
In	O
computing	O
,	O
rr	B-Application
is	O
a	O
debugging	B-Application
tool	I-Application
for	O
Linux	O
designed	O
to	O
record	B-Application
and	I-Application
replay	I-Application
program	I-Application
execution	I-Application
.	O
</s>
<s>
During	O
the	O
replay	O
phase	O
,	O
rr	B-Application
provides	O
an	O
enhanced	O
gdb	B-Language
debugging	O
experience	O
that	O
supports	O
reverse	O
execution	O
.	O
</s>
<s>
rr	B-Application
was	O
originally	O
developed	O
by	O
Mozilla	B-Operating_System
to	O
debug	O
Mozilla	B-Application
Firefox	I-Application
on	O
commodity	O
hardware	O
and	O
software	O
.	O
</s>
<s>
rr	B-Application
is	O
now	O
widely	O
used	O
outside	O
Mozilla	B-Operating_System
and	O
capable	O
of	O
debugging	O
software	O
such	O
as	O
Google	B-Application
Chrome	I-Application
,	O
QEMU	B-Application
,	O
and	O
LibreOffice	B-Application
.	O
</s>
<s>
rr	B-Application
is	O
free	B-Application
software	I-Application
.	O
</s>
<s>
During	O
the	O
recording	O
phase	O
,	O
rr	B-Application
records	O
all	O
inputs	O
to	O
a	O
Linux	O
process	O
group	O
from	O
the	O
kernel	O
,	O
as	O
well	O
as	O
nondeterministic	O
CPU	O
effects	O
(	O
such	O
as	O
rdtsc	B-Device
)	O
.	O
</s>
<s>
During	O
replay	O
rr	B-Application
will	O
act	O
as	O
a	O
gdbserver	B-Application
providing	O
a	O
gdb	B-Language
experience	O
capable	O
of	O
reverse-execution	O
.	O
</s>
<s>
Because	O
a	O
bug	O
can	O
be	O
replayed	O
over	O
and	O
over	O
again	O
,	O
rr	B-Application
enables	O
new	O
methods	O
of	O
debugging	O
issues	O
that	O
are	O
very	O
difficult	O
to	O
solve	O
with	O
traditional	O
debuggers	B-Application
.	O
</s>
<s>
rr	B-Application
's	O
design	O
is	O
documented	O
in	O
the	O
paper	O
,	O
with	O
more	O
details	O
in	O
.	O
</s>
