Messages in this thread | | | Date | Thu, 8 Feb 2018 19:19:10 -0500 | From | Steven Rostedt <> | Subject | Re: [PATCH 09/18] tracing: Add indexing of arguments for function based events |
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On Fri, 9 Feb 2018 08:56:15 +0900 Namhyung Kim <namhyung@kernel.org> wrote:
> On Thu, Feb 08, 2018 at 10:43:43AM -0500, Steven Rostedt wrote: > > On Thu, 8 Feb 2018 19:59:24 +0900 > > Namhyung Kim <namhyung@kernel.org> wrote: > > > > > > @@ -347,6 +361,8 @@ static long long get_arg(struct func_arg *arg, unsigned long val) > > > > char buf[8]; > > > > int ret; > > > > > > > > + val += arg->index; > > > > + > > > > if (!arg->indirect) > > > > return val; > > > > > > So this also works without the indirect, and just add the immediate to > > > the value. > > > > Not sure what you are asking here. The immediate adds to the current > > value, where as the indirect will then look what's at that location. > > I expected that the immediate offset is only meaningful with the > indirect (dereference) as the doc says just about it. So I asked it > was intentional or not. >
Yes it is intentional, but rather useless without an indirect. I mean, you could just add to the value if you want :-)
The reason it doesn't need the indirect is because there's some types (arrays and strings) that don't need the indirect. For example, with the net_device with the perm_addr at 558 bytes away:
echo 'ip_rcv(NULL, x8[6] perm_addr+558)' > function_events
produces:
<idle>-0 [003] ..s3 1809.074329: __netif_receive_skb_core->ip_rcv(perm_addr=b4,b5,2f,ce,18,65)
-- Steve
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