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Date: Mon, 25 May 2015 16:33:09 +0800
From: He Kuang <hekuang@...wei.com>
To: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
<wangnan0@...wei.com>, <paulus@...ba.org>,
<a.p.zijlstra@...llo.nl>, <mingo@...hat.com>, <acme@...nel.org>,
<namhyung@...nel.org>, <jolsa@...nel.org>, <ast@...mgrid.com>,
<dsahern@...il.com>, <brendan.d.gregg@...il.com>,
<daniel@...earbox.net>
CC: <lizefan@...wei.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v2 09/15] perf probe: Support $params without
debuginfo
hi,
On 2015/5/24 16:49, Masami Hiramatsu wrote:
> On 2015/05/24 17:28, He Kuang wrote:
>> When probing at function entry, fallback $params to calling regs if no
>> debuginfo is provided.
>>
>> Before this path:
>> $ perf probe -v --add='generic_perform_write $params'
>> ...
>> Added new event:
>> Writing event: p:probe/generic_perform_write _stext+1246632 $params
>> [86152.161204] Parse error at argument[0]. (-22)
>> Failed to write event: Invalid argument
>> Error: Failed to add events. Reason: Invalid argument (Code: -22)
>>
>> After this patch:
>> $ perf probe -v --add='generic_perform_write $params'
>> ...
>> Could not open debuginfo. Try to use symbols.
>> ...
>> Added new event:
>> Writing event: p:probe/generic_perform_write _stext+1246632 %di %si %dx %cx %r8 %r9
>> probe:generic_perform_write (on generic_perform_write with $params)
>>
>> You can now use it in all perf tools, such as:
>>
>> perf record -e probe:generic_perform_write -aR sleep 1
>>
>> $ perf record -e probe:generic_perform_write dd if=/dev/zero of=/mnt/data/test bs=4k count=3
>
> NAK, this should not work on x86-32 and we don't know how many registers are used.
> I think $params special handler should be used only with debuginfo, since $params
> ensures user to save function parameters with its name. If we can't do that, we
> should accept that.
>
> If you need to handle register arguments, you should introduce new $regparams instead
Yes, $regparam is more appropriate.
> of $params. (however, that still not work correctly on x86-32)
>
> Hmm, we also need $regs to record all registers.
Right, I learnt regparm(3) is mandatory in x86_32, according to rules,
the first three args will go to regparm(ax, dx, cx). But we should not
refer arg1~3 to ax, dx, cx because of 64bit parameters (other reasons?).
Consider this keyword is used for generating bpf prologue which fetches
formal parameters when no debuginfo is provided, for this purpose, we can:
1) We just help fetch the $regs or $regparms(If the keyword is
$regparms, ax/dx/cx is fetched, nothing related to args) to bpf arglists
and leave the rest things to bpf prog writer.
2) Keep that on platforms like x86_64 and skip this feature on
platforms like x86_32.
or any other suggestions?
Thanks
>
> Thank you,
>
>
>>
>> $ perf script
>> dd 1149 [000] 18574.762652: probe:generic_perform_write: (ffffffff81130770) arg1=0xffff88007c37f600 arg2=0xffff88007ca87e70 arg3=0x0 arg4=0x0 arg5=0x556062e3 arg6=0x12a8010
>> dd 1149 [000] 18574.762652: probe:generic_perform_write: (ffffffff81130770) arg1=0xffff88007c37f600 arg2=0xffff88007ca87e70 arg3=0x1000 arg4=0x0 arg5=0x556062e3 arg6=0x12a8010
>> dd 1149 [000] 18574.762652: probe:generic_perform_write: (ffffffff81130770) arg1=0xffff88007c37f600 arg2=0xffff88007ca87e70 arg3=0x2000 arg4=0x0 arg5=0x556062e3 arg6=0x12a8010
>>
>> Signed-off-by: He Kuang <hekuang@...wei.com>
>> ---
>> tools/perf/util/probe-event.c | 42 ++++++++++++++++++++++++++++++++++++++++++
>> 1 file changed, 42 insertions(+)
>>
>> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
>> index d05b77c..7f9f431 100644
>> --- a/tools/perf/util/probe-event.c
>> +++ b/tools/perf/util/probe-event.c
>> @@ -46,6 +46,7 @@
>> #include "probe-event.h"
>> #include "probe-finder.h"
>> #include "session.h"
>> +#include <dwarf-regs.h>
>>
>> #define MAX_CMDLEN 256
>> #define PERFPROBE_GROUP "probe"
>> @@ -286,6 +287,14 @@ static void clear_probe_trace_events(struct probe_trace_event *tevs, int ntevs)
>> clear_probe_trace_event(tevs + i);
>> }
>>
>> +static bool perf_probe_is_function_entry(struct perf_probe_event *pev)
>> +{
>> + if (pev->point.file || pev->point.line || pev->point.lazy_line)
>> + return false;
>> +
>> + return true;
>> +}
>> +
>> #ifdef HAVE_DWARF_SUPPORT
>> /*
>> * Some binaries like glibc have special symbols which are on the symbol
>> @@ -1225,6 +1234,33 @@ static int parse_perf_probe_point(char *arg, struct perf_probe_event *pev)
>> return 0;
>> }
>>
>> +static char *parse_perf_probe_param(void)
>> +{
>> + int i = 0;
>> + struct strbuf sb;
>> + bool first = true;
>> + const char *reg_str;
>> +
>> + strbuf_init(&sb, 16);
>> +
>> + while (1) {
>> + reg_str = get_arch_calling_reg_str(i++);
>> + if (!reg_str)
>> + break;
>> +
>> + if (first) {
>> + strbuf_addf(&sb, "%s", reg_str);
>> + first = false;
>> + } else
>> + strbuf_addf(&sb, " %s", reg_str);
>> + }
>> +
>> + if (first)
>> + strbuf_add(&sb, "", 1);
>> +
>> + return strbuf_detach(&sb, NULL);
>> +}
>> +
>> /* Parse perf-probe event argument */
>> static int parse_perf_probe_arg(char *str, struct perf_probe_arg *arg)
>> {
>> @@ -2543,6 +2579,12 @@ static int find_probe_trace_events_from_map(struct perf_probe_event *pev,
>> goto nomem_out;
>> }
>> for (i = 0; i < tev->nargs; i++) {
>> + if (perf_probe_is_function_entry(pev) &&
>> + !strcmp(pev->args[i].var, "$params")) {
>> + tev->args[i].value = parse_perf_probe_param();
>> + continue;
>> + }
>> +
>> if (pev->args[i].name)
>> tev->args[i].name =
>> strdup_or_goto(pev->args[i].name,
>>
>
>
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