From: Mathieu Poirier <mathieu.poirier@linaro.org>
To: Leo Yan <leo.yan@linaro.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
Mike Leach <mike.leach@linaro.org>,
Robert Walker <robert.walker@arm.com>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org,
Coresight ML <coresight@lists.linaro.org>
Subject: Re: [PATCH v6 8/8] perf cs-etm: Set sample flags for exception return packet
Date: Wed, 23 Jan 2019 14:51:14 -0700 [thread overview]
Message-ID: <20190123215114.GH620@xps15> (raw)
In-Reply-To: <20190119014347.27441-9-leo.yan@linaro.org>
On Sat, Jan 19, 2019 at 09:43:47AM +0800, Leo Yan wrote:
> When return from exception, we need to distinguish if it's system call
> return or for other type exceptions for setting sample flags. Due to
> the exception return packet doesn't contain exception number, so we
> cannot decide sample flags based on exception number.
>
> On the other hand, the exception return packet is followed by an
> instruction range packet; this range packet deliveries the start address
> after exception handling, we can check if it is a SVC instruction just
> before the start address. If there has one SVC instruction is found
> ahead the return address, this means it's an exception return for system
> call; otherwise it is an normal return for other exceptions.
>
> This patch is to set sample flags for exception return packet, firstly
> it simply set sample flags as PERF_IP_FLAG_INTERRUPT for all exception
> returns since at this point it doesn't know what's exactly the exception
> type. We will defer to decide if it's an exception return for system
> call when the next instruction range packet comes, it checks if there
> has one SVC instruction prior to the start address and if so we will
> change sample flags to PERF_IP_FLAG_SYSCALLRET for system call
> return.
>
> Signed-off-by: Leo Yan <leo.yan@linaro.org>
> ---
> tools/perf/util/cs-etm.c | 44 ++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 44 insertions(+)
>
> diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
> index 052805de6513..7547a7178f46 100644
> --- a/tools/perf/util/cs-etm.c
> +++ b/tools/perf/util/cs-etm.c
> @@ -1372,6 +1372,20 @@ static int cs_etm__set_sample_flags(struct cs_etm_queue *etmq)
> if (prev_packet->sample_type == CS_ETM_DISCONTINUITY)
> prev_packet->flags |= PERF_IP_FLAG_BRANCH |
> PERF_IP_FLAG_TRACE_BEGIN;
> +
> + /*
> + * If the previous packet is an exception return packet
> + * and the return address just follows SVC instuction,
> + * it needs to calibrate the previous packet sample flags
> + * as PERF_IP_FLAG_SYSCALLRET.
> + */
> + if (prev_packet->flags == (PERF_IP_FLAG_BRANCH |
> + PERF_IP_FLAG_RETURN |
> + PERF_IP_FLAG_INTERRUPT) &&
Would it make more sense to just look for prev-packet->sample_type ==
CS_ETM_EXCEPTION_RET ?
> + cs_etm__is_svc_instr(etmq, packet, packet->start_addr))
> + prev_packet->flags = PERF_IP_FLAG_BRANCH |
> + PERF_IP_FLAG_RETURN |
> + PERF_IP_FLAG_SYSCALLRET;
> break;
> case CS_ETM_DISCONTINUITY:
> /*
> @@ -1422,6 +1436,36 @@ static int cs_etm__set_sample_flags(struct cs_etm_queue *etmq)
> prev_packet->flags = packet->flags;
> break;
> case CS_ETM_EXCEPTION_RET:
> + /*
> + * When the exception return packet is inserted, since
> + * exception return packet is not used standalone for
> + * generating samples and it's affiliation to the previous
> + * instruction range packet; so set previous range packet
> + * flags to tell perf it is an exception return branch.
> + *
> + * The exception return can be for either system call or
> + * other exception types; unfortunately the packet doesn't
> + * contain exception type related info so we cannot decide
> + * the exception type purely based on exception return packet.
> + * If we record the exception number from exception packet and
> + * reuse it for excpetion return packet, this is not reliable
> + * due the trace can be discontinuity or the interrupt can
> + * be nested, thus the recorded exception number cannot be
> + * used for exception return packet for these two cases.
> + *
> + * For exception return packet, we only need to distinguish the
> + * packet is for system call or for other types. Thus the
> + * decision can be deferred when receive the next packet which
> + * contains the return address, based on the return address we
> + * can read out the previous instruction and check if it's a
> + * system call instruction and then calibrate the sample flag
> + * as needed.
> + */
> + if (prev_packet->sample_type == CS_ETM_RANGE)
> + prev_packet->flags = PERF_IP_FLAG_BRANCH |
> + PERF_IP_FLAG_RETURN |
> + PERF_IP_FLAG_INTERRUPT;
> + break;
> case CS_ETM_EMPTY:
> default:
> break;
> --
> 2.17.1
>
next prev parent reply other threads:[~2019-01-23 21:51 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-19 1:43 [PATCH v6 0/8] perf cs-etm: Add support for sample flags Leo Yan
2019-01-19 1:43 ` [PATCH v6 1/8] perf cs-etm: Add last instruction information in packet Leo Yan
2019-01-23 21:03 ` Mathieu Poirier
2019-01-19 1:43 ` [PATCH v6 2/8] perf cs-etm: Set sample flags for instruction range packet Leo Yan
2019-01-23 21:03 ` Mathieu Poirier
2019-01-19 1:43 ` [PATCH v6 3/8] perf cs-etm: Set sample flags for trace discontinuity Leo Yan
2019-01-23 21:04 ` Mathieu Poirier
2019-01-19 1:43 ` [PATCH v6 4/8] perf cs-etm: Add exception number in exception packet Leo Yan
2019-01-23 21:05 ` Mathieu Poirier
2019-01-19 1:43 ` [PATCH v6 5/8] perf cs-etm: Change tuple from traceID-CPU# to traceID-metadata Leo Yan
2019-01-23 21:13 ` Mathieu Poirier
2019-01-23 23:45 ` Leo Yan
2019-01-19 1:43 ` [PATCH v6 6/8] perf cs-etm: Add traceID in packet Leo Yan
2019-01-23 21:23 ` Mathieu Poirier
2019-01-19 1:43 ` [PATCH v6 7/8] perf cs-etm: Set sample flags for exception packet Leo Yan
2019-01-23 21:39 ` Mathieu Poirier
2019-01-19 1:43 ` [PATCH v6 8/8] perf cs-etm: Set sample flags for exception return packet Leo Yan
2019-01-23 21:51 ` Mathieu Poirier [this message]
2019-01-23 23:36 ` Leo Yan
2019-01-24 0:22 ` [PATCH v6 0/8] perf cs-etm: Add support for sample flags Mathieu Poirier
2019-01-24 4:00 ` Leo Yan
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