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Date: Mon, 16 Jan 2023 08:14:29 +0200
From: Adrian Hunter <adrian.hunter@...el.com>
To: Ravi Bangoria <ravi.bangoria@....com>, acme@...nel.org
Cc: jolsa@...nel.org, namhyung@...nel.org, irogers@...gle.com,
kan.liang@...ux.intel.com, peterz@...radead.org,
mark.rutland@....com, mingo@...hat.com,
alexander.shishkin@...ux.intel.com, james.clark@....com,
german.gomez@....com, leo.yan@...aro.org,
alexey.v.bayduraev@...ux.intel.com,
linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
sandipan.das@....com, ananth.narayan@....com,
santosh.shukla@....com
Subject: Re: [RFC 3/4] perf tool: Introduce PERF_RECORD_KMOD_SEC_MAP
On 10/01/23 07:58, Ravi Bangoria wrote:
> Introduce, perf tool only, synthetic event type PERF_RECORD_KMOD_SEC_MAP.
> Also add stub code for it. This event will be used to save/restore kernel
> module section maps to/from perf.data file. This is needed because kernel
> module elfs does not contain program header table and thus there is no
> easy way to find out how kernel would have loaded module sections in the
> memory.
Currently machine__addnew_module_map() adds a map for a
module, and then perf_event__synthesize_modules() creates
an MMAP/MMAP2 event for it. Why can't we do that for the
sections?
>
> Signed-off-by: Ravi Bangoria <ravi.bangoria@....com>
> ---
> tools/lib/perf/Documentation/libperf.txt | 1 +
> tools/lib/perf/include/perf/event.h | 25 ++++++++++++++++++++++++
> tools/perf/util/event.c | 1 +
> tools/perf/util/session.c | 12 ++++++++++++
> tools/perf/util/tool.h | 3 ++-
> 5 files changed, 41 insertions(+), 1 deletion(-)
>
> diff --git a/tools/lib/perf/Documentation/libperf.txt b/tools/lib/perf/Documentation/libperf.txt
> index a8f1a237931b..b62730b84cc5 100644
> --- a/tools/lib/perf/Documentation/libperf.txt
> +++ b/tools/lib/perf/Documentation/libperf.txt
> @@ -211,6 +211,7 @@ SYNOPSIS
> struct perf_record_time_conv;
> struct perf_record_header_feature;
> struct perf_record_compressed;
> + struct perf_record_kmod_sec_maps;
> --
>
> DESCRIPTION
> diff --git a/tools/lib/perf/include/perf/event.h b/tools/lib/perf/include/perf/event.h
> index ad47d7b31046..404b23b6902b 100644
> --- a/tools/lib/perf/include/perf/event.h
> +++ b/tools/lib/perf/include/perf/event.h
> @@ -438,6 +438,29 @@ struct perf_record_compressed {
> char data[];
> };
>
> +/* Kernel module elf section maps */
> +struct perf_record_kmod_sec_map {
> + struct perf_event_header header;
> + /* Machine id. Same as synthesized PERF_RECORD_MMAP */
> + __u32 pid;
> + /* Section start ip address */
> + __u64 start;
> + /* Section length */
> + __u64 len;
> + /* Section page offset in kernel module elf file */
> + __u64 pgoff;
> + /* Section name length, including '\0' */
> + __u16 sec_name_len;
> + /* Kernel module filename(path) length, including '\0' */
> + __u16 filename_len;
> + /*
> + * Section name and filename stored as: "sec_name\0filename\0". i.e:
> + * data[0]: Section name
> + * data[sec_name_len + 1]: File name
> + */
> + char data[];
> +};
> +
> enum perf_user_event_type { /* above any possible kernel type */
> PERF_RECORD_USER_TYPE_START = 64,
> PERF_RECORD_HEADER_ATTR = 64,
> @@ -459,6 +482,7 @@ enum perf_user_event_type { /* above any possible kernel type */
> PERF_RECORD_HEADER_FEATURE = 80,
> PERF_RECORD_COMPRESSED = 81,
> PERF_RECORD_FINISHED_INIT = 82,
> + PERF_RECORD_KMOD_SEC_MAP = 83,
> PERF_RECORD_HEADER_MAX
> };
>
> @@ -499,6 +523,7 @@ union perf_event {
> struct perf_record_time_conv time_conv;
> struct perf_record_header_feature feat;
> struct perf_record_compressed pack;
> + struct perf_record_kmod_sec_map kmod_sec_map;
> };
>
> #endif /* __LIBPERF_EVENT_H */
> diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
> index 1fa14598b916..1b03061440bc 100644
> --- a/tools/perf/util/event.c
> +++ b/tools/perf/util/event.c
> @@ -77,6 +77,7 @@ static const char *perf_event__names[] = {
> [PERF_RECORD_HEADER_FEATURE] = "FEATURE",
> [PERF_RECORD_COMPRESSED] = "COMPRESSED",
> [PERF_RECORD_FINISHED_INIT] = "FINISHED_INIT",
> + [PERF_RECORD_KMOD_SEC_MAP] = "KMOD_SEC_MAP",
> };
>
> const char *perf_event__name(unsigned int id)
> diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
> index 7c021c6cedb9..4f5165cd58de 100644
> --- a/tools/perf/util/session.c
> +++ b/tools/perf/util/session.c
> @@ -563,6 +563,8 @@ void perf_tool__fill_defaults(struct perf_tool *tool)
> tool->compressed = perf_session__process_compressed_event;
> if (tool->finished_init == NULL)
> tool->finished_init = process_event_op2_stub;
> + if (tool->kmod_sec_map == NULL)
> + tool->kmod_sec_map = process_event_stub;
> }
>
> static void swap_sample_id_all(union perf_event *event, void *data)
> @@ -997,6 +999,12 @@ static void perf_event__time_conv_swap(union perf_event *event,
> }
> }
>
> +static void perf_event_kmod_sec_map_swap(union perf_event *event __maybe_unused,
> + bool sample_id_all __maybe_unused)
> +{
> + /* FIXME */
> +}
> +
> typedef void (*perf_event__swap_op)(union perf_event *event,
> bool sample_id_all);
>
> @@ -1035,6 +1043,7 @@ static perf_event__swap_op perf_event__swap_ops[] = {
> [PERF_RECORD_STAT_ROUND] = perf_event__stat_round_swap,
> [PERF_RECORD_EVENT_UPDATE] = perf_event__event_update_swap,
> [PERF_RECORD_TIME_CONV] = perf_event__time_conv_swap,
> + [PERF_RECORD_KMOD_SEC_MAP] = perf_event_kmod_sec_map_swap,
> [PERF_RECORD_HEADER_MAX] = NULL,
> };
>
> @@ -1727,6 +1736,9 @@ static s64 perf_session__process_user_event(struct perf_session *session,
> return err;
> case PERF_RECORD_FINISHED_INIT:
> return tool->finished_init(session, event);
> + case PERF_RECORD_KMOD_SEC_MAP:
> + /* Currently PERF_RECORD_KMOD_SEC_MAP is supported only for host */
> + return tool->kmod_sec_map(tool, event, &sample, &session->machines.host);
> default:
> return -EINVAL;
> }
> diff --git a/tools/perf/util/tool.h b/tools/perf/util/tool.h
> index c957fb849ac6..8ea7fb85c196 100644
> --- a/tools/perf/util/tool.h
> +++ b/tools/perf/util/tool.h
> @@ -60,7 +60,8 @@ struct perf_tool {
> unthrottle,
> ksymbol,
> bpf,
> - text_poke;
> + text_poke,
> + kmod_sec_map;
>
> event_attr_op attr;
> event_attr_op event_update;
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