[lttng-dev] [RFC PATCH lttng-tools 10/18] Add serialized versions of lttng_event_context structs

[Mathieu Desnoyers]

----- On Apr 18, 2019, at 12:18 PM, Yannick Lamarre ylamarre at efficios.com wrote:

> Serialized versions of lttng_event_context and lttng_event_perf_counter_ctx are
> packed structures to be used in communication protocols for consistent
> sizes across platforms. The serialized versions are stripped of pointers
> and padding.
> 
> Pointers are removed since their size can vary on platforms supporting
> variable sized registers (x86-64).

Same question as prior commit about the explanation here.

> Padding is also removed since it defeats the purpose of a packed struct.

Same question as prior commit about padding purpose. How do we intend to
extend this in the future ? We should document this plan.

Thanks,

Mathieu

> 
> Signed-off-by: Yannick Lamarre <ylamarre at efficios.com>
> ---
> include/lttng/event-internal.h | 11 +++++++++++
> 1 file changed, 11 insertions(+)
> 
> diff --git a/include/lttng/event-internal.h b/include/lttng/event-internal.h
> index f8130e3b..25a88448 100644
> --- a/include/lttng/event-internal.h
> +++ b/include/lttng/event-internal.h
> @@ -27,6 +27,17 @@
> 
> struct lttng_userspace_probe_location;
> 
> +struct lttng_event_perf_counter_ctx_serialized {
> +	uint32_t type;
> +	uint64_t config;
> +	char name[LTTNG_SYMBOL_NAME_LEN];
> +} LTTNG_PACKED;
> +
> +struct lttng_event_context_serialized {
> +	uint32_t ctx; /* enum lttng_event_context_type */
> +	struct lttng_event_perf_counter_ctx_serialized perf_counter;
> +} LTTNG_PACKED;
> +
> struct lttng_event_extended {
> 	/*
> 	 * exclusions and filter_expression are only set when the lttng_event
> --
> 2.11.0
> 
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-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com