[lttng-dev] [PATCH lttng-ust] Fix: Filter ABI changes to support FILTER_BYTECODE_MAX_LEN (65536)

[Mathieu Desnoyers]

* Christian Babeux (christian.babeux at efficios.com) wrote:
> In order to support the filter bytecode maximum length (65536 bytes),
> the lttng_ust_filter_bytecode len field type must be able to
> hold more than a uint16_t. Change the field type to a uint32_t.
> 
> Also, since the relocation table is located at the end of the actual
> bytecode, the reloc_offset field must support offset values larger
> than 65535. Change the field type to a uint32_t. This change will
> allow support of relocation table appended to larger bytecode without
> breaking the ABI if the need arise in the future.
> 
> Both changes currently breaks the filter ABI, but this should be a
> reasonable compromise since the filtering feature has not been
> released yet.
> 
> Signed-off-by: Christian Babeux <christian.babeux at efficios.com>
> ---
>  include/lttng/ust-abi.h | 4 ++--
>  include/ust-comm.h      | 4 ++--
>  2 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/include/lttng/ust-abi.h b/include/lttng/ust-abi.h
> index 0489e89..91639a7 100644
> --- a/include/lttng/ust-abi.h
> +++ b/include/lttng/ust-abi.h
> @@ -174,8 +174,8 @@ struct lttng_ust_calibrate {
>  
>  #define FILTER_BYTECODE_MAX_LEN		65536
>  struct lttng_ust_filter_bytecode {
> -	uint16_t len;
> -	uint16_t reloc_offset;
> +	uint32_t len;
> +	uint32_t reloc_offset;

You'll need to add a check in liblttng-ust/lttng-ust-comm.c, when the
data is received: we need to check that the reloc_offset is within the
data.

Mathieu

>  	char data[0];
>  };
>  
> diff --git a/include/ust-comm.h b/include/ust-comm.h
> index b09fcca..4a3e4ce 100644
> --- a/include/ust-comm.h
> +++ b/include/ust-comm.h
> @@ -132,8 +132,8 @@ struct ustcomm_ust_msg {
>  		struct lttng_ust_tracer_version version;
>  		struct lttng_ust_tracepoint_iter tracepoint;
>  		struct {
> -			uint16_t data_size;	/* following filter data */
> -			uint16_t reloc_offset;
> +			uint32_t data_size;	/* following filter data */
> +			uint32_t reloc_offset;
>  		} filter;
>  	} u;
>  };
> -- 
> 1.7.11.4
> 

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com