[PATCH v1 1/2] perf cs-etm: Always allocate memory for cs_etm_queue::prev_packet

[PATCH v1 1/2] perf cs-etm: Always allocate memory for cs_etm_queue::prev_packet

[Leo Yan]

Robert Walker reported a segmentation fault is observed when process
CoreSight trace data; this issue can be easily reproduced by the
command 'perf report --itrace=i1000i' for decoding tracing data.

If neither the 'b' flag (synthesize branches events) nor 'l' flag
(synthesize last branch entries) are specified to option '--itrace',
cs_etm_queue::prev_packet will not been initialised.  After merging
the code to support exception packets and sample flags, there
introduced a number of uses of cs_etm_queue::prev_packet without
checking whether it is valid, for these cases any accessing to
uninitialised prev_packet will cause crash.

As cs_etm_queue::prev_packet is used more widely now and it's already
hard to follow which functions have been called in a context where the
validity of cs_etm_queue::prev_packet has been checked, this patch
always allocates memory for cs_etm_queue::prev_packet.

Reported-by: Robert Walker <robert.walker@arm.com>
Suggested-by: Robert Walker <robert.walker@arm.com>
Fixes: 7100b12cf474 ("perf cs-etm: Generate branch sample for exception packet")
Fixes: 24fff5eb2b93 ("perf cs-etm: Avoid stale branch samples when flush packet")
Signed-off-by: Leo Yan <leo.yan@linaro.org>
---
 tools/perf/util/cs-etm.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
index 110804936fc3..054b480aab04 100644
--- a/tools/perf/util/cs-etm.c
+++ b/tools/perf/util/cs-etm.c
@@ -422,11 +422,9 @@ static struct cs_etm_queue *cs_etm__alloc_queue(struct cs_etm_auxtrace *etm)
 	if (!etmq->packet)
 		goto out_free;
 
-	if (etm->synth_opts.last_branch || etm->sample_branches) {
-		etmq->prev_packet = zalloc(szp);
-		if (!etmq->prev_packet)
-			goto out_free;
-	}
+	etmq->prev_packet = zalloc(szp);
+	if (!etmq->prev_packet)
+		goto out_free;
 
 	if (etm->synth_opts.last_branch) {
 		size_t sz = sizeof(struct branch_stack);
-- 
2.17.1


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[PATCH v1 2/2] perf cs-etm: Don't check cs_etm_queue::prev_packet validity

[Leo Yan]

Since cs_etm_queue::prev_packet is allocated for all cases, it will
never be NULL pointer; now validity checking prev_packet is pointless,
remove all of them.

Signed-off-by: Leo Yan <leo.yan@linaro.org>
---
 tools/perf/util/cs-etm.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
index 054b480aab04..de488b43f440 100644
--- a/tools/perf/util/cs-etm.c
+++ b/tools/perf/util/cs-etm.c
@@ -979,7 +979,6 @@ static int cs_etm__sample(struct cs_etm_queue *etmq)
 	 * PREV_PACKET is a branch.
 	 */
 	if (etm->synth_opts.last_branch &&
-	    etmq->prev_packet &&
 	    etmq->prev_packet->sample_type == CS_ETM_RANGE &&
 	    etmq->prev_packet->last_instr_taken_branch)
 		cs_etm__update_last_branch_rb(etmq);
@@ -1012,7 +1011,7 @@ static int cs_etm__sample(struct cs_etm_queue *etmq)
 		etmq->period_instructions = instrs_over;
 	}
 
-	if (etm->sample_branches && etmq->prev_packet) {
+	if (etm->sample_branches) {
 		bool generate_sample = false;
 
 		/* Generate sample for tracing on packet */
@@ -1069,9 +1068,6 @@ static int cs_etm__flush(struct cs_etm_queue *etmq)
 	struct cs_etm_auxtrace *etm = etmq->etm;
 	struct cs_etm_packet *tmp;
 
-	if (!etmq->prev_packet)
-		return 0;
-
 	/* Handle start tracing packet */
 	if (etmq->prev_packet->sample_type == CS_ETM_EMPTY)
 		goto swap_packet;
-- 
2.17.1


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Re: [PATCH v1 1/2] perf cs-etm: Always allocate memory for cs_etm_queue::prev_packet

[Robert Walker]

Hi,

On 28/04/2019 09:32, Leo Yan wrote:
> Robert Walker reported a segmentation fault is observed when process
> CoreSight trace data; this issue can be easily reproduced by the
> command 'perf report --itrace=i1000i' for decoding tracing data.
>
> If neither the 'b' flag (synthesize branches events) nor 'l' flag
> (synthesize last branch entries) are specified to option '--itrace',
> cs_etm_queue::prev_packet will not been initialised.  After merging
> the code to support exception packets and sample flags, there
> introduced a number of uses of cs_etm_queue::prev_packet without
> checking whether it is valid, for these cases any accessing to
> uninitialised prev_packet will cause crash.
>
> As cs_etm_queue::prev_packet is used more widely now and it's already
> hard to follow which functions have been called in a context where the
> validity of cs_etm_queue::prev_packet has been checked, this patch
> always allocates memory for cs_etm_queue::prev_packet.
>
> Reported-by: Robert Walker <robert.walker@arm.com>
> Suggested-by: Robert Walker <robert.walker@arm.com>
> Fixes: 7100b12cf474 ("perf cs-etm: Generate branch sample for exception packet")
> Fixes: 24fff5eb2b93 ("perf cs-etm: Avoid stale branch samples when flush packet")
> Signed-off-by: Leo Yan <leo.yan@linaro.org>
> ---
>   tools/perf/util/cs-etm.c | 8 +++-----
>   1 file changed, 3 insertions(+), 5 deletions(-)

I've tested these with the trace from the HiKey960 and the segfault no 
longer occurs

Tested-by: Robert Walker <robert.walker@arm.com>

Regards

Rob

>
> diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
> index 110804936fc3..054b480aab04 100644
> --- a/tools/perf/util/cs-etm.c
> +++ b/tools/perf/util/cs-etm.c
> @@ -422,11 +422,9 @@ static struct cs_etm_queue *cs_etm__alloc_queue(struct cs_etm_auxtrace *etm)
>   	if (!etmq->packet)
>   		goto out_free;
>   
> -	if (etm->synth_opts.last_branch || etm->sample_branches) {
> -		etmq->prev_packet = zalloc(szp);
> -		if (!etmq->prev_packet)
> -			goto out_free;
> -	}
> +	etmq->prev_packet = zalloc(szp);
> +	if (!etmq->prev_packet)
> +		goto out_free;
>   
>   	if (etm->synth_opts.last_branch) {
>   		size_t sz = sizeof(struct branch_stack);

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Re: [PATCH v1 2/2] perf cs-etm: Don't check cs_etm_queue::prev_packet validity

[Robert Walker]

On 28/04/2019 09:32, Leo Yan wrote:
> Since cs_etm_queue::prev_packet is allocated for all cases, it will
> never be NULL pointer; now validity checking prev_packet is pointless,
> remove all of them.
>
> Signed-off-by: Leo Yan <leo.yan@linaro.org>
> ---
>   tools/perf/util/cs-etm.c | 6 +-----
>   1 file changed, 1 insertion(+), 5 deletions(-)

Tested-by: Robert Walker <robert.walker@arm.com>

Regards

Rob

> diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
> index 054b480aab04..de488b43f440 100644
> --- a/tools/perf/util/cs-etm.c
> +++ b/tools/perf/util/cs-etm.c
> @@ -979,7 +979,6 @@ static int cs_etm__sample(struct cs_etm_queue *etmq)
>   	 * PREV_PACKET is a branch.
>   	 */
>   	if (etm->synth_opts.last_branch &&
> -	    etmq->prev_packet &&
>   	    etmq->prev_packet->sample_type == CS_ETM_RANGE &&
>   	    etmq->prev_packet->last_instr_taken_branch)
>   		cs_etm__update_last_branch_rb(etmq);
> @@ -1012,7 +1011,7 @@ static int cs_etm__sample(struct cs_etm_queue *etmq)
>   		etmq->period_instructions = instrs_over;
>   	}
>   
> -	if (etm->sample_branches && etmq->prev_packet) {
> +	if (etm->sample_branches) {
>   		bool generate_sample = false;
>   
>   		/* Generate sample for tracing on packet */
> @@ -1069,9 +1068,6 @@ static int cs_etm__flush(struct cs_etm_queue *etmq)
>   	struct cs_etm_auxtrace *etm = etmq->etm;
>   	struct cs_etm_packet *tmp;
>   
> -	if (!etmq->prev_packet)
> -		return 0;
> -
>   	/* Handle start tracing packet */
>   	if (etmq->prev_packet->sample_type == CS_ETM_EMPTY)
>   		goto swap_packet;

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Re: [PATCH v1 1/2] perf cs-etm: Always allocate memory for cs_etm_queue::prev_packet

[Arnaldo Carvalho de Melo]

Em Sun, Apr 28, 2019 at 04:32:27PM +0800, Leo Yan escreveu:
> Robert Walker reported a segmentation fault is observed when process
> CoreSight trace data; this issue can be easily reproduced by the
> command 'perf report --itrace=i1000i' for decoding tracing data.
> 
> If neither the 'b' flag (synthesize branches events) nor 'l' flag
> (synthesize last branch entries) are specified to option '--itrace',
> cs_etm_queue::prev_packet will not been initialised.  After merging
> the code to support exception packets and sample flags, there
> introduced a number of uses of cs_etm_queue::prev_packet without
> checking whether it is valid, for these cases any accessing to
> uninitialised prev_packet will cause crash.
> 
> As cs_etm_queue::prev_packet is used more widely now and it's already
> hard to follow which functions have been called in a context where the
> validity of cs_etm_queue::prev_packet has been checked, this patch
> always allocates memory for cs_etm_queue::prev_packet.
> 
> Reported-by: Robert Walker <robert.walker@arm.com>
> Suggested-by: Robert Walker <robert.walker@arm.com>
> Fixes: 7100b12cf474 ("perf cs-etm: Generate branch sample for exception packet")

Thanks, applied both to perf/urgent, testing them now in the containers.

- Arnaldo

> Fixes: 24fff5eb2b93 ("perf cs-etm: Avoid stale branch samples when flush packet")
> Signed-off-by: Leo Yan <leo.yan@linaro.org>
> ---
>  tools/perf/util/cs-etm.c | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
> index 110804936fc3..054b480aab04 100644
> --- a/tools/perf/util/cs-etm.c
> +++ b/tools/perf/util/cs-etm.c
> @@ -422,11 +422,9 @@ static struct cs_etm_queue *cs_etm__alloc_queue(struct cs_etm_auxtrace *etm)
>  	if (!etmq->packet)
>  		goto out_free;
>  
> -	if (etm->synth_opts.last_branch || etm->sample_branches) {
> -		etmq->prev_packet = zalloc(szp);
> -		if (!etmq->prev_packet)
> -			goto out_free;
> -	}
> +	etmq->prev_packet = zalloc(szp);
> +	if (!etmq->prev_packet)
> +		goto out_free;
>  
>  	if (etm->synth_opts.last_branch) {
>  		size_t sz = sizeof(struct branch_stack);
> -- 
> 2.17.1

-- 

- Arnaldo

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