linux-kernel - Re: [PATCH] perf scripts python arm-cs-trace-disasm.py: Skip disasm if address continuity is broken

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Message-ID: <7302367c-311f-4655-9a83-3c4034c50086@linaro.org>
Date: Fri, 19 Jul 2024 15:39:55 +0100
From: James Clark <james.clark@...aro.org>
To: Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>,
 james.clark@....com, mike.leach@...aro.org, suzuki.poulose@....com,
 Leo Yan <leo.yan@....com>
Cc: acme@...hat.com, coresight@...ts.linaro.org,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 darren@...amperecomputing.com, scclevenger@...amperecomputing.com
Subject: Re: [PATCH] perf scripts python arm-cs-trace-disasm.py: Skip disasm
 if address continuity is broken



On 19/07/2024 10:26 am, Ganapatrao Kulkarni wrote:
> To generate the instruction tracing, script uses 2 contiguous packets
> address range. If there a continuity brake due to discontiguous branch
> address, it is required to reset the tracing and start tracing with the
> new set of contiguous packets.
> 
> Adding change to identify the break and complete the remaining tracing
> of current packets and restart tracing from new set of packets, if
> continuity is established.
> 

Hi Ganapatrao,

Can you add a before and after example of what's changed to the commit 
message? It wasn't immediately obvious to me if this is adding missing 
output, or it was correcting the tail end of the output that was 
previously wrong.

> Signed-off-by: Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>
> ---
>   tools/perf/scripts/python/arm-cs-trace-disasm.py | 10 ++++++++++
>   1 file changed, 10 insertions(+)
> 
> diff --git a/tools/perf/scripts/python/arm-cs-trace-disasm.py b/tools/perf/scripts/python/arm-cs-trace-disasm.py
> index d973c2baed1c..ad10cee2c35e 100755
> --- a/tools/perf/scripts/python/arm-cs-trace-disasm.py
> +++ b/tools/perf/scripts/python/arm-cs-trace-disasm.py
> @@ -198,6 +198,10 @@ def process_event(param_dict):
>   		cpu_data[str(cpu) + 'addr'] = addr
>   		return
>   
> +	if (cpu_data.get(str(cpu) + 'ip') == None):
> +		cpu_data[str(cpu) + 'ip'] = ip
> +

Do you need to write into the global cpu_data here? Doesn't it get 
overwritten after you load it back into 'prev_ip'

   prev_ip = cpu_data[str(cpu) + 'ip']

   ... then ...

   # Record for previous sample packet
   cpu_data[str(cpu) + 'addr'] = addr
   cpu_data[str(cpu) + 'ip'] = stop_addr

Would a local variable not accomplish the same thing?

> +	prev_ip = cpu_data[str(cpu) + 'ip']
>   
>   	if (options.verbose == True):
>   		print("Event type: %s" % name)
> @@ -243,12 +247,18 @@ def process_event(param_dict):
>   
>   	# Record for previous sample packet
>   	cpu_data[str(cpu) + 'addr'] = addr
> +	cpu_data[str(cpu) + 'ip'] = stop_addr
>   
>   	# Handle CS_ETM_TRACE_ON packet if start_addr=0 and stop_addr=4
>   	if (start_addr == 0 and stop_addr == 4):
>   		print("CPU%d: CS_ETM_TRACE_ON packet is inserted" % cpu)
>   		return
>   
> +	if (stop_addr < start_addr):
> +		# Continuity of the Packets broken, set start_addr to previous
> +		# packet ip to complete the remaining tracing of the address range.
> +		start_addr = prev_ip
> +
>   	if (start_addr < int(dso_start) or start_addr > int(dso_end)):
>   		print("Start address 0x%x is out of range [ 0x%x .. 0x%x ] for dso %s" % (start_addr, int(dso_start), int(dso_end), dso))
>   		return