linux-kernel - Re: [PATCH 2/3] perf scripts python: arm-cs-trace-disasm.py: set start vm addr of exectable file to 0

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Date: Wed, 20 Dec 2023 12:06:59 +0000
From: James Clark <james.clark@....com>
To: Ruidong Tian <tianruidong@...ux.alibaba.com>, linux-kernel@...r.kernel.org
Cc: coresight@...ts.linaro.org, suzuki.poulose@....com,
 mike.leach@...aro.org, alexander.shishkin@...ux.intel.com,
 linux-arm-kernel@...ts.infradead.org, adrian.hunter@...el.com,
 linux-perf-users@...r.kernel.org, leo.yan@...aro.org, al.grant@....com,
 mathieu.poirier@...aro.org, tor@...com, acme@...hat.com
Subject: Re: [PATCH 2/3] perf scripts python: arm-cs-trace-disasm.py: set
 start vm addr of exectable file to 0



On 14/12/2023 12:33, Ruidong Tian wrote:
> For exectable ELF file, which e_type is ET_EXEC, dso start address is a
> absolute address other than offset. Just set vm_start to zero when dso
> start is 0x400000, which means it is a exectable file.
> 
> Signed-off-by: Ruidong Tian <tianruidong@...ux.alibaba.com>
> ---
>  tools/perf/scripts/python/arm-cs-trace-disasm.py | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/perf/scripts/python/arm-cs-trace-disasm.py b/tools/perf/scripts/python/arm-cs-trace-disasm.py
> index 46bf6b02eea1..c9e14af5b58c 100755
> --- a/tools/perf/scripts/python/arm-cs-trace-disasm.py
> +++ b/tools/perf/scripts/python/arm-cs-trace-disasm.py
> @@ -260,8 +260,9 @@ def process_event(param_dict):
>  
>  	if (options.objdump_name != None):
>  		# It doesn't need to decrease virtual memory offset for disassembly
> -		# for kernel dso, so in this case we set vm_start to zero.
> -		if (dso == "[kernel.kallsyms]"):
> +		# for kernel dso and executable file dso, so in this case we set
> +		# vm_start to zero.
> +		if (dso == "[kernel.kallsyms]" or dso_start == 0x400000):
>  			dso_vm_start = 0
>  		else:
>  			dso_vm_start = int(dso_start)

I confirmed that this fixes the disassembly for static binaries. It
would have been nice to check the type of the file rather than using a
magic number, but it's not that easy and I don't really see a chance of
the number having a false positive.

I wonder if it's worth putting a fixes tag on this one? For the other
ones I'd say no tag as they have a chance of breaking things.

Reviewed-by: James Clark <james.clark@....com>