linux-kernel - Re: [PATCH Linux-next] perf test: Fix test case perf trace BTF general tests

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Message-ID: <20251118132451.29a35127@gandalf.local.home>
Date: Tue, 18 Nov 2025 13:24:51 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Thomas Richter <tmricht@...ux.ibm.com>, linux-kernel@...r.kernel.org,
 linux-s390@...r.kernel.org, linux-perf-users@...r.kernel.org,
 acme@...nel.org, agordeev@...ux.ibm.com, gor@...ux.ibm.com,
 sumanthk@...ux.ibm.com, hca@...ux.ibm.com, japo@...ux.ibm.com
Subject: Re: [PATCH Linux-next] perf test: Fix test case perf trace BTF
 general tests

On Mon, 17 Nov 2025 22:43:21 -0800
Namhyung Kim <namhyung@...nel.org> wrote:

> > bash-5.3# uname -a
> > Linux f43 6.18.0-rc5-next-20251114tmr-n #1 SMP PREEMPT_DYNAMIC Mon Nov 17 11:24:02 CET 2025 x86_64 GNU/Linux
> > bash-5.3# cat /sys/kernel/tracing/events/syscalls/sys_enter_write/format
> > name: sys_enter_write
> > ID: 758
> > format:
> > 	field:unsigned short common_type;	offset:0;	size:2;	signed:0;
> > 	field:unsigned char common_flags;	offset:2;	size:1;	signed:0;
> > 	field:unsigned char common_preempt_count;	offset:3;	size:1;	signed:0;
> > 	field:int common_pid;	offset:4;	size:4;	signed:1;
> > 
> > 	field:int __syscall_nr;	offset:8;	size:4;	signed:1;
> > 	field:unsigned int fd;	offset:16;	size:8;	signed:0;
> > 	field:const char * buf;	offset:24;	size:8;	signed:0;
> > 	field:size_t count;	offset:32;	size:8;	signed:0;
> > 	field:__data_loc char[] __buf_val;	offset:40;	size:4;	signed:0;  
> 
> Indeed, I see this new field __buf_val.
> 
> Steve, is this what you added recently for taking user contents?

Yes.

> Hmm.. this makes perf trace confused wrt the syscall parameters.
> Is it always __buf_val or has any patterns?

Really? It still uses libtraceevent right? I made sure that this didn't
break trace-cmd and thought that perf would work too.

-- Steve