linux-kernel - Re: [PATCH v4] perf test: Fix test trace+probe_vfs

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Date:   Mon, 17 Feb 2020 11:29:35 -0300
From:   Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Thomas Richter <tmricht@...ux.ibm.com>,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        gor@...ux.ibm.com, sumanthk@...ux.ibm.com,
        heiko.carstens@...ibm.com
Subject: Re: [PATCH v4] perf test: Fix test trace+probe_vfs_getname.sh on s390

Em Mon, Feb 17, 2020 at 09:10:10PM +0900, Masami Hiramatsu escreveu:
> On Mon, 17 Feb 2020 11:21:11 +0100
> Thomas Richter <tmricht@...ux.ibm.com> wrote:
> 
> > This test places a kprobe to function getname_flags() in the kernel
> > which has the following prototype:
> > 
> >   struct filename *
> >   getname_flags(const char __user *filename, int flags, int *empty)
> > 
> > Variable filename points to a filename located in user space memory.
> > Looking at
> > commit 88903c464321c ("tracing/probe: Add ustring type for user-space string")
> > the kprobe should indicate that user space memory is accessed.
> > 
> > Output before:
> >    [root@...lp76 perf]# ./perf test  66 67
> >    66: Use vfs_getname probe to get syscall args filenames   : FAILED!
> >    67: Check open filename arg using perf trace + vfs_getname: FAILED!
> >    [root@...lp76 perf]#
> > 
> > Output after:
> >    [root@...lp76 perf]# ./perf test  66 67
> >    66: Use vfs_getname probe to get syscall args filenames   : Ok
> >    67: Check open filename arg using perf trace + vfs_getname: Ok
> >    [root@...lp76 perf]#
> > 
> > Comments from Masami Hiramatsu:
> > This bug doesn't happen on x86 or other archs on which user-address
> > space and kernel address space is same. On some arch (ppc64 in this case?)
> > user-address space is partially or completely same as kernel address space.
> > (Yes, they switch the world when running into the kernel) In this case,
> > we need to use different data access functions for each spaces.
> > That is why I introduced "ustring" type for kprobe event.
> > As far as I can see, Thomas's patch is sane. Thomas, could you show us
> > your result on your test environment?
> > Thank you
> > 
> > Comments from Thomas Richter:
> > Test results included above.
> > 
> > Signed-off-by: Thomas Richter <tmricht@...ux.ibm.com>
> 
> Looks good to me.
> 
> Acked-by: Masami Hiramatsu <mhiramat@...nel.org>

Thanks, I tested it successfully on x86-64, applying.

- Arnaldo