linux-kernel - Re: [PATCH v2] perf/probe: Change MAX

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Date:   Tue, 21 Mar 2017 10:37:54 -0300
From:   Arnaldo Carvalho de Melo <acme@...hat.com>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>,
        linux-kernel@...r.kernel.org, alexis.berlemont@...il.com,
        peterz@...radead.org, mingo@...hat.com,
        alexander.shishkin@...ux.intel.com, mpe@...erman.id.au,
        naveen.n.rao@...ux.vnet.ibm.com, maddy@...ux.vnet.ibm.com
Subject: Re: [PATCH v2] perf/probe: Change MAX_CMDLEN

Em Tue, Mar 21, 2017 at 02:19:50PM +0900, Masami Hiramatsu escreveu:
> On Tue,  7 Feb 2017 11:15:47 +0530
> Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com> wrote:
> 
> > There are many SDT markers in powerpc whose uprobe definition goes
> > beyond current MAX_CMDLEN, especially when target filename is long
> > and sdt marker has long list of arguments. For example, definition
> > of sdt marker
> > 
> >   method__compile__end: 8@17 8@9 8@10 -4@8 8@7 -4@6 8@5 -4@4 1@37(28)
> > 
> > from file
> > 
> >   /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.91-2.b14.fc22.ppc64/jre/lib/\
> >      ppc64/server/libjvm.so
> > 
> > is
> > 
> >   p:sdt_hotspot/method__compile__end /usr/lib/jvm/java-1.8.0-openjdk-\
> >     1.8.0.91-2.b14.fc22.ppc64/jre/lib/ppc64/server/libjvm.so:0x4c4e00\
> >     arg1=%gpr17:u64 arg2=%gpr9:u64 arg3=%gpr10:u64 arg4=%gpr8:s32\
> >     arg5=%gpr7:u64 arg6=%gpr6:s32 arg7=%gpr5:u64 arg8=%gpr4:s32\
> >     arg9=+37(%gpr28):u8
> > 
> > Perf probe fails with seg fault for such markers. As uprobe_events file
> > accepts definition upto 4094 characters(4096 - 2 (\n\0)), increase value
> > of MAX_CMDLEN to 4094.
> 
> This looks good to me.
> 
> Acked-by: Masami Hiramatsu <mhiramat@...nel.org>

Thanks, applied manually, as the code patched drifted some lines away
from the ones here.

- Arnaldo
 
> Thanks,
> 
> > 
> > Signed-off-by: Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
> > ---
> > Changes in v2:
> >   - Set MAX_CMDLEN to 4094 instead of 512
> > 
> >  tools/perf/util/probe-event.c | 1 -
> >  tools/perf/util/probe-file.c  | 3 ++-
> >  2 files changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> > index 6a6f44d..e6e3244 100644
> > --- a/tools/perf/util/probe-event.c
> > +++ b/tools/perf/util/probe-event.c
> > @@ -47,7 +47,6 @@
> >  #include "probe-file.h"
> >  #include "session.h"
> >  
> > -#define MAX_CMDLEN 256
> >  #define PERFPROBE_GROUP "probe"
> >  
> >  bool probe_event_dry_run;	/* Dry run flag */
> > diff --git a/tools/perf/util/probe-file.c b/tools/perf/util/probe-file.c
> > index 38eca3c..fdabe7e 100644
> > --- a/tools/perf/util/probe-file.c
> > +++ b/tools/perf/util/probe-file.c
> > @@ -29,7 +29,8 @@
> >  #include "session.h"
> >  #include "perf_regs.h"
> >  
> > -#define MAX_CMDLEN 256
> > +/* 4096 - 2 ('\n' + '\0') */
> > +#define MAX_CMDLEN 4094
> >  
> >  static void print_open_warning(int err, bool uprobe)
> >  {
> > -- 
> > 2.9.3
> > 
> 
> 
> -- 
> Masami Hiramatsu <mhiramat@...nel.org>