linux-kernel - Re: [PATCH v8 4/8] ppc64 ftrace_with

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Message-ID: <20160211083932.GA23103@linux.vnet.ibm.com>
Date:	Thu, 11 Feb 2016 14:09:33 +0530
From:	Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>
To:	Balbir Singh <bsingharora@...il.com>
Cc:	Torsten Duwe <duwe@....de>, Michael Ellerman <mpe@...erman.id.au>,
	Jiri Kosina <jkosina@...e.cz>, Miroslav Benes <mbenes@...e.cz>,
	Petr Mladek <pmladek@...e.com>, Jessica Yu <jeyu@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	live-patching@...r.kernel.org
Subject: Re: [PATCH v8 4/8] ppc64 ftrace_with_regs configuration variables

* Balbir Singh <bsingharora@...il.com> [2016-02-11 18:48:17]:

> On Wed, 2016-02-10 at 17:25 +0100, Torsten Duwe wrote:
> 
> snip
> 
> > diff --git a/arch/powerpc/gcc-mprofile-kernel-notrace.sh b/arch/powerpc/gcc-mprofile-kernel-notrace.sh
> > new file mode 100755
> > index 0000000..68d6482
> > --- /dev/null
> > +++ b/arch/powerpc/gcc-mprofile-kernel-notrace.sh
> > @@ -0,0 +1,33 @@
> > +#!/bin/sh
> > +# Test whether the compile option -mprofile-kernel
> > +# generates profiling code ( = a call to mcount), and
> > +# whether a function without any global references sets
> > +# the TOC pointer properly at the beginning, and
> > +# whether the "notrace" function attribute successfully
> > +# suppresses the _mcount call.
> > +
> > +echo "int func() { return 0; }" | \
> > +    $* -S -x c -O2 -p -mprofile-kernel - -o - 2> /dev/null | \
> > +    grep -q "mcount"
> > +
> > +trace_result=$?
> > +
> > +echo "int func() { return 0; }" | \
> > +    $* -S -x c -O2 -p -mprofile-kernel - -o - 2> /dev/null | \
> > +    sed -n -e '/func:/,/bl _mcount/p' | grep -q TOC
> > +
> > +leaf_toc_result=$?
> > +
> 
> leaf_toc_result failed for me with gcc 5. I'll try and grab gcc-6
> and give the patches a spin
> 

It fails for me to on ppc64le but pass over ppc64

# gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/ppc64-redhat-linux/5.1.1/lto-wrapper
Target: ppc64-redhat-linux
[...]
gcc version 5.1.1 20150422 (Red Hat 5.1.1-1) (GCC)

# echo "int func() { return 0;  }" |     gcc -S -x c -O2 -p -mprofile-kernel - -o - 2> /dev/null |     sed -n -e '/func:/,/bl _mcount/p'
func:
        .quad   .L.func,.TOC.@...base
        .previous
        .type   func, @function
.L.func:
        mflr 0
        std 0,16(1)
        bl _mcount

# gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/powerpc64le-linux-gnu/5/lto-wrapper
Target: powerpc64le-linux-gnu
[...]
gcc version 5.3.1 20160205 (Ubuntu/IBM 5.3.1-8ubuntu2)

# echo "int func() { return 0;  }" |     gcc -S -x c -O2 -p -mprofile-kernel - -o - 2> /dev/null |     sed -n -e '/func:/,/bl _mcount/p'
func:
        mflr 0
        std 0,16(1)
        bl _mcount


I will try it over gcc-6.

Thanks,
Kamalesh