linux-kernel - Re: [PATCH 18/36] perf s390: Always build with -fPIC

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Message-Id: <20171207080951.GC4889@linux.vnet.ibm.com>
Date:   Thu, 7 Dec 2017 09:09:51 +0100
From:   Hendrik Brueckner <brueckner@...ux.vnet.ibm.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org,
        Hendrik Brueckner <brueckner@...ux.vnet.ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Thomas Richter <tmricht@...ux.vnet.ibm.com>,
        linux s390 list <linux-s390@...r.kernel.org>,
        Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [PATCH 18/36] perf s390: Always build with -fPIC

Hi Arnaldo,

On Wed, Dec 06, 2017 at 11:40:57AM -0300, Arnaldo Carvalho de Melo wrote:
> From: Hendrik Brueckner <brueckner@...ux.vnet.ibm.com>
> 
> On s390, object files must be compiled with position-indepedent code in
> order to be incrementally linked or linked to shared libraries.
> Therefore, add -fPIC to the CFLAGS for s390 to ensure each object file
> is built properly.
> 
> Reported-by: Jonathan Hermann <jonathan.hermann@...ibm.com>
> Signed-off-by: Hendrik Brueckner <brueckner@...ux.vnet.ibm.com>
> Cc: Heiko Carstens <heiko.carstens@...ibm.com>
> Cc: Martin Schwidefsky <schwidefsky@...ibm.com>
> Cc: Thomas Richter <tmricht@...ux.vnet.ibm.com>
> Cc: linux s390 list <linux-s390@...r.kernel.org>
> LPU-Reference: 1512031765-9382-1-git-send-email-brueckner@...ux.vnet.ibm.com
> Link: https://lkml.kernel.org/n/tip-a8wga8hrl0d0r84cal96fmgv@git.kernel.org
> Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> ---
>  tools/perf/Makefile.config | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
> index 2c437baf8364..bf86c09ca889 100644
> --- a/tools/perf/Makefile.config
> +++ b/tools/perf/Makefile.config
> @@ -41,6 +41,7 @@ ifeq ($(SRCARCH),x86)
>      LIBUNWIND_LIBS = -lunwind-x86 -llzma -lunwind
>    endif
>    NO_PERF_REGS := 0
> +  CFLAGS += -fPIC
>  endif

I was just rebasing my syscall table work on top of your perf/core tree.
It looks like that there is a significant difference compared to linux
master tree.

With f704ef44602fbf403e6722c7ed13f62d17e8cb20 ("s390/perf: add support for
perf_regs and libdw"), Heiko introduced a change in the Makefile.config:

	--- a/tools/perf/Makefile.config
	+++ b/tools/perf/Makefile.config
	@@ -53,6 +53,10 @@ ifeq ($(SRCARCH),arm64)
	   LIBUNWIND_LIBS = -lunwind -lunwind-aarch64
	    endif
	     
	+ifeq ($(ARCH),s390)
	+  NO_PERF_REGS := 0
	+endif
	+
	ifeq ($(NO_PERF_REGS),0)

The CFLAGS actually should applied to the s390 block and not in the x86
block.  Somehow this got messed up with git cherryp-pick / am.  So actually,
this should go into the section above:

diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index ed65e82..0833d9f 100644
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -55,6 +55,7 @@ endif
 
 ifeq ($(ARCH),s390)
   NO_PERF_REGS := 0
+  CFLAGS += -fPIC
 endif
 
 ifeq ($(NO_PERF_REGS),0)