diff mbox

Test for profiling support (_mcount/gprof)

Message ID CAMe9rOpye5pUs1j_V_ANOJQfrzK5VXhacLhHFzB95OD+3dtSPw@mail.gmail.com
State New, archived
Headers show

Commit Message

H.J. Lu Aug. 16, 2017, 9:19 p.m. UTC
On Wed, Aug 16, 2017 at 2:10 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Wed, Aug 16, 2017 at 2:04 PM, Florian Weimer <fweimer@redhat.com> wrote:
>> On 08/16/2017 10:03 PM, H.J. Lu wrote:
>>> On Wed, Aug 16, 2017 at 8:32 AM, Florian Weimer <fweimer@redhat.com> wrote:
>>>> On 08/16/2017 05:30 PM, Andreas Schwab wrote:
>>>>> On Aug 16 2017, Florian Weimer <fweimer@redhat.com> wrote:
>>>>>
>>>>>> On 08/16/2017 05:20 PM, Andreas Schwab wrote:
>>>>>>> On Aug 16 2017, Florian Weimer <fweimer@redhat.com> wrote:
>>>>>>>
>>>>>>>> If you don't use --enable-frame-pointer for GCC, there's no apparent
>>>>>>>> reason to me to build glibc with --fomit-frame-pointer because it's the
>>>>>>>> default (albeit in a fashion that is compatible with -pg).
>>>>>>>
>>>>>>> That is not true.
>>>>>>
>>>>>> It is currently true—I don't see why anyone would want to build glibc
>>>>>> this way.  Could you enlighten me?
>>>>>
>>>>> To omit the frame pointer.
>>>>
>>>> But GCC does it by default if you don't build with
>>>> --enable-frame-pointer, at least on i386, which is the architecture for
>>>> which you reported the failure.
>>>
>>> gmon/tst-gmon-gprof also fails with GCC defaulting to PIE.
>>
>> That would be a real failure (due to ASLR).  Does linking with -pg
>> ordinarily disable PIE?  I suppose we could add -pg to LDFLAGS for this
>> test because as Andreas explained earlier, it won't link in the system
>> profiling libraries.
>>
>
> -pg and -pie are mutually exclusive since they need different crt1.os,
> gcrrt1.o vs Scrt1.o.   This patch works for me:
>
> diff --git a/Makeconfig b/Makeconfig
> index 5f2469116c..b51904b797 100644
> --- a/Makeconfig
> +++ b/Makeconfig
> @@ -409,7 +409,7 @@ ifndef +link-pie
>  +link-pie-before-libc = $(CC) -pie -Wl,-O1 -nostdlib -nostartfiles -o $@ \
>         $(sysdep-LDFLAGS) $(LDFLAGS) $(LDFLAGS-$(@F)) \
>         $(combreloc-LDFLAGS) $(relro-LDFLAGS) $(hashstyle-LDFLAGS) \
> -       $(addprefix $(csu-objpfx),S$(start-installed-name)) \
> +       $(firstword $(CRT-$(@F)) $(csu-objpfx)S$(start-installed-name)) \
>         $(+preinit) $(+prectorS) \
>         $(filter-out $(addprefix $(csu-objpfx),start.o \
>                       S$(start-installed-name))\
>
>

Tested  with GCC defaulting to PIE.  OK for master?

Comments

Florian Weimer Aug. 17, 2017, 7:44 a.m. UTC | #1
On 08/16/2017 11:19 PM, H.J. Lu wrote:
> -pg and -pie are mutually exclusive since they need different crt1.o,
> gcrrt1.o vs Scrt1.o.  Make -pg overrdies -pie.
> 
> 	* Makeconfig (+link-pie-before-libc): Add CRT-* hook to override
> 	the startup object.

Typo (gcrrt1.o), and the commit message is confusing.  There is no -pg
involved at the linking stage.

gcrt1.o is deliberately compiled so that it is compatible with PIE, so
the patch itself is okay.

Thanks,
Florian
diff mbox

Patch

From f19721b98346b9493f3ecb5cd41527e102c7fedf Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Wed, 16 Aug 2017 14:15:43 -0700
Subject: [PATCH] Support -pg with GCC defaulting to PIE

-pg and -pie are mutually exclusive since they need different crt1.o,
gcrrt1.o vs Scrt1.o.  Make -pg overrdies -pie.

	* Makeconfig (+link-pie-before-libc): Add CRT-* hook to override
	the startup object.
---
 Makeconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Makeconfig b/Makeconfig
index 5f2469116c..b51904b797 100644
--- a/Makeconfig
+++ b/Makeconfig
@@ -409,7 +409,7 @@  ifndef +link-pie
 +link-pie-before-libc = $(CC) -pie -Wl,-O1 -nostdlib -nostartfiles -o $@ \
 	     $(sysdep-LDFLAGS) $(LDFLAGS) $(LDFLAGS-$(@F)) \
 	     $(combreloc-LDFLAGS) $(relro-LDFLAGS) $(hashstyle-LDFLAGS) \
-	     $(addprefix $(csu-objpfx),S$(start-installed-name)) \
+	     $(firstword $(CRT-$(@F)) $(csu-objpfx)S$(start-installed-name)) \
 	     $(+preinit) $(+prectorS) \
 	     $(filter-out $(addprefix $(csu-objpfx),start.o \
 						    S$(start-installed-name))\
-- 
2.13.5