linux-next: build failure after merge of the tip tree

linux-next: build failure after merge of the tip tree

[Stephen Rothwell]

Hi all,

After merging the tip tree, today's linux-next build (x86_64 allmodconfig)
failed like this:

  DESCEND  objtool
  CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/builtin-check.o
  CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/special.o
  CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/elf.o
  CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/objtool.o
  MKDIR    /home/sfr/next/x86_64_allmodconfig/tools/objtool/arch/x86/insn/
  CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/libstring.o
elf.c:22:23: fatal error: sys/types.h: No such file or directory
compilation terminated.
  CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/exec-cmd.o
  CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/help.o
builtin-check.c:28:20: fatal error: string.h: No such file or directory
compilation terminated.
objtool.c:28:19: fatal error: stdio.h: No such file or directory
compilation terminated.

and further errors ...

This build is done with a PowerPC hosted cross compiler with no glibc.
I assume that some things here need to be built with HOSTCC?

Presumably caused by commit

  9e54249679b4 ("Merge branch 'core/objtool'")

and the commit series that was merged.

I tried to revert that merge, but it had conflicts, so I just used the
tip tree from next-20160229 for today.

-- 
Cheers,
Stephen Rothwell

Re: linux-next: build failure after merge of the tip tree

[Ingo Molnar]

* Stephen Rothwell <sfr@canb.auug.org.au> wrote:

> Hi all,
> 
> After merging the tip tree, today's linux-next build (x86_64 allmodconfig)
> failed like this:
> 
>   DESCEND  objtool
>   CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/builtin-check.o
>   CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/special.o
>   CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/elf.o
>   CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/objtool.o
>   MKDIR    /home/sfr/next/x86_64_allmodconfig/tools/objtool/arch/x86/insn/
>   CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/libstring.o
> elf.c:22:23: fatal error: sys/types.h: No such file or directory
> compilation terminated.
>   CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/exec-cmd.o
>   CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/help.o
> builtin-check.c:28:20: fatal error: string.h: No such file or directory
> compilation terminated.
> objtool.c:28:19: fatal error: stdio.h: No such file or directory
> compilation terminated.
> 
> and further errors ...
> 
> This build is done with a PowerPC hosted cross compiler with no glibc.

Ugh, what a rare and weird way to build an x86 kernel, and you made linux-next 
dependent on it?

> I assume that some things here need to be built with HOSTCC?

I suspect that's the culprit. Do you now mandate people to have PowerPC systems as 
a requirement to merge to linux-next? How are people supposed to be able to test 
that rare type of build method which does not matter to 99.99% of our kernel 
testers and users?

Thanks,

	Ingo

Re: linux-next: build failure after merge of the tip tree

[Sedat Dilek]

On Tue, Mar 1, 2016 at 8:07 AM, Ingo Molnar <mingo@kernel.org> wrote:
>
> * Stephen Rothwell <sfr@canb.auug.org.au> wrote:
>
>> Hi all,
>>
>> After merging the tip tree, today's linux-next build (x86_64 allmodconfig)
>> failed like this:
>>
>>   DESCEND  objtool
>>   CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/builtin-check.o
>>   CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/special.o
>>   CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/elf.o
>>   CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/objtool.o
>>   MKDIR    /home/sfr/next/x86_64_allmodconfig/tools/objtool/arch/x86/insn/
>>   CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/libstring.o
>> elf.c:22:23: fatal error: sys/types.h: No such file or directory
>> compilation terminated.
>>   CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/exec-cmd.o
>>   CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/help.o
>> builtin-check.c:28:20: fatal error: string.h: No such file or directory
>> compilation terminated.
>> objtool.c:28:19: fatal error: stdio.h: No such file or directory
>> compilation terminated.
>>
>> and further errors ...
>>
>> This build is done with a PowerPC hosted cross compiler with no glibc.
>
> Ugh, what a rare and weird way to build an x86 kernel, and you made linux-next
> dependent on it?
>
>> I assume that some things here need to be built with HOSTCC?
>
> I suspect that's the culprit. Do you now mandate people to have PowerPC systems as
> a requirement to merge to linux-next? How are people supposed to be able to test
> that rare type of build method which does not matter to 99.99% of our kernel
> testers and users?
>

>From my experience in using different $COMPILER you should always pass
CC and HOSTCC in your make-line when building a Linux-kernel or
playing with the Kconfig-system.

When building my llvm-toolchain with make/autoconf I had also to pass
CC and CXX to my configure-line otherwise you got misconfiguration.

[ EXAMPLE: Linux Kconfig-system ]

$ MAKE="make V=1" ; COMPILER="mycompiler" ; MAKE_OPTS="CC=$COMPILER
HOSTCC=$COMPILER"

$ yes "" | $MAKE $MAKE_OPTS oldconfig && $MAKE $MAKE_OPTS
silentoldconfig < /dev/null

- Sedat -

Re: linux-next: build failure after merge of the tip tree

[H. Peter Anvin]

On February 29, 2016 11:28:22 PM PST, Sedat Dilek <sedat.dilek@gmail.com> wrote:
>On Tue, Mar 1, 2016 at 8:07 AM, Ingo Molnar <mingo@kernel.org> wrote:
>>
>> * Stephen Rothwell <sfr@canb.auug.org.au> wrote:
>>
>>> Hi all,
>>>
>>> After merging the tip tree, today's linux-next build (x86_64
>allmodconfig)
>>> failed like this:
>>>
>>>   DESCEND  objtool
>>>   CC      
>/home/sfr/next/x86_64_allmodconfig/tools/objtool/builtin-check.o
>>>   CC      
>/home/sfr/next/x86_64_allmodconfig/tools/objtool/special.o
>>>   CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/elf.o
>>>   CC      
>/home/sfr/next/x86_64_allmodconfig/tools/objtool/objtool.o
>>>   MKDIR   
>/home/sfr/next/x86_64_allmodconfig/tools/objtool/arch/x86/insn/
>>>   CC      
>/home/sfr/next/x86_64_allmodconfig/tools/objtool/libstring.o
>>> elf.c:22:23: fatal error: sys/types.h: No such file or directory
>>> compilation terminated.
>>>   CC      
>/home/sfr/next/x86_64_allmodconfig/tools/objtool/exec-cmd.o
>>>   CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/help.o
>>> builtin-check.c:28:20: fatal error: string.h: No such file or
>directory
>>> compilation terminated.
>>> objtool.c:28:19: fatal error: stdio.h: No such file or directory
>>> compilation terminated.
>>>
>>> and further errors ...
>>>
>>> This build is done with a PowerPC hosted cross compiler with no
>glibc.
>>
>> Ugh, what a rare and weird way to build an x86 kernel, and you made
>linux-next
>> dependent on it?
>>
>>> I assume that some things here need to be built with HOSTCC?
>>
>> I suspect that's the culprit. Do you now mandate people to have
>PowerPC systems as
>> a requirement to merge to linux-next? How are people supposed to be
>able to test
>> that rare type of build method which does not matter to 99.99% of our
>kernel
>> testers and users?
>>
>
>From my experience in using different $COMPILER you should always pass
>CC and HOSTCC in your make-line when building a Linux-kernel or
>playing with the Kconfig-system.
>
>When building my llvm-toolchain with make/autoconf I had also to pass
>CC and CXX to my configure-line otherwise you got misconfiguration.
>
>[ EXAMPLE: Linux Kconfig-system ]
>
>$ MAKE="make V=1" ; COMPILER="mycompiler" ; MAKE_OPTS="CC=$COMPILER
>HOSTCC=$COMPILER"
>
>$ yes "" | $MAKE $MAKE_OPTS oldconfig && $MAKE $MAKE_OPTS
>silentoldconfig < /dev/null
>
>- Sedat -

That is not the issue here.  The problem is clearly that objtool is a host program and not compiled with host cc.  So it is a good thing to test even though it is weird, because it affects real use cases.

As x86 is far and beyond the most widely used host architecture, cross-compiling x86 is more likely to involve compiler differences than actually using another host, or possibly compiling 32 bits on a system without the 32-bit libc installed, but it should still work.
-- 
Sent from my Android device with K-9 Mail. Please excuse brevity and formatting.

Re: linux-next: build failure after merge of the tip tree

[Sedat Dilek]

On Tue, Mar 1, 2016 at 8:39 AM, H. Peter Anvin <hpa@zytor.com> wrote:
> On February 29, 2016 11:28:22 PM PST, Sedat Dilek <sedat.dilek@gmail.com> wrote:
>>On Tue, Mar 1, 2016 at 8:07 AM, Ingo Molnar <mingo@kernel.org> wrote:
>>>
>>> * Stephen Rothwell <sfr@canb.auug.org.au> wrote:
>>>
>>>> Hi all,
>>>>
>>>> After merging the tip tree, today's linux-next build (x86_64
>>allmodconfig)
>>>> failed like this:
>>>>
>>>>   DESCEND  objtool
>>>>   CC
>>/home/sfr/next/x86_64_allmodconfig/tools/objtool/builtin-check.o
>>>>   CC
>>/home/sfr/next/x86_64_allmodconfig/tools/objtool/special.o
>>>>   CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/elf.o
>>>>   CC
>>/home/sfr/next/x86_64_allmodconfig/tools/objtool/objtool.o
>>>>   MKDIR
>>/home/sfr/next/x86_64_allmodconfig/tools/objtool/arch/x86/insn/
>>>>   CC
>>/home/sfr/next/x86_64_allmodconfig/tools/objtool/libstring.o
>>>> elf.c:22:23: fatal error: sys/types.h: No such file or directory
>>>> compilation terminated.
>>>>   CC
>>/home/sfr/next/x86_64_allmodconfig/tools/objtool/exec-cmd.o
>>>>   CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/help.o
>>>> builtin-check.c:28:20: fatal error: string.h: No such file or
>>directory
>>>> compilation terminated.
>>>> objtool.c:28:19: fatal error: stdio.h: No such file or directory
>>>> compilation terminated.
>>>>
>>>> and further errors ...
>>>>
>>>> This build is done with a PowerPC hosted cross compiler with no
>>glibc.
>>>
>>> Ugh, what a rare and weird way to build an x86 kernel, and you made
>>linux-next
>>> dependent on it?
>>>
>>>> I assume that some things here need to be built with HOSTCC?
>>>
>>> I suspect that's the culprit. Do you now mandate people to have
>>PowerPC systems as
>>> a requirement to merge to linux-next? How are people supposed to be
>>able to test
>>> that rare type of build method which does not matter to 99.99% of our
>>kernel
>>> testers and users?
>>>
>>
> >From my experience in using different $COMPILER you should always pass
>>CC and HOSTCC in your make-line when building a Linux-kernel or
>>playing with the Kconfig-system.
>>
>>When building my llvm-toolchain with make/autoconf I had also to pass
>>CC and CXX to my configure-line otherwise you got misconfiguration.
>>
>>[ EXAMPLE: Linux Kconfig-system ]
>>
>>$ MAKE="make V=1" ; COMPILER="mycompiler" ; MAKE_OPTS="CC=$COMPILER
>>HOSTCC=$COMPILER"
>>
>>$ yes "" | $MAKE $MAKE_OPTS oldconfig && $MAKE $MAKE_OPTS
>>silentoldconfig < /dev/null
>>
>>- Sedat -
>
> That is not the issue here.  The problem is clearly that objtool is a host program and not compiled with host cc.  So it is a good thing to test even though it is weird, because it affects real use cases.
>
> As x86 is far and beyond the most widely used host architecture, cross-compiling x86 is more likely to involve compiler differences than actually using another host, or possibly compiling 32 bits on a system without the 32-bit libc installed, but it should still work.
>

Thanks for the clarification.

I talked about my experiences in software building in general.

When this is a "tools/objtool problem" then someone should address
this to "tools/objtool maintainers/folks" or whoever else is
responsible.

- Sedat -

Re: linux-next: build failure after merge of the tip tree

[Ingo Molnar]

* H. Peter Anvin <hpa@zytor.com> wrote:

> That is not the issue here.  The problem is clearly that objtool is a host 
> program and not compiled with host cc.  So it is a good thing to test even 
> though it is weird, because it affects real use cases.

Absolutely, it's a real bug that should be fixed. What is counterproductive is 
that this rare and hard to replicate build modus is now a must-have test for 
linux-next inclusion.

I already cross-build to 20+ weird, rarely used architectures, slowing down the 
linux-next merge integration test immensely and wasting quite a bit of 
electricity. linux-next making it even harder to test for is a step backwards.

Thanks,

	Ingo

Re: linux-next: build failure after merge of the tip tree

[Stephen Rothwell]

Hi Ingo,

On Tue, 1 Mar 2016 08:07:50 +0100 Ingo Molnar <mingo@kernel.org> wrote:
>
> > This build is done with a PowerPC hosted cross compiler with no glibc.  
> 
> Ugh, what a rare and weird way to build an x86 kernel, and you made linux-next 
> dependent on it?

It is just the fastest hardware I currently have access to (you remember
who I work for, right? ;-)).  I have always done at least part of the
linux-next building (daily, or overnight) on PowerPC hardware and this
is only the 2nd or third time in over 8 years that it has found an
issue like this.

> > I assume that some things here need to be built with HOSTCC?  
> 
> I suspect that's the culprit.

Good, hopefully it is not too hard to fix.

-- 
Cheers,
Stephen Rothwell

[PATCH] objtool: Disable stack validation when CROSS_COMPILE is used

[Josh Poimboeuf]

On Tue, Mar 01, 2016 at 08:40:01PM +1100, Stephen Rothwell wrote:
> Hi Ingo,
> 
> On Tue, 1 Mar 2016 08:07:50 +0100 Ingo Molnar <mingo@kernel.org> wrote:
> >
> > > This build is done with a PowerPC hosted cross compiler with no glibc.  
> > 
> > Ugh, what a rare and weird way to build an x86 kernel, and you made linux-next 
> > dependent on it?
> 
> It is just the fastest hardware I currently have access to (you remember
> who I work for, right? ;-)).  I have always done at least part of the
> linux-next building (daily, or overnight) on PowerPC hardware and this
> is only the 2nd or third time in over 8 years that it has found an
> issue like this.
> 
> > > I assume that some things here need to be built with HOSTCC?  
> > 
> > I suspect that's the culprit.
> 
> Good, hopefully it is not too hard to fix.

Changing it to use the host compiler would probably be an easy fix, but
that would expose a harder bug related to endianness.

objtool uses the kernel x86 decoder (arch/x86/lib/insn.c) which is
endian-ignorant.  If it tries to analyze reverse endian binaries it gets
confused.  And since CONFIG_STACK_VALIDATION causes objtool to analyze
every .o file in the build, it'll spit out a ton of false warnings.

How about the below workaround patch to disable objtool and warn when
CROSS_COMPILE is used?  If anybody complains about lack of cross-compile
support later, we could try to fix it then.


>From a3c65947011a420743f308b698171c4209105d3f Mon Sep 17 00:00:00 2001
Message-Id: <a3c65947011a420743f308b698171c4209105d3f.1456868910.git.jpoimboe@redhat.com>
From: Josh Poimboeuf <jpoimboe@redhat.com>
Date: Tue, 1 Mar 2016 13:35:51 -0600
Subject: [PATCH] objtool: Disable stack validation when CROSS_COMPILE is used

When building with CONFIG_STACK_VALIDATION on a PowerPC host using an
x86 cross-compiler, Stephen Rothwell saw the following objtool build
errors:

    DESCEND  objtool
    CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/builtin-check.o
    CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/special.o
    CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/elf.o
    CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/objtool.o
    MKDIR    /home/sfr/next/x86_64_allmodconfig/tools/objtool/arch/x86/insn/
    CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/libstring.o
  elf.c:22:23: fatal error: sys/types.h: No such file or directory
  compilation terminated.
    CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/exec-cmd.o
    CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/help.o
  builtin-check.c:28:20: fatal error: string.h: No such file or directory
  compilation terminated.
  objtool.c:28:19: fatal error: stdio.h: No such file or directory
  compilation terminated.

The problem is that objtool was compiled with the cross compiler instead
of the host compiler.  But even if that were fixed, we'd still have a
problem with endianness.  objtool's x86 decoder (copied from
arch/x86/lib/insn.c) assumes that the endianness of the host and target
are the same.  When analyzing a little-endian x86 binary on a big-endian
host, it will get confused and spit out a bunch of false positive
warnings during the build.

Eventually we may want to add endian awareness to x86 objtool, but
that's generally a rare edge case and it's not clear if anybody would
use it.  For now, when a cross-compiler is used, just disable
CONFIG_STACK_VALIDATION and emit a warning.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
 Makefile               | 12 +++++++++++-
 scripts/Makefile.build |  4 +++-
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index 8cc926f..b59007c 100644
--- a/Makefile
+++ b/Makefile
@@ -998,8 +998,18 @@ prepare0: archprepare FORCE
 # All the preparing..
 prepare: prepare0 prepare-objtool
 
+
+ifdef CONFIG_STACK_VALIDATION
+  ifeq ($(CROSS_COMPILE),)
+    objtool_target := tools/objtool FORCE
+  else
+    $(warning Stack validation is not supported with cross-compilation.  Disabling CONFIG_STACK_VALIDATION!)
+  endif
+endif
+
 PHONY += prepare-objtool
-prepare-objtool: $(if $(CONFIG_STACK_VALIDATION), tools/objtool FORCE)
+prepare-objtool: $(objtool_target)
+
 
 # Generate some files
 # ---------------------------------------------------------------------------
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 130a452..973bb26 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -242,6 +242,7 @@ cmd_record_mcount =						\
 endif
 
 ifdef CONFIG_STACK_VALIDATION
+ifeq ($(CROSS_COMPILE),)
 
 __objtool_obj := $(objtree)/tools/objtool/objtool
 
@@ -260,13 +261,14 @@ objtool_obj = $(if $(patsubst y%,, \
 	$(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n), \
 	$(__objtool_obj))
 
+endif # CROSS_COMPILE
 endif # CONFIG_STACK_VALIDATION
 
 define rule_cc_o_c
 	$(call echo-cmd,checksrc) $(cmd_checksrc)			  \
 	$(call echo-cmd,cc_o_c) $(cmd_cc_o_c);				  \
 	$(cmd_modversions)						  \
-	$(cmd_objtool)						  \
+	$(cmd_objtool)							  \
 	$(call echo-cmd,record_mcount)					  \
 	$(cmd_record_mcount)						  \
 	scripts/basic/fixdep $(depfile) $@ '$(call make-cmd,cc_o_c)' >    \
-- 
2.4.3

Re: [PATCH] objtool: Disable stack validation when CROSS_COMPILE is used

[Stephen Rothwell]

Hi Josh,

On Tue, 1 Mar 2016 15:54:51 -0600 Josh Poimboeuf <jpoimboe@redhat.com> wrote:
>
> Changing it to use the host compiler would probably be an easy fix, but
> that would expose a harder bug related to endianness.

Just by luck, my PowerPC host is little endian :-)

> How about the below workaround patch to disable objtool and warn when
> CROSS_COMPILE is used?  If anybody complains about lack of cross-compile
> support later, we could try to fix it then.

This seems reasonable.

> From a3c65947011a420743f308b698171c4209105d3f Mon Sep 17 00:00:00 2001
> Message-Id: <a3c65947011a420743f308b698171c4209105d3f.1456868910.git.jpoimboe@redhat.com>
> From: Josh Poimboeuf <jpoimboe@redhat.com>
> Date: Tue, 1 Mar 2016 13:35:51 -0600
> Subject: [PATCH] objtool: Disable stack validation when CROSS_COMPILE is used

I have applied this to the merge of the tip tree in linux-next today
and it compiles fine for me.  I will continue applying it until
something better comes along or it is applied to the tip tree.

Thanks for that.
-- 
Cheers,
Stephen Rothwell

Re: [PATCH] objtool: Disable stack validation when CROSS_COMPILE is used

[Josh Poimboeuf]

On Wed, Mar 02, 2016 at 01:27:35PM +1100, Stephen Rothwell wrote:
> Hi Josh,
> 
> On Tue, 1 Mar 2016 15:54:51 -0600 Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> >
> > Changing it to use the host compiler would probably be an easy fix, but
> > that would expose a harder bug related to endianness.
> 
> Just by luck, my PowerPC host is little endian :-)

Aha!  In that case, I think I'll take a different approach and try to
add support for CROSS_COMPILE.

We'll need it anyway, later on, when we port objtool to more
architectures.

> > How about the below workaround patch to disable objtool and warn when
> > CROSS_COMPILE is used?  If anybody complains about lack of cross-compile
> > support later, we could try to fix it then.
> 
> This seems reasonable.
> 
> > From a3c65947011a420743f308b698171c4209105d3f Mon Sep 17 00:00:00 2001
> > Message-Id: <a3c65947011a420743f308b698171c4209105d3f.1456868910.git.jpoimboe@redhat.com>
> > From: Josh Poimboeuf <jpoimboe@redhat.com>
> > Date: Tue, 1 Mar 2016 13:35:51 -0600
> > Subject: [PATCH] objtool: Disable stack validation when CROSS_COMPILE is used
> 
> I have applied this to the merge of the tip tree in linux-next today
> and it compiles fine for me.  I will continue applying it until
> something better comes along or it is applied to the tip tree.

Thanks.  I should have the patch(es) soon.  If/when they get merged,
I'll let you know, and then you can drop this one.

-- 
Josh

Re: [PATCH] objtool: Disable stack validation when CROSS_COMPILE is used

[Stephen Rothwell]

Hi Josh,

On Wed, 2 Mar 2016 15:17:26 -0600 Josh Poimboeuf <jpoimboe@redhat.com> wrote:
>
> On Wed, Mar 02, 2016 at 01:27:35PM +1100, Stephen Rothwell wrote:
> > 
> > On Tue, 1 Mar 2016 15:54:51 -0600 Josh Poimboeuf <jpoimboe@redhat.com> wrote:  
> > >
> > > Changing it to use the host compiler would probably be an easy fix, but
> > > that would expose a harder bug related to endianness.  
> > 
> > Just by luck, my PowerPC host is little endian :-)  
> 
> Aha!  In that case, I think I'll take a different approach and try to
> add support for CROSS_COMPILE.
> 
> We'll need it anyway, later on, when we port objtool to more
> architectures.

That would be great.  I was discussing this briefly with the powerpc
maintainer and he expressed some interest.

> Thanks.  I should have the patch(es) soon.  If/when they get merged,
> I'll let you know, and then you can drop this one.

OK, I will keep an eye out - I usually notice when stuff get fixed, but
a heads up is always helpful.

-- 
Cheers,
Stephen Rothwell

[PATCH 0/2] objtool: Cross-compilation support

[Josh Poimboeuf]

This adds the ability for CONFIG_STACK_VALIDATION to work in a
cross-compiled environment against an x86 kernel.  Based on tip/master.

Josh Poimboeuf (2):
  x86/asm/decoder: Use explicitly signed chars
  objtool: Support CROSS_COMPILE

 arch/x86/lib/insn.c                     |  6 +++---
 tools/lib/subcmd/Makefile               |  6 ++++--
 tools/objtool/Makefile                  | 17 ++++++++++-------
 tools/objtool/arch/x86/insn/insn.c      |  6 +++---
 tools/perf/util/intel-pt-decoder/insn.c |  6 +++---
 5 files changed, 23 insertions(+), 18 deletions(-)

-- 
2.4.3

[PATCH 1/2] x86/asm/decoder: Use explicitly signed chars

[Josh Poimboeuf]

When running objtool on a ppc64le host to analyze x86 binaries, it
reports a lot of false warnings like:

  ipc/compat_mq.o: warning: objtool: compat_SyS_mq_open()+0x91: can't find jump dest instruction at .text+0x3a5

The warnings are caused by the x86 instruction decoder setting the wrong
value for the jump instruction's immediate field because it assumes that
"char == signed char", which isn't true for all architectures.  When
converting char to int, gcc sign-extends on x86 but doesn't sign-extend
on ppc64le.

According to the gcc man page, that's a feature, not a bug:

> Each kind of machine has a default for what "char" should be.  It is
> either like "unsigned char" by default or like "signed char" by
> default.
>
> Ideally, a portable program should always use "signed char" or
> "unsigned char" when it depends on the signedness of an object.

Conform to the "standards" by changing the "char" casts to "signed
char".  This results in no actual changes to the object code on x86.

Note: the x86 decoder now lives in three different locations in the
kernel tree, which are all kept in sync via makefile checks and
warnings: in-kernel, perf, and objtool.  This fixes all three locations.
Eventually we should probably try to at least converge the two separate
"tools" locations into a single shared location.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
 arch/x86/lib/insn.c                     | 6 +++---
 tools/objtool/arch/x86/insn/insn.c      | 6 +++---
 tools/perf/util/intel-pt-decoder/insn.c | 6 +++---
 3 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/arch/x86/lib/insn.c b/arch/x86/lib/insn.c
index 8f72b33..1a41693 100644
--- a/arch/x86/lib/insn.c
+++ b/arch/x86/lib/insn.c
@@ -374,7 +374,7 @@ void insn_get_displacement(struct insn *insn)
 		if (mod == 3)
 			goto out;
 		if (mod == 1) {
-			insn->displacement.value = get_next(char, insn);
+			insn->displacement.value = get_next(signed char, insn);
 			insn->displacement.nbytes = 1;
 		} else if (insn->addr_bytes == 2) {
 			if ((mod == 0 && rm == 6) || mod == 2) {
@@ -532,7 +532,7 @@ void insn_get_immediate(struct insn *insn)
 
 	switch (inat_immediate_size(insn->attr)) {
 	case INAT_IMM_BYTE:
-		insn->immediate.value = get_next(char, insn);
+		insn->immediate.value = get_next(signed char, insn);
 		insn->immediate.nbytes = 1;
 		break;
 	case INAT_IMM_WORD:
@@ -566,7 +566,7 @@ void insn_get_immediate(struct insn *insn)
 		goto err_out;
 	}
 	if (inat_has_second_immediate(insn->attr)) {
-		insn->immediate2.value = get_next(char, insn);
+		insn->immediate2.value = get_next(signed char, insn);
 		insn->immediate2.nbytes = 1;
 	}
 done:
diff --git a/tools/objtool/arch/x86/insn/insn.c b/tools/objtool/arch/x86/insn/insn.c
index 47314a6..9f26eae 100644
--- a/tools/objtool/arch/x86/insn/insn.c
+++ b/tools/objtool/arch/x86/insn/insn.c
@@ -374,7 +374,7 @@ void insn_get_displacement(struct insn *insn)
 		if (mod == 3)
 			goto out;
 		if (mod == 1) {
-			insn->displacement.value = get_next(char, insn);
+			insn->displacement.value = get_next(signed char, insn);
 			insn->displacement.nbytes = 1;
 		} else if (insn->addr_bytes == 2) {
 			if ((mod == 0 && rm == 6) || mod == 2) {
@@ -532,7 +532,7 @@ void insn_get_immediate(struct insn *insn)
 
 	switch (inat_immediate_size(insn->attr)) {
 	case INAT_IMM_BYTE:
-		insn->immediate.value = get_next(char, insn);
+		insn->immediate.value = get_next(signed char, insn);
 		insn->immediate.nbytes = 1;
 		break;
 	case INAT_IMM_WORD:
@@ -566,7 +566,7 @@ void insn_get_immediate(struct insn *insn)
 		goto err_out;
 	}
 	if (inat_has_second_immediate(insn->attr)) {
-		insn->immediate2.value = get_next(char, insn);
+		insn->immediate2.value = get_next(signed char, insn);
 		insn->immediate2.nbytes = 1;
 	}
 done:
diff --git a/tools/perf/util/intel-pt-decoder/insn.c b/tools/perf/util/intel-pt-decoder/insn.c
index 47314a6..9f26eae 100644
--- a/tools/perf/util/intel-pt-decoder/insn.c
+++ b/tools/perf/util/intel-pt-decoder/insn.c
@@ -374,7 +374,7 @@ void insn_get_displacement(struct insn *insn)
 		if (mod == 3)
 			goto out;
 		if (mod == 1) {
-			insn->displacement.value = get_next(char, insn);
+			insn->displacement.value = get_next(signed char, insn);
 			insn->displacement.nbytes = 1;
 		} else if (insn->addr_bytes == 2) {
 			if ((mod == 0 && rm == 6) || mod == 2) {
@@ -532,7 +532,7 @@ void insn_get_immediate(struct insn *insn)
 
 	switch (inat_immediate_size(insn->attr)) {
 	case INAT_IMM_BYTE:
-		insn->immediate.value = get_next(char, insn);
+		insn->immediate.value = get_next(signed char, insn);
 		insn->immediate.nbytes = 1;
 		break;
 	case INAT_IMM_WORD:
@@ -566,7 +566,7 @@ void insn_get_immediate(struct insn *insn)
 		goto err_out;
 	}
 	if (inat_has_second_immediate(insn->attr)) {
-		insn->immediate2.value = get_next(char, insn);
+		insn->immediate2.value = get_next(signed char, insn);
 		insn->immediate2.nbytes = 1;
 	}
 done:
-- 
2.4.3

[tip:core/objtool] x86/asm/decoder: Use explicitly signed chars

[tip-bot for Josh Poimboeuf]

Commit-ID:  19072f23d1d785c093b7f81cb1fb161e7a13ecc0
Gitweb:     http://git.kernel.org/tip/19072f23d1d785c093b7f81cb1fb161e7a13ecc0
Author:     Josh Poimboeuf <jpoimboe@redhat.com>
AuthorDate: Wed, 2 Mar 2016 18:39:36 -0600
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Thu, 3 Mar 2016 16:13:00 +0100

x86/asm/decoder: Use explicitly signed chars

When running objtool on a ppc64le host to analyze x86 binaries, it
reports a lot of false warnings like:

  ipc/compat_mq.o: warning: objtool: compat_SyS_mq_open()+0x91: can't find jump dest instruction at .text+0x3a5

The warnings are caused by the x86 instruction decoder setting the wrong
value for the jump instruction's immediate field because it assumes that
"char == signed char", which isn't true for all architectures.  When
converting char to int, gcc sign-extends on x86 but doesn't sign-extend
on ppc64le.

According to the gcc man page, that's a feature, not a bug:

  > Each kind of machine has a default for what "char" should be.  It is
  > either like "unsigned char" by default or like "signed char" by
  > default.
  >
  > Ideally, a portable program should always use "signed char" or
  > "unsigned char" when it depends on the signedness of an object.

Conform to the "standards" by changing the "char" casts to "signed
char".  This results in no actual changes to the object code on x86.

Note: the x86 decoder now lives in three different locations in the
kernel tree, which are all kept in sync via makefile checks and
warnings: in-kernel, perf, and objtool.  This fixes all three locations.
Eventually we should probably try to at least converge the two separate
"tools" locations into a single shared location.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/9dd4161719b20e6def9564646d68bfbe498c549f.1456962210.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/lib/insn.c                     | 6 +++---
 tools/objtool/arch/x86/insn/insn.c      | 6 +++---
 tools/perf/util/intel-pt-decoder/insn.c | 6 +++---
 3 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/arch/x86/lib/insn.c b/arch/x86/lib/insn.c
index 8f72b33..1a41693 100644
--- a/arch/x86/lib/insn.c
+++ b/arch/x86/lib/insn.c
@@ -374,7 +374,7 @@ void insn_get_displacement(struct insn *insn)
 		if (mod == 3)
 			goto out;
 		if (mod == 1) {
-			insn->displacement.value = get_next(char, insn);
+			insn->displacement.value = get_next(signed char, insn);
 			insn->displacement.nbytes = 1;
 		} else if (insn->addr_bytes == 2) {
 			if ((mod == 0 && rm == 6) || mod == 2) {
@@ -532,7 +532,7 @@ void insn_get_immediate(struct insn *insn)
 
 	switch (inat_immediate_size(insn->attr)) {
 	case INAT_IMM_BYTE:
-		insn->immediate.value = get_next(char, insn);
+		insn->immediate.value = get_next(signed char, insn);
 		insn->immediate.nbytes = 1;
 		break;
 	case INAT_IMM_WORD:
@@ -566,7 +566,7 @@ void insn_get_immediate(struct insn *insn)
 		goto err_out;
 	}
 	if (inat_has_second_immediate(insn->attr)) {
-		insn->immediate2.value = get_next(char, insn);
+		insn->immediate2.value = get_next(signed char, insn);
 		insn->immediate2.nbytes = 1;
 	}
 done:
diff --git a/tools/objtool/arch/x86/insn/insn.c b/tools/objtool/arch/x86/insn/insn.c
index 47314a6..9f26eae 100644
--- a/tools/objtool/arch/x86/insn/insn.c
+++ b/tools/objtool/arch/x86/insn/insn.c
@@ -374,7 +374,7 @@ void insn_get_displacement(struct insn *insn)
 		if (mod == 3)
 			goto out;
 		if (mod == 1) {
-			insn->displacement.value = get_next(char, insn);
+			insn->displacement.value = get_next(signed char, insn);
 			insn->displacement.nbytes = 1;
 		} else if (insn->addr_bytes == 2) {
 			if ((mod == 0 && rm == 6) || mod == 2) {
@@ -532,7 +532,7 @@ void insn_get_immediate(struct insn *insn)
 
 	switch (inat_immediate_size(insn->attr)) {
 	case INAT_IMM_BYTE:
-		insn->immediate.value = get_next(char, insn);
+		insn->immediate.value = get_next(signed char, insn);
 		insn->immediate.nbytes = 1;
 		break;
 	case INAT_IMM_WORD:
@@ -566,7 +566,7 @@ void insn_get_immediate(struct insn *insn)
 		goto err_out;
 	}
 	if (inat_has_second_immediate(insn->attr)) {
-		insn->immediate2.value = get_next(char, insn);
+		insn->immediate2.value = get_next(signed char, insn);
 		insn->immediate2.nbytes = 1;
 	}
 done:
diff --git a/tools/perf/util/intel-pt-decoder/insn.c b/tools/perf/util/intel-pt-decoder/insn.c
index 47314a6..9f26eae 100644
--- a/tools/perf/util/intel-pt-decoder/insn.c
+++ b/tools/perf/util/intel-pt-decoder/insn.c
@@ -374,7 +374,7 @@ void insn_get_displacement(struct insn *insn)
 		if (mod == 3)
 			goto out;
 		if (mod == 1) {
-			insn->displacement.value = get_next(char, insn);
+			insn->displacement.value = get_next(signed char, insn);
 			insn->displacement.nbytes = 1;
 		} else if (insn->addr_bytes == 2) {
 			if ((mod == 0 && rm == 6) || mod == 2) {
@@ -532,7 +532,7 @@ void insn_get_immediate(struct insn *insn)
 
 	switch (inat_immediate_size(insn->attr)) {
 	case INAT_IMM_BYTE:
-		insn->immediate.value = get_next(char, insn);
+		insn->immediate.value = get_next(signed char, insn);
 		insn->immediate.nbytes = 1;
 		break;
 	case INAT_IMM_WORD:
@@ -566,7 +566,7 @@ void insn_get_immediate(struct insn *insn)
 		goto err_out;
 	}
 	if (inat_has_second_immediate(insn->attr)) {
-		insn->immediate2.value = get_next(char, insn);
+		insn->immediate2.value = get_next(signed char, insn);
 		insn->immediate2.nbytes = 1;
 	}
 done:

Re: [tip:core/objtool] x86/asm/decoder: Use explicitly signed chars

[H. Peter Anvin]

On March 3, 2016 8:51:39 AM PST, tip-bot for Josh Poimboeuf <tipbot@zytor.com> wrote:
>Commit-ID:  19072f23d1d785c093b7f81cb1fb161e7a13ecc0
>Gitweb:    
>http://git.kernel.org/tip/19072f23d1d785c093b7f81cb1fb161e7a13ecc0
>Author:     Josh Poimboeuf <jpoimboe@redhat.com>
>AuthorDate: Wed, 2 Mar 2016 18:39:36 -0600
>Committer:  Ingo Molnar <mingo@kernel.org>
>CommitDate: Thu, 3 Mar 2016 16:13:00 +0100
>
>x86/asm/decoder: Use explicitly signed chars
>
>When running objtool on a ppc64le host to analyze x86 binaries, it
>reports a lot of false warnings like:
>
>ipc/compat_mq.o: warning: objtool: compat_SyS_mq_open()+0x91: can't
>find jump dest instruction at .text+0x3a5
>
>The warnings are caused by the x86 instruction decoder setting the
>wrong
>value for the jump instruction's immediate field because it assumes
>that
>"char == signed char", which isn't true for all architectures.  When
>converting char to int, gcc sign-extends on x86 but doesn't sign-extend
>on ppc64le.
>
>According to the gcc man page, that's a feature, not a bug:
>
> > Each kind of machine has a default for what "char" should be.  It is
>  > either like "unsigned char" by default or like "signed char" by
>  > default.
>  >
>  > Ideally, a portable program should always use "signed char" or
>  > "unsigned char" when it depends on the signedness of an object.
>
>Conform to the "standards" by changing the "char" casts to "signed
>char".  This results in no actual changes to the object code on x86.
>
>Note: the x86 decoder now lives in three different locations in the
>kernel tree, which are all kept in sync via makefile checks and
>warnings: in-kernel, perf, and objtool.  This fixes all three
>locations.
>Eventually we should probably try to at least converge the two separate
>"tools" locations into a single shared location.
>
>Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
>Cc: Adrian Hunter <adrian.hunter@intel.com>
>Cc: Linus Torvalds <torvalds@linux-foundation.org>
>Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
>Cc: Michael Ellerman <mpe@ellerman.id.au>
>Cc: Peter Zijlstra <peterz@infradead.org>
>Cc: Stephen Rothwell <sfr@canb.auug.org.au>
>Cc: Thomas Gleixner <tglx@linutronix.de>
>Link:
>http://lkml.kernel.org/r/9dd4161719b20e6def9564646d68bfbe498c549f.1456962210.git.jpoimboe@redhat.com
>Signed-off-by: Ingo Molnar <mingo@kernel.org>
>---
> arch/x86/lib/insn.c                     | 6 +++---
> tools/objtool/arch/x86/insn/insn.c      | 6 +++---
> tools/perf/util/intel-pt-decoder/insn.c | 6 +++---
> 3 files changed, 9 insertions(+), 9 deletions(-)
>
>diff --git a/arch/x86/lib/insn.c b/arch/x86/lib/insn.c
>index 8f72b33..1a41693 100644
>--- a/arch/x86/lib/insn.c
>+++ b/arch/x86/lib/insn.c
>@@ -374,7 +374,7 @@ void insn_get_displacement(struct insn *insn)
> 		if (mod == 3)
> 			goto out;
> 		if (mod == 1) {
>-			insn->displacement.value = get_next(char, insn);
>+			insn->displacement.value = get_next(signed char, insn);
> 			insn->displacement.nbytes = 1;
> 		} else if (insn->addr_bytes == 2) {
> 			if ((mod == 0 && rm == 6) || mod == 2) {
>@@ -532,7 +532,7 @@ void insn_get_immediate(struct insn *insn)
> 
> 	switch (inat_immediate_size(insn->attr)) {
> 	case INAT_IMM_BYTE:
>-		insn->immediate.value = get_next(char, insn);
>+		insn->immediate.value = get_next(signed char, insn);
> 		insn->immediate.nbytes = 1;
> 		break;
> 	case INAT_IMM_WORD:
>@@ -566,7 +566,7 @@ void insn_get_immediate(struct insn *insn)
> 		goto err_out;
> 	}
> 	if (inat_has_second_immediate(insn->attr)) {
>-		insn->immediate2.value = get_next(char, insn);
>+		insn->immediate2.value = get_next(signed char, insn);
> 		insn->immediate2.nbytes = 1;
> 	}
> done:
>diff --git a/tools/objtool/arch/x86/insn/insn.c
>b/tools/objtool/arch/x86/insn/insn.c
>index 47314a6..9f26eae 100644
>--- a/tools/objtool/arch/x86/insn/insn.c
>+++ b/tools/objtool/arch/x86/insn/insn.c
>@@ -374,7 +374,7 @@ void insn_get_displacement(struct insn *insn)
> 		if (mod == 3)
> 			goto out;
> 		if (mod == 1) {
>-			insn->displacement.value = get_next(char, insn);
>+			insn->displacement.value = get_next(signed char, insn);
> 			insn->displacement.nbytes = 1;
> 		} else if (insn->addr_bytes == 2) {
> 			if ((mod == 0 && rm == 6) || mod == 2) {
>@@ -532,7 +532,7 @@ void insn_get_immediate(struct insn *insn)
> 
> 	switch (inat_immediate_size(insn->attr)) {
> 	case INAT_IMM_BYTE:
>-		insn->immediate.value = get_next(char, insn);
>+		insn->immediate.value = get_next(signed char, insn);
> 		insn->immediate.nbytes = 1;
> 		break;
> 	case INAT_IMM_WORD:
>@@ -566,7 +566,7 @@ void insn_get_immediate(struct insn *insn)
> 		goto err_out;
> 	}
> 	if (inat_has_second_immediate(insn->attr)) {
>-		insn->immediate2.value = get_next(char, insn);
>+		insn->immediate2.value = get_next(signed char, insn);
> 		insn->immediate2.nbytes = 1;
> 	}
> done:
>diff --git a/tools/perf/util/intel-pt-decoder/insn.c
>b/tools/perf/util/intel-pt-decoder/insn.c
>index 47314a6..9f26eae 100644
>--- a/tools/perf/util/intel-pt-decoder/insn.c
>+++ b/tools/perf/util/intel-pt-decoder/insn.c
>@@ -374,7 +374,7 @@ void insn_get_displacement(struct insn *insn)
> 		if (mod == 3)
> 			goto out;
> 		if (mod == 1) {
>-			insn->displacement.value = get_next(char, insn);
>+			insn->displacement.value = get_next(signed char, insn);
> 			insn->displacement.nbytes = 1;
> 		} else if (insn->addr_bytes == 2) {
> 			if ((mod == 0 && rm == 6) || mod == 2) {
>@@ -532,7 +532,7 @@ void insn_get_immediate(struct insn *insn)
> 
> 	switch (inat_immediate_size(insn->attr)) {
> 	case INAT_IMM_BYTE:
>-		insn->immediate.value = get_next(char, insn);
>+		insn->immediate.value = get_next(signed char, insn);
> 		insn->immediate.nbytes = 1;
> 		break;
> 	case INAT_IMM_WORD:
>@@ -566,7 +566,7 @@ void insn_get_immediate(struct insn *insn)
> 		goto err_out;
> 	}
> 	if (inat_has_second_immediate(insn->attr)) {
>-		insn->immediate2.value = get_next(char, insn);
>+		insn->immediate2.value = get_next(signed char, insn);
> 		insn->immediate2.nbytes = 1;
> 	}
> done:

It ought to be made specific as __s8 (or int8_t) really...
-- 
Sent from my Android device with K-9 Mail. Please excuse brevity and formatting.

[PATCH 2/2] objtool: Support CROSS_COMPILE

[Josh Poimboeuf]

When building with CONFIG_STACK_VALIDATION on a ppc64le host with an x86
cross-compiler, Stephen Rothwell saw the following objtool build errors:

    DESCEND  objtool
    CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/builtin-check.o
    CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/special.o
    CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/elf.o
    CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/objtool.o
    MKDIR    /home/sfr/next/x86_64_allmodconfig/tools/objtool/arch/x86/insn/
    CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/libstring.o
  elf.c:22:23: fatal error: sys/types.h: No such file or directory
  compilation terminated.
    CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/exec-cmd.o
    CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/help.o
  builtin-check.c:28:20: fatal error: string.h: No such file or directory
  compilation terminated.
  objtool.c:28:19: fatal error: stdio.h: No such file or directory
  compilation terminated.

It fails to build because it tries to compile objtool with the
cross-compiler instead of the host compiler.

Ensure that it always uses the host compiler by ignoring CROSS_COMPILE.

In order to do that properly, the libsubcmd.a library needs to be built
in tools/objtool/ rather than tools/lib/subcmd/.  The latter directory
contains the cross-compiled version which is needed for perf and
possibly other tools.

Note that cross-compiling for x86 on a _big_ endian system would result
in a bunch of false positive objtool warnings during the kernel build
because it isn't endian-aware.  But that's generally a rare edge case
and there haven't been any reports of anybody needing that.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
 tools/lib/subcmd/Makefile |  6 ++++--
 tools/objtool/Makefile    | 17 ++++++++++-------
 2 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/tools/lib/subcmd/Makefile b/tools/lib/subcmd/Makefile
index 629cf8c..1faecb8 100644
--- a/tools/lib/subcmd/Makefile
+++ b/tools/lib/subcmd/Makefile
@@ -8,8 +8,10 @@ srctree := $(patsubst %/,%,$(dir $(srctree)))
 #$(info Determined 'srctree' to be $(srctree))
 endif
 
-CC = $(CROSS_COMPILE)gcc
-AR = $(CROSS_COMPILE)ar
+CC ?= $(CROSS_COMPILE)gcc
+LD ?= $(CROSS_COMPILE)ld
+AR ?= $(CROSS_COMPILE)ar
+
 RM = rm -f
 
 MAKEFLAGS += --no-print-directory
diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile
index c4f0713..e4a6bd5 100644
--- a/tools/objtool/Makefile
+++ b/tools/objtool/Makefile
@@ -7,13 +7,19 @@ ARCH := x86
 endif
 endif
 
+# always use the host compiler
+CC = gcc
+LD = ld
+AR = ar
+
 ifeq ($(srctree),)
 srctree := $(patsubst %/,%,$(dir $(shell pwd)))
 srctree := $(patsubst %/,%,$(dir $(srctree)))
 endif
 
-SUBCMD_SRCDIR	= $(srctree)/tools/lib/subcmd/
-LIBSUBCMD	= $(if $(OUTPUT),$(OUTPUT),$(SUBCMD_SRCDIR))libsubcmd.a
+SUBCMD_SRCDIR		= $(srctree)/tools/lib/subcmd/
+LIBSUBCMD_OUTPUT	= $(if $(OUTPUT),$(OUTPUT),$(PWD)/)
+LIBSUBCMD		= $(LIBSUBCMD_OUTPUT)libsubcmd.a
 
 OBJTOOL    := $(OUTPUT)objtool
 OBJTOOL_IN := $(OBJTOOL)-in.o
@@ -45,12 +51,9 @@ $(OBJTOOL): $(LIBSUBCMD) $(OBJTOOL_IN)
 
 
 $(LIBSUBCMD): fixdep FORCE
-	$(Q)$(MAKE) -C $(SUBCMD_SRCDIR)
-
-$(LIBSUBCMD)-clean:
-	$(Q)$(MAKE) -C $(SUBCMD_SRCDIR) clean > /dev/null
+	$(Q)$(MAKE) -C $(SUBCMD_SRCDIR) OUTPUT=$(LIBSUBCMD_OUTPUT)
 
-clean: $(LIBSUBCMD)-clean
+clean:
 	$(call QUIET_CLEAN, objtool) $(RM) $(OBJTOOL)
 	$(Q)find $(OUTPUT) -name '*.o' -delete -o -name '\.*.cmd' -delete -o -name '\.*.d' -delete
 	$(Q)$(RM) $(OUTPUT)arch/x86/insn/inat-tables.c $(OUTPUT)fixdep
-- 
2.4.3

Re: [PATCH 2/2] objtool: Support CROSS_COMPILE

[Stephen Rothwell]

Hi Josh,

Just a couple of quick comments ...

On Wed,  2 Mar 2016 18:39:37 -0600 Josh Poimboeuf <jpoimboe@redhat.com> wrote:
>
> diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile
> index c4f0713..e4a6bd5 100644
> --- a/tools/objtool/Makefile
> +++ b/tools/objtool/Makefile

I was wondering if this would be more appropriate in scripts/objtool
since it is used during the building of the kernel.  Or does it have a
wider use?

> @@ -7,13 +7,19 @@ ARCH := x86
>  endif
>  endif
>  
> +# always use the host compiler
> +CC = gcc

We have HOSTCC with its associated HOSTCFLAGS etc ... I am not sure if
that is more appropriate (but it does take care of people using clang).

-- 
Cheers,
Stephen Rothwell

Re: [PATCH 2/2] objtool: Support CROSS_COMPILE

[Josh Poimboeuf]

On Thu, Mar 03, 2016 at 01:43:14PM +1100, Stephen Rothwell wrote:
> Hi Josh,
> 
> Just a couple of quick comments ...
> 
> On Wed,  2 Mar 2016 18:39:37 -0600 Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> >
> > diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile
> > index c4f0713..e4a6bd5 100644
> > --- a/tools/objtool/Makefile
> > +++ b/tools/objtool/Makefile
> 
> I was wondering if this would be more appropriate in scripts/objtool
> since it is used during the building of the kernel.  Or does it have a
> wider use?

Yeah, it was actually in the scripts/ dir in earlier revisions of the
patch set, for that very reason.  However, Ingo pointed out that it
could be useful beyond the kernel, so we graduated it to a "tool".

> > @@ -7,13 +7,19 @@ ARCH := x86
> >  endif
> >  endif
> >  
> > +# always use the host compiler
> > +CC = gcc
> 
> We have HOSTCC with its associated HOSTCFLAGS etc ... I am not sure if
> that is more appropriate (but it does take care of people using clang).

The "tools" are almost completely separate from the rest of the kernel.
They have their own scaled-down version of kbuild, which doesn't have
HOSTCC.

But yeah, we might eventually need to copy some of the host compilation
infrastructure from scripts/Makefile.host over to the tools/ side.

-- 
Josh

Re: [PATCH 2/2] objtool: Support CROSS_COMPILE

[Stephen Rothwell]

Hi Josh,

On Wed, 2 Mar 2016 21:20:58 -0600 Josh Poimboeuf <jpoimboe@redhat.com> wrote:
>
> On Thu, Mar 03, 2016 at 01:43:14PM +1100, Stephen Rothwell wrote:
> > 
> > I was wondering if this would be more appropriate in scripts/objtool
> > since it is used during the building of the kernel.  Or does it have a
> > wider use?  
> 
> Yeah, it was actually in the scripts/ dir in earlier revisions of the
> patch set, for that very reason.  However, Ingo pointed out that it
> could be useful beyond the kernel, so we graduated it to a "tool".
> 
> > 
> > We have HOSTCC with its associated HOSTCFLAGS etc ... I am not sure if
> > that is more appropriate (but it does take care of people using clang).  
> 
> The "tools" are almost completely separate from the rest of the kernel.
> They have their own scaled-down version of kbuild, which doesn't have
> HOSTCC.
> 
> But yeah, we might eventually need to copy some of the host compilation
> infrastructure from scripts/Makefile.host over to the tools/ side.

That all sounds sane, thanks.

I did not add this to linux-next today, but may tomorrow if people
think it is sensible to do so (for testing on a powerpcle host).  If I
do, I will just back out to the previous patch if it all goes south (so
it won't impact on the rest of the tip tree's testing).
-- 
Cheers,
Stephen Rothwell

Re: [PATCH 2/2] objtool: Support CROSS_COMPILE

[Josh Poimboeuf]

On Thu, Mar 03, 2016 at 02:38:43PM +1100, Stephen Rothwell wrote:
> Hi Josh,
> 
> On Wed, 2 Mar 2016 21:20:58 -0600 Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> >
> > On Thu, Mar 03, 2016 at 01:43:14PM +1100, Stephen Rothwell wrote:
> > > 
> > > I was wondering if this would be more appropriate in scripts/objtool
> > > since it is used during the building of the kernel.  Or does it have a
> > > wider use?  
> > 
> > Yeah, it was actually in the scripts/ dir in earlier revisions of the
> > patch set, for that very reason.  However, Ingo pointed out that it
> > could be useful beyond the kernel, so we graduated it to a "tool".
> > 
> > > 
> > > We have HOSTCC with its associated HOSTCFLAGS etc ... I am not sure if
> > > that is more appropriate (but it does take care of people using clang).  
> > 
> > The "tools" are almost completely separate from the rest of the kernel.
> > They have their own scaled-down version of kbuild, which doesn't have
> > HOSTCC.
> > 
> > But yeah, we might eventually need to copy some of the host compilation
> > infrastructure from scripts/Makefile.host over to the tools/ side.
> 
> That all sounds sane, thanks.
> 
> I did not add this to linux-next today, but may tomorrow if people
> think it is sensible to do so (for testing on a powerpcle host).  If I
> do, I will just back out to the previous patch if it all goes south (so
> it won't impact on the rest of the tip tree's testing).

Sounds good, thanks!

FWIW, I did test it on a ppc64le host with an x86 cross-compiler and it
worked fine (but more testing is certainly welcome).

-- 
Josh

Re: [PATCH 2/2] objtool: Support CROSS_COMPILE

[Ingo Molnar]

* Stephen Rothwell <sfr@canb.auug.org.au> wrote:

> Hi Josh,
> 
> On Wed, 2 Mar 2016 21:20:58 -0600 Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> >
> > On Thu, Mar 03, 2016 at 01:43:14PM +1100, Stephen Rothwell wrote:
> > > 
> > > I was wondering if this would be more appropriate in scripts/objtool
> > > since it is used during the building of the kernel.  Or does it have a
> > > wider use?  
> > 
> > Yeah, it was actually in the scripts/ dir in earlier revisions of the
> > patch set, for that very reason.  However, Ingo pointed out that it
> > could be useful beyond the kernel, so we graduated it to a "tool".
> > 
> > > 
> > > We have HOSTCC with its associated HOSTCFLAGS etc ... I am not sure if
> > > that is more appropriate (but it does take care of people using clang).  
> > 
> > The "tools" are almost completely separate from the rest of the kernel.
> > They have their own scaled-down version of kbuild, which doesn't have
> > HOSTCC.
> > 
> > But yeah, we might eventually need to copy some of the host compilation
> > infrastructure from scripts/Makefile.host over to the tools/ side.
> 
> That all sounds sane, thanks.
> 
> I did not add this to linux-next today, but may tomorrow if people
> think it is sensible to do so (for testing on a powerpcle host).  If I
> do, I will just back out to the previous patch if it all goes south (so
> it won't impact on the rest of the tip tree's testing).

I'll add Josh's fixes to -tip ASAP as well, so hopefully soon you can drop all 
linux-next specific patches related to this and it will all work Just Fine (tm).

Sorry about the breakage!

Thanks,

	Ingo

Re: [PATCH 2/2] objtool: Support CROSS_COMPILE

[Stephen Rothwell]

Hi Ingo,

On Thu, 3 Mar 2016 16:10:21 +0100 Ingo Molnar <mingo@kernel.org> wrote:
>
> I'll add Josh's fixes to -tip ASAP as well, so hopefully soon you can drop all 
> linux-next specific patches related to this and it will all work Just Fine (tm).

Thanks for that.  I have now dropped these patches.

> Sorry about the breakage!

Hey, it happens ..

-- 
Cheers,
Stephen Rothwell

Re: [PATCH 2/2] objtool: Support CROSS_COMPILE

[H. Peter Anvin]

On March 2, 2016 6:43:14 PM PST, Stephen Rothwell <sfr@canb.auug.org.au> wrote:
>Hi Josh,
>
>Just a couple of quick comments ...
>
>On Wed,  2 Mar 2016 18:39:37 -0600 Josh Poimboeuf <jpoimboe@redhat.com>
>wrote:
>>
>> diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile
>> index c4f0713..e4a6bd5 100644
>> --- a/tools/objtool/Makefile
>> +++ b/tools/objtool/Makefile
>
>I was wondering if this would be more appropriate in scripts/objtool
>since it is used during the building of the kernel.  Or does it have a
>wider use?
>
>> @@ -7,13 +7,19 @@ ARCH := x86
>>  endif
>>  endif
>>  
>> +# always use the host compiler
>> +CC = gcc
>
>We have HOSTCC with its associated HOSTCFLAGS etc ... I am not sure if
>that is more appropriate (but it does take care of people using clang).

This is what HOSTCC is for.  And yes, this belongs in scripts.
-- 
Sent from my Android device with K-9 Mail. Please excuse brevity and formatting.

[tip:core/objtool] objtool: Support CROSS_COMPILE

[tip-bot for Josh Poimboeuf]

Commit-ID:  c1d45c3abd49b5bf9447e435099c1b000dcde752
Gitweb:     http://git.kernel.org/tip/c1d45c3abd49b5bf9447e435099c1b000dcde752
Author:     Josh Poimboeuf <jpoimboe@redhat.com>
AuthorDate: Wed, 2 Mar 2016 18:39:37 -0600
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Thu, 3 Mar 2016 16:13:00 +0100

objtool: Support CROSS_COMPILE

When building with CONFIG_STACK_VALIDATION on a ppc64le host with an x86
cross-compiler, Stephen Rothwell saw the following objtool build errors:

    DESCEND  objtool
    CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/builtin-check.o
    CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/special.o
    CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/elf.o
    CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/objtool.o
    MKDIR    /home/sfr/next/x86_64_allmodconfig/tools/objtool/arch/x86/insn/
    CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/libstring.o
  elf.c:22:23: fatal error: sys/types.h: No such file or directory
  compilation terminated.
    CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/exec-cmd.o
    CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/help.o
  builtin-check.c:28:20: fatal error: string.h: No such file or directory
  compilation terminated.
  objtool.c:28:19: fatal error: stdio.h: No such file or directory
  compilation terminated.

It fails to build because it tries to compile objtool with the
cross-compiler instead of the host compiler.

Ensure that it always uses the host compiler by ignoring CROSS_COMPILE.

In order to do that properly, the libsubcmd.a library needs to be built
in tools/objtool/ rather than tools/lib/subcmd/.  The latter directory
contains the cross-compiled version which is needed for perf and
possibly other tools.

Note that cross-compiling for x86 on a _big_ endian system would result
in a bunch of false positive objtool warnings during the kernel build
because it isn't endian-aware.  But that's generally a rare edge case
and there haven't been any reports of anybody needing that.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/55b63eefc347f1bb28573f972d8d1adbf1f1c31d.1456962210.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 tools/lib/subcmd/Makefile |  6 ++++--
 tools/objtool/Makefile    | 17 ++++++++++-------
 2 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/tools/lib/subcmd/Makefile b/tools/lib/subcmd/Makefile
index 629cf8c..1faecb8 100644
--- a/tools/lib/subcmd/Makefile
+++ b/tools/lib/subcmd/Makefile
@@ -8,8 +8,10 @@ srctree := $(patsubst %/,%,$(dir $(srctree)))
 #$(info Determined 'srctree' to be $(srctree))
 endif
 
-CC = $(CROSS_COMPILE)gcc
-AR = $(CROSS_COMPILE)ar
+CC ?= $(CROSS_COMPILE)gcc
+LD ?= $(CROSS_COMPILE)ld
+AR ?= $(CROSS_COMPILE)ar
+
 RM = rm -f
 
 MAKEFLAGS += --no-print-directory
diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile
index c4f0713..e4a6bd5 100644
--- a/tools/objtool/Makefile
+++ b/tools/objtool/Makefile
@@ -7,13 +7,19 @@ ARCH := x86
 endif
 endif
 
+# always use the host compiler
+CC = gcc
+LD = ld
+AR = ar
+
 ifeq ($(srctree),)
 srctree := $(patsubst %/,%,$(dir $(shell pwd)))
 srctree := $(patsubst %/,%,$(dir $(srctree)))
 endif
 
-SUBCMD_SRCDIR	= $(srctree)/tools/lib/subcmd/
-LIBSUBCMD	= $(if $(OUTPUT),$(OUTPUT),$(SUBCMD_SRCDIR))libsubcmd.a
+SUBCMD_SRCDIR		= $(srctree)/tools/lib/subcmd/
+LIBSUBCMD_OUTPUT	= $(if $(OUTPUT),$(OUTPUT),$(PWD)/)
+LIBSUBCMD		= $(LIBSUBCMD_OUTPUT)libsubcmd.a
 
 OBJTOOL    := $(OUTPUT)objtool
 OBJTOOL_IN := $(OBJTOOL)-in.o
@@ -45,12 +51,9 @@ $(OBJTOOL): $(LIBSUBCMD) $(OBJTOOL_IN)
 
 
 $(LIBSUBCMD): fixdep FORCE
-	$(Q)$(MAKE) -C $(SUBCMD_SRCDIR)
-
-$(LIBSUBCMD)-clean:
-	$(Q)$(MAKE) -C $(SUBCMD_SRCDIR) clean > /dev/null
+	$(Q)$(MAKE) -C $(SUBCMD_SRCDIR) OUTPUT=$(LIBSUBCMD_OUTPUT)
 
-clean: $(LIBSUBCMD)-clean
+clean:
 	$(call QUIET_CLEAN, objtool) $(RM) $(OBJTOOL)
 	$(Q)find $(OUTPUT) -name '*.o' -delete -o -name '\.*.cmd' -delete -o -name '\.*.d' -delete
 	$(Q)$(RM) $(OUTPUT)arch/x86/insn/inat-tables.c $(OUTPUT)fixdep

Re: [PATCH] objtool: Disable stack validation when CROSS_COMPILE is used

[Sedat Dilek]

On 3/2/16, Stephen Rothwell <sfr@canb.auug.org.au> wrote:
> Hi Josh,
>
> On Tue, 1 Mar 2016 15:54:51 -0600 Josh Poimboeuf <jpoimboe@redhat.com>
> wrote:
>>
>> Changing it to use the host compiler would probably be an easy fix, but
>> that would expose a harder bug related to endianness.
>
> Just by luck, my PowerPC host is little endian :-)
>
>> How about the below workaround patch to disable objtool and warn when
>> CROSS_COMPILE is used?  If anybody complains about lack of cross-compile
>> support later, we could try to fix it then.
>
> This seems reasonable.
>
>> From a3c65947011a420743f308b698171c4209105d3f Mon Sep 17 00:00:00 2001
>> Message-Id:
>> <a3c65947011a420743f308b698171c4209105d3f.1456868910.git.jpoimboe@redhat.com>
>> From: Josh Poimboeuf <jpoimboe@redhat.com>
>> Date: Tue, 1 Mar 2016 13:35:51 -0600
>> Subject: [PATCH] objtool: Disable stack validation when CROSS_COMPILE is
>> used
>
> I have applied this to the merge of the tip tree in linux-next today
> and it compiles fine for me.  I will continue applying it until
> something better comes along or it is applied to the tip tree.
>

Does Linux next-20160303 has this patch?
On a quick view I could not find it.

- Sedat -

> Thanks for that.
> --
> Cheers,
> Stephen Rothwell
> --
> To unsubscribe from this list: send the line "unsubscribe linux-next" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>

Re: [PATCH] objtool: Disable stack validation when CROSS_COMPILE is used

[Stephen Rothwell]

Hi Sedat,

On Thu, 3 Mar 2016 08:31:57 +0100 Sedat Dilek <sedat.dilek@gmail.com> wrote:
>
> Does Linux next-20160303 has this patch?
> On a quick view I could not find it.

It is applied as part of the merge commit that merges the tip tree, so
there is not a separate commit for it.

-- 
Cheers,
Stephen Rothwell