[PATCH] selftests: kvm: Fix libkvm build error

[PATCH] selftests: kvm: Fix libkvm build error

[Shuah Khan]

Fix the following build error:

libkvm.a(assert.o): relocation R_X86_64_32 against `.rodata.str1.1' can not be used when making a PIE object; recompile with -fPIC

Add -fPIC to CFLAGS to fix it.

Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
---
 tools/testing/selftests/kvm/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
index 62c591f87dab..b4a55d300e75 100644
--- a/tools/testing/selftests/kvm/Makefile
+++ b/tools/testing/selftests/kvm/Makefile
@@ -44,7 +44,7 @@ INSTALL_HDR_PATH = $(top_srcdir)/usr
 LINUX_HDR_PATH = $(INSTALL_HDR_PATH)/include/
 LINUX_TOOL_INCLUDE = $(top_srcdir)/tools/include
 CFLAGS += -Wall -Wstrict-prototypes -Wuninitialized -O2 -g -std=gnu99 \
-	-fno-stack-protector -fno-PIE -I$(LINUX_TOOL_INCLUDE) \
+	-fno-stack-protector -fPIC -fno-PIE -I$(LINUX_TOOL_INCLUDE) \
 	-I$(LINUX_HDR_PATH) -Iinclude -I$(<D) -Iinclude/$(UNAME_M) -I..
 
 no-pie-option := $(call try-run, echo 'int main() { return 0; }' | \
-- 
2.20.1

Re: [PATCH] selftests: kvm: Fix libkvm build error

[Paolo Bonzini]

On 24/09/19 22:14, Shuah Khan wrote:
> Fix the following build error:
> 
> libkvm.a(assert.o): relocation R_X86_64_32 against `.rodata.str1.1' can not be used when making a PIE object; recompile with -fPIC
> 
> Add -fPIC to CFLAGS to fix it.

This is wrong, these testcases cannot be position-independent 
executables.  Can you include the failing command line from "V=1" 
output?

The problem seems to be that these definitions are not working properly:

no-pie-option := $(call try-run, echo 'int main() { return 0; }' | \
        $(CC) -Werror $(KBUILD_CPPFLAGS) $(CC_OPTION_CFLAGS) -no-pie -x c - -o "$$TMP", -no-pie)

LDFLAGS += -pthread $(no-pie-option)

Thanks,

Paolo

> Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
> ---
>  tools/testing/selftests/kvm/Makefile | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
> index 62c591f87dab..b4a55d300e75 100644
> --- a/tools/testing/selftests/kvm/Makefile
> +++ b/tools/testing/selftests/kvm/Makefile
> @@ -44,7 +44,7 @@ INSTALL_HDR_PATH = $(top_srcdir)/usr
>  LINUX_HDR_PATH = $(INSTALL_HDR_PATH)/include/
>  LINUX_TOOL_INCLUDE = $(top_srcdir)/tools/include
>  CFLAGS += -Wall -Wstrict-prototypes -Wuninitialized -O2 -g -std=gnu99 \
> -	-fno-stack-protector -fno-PIE -I$(LINUX_TOOL_INCLUDE) \
> +	-fno-stack-protector -fPIC -fno-PIE -I$(LINUX_TOOL_INCLUDE) \
>  	-I$(LINUX_HDR_PATH) -Iinclude -I$(<D) -Iinclude/$(UNAME_M) -I..
>  
>  no-pie-option := $(call try-run, echo 'int main() { return 0; }' | \
> 

Re: [PATCH] selftests: kvm: Fix libkvm build error

[Shuah Khan]

On 9/25/19 1:48 AM, Paolo Bonzini wrote:
> On 24/09/19 22:14, Shuah Khan wrote:
>> Fix the following build error:
>>
>> libkvm.a(assert.o): relocation R_X86_64_32 against `.rodata.str1.1' can not be used when making a PIE object; recompile with -fPIC
>>
>> Add -fPIC to CFLAGS to fix it.
> 
> This is wrong, these testcases cannot be position-independent
> executables.  Can you include the failing command line from "V=1"
> output?
> 

You are right. This isn't correct.

> The problem seems to be that these definitions are not working properly:
> 
> no-pie-option := $(call try-run, echo 'int main() { return 0; }' | \
>          $(CC) -Werror $(KBUILD_CPPFLAGS) $(CC_OPTION_CFLAGS) -no-pie -x c - -o "$$TMP", -no-pie)
> 
> LDFLAGS += -pthread $(no-pie-option)
> 

Yup. That is what is happening, when I build using

"make TARGETS=kvm kselftest"

You can see this below:

gcc -Wall -Wstrict-prototypes -Wuninitialized -O2 -g -std=gnu99 
-fno-stack-protector -fno-PIE -I../../../../tools/include 
-I../../../../usr/include/ -Iinclude -Ix86_64 -Iinclude/x86_64 -I.. 
-pthread    x86_64/cr4_cpuid_sync_test.c


vs.

Running make in kvm directory:

gcc -Wall -Wstrict-prototypes -Wuninitialized -O2 -g -std=gnu99 
-fno-stack-protector -fPIC -fno-PIE -I../../../../tools/include 
-I../../../../usr/include/ -Iinclude -Ix86_64 -Iinclude/x86_64 -I.. 
-pthread  -no-pie   x86_64/cr4_cpuid_sync_test.c

I was playing with both options yesterday and totally confused myself
thinking that adding fPIC helps. It doesn't.

I am looking into this to see how we can make "make kselftest" work.
Once I figure it out, will send v2. I think for some reason in the
failing case, no-pie-option and pgste-option are null strings.

thanks,
-- Shuah