Re: [FuSa SIG] Static code analysis. some questions.

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>]

On Tue, 28 Jan 2020, Francesco Brancati wrote:
> Dear Stefano,
> 
> I have a couple of question for you from the team working on static code
> analysis. please see below.

Hi Francesco,

Sorry for the late reply.

 
> - with the approach presented during last meeting we obtained intermediate
> results but for the analysis few decisions were done by us that needs
> confirmations and few errors/warning raised  by the understand tool:
> 1) since the file list provided had some errors (rows with double entries and
> file not identified in  the path specified) we tried to solve them as reported
> in the file list attached: could you confirm that this is a valid list for
> headers+source code files for Xen 4.13.0 tinyconfig project ? (see
> fileListRes.txt)

Sorry about the errors, and yes, your list looks valid, except for a
couple of missing headers, see below.


> 2) the tool raised the following warnings during the analysis with respect to
> .h files that we were unable to solve manually: could you please help us?

In regards to the warnings, they affect the following headers:

  asm/asm-offsets.h
  asm-arm/vpl011.h
  xen/compile.h
  asm/spec_ctrl.h
  asm/i387.h
  asm/xstate.h

Let's go over them one by one:

1) asm/asm-offsets.h
It looks like this is missing from your file list, you should have:
  
  include/asm/asm-offsets.h

2) asm-arm/vpl011.h
This one is present in your file list as include/asm-arm/vpl011.h, I
don't know why the tool is not able to find it. If you look at xen.git,
the file is certainly there:

http://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=xen/include/asm-arm/vpl011.h;h=e6c7ab738194a5759e796aa3b0e30be4133340f8;hb=a2e84d8e42c9e878fff17b738d8e5c5d83888f31

3) xen/compile.h
This one is missing from your file list, you should add:

  include/xen/compile.h

4) asm/spec_ctrl.h 
This one is interesting because it shouldn't be included at all. This is
a x86 header file: xen/include/asm-x86/spec_ctrl.h. The C file that is
supposed to include it is xen/common/efi/boot.c:

http://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=xen/common/efi/boot.c;h=3f1c330afec2c675636b73b00ee89c1734230d47;hb=a2e84d8e42c9e878fff17b738d8e5c5d83888f31

If you look at line 1410, you'll see that the include is actually right
after #ifndef CONFIG_ARM:

http://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=xen/common/efi/boot.c;h=3f1c330afec2c675636b73b00ee89c1734230d47;hb=a2e84d8e42c9e878fff17b738d8e5c5d83888f31#l1410

So this seems to be a genuine error in the tool that doesn't pick up the
meaning of #ifndef CONFIG_ARM?


5) asm/i387.h
Same as 4), the file is a x86 header file: xen/include/asm-x86/i387.h
It is supposed to be included by xen/common/efi/runtime.c, but the
#include is done right after a #ifndef CONFIG_ARM, see:

http://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=xen/common/efi/runtime.c;h=8c2ece468de97c7448b0ef0cad8b440de8cbae51;hb=a2e84d8e42c9e878fff17b738d8e5c5d83888f31#l32


6) asm/xstate.h
This is again like 4) and 5), probably an error by the tool. xstate.h is
a x86 header: xen/include/asm-x86/xstate.h, it is included by
xen/common/efi/runtime.c after a #ifndef CONFIG_ARM, give a look at the
same link as before.



> 3) in addition to this, we would like to try a new functionality of the
> Understand tool that should allow to automatically trace the building process
> in order to detect all the files (.c and .h) used for a certain build and
> parameters, allowing to analyze all and only the needed file with preprocessor
> config.

Sounds very useful


> in order to do this, we would like to have advices on the build process.
> you gave us as reference the following process:
> ---
> export XEN_TARGET_ARCH=arm64
> export CROSS_COMPILE=/path/to/cross-compiler
> cd xen/
> cp arch/arm/configs/tiny64.conf .config
> make
> (press Enter a few times)
> ---
> the question is: is it ok with Xen 4.13.0?

Yes, it is OK.


> Which is the cross-compiler for arm64 that you use?

Typically, I just use the one pre-built by Linaro:

https://releases.linaro.org/components/toolchain/binaries/latest-7/aarch64-linux-gnu/gcc-linaro-7.5.0-2019.12-x86_64_aarch64-linux-gnu.tar.xz

Unpack the tarball, lets say you end up with:

/local/gcc-linaro-7.5.0-2019.12-x86_64_aarch64-linux-gnu

Then you need to set CROSS_COMPILE as follows:

export 
CROSS_COMPILE=/local/gcc-linaro-7.5.0-2019.12-x86_64_aarch64-linux-gnu/bin/aarch64-linux-gnu-

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