Re: [LLVMdev] Compile a linux kernel with LLVM?

[ymxia at nudt.edu.cn]

Dear John,

I am glad to receive your letter. Your advices are very helpful for me. Thank you very much.
 
Kindly excuse my not replying to your favour of the 7th July until today.

I want to analysis security of large source code, such as buffer overrun, security model, etc.

I have done some primitive experiments for that, and wich show the intermediate language of 

LLVM is very effective, and other supports, such as def-use chain, call graph, loopinfo, alias 

analysis, etc., are powerful. I like LLVM!

Without question, I will meet many problems when I study LLVM. Please prepare your favours. :)

-Xia

John Criswell <criswell at cs.uiuc.edu>:

> ymxia at nudt.edu.cn wrote:
> > Hi,
> >
> >   I want to check some properties of linux kernel with llvm, but I don't k
> now how to compile a
> >
> > linux kernel to an llvm's .bc file. I have let llvm's gcc front-end ignore
>  inline assembly by
> >
> > modifying cfrontend/src/gcc/llvm-expand.c, and replace CC/as/ar in the Mak
> efile of the kernel
> >
> > with llvm-gcc/llvm-as/llvm-ar. However, the linux's "make" reports errors:
>  "File format not
> >
> > recognized" and "not ELF".
> >
> >   Some people did this before?
>
> I am currently working on a similar project (compiling Linux with the
> LLVM compiler).  However, my work modifies the inline assembly in the
> kernel to use LLVM intrinsics (most of which have not been added to LLVM
> yet).
>
> First, make sure you change LD in the master Makefile to use gccld
> (instead of the native linker, ld).  The final linking of vmlinux uses
> ld directly (which doesn't understand LLVM bytecode files).  This needs
> to be changed to use gccld.
>
> Second, you may need to adjust the rules for the vmlinux target a little
> bit.  The gccld program will, given the -o <file> option, will create
> file and file.bc, where file.bc is the actual bytecode file and file is
> a script that runs lli on file.bc.
>
> Third, if all you want to do is do program analysis on Linux, then all
> you need to build is vmlinux.bc.  It won't be necessary to build bzImage.
>
> If the problem continues, just use gmake/make without the -s option so
> that you can see what programs it is running.  Chances are good that the
> error is caused by running a native tool on an LLVM bytecode file;
> looking at what gmake is doing will quickly tell you what program is
> being run.
>
> Just out of curiousity, what sort of analysis do you want to do on vmlinux?
>
> -- John T.
>
> >
> > Thanks.
> >
> > _______________________________________________
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> > LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> > http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev
>
>
> --
> John T. Criswell
> Research Programmer
> University of Illinois at Urbana-Champaign
> "It's today!" said Piglet. "My favorite day," said Pooh.
>
>