Actually these are two separate things. My callback function to fetch
shadow offset from user code is ready. This function is defined in my user
code and will be called by compiler (quite similar to how
__asan_stack_malloc_ function is implemented in gcc/asan.c).
Now in order to make sure that my users have applied this gcc patch to
their compilers, I want a have a variable __asan_gcc_patch_present which
will be defined inside gcc but will be used by user code. This way if they
build the program without applying the patch, they will get a compile error
as the reference to this variable will not be resolved.
This is how I have defined the variable. But I am not sure how I can make
this variable accessible by the user code.
id = get_identifier ("__asan_gcc_patch_present");
decl = build_decl (DECL_SOURCE_LOCATION (current_function_decl),
VAR_DECL, id, integer_type_node);
DECL_INITIAL(decl) = integer_one_node;
Please tell me what I am doing wrong.
-Harshit
On Wed, Jul 1, 2020 at 12:03 AM Martin Liška <mli...@suse.cz> wrote:
> On 6/30/20 6:52 PM, Harshit Sharma wrote:
> > Hey Martin,
> >
> > Thanks for your reply. Actually I am trying to have a callback function
> allowing gcc to fetch shadow offset from runtime code.
>
> Ah, all right!
>
> >
> > In order to make sure that my users have applied this patch before using
> asan feature, I want to define a variable in gcc (could be an integer)
> which will be referenced by the asan library in our source code. I think I
> used the wrong word 'emit' in my previous post. The variable say
> "__asan_gccpatch_present" needs to be defined in gcc and then referenced by
> our code (just like we do with functions such as __builtin_expect).
>
> Then what about adding a new ASAN variable that you will directly access
> from your source code?
> What kind of interaction do you need? Or you can add a new ASAN builtin
> (gcc/sanitizer.def), something like
> __asan_poison_stack_memory that can be used in a user code?
>
> Martin
>
> >
> >
> > Thanks,
> > Harshit
> >
> > On Tue, Jun 30, 2020 at 12:34 AM Martin Liška <mli...@suse.cz <mailto:
> mli...@suse.cz>> wrote:
> >
> > On 6/30/20 7:55 AM, Harshit Sharma via Gcc wrote:
> > > Hello,
> > > I am working on a gcc patch for asan.
> >
> > Hey.
> >
> > Good to hear, what kind of feature is that?
> >
> > > The patch is almost ready except one
> > > thing. To make sure that the user has applied this patch before
> using asan
> > > feature, I want to declare an additional variable in gcc which is
> reference
> > > by our source code so that if this patch is missing, the user
> gets an error
> > > compiling the code because the reference to this variable will
> not be
> > > resolved.
> >
> > A nice example can be emission of global variables that are used for
> -fprofile-generate:
> > see gcc/tree-profile.c:194-202.
> >
> > Let me know if it helps?
> > Martin
> >
> > >
> > > I am still new to gcc development. So, can anyone tell me how can
> I make
> > > gcc emit this variable?
> > >
> > >
> > > Thanks,
> > > Harshit
> > >
> >
>
>
