Re: [Valgrind-users] an mmaptracer - getting the value that's going to be written

[Nicholas N. <nj...@cs...>]

On Sun, 31 Dec 2006, Tilman Sauerbeck wrote:

> I need to pass the size of the written data type, too, so now the code
> looks like this:
>
> static VG_REGPARM(2) void
> trace_store(Addr addr, SizeT size, UInt value) { ... }
>
> ...
>
> IRType arg_ty = typeOfIRExpr(bbOut->tyenv, st->Ist.Store.data);
> IExpr* addr_expr = st->Ist.Store.addr;
> IExpr* size_expr = mkIRExpr_HWord(sizeofIRType(arg_ty));
> IExpr* data_expr = st->Ist.Store.data;
>
> unsafeIRDirty_0_N(/*regparms*/ 2, "trace_store",
>                   VG_(fnptr_to_fnentry)(trace_store),
>                   mkIRExprVec_3(addr_expr, size_expr, data_expr));
>
> That created helper call is then added to the IRSB of course.
> When I run that code, I get:
>
> vex: the `impossible' happened:
>   pushArg(x86): can't handle arg of this type
> [...]
>   LibVEX called failure_exit().
> ==19009==    at 0x3800136C: report_and_quit (m_libcassert.c:140)

Args passed to C functions have to be word-sized.  data_expr will not always 
be word-sized.  I think you need to switch on the data_size and convert the 
value to word-size using the appropriate unary casts (16Uto32, etc).

> Now when I adjust the code to _not_ pass "size_expr", thus reducing the
> number of arguments to two, I get:
>
> vex: priv/host-x86/isel.c:510 (doHelperCall): Assertion `typeOfIRExpr(env->type_env, args[i]) == Ity_I32' failed.
>
> Any idea on that?

Hmm, not sure about that one, again it's complaining that one of the 
arguments isn't 32 bits, but I'm not sure why.

Nick