[PATCH v5] x86: Disallow GOT memory access beyond its GOT slot

[H.J. Lu]

On Wed, Feb 12, 2025 at 7:22 PM Jan Beulich <jbeulich@suse.com> wrote:
>
> On 11.02.2025 22:47, H.J. Lu wrote:
> > @@ -12725,6 +12739,51 @@ imm_size (unsigned int n)
> >    return size;
> >  }
> >
> > +/* Since GOT slot size is 32 bits for i386 and 64 bits for x86-64,
> > +   disallow GOT memory access beyond its GOT slot.  */
> > +
> > +static bool
> > +check_GOT_memory (enum bfd_reloc_code_real reloc_type, unsigned int n)
> > +{
> > +  bool qword;
> > +
> > +  qword = false;
> > +  if (reloc_type == BFD_RELOC_32_PCREL)
> > +    {
> > +      if (!GOT_symbol || GOT_symbol != i.op[n].disps->X_op_symbol)
> > +     return true;
> > +      qword = true;
> > +    }
> > +  else if (reloc_type != BFD_RELOC_386_GOT32)
> > +    return true;
>
> What about BFD_RELOC_X86_64_GOT32? The 64-bit ABI simply refers to the
> 32-bit one for many reloc types, including R_X86_64_GOT32.

It can be added later.

> > +  /* Disallow AMX TILE configuration load and store instructions.  */
> > +  if (is_cpu (&i.tm, CpuAMX_TILE))
> > +    return false;
> > +
> > +  /* Disallow instructions with 6-byte and 10-byte memory access.  */
> > +  if (i.tm.operand_types[n].bitfield.fword
> > +      || i.tm.operand_types[n].bitfield.tbyte)
> > +    return false;
>
> Coming back to my concern regarding .insn: Can you explain to me how this
> (as an example) isn't going to affect .insn (using Intel syntax), when
> s_insn() has
>
>       for (j = 0; j < i.operands; ++j)
>         i.tm.operand_types[j] = i.types[j];

A testcase?

> ?
>
> Jan



-- 
H.J.