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

[Jan Beulich]

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.

> +  /* 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];

?

Jan