Re: [v6 PATCH 11/21] insn/eval: Incorporate segment base in address computation

Borislav Petkov
2017-04-21T14:55:33Z

On Tue, Mar 07, 2017 at 04:32:44PM -0800, Ricardo Neri wrote:
> insn_get_addr_ref returns the effective address as defined by the

Please end function names with parentheses.

> section 3.7.5.1 Vol 1 of the Intel 64 and IA-32 Architectures Software
> Developer's Manual. In order to compute the linear address, we must add
> to the effective address the segment base address as set in the segment
> descriptor. Furthermore, the segment descriptor to use depends on the
> register that is used as the base of the effective address. The effective
> base address varies depending on whether the operand is a register or a
> memory address and on whether a SiB byte is used.
>
> In most cases, the segment base address will be 0 if the USER_DS/USER32_DS
> segment is used or if segmentation is not used. However, the base address
> is not necessarily zero if a user programs defines its own segments. This
> is possible by using a local descriptor table.
>
> Since the effective address is a signed quantity, the unsigned segment
> base address saved in a separate variable and added to the final effective

".. is saved..."

> address.
>

--
Regards/Gruss,
Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
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