Re: [PATCH v9 16/29] x86/insn-eval: Add function to get default params of code segment

Ricardo Neri
2017-10-12T18:27:51Z

On Thu, 2017-10-12 at 18:31 +0200, Borislav Petkov wrote:
> On Tue, Oct 03, 2017 at 08:54:19PM -0700, Ricardo Neri wrote:
> >
> > Obtain the default values of the address and operand sizes as specified in
> > the D and L bits of the the segment descriptor selected by the register
> > CS. The function can be used for both protected and long modes.
> > For virtual-8086 mode, the default address and operand sizes are always 2
> > bytes.
> >
> > The returned parameters are encoded in a signed 8-bit data type. Auxiliar
> > macros are provided to encode and decode such values.
> >
> > Cc: Dave Hansen <dave.hansen@linux.intel.com>
> > Cc: Adam Buchbinder <adam.buchbinder@gmail.com>
> > Cc: Colin Ian King <colin.king@canonical.com>
> > Cc: Lorenzo Stoakes <lstoakes@gmail.com>
> > Cc: Qiaowei Ren <qiaowei.ren@intel.com>
> > Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
> > Cc: Masami Hiramatsu <mhiramat@kernel.org>
> > Cc: Adrian Hunter <adrian.hunter@intel.com>
> > Cc: Kees Cook <keescook@chromium.org>
> > Cc: Thomas Garnier <thgarnie@google.com>
> > Cc: Peter Zijlstra <peterz@infradead.org>
> > Cc: Borislav Petkov <bp@suse.de>
> > Cc: Dmitry Vyukov <dvyukov@google.com>
> > Cc: Ravi V. Shankar <ravi.v.shankar@intel.com>
> > Cc: x86@kernel.org
> > Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
> > ---
> >  arch/x86/include/asm/insn-eval.h |  5 ++++
> >  arch/x86/lib/insn-eval.c         | 64
> > ++++++++++++++++++++++++++++++++++++++++
> >  2 files changed, 69 insertions(+)
> Some cleanups ontop:
>
> ---
> diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c
> index 64924b7d5fff..3352b9d5164f 100644
> --- a/arch/x86/lib/insn-eval.c
> +++ b/arch/x86/lib/insn-eval.c
> @@ -614,14 +614,14 @@ static unsigned long get_seg_limit(struct pt_regs *regs,
> int seg_reg_idx)
>  }
>
>  /**
> - * insn_get_code_seg_defaults() - Obtain code segment default parameters
> + * insn_get_code_seg_params() - Obtain code segment parameters
>   * @regs: Structure with register values as seen when entering kernel
> mode
>   *
> - * Obtain the default parameters of the code segment: address and operand
> sizes.
> - * The code segment is obtained from the selector contained in the CS
> register
> - * in regs. In protected mode, the default address is determined by
> inspecting
> - * the L and D bits of the segment descriptor. In virtual-8086 mode, the
> default
> - * is always two bytes for both address and operand sizes.
> + * Obtain address and operand sizes of the code segment. It is obtained from
> the
> + * selector contained in the CS register in regs. In protected mode, the
> default
> + * address is determined by inspecting the L and D bits of the segment
> descriptor.
> + * In virtual-8086 mode, the default is always two bytes for both address and
> + * operand sizes.
>   *
>   * Returns:
>   *
> @@ -629,7 +629,7 @@ static unsigned long get_seg_limit(struct pt_regs *regs,
> int seg_reg_idx)
>   *
>   * -EINVAL on error.
>   */
> -char insn_get_code_seg_defaults(struct pt_regs *regs)
> +char insn_get_code_seg_params(struct pt_regs *regs)
>  {
>   struct desc_struct *desc;
>   short sel;
> @@ -640,7 +640,7 @@ char insn_get_code_seg_defaults(struct pt_regs *regs)
>
>   sel = get_segment_selector(regs, INAT_SEG_REG_CS);
>   if (sel < 0)
> - return -1L;
> + return sel;

Thanks! I implemente these changes along with your Improvements-by.

BR,
Ricardo