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Re: [PATCH v7 07/26] x86/insn-eval: Do not BUG on invalid register type

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  Re: [PATCH v7 07/26] x86/insn-eval: Do not BUG on invalid register  type Borislav Petkov <bp@suse.de> - 2017-05-29 18:40 +0200
    Re: [PATCH v7 07/26] x86/insn-eval: Do not BUG on invalid register  type Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-06-06 08:10 +0200
      Re: [PATCH v7 07/26] x86/insn-eval: Do not BUG on invalid register  type Borislav Petkov <bp@suse.de> - 2017-06-06 14:00 +0200
        Re: [PATCH v7 07/26] x86/insn-eval: Do not BUG on invalid register  type Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-06-07 02:30 +0200
          Re: [PATCH v7 07/26] x86/insn-eval: Do not BUG on invalid register  type Borislav Petkov <bp@suse.de> - 2017-06-07 14:30 +0200

#1652643 — Re: [PATCH v7 07/26] x86/insn-eval: Do not BUG on invalid register type

On Fri, May 05, 2017 at 11:17:05AM -0700, Ricardo Neri wrote:
> We are not in a critical failure path. The invalid register type is caused
> when trying to decode invalid instruction bytes from a user-space program.
> Thus, simply print an error message. To prevent this warning from being
> abused from user space programs, use the rate-limited variant of printk.
> 
> Cc: Borislav Petkov <bp@suse.de>
> Cc: Andy Lutomirski <luto@kernel.org>
> 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: 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/lib/insn-eval.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c
> index e746a6f..182e2ae 100644
> --- a/arch/x86/lib/insn-eval.c
> +++ b/arch/x86/lib/insn-eval.c
> @@ -5,6 +5,7 @@
>   */
>  #include <linux/kernel.h>
>  #include <linux/string.h>
> +#include <linux/ratelimit.h>
>  #include <asm/inat.h>
>  #include <asm/insn.h>
>  #include <asm/insn-eval.h>
> @@ -85,9 +86,8 @@ static int get_reg_offset(struct insn *insn, struct pt_regs *regs,
>  		break;
>  
>  	default:
> -		pr_err("invalid register type");
> -		BUG();
> -		break;
> +		printk_ratelimited(KERN_ERR "insn-eval: x86: invalid register type");

You can use pr_err_ratelimited() and define "insn-eval" with pr_fmt.
Look for examples in the tree.

Btw, "insn-eval" is perhaps not the right name - since we're building
an instruction decoder, maybe it should be called "insn-dec" or so. I'm
looking at those other arch/x86/lib/insn.c, arch/x86/include/asm/inat.h
things and how they're starting to morph into one decoding facility,
AFAICT.

-- 
Regards/Gruss,
    Boris.

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

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#1658374

On Mon, 2017-05-29 at 18:37 +0200, Borislav Petkov wrote:
> On Fri, May 05, 2017 at 11:17:05AM -0700, Ricardo Neri wrote:
> > We are not in a critical failure path. The invalid register type is caused
> > when trying to decode invalid instruction bytes from a user-space program.
> > Thus, simply print an error message. To prevent this warning from being
> > abused from user space programs, use the rate-limited variant of printk.
> > 
> > Cc: Borislav Petkov <bp@suse.de>
> > Cc: Andy Lutomirski <luto@kernel.org>
> > 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: 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/lib/insn-eval.c | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> > 
> > diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c
> > index e746a6f..182e2ae 100644
> > --- a/arch/x86/lib/insn-eval.c
> > +++ b/arch/x86/lib/insn-eval.c
> > @@ -5,6 +5,7 @@
> >   */
> >  #include <linux/kernel.h>
> >  #include <linux/string.h>
> > +#include <linux/ratelimit.h>
> >  #include <asm/inat.h>
> >  #include <asm/insn.h>
> >  #include <asm/insn-eval.h>
> > @@ -85,9 +86,8 @@ static int get_reg_offset(struct insn *insn, struct pt_regs *regs,
> >  		break;
> >  
> >  	default:
> > -		pr_err("invalid register type");
> > -		BUG();
> > -		break;
> > +		printk_ratelimited(KERN_ERR "insn-eval: x86: invalid register type");
> 
> You can use pr_err_ratelimited() and define "insn-eval" with pr_fmt.
> Look for examples in the tree.

Will do. I have looked at the examples.
> 
> Btw, "insn-eval" is perhaps not the right name - since we're building
> an instruction decoder, maybe it should be called "insn-dec" or so. I'm
> looking at those other arch/x86/lib/insn.c, arch/x86/include/asm/inat.h
> things and how they're starting to morph into one decoding facility,
> AFAICT.

I agree that insn-eval reads somewhat funny. I did not want to go with
insn-dec.c as insn.c, in my opinion, already decodes the instruction
(i.e., it finds prefixes, opcodes, ModRM, SIB and displacement bytes).
In insn-eval.c I simply take those decoded parameters and evaluate them
to obtain the values they contain (e.g., a specific memory location).
Perhaps, insn-resolve.c could be a better name? Or maybe isnn-operands?

Thanks and BR,
Ricardo

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#1658680

On Mon, Jun 05, 2017 at 11:06:58PM -0700, Ricardo Neri wrote:
> I agree that insn-eval reads somewhat funny. I did not want to go with
> insn-dec.c as insn.c, in my opinion, already decodes the instruction
> (i.e., it finds prefixes, opcodes, ModRM, SIB and displacement bytes).
> In insn-eval.c I simply take those decoded parameters and evaluate them
> to obtain the values they contain (e.g., a specific memory location).
> Perhaps, insn-resolve.c could be a better name? Or maybe isnn-operands?

So actually I'm gravitating towards calling all that instruction
"massaging" code with a single prefix to denote this comes from the insn
decoder/handler/whatever...

I.e.,

	"insn-decoder: x86: invalid register type"

or

	"inat: x86: invalid register type"

or something to that effect.

I mean, If we're going to grow our own - as we do, apparently - maybe it
all should be a separate entity with its proper name.

Hmm.

-- 
Regards/Gruss,
    Boris.

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

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#1659317

On Tue, 2017-06-06 at 13:58 +0200, Borislav Petkov wrote:
> On Mon, Jun 05, 2017 at 11:06:58PM -0700, Ricardo Neri wrote:
> > I agree that insn-eval reads somewhat funny. I did not want to go with
> > insn-dec.c as insn.c, in my opinion, already decodes the instruction
> > (i.e., it finds prefixes, opcodes, ModRM, SIB and displacement bytes).
> > In insn-eval.c I simply take those decoded parameters and evaluate them
> > to obtain the values they contain (e.g., a specific memory location).
> > Perhaps, insn-resolve.c could be a better name? Or maybe isnn-operands?
> 
> So actually I'm gravitating towards calling all that instruction
> "massaging" code with a single prefix to denote this comes from the insn
> decoder/handler/whatever...
> 
> I.e.,
> 
> 	"insn-decoder: x86: invalid register type"
> 
> or
> 
> 	"inat: x86: invalid register type"
> 
> or something to that effect.
> 
> I mean, If we're going to grow our own - as we do, apparently - maybe it
> all should be a separate entity with its proper name.

I see. You were more concerned about the naming of the coding artifacts
(e.g., function names, error prints, etc) than the actual filenames. I
think I have aligned with the function naming of insn.c in all the
functions that are exposed via header by using the inns_ prefix. For
static functions I don't use that prefix. Perhaps I can use the __
prefix as insn.c does.

Thanks and BR,
Ricardo

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#1659745

On Tue, Jun 06, 2017 at 05:28:52PM -0700, Ricardo Neri wrote:
> I see. You were more concerned about the naming of the coding artifacts
> (e.g., function names, error prints, etc) than the actual filenames.

Well, I'm not sure here. We could either have a generalized prefix or
put the function name in there - __func__ - for easier debuggability,
i.e., find the origin of the error message faster.

But I'm sensing that we're already well inside the bikeshed so let's not
change anything now. :)

-- 
Regards/Gruss,
    Boris.

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

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