linux-kernel - Re: [PATCH v3 10/19] x86, 64bit: Set ident

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Date:	Mon, 21 Mar 2016 12:48:54 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Baoquan He <bhe@...hat.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Yinghai Lu <yinghai@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>, Vivek Goyal <vgoyal@...hat.com>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	Andy Lutomirski <luto@...nel.org>, lasse.collin@...aani.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dave Young <dyoung@...hat.com>, Jiri Kosina <jkosina@...e.cz>,
	Borislav Petkov <bp@...e.de>,
	Matt Fleming <matt.fleming@...el.com>
Subject: Re: [PATCH v3 10/19] x86, 64bit: Set ident_mapping for kaslr

On Mon, Mar 21, 2016 at 12:50 AM, Baoquan He <bhe@...hat.com> wrote:
> On 03/07/16 at 03:34pm, Kees Cook wrote:
>> >  #ifdef CONFIG_EARLY_PRINTK
>> >  /* early_serial_console.c */
>> >  extern int early_serial_base;
>> > diff --git a/arch/x86/boot/compressed/misc_pgt.c b/arch/x86/boot/compressed/misc_pgt.c
>> > new file mode 100644
>> > index 0000000..954811e
>> > --- /dev/null
>> > +++ b/arch/x86/boot/compressed/misc_pgt.c
>> > @@ -0,0 +1,91 @@
>> > +#define __pa(x)  ((unsigned long)(x))
>> > +#define __va(x)  ((void *)((unsigned long)(x)))
>> > +
>> > +#include "misc.h"
>> > +
>> > +#include <asm/init.h>
>> > +#include <asm/pgtable.h>
>> > +
>> > +#include "../../mm/ident_map.c"
>> > +#include "../string.h"
>> > +
>> > +struct alloc_pgt_data {
>> > +       unsigned char *pgt_buf;
>> > +       unsigned long pgt_buf_size;
>> > +       unsigned long pgt_buf_offset;
>> > +};
>> > +
>> > +static void *alloc_pgt_page(void *context)
>> > +{
>> > +       struct alloc_pgt_data *d = (struct alloc_pgt_data *)context;
>> > +       unsigned char *p = (unsigned char *)d->pgt_buf;
>> > +
>> > +       if (d->pgt_buf_offset >= d->pgt_buf_size) {
>> > +               debug_putstr("out of pgt_buf in misc.c\n");
>>
>> This line probably isn't needed any more. Or, if it is, maybe it could
>> include more details from the context?
>
> I am trying to repost, found I missed this place.
>
> Is it OK to add more informatin in printing as below?
> if (d->pgt_buf_offset >= d->pgt_buf_size) {
>                 debug_putstr("out of pgt_buf in misc.c\n");
>                 debug_putaddr(d->pgt_buf_offset);
>                 debug_putaddr(d->pgt_buf_size);

Yeah, absolutely, that sounds perfect.

-Kees

-- 
Kees Cook
Chrome OS & Brillo Security