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Message-ID: <20170706012101.GH19994@x1>
Date: Thu, 6 Jul 2017 09:21:01 +0800
From: Baoquan He <bhe@...hat.com>
To: Kees Cook <keescook@...omium.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
"x86@...nel.org" <x86@...nel.org>,
"H. Peter Anvin" <hpa@...or.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...nel.org>,
Thomas Garnier <thgarnie@...gle.com>, caoj.fnst@...fujitsu.com,
izumi.taku@...fujitsu.com
Subject: Re: [PATCH v2 1/2] x86/boot/KASLR: Adapt process_e820_entry for any
type of memory entry
On 07/05/17 at 03:06pm, Kees Cook wrote:
> On Tue, Jul 4, 2017 at 1:04 AM, Baoquan He <bhe@...hat.com> wrote:
> > Now function process_e820_entry is only used to process e820 memory
> > entries. Adapt it for any type of memory entry, not just for e820.
> > Later we will use it to process efi mirror regions.
> >
> > So rename the old process_e820_entry to process_mem_region, and
> > extract and wrap the e820 specific processing code into process_e820_entry.
>
> This mixes changing the structure internals (.addr vs .start) with
> changing the processing logic (adding a wrapper). I would prefer this
> was done in several stages to make review easier:
OK, will do following below steps. Thanks!
>
> 1) lift e820 walking into a new function process_e820_entries(), and
> move TYPE_RAM logic there.
>
> 2) switch process_e820_entry() from struct boot_e820_entry to struct mem_vector.
>
> 3) rename (and adjust comments!) of process_e820_entry() into
> process_mem_region().
>
> -Kees
>
> >
> > Signed-off-by: Baoquan He <bhe@...hat.com>
> > ---
> > arch/x86/boot/compressed/kaslr.c | 60 ++++++++++++++++++++++------------------
> > 1 file changed, 33 insertions(+), 27 deletions(-)
> >
> > diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
> > index 91f27ab970ef..85c360eec4a6 100644
> > --- a/arch/x86/boot/compressed/kaslr.c
> > +++ b/arch/x86/boot/compressed/kaslr.c
> > @@ -479,35 +479,31 @@ static unsigned long slots_fetch_random(void)
> > return 0;
> > }
> >
> > -static void process_e820_entry(struct boot_e820_entry *entry,
> > +static void process_mem_region(struct mem_vector *entry,
> > unsigned long minimum,
> > unsigned long image_size)
> > {
> > struct mem_vector region, overlap;
> > struct slot_area slot_area;
> > unsigned long start_orig, end;
> > - struct boot_e820_entry cur_entry;
> > -
> > - /* Skip non-RAM entries. */
> > - if (entry->type != E820_TYPE_RAM)
> > - return;
> > + struct mem_vector cur_entry;
> >
> > /* On 32-bit, ignore entries entirely above our maximum. */
> > - if (IS_ENABLED(CONFIG_X86_32) && entry->addr >= KERNEL_IMAGE_SIZE)
> > + if (IS_ENABLED(CONFIG_X86_32) && entry->start >= KERNEL_IMAGE_SIZE)
> > return;
> >
> > /* Ignore entries entirely below our minimum. */
> > - if (entry->addr + entry->size < minimum)
> > + if (entry->start + entry->size < minimum)
> > return;
> >
> > /* Ignore entries above memory limit */
> > - end = min(entry->size + entry->addr, mem_limit);
> > - if (entry->addr >= end)
> > + end = min(entry->size + entry->start, mem_limit);
> > + if (entry->start >= end)
> > return;
> > - cur_entry.addr = entry->addr;
> > - cur_entry.size = end - entry->addr;
> > + cur_entry.start = entry->start;
> > + cur_entry.size = end - entry->start;
> >
> > - region.start = cur_entry.addr;
> > + region.start = cur_entry.start;
> > region.size = cur_entry.size;
> >
> > /* Give up if slot area array is full. */
> > @@ -522,7 +518,7 @@ static void process_e820_entry(struct boot_e820_entry *entry,
> > region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN);
> >
> > /* Did we raise the address above this e820 region? */
> > - if (region.start > cur_entry.addr + cur_entry.size)
> > + if (region.start > cur_entry.start + cur_entry.size)
> > return;
> >
> > /* Reduce size by any delta from the original address. */
> > @@ -562,12 +558,31 @@ static void process_e820_entry(struct boot_e820_entry *entry,
> > }
> > }
> >
> > -static unsigned long find_random_phys_addr(unsigned long minimum,
> > - unsigned long image_size)
> > +static void process_e820_entry(unsigned long minimum, unsigned long image_size)
> > {
> > int i;
> > - unsigned long addr;
> > + struct mem_vector region;
> > + struct boot_e820_entry *entry;
> > +
> > + /* Verify potential e820 positions, appending to slots list. */
> > + for (i = 0; i < boot_params->e820_entries; i++) {
> > + entry = &boot_params->e820_table[i];
> > + /* Skip non-RAM entries. */
> > + if (entry->type != E820_TYPE_RAM)
> > + continue;
> > + region.start = entry->addr;
> > + region.size = entry->size;
> > + process_mem_region(®ion, minimum, image_size);
> > + if (slot_area_index == MAX_SLOT_AREA) {
> > + debug_putstr("Aborted e820 scan (slot_areas full)!\n");
> > + break;
> > + }
> > + }
> > +}
> >
> > +static unsigned long find_random_phys_addr(unsigned long minimum,
> > + unsigned long image_size)
> > +{
> > /* Check if we had too many memmaps. */
> > if (memmap_too_large) {
> > debug_putstr("Aborted e820 scan (more than 4 memmap= args)!\n");
> > @@ -577,16 +592,7 @@ static unsigned long find_random_phys_addr(unsigned long minimum,
> > /* Make sure minimum is aligned. */
> > minimum = ALIGN(minimum, CONFIG_PHYSICAL_ALIGN);
> >
> > - /* Verify potential e820 positions, appending to slots list. */
> > - for (i = 0; i < boot_params->e820_entries; i++) {
> > - process_e820_entry(&boot_params->e820_table[i], minimum,
> > - image_size);
> > - if (slot_area_index == MAX_SLOT_AREA) {
> > - debug_putstr("Aborted e820 scan (slot_areas full)!\n");
> > - break;
> > - }
> > - }
> > -
> > + process_e820_entry(minimum, image_size);
> > return slots_fetch_random();
> > }
> >
> > --
> > 2.5.5
> >
>
>
>
> --
> Kees Cook
> Pixel Security
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