linux-kernel - Re: [PATCH v5 4/4] x86/boot/KASLR: Limit kaslr to choosing the immovable memory

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Date:   Mon, 27 Aug 2018 15:10:32 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Chao Fan <fanc.fnst@...fujitsu.com>
Cc:     tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        keescook@...omium.org, n-horiguchi@...jp.nec.com,
        indou.takao@...fujitsu.com, caoj.fnst@...fujitsu.com,
        douly.fnst@...fujitsu.com
Subject: Re: [PATCH v5 4/4] x86/boot/KASLR: Limit kaslr to choosing the
 immovable memory

On 08/27/18 at 01:56pm, Baoquan He wrote:
> On 08/07/18 at 02:50pm, Chao Fan wrote:
> > If 'CONFIG_MEMORY_HOTREMOVE' specified and the account of immovable
> If CONFIG_MEMORY_HOTREMOVE is enabled, 
> > memory regions is not zero. Calculate the intersection between memory
> > regions from e820/efi memory table and immovable memory regions.
> > Or go on the old code.
> > 
> > Rename process_mem_region to slots_count to match slots_fetch_random,
> > and name new function as process_mem_region.
> > 
> > Signed-off-by: Chao Fan <fanc.fnst@...fujitsu.com>
> > ---
> >  arch/x86/boot/compressed/kaslr.c | 66 ++++++++++++++++++++++++++------
> >  1 file changed, 55 insertions(+), 11 deletions(-)
> > 
> > diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
> > index 720878f967a3..9c6e24a23a2d 100644
> > --- a/arch/x86/boot/compressed/kaslr.c
> > +++ b/arch/x86/boot/compressed/kaslr.c
> > @@ -635,9 +635,9 @@ static unsigned long slots_fetch_random(void)
> >  	return 0;
> >  }
> >  
> > -static void process_mem_region(struct mem_vector *entry,
> > -			       unsigned long minimum,
> > -			       unsigned long image_size)
> > +static void slots_count(struct mem_vector *entry,
> > +			unsigned long minimum,
> > +			unsigned long image_size)
> >  {
> >  	struct mem_vector region, overlap;
> >  	struct slot_area slot_area;
> > @@ -714,6 +714,56 @@ static void process_mem_region(struct mem_vector *entry,
> >  	}
> >  }
> >  
> > +static bool process_mem_region(struct mem_vector *region,
> > +			       unsigned long long minimum,
> > +			       unsigned long long image_size)
> > +{
> 
> Is it possible to take num_immovable_mem definition out from #ifdef
> CONFIG_MEMORY_HOTREMOVE block and check it here like below? This way,
> one level of indentation can be reduced in the for loop, and code is
> more readable.
> 
> 
> static bool process_mem_region(struct mem_vector *region,
> 			       unsigned long long minimum,
> 			       unsigned long long image_size)
> {
> 
> 	/*
> 	 * If no immovable memory found, or MEMORY_HOTREMOVE disabled,
> 	 * walk all the regions, so use region directely.
> 	 */
> 	if (num_immovable_mem > 0) {
Sorry, I meant if (!num_immovable_mem) {


> 		slots_count(region, minimum, image_size);
> 		
> 		if (slot_area_index == MAX_SLOT_AREA) {
> 			debug_putstr("Aborted e820/efi memmap scan (slot_areas full)!\n");
> 			return 1;
> 		}
> 		return 0;
> 	}
> 
> #ifdef CONFIG_MEMORY_HOTREMOVE
> 	for (i = 0; i < num_immovable_mem; i++) {
> 		...
> 	}
> #endif
> }
> 
> > +#ifdef CONFIG_MEMORY_HOTREMOVE
> > +	/*
> > +	 * If immovable memory found, filter the intersection between
> > +	 * immovable memory and region to slots_count.
> > +	 * Otherwise, go on old code.
> > +	 */
> > +	if (num_immovable_mem > 0) {
> > +		int i;
> > +
> > +		for (i = 0; i < num_immovable_mem; i++) {
> > +			struct mem_vector entry;
> > +			unsigned long long start, end, entry_end, region_end;
> > +
> > +			start = immovable_mem[i].start;
> > +			end = start + immovable_mem[i].size;
> > +			region_end = region->start + region->size;
> > +
> > +			entry.start = clamp(region->start, start, end);
> > +			entry_end = clamp(region_end, start, end);
> > +
> > +			if (entry.start + image_size < entry_end) {
> > +				entry.size = entry_end - entry.start;
> > +				slots_count(&entry, minimum, image_size);
> > +
> > +				if (slot_area_index == MAX_SLOT_AREA) {
> > +					debug_putstr("Aborted e820/efi memmap scan (slot_areas full)!\n");
> > +					return 1;
> > +				}
> > +			}
> > +		}
> > +		return 0;
> > +	}
> > +#endif
> > +	/*
> > +	 * If no immovable memory found, or MEMORY_HOTREMOVE disabled,
> > +	 * walk all the regions, so use region directely.
> > +	 */
> > +	slots_count(region, minimum, image_size);
> > +
> > +	if (slot_area_index == MAX_SLOT_AREA) {
> > +		debug_putstr("Aborted e820/efi memmap scan (slot_areas full)!\n");
> > +		return 1;
> > +	}
> > +	return 0;
> > +}
> > +
> >  #ifdef CONFIG_EFI
> >  /*
> >   * Returns true if mirror region found (and must have been processed
> > @@ -779,11 +829,8 @@ process_efi_entries(unsigned long minimum, unsigned long image_size)
> >  
> >  		region.start = md->phys_addr;
> >  		region.size = md->num_pages << EFI_PAGE_SHIFT;
> > -		process_mem_region(&region, minimum, image_size);
> > -		if (slot_area_index == MAX_SLOT_AREA) {
> > -			debug_putstr("Aborted EFI scan (slot_areas full)!\n");
> > +		if (process_mem_region(&region, minimum, image_size))
> >  			break;
> > -		}
> >  	}
> >  	return true;
> >  }
> > @@ -810,11 +857,8 @@ static void process_e820_entries(unsigned long minimum,
> >  			continue;
> >  		region.start = entry->addr;
> >  		region.size = entry->size;
> > -		process_mem_region(&region, minimum, image_size);
> > -		if (slot_area_index == MAX_SLOT_AREA) {
> > -			debug_putstr("Aborted e820 scan (slot_areas full)!\n");
> > +		if (process_mem_region(&region, minimum, image_size))
> >  			break;
> > -		}
> >  	}
> >  }
> >  
> > -- 
> > 2.17.1
> > 
> > 
> >