linux-kernel - Re: [PATCH 1/2] x86/boot/KASLR: Add two functions for 1GB huge pages handling

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Date:   Thu, 17 May 2018 13:38:55 +0800
From:   Baoquan He <bhe@...hat.com>
To:     linux_dti@...oud.com
Cc:     linux-kernel@...r.kernel.org, mingo@...nel.org,
        lcapitulino@...hat.com, keescook@...omium.org, tglx@...utronix.de,
        x86@...nel.org, hpa@...or.com, fanc.fnst@...fujitsu.com,
        yasu.isimatu@...il.com, indou.takao@...fujitsu.com,
        douly.fnst@...fujitsu.com
Subject: Re: [PATCH 1/2] x86/boot/KASLR: Add two functions for 1GB huge pages
 handling

On 05/17/18 at 07:12am, damian wrote:
> On Wed, 16. May 18:05, Baoquan He wrote:
> > Functions parse_gb_huge_pages() and process_gb_huge_page() are introduced to
> > handle conflict between KASLR and huge pages, will be used in the next patch.
> > 
> > Function parse_gb_huge_pages() is used to parse kernel command-line to get
> > how many 1GB huge pages have been specified. A static global variable
> > 'max_gb_huge_pages' is added to store the number.
> > 
> > And process_gb_huge_page() is used to skip as many 1GB huge pages as possible
> > from the passed in memory region according to the specified number.
> > 
> > Signed-off-by: Baoquan He <bhe@...hat.com>
> > ---
> >  arch/x86/boot/compressed/kaslr.c | 71 ++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 71 insertions(+)
> > 
> > diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
> > index a0a50b91ecef..13bd879cdc5d 100644
> > --- a/arch/x86/boot/compressed/kaslr.c
> > +++ b/arch/x86/boot/compressed/kaslr.c
> > @@ -215,6 +215,32 @@ static void mem_avoid_memmap(char *str)
> >  		memmap_too_large = true;
> >  }
> >  
> > +/* Store the number of 1GB huge pages which user specified.*/
> > +static unsigned long max_gb_huge_pages;
> > +
> > +static int parse_gb_huge_pages(char *param, char* val)
> > +{
> > +	char *p;
> > +	u64 mem_size;
> > +	static bool gbpage_sz = false;
> > +
> > +	if (!strcmp(param, "hugepagesz")) {
> > +		p = val;
> > +		mem_size = memparse(p, &p);
> > +		if (mem_size == PUD_SIZE) {
> > +			if (gbpage_sz)
> > +				warn("Repeadly set hugeTLB page size of 1G!\n");
> > +			gbpage_sz = true;
> > +		} else
> > +			gbpage_sz = false;
> > +	} else if (!strcmp(param, "hugepages") && gbpage_sz) {
> > +		p = val;
> > +		max_gb_huge_pages = simple_strtoull(p, &p, 0);
> > +		debug_putaddr(max_gb_huge_pages);
> > +	}
> > +}
> Hello,
> 
> the return value is missing for the function or not ?

Thanks, very good catch. It should be 'static void ', no return value
since we didn't check it. Will update when repost.

> 
> > +
> > +
> >  static int handle_mem_memmap(void)
> >  {
> >  	char *args = (char *)get_cmd_line_ptr();
> > @@ -466,6 +492,51 @@ static void store_slot_info(struct mem_vector *region, unsigned long image_size)
> >  	}
> >  }
> >  
> > +/* Skip as many 1GB huge pages as possible in the passed region. */
> > +static void process_gb_huge_page(struct mem_vector *region, unsigned long image_size)
> > +{
> > +	int i = 0;
> > +	unsigned long addr, size;
> > +	struct mem_vector tmp;
> > +
> > +	if (!max_gb_huge_pages) {
> > +		store_slot_info(region, image_size);
> > +		return;
> > +	}
> > +
> > +	addr = ALIGN(region->start, PUD_SIZE);
> > +	/* If Did we raise the address above the passed in memory entry? */
> > +	if (addr < region->start + region->size)
> > +		size = region->size - (addr - region->start);
> > +
> > +	/* Check how many 1GB huge pages can be filtered out*/
> > +	while (size > PUD_SIZE && max_gb_huge_pages) {
> > +		size -= PUD_SIZE;
> > +		max_gb_huge_pages--;
> > +		i++;
> > +	}
> > +
> > +	if (!i) {
> > +		store_slot_info(region, image_size);
> > +		return;
> > +	}
> > +
> > +	/* Process the remaining regions after filtering out. */
> > +
> > +	if (addr >= region->start + image_size) {
> > +		tmp.start = region->start;
> > +		tmp.size = addr - region->start;
> > +		store_slot_info(&tmp, image_size);
> > +	}
> > +
> > +	size  = region->size - (addr - region->start) - i * PUD_SIZE;
> > +        if (size >= image_size) {
> > +		tmp.start = addr + i*PUD_SIZE;
> > +		tmp.size = size;
> > +		store_slot_info(&tmp, image_size);
> > +        }
> > +}
> > +
> >  static unsigned long slots_fetch_random(void)
> >  {
> >  	unsigned long slot;
> > -- 
> > 2.13.6
> >