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 07:12:26 +0200
From:   damian <linux_dti@...oud.com>
To:     Baoquan He <bhe@...hat.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 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 ?

regards
Damian

> +
> +
>  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
>