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SubjectRe: [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@redhat.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
> >

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