Commit e1dbcfaa authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by Peng Zhang
Browse files

mm: Introduce VM_SPARSE kind and vm_area_[un]map_pages(). 

mainline inclusion
from mainline-v6.9-rc1
commit e6f798225a31485e47a6e4f6aa07ee9fdf80c2cb
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I9CHG1
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e6f798225a31485e47a6e4f6aa07ee9fdf80c2cb



-------------------------------------------------

vmap/vmalloc APIs are used to map a set of pages into contiguous kernel
virtual space.

get_vm_area() with appropriate flag is used to request an area of kernel
address range. It's used for vmalloc, vmap, ioremap, xen use cases.
- vmalloc use case dominates the usage. Such vm areas have VM_ALLOC flag.
- the areas created by vmap() function should be tagged with VM_MAP.
- ioremap areas are tagged with VM_IOREMAP.

BPF would like to extend the vmap API to implement a lazily-populated
sparse, yet contiguous kernel virtual space. Introduce VM_SPARSE flag
and vm_area_map_pages(area, start_addr, count, pages) API to map a set
of pages within a given area.
It has the same sanity checks as vmap() does.
It also checks that get_vm_area() was created with VM_SPARSE flag
which identifies such areas in /proc/vmallocinfo
and returns zero pages on read through /proc/kcore.

The next commits will introduce bpf_arena which is a sparsely populated
shared memory region between bpf program and user space process. It will
map privately-managed pages into a sparse vm area with the following steps:

  // request virtual memory region during bpf prog verification
  area = get_vm_area(area_size, VM_SPARSE);

  // on demand
  vm_area_map_pages(area, kaddr, kend, pages);
  vm_area_unmap_pages(area, kaddr, kend);

  // after bpf program is detached and unloaded
  free_vm_area(area);

Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarPasha Tatashin <pasha.tatashin@soleen.com>
Link: https://lore.kernel.org/bpf/20240305030516.41519-3-alexei.starovoitov@gmail.com


(cherry picked from commit e6f798225a31485e47a6e4f6aa07ee9fdf80c2cb)
Signed-off-by: default avatarKefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: default avatarZhangPeng <zhangpeng362@huawei.com>
parent d3a24e7a

include/linux/vmalloc.h

+5 −0
Original line number Diff line number Diff line
@@ -35,6 +35,7 @@ struct iov_iter; /* in uio.h */ 
#else

#define VM_DEFER_KMEMLEAK	0

#endif

#define VM_SPARSE		0x00001000	/* sparse vm_area. not all pages are present. */



#ifdef CONFIG_EXTEND_HUGEPAGE_MAPPING

#define VM_HUGE_PAGES		0x00004000      /* vmalloc hugepage mapping only */
@@ -250,6 +251,10 @@ static inline bool is_vm_area_hugepages(const void *addr) 
}



#ifdef CONFIG_MMU

int vm_area_map_pages(struct vm_struct *area, unsigned long start,

		      unsigned long end, struct page **pages);

void vm_area_unmap_pages(struct vm_struct *area, unsigned long start,

			 unsigned long end);

void vunmap_range(unsigned long addr, unsigned long end);

static inline void set_vm_flush_reset_perms(void *addr)

{

mm/vmalloc.c

+57 −2
Original line number Diff line number Diff line
@@ -648,6 +648,58 @@ static int vmap_pages_range(unsigned long addr, unsigned long end, 
	return err;

}



static int check_sparse_vm_area(struct vm_struct *area, unsigned long start,

				unsigned long end)

{

	might_sleep();

	if (WARN_ON_ONCE(area->flags & VM_FLUSH_RESET_PERMS))

		return -EINVAL;

	if (WARN_ON_ONCE(area->flags & VM_NO_GUARD))

		return -EINVAL;

	if (WARN_ON_ONCE(!(area->flags & VM_SPARSE)))

		return -EINVAL;

	if ((end - start) >> PAGE_SHIFT > totalram_pages())

		return -E2BIG;

	if (start < (unsigned long)area->addr ||

	    (void *)end > area->addr + get_vm_area_size(area))

		return -ERANGE;

	return 0;

}



/**

 * vm_area_map_pages - map pages inside given sparse vm_area

 * @area: vm_area

 * @start: start address inside vm_area

 * @end: end address inside vm_area

 * @pages: pages to map (always PAGE_SIZE pages)

 */

int vm_area_map_pages(struct vm_struct *area, unsigned long start,

		      unsigned long end, struct page **pages)

{

	int err;



	err = check_sparse_vm_area(area, start, end);

	if (err)

		return err;



	return vmap_pages_range(start, end, PAGE_KERNEL, pages, PAGE_SHIFT);

}



/**

 * vm_area_unmap_pages - unmap pages inside given sparse vm_area

 * @area: vm_area

 * @start: start address inside vm_area

 * @end: end address inside vm_area

 */

void vm_area_unmap_pages(struct vm_struct *area, unsigned long start,

			 unsigned long end)

{

	if (check_sparse_vm_area(area, start, end))

		return;



	vunmap_range(start, end);

}



int is_vmalloc_or_module_addr(const void *x)

{

	/*
@@ -3827,9 +3879,9 @@ long vread_iter(struct iov_iter *iter, const char *addr, size_t count) 


		if (flags & VMAP_RAM)

			copied = vmap_ram_vread_iter(iter, addr, n, flags);

		else if (!(vm && (vm->flags & VM_IOREMAP)))

		else if (!(vm && (vm->flags & (VM_IOREMAP | VM_SPARSE))))

			copied = aligned_vread_iter(iter, addr, n);

		else /* IOREMAP area is treated as memory hole */

		else /* IOREMAP | SPARSE area is treated as memory hole */

			copied = zero_iter(iter, n);



		addr += copied;
@@ -4618,6 +4670,9 @@ static int s_show(struct seq_file *m, void *p) 
	if (v->flags & VM_IOREMAP)

		seq_puts(m, " ioremap");



	if (v->flags & VM_SPARSE)

		seq_puts(m, " sparse");



	if (v->flags & VM_ALLOC)

		seq_puts(m, " vmalloc");