Commit 9a9d1d36 authored by Andrii Nakryiko's avatar Andrii Nakryiko
Browse files

Merge branch 'mm-enforce-ioremap-address-space-and-introduce-sparse-vm_area' 

Alexei Starovoitov says:

====================
mm: Enforce ioremap address space and introduce sparse vm_area

From: Alexei Starovoitov <ast@kernel.org>

v3 -> v4
- dropped VM_XEN patch for now. It will be in the follow up.
- fixed constant as pointed out by Mike

v2 -> v3
- added Christoph's reviewed-by to patch 1
- cap commit log lines to 75 chars
- factored out common checks in patch 3 into helper
- made vm_area_unmap_pages() return void

There are various users of kernel virtual address space:
vmalloc, vmap, ioremap, xen.

- vmalloc use case dominates the usage. Such vm areas have VM_ALLOC flag
and these areas are treated differently by KASAN.

- the areas created by vmap() function should be tagged with VM_MAP
(as majority of the users do).

- ioremap areas are tagged with VM_IOREMAP and vm area start is aligned
to size of the area unlike vmalloc/vmap.

- there is also xen usage that is marked as VM_IOREMAP, but it doesn't
call ioremap_page_range() unlike all other VM_IOREMAP users.

To clean this up a bit, enforce that ioremap_page_range() checks the range
and VM_IOREMAP flag.

In addition BPF would like to reserve regions of kernel virtual address
space and populate it lazily, similar to xen use cases.
For that reason, introduce VM_SPARSE flag and vm_area_[un]map_pages()
helpers to populate this sparse area.

In the end the /proc/vmallocinfo will show
"vmalloc"
"vmap"
"ioremap"
"sparse"
categories for different kinds of address regions.

ioremap, sparse will return zero when dumped through /proc/kcore
====================

Link: https://lore.kernel.org/r/20240305030516.41519-1-alexei.starovoitov@gmail.com


Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
parents 8f50d5c4 e6f79822

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. */



/* bits [20..32] reserved for arch specific ioremap internals */
@@ -232,6 +233,10 @@ 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

+70 −2
Original line number Diff line number Diff line
@@ -307,8 +307,21 @@ static int vmap_range_noflush(unsigned long addr, unsigned long end, 
int ioremap_page_range(unsigned long addr, unsigned long end,

		phys_addr_t phys_addr, pgprot_t prot)

{

	struct vm_struct *area;

	int err;



	area = find_vm_area((void *)addr);

	if (!area || !(area->flags & VM_IOREMAP)) {

		WARN_ONCE(1, "vm_area at addr %lx is not marked as VM_IOREMAP\n", addr);

		return -EINVAL;

	}

	if (addr != (unsigned long)area->addr ||

	    (void *)end != area->addr + get_vm_area_size(area)) {

		WARN_ONCE(1, "ioremap request [%lx,%lx) doesn't match vm_area [%lx, %lx)\n",

			  addr, end, (long)area->addr,

			  (long)area->addr + get_vm_area_size(area));

		return -ERANGE;

	}

	err = vmap_range_noflush(addr, end, phys_addr, pgprot_nx(prot),

				 ioremap_max_page_shift);

	flush_cache_vmap(addr, end);
@@ -635,6 +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)

{

	/*
@@ -3809,9 +3874,9 @@ 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;
@@ -4402,6 +4467,9 @@ 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");