Commit 06c89946 authored by Baoquan He's avatar Baoquan He Committed by Andrew Morton
Browse files

mm/vmalloc.c: allow vread() to read out vm_map_ram areas 

Currently, vread can read out vmalloc areas which is associated with a
vm_struct.  While this doesn't work for areas created by vm_map_ram()
interface because it doesn't have an associated vm_struct.  Then in
vread(), these areas are all skipped.

Here, add a new function vmap_ram_vread() to read out vm_map_ram areas. 
The area created with vmap_ram_vread() interface directly can be handled
like the other normal vmap areas with aligned_vread().  While areas which
will be further subdivided and managed with vmap_block need carefully read
out page-aligned small regions and zero fill holes.

Link: https://lkml.kernel.org/r/20230206084020.174506-4-bhe@redhat.com


Reported-by: default avatarStephen Brennan <stephen.s.brennan@oracle.com>
Signed-off-by: default avatarBaoquan He <bhe@redhat.com>
Reviewed-by: default avatarLorenzo Stoakes <lstoakes@gmail.com>
Tested-by: default avatarStephen Brennan <stephen.s.brennan@oracle.com>
Cc: Dan Carpenter <error27@gmail.com>
Cc: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 869176a0

mm/vmalloc.c

+81 −7
Original line number Diff line number Diff line
@@ -3463,6 +3463,68 @@ static int aligned_vread(char *buf, char *addr, unsigned long count) 
	return copied;

}



static void vmap_ram_vread(char *buf, char *addr, int count, unsigned long flags)

{

	char *start;

	struct vmap_block *vb;

	unsigned long offset;

	unsigned int rs, re, n;



	/*

	 * If it's area created by vm_map_ram() interface directly, but

	 * not further subdividing and delegating management to vmap_block,

	 * handle it here.

	 */

	if (!(flags & VMAP_BLOCK)) {

		aligned_vread(buf, addr, count);

		return;

	}



	/*

	 * Area is split into regions and tracked with vmap_block, read out

	 * each region and zero fill the hole between regions.

	 */

	vb = xa_load(&vmap_blocks, addr_to_vb_idx((unsigned long)addr));

	if (!vb)

		goto finished;



	spin_lock(&vb->lock);

	if (bitmap_empty(vb->used_map, VMAP_BBMAP_BITS)) {

		spin_unlock(&vb->lock);

		goto finished;

	}

	for_each_set_bitrange(rs, re, vb->used_map, VMAP_BBMAP_BITS) {

		if (!count)

			break;

		start = vmap_block_vaddr(vb->va->va_start, rs);

		while (addr < start) {

			if (count == 0)

				goto unlock;

			*buf = '\0';

			buf++;

			addr++;

			count--;

		}

		/*it could start reading from the middle of used region*/

		offset = offset_in_page(addr);

		n = ((re - rs + 1) << PAGE_SHIFT) - offset;

		if (n > count)

			n = count;

		aligned_vread(buf, start+offset, n);



		buf += n;

		addr += n;

		count -= n;

	}

unlock:

	spin_unlock(&vb->lock);



finished:

	/* zero-fill the left dirty or free regions */

	if (count)

		memset(buf, 0, count);

}



/**

 * vread() - read vmalloc area in a safe way.

 * @buf:     buffer for reading data
@@ -3493,7 +3555,7 @@ long vread(char *buf, char *addr, unsigned long count) 
	struct vm_struct *vm;

	char *vaddr, *buf_start = buf;

	unsigned long buflen = count;

	unsigned long n;

	unsigned long n, size, flags;



	addr = kasan_reset_tag(addr);
@@ -3514,12 +3576,21 @@ long vread(char *buf, char *addr, unsigned long count) 
		if (!count)

			break;



		if (!va->vm)

		vm = va->vm;

		flags = va->flags & VMAP_FLAGS_MASK;

		/*

		 * VMAP_BLOCK indicates a sub-type of vm_map_ram area, need

		 * be set together with VMAP_RAM.

		 */

		WARN_ON(flags == VMAP_BLOCK);



		if (!vm && !flags)

			continue;



		vm = va->vm;

		vaddr = (char *) vm->addr;

		if (addr >= vaddr + get_vm_area_size(vm))

		vaddr = (char *) va->va_start;

		size = vm ? get_vm_area_size(vm) : va_size(va);



		if (addr >= vaddr + size)

			continue;

		while (addr < vaddr) {

			if (count == 0)
@@ -3529,10 +3600,13 @@ long vread(char *buf, char *addr, unsigned long count) 
			addr++;

			count--;

		}

		n = vaddr + get_vm_area_size(vm) - addr;

		n = vaddr + size - addr;

		if (n > count)

			n = count;

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



		if (flags & VMAP_RAM)

			vmap_ram_vread(buf, addr, n, flags);

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

			aligned_vread(buf, addr, n);

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

			memset(buf, 0, n);