Commit ab520be8 authored by Paul Durrant's avatar Paul Durrant Committed by Boris Ostrovsky
Browse files

xen/privcmd: Add IOCTL_PRIVCMD_DM_OP 

Recently a new dm_op[1] hypercall was added to Xen to provide a mechanism
for restricting device emulators (such as QEMU) to a limited set of
hypervisor operations, and being able to audit those operations in the
kernel of the domain in which they run.

This patch adds IOCTL_PRIVCMD_DM_OP as gateway for __HYPERVISOR_dm_op.

NOTE: There is no requirement for user-space code to bounce data through
      locked memory buffers (as with IOCTL_PRIVCMD_HYPERCALL) since
      privcmd has enough information to lock the original buffers
      directly.

[1] http://xenbits.xen.org/gitweb/?p=xen.git;a=commit;h=524a98c2



Signed-off-by: default avatarPaul Durrant <paul.durrant@citrix.com>
Acked-by: default avatarStefano Stabellini <sstabellini@kernel.org>
Signed-off-by: default avatarBoris Ostrovsky <boris.ostrovsky@oracle.com>
parent dc9eab6f

arch/arm/xen/enlighten.c

+1 −0
Original line number Diff line number Diff line
@@ -457,4 +457,5 @@ EXPORT_SYMBOL_GPL(HYPERVISOR_tmem_op); 
EXPORT_SYMBOL_GPL(HYPERVISOR_platform_op);

EXPORT_SYMBOL_GPL(HYPERVISOR_multicall);

EXPORT_SYMBOL_GPL(HYPERVISOR_vm_assist);

EXPORT_SYMBOL_GPL(HYPERVISOR_dm_op);

EXPORT_SYMBOL_GPL(privcmd_call);

arch/arm/xen/hypercall.S

+1 −0
Original line number Diff line number Diff line
@@ -92,6 +92,7 @@ HYPERCALL1(tmem_op); 
HYPERCALL1(platform_op_raw);

HYPERCALL2(multicall);

HYPERCALL2(vm_assist);

HYPERCALL3(dm_op);



ENTRY(privcmd_call)

	stmdb sp!, {r4}

arch/arm64/xen/hypercall.S

+1 −0
Original line number Diff line number Diff line
@@ -84,6 +84,7 @@ HYPERCALL1(tmem_op); 
HYPERCALL1(platform_op_raw);

HYPERCALL2(multicall);

HYPERCALL2(vm_assist);

HYPERCALL3(dm_op);



ENTRY(privcmd_call)

	mov x16, x0

arch/x86/include/asm/xen/hypercall.h

+7 −0
Original line number Diff line number Diff line
@@ -472,6 +472,13 @@ HYPERVISOR_xenpmu_op(unsigned int op, void *arg) 
	return _hypercall2(int, xenpmu_op, op, arg);

}



static inline int

HYPERVISOR_dm_op(

	domid_t dom, unsigned int nr_bufs, void *bufs)

{

	return _hypercall3(int, dm_op, dom, nr_bufs, bufs);

}



static inline void

MULTI_fpu_taskswitch(struct multicall_entry *mcl, int set)

{

drivers/xen/privcmd.c

+139 −0
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@ 
#include <linux/pagemap.h>

#include <linux/seq_file.h>

#include <linux/miscdevice.h>

#include <linux/moduleparam.h>



#include <asm/pgalloc.h>

#include <asm/pgtable.h>
@@ -32,6 +33,7 @@ 
#include <xen/xen.h>

#include <xen/privcmd.h>

#include <xen/interface/xen.h>

#include <xen/interface/hvm/dm_op.h>

#include <xen/features.h>

#include <xen/page.h>

#include <xen/xen-ops.h>
@@ -43,6 +45,17 @@ MODULE_LICENSE("GPL"); 


#define PRIV_VMA_LOCKED ((void *)1)



static unsigned int privcmd_dm_op_max_num = 16;

module_param_named(dm_op_max_nr_bufs, privcmd_dm_op_max_num, uint, 0644);

MODULE_PARM_DESC(dm_op_max_nr_bufs,

		 "Maximum number of buffers per dm_op hypercall");



static unsigned int privcmd_dm_op_buf_max_size = 4096;

module_param_named(dm_op_buf_max_size, privcmd_dm_op_buf_max_size, uint,

		   0644);

MODULE_PARM_DESC(dm_op_buf_max_size,

		 "Maximum size of a dm_op hypercall buffer");



static int privcmd_vma_range_is_mapped(

               struct vm_area_struct *vma,

               unsigned long addr,
@@ -548,6 +561,128 @@ out_unlock: 
	goto out;

}



static int lock_pages(

	struct privcmd_dm_op_buf kbufs[], unsigned int num,

	struct page *pages[], unsigned int nr_pages)

{

	unsigned int i;



	for (i = 0; i < num; i++) {

		unsigned int requested;

		int pinned;



		requested = DIV_ROUND_UP(

			offset_in_page(kbufs[i].uptr) + kbufs[i].size,

			PAGE_SIZE);

		if (requested > nr_pages)

			return -ENOSPC;



		pinned = get_user_pages_fast(

			(unsigned long) kbufs[i].uptr,

			requested, FOLL_WRITE, pages);

		if (pinned < 0)

			return pinned;



		nr_pages -= pinned;

		pages += pinned;

	}



	return 0;

}



static void unlock_pages(struct page *pages[], unsigned int nr_pages)

{

	unsigned int i;



	if (!pages)

		return;



	for (i = 0; i < nr_pages; i++) {

		if (pages[i])

			put_page(pages[i]);

	}

}



static long privcmd_ioctl_dm_op(void __user *udata)

{

	struct privcmd_dm_op kdata;

	struct privcmd_dm_op_buf *kbufs;

	unsigned int nr_pages = 0;

	struct page **pages = NULL;

	struct xen_dm_op_buf *xbufs = NULL;

	unsigned int i;

	long rc;



	if (copy_from_user(&kdata, udata, sizeof(kdata)))

		return -EFAULT;



	if (kdata.num == 0)

		return 0;



	if (kdata.num > privcmd_dm_op_max_num)

		return -E2BIG;



	kbufs = kcalloc(kdata.num, sizeof(*kbufs), GFP_KERNEL);

	if (!kbufs)

		return -ENOMEM;



	if (copy_from_user(kbufs, kdata.ubufs,

			   sizeof(*kbufs) * kdata.num)) {

		rc = -EFAULT;

		goto out;

	}



	for (i = 0; i < kdata.num; i++) {

		if (kbufs[i].size > privcmd_dm_op_buf_max_size) {

			rc = -E2BIG;

			goto out;

		}



		if (!access_ok(VERIFY_WRITE, kbufs[i].uptr,

			       kbufs[i].size)) {

			rc = -EFAULT;

			goto out;

		}



		nr_pages += DIV_ROUND_UP(

			offset_in_page(kbufs[i].uptr) + kbufs[i].size,

			PAGE_SIZE);

	}



	pages = kcalloc(nr_pages, sizeof(*pages), GFP_KERNEL);

	if (!pages) {

		rc = -ENOMEM;

		goto out;

	}



	xbufs = kcalloc(kdata.num, sizeof(*xbufs), GFP_KERNEL);

	if (!xbufs) {

		rc = -ENOMEM;

		goto out;

	}



	rc = lock_pages(kbufs, kdata.num, pages, nr_pages);

	if (rc)

		goto out;



	for (i = 0; i < kdata.num; i++) {

		set_xen_guest_handle(xbufs[i].h, kbufs[i].uptr);

		xbufs[i].size = kbufs[i].size;

	}



	xen_preemptible_hcall_begin();

	rc = HYPERVISOR_dm_op(kdata.dom, kdata.num, xbufs);

	xen_preemptible_hcall_end();



out:

	unlock_pages(pages, nr_pages);

	kfree(xbufs);

	kfree(pages);

	kfree(kbufs);



	return rc;

}



static long privcmd_ioctl(struct file *file,

			  unsigned int cmd, unsigned long data)

{
@@ -571,6 +706,10 @@ static long privcmd_ioctl(struct file *file, 
		ret = privcmd_ioctl_mmap_batch(udata, 2);

		break;



	case IOCTL_PRIVCMD_DM_OP:

		ret = privcmd_ioctl_dm_op(udata);

		break;



	default:

		break;

	}

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