diff --git a/drivers/xen/Makefile b/drivers/xen/Makefile index 451e833f593175..48b154276179f0 100644 --- a/drivers/xen/Makefile +++ b/drivers/xen/Makefile @@ -41,4 +41,4 @@ obj-$(CONFIG_XEN_PVCALLS_FRONTEND) += pvcalls-front.o xen-evtchn-y := evtchn.o xen-gntdev-y := gntdev.o xen-gntalloc-y := gntalloc.o -xen-privcmd-y := privcmd.o +xen-privcmd-y := privcmd.o privcmd-buf.o diff --git a/drivers/xen/privcmd-buf.c b/drivers/xen/privcmd-buf.c new file mode 100644 index 00000000000000..df1ed37c3269eb --- /dev/null +++ b/drivers/xen/privcmd-buf.c @@ -0,0 +1,210 @@ +// SPDX-License-Identifier: GPL-2.0 OR MIT + +/****************************************************************************** + * privcmd-buf.c + * + * Mmap of hypercall buffers. + * + * Copyright (c) 2018 Juergen Gross + */ + +#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt + +#include +#include +#include +#include +#include +#include + +#include "privcmd.h" + +MODULE_LICENSE("GPL"); + +static unsigned int limit = 64; +module_param(limit, uint, 0644); +MODULE_PARM_DESC(limit, "Maximum number of pages that may be allocated by " + "the privcmd-buf device per open file"); + +struct privcmd_buf_private { + struct mutex lock; + struct list_head list; + unsigned int allocated; +}; + +struct privcmd_buf_vma_private { + struct privcmd_buf_private *file_priv; + struct list_head list; + unsigned int users; + unsigned int n_pages; + struct page *pages[]; +}; + +static int privcmd_buf_open(struct inode *ino, struct file *file) +{ + struct privcmd_buf_private *file_priv; + + file_priv = kzalloc(sizeof(*file_priv), GFP_KERNEL); + if (!file_priv) + return -ENOMEM; + + mutex_init(&file_priv->lock); + INIT_LIST_HEAD(&file_priv->list); + + file->private_data = file_priv; + + return 0; +} + +static void privcmd_buf_vmapriv_free(struct privcmd_buf_vma_private *vma_priv) +{ + unsigned int i; + + vma_priv->file_priv->allocated -= vma_priv->n_pages; + + list_del(&vma_priv->list); + + for (i = 0; i < vma_priv->n_pages; i++) + if (vma_priv->pages[i]) + __free_page(vma_priv->pages[i]); + + kfree(vma_priv); +} + +static int privcmd_buf_release(struct inode *ino, struct file *file) +{ + struct privcmd_buf_private *file_priv = file->private_data; + struct privcmd_buf_vma_private *vma_priv; + + mutex_lock(&file_priv->lock); + + while (!list_empty(&file_priv->list)) { + vma_priv = list_first_entry(&file_priv->list, + struct privcmd_buf_vma_private, + list); + privcmd_buf_vmapriv_free(vma_priv); + } + + mutex_unlock(&file_priv->lock); + + kfree(file_priv); + + return 0; +} + +static void privcmd_buf_vma_open(struct vm_area_struct *vma) +{ + struct privcmd_buf_vma_private *vma_priv = vma->vm_private_data; + + if (!vma_priv) + return; + + mutex_lock(&vma_priv->file_priv->lock); + vma_priv->users++; + mutex_unlock(&vma_priv->file_priv->lock); +} + +static void privcmd_buf_vma_close(struct vm_area_struct *vma) +{ + struct privcmd_buf_vma_private *vma_priv = vma->vm_private_data; + struct privcmd_buf_private *file_priv; + + if (!vma_priv) + return; + + file_priv = vma_priv->file_priv; + + mutex_lock(&file_priv->lock); + + vma_priv->users--; + if (!vma_priv->users) + privcmd_buf_vmapriv_free(vma_priv); + + mutex_unlock(&file_priv->lock); +} + +static vm_fault_t privcmd_buf_vma_fault(struct vm_fault *vmf) +{ + pr_debug("fault: vma=%p %lx-%lx, pgoff=%lx, uv=%p\n", + vmf->vma, vmf->vma->vm_start, vmf->vma->vm_end, + vmf->pgoff, (void *)vmf->address); + + return VM_FAULT_SIGBUS; +} + +static const struct vm_operations_struct privcmd_buf_vm_ops = { + .open = privcmd_buf_vma_open, + .close = privcmd_buf_vma_close, + .fault = privcmd_buf_vma_fault, +}; + +static int privcmd_buf_mmap(struct file *file, struct vm_area_struct *vma) +{ + struct privcmd_buf_private *file_priv = file->private_data; + struct privcmd_buf_vma_private *vma_priv; + unsigned long count = vma_pages(vma); + unsigned int i; + int ret = 0; + + if (!(vma->vm_flags & VM_SHARED) || count > limit || + file_priv->allocated + count > limit) + return -EINVAL; + + vma_priv = kzalloc(sizeof(*vma_priv) + count * sizeof(void *), + GFP_KERNEL); + if (!vma_priv) + return -ENOMEM; + + vma_priv->n_pages = count; + count = 0; + for (i = 0; i < vma_priv->n_pages; i++) { + vma_priv->pages[i] = alloc_page(GFP_KERNEL | __GFP_ZERO); + if (!vma_priv->pages[i]) + break; + count++; + } + + mutex_lock(&file_priv->lock); + + file_priv->allocated += count; + + vma_priv->file_priv = file_priv; + vma_priv->users = 1; + + vma->vm_flags |= VM_IO | VM_DONTEXPAND; + vma->vm_ops = &privcmd_buf_vm_ops; + vma->vm_private_data = vma_priv; + + list_add(&vma_priv->list, &file_priv->list); + + if (vma_priv->n_pages != count) + ret = -ENOMEM; + else + for (i = 0; i < vma_priv->n_pages; i++) { + ret = vm_insert_page(vma, vma->vm_start + i * PAGE_SIZE, + vma_priv->pages[i]); + if (ret) + break; + } + + if (ret) + privcmd_buf_vmapriv_free(vma_priv); + + mutex_unlock(&file_priv->lock); + + return ret; +} + +const struct file_operations xen_privcmdbuf_fops = { + .owner = THIS_MODULE, + .open = privcmd_buf_open, + .release = privcmd_buf_release, + .mmap = privcmd_buf_mmap, +}; +EXPORT_SYMBOL_GPL(xen_privcmdbuf_fops); + +struct miscdevice xen_privcmdbuf_dev = { + .minor = MISC_DYNAMIC_MINOR, + .name = "xen/hypercall", + .fops = &xen_privcmdbuf_fops, +}; diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c index 8ae0349d9f0ae4..7e6e682104dc4e 100644 --- a/drivers/xen/privcmd.c +++ b/drivers/xen/privcmd.c @@ -1007,12 +1007,21 @@ static int __init privcmd_init(void) pr_err("Could not register Xen privcmd device\n"); return err; } + + err = misc_register(&xen_privcmdbuf_dev); + if (err != 0) { + pr_err("Could not register Xen hypercall-buf device\n"); + misc_deregister(&privcmd_dev); + return err; + } + return 0; } static void __exit privcmd_exit(void) { misc_deregister(&privcmd_dev); + misc_deregister(&xen_privcmdbuf_dev); } module_init(privcmd_init); diff --git a/drivers/xen/privcmd.h b/drivers/xen/privcmd.h index 14facaeed36fda..0dd9f8f67ee30e 100644 --- a/drivers/xen/privcmd.h +++ b/drivers/xen/privcmd.h @@ -1,3 +1,6 @@ #include extern const struct file_operations xen_privcmd_fops; +extern const struct file_operations xen_privcmdbuf_fops; + +extern struct miscdevice xen_privcmdbuf_dev;