blob: 7aaa3652e31d15022a9d956944cd14c099ea0740 [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0
/*
* Device driver to expose SGX enclave memory to KVM guests.
*
* Copyright(c) 2021 Intel Corporation.
*/
#include <linux/miscdevice.h>
#include <linux/mm.h>
#include <linux/mman.h>
#include <linux/sched/mm.h>
#include <linux/sched/signal.h>
#include <linux/slab.h>
#include <linux/xarray.h>
#include <asm/sgx.h>
#include <uapi/asm/sgx.h>
#include "encls.h"
#include "sgx.h"
struct sgx_vepc {
struct xarray page_array;
struct mutex lock;
};
/*
* Temporary SECS pages that cannot be EREMOVE'd due to having child in other
* virtual EPC instances, and the lock to protect it.
*/
static struct mutex zombie_secs_pages_lock;
static struct list_head zombie_secs_pages;
static int __sgx_vepc_fault(struct sgx_vepc *vepc,
struct vm_area_struct *vma, unsigned long addr)
{
struct sgx_epc_page *epc_page;
unsigned long index, pfn;
int ret;
WARN_ON(!mutex_is_locked(&vepc->lock));
/* Calculate index of EPC page in virtual EPC's page_array */
index = vma->vm_pgoff + PFN_DOWN(addr - vma->vm_start);
epc_page = xa_load(&vepc->page_array, index);
if (epc_page)
return 0;
epc_page = sgx_alloc_epc_page(vepc, false);
if (IS_ERR(epc_page))
return PTR_ERR(epc_page);
ret = xa_err(xa_store(&vepc->page_array, index, epc_page, GFP_KERNEL));
if (ret)
goto err_free;
pfn = PFN_DOWN(sgx_get_epc_phys_addr(epc_page));
ret = vmf_insert_pfn(vma, addr, pfn);
if (ret != VM_FAULT_NOPAGE) {
ret = -EFAULT;
goto err_delete;
}
return 0;
err_delete:
xa_erase(&vepc->page_array, index);
err_free:
sgx_free_epc_page(epc_page);
return ret;
}
static vm_fault_t sgx_vepc_fault(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
struct sgx_vepc *vepc = vma->vm_private_data;
int ret;
mutex_lock(&vepc->lock);
ret = __sgx_vepc_fault(vepc, vma, vmf->address);
mutex_unlock(&vepc->lock);
if (!ret)
return VM_FAULT_NOPAGE;
if (ret == -EBUSY && (vmf->flags & FAULT_FLAG_ALLOW_RETRY)) {
mmap_read_unlock(vma->vm_mm);
return VM_FAULT_RETRY;
}
return VM_FAULT_SIGBUS;
}
static const struct vm_operations_struct sgx_vepc_vm_ops = {
.fault = sgx_vepc_fault,
};
static int sgx_vepc_mmap(struct file *file, struct vm_area_struct *vma)
{
struct sgx_vepc *vepc = file->private_data;
if (!(vma->vm_flags & VM_SHARED))
return -EINVAL;
vma->vm_ops = &sgx_vepc_vm_ops;
/* Don't copy VMA in fork() */
vm_flags_set(vma, VM_PFNMAP | VM_IO | VM_DONTDUMP | VM_DONTCOPY);
vma->vm_private_data = vepc;
return 0;
}
static int sgx_vepc_remove_page(struct sgx_epc_page *epc_page)
{
/*
* Take a previously guest-owned EPC page and return it to the
* general EPC page pool.
*
* Guests can not be trusted to have left this page in a good
* state, so run EREMOVE on the page unconditionally. In the
* case that a guest properly EREMOVE'd this page, a superfluous
* EREMOVE is harmless.
*/
return __eremove(sgx_get_epc_virt_addr(epc_page));
}
static int sgx_vepc_free_page(struct sgx_epc_page *epc_page)
{
int ret = sgx_vepc_remove_page(epc_page);
if (ret) {
/*
* Only SGX_CHILD_PRESENT is expected, which is because of
* EREMOVE'ing an SECS still with child, in which case it can
* be handled by EREMOVE'ing the SECS again after all pages in
* virtual EPC have been EREMOVE'd. See comments in below in
* sgx_vepc_release().
*
* The user of virtual EPC (KVM) needs to guarantee there's no
* logical processor is still running in the enclave in guest,
* otherwise EREMOVE will get SGX_ENCLAVE_ACT which cannot be
* handled here.
*/
WARN_ONCE(ret != SGX_CHILD_PRESENT, EREMOVE_ERROR_MESSAGE,
ret, ret);
return ret;
}
sgx_free_epc_page(epc_page);
return 0;
}
static long sgx_vepc_remove_all(struct sgx_vepc *vepc)
{
struct sgx_epc_page *entry;
unsigned long index;
long failures = 0;
xa_for_each(&vepc->page_array, index, entry) {
int ret = sgx_vepc_remove_page(entry);
if (ret) {
if (ret == SGX_CHILD_PRESENT) {
/* The page is a SECS, userspace will retry. */
failures++;
} else {
/*
* Report errors due to #GP or SGX_ENCLAVE_ACT; do not
* WARN, as userspace can induce said failures by
* calling the ioctl concurrently on multiple vEPCs or
* while one or more CPUs is running the enclave. Only
* a #PF on EREMOVE indicates a kernel/hardware issue.
*/
WARN_ON_ONCE(encls_faulted(ret) &&
ENCLS_TRAPNR(ret) != X86_TRAP_GP);
return -EBUSY;
}
}
cond_resched();
}
/*
* Return the number of SECS pages that failed to be removed, so
* userspace knows that it has to retry.
*/
return failures;
}
static int sgx_vepc_release(struct inode *inode, struct file *file)
{
struct sgx_vepc *vepc = file->private_data;
struct sgx_epc_page *epc_page, *tmp, *entry;
unsigned long index;
LIST_HEAD(secs_pages);
xa_for_each(&vepc->page_array, index, entry) {
/*
* Remove all normal, child pages. sgx_vepc_free_page()
* will fail if EREMOVE fails, but this is OK and expected on
* SECS pages. Those can only be EREMOVE'd *after* all their
* child pages. Retries below will clean them up.
*/
if (sgx_vepc_free_page(entry))
continue;
xa_erase(&vepc->page_array, index);
cond_resched();
}
/*
* Retry EREMOVE'ing pages. This will clean up any SECS pages that
* only had children in this 'epc' area.
*/
xa_for_each(&vepc->page_array, index, entry) {
epc_page = entry;
/*
* An EREMOVE failure here means that the SECS page still
* has children. But, since all children in this 'sgx_vepc'
* have been removed, the SECS page must have a child on
* another instance.
*/
if (sgx_vepc_free_page(epc_page))
list_add_tail(&epc_page->list, &secs_pages);
xa_erase(&vepc->page_array, index);
cond_resched();
}
/*
* SECS pages are "pinned" by child pages, and "unpinned" once all
* children have been EREMOVE'd. A child page in this instance
* may have pinned an SECS page encountered in an earlier release(),
* creating a zombie. Since some children were EREMOVE'd above,
* try to EREMOVE all zombies in the hopes that one was unpinned.
*/
mutex_lock(&zombie_secs_pages_lock);
list_for_each_entry_safe(epc_page, tmp, &zombie_secs_pages, list) {
/*
* Speculatively remove the page from the list of zombies,
* if the page is successfully EREMOVE'd it will be added to
* the list of free pages. If EREMOVE fails, throw the page
* on the local list, which will be spliced on at the end.
*/
list_del(&epc_page->list);
if (sgx_vepc_free_page(epc_page))
list_add_tail(&epc_page->list, &secs_pages);
cond_resched();
}
if (!list_empty(&secs_pages))
list_splice_tail(&secs_pages, &zombie_secs_pages);
mutex_unlock(&zombie_secs_pages_lock);
xa_destroy(&vepc->page_array);
kfree(vepc);
return 0;
}
static int sgx_vepc_open(struct inode *inode, struct file *file)
{
struct sgx_vepc *vepc;
vepc = kzalloc(sizeof(struct sgx_vepc), GFP_KERNEL);
if (!vepc)
return -ENOMEM;
mutex_init(&vepc->lock);
xa_init(&vepc->page_array);
file->private_data = vepc;
return 0;
}
static long sgx_vepc_ioctl(struct file *file,
unsigned int cmd, unsigned long arg)
{
struct sgx_vepc *vepc = file->private_data;
switch (cmd) {
case SGX_IOC_VEPC_REMOVE_ALL:
if (arg)
return -EINVAL;
return sgx_vepc_remove_all(vepc);
default:
return -ENOTTY;
}
}
static const struct file_operations sgx_vepc_fops = {
.owner = THIS_MODULE,
.open = sgx_vepc_open,
.unlocked_ioctl = sgx_vepc_ioctl,
.compat_ioctl = sgx_vepc_ioctl,
.release = sgx_vepc_release,
.mmap = sgx_vepc_mmap,
};
static struct miscdevice sgx_vepc_dev = {
.minor = MISC_DYNAMIC_MINOR,
.name = "sgx_vepc",
.nodename = "sgx_vepc",
.fops = &sgx_vepc_fops,
};
int __init sgx_vepc_init(void)
{
/* SGX virtualization requires KVM to work */
if (!cpu_feature_enabled(X86_FEATURE_VMX))
return -ENODEV;
INIT_LIST_HEAD(&zombie_secs_pages);
mutex_init(&zombie_secs_pages_lock);
return misc_register(&sgx_vepc_dev);
}
/**
* sgx_virt_ecreate() - Run ECREATE on behalf of guest
* @pageinfo: Pointer to PAGEINFO structure
* @secs: Userspace pointer to SECS page
* @trapnr: trap number injected to guest in case of ECREATE error
*
* Run ECREATE on behalf of guest after KVM traps ECREATE for the purpose
* of enforcing policies of guest's enclaves, and return the trap number
* which should be injected to guest in case of any ECREATE error.
*
* Return:
* - 0: ECREATE was successful.
* - <0: on error.
*/
int sgx_virt_ecreate(struct sgx_pageinfo *pageinfo, void __user *secs,
int *trapnr)
{
int ret;
/*
* @secs is an untrusted, userspace-provided address. It comes from
* KVM and is assumed to be a valid pointer which points somewhere in
* userspace. This can fault and call SGX or other fault handlers when
* userspace mapping @secs doesn't exist.
*
* Add a WARN() to make sure @secs is already valid userspace pointer
* from caller (KVM), who should already have handled invalid pointer
* case (for instance, made by malicious guest). All other checks,
* such as alignment of @secs, are deferred to ENCLS itself.
*/
if (WARN_ON_ONCE(!access_ok(secs, PAGE_SIZE)))
return -EINVAL;
__uaccess_begin();
ret = __ecreate(pageinfo, (void *)secs);
__uaccess_end();
if (encls_faulted(ret)) {
*trapnr = ENCLS_TRAPNR(ret);
return -EFAULT;
}
/* ECREATE doesn't return an error code, it faults or succeeds. */
WARN_ON_ONCE(ret);
return 0;
}
EXPORT_SYMBOL_GPL(sgx_virt_ecreate);
static int __sgx_virt_einit(void __user *sigstruct, void __user *token,
void __user *secs)
{
int ret;
/*
* Make sure all userspace pointers from caller (KVM) are valid.
* All other checks deferred to ENCLS itself. Also see comment
* for @secs in sgx_virt_ecreate().
*/
#define SGX_EINITTOKEN_SIZE 304
if (WARN_ON_ONCE(!access_ok(sigstruct, sizeof(struct sgx_sigstruct)) ||
!access_ok(token, SGX_EINITTOKEN_SIZE) ||
!access_ok(secs, PAGE_SIZE)))
return -EINVAL;
__uaccess_begin();
ret = __einit((void *)sigstruct, (void *)token, (void *)secs);
__uaccess_end();
return ret;
}
/**
* sgx_virt_einit() - Run EINIT on behalf of guest
* @sigstruct: Userspace pointer to SIGSTRUCT structure
* @token: Userspace pointer to EINITTOKEN structure
* @secs: Userspace pointer to SECS page
* @lepubkeyhash: Pointer to guest's *virtual* SGX_LEPUBKEYHASH MSR values
* @trapnr: trap number injected to guest in case of EINIT error
*
* Run EINIT on behalf of guest after KVM traps EINIT. If SGX_LC is available
* in host, SGX driver may rewrite the hardware values at wish, therefore KVM
* needs to update hardware values to guest's virtual MSR values in order to
* ensure EINIT is executed with expected hardware values.
*
* Return:
* - 0: EINIT was successful.
* - <0: on error.
*/
int sgx_virt_einit(void __user *sigstruct, void __user *token,
void __user *secs, u64 *lepubkeyhash, int *trapnr)
{
int ret;
if (!cpu_feature_enabled(X86_FEATURE_SGX_LC)) {
ret = __sgx_virt_einit(sigstruct, token, secs);
} else {
preempt_disable();
sgx_update_lepubkeyhash(lepubkeyhash);
ret = __sgx_virt_einit(sigstruct, token, secs);
preempt_enable();
}
/* Propagate up the error from the WARN_ON_ONCE in __sgx_virt_einit() */
if (ret == -EINVAL)
return ret;
if (encls_faulted(ret)) {
*trapnr = ENCLS_TRAPNR(ret);
return -EFAULT;
}
return ret;
}
EXPORT_SYMBOL_GPL(sgx_virt_einit);