Re: [PATCH v36 12/24] x86/sgx: Add SGX_IOC_ENCLAVE_CREATE

From: Darren Kenny
Date: Thu Aug 06 2020 - 16:25:00 EST

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On Thursday, 2020-07-16 at 16:52:51 +03, Jarkko Sakkinen wrote:
> Add an ioctl that performs ENCLS[ECREATE], which creates SGX Enclave
> Control Structure for the enclave. SECS contains attributes about the
> enclave that are used by the hardware and cannot be directly accessed by
> software, as SECS resides in the EPC.
>
> One essential field in SECS is a field that stores the SHA256 of the
> measured enclave pages. This field, MRENCLAVE, is initialized by the
> ECREATE instruction and updated by every EADD and EEXTEND operation.
> Finally, EINIT locks down the value.
>
> Acked-by: Jethro Beekman <jethro@xxxxxxxxxxxx>
> Tested-by: Jethro Beekman <jethro@xxxxxxxxxxxx>
> Tested-by: Haitao Huang <haitao.huang@xxxxxxxxxxxxxxx>
> Tested-by: Chunyang Hui <sanqian.hcy@xxxxxxxxxx>
> Tested-by: Jordan Hand <jorhand@xxxxxxxxxxxxxxxxxxx>
> Tested-by: Nathaniel McCallum <npmccallum@xxxxxxxxxx>
> Tested-by: Seth Moore <sethmo@xxxxxxxxxx>

Tested-by: Darren Kenny <darren.kenny@xxxxxxxxxx>
Reviewed-by: Darren Kenny <darren.kenny@xxxxxxxxxx>

> Co-developed-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> Co-developed-by: Suresh Siddha <suresh.b.siddha@xxxxxxxxx>
> Signed-off-by: Suresh Siddha <suresh.b.siddha@xxxxxxxxx>
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
> ---
> .../userspace-api/ioctl/ioctl-number.rst | 1 +
> arch/x86/include/uapi/asm/sgx.h | 25 ++
> arch/x86/kernel/cpu/sgx/Makefile | 1 +
> arch/x86/kernel/cpu/sgx/driver.c | 12 +
> arch/x86/kernel/cpu/sgx/driver.h | 1 +
> arch/x86/kernel/cpu/sgx/ioctl.c | 226 ++++++++++++++++++
> 6 files changed, 266 insertions(+)
> create mode 100644 arch/x86/include/uapi/asm/sgx.h
> create mode 100644 arch/x86/kernel/cpu/sgx/ioctl.c
>
> diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documentation/userspace-api/ioctl/ioctl-number.rst
> index 59472cd6a11d..35f713e3a267 100644
> --- a/Documentation/userspace-api/ioctl/ioctl-number.rst
> +++ b/Documentation/userspace-api/ioctl/ioctl-number.rst
> @@ -323,6 +323,7 @@ Code Seq# Include File Comments
> <mailto:tlewis@xxxxxxxxxxxxxx>
> 0xA3 90-9F linux/dtlk.h
> 0xA4 00-1F uapi/linux/tee.h Generic TEE subsystem
> +0xA4 00-1F uapi/asm/sgx.h Intel SGX subsystem (a legit conflict as TEE and SGX do not co-exist)
> 0xAA 00-3F linux/uapi/linux/userfaultfd.h
> 0xAB 00-1F linux/nbd.h
> 0xAC 00-1F linux/raw.h
> diff --git a/arch/x86/include/uapi/asm/sgx.h b/arch/x86/include/uapi/asm/sgx.h
> new file mode 100644
> index 000000000000..3787d278e84b
> --- /dev/null
> +++ b/arch/x86/include/uapi/asm/sgx.h
> @@ -0,0 +1,25 @@
> +/* SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause) WITH Linux-syscall-note */
> +/*
> + * Copyright(c) 2016-19 Intel Corporation.
> + */
> +#ifndef _UAPI_ASM_X86_SGX_H
> +#define _UAPI_ASM_X86_SGX_H
> +
> +#include <linux/types.h>
> +#include <linux/ioctl.h>
> +
> +#define SGX_MAGIC 0xA4
> +
> +#define SGX_IOC_ENCLAVE_CREATE \
> + _IOW(SGX_MAGIC, 0x00, struct sgx_enclave_create)
> +
> +/**
> + * struct sgx_enclave_create - parameter structure for the
> + * %SGX_IOC_ENCLAVE_CREATE ioctl
> + * @src: address for the SECS page data
> + */
> +struct sgx_enclave_create {
> + __u64 src;
> +};
> +
> +#endif /* _UAPI_ASM_X86_SGX_H */
> diff --git a/arch/x86/kernel/cpu/sgx/Makefile b/arch/x86/kernel/cpu/sgx/Makefile
> index 3fc451120735..91d3dc784a29 100644
> --- a/arch/x86/kernel/cpu/sgx/Makefile
> +++ b/arch/x86/kernel/cpu/sgx/Makefile
> @@ -1,4 +1,5 @@
> obj-y += \
> driver.o \
> encl.o \
> + ioctl.o \
> main.o
> diff --git a/arch/x86/kernel/cpu/sgx/driver.c b/arch/x86/kernel/cpu/sgx/driver.c
> index b52520407f5b..5559bc18de41 100644
> --- a/arch/x86/kernel/cpu/sgx/driver.c
> +++ b/arch/x86/kernel/cpu/sgx/driver.c
> @@ -118,10 +118,22 @@ static unsigned long sgx_get_unmapped_area(struct file *file,
> return current->mm->get_unmapped_area(file, addr, len, pgoff, flags);
> }
>
> +#ifdef CONFIG_COMPAT
> +static long sgx_compat_ioctl(struct file *filep, unsigned int cmd,
> + unsigned long arg)
> +{
> + return sgx_ioctl(filep, cmd, arg);
> +}
> +#endif
> +
> static const struct file_operations sgx_encl_fops = {
> .owner = THIS_MODULE,
> .open = sgx_open,
> .release = sgx_release,
> + .unlocked_ioctl = sgx_ioctl,
> +#ifdef CONFIG_COMPAT
> + .compat_ioctl = sgx_compat_ioctl,
> +#endif
> .mmap = sgx_mmap,
> .get_unmapped_area = sgx_get_unmapped_area,
> };
> diff --git a/arch/x86/kernel/cpu/sgx/driver.h b/arch/x86/kernel/cpu/sgx/driver.h
> index f7ce40dedc91..e4063923115b 100644
> --- a/arch/x86/kernel/cpu/sgx/driver.h
> +++ b/arch/x86/kernel/cpu/sgx/driver.h
> @@ -9,6 +9,7 @@
> #include <linux/rwsem.h>
> #include <linux/sched.h>
> #include <linux/workqueue.h>
> +#include <uapi/asm/sgx.h>
> #include "sgx.h"
>
> #define SGX_EINIT_SPIN_COUNT 20
> diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c
> new file mode 100644
> index 000000000000..7981c411b05a
> --- /dev/null
> +++ b/arch/x86/kernel/cpu/sgx/ioctl.c
> @@ -0,0 +1,226 @@
> +// SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause)
> +// Copyright(c) 2016-19 Intel Corporation.
> +
> +#include <asm/mman.h>
> +#include <linux/mman.h>
> +#include <linux/delay.h>
> +#include <linux/file.h>
> +#include <linux/hashtable.h>
> +#include <linux/highmem.h>
> +#include <linux/ratelimit.h>
> +#include <linux/sched/signal.h>
> +#include <linux/shmem_fs.h>
> +#include <linux/slab.h>
> +#include <linux/suspend.h>
> +#include "driver.h"
> +#include "encl.h"
> +#include "encls.h"
> +
> +static u32 sgx_calc_ssa_frame_size(u32 miscselect, u64 xfrm)
> +{
> + u32 size_max = PAGE_SIZE;
> + u32 size;
> + int i;
> +
> + for (i = 2; i < 64; i++) {
> + if (!((1 << i) & xfrm))
> + continue;
> +
> + size = SGX_SSA_GPRS_SIZE + sgx_xsave_size_tbl[i];
> +
> + if (miscselect & SGX_MISC_EXINFO)
> + size += SGX_SSA_MISC_EXINFO_SIZE;
> +
> + if (size > size_max)
> + size_max = size;
> + }
> +
> + return PFN_UP(size_max);
> +}
> +
> +static int sgx_validate_secs(const struct sgx_secs *secs)
> +{
> + u64 max_size = (secs->attributes & SGX_ATTR_MODE64BIT) ?
> + sgx_encl_size_max_64 : sgx_encl_size_max_32;
> +
> + if (secs->size < (2 * PAGE_SIZE) || !is_power_of_2(secs->size))
> + return -EINVAL;
> +
> + if (secs->base & (secs->size - 1))
> + return -EINVAL;
> +
> + if (secs->miscselect & sgx_misc_reserved_mask ||
> + secs->attributes & sgx_attributes_reserved_mask ||
> + secs->xfrm & sgx_xfrm_reserved_mask)
> + return -EINVAL;
> +
> + if (secs->size >= max_size)
> + return -EINVAL;
> +
> + if (!(secs->xfrm & XFEATURE_MASK_FP) ||
> + !(secs->xfrm & XFEATURE_MASK_SSE) ||
> + (((secs->xfrm >> XFEATURE_BNDREGS) & 1) !=
> + ((secs->xfrm >> XFEATURE_BNDCSR) & 1)))
> + return -EINVAL;
> +
> + if (!secs->ssa_frame_size)
> + return -EINVAL;
> +
> + if (sgx_calc_ssa_frame_size(secs->miscselect, secs->xfrm) >
> + secs->ssa_frame_size)
> + return -EINVAL;
> +
> + if (memchr_inv(secs->reserved1, 0, sizeof(secs->reserved1)) ||
> + memchr_inv(secs->reserved2, 0, sizeof(secs->reserved2)) ||
> + memchr_inv(secs->reserved3, 0, sizeof(secs->reserved3)) ||
> + memchr_inv(secs->reserved4, 0, sizeof(secs->reserved4)))
> + return -EINVAL;
> +
> + return 0;
> +}
> +
> +static int sgx_encl_create(struct sgx_encl *encl, struct sgx_secs *secs)
> +{
> + unsigned long encl_size = secs->size + PAGE_SIZE;
> + struct sgx_epc_page *secs_epc;
> + struct sgx_pageinfo pginfo;
> + struct sgx_secinfo secinfo;
> + struct file *backing;
> + long ret;
> +
> + if (sgx_validate_secs(secs)) {
> + pr_debug("invalid SECS\n");
> + return -EINVAL;
> + }
> +
> + backing = shmem_file_setup("SGX backing", encl_size + (encl_size >> 5),
> + VM_NORESERVE);
> + if (IS_ERR(backing))
> + return PTR_ERR(backing);
> +
> + encl->backing = backing;
> +
> + secs_epc = __sgx_alloc_epc_page();
> + if (IS_ERR(secs_epc)) {
> + ret = PTR_ERR(secs_epc);
> + goto err_out_backing;
> + }
> +
> + encl->secs.epc_page = secs_epc;
> +
> + pginfo.addr = 0;
> + pginfo.contents = (unsigned long)secs;
> + pginfo.metadata = (unsigned long)&secinfo;
> + pginfo.secs = 0;
> + memset(&secinfo, 0, sizeof(secinfo));
> +
> + ret = __ecreate((void *)&pginfo, sgx_get_epc_addr(secs_epc));
> + if (ret) {
> + pr_debug("ECREATE returned %ld\n", ret);
> + goto err_out;
> + }
> +
> + if (secs->attributes & SGX_ATTR_DEBUG)
> + atomic_or(SGX_ENCL_DEBUG, &encl->flags);
> +
> + encl->secs.encl = encl;
> + encl->secs_attributes = secs->attributes;
> + encl->allowed_attributes |= SGX_ATTR_ALLOWED_MASK;
> + encl->base = secs->base;
> + encl->size = secs->size;
> + encl->ssaframesize = secs->ssa_frame_size;
> +
> + /*
> + * Set SGX_ENCL_CREATED only after the enclave is fully prepped. This
> + * allows setting and checking enclave creation without having to take
> + * encl->lock.
> + */
> + atomic_or(SGX_ENCL_CREATED, &encl->flags);
> +
> + return 0;
> +
> +err_out:
> + sgx_free_epc_page(encl->secs.epc_page);
> + encl->secs.epc_page = NULL;
> +
> +err_out_backing:
> + fput(encl->backing);
> + encl->backing = NULL;
> +
> + return ret;
> +}
> +
> +/**
> + * sgx_ioc_enclave_create - handler for %SGX_IOC_ENCLAVE_CREATE
> + * @filep: open file to /dev/sgx
> + * @arg: userspace pointer to a struct sgx_enclave_create instance
> + *
> + * Allocate kernel data structures for a new enclave and execute ECREATE after
> + * verifying the correctness of the provided SECS.
> + *
> + * Note, enforcement of restricted and disallowed attributes is deferred until
> + * sgx_ioc_enclave_init(), only the architectural correctness of the SECS is
> + * checked by sgx_ioc_enclave_create().
> + *
> + * Return:
> + * 0 on success,
> + * -errno otherwise
> + */
> +static long sgx_ioc_enclave_create(struct sgx_encl *encl, void __user *arg)
> +{
> + struct sgx_enclave_create ecreate;
> + struct page *secs_page;
> + struct sgx_secs *secs;
> + int ret;
> +
> + if (atomic_read(&encl->flags) & SGX_ENCL_CREATED)
> + return -EINVAL;
> +
> + if (copy_from_user(&ecreate, arg, sizeof(ecreate)))
> + return -EFAULT;
> +
> + secs_page = alloc_page(GFP_KERNEL);
> + if (!secs_page)
> + return -ENOMEM;
> +
> + secs = kmap(secs_page);
> + if (copy_from_user(secs, (void __user *)ecreate.src, sizeof(*secs))) {
> + ret = -EFAULT;
> + goto out;
> + }
> +
> + ret = sgx_encl_create(encl, secs);
> +
> +out:
> + kunmap(secs_page);
> + __free_page(secs_page);
> + return ret;
> +}
> +
> +long sgx_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
> +{
> + struct sgx_encl *encl = filep->private_data;
> + int ret, encl_flags;
> +
> + encl_flags = atomic_fetch_or(SGX_ENCL_IOCTL, &encl->flags);
> + if (encl_flags & SGX_ENCL_IOCTL)
> + return -EBUSY;
> +
> + if (encl_flags & SGX_ENCL_DEAD) {
> + ret = -EFAULT;
> + goto out;
> + }
> +
> + switch (cmd) {
> + case SGX_IOC_ENCLAVE_CREATE:
> + ret = sgx_ioc_enclave_create(encl, (void __user *)arg);
> + break;
> + default:
> + ret = -ENOIOCTLCMD;
> + break;
> + }
> +
> +out:
> + atomic_andnot(SGX_ENCL_IOCTL, &encl->flags);
> + return ret;
> +}
> --
> 2.25.1

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