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From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org,
	linux-sgx@vger.kernel.org, akpm@linux-foundation.org,
	dave.hansen@intel.com, nhorman@redhat.com, npmccallum@redhat.com,
	serge.ayoun@intel.com, shay.katz-zamir@intel.com,
	haitao.huang@intel.com, andriy.shevchenko@linux.intel.com,
	tglx@linutronix.de, kai.svahn@intel.com, bp@alien8.de,
	josh@joshtriplett.org, luto@kernel.org, kai.huang@intel.com,
	rientjes@google.com, cedric.xing@intel.com,
	Suresh Siddha <suresh.b.siddha@intel.com>
Subject: Re: [PATCH v21 16/28] x86/sgx: Add the Linux SGX Enclave Driver
Date: Mon, 5 Aug 2019 09:16:44 -0700
Message-ID: <20190805161644.GD29275@linux.intel.com> (raw)
In-Reply-To: <20190713170804.2340-17-jarkko.sakkinen@linux.intel.com>

On Sat, Jul 13, 2019 at 08:07:52PM +0300, Jarkko Sakkinen wrote:
> +static unsigned long sgx_get_unmapped_area(struct file *file,
> +					   unsigned long addr,
> +					   unsigned long len,
> +					   unsigned long pgoff,
> +					   unsigned long flags)
> +{
> +	if (flags & MAP_PRIVATE)
> +		return -EINVAL;
> +
> +	if (flags & MAP_FIXED)
> +		return addr;
> +
> +	if (len < 2 * PAGE_SIZE || len & (len - 1))
> +		return -EINVAL;
> +
> +	addr = current->mm->get_unmapped_area(file, addr, 2 * len, pgoff,
> +					      flags);
> +	if (IS_ERR_VALUE(addr))
> +		return addr;
> +
> +	addr = (addr + (len - 1)) & ~(len - 1);
> +
> +	return addr;
> +}

Thinking about this more, I don't think the driver should verify or adjust
@addr and @len during non-fixed mmap().  There is no requirement that
userspace must map the full ELRANGE, or that an enclave's ELRANGE can
*never* be mapped to non-EPC.  The architectural requirement is that an
access that hits ELRANGE must map to the EPC *if* the CPU is executing the
associated enclave.

This means that a process can have random mappings that overlap an
enclave's ELRANGE while the enclave is active, it just can't access that
memory from within the enclave.

A good example is a large enclave, e.g. 3gb of actual code/data, that
userspace wants to locate below 4gb for some reason, e.g. running an
unmodified non-enclave binary under graphene.  Requiring @addr+@len to be
naturally sized and aligned will force @addr to 0x0, which is often
disallowed by the kernel.

  parent reply index

Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-13 17:07 [PATCH v21 00/28] Intel SGX foundations Jarkko Sakkinen
2019-07-13 17:07 ` [PATCH v21 01/28] x86/cpufeatures: Add Intel-defined SGX feature bit Jarkko Sakkinen
2019-07-13 17:07 ` [PATCH v21 02/28] x86/cpufeatures: Add SGX sub-features (as Linux-defined bits) Jarkko Sakkinen
2019-07-13 17:07 ` [PATCH v21 03/28] x86/msr: Add IA32_FEATURE_CONTROL.SGX_ENABLE definition Jarkko Sakkinen
2019-07-13 17:07 ` [PATCH v21 04/28] x86/cpufeatures: Add Intel-defined SGX_LC feature bit Jarkko Sakkinen
2019-07-13 17:07 ` [PATCH v21 05/28] x86/msr: Add SGX Launch Control MSR definitions Jarkko Sakkinen
2019-07-13 17:07 ` [PATCH v21 06/28] x86/mm: x86/sgx: Add new 'PF_SGX' page fault error code bit Jarkko Sakkinen
2019-07-13 17:07 ` [PATCH v21 07/28] x86/mm: x86/sgx: Signal SIGSEGV for userspace #PFs w/ PF_SGX Jarkko Sakkinen
2019-07-13 17:07 ` [PATCH v21 08/28] x86/cpu/intel: Detect SGX support and update caps appropriately Jarkko Sakkinen
2019-07-24 19:35   ` Sean Christopherson
2019-08-02 20:48     ` Jarkko Sakkinen
2019-08-07 15:17     ` Jarkko Sakkinen
2019-07-13 17:07 ` [PATCH v21 09/28] x86/sgx: Add ENCLS architectural error codes Jarkko Sakkinen
2019-07-13 17:07 ` [PATCH v21 10/28] x86/sgx: Add SGX1 and SGX2 architectural data structures Jarkko Sakkinen
2019-07-13 17:07 ` [PATCH v21 11/28] x86/sgx: Add wrappers for ENCLS leaf functions Jarkko Sakkinen
2019-07-13 17:07 ` [PATCH v21 12/28] x86/sgx: Enumerate and track EPC sections Jarkko Sakkinen
2019-07-13 17:07 ` [PATCH v21 13/28] x86/sgx: Add functions to allocate and free EPC pages Jarkko Sakkinen
2019-07-13 17:07 ` [PATCH v21 14/28] x86/sgx: Add sgx_einit() for initializing enclaves Jarkko Sakkinen
2019-07-13 17:07 ` [PATCH v21 15/28] mm: Introduce vm_ops->may_mprotect() Jarkko Sakkinen
2019-07-13 17:07 ` [PATCH v21 16/28] x86/sgx: Add the Linux SGX Enclave Driver Jarkko Sakkinen
2019-07-29 11:17   ` Ayoun, Serge
2019-08-07 15:15     ` Jarkko Sakkinen
2019-08-07 15:17       ` Jarkko Sakkinen
2019-08-07 16:45         ` Jethro Beekman
2019-08-08 15:40       ` Sean Christopherson
2019-08-09 15:02         ` Jarkko Sakkinen
2019-08-09 15:24           ` Sean Christopherson
2019-08-05 16:16   ` Sean Christopherson [this message]
2019-08-05 21:39     ` Jarkko Sakkinen
2019-07-13 17:07 ` [PATCH v21 17/28] x86/sgx: Add provisioning Jarkko Sakkinen
2019-07-13 17:07 ` [PATCH v21 18/28] x86/sgx: Add swapping code to the core and SGX driver Jarkko Sakkinen
2019-08-07  6:33   ` Jethro Beekman
2019-08-07 19:12     ` Jarkko Sakkinen
2019-07-13 17:07 ` [PATCH v21 19/28] x86/sgx: ptrace() support for the " Jarkko Sakkinen
2019-07-13 17:07 ` [PATCH v21 20/28] x86/vdso: Add support for exception fixup in vDSO functions Jarkko Sakkinen
2019-07-13 17:07 ` [PATCH v21 21/28] x86/fault: Add helper function to sanitize error code Jarkko Sakkinen
2019-07-13 17:07 ` [PATCH v21 22/28] x86/traps: Attempt to fixup exceptions in vDSO before signaling Jarkko Sakkinen
2019-07-13 17:07 ` [PATCH v21 23/28] x86/vdso: Add __vdso_sgx_enter_enclave() to wrap SGX enclave transitions Jarkko Sakkinen
2019-07-17 22:07   ` Xing, Cedric
2019-07-13 17:08 ` [PATCH v21 24/28] selftests/x86: Add a selftest for SGX Jarkko Sakkinen
2019-07-17 22:37   ` Xing, Cedric
2019-08-02 20:46     ` Jarkko Sakkinen
2019-08-16 15:43     ` Jarkko Sakkinen
2019-08-16 15:51       ` Jarkko Sakkinen
2019-08-16 16:56     ` Jarkko Sakkinen
2019-07-13 17:08 ` [PATCH v21 25/28] x86/sgx: Update MAINTAINERS Jarkko Sakkinen
2019-07-13 17:08 ` [PATCH v21 26/28] docs: x86/sgx: Add Architecture documentation Jarkko Sakkinen
2019-07-13 17:08 ` [PATCH v21 27/28] docs: x86/sgx: Document kernel internals Jarkko Sakkinen
2019-07-13 17:08 ` [PATCH v21 28/28] docs: x86/sgx: Document the enclave API Jarkko Sakkinen
2019-07-14 14:36 ` [PATCH v21 00/28] Intel SGX foundations Jarkko Sakkinen
2019-08-07  6:40   ` Jethro Beekman

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