From: ebiederm@xmission.com (Eric W. Biederman)
To: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: x86@kernel.org, platform-driver-x86@vger.kernel.org,
dave.hansen@intel.com, sean.j.christopherson@intel.com,
nhorman@redhat.com, npmccallum@redhat.com, serge.ayoun@intel.com,
shay.katz-zamir@intel.com, linux-sgx@vger.kernel.org,
andriy.shevchenko@linux.intel.com,
Dave Hansen <dave.hansen@linux.intel.com>,
Arnd Bergmann <arnd@arndb.de>,
linux-arch@vger.kernel.org (open list:GENERIC INCLUDE/ASM HEADER
FILES), linux-kernel@vger.kernel.org (open list)
Subject: Re: [PATCH v14 08/19] signal: x86/sgx: Add SIGSEGV siginfo code for SGX EPCM fault
Date: Thu, 27 Sep 2018 20:41:48 +0200 [thread overview]
Message-ID: <87in2qpytv.fsf@xmission.com> (raw)
In-Reply-To: <20180925130845.9962-9-jarkko.sakkinen@linux.intel.com> (Jarkko Sakkinen's message of "Tue, 25 Sep 2018 16:06:45 +0300")
Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> writes:
> From: Sean Christopherson <sean.j.christopherson@intel.com>
>
> The SGX Enclave Page Cache Map (EPCM) is a hardware-managed table
> that enforces accesses to an enclave's EPC page in addition to the
> software-managed kernel page tables, i.e. the effective permissions
> for an EPC page are a logical AND of the kernel's page tables and
> the corresponding EPCM entry. The primary purpose of the EPCM is
> to prevent a malcious or compromised kernel from attacking an enclave
> by modifying the enclave's page tables. The EPCM entires for an
> enclave are populated when the enclave is built and verified, using
> metadata provided by the enclave that is included in the measurement
> used to verify the enclave.
>
> In normal operation of a properly functioning, non-malicious kernel
> (and enclave), the EPCM permissions will never trigger a fault, i.e.
> the kernel may make the permissions for an EPC page more restrictive,
> e.g. mark it not-present to swap out the EPC page, but the kernel will
> never make its permissions less restrictive.
>
> But, there is a legitimate scenario in which the kernel's page tables
> can become less restrictive than the EPCM: on current hardware all
> enclaves are destroyed (by hardware) on a transition to S3 or lower
> sleep states, i.e. all EPCM entries are invalid (not-present) after
> the system resumes from its sleep state.
>
> Unfortunately, on CPUs that support only SGX1, EPCM violations result
> in a #GP. The upside of the #GP is that no kernel changes are needed
> to deal with the EPCM being blasted away by hardware, e.g. userspace
> gets a SIGSEGV, assumes the EPCM was lost and restarts its enclave
> and everyone is happy. The downside is that userspace has to assume
> the SIGSEGV was because the EPC was lost (or possibly do some leg work
> to rule out other causes).
>
> In SGX2, the oddity of delivering a #GP due to what are inherently
> paging related violations is remedied. CPUs that support SGX2 deliver
> EPCM violations as #PFs with a new SGX error code bit set. So, now
> that hardware provides us with a way to unequivocally determine that
> a fault was due to a EPCM violation, define a signfo code for SIGSEGV
> so that the information can be passed onto userspace.
>
> Cc: Dave Hansen <dave.hansen@linux.intel.com>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
> ---
> include/uapi/asm-generic/siginfo.h | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/include/uapi/asm-generic/siginfo.h b/include/uapi/asm-generic/siginfo.h
> index 80e2a7227205..fdd898e2325b 100644
> --- a/include/uapi/asm-generic/siginfo.h
> +++ b/include/uapi/asm-generic/siginfo.h
> @@ -225,7 +225,11 @@ typedef struct siginfo {
> #else
> # define SEGV_PKUERR 4 /* failed protection key checks */
> #endif
> +#ifdef __x86_64__
> +#define SEGV_SGXERR 5 /* SGX Enclave Page Cache Map fault */
> +#else
> #define SEGV_ACCADI 5 /* ADI not enabled for mapped object */
> +#endif
Don't do this crazy ifdef thing. si_codes are not supposed to be per
architecture. There are a few historical bugs but with a 32bit space
it is just stupid to add #ifdefs.
Just set.
#define SEGV_SGXERR 8 and increase NSIGSEGV
Anything else is just asking for trouble. Especially when you want to
get SGX working on itaninum.
> #define SEGV_ADIDERR 6 /* Disrupting MCD error */
> #define SEGV_ADIPERR 7 /* Precise MCD exception */
> #define NSIGSEGV 7
Eric
next prev parent reply other threads:[~2018-09-27 18:42 UTC|newest]
Thread overview: 71+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-25 13:06 [PATCH v14 00/19] Intel SGX1 support Jarkko Sakkinen
2018-09-25 13:06 ` [PATCH v14 01/19] x86/sgx: Update MAINTAINERS Jarkko Sakkinen
2018-09-25 13:06 ` [PATCH v14 02/19] x86/sgx: Architectural structures Jarkko Sakkinen
2018-09-25 13:06 ` [PATCH v14 03/19] x86/cpufeature: Add SGX and SGX_LC CPU features Jarkko Sakkinen
2018-09-25 13:06 ` [PATCH v14 04/19] x86/cpufeatures: Add SGX feature bits Jarkko Sakkinen
2018-09-25 16:48 ` Borislav Petkov
2018-09-26 11:11 ` Jarkko Sakkinen
2018-09-26 11:36 ` Borislav Petkov
2018-09-27 13:16 ` Jarkko Sakkinen
2018-09-27 13:51 ` Borislav Petkov
2018-09-27 14:52 ` Jarkko Sakkinen
2018-09-25 13:06 ` [PATCH v14 05/19] x86/msr: Add SGX definitions to msr-index.h Jarkko Sakkinen
2018-09-25 13:06 ` [PATCH v14 06/19] x86/mm: x86/sgx: Add new 'PF_SGX' page fault error code bit Jarkko Sakkinen
2018-09-25 13:06 ` [PATCH v14 07/19] x86/fault: x86/mm/pkeys: relocate stale comment regarding OSPKE Jarkko Sakkinen
2018-09-25 13:06 ` [PATCH v14 08/19] signal: x86/sgx: Add SIGSEGV siginfo code for SGX EPCM fault Jarkko Sakkinen
2018-09-26 19:14 ` Sean Christopherson
2018-09-27 18:41 ` Eric W. Biederman [this message]
2018-09-25 13:06 ` [PATCH v14 09/19] x86/mm: x86/sgx: Signal SEGV_SGXERR for #PFs w/ PF_SGX Jarkko Sakkinen
2018-09-25 22:53 ` Andy Lutomirski
2018-09-26 17:35 ` Sean Christopherson
2018-09-26 18:12 ` Andy Lutomirski
2018-09-26 20:16 ` Dave Hansen
2018-09-26 20:44 ` Sean Christopherson
2018-09-26 20:49 ` Dave Hansen
2018-09-26 21:15 ` Andy Lutomirski
2018-09-26 21:45 ` Dave Hansen
2018-09-26 22:37 ` Andy Lutomirski
2018-09-27 14:21 ` Jarkko Sakkinen
2018-09-27 14:41 ` Andy Lutomirski
2018-09-27 13:56 ` Jarkko Sakkinen
2018-10-01 21:42 ` Jethro Beekman
2018-10-01 22:03 ` Dave Hansen
2018-10-31 21:30 ` Sean Christopherson
2018-10-31 21:35 ` Dave Hansen
2018-11-01 17:42 ` Jarkko Sakkinen
2018-11-01 17:44 ` Jarkko Sakkinen
2018-10-02 0:31 ` Jarkko Sakkinen
2018-10-01 14:29 ` Sean Christopherson
2018-10-01 14:41 ` Dave Hansen
2018-10-02 0:07 ` Jarkko Sakkinen
2018-09-27 13:42 ` Jarkko Sakkinen
2018-09-27 14:58 ` Dave Hansen
2018-09-27 15:39 ` Jarkko Sakkinen
2018-09-27 15:53 ` Dave Hansen
2018-09-27 13:14 ` Jarkko Sakkinen
2018-09-27 19:43 ` Eric W. Biederman
2018-09-28 12:17 ` Jarkko Sakkinen
2018-09-25 13:06 ` [PATCH v14 10/19] x86/sgx: Detect Intel SGX Jarkko Sakkinen
2018-09-25 20:02 ` Randy Dunlap
2018-09-27 13:13 ` Jarkko Sakkinen
2018-09-25 13:06 ` [PATCH v14 11/19] x86/sgx: Add wrappers for ENCLS leaf functions Jarkko Sakkinen
2018-09-25 20:01 ` Randy Dunlap
2018-09-27 13:12 ` Jarkko Sakkinen
2018-09-25 13:06 ` [PATCH v14 12/19] x86/sgx: Add data structures for tracking the EPC pages Jarkko Sakkinen
2018-09-25 20:00 ` Randy Dunlap
2018-09-27 13:11 ` Jarkko Sakkinen
2018-09-25 13:06 ` [PATCH v14 13/19] x86/sgx: Enclave Page Cache (EPC) memory manager Jarkko Sakkinen
2018-09-25 13:06 ` [PATCH v14 14/19] x86/sgx: Add sgx_einit() for initializing enclaves Jarkko Sakkinen
2018-09-25 13:06 ` [PATCH v14 15/19] platform/x86: Intel SGX driver Jarkko Sakkinen
2018-10-04 18:01 ` Sean Christopherson
2018-10-05 11:32 ` Jarkko Sakkinen
2018-09-25 13:06 ` [PATCH v14 16/19] platform/x86: Add swapping functionality to the " Jarkko Sakkinen
2018-09-25 13:06 ` [PATCH v14 17/19] x86/sgx: Add a simple swapper for the EPC memory manager Jarkko Sakkinen
2018-09-25 13:06 ` [PATCH v14 18/19] platform/x86: ptrace() support for the SGX driver Jarkko Sakkinen
2018-09-25 13:06 ` [PATCH v14 19/19] x86/sgx: Driver documentation Jarkko Sakkinen
2018-09-25 13:27 ` Jonathan Corbet
2018-10-15 20:54 ` Pavel Machek
2018-10-17 23:45 ` Jarkko Sakkinen
2018-10-18 9:57 ` Pavel Machek
2018-10-19 23:59 ` Jarkko Sakkinen
2018-10-17 23:56 ` Dave Hansen
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