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From: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To: x86@kernel.org, linux-sgx@vger.kernel.org
Cc: akpm@linux-foundation.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, 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,
	Andy Lutomirski <luto@amacapital.net>,
	Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
	Dave Hansen <dave.hansen@linux.intel.com>
Subject: [PATCH v19 23/27] x86/traps: Attempt to fixup exceptions in vDSO before signaling
Date: Sun, 17 Mar 2019 23:14:52 +0200
Message-ID: <20190317211456.13927-24-jarkko.sakkinen@linux.intel.com> (raw)
In-Reply-To: <20190317211456.13927-1-jarkko.sakkinen@linux.intel.com>

From: Sean Christopherson <sean.j.christopherson@intel.com>

vDSO functions can now leverage an exception fixup mechanism similar to
kernel exception fixup.  For vDSO exception fixup, the initial user is
Intel's Software Guard Extensions (SGX), which will wrap the low-level
transitions to/from the enclave, i.e. EENTER and ERESUME instructions,
in a vDSO function and leverage fixup to intercept exceptions that would
otherwise generate a signal.  This allows the vDSO wrapper to return the
fault information directly to its caller, obviating the need for SGX
applications and libraries to juggle signal handlers.

Attempt to fixup vDSO exceptions immediately prior to populating and
sending signal information.  Except for the delivery mechanism, an
exception in a vDSO function should be treated like any other exception
in userspace, e.g. any fault that is successfully handled by the kernel
should not be directly visible to userspace.

Although it's debatable whether or not all exceptions are of interest to
enclaves, defer to the vDSO fixup to decide whether to do fixup or
generate a signal.  Future users of vDSO fixup, if there ever are any,
will undoubtedly have different requirements than SGX enclaves, e.g. the
fixup vs. signal logic can be made function specific if/when necessary.

Suggested-by: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
 arch/x86/kernel/traps.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index d26f9e9c3d83..02eda456c119 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -61,6 +61,7 @@
 #include <asm/mpx.h>
 #include <asm/vm86.h>
 #include <asm/umip.h>
+#include <asm/vdso.h>
 
 #ifdef CONFIG_X86_64
 #include <asm/x86_init.h>
@@ -210,6 +211,9 @@ do_trap_no_signal(struct task_struct *tsk, int trapnr, const char *str,
 		tsk->thread.error_code = error_code;
 		tsk->thread.trap_nr = trapnr;
 		die(str, regs, error_code);
+	} else {
+		if (fixup_vdso_exception(regs, trapnr, error_code, 0))
+			return 0;
 	}
 
 	/*
@@ -561,6 +565,9 @@ do_general_protection(struct pt_regs *regs, long error_code)
 		return;
 	}
 
+	if (fixup_vdso_exception(regs, X86_TRAP_GP, error_code, 0))
+		return;
+
 	tsk->thread.error_code = error_code;
 	tsk->thread.trap_nr = X86_TRAP_GP;
 
@@ -775,6 +782,10 @@ dotraplinkage void do_debug(struct pt_regs *regs, long error_code)
 							SIGTRAP) == NOTIFY_STOP)
 		goto exit;
 
+	if (user_mode(regs) &&
+	    fixup_vdso_exception(regs, X86_TRAP_DB, error_code, 0))
+		goto exit;
+
 	/*
 	 * Let others (NMI) know that the debug stack is in use
 	 * as we may switch to the interrupt stack.
@@ -855,6 +866,9 @@ static void math_error(struct pt_regs *regs, int error_code, int trapnr)
 	if (!si_code)
 		return;
 
+	if (fixup_vdso_exception(regs, trapnr, error_code, 0))
+		return;
+
 	force_sig_fault(SIGFPE, si_code,
 			(void __user *)uprobe_get_trap_addr(regs), task);
 }
-- 
2.19.1


  parent reply index

Thread overview: 92+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-17 21:14 [PATCH v19 00/27] Intel SGX1 support Jarkko Sakkinen
2019-03-17 21:14 ` [PATCH v19 01/27] x86/cpufeatures: Add Intel-defined SGX feature bit Jarkko Sakkinen
2019-03-17 21:14 ` [PATCH v19 02/27] x86/cpufeatures: Add SGX sub-features (as Linux-defined bits) Jarkko Sakkinen
2019-03-17 21:14 ` [PATCH v19 03/27] x86/msr: Add IA32_FEATURE_CONTROL.SGX_ENABLE definition Jarkko Sakkinen
2019-03-17 21:14 ` [PATCH v19 04/27] x86/cpufeatures: Add Intel-defined SGX_LC feature bit Jarkko Sakkinen
2019-03-17 21:14 ` [PATCH v19 05/27] x86/msr: Add SGX Launch Control MSR definitions Jarkko Sakkinen
2019-03-17 21:14 ` [PATCH v19 06/27] x86/mm: x86/sgx: Add new 'PF_SGX' page fault error code bit Jarkko Sakkinen
2019-03-17 21:14 ` [PATCH v19 07/27] x86/mm: x86/sgx: Signal SIGSEGV for userspace #PFs w/ PF_SGX Jarkko Sakkinen
2019-03-18 17:15   ` Dave Hansen
2019-03-18 19:53     ` Sean Christopherson
2019-03-17 21:14 ` [PATCH v19 08/27] x86/cpu/intel: Detect SGX support and update caps appropriately Jarkko Sakkinen
2019-03-17 21:14 ` [PATCH v19 09/27] x86/sgx: Add ENCLS architectural error codes Jarkko Sakkinen
2019-03-17 21:14 ` [PATCH v19 10/27] x86/sgx: Add SGX1 and SGX2 architectural data structures Jarkko Sakkinen
2019-03-17 21:14 ` [PATCH v19 11/27] x86/sgx: Add definitions for SGX's CPUID leaf and variable sub-leafs Jarkko Sakkinen
2019-03-17 21:14 ` [PATCH v19 12/27] x86/sgx: Enumerate and track EPC sections Jarkko Sakkinen
2019-03-18 19:50   ` Sean Christopherson
2019-03-21 14:40     ` Jarkko Sakkinen
2019-03-21 15:28       ` Sean Christopherson
2019-03-22 10:19         ` Jarkko Sakkinen
2019-03-22 10:50           ` Jarkko Sakkinen
2019-03-17 21:14 ` [PATCH v19 13/27] x86/sgx: Add wrappers for ENCLS leaf functions Jarkko Sakkinen
2019-03-19 19:59   ` Sean Christopherson
2019-03-21 14:51     ` Jarkko Sakkinen
2019-03-21 15:40       ` Sean Christopherson
2019-03-22 11:00         ` Jarkko Sakkinen
2019-03-22 16:43           ` Sean Christopherson
2019-03-17 21:14 ` [PATCH v19 16/27] x86/sgx: Add the Linux SGX Enclave Driver Jarkko Sakkinen
2019-03-19 21:19   ` Sean Christopherson
2019-03-21 15:51     ` Jarkko Sakkinen
2019-03-21 16:47       ` Sean Christopherson
2019-03-22 11:10         ` Jarkko Sakkinen
2019-03-26 13:26       ` Jarkko Sakkinen
2019-03-26 23:58         ` Sean Christopherson
2019-03-27  5:28           ` Jarkko Sakkinen
2019-03-27 17:57             ` Sean Christopherson
2019-03-27 18:38             ` Jethro Beekman
2019-03-27 20:06               ` Sean Christopherson
2019-03-28  1:21                 ` Jethro Beekman
2019-03-28 13:19                 ` Jarkko Sakkinen
2019-03-28 19:05                   ` Andy Lutomirski
2019-03-29  9:43                     ` Jarkko Sakkinen
2019-03-29 16:20                     ` Sean Christopherson
2019-04-01 10:01                       ` Jarkko Sakkinen
2019-04-01 17:25                         ` Jethro Beekman
2019-04-01 22:57                           ` Jarkko Sakkinen
2019-03-28 13:15               ` Jarkko Sakkinen
2019-03-19 23:00   ` Sean Christopherson
2019-03-21 16:18     ` Jarkko Sakkinen
2019-03-21 17:38       ` Sean Christopherson
2019-03-22 11:17         ` Jarkko Sakkinen
2019-03-17 21:14 ` [PATCH v19 17/27] x86/sgx: Add provisioning Jarkko Sakkinen
2019-03-19 20:09   ` Sean Christopherson
2019-03-21  2:08     ` Huang, Kai
2019-03-21 14:32       ` Jarkko Sakkinen
2019-03-21 21:41         ` Huang, Kai
2019-03-22 11:31           ` Jarkko Sakkinen
2019-03-21 14:30     ` Jarkko Sakkinen
2019-03-21 14:38   ` Nathaniel McCallum
2019-03-22 11:22     ` Jarkko Sakkinen
2019-03-21 16:50   ` Andy Lutomirski
2019-03-22 11:29     ` Jarkko Sakkinen
2019-03-22 11:43       ` Jarkko Sakkinen
2019-03-22 18:20         ` Andy Lutomirski
2019-03-25 14:55           ` Jarkko Sakkinen
2019-03-27  0:14             ` Sean Christopherson
2019-04-05 10:18             ` Jarkko Sakkinen
2019-04-05 13:53               ` Andy Lutomirski
2019-04-05 14:20                 ` Jarkko Sakkinen
2019-04-05 14:34                   ` Greg KH
2019-04-09 13:37                     ` Jarkko Sakkinen
2019-04-05 14:21                 ` Greg KH
2019-03-17 21:14 ` [PATCH v19 19/27] x86/sgx: ptrace() support for the SGX driver Jarkko Sakkinen
2019-03-19 22:22   ` Sean Christopherson
2019-03-21 15:02     ` Jarkko Sakkinen
2019-03-17 21:14 ` [PATCH v19 20/27] x86/vdso: Add support for exception fixup in vDSO functions Jarkko Sakkinen
2019-03-17 21:14 ` [PATCH v19 21/27] x86/fault: Add helper function to sanitize error code Jarkko Sakkinen
2019-03-17 21:14 ` [PATCH v19 22/27] x86/fault: Attempt to fixup unhandled #PF in vDSO before signaling Jarkko Sakkinen
2019-03-17 21:14 ` Jarkko Sakkinen [this message]
2019-03-17 21:14 ` [PATCH v19 25/27] x86/sgx: SGX documentation Jarkko Sakkinen
2019-03-20 17:14   ` Sean Christopherson
2019-03-21 16:24     ` Jarkko Sakkinen
2019-03-17 21:14 ` [PATCH v19 26/27] selftests/x86: Add a selftest for SGX Jarkko Sakkinen
2019-03-17 21:14 ` [PATCH v19 27/27] x86/sgx: Update MAINTAINERS Jarkko Sakkinen
2019-03-19 17:12   ` Sean Christopherson
2019-03-21 14:42     ` Jarkko Sakkinen
     [not found] ` <20190317211456.13927-19-jarkko.sakkinen@linux.intel.com>
2019-03-19 22:09   ` [PATCH v19 18/27] x86/sgx: Add swapping code to the core and SGX driver Sean Christopherson
2019-03-21 14:59     ` Jarkko Sakkinen
2019-03-19 23:41 ` [PATCH v19 00/27] Intel SGX1 support Sean Christopherson
2019-03-19 23:52   ` Jethro Beekman
2019-03-20  0:22     ` Sean Christopherson
2019-03-21 16:20     ` Jarkko Sakkinen
2019-03-21 16:00   ` Jarkko Sakkinen

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