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From: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To: linux-kernel@vger.kernel.org, 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, 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, puiterwijk@redhat.com,
	Andy Lutomirski <luto@amacapital.net>,
	Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Subject: [PATCH v29 17/20] x86/traps: Attempt to fixup exceptions in vDSO before signaling
Date: Wed, 22 Apr 2020 00:53:13 +0300
Message-ID: <20200421215316.56503-18-jarkko.sakkinen@linux.intel.com> (raw)
In-Reply-To: <20200421215316.56503-1-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>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
---
 arch/x86/kernel/traps.c | 14 ++++++++++++++
 arch/x86/mm/fault.c     |  8 ++++++++
 2 files changed, 22 insertions(+)

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 6ef00eb6fbb9..a814b1aea94d 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -56,6 +56,7 @@
 #include <asm/umip.h>
 #include <asm/insn.h>
 #include <asm/insn-eval.h>
+#include <asm/vdso.h>
 
 #ifdef CONFIG_X86_64
 #include <asm/x86_init.h>
@@ -205,6 +206,9 @@ 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;
 	}
 
 	/*
@@ -518,6 +522,9 @@ dotraplinkage void do_general_protection(struct pt_regs *regs, long error_code)
 		tsk->thread.error_code = error_code;
 		tsk->thread.trap_nr = X86_TRAP_GP;
 
+		if (fixup_vdso_exception(regs, X86_TRAP_GP, error_code, 0))
+			return;
+
 		show_signal(tsk, SIGSEGV, "", desc, regs, error_code);
 		force_sig(SIGSEGV);
 
@@ -762,6 +769,10 @@ 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.
@@ -842,6 +853,9 @@ 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));
 }
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 6b662d272af6..42965b47b52f 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -30,6 +30,7 @@
 #include <asm/desc.h>			/* store_idt(), ...		*/
 #include <asm/cpu_entry_area.h>		/* exception stack		*/
 #include <asm/pgtable_areas.h>		/* VMALLOC_START, ...		*/
+#include <asm/vdso.h>			/* fixup_vdso_exception()	*/
 
 #define CREATE_TRACE_POINTS
 #include <asm/trace/exceptions.h>
@@ -902,6 +903,10 @@ __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
 
 		sanitize_error_code(address, &error_code);
 
+		if (fixup_vdso_exception(regs, X86_TRAP_PF, error_code,
+		    address))
+			return;
+
 		if (likely(show_unhandled_signals))
 			show_signal_msg(regs, error_code, address, tsk);
 
@@ -1019,6 +1024,9 @@ do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
 
 	sanitize_error_code(address, &error_code);
 
+	if (fixup_vdso_exception(regs, X86_TRAP_PF, error_code, address))
+		return;
+
 	set_signal_archinfo(address, error_code);
 
 #ifdef CONFIG_MEMORY_FAILURE
-- 
2.25.1


  parent reply index

Thread overview: 83+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-21 21:52 [PATCH v29 00/20] Intel SGX foundations Jarkko Sakkinen
2020-04-21 21:52 ` [PATCH v29 01/20] x86/sgx: Update MAINTAINERS Jarkko Sakkinen
2020-04-21 21:52 ` [PATCH v29 02/20] x86/cpufeatures: x86/msr: Add Intel SGX hardware bits Jarkko Sakkinen
2020-04-21 21:52 ` [PATCH v29 03/20] x86/cpufeatures: x86/msr: Intel SGX Launch Control " Jarkko Sakkinen
2020-04-21 21:53 ` [PATCH v29 04/20] x86/mm: x86/sgx: Signal SIGSEGV with PF_SGX Jarkko Sakkinen
2020-04-21 21:53 ` [PATCH v29 05/20] x86/sgx: Add SGX microarchitectural data structures Jarkko Sakkinen
2020-04-21 21:53 ` [PATCH v29 06/20] x86/sgx: Add wrappers for ENCLS leaf functions Jarkko Sakkinen
2020-04-21 21:53 ` [PATCH v29 07/20] x86/cpu/intel: Detect SGX support Jarkko Sakkinen
2020-04-21 21:53 ` [PATCH v29 08/20] x86/sgx: Enumerate and track EPC sections Jarkko Sakkinen
2020-04-21 21:53 ` [PATCH v29 09/20] x86/sgx: Add functions to allocate and free EPC pages Jarkko Sakkinen
2020-04-21 21:53 ` [PATCH v29 10/20] mm: Introduce vm_ops->may_mprotect() Jarkko Sakkinen
2020-04-21 21:53 ` [PATCH v29 11/20] x86/sgx: Linux Enclave Driver Jarkko Sakkinen
2020-05-08 19:09   ` Sean Christopherson
2020-04-21 21:53 ` [PATCH v29 12/20] x86/sgx: Add provisioning Jarkko Sakkinen
2020-04-21 21:53 ` [PATCH v29 13/20] x86/sgx: Add a page reclaimer Jarkko Sakkinen
2020-04-21 21:53 ` [PATCH v29 14/20] x86/sgx: ptrace() support for the SGX driver Jarkko Sakkinen
2020-05-06 21:50   ` Sean Christopherson
2020-05-13 21:40     ` Jarkko Sakkinen
2020-04-21 21:53 ` [PATCH v29 15/20] x86/vdso: Add support for exception fixup in vDSO functions Jarkko Sakkinen
2020-04-21 21:53 ` [PATCH v29 16/20] x86/fault: Add helper function to sanitize error code Jarkko Sakkinen
2020-04-21 21:53 ` Jarkko Sakkinen [this message]
2020-04-21 21:53 ` [PATCH v29 18/20] x86/vdso: Implement a vDSO for Intel SGX enclave call Jarkko Sakkinen
2020-04-21 21:53 ` [PATCH v29 19/20] selftests/x86: Add a selftest for SGX Jarkko Sakkinen
2020-04-21 21:53 ` [PATCH v29 20/20] docs: x86/sgx: Document SGX micro architecture and kernel internals Jarkko Sakkinen
2020-04-22 16:48 ` [PATCH v29 00/20] Intel SGX foundations Connor Kuehl
2020-04-29  5:22   ` Jarkko Sakkinen
2020-04-26 16:57 ` Dr. Greg
2020-04-29  5:23   ` Jarkko Sakkinen
2020-04-29 15:14     ` Sean Christopherson
2020-04-30  3:59       ` Jarkko Sakkinen
2020-05-02 23:05         ` Dr. Greg
2020-05-03  0:48           ` Andy Lutomirski
2020-05-04  9:34             ` Dr. Greg
2020-04-29 15:30   ` Sean Christopherson
2020-05-08  0:40     ` Andy Lutomirski
2020-05-07  0:41   ` Thomas Gleixner
2020-05-08 19:02     ` Dr. Greg
2020-05-08 19:56       ` Sean Christopherson
2020-05-14  9:16         ` Dr. Greg
2020-05-14 16:15           ` Sean Christopherson
2020-05-14 16:20             ` Borislav Petkov
2020-05-14 19:29               ` Thomas Gleixner
2020-05-15  9:28               ` Jarkko Sakkinen
2020-05-15  9:42                 ` Borislav Petkov
2020-05-15 16:24                   ` Jarkko Sakkinen
2020-05-15  0:09             ` Jarkko Sakkinen
2020-05-15 19:54           ` Nathaniel McCallum
2020-05-16  9:58             ` Jarkko Sakkinen
2020-05-24 21:27           ` Pavel Machek
2020-05-26  8:16             ` David Laight
2020-04-26 17:03 ` Dr. Greg
2020-04-29 15:27 ` Jethro Beekman
2020-04-30  3:46   ` Jarkko Sakkinen
2020-04-30  7:19     ` Jethro Beekman
2020-04-30  8:23       ` Jarkko Sakkinen
2020-04-30 14:12         ` Jethro Beekman
2020-05-06 12:16           ` Jarkko Sakkinen
2020-05-06 16:39 ` Jordan Hand
2020-05-07 18:06   ` Dr. Greg
2020-05-08 16:16     ` Jordan Hand
2020-05-13 23:09   ` Jarkko Sakkinen
2020-05-06 21:42 ` Nathaniel McCallum
2020-05-06 22:14   ` Sean Christopherson
2020-05-07  5:02     ` Haitao Huang
2020-05-07 16:49       ` Nathaniel McCallum
2020-05-07 19:34         ` Sean Christopherson
2020-05-07 22:35           ` Haitao Huang
2020-05-08  0:25             ` Sean Christopherson
2020-05-28 11:15               ` Jarkko Sakkinen
2020-05-28 11:19                 ` Jarkko Sakkinen
2020-05-07 22:31         ` Haitao Huang
2020-05-13 22:14   ` Jarkko Sakkinen
2020-05-13 22:18     ` Jarkko Sakkinen
2020-05-14  6:31     ` Jethro Beekman
2020-05-14 19:30     ` Thomas Gleixner
2020-05-15  0:22       ` Jarkko Sakkinen
2020-05-08 19:08 ` Sean Christopherson
2020-05-14 19:05   ` Seth Moore
2020-05-15  0:23     ` Jarkko Sakkinen
2020-05-12 11:55 ` Hui, Chunyang
2020-05-12 16:51   ` Dr. Greg
2020-05-14 10:49   ` Jarkko Sakkinen
2020-05-16  8:53 ` [PATCH] x86/cpu/intel: Add nosgx kernel parameter Jarkko Sakkinen

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